A processing method of a gold finger on a circuit board and the circuit board

Abstract

This invention belongs to the field of circuit board technology, and specifically relates to a method for processing gold fingers on a circuit board and the circuit board itself. The method for processing gold fingers on a circuit board includes: preparing a circuit board body; wherein the surface of the circuit board body has an area to be gold-plated, a copper layer for fingers is processed in the area to be gold-plated, and metallized holes are processed at the edges of the area to be gold-plated; plugging the metallized holes at the edges of the area to be gold-plated with photosensitive resist; printing photosensitive resist on the entire surface of the circuit board body, baking and curing to form a photosensitive protective film; exposing and developing the photosensitive protective film to expose the area to be gold-plated; gold-plating the copper layer for fingers within the area to be gold-plated to form gold fingers; and removing the resist using a degreasing agent, thus removing the photosensitive protective film and the photosensitive resist within the metallized holes. This method abandons the conventional method of protecting metallized holes with dry film, instead using photosensitive resist to plug the holes, and then removing the resist using a degreasing agent after gold plating.

Description

Technical Field

[0001] This invention belongs to the field of circuit board technology, and in particular relates to a method for processing gold fingers on a circuit board and the circuit board itself. Background Technology

[0002] Some circuit boards have gold fingers on their edges, and metallized holes are located near the gold fingers. The customer has explicitly requested that gold plating not be allowed inside the metallized holes to ensure the conductivity of the metallized holes and the reliability of the product, and to avoid the gold plating layer affecting the conductivity of the copper layer inside the metallized holes or causing subsequent assembly defects.

[0003] The conventional gold finger processing technology is as follows: dry film is used to protect the metallized holes. Specifically, the dry film is applied to completely cover the metallized holes near the gold finger, exposing the area to be processed. Then, the gold finger is gold plated. After the gold plating is completed, the dry film is removed, thus achieving the requirement that the metallized holes are not gold plated.

[0004] However, dry film materials are expensive, and the processes of applying dry film, positioning, and exposure are complex and time-consuming, resulting in high overall processing costs. Moreover, problems such as air bubbles and misalignment are prone to occur during the dry film bonding process, which can lead to poor gold plating inside the metallized holes due to inadequate protection, thus reducing the pass rate of circuit board processing.

[0005] Therefore, there is a need for a gold finger processing technology that is low-cost, simple to operate, and has a high circuit board yield rate. Summary of the Invention

[0006] This invention provides a low-cost, simple-to-operate method for processing gold fingers on a circuit board and a circuit board with a high yield rate.

[0007] To solve the above-mentioned technical problems, on the one hand, the present invention provides a method for processing gold fingers on a circuit board, comprising: A circuit board body is prepared; wherein the surface of the circuit board body has a gold-plated area, the gold-plated area is processed with a finger copper layer, and the edge of the gold-plated area is processed with metallized holes. Photosensitive resist coating is used to plug the metallized holes at the edge of the area to be gold plated, and photosensitive resist coating is printed on the entire surface of the circuit board body, baked and cured to form a photosensitive protective film. The photosensitive protective film is exposed and developed to reveal the area to be gold-plated. The copper layer of the finger in the area to be gold-plated is gold-plated to form a gold finger; The oil is removed by using an oil remover, and the photosensitive protective film and the photosensitive anti-plating oil in the metallized holes are removed.

[0008] Optionally, when using photosensitive resist to plug the metallized holes at the edge of the area to be plated with gold, the photosensitive resist overflows from the opening of the metallized hole to the periphery by 0.1~0.3mm.

[0009] Optionally, the metallization holes at the edge of the area to be gold-plated can be plugged using screen printing or adhesive dispensing.

[0010] Optionally, the baking and curing process specifically includes: First, pre-bake at a low temperature, with a baking temperature of 70℃~75℃ and a baking time of 30~60 minutes; Then, bake at a high temperature of 100℃~120℃ for 25~35 minutes.

[0011] Optionally, the use of an oil-removing agent for oil removal specifically includes: Organic degreasing agent is used to remove photosensitive anti-plating oil. The degreasing temperature is 40℃~60℃ and the degreasing time is 10~20 minutes.

[0012] Optionally, the fabrication of the circuit board body specifically includes: Drill the required through holes in the stacked plate; wherein, the outermost layer of the stacked plate is a metal layer, the metal layer having an area to be gold plated; Electroplating, wherein the vias are metallized; The outer layer circuitry is fabricated on the metal layer using a pattern transfer process to obtain the desired circuit board body; wherein, the outer layer circuitry includes conductive lines and finger copper layers located in the area to be gold-plated.

[0013] Optionally, the fabrication of the outer circuit pattern on the metal layer using a pattern transfer process specifically includes: Conductive lines, finger copper layers, and conductive leads are fabricated on the metal layer using a pattern transfer process. The finger copper layers are located within the area to be gold-plated, and the conductive leads are located on the side of the area to be gold-plated away from the center of the circuit body. The conductive leads extend from the outer edge of the stacked plate to the area to be gold-plated. After the oil removal process using the oil remover, the method further includes: Remove the conductive lead.

[0014] Optionally, after removing the oil with the degreasing agent, the method further includes: After the oil is removed, the circuit board body is subjected to solder resist, exposure, development, and curing to expose the gold fingers.

[0015] On the other hand, the present invention provides a circuit board prepared by the above-mentioned processing method for gold fingers on a circuit board, comprising a circuit board body and gold fingers, wherein the gold fingers are disposed on the surface of the circuit board body, and the edges of the gold fingers are provided with the metallized holes.

[0016] This invention discloses a method for processing gold fingers on a circuit board. It abandons the conventional method of using dry film to protect metallized holes, instead employing a photosensitive resist-plating method to protect the metallized holes at the edges of the area to be gold-plated. Photosensitive resist-plating is printed on the surface of the circuit board, baked and cured to form a photosensitive protective film, and then exposed and developed to reveal the area to be gold-plated. This allows the photosensitive protective film to protect the non-gold-plated areas, preventing the gold plating solution from entering the metallized holes during gold finger plating. After gold plating, a descaling agent is used to remove the photosensitive resist-plating and the photosensitive protective film from the circuit board surface, revealing the original structure of the circuit board. This method satisfies the requirement of not plating the metallized holes with gold, significantly reduces processing costs, simplifies the operation process, improves protection reliability, and increases product yield. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for processing gold fingers on a circuit board according to an embodiment of the present invention; Figure 2 This is a schematic diagram of step S1 in a method for processing gold fingers on a circuit board according to an embodiment of the present invention; Figure 3 This is a schematic diagram of step S2 in a method for processing gold fingers on a circuit board according to an embodiment of the present invention; Figure 4 This is a schematic diagram of step S4 in the processing method of gold fingers on a circuit board provided in an embodiment of the present invention.

[0018] The reference numerals in the accompanying drawings are as follows: 1. Circuit board body; 11. Area to be gold plated; 12. Metallized hole; 13. Conductive line; 14. Conductive lead; 2. Gold finger. Detailed Implementation

[0019] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0020] Some circuit boards have gold fingers 2 designed on their edges. Gold fingers 2 refers to a row of metal contacts on the edge of the circuit board, which are shaped like "fingers". Their main function is to realize the electrical connection between the circuit board and other electronic components (such as connectors and motherboards). They are widely used in products that require frequent plugging and unplugging or high reliability connections, such as graphics cards, memory modules, hard drives, and industrial control boards.

[0021] like Figures 1 to 4 As shown, an embodiment of the present invention provides a method for processing gold fingers on a circuit board, comprising the following steps: S1: As Figure 2 As shown, a circuit board body 1 is fabricated; wherein, the surface of the circuit board body 1 has a gold-plated area 11, and the edge of the gold-plated area 11 is processed with metallized holes 12. It is understood that the hole walls of the metallized holes 12 are plated with a copper layer. Wherein, Figure 2 The dashed box in the figure represents the area 11 to be gold plated. The area 11 to be gold plated has a finger copper layer processed on it. The finger copper layer has the basic shape of the gold finger 2 required. Gold is then plated on the finger copper layer to form the gold finger 2 required on the final circuit board product.

[0022] S2: As Figure 3 As shown, photosensitive resist coating is used to plug the metallized holes 12 at the edge of the gold-plated area 11, and photosensitive resist coating is printed on the entire surface of the circuit board body 1, baked and cured to form a photosensitive protective film.

[0023] It is understandable that the metallization holes 12 at the edge of the area to be plated are closer to the area to be plated, and compared with the other metallization holes 12 on the circuit board body 1 that are far away from the area to be plated, the gold plating solution can easily enter the metallization holes 12 at the edge of the area to be plated.

[0024] Therefore, in this application, photosensitive resist is used to plug the metallized holes 12 at the edge of the area to be plated in order to protect the metallized holes 12 at the edge of the area to be plated. At the same time, photosensitive resist is printed on the entire surface of the circuit board body 1. The photosensitive resist is baked and cured to form a photosensitive protective film that covers the entire surface of the circuit board body 1 and the copper layer of the remaining metallized holes 12.

[0025] S3: Expose and develop the photosensitive protective film to reveal the area to be gold-plated 11.

[0026] It is understandable that exposure and development utilize UV ​​light to trigger a photochemical reaction in the photosensitive protective film, causing the portion of the photosensitive protective film corresponding to the area 11 to be gold-plated to dissolve in the developing solution, thereby exposing the area 11 to be gold-plated and enabling subsequent gold plating, while the remaining photosensitive protective film protects the non-gold-plated areas.

[0027] S4: As Figure 4As shown, the copper layer of the fingers in the area to be gilded 11 is plated with gold to form gold fingers 2. Among them, Figure 4 The black fill in the text indicates the gold-plated portion.

[0028] S5: As Figure 4 As shown, the degreaser is used to remove the oil, and the photosensitive protective film and the photosensitive anti-plating oil in the metallized hole 12 are removed.

[0029] Understandably, after the gold plating is completed, the circuit board is degreased with a degreasing agent to completely remove the anti-plating oil inside the metallized holes 12 and on the surface of the circuit board body 1, exposing the copper layer inside the metallized holes 12 without damaging the gold plating layer on the surface of the gold fingers 2 or other areas of the circuit board.

[0030] As can be seen from steps S1 to S5, the processing method for gold fingers on the circuit board in this application abandons the conventional method of dry film protection for metallized holes 12. Instead, it adopts a photosensitive resist-plating method to protect the metallized holes 12 at the edge of the area to be gold-plated 11. Photosensitive resist-plating is printed on the surface of the circuit board body 1, and the photosensitive resist-plating is baked and cured to form a photosensitive protective film. The photosensitive protective film is then exposed and developed to expose the area to be gold-plated 11. This allows the photosensitive protective film after exposure and development to protect the non-gold-plated area, thus preventing the gold plating solution from entering the metallized holes 12 when the gold fingers 2 are plated in the area to be gold-plated 11. After gold plating is completed, a descaling agent is used to remove the photosensitive resist-plating that plugged the metallized holes 12 and the photosensitive protective film on the surface of the circuit board body 1, exposing the original structure of the circuit board. This method not only meets the requirement of not plating the metallized holes 12 on the circuit board, but also significantly reduces processing costs, simplifies the operation process, improves protection reliability, and increases product qualification rate.

[0031] In one embodiment, when photosensitive resist plating oil is used to plug the metallized holes 12 at the edge of the gold-plated area 11 in step S2, the photosensitive resist plating oil overflows from the opening of the metallized holes 12 to the periphery by 0.1~0.3mm.

[0032] Understandably, during subsequent baking and curing, the photosensitive resist in the metallized hole 12 will release gas and shrink as it cures. To prevent the photosensitive resist from leaking out of the metallized hole 12 after curing and shrinkage, the amount of photosensitive resist filling the hole needs to be controlled, allowing 0.1~0.3mm of resist to overflow from the hole opening. This ensures that the photosensitive resist completely fills the metallized hole 12 after curing, preventing gaps that could allow the gold plating solution to seep in, while also avoiding material waste due to excessive overflow. In actual processing, the overflow amount can be adjusted appropriately according to the hole diameter of the metallized hole 12 to ensure the hole-sealing protection effect.

[0033] In one embodiment, the metallized holes 12 at the edge of the gold-plated area 11 are plugged by screen printing or dispensing.

[0034] Specifically, the screen printing method is used to fill the holes. During the screen printing process, the screen is placed on the circuit board body 1. The screen has holes that are aligned with the metallized holes 12 that need to be filled. The diameter of the hole is 0.1~0.3mm larger than the diameter of the corresponding metallized hole 12. The screen printing knife scrapes photosensitive resist ink onto the screen, so that the photosensitive resist ink fills the metallized holes 12 through each hole. The operation is simple and the processing efficiency is higher.

[0035] In one embodiment, baking and curing specifically includes: First, pre-bake at a low temperature, with a baking temperature of 70℃~75℃ and a baking time of 30~60 minutes; Then, bake at a high temperature of 100℃~120℃ for 25~35 minutes.

[0036] It is understandable that, since the photosensitive resist coating inside the metallized hole 12 has a certain depth, if high-temperature baking is used directly, the photosensitive resist coating on the outer surface of the metallized hole 12 will solidify first, causing the gas volatilized from the photosensitive resist coating inside the metallized hole 12 to be unable to escape. This can easily lead to the formation of bubbles or voids after the photosensitive resist coating inside the metallized hole 12 solidifies, affecting the subsequent blocking effect.

[0037] In this application, a segmented baking process is adopted. First, a low-temperature pre-baking is performed to allow the solvent in the photosensitive resist to evaporate slowly and solidify gradually from the inside out, avoiding premature solidification and sealing of pores on the surface. Then, a high-temperature baking is performed to solidify the photosensitive resist into a stable photosensitive protective film, ensuring the structural stability of the photosensitive protective film and the plugging structure, and avoiding problems such as peeling and cracking during subsequent exposure, development, or gold plating.

[0038] In one embodiment, step S5 uses an oil-removing agent to remove oil, specifically including: Organic degreasing agent is used to remove photosensitive anti-plating oil. The degreasing temperature is 40℃~60℃ and the degreasing time is 10~20 minutes.

[0039] Understandably, the degreaser is a special organic degreaser that matches the photosensitive resist coating, ensuring that the photosensitive resist coating dissolves quickly and does not corrode the copper layer on the surface of the circuit board body 1 and the gold plating layer on the gold fingers 2.

[0040] In one embodiment, step S1 specifically includes: S11: Drill the required through holes in the laminate; wherein, the outermost layer of the laminate is a metal layer with a gold-plated area 11. S12: Electroplating, through-hole forming metallized hole 12; S13: The outer layer circuit is fabricated on the metal layer by a pattern transfer process to obtain the required circuit board body 1; wherein, the outer layer circuit includes conductive lines 13 and finger copper layers located in the gold-plating area 11.

[0041] Understandably, the copper layer of the finger is processed together with the conductive line 13, which simplifies the process and improves processing efficiency.

[0042] In one embodiment, step S13 specifically includes: S131: Conductive lines 13, finger copper layers and conductive leads 14 are processed on the metal layer by pattern transfer process. The finger copper layer is located in the gold-plating area 11. The conductive leads 14 are located on the side of the gold-plating area 11 away from the center of the circuit body. The conductive leads 14 extend from the outer edge of the stack to the gold-plating area 11.

[0043] It is understood that the pattern transfer process refers to the sequential steps of film application, exposure, development, etching, and film removal. Pattern transfer is a conventional technique in this field and will not be elaborated upon here.

[0044] In one embodiment, after removing the oil with an oil remover, the process further includes: S132: Remove conductive lead 14. Specifically, this involves etching to remove conductive lead 14.

[0045] It is understandable that the conductive lead 14 is the carrier of power supply and conduction current to the area 11 to be plated during gold plating, forming a cathode circuit from the electroplating rack to the conductive lead 14 to each gold finger 2, so as to adsorb gold ions and deposit gold plating on the surface of the area 11 to be plated.

[0046] The conductive lead 14 is only used as a process structure to achieve the gold plating function. Therefore, the conductive lead 14 needs to be removed from the final product.

[0047] In one embodiment, after removing the oil with an oil remover, the process further includes: S6: After removing the photosensitive resist coating, the circuit board body 1 is solder resisted, exposed, developed, and cured to expose the gold fingers 2.

[0048] Understandably, solder resist is applied by brushing a layer of green solder mask onto the circuit board body 1 after the photosensitive solder mask has been removed. Through exposure-development-curing, the green solder mask covers the conductive lines 13, solder pads, and copper surface to provide protection against oxidation, short circuits, and moisture, while exposing the gold fingers 2.

[0049] In addition, an embodiment of the present invention also provides a circuit board, which is prepared by the processing method of gold fingers on the circuit board in any of the above embodiments. The circuit board includes a circuit board body 1 and gold fingers 2. The gold fingers 2 are disposed on the board surface of the circuit board body 1, and metallization holes 12 are provided on the edge of the gold fingers 2.

[0050] It should be noted that the circuit board can be a single-layer board or a multi-layer board.

[0051] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for processing gold fingers on a circuit board, characterized in that, include: A circuit board body is prepared; wherein the surface of the circuit board body has a gold-plated area, the gold-plated area is processed with a finger copper layer, and the edge of the gold-plated area is processed with metallized holes. Photosensitive resist coating is used to plug the metallized holes at the edge of the area to be gold plated, and photosensitive resist coating is printed on the entire surface of the circuit board body, baked and cured to form a photosensitive protective film. The photosensitive protective film is exposed and developed to reveal the area to be gold-plated. The copper layer of the finger in the area to be gold-plated is gold-plated to form a gold finger; The oil is removed by using an oil remover, and the photosensitive protective film and the photosensitive anti-plating oil in the metallized holes are removed.

2. The method for processing gold fingers on a circuit board according to claim 1, characterized in that, When photosensitive resist is used to plug the metallized holes at the edge of the area to be plated with gold, the photosensitive resist overflows from the opening of the metallized hole to the periphery by 0.1~0.3mm.

3. The method for processing gold fingers on a circuit board according to claim 2, characterized in that, The metallization holes at the edge of the area to be plated with gold are plugged using screen printing or adhesive dispensing.

4. The method for processing gold fingers on a circuit board according to claim 1, characterized in that, The baking and curing process specifically includes: First, pre-bake at a low temperature, with a baking temperature of 70℃~75℃ and a baking time of 30~60 minutes; Then, bake at a high temperature of 100℃~120℃ for 25~35 minutes.

5. The method for processing gold fingers on a circuit board according to claim 1, characterized in that, The process of using an oil-removing agent to remove oil specifically includes: Organic degreasing agent is used to remove photosensitive anti-plating oil. The degreasing temperature is 40℃~60℃ and the degreasing time is 10~20 minutes.

6. The method for processing gold fingers on a circuit board according to claim 1, characterized in that, The fabrication of the circuit board body specifically includes: Drill the required through holes in the stacked plate; wherein, the outermost layer of the stacked plate is a metal layer, the metal layer having an area to be gold plated; Electroplating, wherein the vias are metallized; The outer layer circuitry is fabricated on the metal layer using a pattern transfer process to obtain the desired circuit board body; wherein, the outer layer circuitry includes conductive lines and finger copper layers located in the area to be gold-plated.

7. The method for processing gold fingers on a circuit board according to claim 6, characterized in that, The process of fabricating an outer layer circuit pattern on the metal layer using a pattern transfer process specifically includes: Conductive lines, finger copper layers, and conductive leads are fabricated on the metal layer using a pattern transfer process. The finger copper layers are located within the area to be gold-plated, and the conductive leads are located on the side of the area to be gold-plated away from the center of the circuit body. The conductive leads extend from the outer edge of the stacked plate to the area to be gold-plated. After the oil removal process using the oil remover, the method further includes: Remove the conductive lead.

8. The method for processing gold fingers on a circuit board according to any one of claims 1 to 7, characterized in that, After the oil removal process using the oil remover, the method further includes: After the oil is removed, the circuit board body is subjected to solder resist, exposure, development, and curing to expose the gold fingers.

9. A circuit board, manufactured using the processing method for gold fingers on a circuit board according to any one of claims 1 to 8, characterized in that, It includes a circuit board body and gold fingers, the gold fingers are disposed on the surface of the circuit board body, and the edges of the gold fingers are provided with the metallized holes.

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