Method for manufacturing circuit board by laser-made conductive pattern after only electroplating thickening and weldability processing hole
阅读说明：本技术 一种只电镀加厚并可焊性处理孔后激光制导电图案的制造电路板方法 (Method for manufacturing circuit board by laser-made conductive pattern after only electroplating thickening and weldability processing hole ) 是由 胡宏宇 宋金月 于 2021-08-30 设计创作，主要内容包括：本发明涉及一种只电镀加厚并可焊性处理孔后激光制导电图案的制造电路板方法,在已经完成内层线路制作的多层覆铜箔板上涂覆一种疏化学镀活性种子并且抗电镀的有机掩蔽材料,钻孔并只在孔壁上电镀沉积铜至需要的厚度后,再电镀沉积可焊性金属层,然后,用激光去除非线路区域的掩蔽层、铜箔制造导电图案。本发明通过抗电镀的有机掩蔽材料掩蔽板面,只在孔壁上沉积金属,电路板金属化孔质量更好使其更好地满足电气要求；激光光斑直径可以根据图案尺寸改变,去除铜箔速度快,加工效果更好,可以制造更精细的导电图案；用激光直接去除材料制造阻焊图案,步骤少,质量好,成本低,环境友好。(The invention relates to a method for manufacturing a circuit board by only electroplating thickened holes and processing holes with weldability and then making a conductive pattern by laser. The surface of the board is masked by the electroplating-resistant organic masking material, and only metal is deposited on the hole wall, so that the quality of the metallized hole of the circuit board is better, and the metallized hole of the circuit board can better meet the electrical requirements; the diameter of the laser spot can be changed according to the size of the pattern, the copper foil removing speed is high, the processing effect is better, and a finer conductive pattern can be manufactured; the solder resist pattern is manufactured by directly removing materials by laser, and has the advantages of few steps, good quality, low cost and environmental friendliness.)
1. A method for manufacturing a circuit board by laser-processing a conductive pattern after only plating thickened holes with solderability is characterized in that: coating an organic masking material which is sparse and chemically plated with active seeds and is resistant to electroplating on a multilayer copper-clad laminate on which inner-layer circuits are manufactured, drilling holes, electroplating and depositing copper on hole walls to a required thickness, then electroplating and depositing a weldable metal layer, and then removing the masking layer and the copper foil in a non-circuit area by laser to manufacture a conductive pattern, wherein the steps are as follows:
(1) coating an organic masking material on the surface of a workpiece which is internally provided with no or more than one layer of conductive patterns and is coated with copper foil on two sides;
(2) drilling according to the design requirement;
(3) conducting electricity through the holes;
(4) electroplating, namely depositing copper on the hole wall to thicken the conductive layer to the thickness required by final inspection;
(5) electroplating, namely depositing a weldable metal layer on the hole wall;
(6) laser removing the masking material layer on the surface of the non-circuit area;
(7) removing the copper foil in the non-circuit area by laser to manufacture a conductive pattern;
(8) coating and curing a non-photosensitive solder resist on the non-circuit area at one time;
(9) removing the organic material on the electric conductor of the welding area by laser at an assembly site, manufacturing a solder resist pattern, and cleaning and performing weldability treatment on the surface of the welding area;
(10) adding solder to the connecting disc, carrying out component mounting and insertion, and carrying out remelting welding or wave soldering.
2. The method of claim 1, wherein: the organic masking material is thinned and chemically plated with active seeds, resists acid, alkali and organic treatment before hole metallization and resists electroplating; comprises dry PET, PI, RPP, BOPET, BOPP, PA, PPE, PTFE, PP, PE, PVC, EVA high molecular materials made of single-component, multi-component, composite thermosetting, photo-curing, hot-pressing adhesion, non-photosensitive and photosensitive materials, organic silicon and modified paint thereof, and Parylene coating; the film comprises thermosetting, light-curing and hot-pressing adhesive films made of the materials and modified substances thereof, and a composite adhesive for the films, wherein the film comprises the materials which are overlapped layer by layer and monomeric, prepolymerized or polymerized liquid and paste materials; the coating method of the material comprises one or more of rolling, hot pressing, printing, plating, spraying and curtain coating; the thickness of the material is greater than the total metal thickness thickened on the line, and ranges from 0.3 μm to 3000 μm, and the preferred thickness is 1um to 100 um.
3. The method of claim 1, wherein: the method used in the step (2) comprises the steps of drilling by a mechanical means, drilling by laser, drilling by combining the mechanical means and the laser, deburring after drilling and removing glue residues.
4. The method of claim 1, wherein: the laser processing equipment used in the steps (2), (6), (7) and (9) can convert the diameter of a light spot interacted with the material on line by taking energy and power on a unit area as constant quantities according to the structure of a circuit graph; the laser processing equipment comprises one or more sets of data acquisition and processing systems, an equipment operating system, a laser light source, a light beam shaping and transmission system, a laser focusing system, a workpiece clamping and automatic and manual feeding and discharging system, a workpiece positioning and movement and control system with light beams, a visual detection and laser power monitoring and compensation system, a cleaning and constant temperature system, and light beam types comprise Gaussian, flat top, annular, Bessel and multipoint nanosecond ultraviolet laser beams, picoseconds and femtosecond laser beams.
5. The method of claim 1, wherein: the hole electroconducting in the step (3) comprises a chemical copper deposition process of forming an initial conducting layer through activation of deposited colloidal palladium and chemical copper plating; also comprises a diameter electroplating process for directly forming an initial conductive layer by depositing carbon black, graphite, colloidal palladium and ionic palladium in the hole and using conductive polymers; comprises physically brushing, wiping, grinding or chemically removing the residual active conductive active material on the surface of the plate after direct electroplating or before electroless copper plating after activation.
6. The method of claim 1, wherein: after the step (1) is carried out, before or after the steps (2) and (3) are carried out, and before the step (4) is carried out, removing the anti-electroplating masking film layer on the surface of the clamping point of the electroplating clamp by using laser to expose the copper surface of the contact area with the electroplating clamp; and removing dead copper areas without electric function, or areas with conductive layers needing to be removed and having no negative influence on the subsequent removal process, or areas with copper thickness not influencing the function of the dead copper areas, or areas with copper thickness having positive influence on the function by increasing the electroplating-resistant film masking layer on the areas with copper thickness by using laser, wherein the dead copper areas are not on the non-circuit and have an interval more than 30 mu m with the circuit, or areas with conductive layers needing to be removed and having no negative influence on the subsequent removal process, or areas with copper thickness not influencing the function of the dead copper areas, or areas with copper thickness having positive influence on the function of the dead copper areas are increased, and the copper foil surfaces below the areas are exposed, so that a dispersed pattern which is beneficial to the balanced distribution of electroplating current when the hole wall is electroplated is formed.
7. The method of claim 1, wherein: the steps (6) and (7) comprise selectively removing the unwanted copper foil on the surface of the substrate by using the laser photoetching function and the combined action of the laser photoetching function and the laser heating function to manufacture the conductive pattern; or (6) removing the electroplating-resistant masking film on the non-circuit area without removing the electroplating-resistant masking film, and removing the unwanted copper foil on the surface of the substrate together with the electroplating-resistant masking film to manufacture a conductive pattern; during the machining process, the beam diameter D of the photoetch laser and the beam diameter D of the heating laser may vary depending on the circuit structure, and the insulation spacing between conductors.
8. The method of claim 6, wherein: when the insulation space S between the two conductors is wider, the value satisfies S>2dmaxWhen the processing scheme is nd + (n-1) D, i.e., n-number of photoetched vaporization removals having a beam diameter of D and (n-1) number of thermal lift-off removals having a beam diameter of D, where n is an integer, n ≧ 2, and preferably the value of n is smallest, and D ismaxThe maximum value of the beam waist diameter of the laser beam for the task of the photoetching processing is D, and the beam waist diameter of the laser beam corresponding to the materials to be stripped with different widths for the task of the heating processing is D; when the width S of the conductive layer between two conductors satisfies 2dmax≥S≥dmaxWhen the conductor is etched, S-d 1+ d2 is selected, that is, two photoetching laser beams with photoetching diameters of d1 and d2 are selected to remove the conductive material between the two conductors, wherein d1 and d2 can be the same or different; when the insulation space S between two conductors is smaller than the maximum beam waist diameter of the task of photoetching, i.e. dmaxWhen the diameter of the light beam is larger than or equal to S, the processing scheme is S-d, namely the diameter of the light beam is selected, so that the conducting material between the two conductors is removed by just one photoetching laser beam with the diameter of the light beam being d.
Technical Field
The invention belongs to the technical field of circuit manufacturing, relates to a laser processing technology, and particularly relates to a method for manufacturing a circuit board by laser processing a conductive pattern after electroplating thickening and hole weldability processing.
Background
Electronic products generally go through three stages of design, preparation and assembly from concept to finished product.
After the physical design is completed, material preparation is performed, including selection and customization of various components, connectors, display modules, and other functional modules. Among them, one of the most important materials is a bare circuit board, because the bare circuit board is used to support components and plays a role in electrical interconnection among pins of the components, which is a key factor affecting the quality and reliability of electronic products and the difficulty, cost, speed of the whole manufacturing process, and must be customized according to the design requirements and the properties of the products. A bare circuit board, referred to as a bare board for short, refers to a circuit board on which components have not been mounted, and is also referred to as a printed circuit board, a circuit board, and a printed circuit board. The bare board is typically custom-made as needed by a manufacturer who specializes in manufacturing printed circuit boards. Taking a multilayer circuit board as an example, the process flow of bare board manufacturing is roughly as follows: manufacturing an inner layer conductive pattern, blackening/browning and laminating, drilling holes on a multi-layer copper foil-coated insulating substrate, metallizing the holes, manufacturing an outer layer conductive pattern, removing a metal corrosion resistant film or an organic corrosion resistant film, coating a solder resist, manufacturing a solder resist pattern and generating a welding area, performing solderability coating treatment on the surface of the welding area, manufacturing a mark symbol, and delivering the product to a manufacturer in an assembly stage.
The electronic product is assembled, i.e. various materials are assembled, matched and combined together, and the fixation of the positions of the materials and the corresponding electrical connection and functional matching are realized by connecting means such as soldering, fastening, bonding and the like. In a narrow sense, the assembly process of mounting and soldering components to a circuit board is often referred to as assembly. The product after the components are assembled is generally called an assembly board. Where distinction is not required, the bare board and the assembled board are generally referred to as circuit boards.
The former assembly technique mainly uses through-hole insertion method, i.e. the pins of various components, connectors, functional modules, etc. are inserted into the mounting holes of bare board, and then these pins, hole wall and soldering pad are soldered together by using soldering flux so as to fix the components on the circuit board, and the electric interconnection between the pins of the components can be implemented by means of soldering pad, interconnection line and relay hole on the circuit board. The present electronic products are assembled and connected by adopting surface mounting technology, i.e. firstly, the soldering paste is coated on the connecting disc of the circuit board, i.e. the bonding pad, then the pins of various components, connectors, functional modules, etc. are correspondingly placed on the soldering paste layer of the connecting disc, finally, the circuit board is heated, so that the powdered or granular solid metal tin/tin alloy in the soldering paste is melted, the melted solder infiltrates the terminal electrodes/pins of the components and the bonding pad of the circuit board, when the solid metal is cooled, the terminal electrodes of the components and the connecting disc are soldered together, thereby the components are mounted and fixed on the surface of the circuit board, and the electrical interconnection between the components is realized through the conductive channel formed by the bonding pad, the conducting wire and the hole on the circuit board. The assembly of the circuit board is carried out by a professional assembly factory or is automatically completed by an electronic product development mechanism. Taking the SMT technology as an example, the assembly process flow of the circuit board is roughly: the method comprises the steps of printing solder paste on a soldering tray from a circuit board of a bare board manufacturing factory, picking up components and attaching the components to the surface of the circuit board, heating the components to enable the solder paste to reflow again to achieve soldering between pins and the soldering tray.
Considering the whole process of manufacturing bare board and assembling elements of circuit board, it can be seen that the key of manufacturing bare board is the processes of making conductive pattern, laminating, drilling and metallizing hole, making resistance welding pattern and coating weldability, and the processes of coating soldering paste, sticking and inserting elements and welding are the key processes of assembly production stage. Further analysis shows that the processes are essentially for the purposes of fixing the components and electrically interconnecting the components. Wherein the conductive pattern fabrication is concerned with the fineness and electrical performance of the circuit board circuitry; the manufacture of the solder resist pattern and the solderability coating are finished in a bare board stage, but are the basis of production in a mounting stage; the drilling and hole metallization affects the connection density, mechanical performance, application environment, and matching degree of the plug-in components during installation and fixation of the circuit board, determines the electrical performance and reliability of the Z-direction interconnection between the horizontal conductive layers of the circuit board, and directly affects the difficulty of the manufacturing process of the horizontal electrical connection conductive pattern of the circuit board.
With the progress of social economy, the requirements on electronic products are higher and higher, elements are smaller and smaller, functions are stronger and more, the number of pins is more and more, the requirements on conductive patterns and solder resist patterns are finer and more accurate, the requirements on holes are smaller and deeper, and all process problems influence each other no matter in the manufacturing stage of a bare board or in the assembling stage of components, so that the technical difficulty in manufacturing the circuit board is higher and higher.
For example, in the current hole metallization process, in order to satisfy the minimum reliability and electrical requirements of a Z-direction electrical interconnection physical carrier, that is, the conductive layer of the hole wall reaches the minimum thickness, metal copper must be deposited on the hole wall by using an electroplating technology, and an electrical conduction channel is required in the electroplating process. In IPC standard IPC-6012, there is a clear requirement for the copper thickness of the metallized hole, which is at least 20 μm. The current circuit board manufacturing process has limited deep plating capability, when the wall copper thickness reaches mum, the increased copper thickness of the board surface exceeds the wall copper thickness, and after the added thickness of the wall copper thickness and the original copper foil thickness of the material, the total copper thickness exceeds mum. However, the original copper foil on the board surface must be simultaneously thickened by the electroplating thickened holes, the performance of the circuit board is not enhanced due to the consumption of copper resources, the difficulty of subsequent processes is not reduced, and on the contrary, the performance and the process of the circuit board are negatively influenced by the processes in the following aspects:
first, the thickness of the conductive via is smaller than that of the conductive via on the board, which results in the electrical performance of the Z-direction conductive link being inconsistent with that of the X, Y planar conductive link. Secondly, the conductive layer produced in the process of electroplating the hole copper on the circuit board becomes the top layer of the conductive layer of the future conductive pattern, and is the main medium of electrical signal transmission with higher frequency under the action of skin effect, and the quality of the copper layer deposited by the electroplating technology in the production of the circuit board is slightly lower than the purity of the copper foil manufactured by the original electroforming or rolling technology, the crystal is slightly rough, and the quality of the electrical and mechanical properties is slightly poor, so that the increase of the thickness of the conductive layer is not beneficial to the high-speed and high-frequency transmission of signals. Thirdly, the increase of the copper foil thickness and the resulting lateral etching are factors for the fineness of the conductive pattern, in the process of manufacturing the conductive pattern by using the chemical etching technology, the etching solution is contacted with the copper foil for etching, the etching is not only performed towards the depth of the copper foil vertically, but also performed at two lateral sides of the lead due to the contact of the etching solution and two lateral sides of the lead, the thicker the copper layer to be etched is, the longer the time is, the more serious the lateral etching phenomenon is, the lateral etching not only reduces the width of the lead, but also generates line breakage in serious cases. Fourthly, the copper foil is thick and uneven, which is the bottleneck of wide application of the laser-induced electrical pattern technology, obviously, the thicker the copper foil is, the greater the required laser energy is, the more passes are required to be processed, and the slower the processing process is; the more uneven the thickness of the copper foil, the more difficult the photoetching process, whether the phenomenon that the residual copper affects the insulation performance occurs when the applied laser power is too small in the area with larger copper foil thickness, the copper removal is not clean, or the phenomenon that the quality of the circuit board is affected when the applied laser power is too large in the area with smaller copper foil thickness ablates the insulation material below the copper foil.
In the prior art, the manufacturing process of the conductive pattern has the problems that the traditional etching method has complex process, a corrosion-resistant mask needs to be manufactured by using a pattern transfer process, a photosensitive material needs to be used in the pattern transfer process, a mask plate for selective exposure needs to be manufactured firstly, the corrosion-resistant mask needs to be removed after the conductive pattern is manufactured by etching, and the phenomena of underetching, overetching, side etching and uneven etching which are caused by the etching often cause the quality control factors to be mutually lost, so that the problem is serious; the process of directly removing the organic material etching-resistant mask, the electroplating-resistant mask and the solder-resistant mask by laser and the process of directly removing the conductive pattern by the conductive copper foil method are simple, but the laser spot diameter is small, point-by-point line-by-line processing is needed, the speed is low, and the efficiency is low. In addition, in the processing of the conductive pattern by the method of directly removing the conductive copper foil by laser, the thickness of the copper foil layer on the substrate becomes thicker and more uneven after the hole is metalized, so that the laser energy is difficult to change correspondingly in real time, and the removal quality is difficult to ensure.
The problems of solder resist pattern making and solderability coating are that, as with the making of conductive patterns, the traditional technique for making solder resist patterns is a pattern transfer process, which requires the use of photosensitive materials, and also requires the first making of masking plates for selective exposure, with the baking and exposure effects interfering with each other, making quality control difficult, and frequent occurrence of defects such as pads on solder resists. However, the solderability coating by hot air leveling or electroless nickel gold technology has the defects of complex components and complicated process, and the confusion of affecting the reliability due to unclear welding machine cleaning can be brought.
In summary, it is understood that the current circuit board manufacturing technology includes a series of indirect processing, chemical treatment, and wet manufacturing processes. The single-function flows have inherent technical limitations, and the single-function flows are mutually restrained and are the root cause for limiting higher quality, higher efficiency and more environmental friendliness, and not only need to improve and update each single-function flow, but also need to be comprehensively optimized and upgraded on the whole.
Disclosure of Invention
Aiming at the defects of the prior art, the invention develops a method for manufacturing a circuit board by only electroplating thickened holes and processing the holes with weldability and then conducting a conductive pattern, which comprises the following specific steps:
(1) coating an organic masking material on the surface of a workpiece which is internally provided with no or more than one layer of conductive patterns and is coated with copper foil on two sides;
(2) drilling according to the design requirement;
(3) conducting electricity through the holes;
(4) electroplating, namely depositing copper on the hole wall to thicken the conductive layer to the thickness required by final inspection;
(5) electroplating, namely depositing a weldable metal layer on the hole wall;
(6) laser removing the masking material layer on the surface of the non-circuit area;
(7) removing the copper foil in the non-circuit area by laser to manufacture a conductive pattern;
(8) coating and curing a non-photosensitive solder resist on the non-circuit area at one time;
(9) removing the organic material on the electric conductor of the welding area by laser at an assembly site, manufacturing a solder resist pattern, and cleaning and performing weldability treatment on the surface of the welding area;
(10) adding solder to the connecting disc, carrying out component mounting and insertion, and carrying out remelting welding or wave soldering.
And (1) coating an organic masking material on the surface of a workpiece which is internally provided with one or more layers of conductive patterns and is covered with copper foil on two sides.
In the prior art, a photoinduced dry film is generally used as an electroplating-resistant mask, the photoinduced dry film is of a three-layer structure, a photosensitive adhesive coating is arranged between a carrier film and a protective film and consists of an adhesive, a photopolymerization monomer and the like, the pattern forming process is complex, and the steps of photoplotting, plate making, film pasting, exposure and development are required; moreover, the price is expensive, the strength is not high, the thickness is large, generally more than 20 μm, the resolution is limited, and the masking effect is poor.
The masking film does not need to have photosensitive performance, but has the advantages of hydrophobic chemical plating active seeds, resistance to treatment of acid, alkali, organic matters and the like before hole metallization, and electroplating resistance; the paint comprises high polymer materials such as dry PET, PI, RPP, BOPET, BOPP, PA, PPE, PTFE, PP, PE, PVC, EVA and the like which are made of single-component, multi-component, composite thermosetting, photo-curing, hot-pressing adhesion and non-photosensitive and photosensitive materials, and comprises organic silicon and modified substance paint thereof, and other resin and modified substance paint thereof; including Parylene/Parylene coatings, other polymer coatings; the film which is made of the materials and the modified substances thereof and can be thermally pressed and adhered, the film is compounded with the binder, and the film which is made of other materials and can be thermally pressed and adhered is compounded; comprises the above materials, and the materials in the form of monomer, prepolymerization, or polymerized liquid or paste; the coating method of the material comprises one or more of rolling, hot pressing, printing, plating, spraying and curtain coating; the thickness of the material is greater than the total metal thickness thickened on the line, and ranges from 0.3 μm to 3000 μm, and the preferred thickness is 1um to 100 um.
The method used in the step (2) comprises the steps of drilling holes by mechanical means; comprises drilling holes with laser; comprises mechanical and laser combined drilling; the method comprises the processing steps of deburring after drilling, removing glue residues and the like.
In fact, the common pre-coated pressure-sensitive coating film and the heat-sensitive coating high polymer film can meet the requirements after being treated by the sparse chemical plating active seeds. For example, a thermo-sensitive PET or BOPET film with a thickness of 20 μm is hot-pressed as an electroplating-resistant mask.
And (2) drilling according to design requirements. The material to be drilled is a composite material formed by alternately laminating conductive copper foil and insulating material, and different from the traditional technology, the material drilled by the invention is additionally provided with a high polymer masking film attached to the surface of the board. The drilling tool may be either a mechanical drill or a focused laser beam.
If a mechanical drill bit is used for drilling, epoxy drilling dirt may appear on the hole wall, and before hole conductivity is carried out, the epoxy drilling dirt is removed by using a liquid medicine or a process which does not damage the high polymer film so as to ensure the hole metallization quality.
Wherein, in step (3), the hole is electrically conductive. The purpose of this step is to deposit an initial conductive layer on the walls of the hole to prime the next step of plating the hole cylinder.
The traditional chemical copper deposition process is that active noble metal particles are firstly deposited on the hole wall, and then copper hole metal is deposited to realize the surface conduction of the hole wall, so the hole conduction is the hole metallization process in the existing circuit board manufacturing technology; in the direct electroplating process, particularly in the carbon film method and the polymer film method, the substance for realizing the pore wall conductivity is not metal, so that the description of the process for forming the initial conductive layer by using the pore metallization is not accurate. In the present invention, the description is still made by using hole metallization when referring to the prior art, and the description is made by using hole conduction when referring to the process of the present invention, and the hole conduction includes both a hole conduction process implemented by using metal and a hole conduction process implemented by using a non-metal material.
There are two methods for achieving the object of this step, one is a direct electroplating method, for example, a carbon film method is used to blacken the hole, and an initial conductive layer is formed after the "pretreatment → black hole" step; the other is the traditional chemical copper deposition process, and the initial conducting layer is formed after the plating pretreatment → the activation treatment → the chemical copper plating. Wherein the electroless copper plating thickness is up to a lower limit that ensures process reliability, e.g. 1 μm.
In the step, because the plate surface is covered with the high polymer film, and the outer surface of the film surface has the property of thinning chemical plating active seeds, the plate surface is masked, and after the step of directly electroplating black holes or after the activation treatment of a chemical copper deposition method, the plate surface does not have conductive substances such as carbon black, graphite and the like, and does not have substances such as metal palladium active particles with catalytic action and chemically deposited copper and the like. Therefore, the plate surface and the copper-clad foil conducting layer can be maintained in an electric insulation state, and no metal copper is deposited on the plate surface in the subsequent electroplating process, so that the purpose of electroplating the copper conducting layer on the hole wall only is achieved.
And (4) electroplating copper, and depositing copper on the hole wall to thicken the hole cylinder.
In order to solve the problems that the total area is too small, the power lines are not uniform step by step, the current density is not easy to control and the like when the hole cylinder is electroplated, an electroplating balance block which is beneficial to improving the quality can be manufactured on a workpiece. The method comprises the following steps: after the step (1) is carried out, before or after the steps (2) and (3) are carried out, before the step (4) is carried out, laser is used for removing dead copper areas without electric functions, which are not wires and have an interval of more than 30 microns and preferably more than 50 microns with the intervals with the wires, or areas, the conducting layers of which need to be removed and do not have negative influence on the subsequent removing process, or areas, the functions of which are not influenced by the copper thickness, or areas, the functions of which are positively influenced by the copper thickness, of which are added with anti-electroplating film masking layers, so that copper foil surfaces below the areas are exposed, and dispersed patterns which are favorable for the balanced distribution of electroplating current when the hole walls are electroplated are formed.
The electroplated balance block is manufactured by only removing the organic material on the surface of the copper foil at the corresponding part. In this case, the optical power density of the focused laser spot is greater than the minimum power density required to remove the organic material and lower than or close to the minimum power density required to remove the underlying metal layer. Preferably greater than 1.2 times the minimum optical power density required to remove the organic material.
The control point of the step (4) is the plating time. At the moment, the whole area of the plate surface except the hole cylinder and the electroplating balance block is covered by a mask which is made of insulating materials and is in contact with electroplating liquid medicine, but copper is not deposited on the surface of the plate surface, so that only the hole cylinder and the balance block can deposit copper in the electroplating process, and the electroplating time is enough, a copper deposition layer with enough thickness can be obtained on the hole cylinder, and the purpose of selectively controlling the thickness of copper on the hole wall is achieved.
And (5) electroplating a weldable metal protective layer on the hole wall.
Such metals are not only protective layers for the corresponding areas when the circuit boards are transported and stored, but also functional coatings for increasing the solderability of the soldering areas.
The invention uses non-photosensitive plating-resistant material, has good masking capability, can endure longer electroplating time, and can also endure more severe plating solution and operation conditions. In addition, the other areas of the plate surface are masked by the high polymer film, so that metal can be deposited only on the hole wall and the surface of the electroplated balance block, the plating area is relatively small, and materials are saved. Therefore, more varieties of metals with both protection and solderability can be selected, such as nickel and gold, and tin.
And (6) laser removing the high polymer film layer on the surface of the non-circuit area.
The high polymer film coated on the surface of the board only plays a role of masking the lower copper foil during hole conduction and electroplating. After the plating of the holes is finished, the high polymer film on the whole plate surface can be removed at one time; it is also possible to leave the polymer film on the conductive pattern area and remove only the polymer film in the non-circuit area together with the conductive material thereunder when the conductive pattern is formed.
And removing the high polymer film layer, wherein the organic material on the surface of the copper foil at the corresponding position is only required to be removed in the same process of manufacturing the electroplating balance block and removing the high polymer film layer on the bonding pad. In this case, the optical power density of the focused laser spot used is greater than the minimum power density required to remove the organic material and is lower than or close to the minimum power density required to remove the underlying metal layer. Preferably greater than 1.2 times the minimum optical power density required to remove the organic material.
Removing the polymer film in large area by selecting CO2And (4) processing equipment with a laser as a light source. CO 22The laser emitted by the laser has a wavelength of about 10 μm and is in a far infrared band. Copper has a low absorption coefficient for laser light in this band, but the laser light in this band has good coupling with most high polymers. Therefore, the laser parameter range for removing the high polymer without damaging copper is wide. Selection of CO2The laser can use large-diameter light spots, has high removal efficiency, low cost and high cost performance, and does not damage copper.
In addition to CO2Besides laser, the pulse fiber laser with the wavelength of about 1 mu m has stable performance, convenient use and low cost, and is also suitable for removing the solder resist material and manufacturing the solder resist pattern.
And (7) laser removing the copper foil layer on the non-circuit area to manufacture the conductive pattern.
After the copper foil layer on the non-circuit area is removed, an insulating pattern is formed on the insulating substrate in the area without the copper foil, and a conductive pattern is formed on the insulating substrate by the conductive layer on the hole, the pad and the circuit area.
Because the present invention is capable of selectively plating holes, the technique of removing the conductive material of the non-wiring region with a laser is easier to implement. In the current general circuit board manufacturing technology, after the hole metallization electroplating process, due to the limitation of the plating uniformity capability of the hole metallization system, the deposition speed of copper is different in different areas on the same substrate material, so that the thickness of the total conductive layer is greatly different. Thus, when the laser is used for removing the conductive layer of the non-circuit part, if the laser parameters do not change along with the copper thickness, the copper removal is not clean at the part with large total copper thickness, the residual copper affects the insulation performance, or the energy applied to the part with small total copper thickness is too large, and the insulation material is ablated.
By implementing the technical scheme of the selective electroplating hole, copper can not be deposited in a non-line area, particularly on a laser photoetching removal path, a conducting layer under the laser photoetching path is kept to be an original copper foil, the thickness is uniform, and the laser processing difficulty is reduced. The invention adopts Striping and Stripping method/Striping and Striping of German and Chinese technology, firstly uses laser light etching to vaporize conductive material point by point and layer by layer to form a closed separation line, subdivides the conductive layer area to be removed into small pieces with mutually heat-insulated areas in a certain range, which is called Striping/Striping; the die is then heated with a laser to reduce the bonding force between the die and the substrate and release the die from the substrate, known as lift-off/striping.
The processing steps of the slitting and stripping method are as follows in sequence: firstly, projecting light etching laser point by point, vaporizing and removing the conductive material under the envelope curve of each conductive pattern, and manufacturing a closed insulating channel by taking a contour line as a boundary; then, projecting light etching laser point by point, vaporizing and removing the conductive material under the separation line, and subdividing the large conductive material to be removed into small pieces which are mutually insulated; and then sequentially projecting heating laser onto the small pieces to reduce the bonding force between the small pieces and the base material and deform the small pieces, separating the small pieces from the workpiece under the combined action of auxiliary gas, and transferring and collecting the small pieces.
When the strip is divided and stripped, the insulation space S between the two conductors is wider, and the numerical value satisfies S>2dmaxWhen the processing scheme is nd + (n-1) D, namely n light etching vaporization removal with the beam diameter of D and (n-1) heating stripping removal with the beam diameter of D, wherein n is more than or equal to 2, and the n value is preferably the minimum; when the width S of the conductive layer between two conductors satisfies 2dmax≥S≥dmaxWhen S is d1+ d2, two photoetching laser beams with photoetching diameters of d1 and d2 are selected to remove the conductive material between the two conductors, wherein d1 and d2 can be the same or different; when the insulation space S between two conductors is smaller than the maximum beam waist diameter of the task of photoetching, i.e. dmaxIf S is greater than or equal to S, the processing scheme is S-d, i.e. the beam diameter is selected such that exactly only one photoetched laser beam with a beam diameter d is used for removalA conductive material between the two conductors. Wherein S is the insulation space between two conductors, namely the width of the conductive layer to be removed, D is the diameter of a photoetching laser beam, D is the diameter of a heating laser beam, and n is an integer of 1, 2, 3, 4 and the like.
The laser striping and stripping technique is implemented, the electroplating-resistant masking film-high polymer film in the non-circuit area is not necessarily removed, for example, when the ultraviolet band laser processing is used, or picosecond laser is used for striping, the masking film and the copper foil layer below the masking film can be vaporized together by laser light etching until the insulating substrate layer stops to form a heat insulation channel; in the peeling, the masking film and the copper foil layer thereunder are heated together, and the masking film and the copper foil layer are peeled off in bulk by thermal deformation and reduction of the bonding force with the insulating base material. To be suitable for laser processing, the anti-plating masking film may be selected to be colored to produce better absorption.
Wherein, step (8), the surface of the workpiece is coated with a high polymer film.
The high polymer film, namely the solder resist, coated in the step has the effect of preventing short circuit caused by overflow of solder between welding points when components are welded in the assembly stage of the circuit board; firstly, the surface and the side wall of a conducting wire forming a conducting pattern on the circuit board are physically shielded, and damages such as oxidation, scratch and the like caused by the external environment are prevented.
In the prior art, liquid photosensitive ink is generally adopted as a solder resist, the solder resist contains an adhesive and a photopolymerization monomer, the pattern forming process is very complicated, and multiple processes such as coating, pre-baking, exposure, development, curing and the like are required; moreover, the cost is high, the resolution is not high, and the coating quality between the fine pitch connecting discs is difficult to guarantee.
The invention uses laser light etching to remove the means to make solder resist pattern, the solder resist does not need to have light sensitivity, the common precoating pressure sensitive coating film and heat sensitive coating film can meet the requirement, the price is cheap, the resolution ratio is high, can make the meticulous pattern structure. In addition, the invention adopts hot-pressing coating, does not need an additional curing process, leaves the solder resist pattern to be manufactured by laser on site before the component is assembled, and has simple flow. For example, a thermo-sensitive PI, PVC, PC, PET, PP, RPP, BOPET, BOPP, PA, PPE, parylene film with a thickness of 20 μm to 200 μm is used as a solder resist.
And (9) removing the high polymer film layer on the surface of the welding area by using laser to manufacture the solder resist pattern.
The technical key points of using laser to manufacture the solder resist pattern are as follows: the pattern size is accurate and smooth, and no burr is generated; the solder resist is removed cleanly, and the solder resist has no residue and no carbonization; the metal performance of the welding area is kept, the metal is not damaged, and remelting and color change are avoided; the adhesive force between the bonding pad and the base material is not affected, no overheating exists, the bonding pad is not raised, and the adhesive force is not reduced. The solder resist is generally a high molecular polymer, has large difference with metals physically and chemically, is removed by laser processing, is easier to find a window meeting the technical requirements, and can be finished by using laser with one wavelength, such as nanosecond UV pulse laser, or picosecond and femtosecond laser to produce a solder resist pattern; or by combining two wavelengths of laser light. For example, selecting a large spot CO2Removing the high polymer with high efficiency by laser to manufacture patterns; and removing the solder resist residues by nanosecond UV pulse laser or picosecond and femtosecond laser.
And (10) adding solder to the connecting disc, carrying out component mounting and inserting, and carrying out remelting welding and/or wave peak welding.
In the present invention, laser processing is used for both drilling and removing the high polymer film on the copper foil layer as well as removing the copper foil. The laser processing equipment comprises one or more sets of data acquisition and processing systems, an equipment operating system, a laser light source, a light beam shaping and transmission system, a laser focusing system, a workpiece clamping and automatic and manual feeding and discharging system, a workpiece positioning and light beam movement and control system, a visual detection and laser power monitoring and compensation system, a cleaning and constant temperature system, a laser and equipment safe use system and the like; when the high polymer film or the copper foil on the non-circuit area is removed by the laser, the laser parameters and processing data can be generated by taking the energy and power on a unit area as constant quantities, the diameter of a light spot interacting with a material as variable quantities, and one or a combination of the high processing speed, no overlapping or a certain amount of overlapping when the processing path is overlapped, and a certain overlapping quantity or spacing quantity between pulses as priority according to the shape and the size of the processed area; in the machining process, the diameter of a light spot can be changed on line according to the preset laser parameters and the machining path requirements aiming at the structure of a machined graph.
The invention has the advantages and effects that:
1. the invention adopts the masking film with the sparse chemical plating active seeds on the surface, only the wall of the hole is electroplated and thickened, the thickness of the plating layer is easy to control, and the problem that the thickness of the plating layer of the hole wall is thinner can be solved.
2. The invention uses laser to make anti-plating pattern, which can only plate the solderability protection metal on the hole wall and the welding disc.
3. The invention realizes only electroplating holes and bonding pads, does not increase the thickness of the non-circuit part conductive layer, is suitable for directly removing the copper foil at the non-circuit part by using laser to manufacture the conductive pattern, and can manufacture finer conductive patterns.
4. In the laser pattern manufacturing process, the diameter of the focused laser beam is changed according to the shape and the size of the removed area, so that the diameter of the focused laser beam or the multiple of the diameter of the focused laser beam is exactly equal to the width of the area to be removed, the overlapping of laser processing areas can be reduced or removed, and the processing efficiency is improved.
5. When the conductive pattern is manufactured by laser, the anti-electroplating mask can be removed simultaneously, a special film removing process is not needed, and the steps are few.
6. The invention uses the film precoated with the heat-sensitive and pressure-sensitive solder-resisting materials as the solder resist, and uses the lasers with different wavelengths, pulse widths and power densities to manufacture the solder resist pattern, thereby having higher efficiency and better processing effect.
Drawings
FIG. 1a is a process flow diagram of the present invention (steps 1-5);
FIG. 1b is a process flow diagram of the present invention (steps 6-10);
in the figure: 1. an insulating substrate; 2. copper-clad plate copper layer; 3. a layer of organic masking material; 4. starting a conductive layer; 5. electroplating a copper layer; 6. a solderable metal protection layer; 7. a non-photosensitive solder resist layer; 8. solderability treating the surface; 9. welding flux; 10. component element
Detailed Description
The invention will be further described with reference to the following examples. The following examples are illustrative and not limiting, and are not intended to limit the scope of the invention.
The common copper clad laminate in the electronic industry is used as a base material for manufacturing a circuit board, and comprises an insulating substrate 1 and a copper clad laminate 2.
Example 1
In this embodiment, a double-sided printed circuit board is taken as an example, and the specific processing steps are as follows:
(1) and (3) attaching a high polymer film on the double-sided copper-clad plate to form an organic masking material layer 3.
And (3) mechanically brushing the copper-clad plate with the cut size, and roughening and cleaning the surface of the copper-clad plate to enhance the bonding force between the copper surface and the high polymer film to be attached. Then, hot-pressing and laminating the sparse chemically active seeds on the double-sided copper-clad plate through a laminator and having an anti-electroplating high polymer film BOPET, wherein the laminating parameters are as follows: pressure 10kg/cm2, temperature 90 ℃ and speed 1 m/min.
(2) Drilling;
and placing the coated copper clad laminate on an adsorption table, guiding the drilling engineering data file into an ultraviolet nanosecond laser machine, driving the laser machine, and selectively removing the conductive material layer and the insulating material layer by using the laser machine in the area where holes need to be manufactured to obtain the drilled substrate.
Further, an ultraviolet nanosecond laser machine is adopted to manufacture electroplating shunting patterns on the edge of the coated copper plate and a dead copper area without electrical performance, and current distribution during electroplating is balanced.
(3) Conducting the hole to form an initial conducting layer 4;
the hole is conducted in a black hole mode, and due to the fact that the BOPET film sparse with chemically active seeds is covered on the surface of the copper-clad plate, the black hole liquid cannot be attached to the film, and only the conductive carbon film is formed in the hole, so that consumption of the black hole liquid can be greatly reduced.
(4) Electroplating copper, namely electroplating thickened hole copper on the hole wall to form an electroplated copper layer 5;
calculating electroplating parameters according to the requirements of the electroplating area and the thickness of electroplated copper, wherein the copper plating parameters are as follows: 1ASD 90 min.
(5) Electroplating a weldable metal protection layer 6 on the hole wall;
and according to the requirements of the electroplating area and the thickness of the coating, hard gold is electroplated on the hole wall to serve as a weldable metal protection layer. Electroplating hard gold parameters: 0.5ASD 10 min.
(6) Removing the BOPET film layer on the non-circuit area by laser;
specifically, in this embodiment, a 20W uv nanosecond laser is used to remove the BOPET film on the non-circuit area, place the circuit board on the laser device adsorption table, import the engineering data of laser processing, precisely align the circuit board with the processing data, and remove the polymer film by laser photoetching. And after the top surface is processed, turning over the circuit board, and removing the film on the bottom surface of the copper-clad plate by the same method. The processing parameters are as follows:
power/W
frequency/kHz
Pulse width/ns
Processing speed/mm/s
Number of working operations
5
150
20
800
1
(7) Removing the copper foil layer on the non-circuit area by laser;
firstly, using photoetching laser to make insulation envelope processing, according to the processing data including beam diameter, envelope separation line path and its correspondent laser parameter, projecting laser to conductive material, photoetching, point-by-point vaporizing and removing conductive material to the surface of insulating material, and making closed insulation envelope channel around the conductive material to be retained. Then using photoetching laser to make slicing processing, according to the processing data including beam diameter, small piece separation line path and its correspondent laser parameter, projecting laser to conductive material, photoetching, point-by-point vaporizing and removing conductive material to the surface of insulating material, subdividing the large piece of conductive material to be removed into small pieces which are mutually heat-insulated. And finally, carrying out stripping processing by using heating laser, sequentially projecting laser to each small chip which is mutually insulated according to processing data comprising the diameter of a light beam, a heating line path for heating the small chip and corresponding laser parameters, heating the small chip to deform, reducing the bonding force between the small chip and the insulating material, separating the small chip and the insulating material under the combined action of auxiliary gas, separating the small chip from the insulating material, separating the small chip from the surface of the insulating material, transferring, collecting, and stripping and removing the small chip from the insulating material one by one.
Specifically, in this embodiment, a 20W infrared nanosecond laser is used to remove the copper foil on the non-wiring region to fabricate the conductive pattern. The conducting layer in the laser removing area is the original copper foil, the thickness is uniform, and the laser processing difficulty is greatly reduced. The processing parameters are as follows:
(8) attaching a PI film to the surface of the workpiece to form a non-photosensitive solder resist layer 7;
specifically, a laminator was used to laminate the double-sided board and the PI film, which are made of Kapton HN film manufactured by dupont and have a thickness of 25um, and a silicone rubber gasket was used as a thermocompression bonding gasket during lamination. The thermocompression bonding stage and parameters are as follows, depending on the material properties:
serial number
Pressing pressure (N/cm2)
Pressing temperature (. degree.C.)
Pressing time (minutes)
Stage 1
24
80
15
Stage 2
94
140
25
Stage 3
188
180
25
Stage 4
188
220
60
Stage 5
188→0
220 → room temperature
45
(9) Removing organic materials on the surface of the welding area by laser to manufacture a solder resist pattern, and cleaning and performing weldability treatment on the surface of the welding area to form a weldability treatment surface 8;
specifically, in this embodiment, a 20W ultraviolet nanosecond laser machine is used to fabricate the solder resist pattern, the circuit board is placed on a laser equipment adsorption table, engineering data of laser processing is imported, the circuit board and the processing data are aligned accurately, and the solder resist pattern is formed by laser photoetching. And after the top surface is processed, the circuit board is turned over, and the bottom surface solder resist pattern is manufactured by the same method. The processing parameters are as follows:
power/W
frequency/kHz
Pulse width/ns
Processing speed/mm/s
Number of working operations
6
200
20
600
1
(10) Solder 9 is added to the land, and component 10 is mounted, inserted, and reflow soldered or wave-soldered.
Example 2
In this embodiment, taking a multilayer copper-clad laminate with completed inner layer circuit as an example, the specific processing steps are as follows:
(1) and sticking a high polymer film on the multilayer copper-clad plate with the inner layer circuit.
Drying the multilayer copper-clad plate after the inner layer circuit is manufactured, and then hot-pressing and attaching sparse chemical active seeds on the multilayer copper-clad plate and having an anti-electroplating high polymer film BOPP, attaching parameters: pressure 15kg/cm2, temperature 100 ℃ and speed 1 m/min.
(2) Drilling;
and placing the multilayer copper-clad laminate on an adsorption table, guiding the drilling engineering data file onto an ultraviolet nanosecond laser machine, driving the laser machine, and selectively removing the conductive material layer and the insulating material layer by using the laser machine in the area where the hole needs to be manufactured to obtain the substrate after drilling.
Further, an ultraviolet nanosecond laser machine is adopted to manufacture electroplating shunting patterns on the edge of the coated copper plate and a dead copper area without electrical performance, and current distribution during electroplating is balanced.
(3) Conducting electricity through the holes;
and a chemical copper deposition mode is selected for hole conduction, because the surface of the copper-clad plate is covered with the BOPET film with sparse chemically active seeds, the activating solution cannot be attached to the film and is only absorbed in the holes, and because the surface lacks palladium nuclei, the chemical copper is only deposited in the holes to form a conducting layer.
Further, after drilling and before hole electroconduction, the multilayer copper-clad laminate needs to remove drilling stains generated by drilling, and drilling stain removing liquid medicine which does not damage the BOPP film is preferred.
(4) Electroplating copper, namely electroplating thickened hole copper on the hole wall;
calculating electroplating parameters according to the requirements of the electroplating area and the thickness of electroplated copper, wherein the copper plating parameters are as follows: 0.8ASD 90 min.
(5) Electroplating tin and lead on the hole wall;
and electroplating tin and lead on the hole wall and the bonding pad as a weldable metal protective layer according to the requirements of the electroplating area and the coating thickness. Parameters of tin and lead electroplating: 1ASD 15 min.
(6) Removing the BOPP film layer on the non-line area by laser;
specifically, in this embodiment, a 20W ultraviolet nanosecond laser is used to remove the BOPP film, the circuit board is placed on the laser device adsorption table, engineering data of laser processing is imported, the circuit board and the processing data are accurately aligned, and the BOPP film is removed by laser light etching. And after the top surface is processed, turning over the circuit board, and removing the film on the bottom surface of the copper-clad plate by the same method. The processing parameters are as follows:
power/W
frequency/kHz
Pulse width/ns
Processing speed/mm/s
Number of working operations
6
200
20
600
1
(7) Removing the copper foil layer on the non-circuit area by laser;
firstly, using photoetching laser to make insulation envelope processing, according to the processing data including beam diameter, envelope separation line path and its correspondent laser parameter, projecting laser to conductive material, photoetching, point-by-point vaporizing and removing conductive material to the surface of insulating material, and making closed insulation envelope channel around the conductive material to be retained. Then using photoetching laser to make slicing processing, according to the processing data including beam diameter, small piece separation line path and its correspondent laser parameter, projecting laser to conductive material, photoetching, point-by-point vaporizing and removing conductive material to the surface of insulating material, subdividing the large piece of conductive material to be removed into small pieces which are mutually heat-insulated. And finally, carrying out stripping processing by using heating laser, sequentially projecting laser to each small chip which is mutually insulated according to processing data comprising the diameter of a light beam, a heating line path for heating the small chip and corresponding laser parameters, heating the small chip to deform, reducing the bonding force between the small chip and the insulating material, separating the small chip and the insulating material under the combined action of auxiliary gas, separating the small chip from the insulating material, separating the small chip from the surface of the insulating material, transferring, collecting, and stripping and removing the small chip from the insulating material one by one.
Specifically, in this embodiment, a 20W infrared nanosecond laser is used to remove the copper foil on the non-wiring region to fabricate the conductive pattern. The conducting layer in the laser removing area is the original copper foil, the thickness is uniform, and the laser processing difficulty is greatly reduced. The processing parameters are as follows:
phases
power/W
frequency/kHz
Pulse width/ns
Processing speed/mm/s
Number of working operations
Remarks for note
Enveloping insulation
15
200
100
800
1
Focusing
Slitting and slicing
15
200
100
800
1
Focusing
Heat peeling off
30
200
100
900
1
Out of focus
(8) Attaching an RPP film to the surface of the workpiece;
specifically, the RPP film is laminated on the multilayer copper-clad plate with the manufactured conductive pattern in a hot-pressing laminating mode, and laminating parameters of the laminating machine are as follows: pressure 20kg/cm2, temperature 120 ℃ and speed 0.5 m/min.
(9) Removing the organic material layer on the surface of the welding area by laser to manufacture a solder resist pattern;
specifically, in this embodiment, a 20W ultraviolet nanosecond laser machine is used to fabricate the solder resist pattern, the circuit board is placed on a laser equipment adsorption table, engineering data of laser processing is imported, the circuit board and the processing data are aligned accurately, and the solder resist pattern is formed by laser photoetching. And after the top surface is processed, the circuit board is turned over, and the bottom surface solder resist pattern is manufactured by the same method. The processing parameters are as follows:
power/W
frequency/kHz
Pulse width/ns
Processing speed/mm/s
Number of working operations
8
200
20
700
1
(10) Adding solder to the connecting disc, carrying out component mounting and insertion, and carrying out remelting welding or wave soldering.
The circuit board can be continuously manufactured by the traditional method based on any step of the invention; in the steps of the invention, conventional circuit board processes, such as on-off inspection, such as printing of a label, may be inserted; double-sided, multi-layer, and various substrate materials may be suitable.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept, and these changes and modifications are all within the scope of the present invention.