WO2023178851A1

WO2023178851A1 - Preparation method for pcb, and pcb

Info

Publication number: WO2023178851A1
Application number: PCT/CN2022/099823
Authority: WO
Inventors: 许碧辉; 杨海云; 何罗生; 张恒; 袁继旺
Original assignee: 生益电子股份有限公司
Priority date: 2022-03-25
Filing date: 2022-06-20
Publication date: 2023-09-28
Also published as: CN114666993A

Abstract

Disclosed in the present application is a preparation method for a PCB, and a PCB. The preparation method comprises: providing a PCB to be fabricated, the PCB to be fabricated being provided with a via hole that penetrates from the component side to the solder side; subjecting the component side and the solder side of the PCB to be fabricated to one-step etching to complete the fabrication of all outer-layer patterns; coating or attaching the opposite surfaces of a specific area of the PCB to be fabricated with a conductive material so as to form a conductive material layer, wherein the conductive material is a conductive fluid material or a conductive solid material containing an adhesive component; and subjecting the specific area to a gold plating treatment.

Description

PCB preparation method and PCB

This application claims priority to the Chinese patent application with application number 202210301149.8, which was submitted to the China Patent Office on March 25, 2022. The entire content of this application is incorporated into this application by reference.

Technical field

This application relates to the technical field of PCB (Printed Circuit Boards), for example, to a PCB preparation method and PCB.

Background technique

For testing of packaged semiconductor products, it is generally expected that the PCB used for testing (also called a test board) has a long service life, so the PCB used for testing is required to be processed with gold plating in the area corresponding to the packaged semiconductor product. For example, for the testing of BGA (Ball Grid Array Packaging) packaged products, it is often required that the area of the PCB used for testing corresponding to the BGA packaged product be processed with gold plating on all four sides.

In the related technology, there are two methods for gold plating specific areas on the PCB: (1). Using the traditional method of pulling leads for gold plating. However, the areas on the PCB corresponding to the packaged semiconductor products generally have a small spacing, and the PADs (i.e. pads) generally belong to multiple networks and are not connected to each other. Therefore, this method is often limited by too small spacing to process, or uneven current distribution due to uneven distribution of leads, which in turn leads to uneven thickness and appearance problems during gold plating; (2). Covering the backside of a specific area Copper and gold-plated, PAD can conduct through holes in specific areas and the current distribution is relatively uniform. However, this method requires etching patterns twice, which in turn requires 2 to 3 wet film and 5 dry film processes. The process flow is relatively complex, and the construction period and cost are affected.

Contents of the invention

The embodiments of the present application can solve at least one of the related technical problems. To this end, embodiments of the present application provide a PCB preparation method and PCB to shorten the PCB processing flow and reduce the problem of uneven current distribution.

An embodiment of one aspect of the present application provides a method for preparing a PCB. The preparation method includes:

Provide a PCB to be produced, the PCB to be produced having a via hole penetrating from the component surface to the welding surface;

On the component surface and the welding surface of the PCB to be produced, complete the production of all outer layer patterns in one etching;

Coating or attaching a conductive material on the opposite surface of the specific area of the PCB to be produced to form a conductive material layer, wherein the conductive material is a conductive fluid material or a conductive material containing an adhesive component solid materials; and

Gold plating is applied to said specific areas.

Optionally, the outer layer pattern includes a circuit pattern and a pad in the specific area.

Optionally, the specific area includes an area on the PCB corresponding to a BGA package product, and the pads in the specific area include BGA pads.

Optionally, the conductive material includes at least one of conductive glue, conductive ink, conductive paste, and conductive paint.

Optionally, the conductive material layer is a conductive adhesive layer, and the material of the conductive adhesive layer includes thermally peelable conductive adhesive.

Optionally, before performing gold plating on the specific area, the preparation method further includes: covering the conductive material layer with a wet film or a dry film to form an anti-electroplating layer.

Optionally, after performing gold plating on the specific area, the preparation method further includes: removing the anti-electroplating layer; and removing the conductive material layer.

Optionally, after removing the conductive material layer, the preparation method further includes: using an acetone organic solvent to clean the opposite surface of the specific area.

Optionally, the preparation method further includes: performing full-board copper plating on the PCB to be produced before completing the production of all outer layer patterns with one etching.

The technical solution of the PCB preparation method in the embodiment of the present application at least has the following beneficial effects: conductive material is coated or attached on the opposite surface of a specific area of the PCB to be produced, and the conductive material on the specific area of the PCB is All networks are electrically conductive, allowing gold plating to proceed. Such a preparation method can avoid the problem of uneven current distribution caused by the traditional method of gold plating by pulling leads. In addition, the preparation method in the embodiment of the present application etches the outer layer pattern of the PCB in one step, reducing the unnecessary increase in the process flow caused by etching the outer layer pattern twice (one of the traditional preparation methods is A copper sheet is placed on the back of a specific area of the PCB, and gold plating is performed through the conduction of via holes. However, this traditional method requires etching the outer layer pattern twice) and avoids the secondary alignment problem of the outer layer pattern.

An embodiment of another aspect of the present application provides a PCB. The PCB is made by the PCB preparation method described in any of the preceding technical solutions. Therefore, the PCB in the embodiment of the present application has the beneficial effects brought by the aforementioned preparation method, which will not be described again here.

Description of the drawings

Figure 1 is a schematic flow chart of a PCB preparation method in some embodiments of the present application;

Figure 2 is a schematic flow chart of a PCB preparation method in other embodiments of the present application;

Figure 3(a) to Figure 3(g) are product form schematic diagrams of important steps in an optional embodiment of the present application, wherein:

Figure 3(a) shows the PCB after full copper plating;

Figure 3(b) shows the PCB after etching the outer layer pattern;

Figure 3(c) shows the PCB after attaching conductive adhesive;

Figure 3(d) shows the PCB after the conductive adhesive layer is covered with dry film;

Figure 3(e) shows the PCB after gold plating on the area on the PCB corresponding to the BGA package product;

Figure 3(f) shows the PCB after the film has been removed;

Figure 3(g) shows the PCB after removing the conductive adhesive layer.

In the picture:

1-PCB; 10-component surface, 20-soldering surface; 30-via hole; 40-copper plating layer; 50-conductive adhesive layer; 60-dry film layer; 70-gold plating layer.

Detailed ways

The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application. The technical solutions in the various embodiments of the present application can be combined with each other based on what those of ordinary skill in the art can implement.

Terms like "first" or "second" used in this application are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of indicated technical features.

In order to meet the testing needs of semiconductor packaging products, the corresponding area of the PCB used for testing is usually required to have high oxidation resistance, wear resistance, conductivity, etc., so that the PCB used for testing (i.e., the test board) can be used multiple times. Thereby extending the service life of the PCB used for testing. To meet the requirements of oxidation resistance, wear resistance and conductivity, gold plating needs to be performed on the corresponding areas of the PCB. For example, the PCB used to test BGA packaged semiconductor products should be gold-plated in the area corresponding to the BGA pad.

An embodiment of one aspect of the present application provides a method for preparing a PCB. Referring to Figure 1, the preparation method includes:

Step S100: Provide a PCB to be produced. The PCB to be produced has a via hole penetrating from the component surface to the soldering surface. The back side of the component side is the soldering side.

Step S300: On the component surface and welding surface of the PCB to be produced, complete the production of all outer layer patterns by etching at one time;

Step S400: Coat or attach conductive material on the opposite surface of the specific area of the PCB to be produced to form a conductive material layer;

Step S600: Perform gold plating on the specific area.

As mentioned before, after integrated circuits or discrete components are installed on the PCB, related tests may be performed. The "specific area" in this application corresponds to the location of the test object on the PCB for subsequent testing. For example, when testing BGA-packaged integrated circuit products, the specific area refers to the area where the subsequent BGA-packaged integrated circuit products are installed on the PCB.

The meaning of "opposite surface" refers to the surface opposite to a certain surface. For example, if a BGA packaged integrated circuit product is installed on the component side of a PCB, the opposite surface refers to the soldering surface of the PCB.

Gold plating can be electroplated hard gold (i.e., electroplated alloy), for example, electroplated nickel gold can be used. It is understandable that electroplating soft gold can also be used depending on the situation (soft gold can be understood as pure gold).

The conductive material is a conductive fluid material or a conductive solid material containing a binder component. In traditional gold plating methods, the leads do not have an adhesive component. Compared with the method of using leads as conductive materials, the conductive materials in the embodiments of the present application have high line resolution and are suitable for finer lead spacing. Therefore, to a certain extent, it overcomes the problems caused by the traditional method of pulling leads for gold plating. The problem that the spacing is too small and cannot be processed.

The conductive material can be in fluid form or in solid form (such as conductive tape or other solid form). Depending on the conductive material, the conductive material can be coated or attached to form a conductive material layer. With the help of via holes that penetrate the PCB, the component surface of the PCB is connected to the conductive material layer on the soldering surface, so gold plating can be performed.

The outer layer pattern of the PCB is etched in one go, which reduces the unnecessary increase in the process flow caused by etching the outer layer pattern twice and avoids the problem of secondary alignment of the outer layer pattern. One of the traditional preparation methods is to set a copper sheet on the back of a specific area of the PCB and conduct gold plating with the help of via holes. However, this traditional method requires etching the outer layer pattern twice: (1). Perform the first Etch the pattern to form a pad in a specific area (such as a BGA pad); (2). With the help of the copper on the back of the specific area and the conduction of the via hole, for this specific area (such as the BGA pad position) Carry out gold plating; (3). Carry out the second etching pattern to form the circuit pattern of the PCB.

Conductive material is coated or attached on the opposite surface of a specific area of the PCB to be made, and the network on the specific area of the PCB is connected with the help of the conductive material layer and via holes, so that gold plating can be performed. Such a preparation method can avoid the problem of uneven current distribution caused by the traditional method of gold plating by pulling leads.

In some embodiments of the present application, the outer layer graphics include circuit graphics and pads in specific areas. "Circuit pattern" refers to the circuit connection pattern usually found on PCB. The pad is used to connect some specific components (such as integrated circuits in BGA packages), so the pad is the basic building block of surface mount assembly. "Specific area pads" are patterns on the PCB that are used to connect the basic building blocks of some specific components. In the embodiment of the present application, the above two patterns are completed in one etching process, which avoids the secondary alignment problem of etching the outer layer pattern twice and simplifies the PCB preparation process.

Optionally, in some embodiments of the present application, the specific component is a BGA package product, the specific area includes an area on the PCB corresponding to the BGA package product, and the pads in the specific area include BGA pads.

In some embodiments of the present application, the conductive material includes at least one of conductive glue, conductive ink, conductive paste, and conductive paint.

The conductive adhesive can be in the form of a fluid or a solid conductive tape, and the conductive adhesive contains an adhesive component. Conductive adhesive has certain conductive properties after curing or drying. It usually uses matrix resin and conductive filler (i.e. conductive particles) as its main components. The conductive particles are combined together through the bonding effect of the matrix resin to form a conductive path and realize the adhesive. Conductive connection of materials. The conductive filler can be a compound of elements such as gold, silver, copper, aluminum, iron, zinc or nickel, or graphite. The conductive paste in the embodiment of the present application includes conductive silver paste, which is also called silver conductive paste. Conductive silver paste can be divided into two categories: polymer silver conductive paste (dried or cured to form a film, organic polymerization material as the bonding phase) and sintered silver conductive paste (sintered to form a film, sintering temperature >500°C, glass powder or oxide as the bonding phase).

Conductive ink is an ink made of conductive materials. It has a certain degree of conductivity and can be used as printed conductive points or conductive lines. Conductive paste is based on mineral oil, synthetic lipid oil and silicone oil, and is added with conductive and anti-static properties. It is a soft paste made by grinding, dispersing and modifying special additives such as oxygen, anti-corrosion and arc suppression. Conductive paint includes conductive paint, which uses composite particles containing copper or silver as conductive particles. A paint with good electrical conductivity.

It can be understood that the conductive material may also be other types of conductive materials including conductive rubber, conductive resin, and the like.

Optionally, in some embodiments of the present application, the conductive material layer is a conductive adhesive layer, and the material of the conductive adhesive layer is thermally peelable conductive adhesive.

In addition to having the advantage of high line resolution, conductive adhesive does not contain lead and other toxic metals, making it an environmentally friendly adhesive. In addition, conductive adhesives can be connected at low temperatures and are especially suitable for interconnecting heat-sensitive components; conductive adhesives can be connected to different substrates, including interconnections on ceramics, glass and other non-solderable surfaces. Conductive adhesive also has good flexibility and fatigue resistance.

Thermal peelable conductive adhesive reduces or even loses its viscosity under heating, so it is easy to peel off and can achieve little or no residual glue.

Please refer to Figure 2. In some embodiments of the present application, before performing gold plating on the specific area, the preparation method further includes: Step S500: Cover the conductive material layer with a wet film or a dry film to form an anti-electroplating layer. .

Most wet films are photosensitive inks, which are photosensitive inks that are sensitive to violet rays and can be cured by ultraviolet rays. Dry film is a polymer material that can produce a polymerization reaction after being irradiated with ultraviolet rays to form a stable substance that adheres to the board surface, thereby blocking electroplating and etching. Both wet film and dry film have the function of blocking electroplating. Put the wet film or dry film on the conductive material layer to seal the via holes on the PCB to be made. It also has a protective effect on the conductive material layer, so that when gold plating is performed on a specific area, the opposite surface of the specific area (i.e., with The opposite surface) is also plated. For example, if the BGA pad area on the component surface is gold-plated, the soldering surface will not be plated.

The operation of covering the dry film is to press the dry film, such as peeling off the polyethylene protective film from the dry film, and pasting the dry film resist on the PCB to be produced under heating and pressure conditions. The method of covering the wet film is to apply the wet film, such as by roller coating, spray coating, dip coating or screen printing.

Please continue to refer to Figure 2. In some embodiments of the present application, after performing gold plating on the specific area, the preparation method further includes: step S700: removing the anti-electroplating layer; and step S800: removing the conductive material layer, thereby Remove materials that are necessary for the intermediate process but are not part of the final form of the PCB.

Optionally, removing the anti-electroplating layer is film stripping. To remove the film, sodium hydroxide solution can be used to remove the anti-electroplating film layer so that the non-circuit copper layer can be exposed. Removing the conductive material layer may be, for example, tearing off the conductive adhesive layer.

Optionally, in some embodiments of the present application, in order to reduce or avoid residue after removing the conductive material layer, the preparation method further includes: using an acetone organic solvent to clean the opposite surface of a specific area after removing the conductive material layer. Acetone organic solvent has a better cleaning effect on most resin materials, especially in removing possible residual conductive adhesive.

Please continue to refer to Figure 2. In some embodiments of the present application, before completing the production of all outer layer patterns in one etching, the preparation method further includes: step S100: performing full-board copper plating on the PCB to be produced. Electroplated copper is deposited on the surface of the PCB to be produced to form a uniform, dense and well-bonded electroplated copper layer to protect the previously deposited chemical copper on the surface of the PCB to be produced.

Another embodiment of the present application also provides a PCB, which is made by the preparation method of any of the foregoing embodiments.

In order to facilitate understanding of the technical solution of the present application, the following text describes an optional embodiment of the present application in conjunction with Figures 3(a) to 3(g) - that is, making a PCB, which is used to test BGA packaged semiconductor products. This PCB is required to be gold plated in specific areas on the PCB corresponding to the mounting position of BGA packaged semiconductor products.

As shown in FIG. 3(a) , the PCB 1 to be produced is fully plated with copper (also called plate electroplating), so that electroplated copper is deposited on the surface of the PCB 1 to be produced, forming a copper plating layer 40 . Figure 3(a) also shows that the PCB 1 to be produced has a via hole 30, which penetrates from the component surface 10 to the soldering surface 20. In the direction shown in Figure 3(a), the component surface 10 is located on the upper surface of PCB1, and the soldering surface 20 is located on the lower surface of PCB1. After the entire board is copper-plated, a copper plating layer 40 is deposited on both the component surface 10 and the welding surface 20 .

As shown in Figure 3(b), on the component surface 10 and the welding surface 20 of the PCB 1 to be produced, all outer layer patterns are produced by etching in one go. All outer layer graphics include the conventional circuit graphics of PCB and the pad graphics of BGA.

As shown in Figure 3(c), on the back side of the designed position of the BGA pad on the PCB1 to be produced (the designed position of the BGA pad is located on the component surface 10, the back side of the designed position of the BGA pad corresponds to the soldering surface 20 A conductive adhesive is attached to the designed position of the BGA pad to form a conductive adhesive layer 50 . In Figure 3(c), the pattern left after one etching on the component surface 10 includes BGA pads.

As shown in Figure 3(d), a dry film is covered on the conductive adhesive layer 50 to form an anti-electroplating layer, that is, a dry film layer 60. The dry film layer 60 blocks and seals the via hole 30 and protects the conductive adhesive layer 50 .

As shown in FIG. 3(e) , gold plating is performed on the designed position of the BGA pad on the component surface 10 to form a gold plating layer 70 .

As shown in Figure 3(f), the dry film layer 60 is subjected to film removal processing;

As shown in Figure 3(g), the conductive adhesive layer 50 is removed without leaving as much adhesive residue as possible. At this point, the production of PCB1 in the embodiment of this application is completed.

Claims

A method for preparing PCB, including:

Provide a PCB to be produced, the PCB to be produced having a via hole penetrating from the component surface to the welding surface;

On the component surface and the welding surface of the PCB to be produced, complete the production of all outer layer patterns in one etching;

Coating or attaching a conductive material on the opposite surface of the specific area of the PCB to be produced to form a conductive material layer, wherein the conductive material is a conductive fluid material or a conductive material containing an adhesive component solid materials; and

Gold plating is applied to said specific areas.
A PCB preparation method according to claim 1, wherein the outer layer pattern includes a circuit pattern and a pad in the specific area.
A PCB preparation method according to claim 2, wherein the specific area includes an area on the PCB corresponding to a BGA package product, and the pads in the specific area include BGA pads.
A PCB preparation method according to claim 1, wherein the conductive material includes at least one of conductive glue, conductive ink, conductive paste and conductive paint.
A PCB preparation method according to claim 4, wherein the conductive material layer is a conductive adhesive layer, and the material of the conductive adhesive layer includes thermally peelable conductive adhesive.
A PCB preparation method according to claim 1, before performing gold plating on the specific area, the preparation method further includes: covering the conductive material layer with a wet film or a dry film to form an anti-electroplating layer. .
A PCB preparation method according to claim 6, after performing gold plating on the specific area, the preparation method further includes:

Remove the anti-electroplating layer;

The layer of conductive material is removed.
A PCB preparation method according to claim 7, after removing the conductive material layer, the preparation method further includes:

Use an organic solvent called acetone to clean the opposing surfaces of the specific area.
A PCB preparation method according to claim 1, before the preparation of all outer layer patterns is completed by etching at one time, the preparation method further includes:

Perform full board copper plating on the PCB to be produced.
A PCB made by the PCB preparation method described in any one of claims 1 to 9.