阅读说明：本技术 采用湿膜保护pcb内层线路的开腔加工方法 (Cavity opening processing method for protecting PCB inner layer circuit by adopting wet film ) 是由 杜军 李明军 邓贤江 于 2019-08-27 设计创作，主要内容包括：一种采用湿膜保护PCB内层线路的开腔加工方法,其包括如下步骤：步骤一、在内层上制作内层线路；步骤二、在内层线路外表面覆盖湿膜层；步骤三、在湿膜层外侧形成一金属膜层；步骤四、在金属膜层外侧再覆上一铜层；步骤五、在铜层的外侧压外层及在外层外表面设置外侧铜层；步骤六、激光铣槽至保护层的铜层外侧面上,使保护层上的铜层露出；步骤七、采用蚀刻工艺,对外侧铜层进行蚀刻处理形成外层线路,同时将槽底部的铜层蚀刻掉；步骤八、将槽底的湿膜层退掉。本发明的开腔加工方法不仅可确保腔体内的清洁度,并可避免腔体内废料残留、线路沾金短路、流胶、填充不实、层间空洞的问题。本发明的实用性强,具有较强的推广意义。(A cavity opening processing method for protecting inner layer circuits of a PCB by adopting a wet film comprises the following steps: firstly, manufacturing an inner layer circuit on an inner layer; covering a wet film layer on the outer surface of the inner-layer circuit; step three, forming a metal film layer outside the wet film layer; step four, coating a copper layer on the outer side of the metal film layer; step five, pressing an outer layer on the outer side of the copper layer and arranging an outer copper layer on the outer surface of the outer layer; sixthly, milling a groove to the outer side face of the copper layer of the protective layer by laser to expose the copper layer on the protective layer; step seven, etching the outer copper layer by adopting an etching process to form an outer layer circuit, and etching the copper layer at the bottom of the groove; and step eight, removing the wet film layer at the bottom of the tank. The open cavity processing method can not only ensure the cleanliness in the cavity, but also avoid the problems of residual waste in the cavity, short circuit due to gold-stained circuits, gummosis, infirmity filling and interlayer cavities. The invention has strong practicability and stronger popularization significance.)

1. A cavity opening processing method for protecting PCB inner layer circuits by adopting a wet film is characterized by comprising the following steps: the PCB comprises an inner layer, an inner layer circuit, a protective layer, an outer layer and an outer layer circuit, wherein the inner layer circuit is arranged on the inner layer, the protective layer is arranged on the outer surface of the inner layer circuit, the outer layer covers the outer side surface of the protective layer, and the outer layer circuit is arranged on the outer surface of the outer layer; the PCB is provided with a cavity, and the cavity sequentially penetrates through the outer layer and the protective layer from the outer layer line to the inside and extends to the outer surface of the inner conductive line; the protective layer comprises a copper layer, a metal film layer and a wet film layer which are sequentially arranged from outside to inside;

the open cavity processing method for protecting the inner layer circuit of the PCB by adopting the wet film comprises the following steps:

step one, manufacturing an inner layer circuit; providing a substrate, wherein circuit layers are arranged on two outer side surfaces of the substrate, an inner layer connecting circuit connected with the circuit layers is arranged in the circuit layers, and a pre-opening cavity area is arranged on the outer surface of each circuit layer; the area of the pre-cavity-opening area is larger than the area of the bottom surface of the cavity;

step two, covering a wet film layer; covering a wet film layer outside the pre-cavity area on the outer surface of the inner-layer circuit;

metallization by a sputtering process; forming a metal film layer outside the wet film layer by a sputtering process;

coating copper, namely coating a copper layer on the outer side of the metal film layer;

step five, pressing an outer layer; pressing a prepreg on the outer side of the copper layer to form the outer layer, and arranging an outer copper layer on the outer surface of the outer layer;

step six, laser groove milling; adopting laser milling grooves on the outer surface of the outer copper layer corresponding to the pre-cavity-opening area to the outer side surface of the copper layer of the protective layer to expose the copper layer on the protective layer;

step seven, removing copper by etching; etching the outer copper layer by adopting an etching process to form an outer layer circuit, and etching the copper layer at the bottom of the groove;

step eight, dehumidifying the film; and removing the wet film layer at the bottom of the tank.

2. The open-cavity processing method for protecting the inner-layer circuit of the PCB by adopting the wet film as claimed in claim 1, characterized in that: the area of the pre-cavity-opening area is larger than the area of the bottom surface of the cavity, and the periphery of the protective layer extends between the outer layer and the circuit layer outside the cavity.

3. The open-cavity processing method for protecting the inner-layer circuit of the PCB by adopting the wet film as claimed in claim 1, characterized in that: the copper layer completely covers the outer side face of the metal film layer, and the outer layer completely covers the outer side face of the copper layer.

4. The open-cavity processing method for protecting the inner-layer circuit of the PCB by adopting the wet film as claimed in claim 1, characterized in that: in step 1, a sputtering copper process is required to metalize the gaps between the lines.

5. The open-cavity processing method for protecting the inner-layer circuit of the PCB by adopting the wet film as claimed in claim 1, characterized in that: in the sixth step, a copper window is firstly manufactured on the outer surface of the outer copper layer corresponding to the pre-cavity-opening area, and then a groove is milled by laser at the position of the copper window.

Technical Field

The invention relates to a circuit board processing method, in particular to an open cavity processing method for protecting a PCB inner layer circuit by adopting a wet film.

Background art:

some current PCBs have inner circuits, and PCBs outside of the inner circuits have cavities/blind slots. However, after the cavity of the conventional PCB is opened, the cleanliness in the cavity is low, and the glue or resin or other waste materials remain in the cavity and are not easy to fall off. And the cavity/blind slot is usually performed after the final surface treatment of the PCB; after ENIG (Electroless nickel plating and Immersion Gold) or ENEPIG (Electroless nickel plating and Immersion Gold), gaps between circuits in the cavity are prone to be stained with Gold, and short circuit is caused. In addition, some cavity opening methods include covering a cavity opening area with an adhesive sheet and opening the cavity. However, the method has the problems of flowing glue, infilling glue and interlayer voids, thereby causing poor reliability of the PCB.

The invention content is as follows:

therefore, the invention mainly aims to provide a cavity opening method for protecting an inner layer circuit of a PCB by adopting nickel or tin, so as to solve the problems of gold-stained short circuit of the inner layer circuit, difficult shedding of waste residues, gummosis, infirmity filling, interlayer cavities and poor reliability of the traditional circuit board cavity opening.

In order to achieve the purpose, the invention mainly adopts the following technical scheme:

a cavity opening processing method for protecting a PCB inner layer circuit by adopting a wet film is disclosed, wherein the PCB comprises an inner layer, an inner layer circuit, a protective layer, an outer layer and an outer layer circuit, the inner layer circuit is arranged on the inner layer, the protective layer is arranged on the outer surface of the inner layer circuit, the outer layer covers the outer side surface of the protective layer, and the outer layer circuit is arranged on the outer surface of the outer layer; the PCB is provided with a cavity, and the cavity sequentially penetrates through the outer layer and the protective layer from the outer layer line to the inside and extends to the outer surface of the inner conductive line; the protective layer comprises a copper layer, a metal film layer and a wet film layer which are sequentially arranged from outside to inside;

the open cavity processing method for protecting the inner layer circuit of the PCB by adopting the wet film comprises the following steps:

step one, manufacturing an inner layer circuit; providing a substrate, wherein circuit layers are arranged on two outer side surfaces of the substrate, an inner layer connecting circuit connected with the circuit layers is arranged in the circuit layers, and a pre-opening cavity area is arranged on the outer surface of each circuit layer; the area of the pre-cavity-opening area is larger than the area of the bottom surface of the cavity;

step two, covering a wet film layer; covering a wet film layer outside the pre-cavity area on the outer surface of the inner-layer circuit;

metallization by a sputtering process; forming a metal film layer outside the wet film layer by a sputtering process;

coating copper, namely coating a copper layer on the outer side of the metal film layer;

step five, pressing an outer layer; pressing a prepreg on the outer side of the copper layer to form the outer layer, and arranging an outer copper layer on the outer surface of the outer layer;

step six, laser groove milling; adopting laser milling grooves on the outer surface of the outer copper layer corresponding to the pre-cavity-opening area to the outer side surface of the copper layer of the protective layer to expose the copper layer on the protective layer;

step seven, removing copper by etching; etching the outer copper layer by adopting an etching process to form an outer layer circuit, and etching the copper layer at the bottom of the groove;

step eight, dehumidifying the film; and removing the wet film layer at the bottom of the tank.

Furthermore, the area of the pre-cavity-opening area is larger than the area of the bottom surface of the cavity, and the periphery of the protective layer extends between the outer layer outside the cavity and the circuit layer.

Furthermore, the copper layer completely covers the outer side face of the metal film layer, and the outer layer completely covers the outer side face of the copper layer.

Further, in step 1, a sputtering copper process is further used to perform metallization processing on the gap between the lines.

Further, in the sixth step, a copper window is firstly manufactured on the outer surface of the outer copper layer corresponding to the pre-cavity-opening area, and then a groove is milled at the position of the copper window by laser.

In summary, the wet film layer, the metal film layer and the copper layer are arranged at the pre-cavity-opening position to protect the inner circuit, and the periphery of the protection layer extends to a larger area than the bottom surface area of the actual cavity; then carrying out laser groove milling, copper layer removal and wet film layer removal; thereby can ensure the cleanliness in the cavity to can avoid in the cavity waste material remain, the circuit is stained with golden short circuit, gummosis, fill not real, the problem of interlayer cavity. The invention has strong practicability and stronger popularization significance.

Drawings

FIG. 1 is a schematic structural diagram of a PCB manufactured by the open-cavity processing method for protecting inner-layer circuits of the PCB by using a wet film according to the present invention;

FIG. 2 is a schematic flow chart of the cavity opening method of the present invention.

The specific implementation mode is as follows:

in order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.

As shown in fig. 1 and 2, the present invention provides a method for forming an open cavity for protecting inner circuits of a PCB using a wet film, which is used for forming an open cavity outside the inner circuits of the PCB. The PCB comprises an inner layer 10, an inner layer circuit 20, a protective layer 30, an outer layer 40 and an outer layer circuit 50, wherein the inner layer 10 is a conventional multilayer board, and the inner layer circuit 20 is arranged on the inner layer 10. The protective layer 30 is disposed on the outer surface of the inner layer circuit 20, the outer layer 40 covers the outer side surface of the protective layer 30, and the outer layer circuit 50 is disposed on the outer surface of the outer layer 40. The PCB is provided with a cavity 11, and the cavity 11 sequentially penetrates through the outer layer 40 and the protective layer 30 from the outer layer line 50 to the inside and extends to the outer surface of the inner conductive circuit 20. The protection layer 30 includes a copper layer 33, a metal film layer 32 and a wet film layer 31, which are sequentially disposed from outside to inside, and in this embodiment, the wet film layer 31 is made of ink. It is understood that the material of the wet film layer 31 is not limited to the ink material.

The open cavity processing method for protecting the inner layer circuit of the PCB by adopting the wet film specifically comprises the following steps:

step one, manufacturing an inner layer circuit; providing an inner layer 10, and manufacturing an inner layer circuit 20 on the inner layer 10, wherein the inner layer circuit 20 is displayed on the outer side surface of the inner layer 10; a pre-open cavity area 21 is arranged on the outer surface of the inner layer circuit 20; in this embodiment, the inner layer 10 of the PCB is a conventional multilayer board, and therefore, the detailed structure thereof is not described herein again; then, carrying out metallization treatment on the gaps of the inner layer circuit by adopting a copper sputtering process;

step two, the film layer 31 is covered with moisture; covering the wet film layer 31 outside the pre-cavity-opening area 21 on the outer surface of the inner layer circuit 20; wherein, the area of the pre-cavity-opening area 21 is larger than the bottom surface area of the cavity 11; the wet film layer 31 is designed to protect the inner layer circuit 20 and prevent the inner layer circuit 20 from being etched;

metallization by a sputtering process; forming a metal film layer 32 on the outer side of the wet film layer 31 by a sputtering process; the metal film layer 32 is designed to facilitate the formation of a copper layer 33;

coating copper, namely coating a copper layer 33 on the outer side of the metal film layer 32, wherein the area of the copper layer 33 is aligned with the wet film layer up and down; the copper layer 32 is designed to protect the inner layer circuit 20, and the processing is simple and convenient, so that the problems of glue flowing, incomplete glue filling and interlayer cavities can be avoided;

step five, pressing the outer layer 40; pressing prepreg on the outer side of the copper layer 33 to form the outer layer 40, wherein the outer layer 40 completely covers the protective layer 30; then, arranging an outer copper layer 51 on the outer surface of the outer layer 40;

step six, laser groove milling; manufacturing a copper window on the outer surface of the outer copper layer 51 corresponding to the pre-cavity area 21, and milling a groove on the outer side of the copper layer 32 of the protective layer 30 at the position of the copper window by using laser to form a groove body so as to expose the copper layer 33 on the protective layer 30; the area of the bottom surface of the groove body is smaller than the area of the copper layer 33;

step seven, removing copper by etching; etching the outer copper layer 51 by using an etching process to form an outer circuit 50, wherein the copper layer 32 at the bottom of the groove is etched away at the same time as the copper layer 33 of the protective layer 30 is exposed to the outside;

step eight, dehumidifying the film; the wet film layer at the bottom of the groove is removed, and the required cavity 11 is formed.

In summary, the wet film layer 31, the metal film layer 32 and the copper layer 33 are disposed at the pre-cavity-opening position to protect the inner circuit, and the periphery of the protection layer 30 extends to a volume larger than the bottom surface area of the actual cavity 11; then, carrying out laser groove milling, copper layer removing 33 and dehumidifying film layer 31; thereby, the cleanness in the cavity 11 can be ensured, and the problems of waste residue in the cavity 11, short circuit due to gold-stained circuit, gummosis, infirmity filling and interlayer cavities can be avoided. The invention has strong practicability and stronger popularization significance.

The above-mentioned embodiments only express one embodiment of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.