阅读说明：本技术 引线框架、引线框架单面侧面棕化工艺及半导体封装体 (Lead frame, single-side surface browning process of lead frame and semiconductor package ) 是由 黎超丰 冯小龙 章新立 林杰 林渊杰 林海见 罗壮 于 2020-08-19 设计创作，主要内容包括：本发明公开了引线框架,属于集成电路封装领域,它包括设有半蚀刻区的基材,且基材单侧表面上以及半蚀刻区侧壁设有棕色氧化层,所述基材上表面设有电镀层,电镀层位于棕色氧化层表面；本发明提供一种引线框架单面侧面棕色氧化工艺及半导体封装体,应用于12*12毫米以及更大尺寸的引线框架,在保证引线框架可靠性的前提下,针对引线框架单面以及内蚀刻区域的侧壁进行棕色氧化处理,相对于引线框架整体做棕色氧化的棕色氧化成本,节省10％-30％。(The invention discloses a lead frame, belonging to the field of integrated circuit packaging, comprising a substrate provided with a half-etching area, wherein the surface of one side of the substrate and the side wall of the half-etching area are provided with brown oxide layers; the invention provides a single-side brown oxidation process of a lead frame and a semiconductor packaging body, which are applied to lead frames with the sizes of 12-12 mm and larger, brown oxidation treatment is carried out on the single side of the lead frame and the side wall of an internal etching area on the premise of ensuring the reliability of the lead frame, and compared with the brown oxidation cost of brown oxidation of the whole lead frame, the brown oxidation cost is saved by 10-30%.)

1. Lead frame, its characterized in that: the electroplating layer is arranged on the upper surface of the substrate and is positioned on the surface of the brown oxidation layer.

2. The lead frame of claim 2, wherein: the substrate size is 12 x 12 mm and above.

3. The single-side surface browning process of the lead frame is characterized in that: the method comprises the following steps:

s1, cleaning, removing fatty oil stains and other organic dirt on the surface of the base material, and drying;

s2, performing single-side brown oxidation, and performing brown oxidation on one surface of the base material;

s3, electroplating, wherein the brown oxidized surface of the base material is electroplated;

s4, etching, namely etching the base material to form a half-etched area;

s5, performing brown oxidation for the second time, removing the film, cleaning and drying the half-etched area after performing brown oxidation treatment;

and S6, sticking the tape first, and then checking and putting the tape into a finished product warehouse.

4. The single-sided side browning process for lead frames according to claim 3, wherein: before the brown oxidation in step S2, a dry film is attached to one surface of the substrate, a PET film is left on the surface of the dry film, and the other surface of the substrate is a surface to be subjected to brown oxidation treatment.

5. The single-sided side browning process for lead frames according to claim 4, wherein: the plating process in step S3, comprising the steps of: firstly, a dry film is pasted on the brown oxidation surface of the base material, then exposure and development treatment are carried out, after the area to be electroplated is exposed, electroplating treatment is carried out on the area to be electroplated, and after electroplating is finished, the surface of the base material is cleaned and dried.

6. The single-sided side browning process for lead frames according to claim 3, wherein: the etching process in step S4, comprising the steps of: the method comprises the steps of firstly removing a film from a base material, then pasting a dry film on the surface of the base material, then sequentially carrying out secondary exposure and secondary development treatment, carrying out etching treatment on an area to be etched after the area to be etched is exposed, cleaning the surface of the base material after etching is finished, and drying.

7. The single-sided side browning process for lead frames according to claim 3, wherein: the secondary brown oxidation process in step S5, comprising the steps of: firstly, the surface of the side wall of the half-etching area is subjected to microscopic activation, then the side wall of the half-etching area is subjected to brown oxidation to form a brown oxidation layer, then a dry film is removed, and the dry film is cleaned and dried.

8. The single-sided side browning process for lead frames according to claim 3, wherein: the cross section of the half-etched area is in a convex shape or an inverted convex shape.

9. The single-sided side browning process for lead frames according to claim 3, wherein: in steps S1-S5, the substrate is a web.

10. A semiconductor package characterized by: -subjecting the finished lead frame as claimed in any of claims 3 to 9 to an encapsulation process.

11. The semiconductor package of claim 10, wherein: the packaging process adopts QFN packaging.

Technical Field

The invention relates to the field of integrated circuit packaging, in particular to a lead frame, a single-side surface browning process of the lead frame and a semiconductor packaging body.

Background

QFN, one of the surface mount packages, is now commonly referred to as LCC. Electrode contacts are arranged on four sides of the package, and due to the fact that pins are not arranged, the mounting occupied area is smaller than that of the QFP, and the height of the package is lower than that of the QFP. However, when stress is generated between the printed substrate and the package, the stress cannot be relieved at the electrode contact. Therefore, the electrode contact is difficult to be made as many as the pins of the QFP, and is generally about 14 to 100.

Taking the example of processing a lead frame with 12 × 12 mm, the lead frame needs to achieve secondary reliability, namely, the MSL2 level, only the front surface of the lead frame is subjected to brown oxidation treatment or only the side wall of the half-etched area of the lead frame is subjected to brown oxidation treatment, and the reliability requirement is difficult to guarantee. In the prior art, a lead frame with a size of 12 × 12 mm and larger is subjected to brown oxidation treatment on the whole lead frame, so that in the subsequent injection molding process, the condition of plastic package material overflow is difficult to avoid, after the plastic package material is tightly combined with a brown oxidation layer on the back of the lead frame, the plastic package material is difficult to remove through a common cleaning process, and a high-pressure water washing or polishing procedure is additionally required, so that the integrity of a semiconductor package body is influenced.

Aiming at the problems, the invention provides the structure without the brown oxide layer on the back surface of the lead frame, and on the premise of ensuring the reliability of the lead frame, the brown oxidation treatment is carried out on the single surface of the lead frame and the side wall of the inner etching area, so that compared with the brown oxidation cost for carrying out brown oxidation on the whole lead frame, the brown oxidation cost is saved by 10% -30%.

Disclosure of Invention

The technical scheme adopted by the invention is as follows: providing a lead frame, which comprises a substrate provided with a half-etching area, wherein brown oxide layers are arranged on the surface of one side of the substrate and the side wall of the half-etching area, and an electroplated layer is arranged on the upper surface of the substrate and is positioned on the surface of the brown oxide layer.

By adopting the structure, in the subsequent packaging process of the lead frame, the connecting surface of the packaging body and the lead frame is the front surface of the base material and the side wall of the half-etched area, so that the contact area with the packaging body is increased, the adhesiveness with the packaging body is improved, and the delamination is prevented; and the electroplated layer is positioned on the surface of the brown oxide layer, the compactness of the surface of the electroplated area is good, no material veins are generated, the deposited silver has good consistency, and the particles are uniform.

The substrate size is 12 x 12 mm and above; the lead frame with the size can achieve secondary reliability after being packaged.

The single-side surface browning process for the lead frame comprises the following steps:

s1, cleaning, removing fatty oil stains and other organic dirt on the surface of the base material, and drying;

s2, performing single-side brown oxidation, and performing brown oxidation on one surface of the base material;

s3, electroplating, wherein the brown oxidized surface of the base material is electroplated;

s4, etching, namely etching the base material to form a half-etched area;

s5, performing brown oxidation for the second time, removing the film, cleaning and drying the half-etched area after performing brown oxidation treatment;

and S6, sticking the tape first, and then checking and putting the tape into a finished product warehouse.

After the technical scheme is adopted, the invention achieves the beneficial effects that:

1. the area to be electroplated is a brown oxidized surface, the surface activity of the brown oxidized surface is high, and acid pickling and activating treatment are not needed before electroplating, so that the electroplating process flow is simplified, and the resource utilization rate is improved; 2. after brown oxidation treatment, the surface is used to obtain a micro-uneven surface shape, so that the contact surface area of copper and the plastic packaging material is increased, the wettability between the copper surface and the plastic packaging material is increased, the adhesion with the plastic packaging material is improved, and delamination is prevented; 3. the brown oxidation step is positioned before the electroplating step, no brown stain is generated on the electroplated silver surface, and the cleaning step after silver plating is simplified; 4. the secondary brown oxidation process is used for carrying out the etching process, alkali washing treatment is not needed before the secondary brown oxidation process, and subsequent treatment such as activation, browning and the like is directly carried out, so that the secondary brown oxidation process is simplified, and the cost is saved.

Preferably, before the brown oxidation in step S2, a dry film is attached to one surface of the substrate, a PET film is left on the surface of the dry film, and the other surface of the substrate is a surface to be subjected to brown oxidation treatment; the dry film is generally classified into three layers, one layer is a PE protective film, the middle layer is a dry film layer, the other layer is a PET protective film, the middle layer of the dry film really plays a role, and the dry film has certain viscosity and good photosensitivity; before brown oxidation, the PE protective film is directly torn off, the exposed dry film layer is directly adhered to the base material, and the PET protective film on the other side is reserved.

Preferably, the plating process in step S3 includes the steps of: firstly, a dry film is pasted on the brown oxidation surface of the base material, then exposure and development treatment are carried out, after the area to be electroplated is exposed, electroplating treatment is carried out on the area to be electroplated, and after electroplating is finished, the surface of the base material is cleaned and dried.

Preferably, in the electroplating step of step S3, the dry film on the brown oxidized surface of the substrate is an electroplated dry film; after the UV reaction, the electroplated dry film that undergoes the optical reaction on the surface of the substrate is corroded by the alkali during the electroplating process.

Preferably, the etching process in step S4 includes the steps of: the method comprises the steps of firstly removing a film from a base material, then pasting a dry film on the surface of the base material, then sequentially carrying out secondary exposure and secondary development treatment, carrying out etching treatment on an area to be etched after the area to be etched is exposed, cleaning the surface of the base material after etching is finished, and drying.

Preferably, the secondary brown oxidation process in step S5 includes the steps of: firstly, the surface of the side wall of the half-etching area is subjected to microscopic activation, then the side wall of the half-etching area is subjected to brown oxidation to form a brown oxidation layer, then a dry film is removed, and the dry film is cleaned and dried.

Preferably, the cross section of the half-etched region is convex or inverted convex.

Preferably, in steps S1-S5, the substrate is a roll; the roll-type base material can be continuously operated, and the production efficiency is high.

And the semiconductor packaging body is used for packaging any one of the lead frame finished products.

Preferably, the packaging process adopts QFN packaging; the QFN package has small volume, thin thickness and light weight, and is suitable for high-density printed circuit boards of portable small electronic equipment.

The beneficial effects of the invention include:

1. in the invention, only the front side of the base material is subjected to brown oxidation treatment, so that the bonding force between the flash on the back side of the base material and the base material is small, the cleaning difficulty of the flash is small, and the influence on the bonding between the front side and the side surface of the base material and the plastic package material in the cleaning process is reduced.

2. Compared with the prior art that the whole lead frame is subjected to brown oxidation, the brown oxidation area of the back surface of the lead frame is reduced, less brown oxidation liquid is consumed, and the aging rate of the brown oxidation liquid is reduced; in single-side brown oxidation, because the binding force between the PET film and the brown oxidation liquid is small, the brown oxidation liquid carried out by the substrate on the side is less, the utilization rate of the brown oxidation liquid is improved, and the brown oxidation cost is saved.

3. In the steps S1-S5, the roll-type substrate is adopted, the integrity of the substrate is high, the efficiency and yield of brown oxidation are improved, and for example, when a 12 × 12 mm lead frame is prepared, on the premise that the lead frame at least achieves secondary reliability, the cost of the roll-type single-side brown oxidation is reduced by 10% -30% compared with the cost of the sheet-type integral brown oxidation.

4. The single-side brown oxidation procedure is arranged before the electroplating procedure, so that the steps of the electroplating procedure are simplified; the etching process is positioned before the secondary brown oxidation process, so that the steps of the brown oxidation process are simplified, and compared with the traditional method for performing brown oxidation treatment on the whole lead frame, the dry film use cost is increased; compared with the simple combination of the single-side browning and the side browning, the invention simplifies the process steps and reduces the unnecessary consumption of the liquid medicine.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

The reference numbers in the figures illustrate:

wherein 1, a substrate; 2. a brown oxide layer; 3. a half-etched region; 4. and (4) electroplating.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Dry films are generally classified into three layers, one layer being a PE protective film, the middle layer being a dry film layer, and the other layer being a PET protective film. What really works is the middle dry film, which has certain viscosity and good photosensitivity. In the specification, the dry films are divided into an electroplating dry film and an etching dry film according to different functions, and a PET film adhered to the surface of the dry film is acid-resistant and alkali-resistant.

In the specification, the base material is made of copper alloy, and gold, silver, nickel and palladium can be electroplated on the copper surface of the base material.

Example 1

A lead frame is shown in figure 1, a convex half etching area 3 is arranged on a base material 1, a brown oxidation layer 2 is arranged on the upper surface of the base material 1 and the side edge of the half etching area 3, an electroplating layer 4 is electroplated on the electroplating surface of a bonding area of the base material 1, the electroplating layer 4 is arranged on the brown oxidation layer 2, and the electroplating layer 4, the brown oxidation layer 2 and the base material 1 are arranged in sequence from top to bottom in the bonding area.

In some examples, the lead frame is 12 x 12 millimeters in size.

Example 2

Providing a single-side brown oxidation process of a lead frame, providing a rolled base material, wherein the base material adopts a copper alloy with pure copper accounting for more than 97 percent, and the method comprises the following steps:

s1, cleaning, also called as pre-cleaning, wherein the cleaning step comprises degreasing and drying procedures, the degreasing temperature is 55 ℃, the positive and negative difference of the temperature is within 5 ℃, the degreasing spraying pressure is 5-25psi, preferably 15psi, and after the degreasing is finished, the base material is dried;

s2, carrying out single-side brown oxidation, carrying the cleaned substrate in the previous step, firstly, attaching a dry film to the back of the target brown oxidation surface on the substrate, wherein the dry film is electroplated, a PET (polyethylene terephthalate) film is reserved on the surface of the dry film, the back of the target brown oxidation surface is used as the back of a lead frame, the target brown oxidation surface on the substrate is used as the front of the lead frame, the roller temperature of a film drying machine is 100 ℃, the up-down floating temperature difference is 20 ℃, and the speed of the roller is 2 m/min;

carrying the base material with the dry film pasted in the last step, and carrying out brown oxidation treatment on the first surface, wherein the brown oxidation treatment comprises alkali washing, acid washing, ALK cleaning, activation, brown oxidation, cleaning procedure after the brown oxidation, mountain angstrom titration, potassium hydroxide titration, hot water washing procedure and drying, and the mountain angstrom is dripped to remove brown oxidation powder; in the alkali washing process, the alkali temperature is 60 ℃, the fluctuation of 5 ℃ up and down is allowed, the alkali concentration is 40g/L, in some examples, the alkali concentration is 60g/L, and the pretreatment speed of the alkali washing is 50 +/-10 HZ; in the acid washing process, the acid concentration is 30-50 g/L, 45g/L is adopted in the embodiment, the concentration of copper ions needs to be less than 10g/L, and the speed of an acid cylinder is 15 +/-10 HZ; the ALK cleaning concentration is 100-150 ml/L; the activation concentration is 15-25 ml/L, the activation temperature is 35 ℃, and fluctuation of up and down 5 ℃ is allowed; the MoldPrep series of Anmett chemical company Limited is adopted as the brown oxidation liquid, the brown oxidation steps and methods are all the prior art, and in some examples, the patent document CN108389803B is described in detail; the temperature of cleaning after brown oxidation is 40 ℃, the fluctuation of the temperature of 5 ℃ from top to bottom is allowed, and the concentration of the cleaning solution is 120-180 ml/L; the concentration of the dropwise adding Erianthus lineare is 3-8 g/L; dropwise adding potassium hydroxide with the concentration of 8-18 g/L; the temperature of hot water washing is 60 ℃, and fluctuation of the temperature of up and down 5 ℃ is allowed; the drying adopts a dry-slice furnace for drying, the drying temperature is 140 ℃, the fluctuation of the temperature of up and down 5 ℃ is allowed, and the drying speed is 15 +/-5 HZ.

S3, electroplating, receiving the substrate after single-side brown oxidation in the previous step, pasting a 40-micron-thick electroplating dry film on the brown oxidation surface, sequentially carrying out exposure treatment and development treatment on the surface, removing the electroplating on the surface of the region to be electroplated shown after the development treatmentAfter the film is dried, exposing the area to be electroplated on the lead frame, and washing and drying the developed substrate; in the exposure process, the light measurement is 40-60mj/cm²Preferably, the light measurement is 50mj/cm 2; in the developing process, the developing pressure is 5-25PSI, and the water washing pressure after developing is 5-15 PSI;

carrying the exposed and developed substrate in the previous step, carrying out electro-silvering treatment on the exposed part of the to-be-electro-silvered surface of the substrate, wherein in the process of silvering, the back surface of the substrate is protected by a dry film with a PET film, other areas on the front surface of the substrate are protected by the electro-silvered dry film, replacement reaction cannot be generated between plated parts in other areas and silvering solution, and after the silvering is finished, only drying treatment is carried out on the substrate; wherein, in the exposure process, the vacuum degree required by exposure is less than-650 KPa; in the developing process, the swinging speed of the developing is 40 +/-10 HZ, and the pH value is 10-12; in the silver plating process, the pH value in the silver plating cylinder is 8-9, the silver concentration is 30-50 g/L, and the KCN concentration is 0-2 g/L; the drying after the silver plating is finished is carried out through oven treatment, so that the base material frame is not easy to oxidize, the drying temperature is 90 ℃, and the fluctuation of 20 ℃ is allowed;

s4, etching, wherein the substrate after being treated by the electrosilvering in the previous step is received, dry films on two sides of the substrate are replaced, the replacement content comprises removing a film stripping and attaching an etching dry film, wherein the film stripping comprises alkali washing, acid washing, water washing and drying treatment, the treated substrate is subjected to secondary upper etching dry film by an upper film drying machine, and the etching dry film completely covers the front side and the back side of the substrate;

carrying the substrate subjected to the secondary dry film coating treatment in the previous step, exposing, developing and etching the substrate, the light intensity of the exposure being 40-60mj/cm²In the embodiment, 60mj/cm is preferred, in the developing process, the conveying speed of the base material is 1-2.5m/min, 1.5m/min is preferred in the embodiment, the developing pressure is 15PSI, after the developing, the upper dry film on the electroplating surface presents the design lines of the lead frame, the subsequent etching part carries out etching treatment on the base material exposed outside, the etching part on the base material is a half-etching area, and the cross section of the half-etching area is in a convex structure;

in the etching process, the concentration of hydrochloric acid is 0.65-0.75 mol/L, the etching temperature is 50 ℃, the fluctuation of the temperature of the upper and lower parts is allowed to be 5 ℃, the transmission speed is 500-3500 mm/min, and 2000mm/min is adopted in the embodiment;

s5, carrying out brown oxidation for the second time, keeping the electroplated dry film left in the etching process on two sides of the substrate after etching in the previous step, and carrying out brown oxidation treatment on the side wall of the half-etched area, wherein the brown oxidation treatment comprises activation, brown oxidation, a cleaning process after the brown oxidation, film stripping, cleaning and drying, the activation concentration is 15-25 ml/L, the activation temperature is 35 ℃, and fluctuation of the temperature of up and down 5 ℃ is allowed; the MoldPrep series of Anmett chemical company Limited is adopted as the brown oxidation liquid, the brown oxidation steps and methods are all the prior art, and in some examples, the patent document CN108389803B is described in detail; the temperature of cleaning after brown oxidation is 40 ℃, the fluctuation of the temperature of 5 ℃ from top to bottom is allowed, and the concentration of the cleaning solution is 120-180 ml/L; the temperature of cleaning is 60 ℃, and fluctuation of 5 ℃ is allowed; the drying adopts a dry-slice furnace for drying, the drying temperature is 140 ℃, the fluctuation of the temperature of up and down 5 ℃ is allowed, and the drying speed is 15 +/-5 HZ.

And S6, firstly pasting the tape, carrying the substrate in the previous step, and carrying out post-processing on the substrate to obtain the finished lead frame, wherein the post-processing comprises tape pasting and forming, and the tape pasting, forming and inspection contents are all in the prior art and are not described in detail.

Example 3

The present embodiment is different from embodiment 1 in that the substrate in the present embodiment adopts a plate type structure, and the adjustment of the substrate in the plate type structure is performed in an exposure and development step including two processes in the processing steps, compared with a roll type substrate. During the exposure, the light measurement was 100mj/cm²(ii) a In the developing link, the pressure is 5-20 PSI, and the preferred pressure is 20 PSI.

Example 4

In the step S1, the degreasing step is to clean the oxidation-resistant oil layer on the surface of the copper coil to prevent oxidation, and remove the oxide and the foreign matters on the substrate to protect the subsequent dry film applying process from deformation caused by the foreign matters to affect the quality of brown oxidation; the difference from the embodiment 2 is that after the alkali cleaning, the rough surface is generated on the substrate by acid micro-etching the substrate, so that the subsequent dry film and the copper surface are more tightly pressed without stripping.

Example 5

In this embodiment, the finished product described in any of embodiments 2 to 4 is applied, and after tape attaching and molding are performed on the finished product, a lead frame is obtained, and the lead frame is applied to an IC package, where the technical content of the IC package is the prior art, and thus, details are not repeated.

In some examples, the IC package uses QFN technology, and a large-area exposed bonding pad is exposed on the bottom surface of the packaged lead frame, and the periphery of the package surrounding the large bonding pad is provided with I/O pins. In the process of packaging by the QFN technology, when plastic package materials are injected, flash is inevitably generated to be adhered to the bottom of a lead frame, the subsequent tinning process is influenced by the flash, and the back of the lead frame is free of a brown oxide layer and is cleaned normally subsequently.

The foregoing has described preferred embodiments of the present invention and is not to be construed as limiting the claims. The present invention is not limited to the above embodiments, and the specific structure thereof is allowed to vary, and various changes made within the scope of the independent claims of the present invention are within the scope of the present invention.