Leadless golden finger carrier plate and preparation method thereof

Abstract

The invention provides a preparation method of a leadless golden finger carrier plate. The preparation method comprises the following steps: providing a carrier plate comprising a first copper layer; the thickness of the first copper layer is less than or equal to 3 microns; a first layer of dry film is pasted on the first copper layer, a pattern area is formed through exposure and development, the pattern area comprises a circuit pattern area and a golden finger area, and the bottom of the pattern area abuts against the first copper layer; performing copper electroplating on the pattern area; pasting a second layer of dry film on the pattern area after copper electroplating and the first layer of dry film, and exposing and developing to expose the golden finger area; plating nickel and gold on the exposed gold finger area to form a lead-free gold finger; and removing the first layer of dry film and the second layer of dry film, and removing the first copper layer exposed after film stripping to obtain a circuit pattern and a golden finger on the surface of the carrier plate. The circuit pattern and the golden finger can be directly electroplated and formed without further etching, so that the preparation efficiency of the carrier plate is improved, and the application range of the carrier plate is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of gold finger and circuit pattern forming, and in particular to a leadless gold finger carrier board and a preparation method thereof. Background Art

[0002] In the production of circuit boards, in order to avoid the surface skin effect of the electroplated nickel-gold plate, a local electroplated nickel-gold process is required; that is, the circuit part on the circuit board is copper, and the gold fingers of the binding disk or plug interface used for gold wire need to be electroplated with nickel-gold surface treatment.

[0003] The traditional method of making PCB with partial electroplating includes: cutting → drilling → copper deposition → board electroplating → outer layer pattern transfer (including conductive leads for electroplating) → pattern electroplating → film stripping → alkaline etching → tin stripping → solder mask → dry film pasting → outer layer pattern transfer 2 (making partial electroplating patterns and protecting leads at the same time) → electroplating nickel gold → film stripping → alkaline etching leads → post-process. When using the lead process, when the circuit process is alkaline etching, the problem of lead position infiltration plating leading to lead residue is easy to occur during the production process; when the circuit process is acid etching, excessive etching or open lead circuit is easy to lead to poor electroplating; the phenomenon of partial electroplating pattern window deviation is easy to occur during the production process, leading to lead electroplating, and then causing lead residue and uneven front end of gold finger; after the circuit is made, the film is pasted, and the height difference between the copper surface of the circuit and the substrate surface is easy to cause the dry film to not be firmly pasted; there is also a process of printing wet film for filling and then pasting dry film in the industry, but the process flow is long and cannot completely eliminate the phenomenon of infiltration plating during electroplating.

[0004] In order to improve the forming process of the gold finger, the existing patent CN103702526A discloses a method for processing leadless electroplated gold fingers; after forming the circuit pattern, the printed circuit board is subjected to chemical copper deposition to obtain a chemical copper deposition layer; the gold finger position is exposed through the circuit manufacturing process; the gold finger is electroplated using the chemical copper deposition layer as a conductor, and then the film is stripped to form a leadless gold finger. However, this technical solution is to deposit copper, electroplate, and form the gold finger after the circuit is formed; before generating the gold finger, since there is already a circuit pattern on the carrier board, that is, the surface of the carrier board has a height difference between the circuit pattern and the non-circuit pattern area, it is easy to cause the dry film to not stick firmly, and the gold finger position seepage plating phenomenon occurs, which in turn causes the gold finger position to deviate or shift, affecting the subsequent plug-in stability and accuracy. Summary of the invention

[0005] In order to overcome the problems existing in the related art, one of the purposes of the present invention is to provide a method for preparing a leadless gold finger carrier, using a thinner first copper layer as a conductive layer, and using a first layer of dry film as a mask layer, and electroplating the circuit pattern area and the gold finger area at the same time to ensure that the circuit pattern and the gold finger are formed in the same plane; then using a second layer of dry film as a mask layer, the gold finger area is separately plated with nickel and gold; in the present application, both the circuit pattern and the gold finger can be directly electroplated and formed without further etching, thereby improving the preparation efficiency of the carrier and expanding the application range of the carrier.

[0006] In order to achieve the above purpose, this application adopts the following technical solutions:

[0007] A method for preparing a leadless gold finger carrier, comprising:

[0008] Providing a carrier board comprising a first copper layer; the thickness of the first copper layer is less than or equal to 3 micrometers;

[0009] A first layer of dry film is attached to the first copper layer, and exposed and developed to form a pattern area, wherein the pattern area includes a circuit pattern area and a gold finger area, and the bottom of the pattern area abuts against the first copper layer;

[0010] Electroplating copper on the graphic area;

[0011] A second layer of dry film is applied to the graphic area after copper electroplating and the first layer of dry film, and then exposed and developed to expose the gold finger area;

[0012] The exposed gold finger area is plated with nickel gold to form a leadless gold finger;

[0013] The first layer of dry film and the second layer of dry film are removed, and the first copper layer exposed after the film is removed to obtain the circuit pattern and gold fingers on the surface of the carrier board.

[0014] Furthermore, a first copper layer with a thickness less than or equal to 3 microns is deposited on the surface of the carrier.

[0015] Furthermore, the height of the graphic area after copper electroplating is smaller than the height of the first layer of dry film.

[0016] Furthermore, the height of the graphic area after copper electroplating is 3-5 microns smaller than the height of the first layer of dry film.

[0017] Furthermore, the height of the gold finger area after nickel-gold plating is smaller than the height of the first layer of dry film.

[0018] Furthermore, the first copper layer outside the pattern area is removed by a flash etching process.

[0019] Furthermore, the flash etching liquid used in the flash etching process includes hydrogen peroxide and sulfuric acid.

[0020] Furthermore, the spacing between the gold fingers on the surface of the carrier board is 1-4 mil.

[0021] The second purpose of the present application is to provide a leadless gold finger carrier, which is prepared by the preparation method as described above.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides a method for preparing a leadless gold finger carrier, comprising: providing a carrier comprising a first copper layer, wherein the thickness of the first copper layer is less than or equal to 3 microns; pasting a first layer of dry film on the first copper layer, exposing and developing to form a graphic area, wherein the graphic area comprises a circuit graphic area and a gold finger area, and the bottom of the graphic area abuts the first copper layer; electroplating copper on the graphic area; pasting a second layer of dry film on the copper-plated graphic area and the first layer of dry film, exposing and developing to expose the gold finger area to form a leadless gold finger; plating nickel gold on the exposed gold finger area; removing the first layer of dry film and the second layer of dry film, and removing the first copper layer exposed after film removal to obtain the circuit graphic and gold finger located on the surface of the carrier. The present application uses a relatively thin first copper layer as a conductive layer. After subsequent circuit patterns and gold fingers are formed, the first copper layer can be directly removed by a flash etching process, without the need to etch the circuit patterns or gold finger areas after electroplating, thereby improving the preparation efficiency of the circuit patterns and gold fingers. At the same time, there is no need to set an anti-corrosion layer on the top layer of the circuit patterns, thereby simplifying the formation process of the circuit patterns and further expanding the scope of application of the carrier board.

[0024] The present application uses the first layer of dry film as a mask layer, and electroplating is performed on the circuit pattern area and the gold finger area at the same time. No gold finger guide is required, but the gold finger is formed by electroplating while the circuit pattern is formed, thereby avoiding the cumbersome process steps of electroplating with the help of leads and then removing the leads during the formation of the gold finger, thereby improving the efficiency of carrier board preparation, and forming leadless gold fingers by etching and electroplating methods, which can also ensure the molding accuracy of the gold finger and improve the plug-in and unplugging stability of the carrier board.

[0025] The present application ensures that the circuit pattern and the gold finger are formed in the same plane, which can avoid the plating phenomenon, improve the accuracy of the gold finger area and the circuit pattern area, and the synchronous molding process can improve the preparation efficiency.

[0026] The present application uses a first layer of dry film to simultaneously form a circuit pattern and a gold finger, uses a second layer of dry film to form nickel and gold in the gold finger, and then removes the first layer of dry film and the second layer of dry film at one time, which helps to improve the forming efficiency and accuracy of the gold finger. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of depositing the first copper layer in Example 2;

[0028] Figure 2 This is a schematic diagram of the structure of attaching the first layer of dry film in Example 2;

[0029] Figure 3 It is a schematic diagram of the structure of copper electroplating in Example 2;

[0030] Figure 4 This is a schematic diagram of the structure of attaching the second layer of dry film in Example 2;

[0031] Figure 5 The schematic diagram of the structure of nickel-gold plating in Example 2;

[0032] Figure 6 A schematic diagram of the structure of removing the first layer of dry film and the second layer of dry film in Example 2;

[0033] Figure 7 This is a schematic diagram of the structure of the first copper layer exposed after the film is removed by flash etching in Example 2;

[0034] Figure 8 A schematic diagram of the structure of forming an inner layer circuit pattern in Example 3;

[0035] Fig. 9 This is a schematic diagram of the structure of the first copper layer pressed in Example 3;

[0036] Fig.10 This is a schematic diagram of the structure after drilling and hole metallization in Example 3;

[0037] Fig.11 This is a schematic diagram of the structure of attaching the first layer of dry film in Example 3;

[0038] Fig.12 This is a schematic diagram of the structure after copper electroplating in Example 3;

[0039] Fig.13 This is a schematic diagram of the structure of attaching the second layer of dry film in Example 3;

[0040] Fig.14 This is a schematic diagram of the structure of nickel-gold plating in Example 3;

[0041] Fig.15 A schematic diagram of the structure of removing the first layer of dry film and the second layer of dry film in Example 3;

[0042] Fig.16 It is a schematic diagram of the structure of the first copper layer exposed after the film is removed by flash etching in Example 3;

[0043] Fig.17 This is a schematic diagram of the structure of the gold finger in this application.

[0044] 1. Carrier board; 2. First copper layer; 3. First dry film layer; 4. Electroplated copper; 5. Second dry film layer; 6. Electroplated nickel and gold; 11. Inner layer circuit pattern; 12. Insulation laminate film; 13. Hole copper. DETAILED DESCRIPTION

[0045] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0046] Example 1

[0047] The present application provides a method for preparing a leadless gold finger carrier, comprising:

[0048] Providing a carrier board comprising a first copper layer; the thickness of the first copper layer is less than or equal to 3 micrometers;

[0049] A first layer of dry film is attached to the first copper layer, and exposed and developed to form a pattern area, wherein the pattern area includes a circuit pattern area and a gold finger area, and the bottom of the pattern area abuts against the first copper layer;

[0050] Electroplating copper on the graphic area;

[0051] A second layer of dry film is applied to the graphic area after copper electroplating and the first layer of dry film, and then exposed and developed to expose the gold finger area;

[0052] The exposed gold finger area is plated with nickel gold to form a leadless gold finger;

[0053] The first layer of dry film and the second layer of dry film are removed, and the first copper layer exposed after the film is removed to obtain the circuit pattern and gold fingers on the surface of the carrier board.

[0054] The present application uses a relatively thin first copper layer as a conductive layer. After subsequent circuit patterns and gold fingers are formed, the first copper layer can be directly removed by a flash etching process, without the need to etch the circuit patterns or gold finger areas after electroplating, thereby improving the preparation efficiency of the circuit patterns and gold fingers. At the same time, there is no need to set an anti-corrosion layer on the top layer of the circuit patterns, thereby simplifying the formation process of the circuit patterns and further expanding the scope of application of the carrier board.

[0055] The present application uses the first copper layer as the conductive layer and the first layer of dry film as the mask layer, and electroplates the circuit pattern area and the gold finger area at the same time. No gold finger guide is required, but the gold finger is formed by electroplating while the circuit pattern is formed, thereby avoiding the cumbersome process steps of electroplating with the help of leads and then removing the leads during the formation of the gold finger, thereby improving the efficiency of carrier board preparation, and forming leadless gold fingers by etching and electroplating methods, which can also ensure the molding accuracy of the gold finger and improve the plug-in stability of the carrier board.

[0056] This application ensures that the circuit pattern and the gold finger are formed in the same plane; it can avoid the plating phenomenon, improve the accuracy of the gold finger area and the circuit pattern area, and the synchronous molding process can improve the preparation efficiency.

[0057] At the same time, the present application uses the first layer of dry film to synchronously form the circuit pattern and the gold finger, uses the second layer of dry film to form the nickel and gold in the gold finger, and then removes the first layer of dry film and the second layer of dry film at one time, which helps to improve the forming efficiency and accuracy of the gold finger.

[0058] The spacing between the gold fingers in this application depends entirely on the performance of the first layer of dry film, and the spacing can be reduced to about 1 mil, while the spacing of the gold fingers prepared by the lead wire in the prior art is between 6-8 mil; the preparation method of this application can form small-pitch gold fingers, and it only needs to be kept within the resolution capability of the first layer of dry film, such as Fig.17 The final gold finger diagram is shown in the figure. Fig.17 The black lines in the gold finger area refer to the gaps between the gold fingers, and the parts between the black lines are the formed gold fingers.

[0059] In the present application, the first layer of dry film is used as a mask layer, and a graphic area is formed by exposure and development, and the graphic area includes a circuit graphic area and a gold finger area at the same time; in actual operation, the circuit graphic area is usually located at the center of the carrier board, and the gold finger area is usually located at the periphery of the circuit graphic area. In the present application, the first layer of dry film is used as a mask layer, and the central circuit graphic area and the peripheral gold finger area are defined at the same time; the advantage is that: the surface of the first copper layer is a smooth and flat surface, and the first layer of dry film is attached to the first copper layer, which can ensure that the first layer of dry film is firmly attached to the first copper layer, and avoid the unevenness of the first layer of dry film due to the unevenness of the carrier board, and then position deviation or plating occurs during the subsequent exposure, development and electroplating process.

[0060] Example 2

[0061] The present embodiment provides a method for preparing a leadless gold finger carrier, comprising:

[0062] S1: Figure 1As shown; providing a carrier board comprising a first copper layer, specifically, a first copper layer 2 can be deposited on the surface of the carrier board 1, and the thickness of the first copper layer is less than or equal to 3 microns

[0063] In this step, the first copper layer 2 exists only as a conductive layer for subsequent copper electroplating, and needs to be removed after the gold finger and circuit pattern are finally formed, so its thickness is usually small to ensure that the conductive function can be achieved and the thickness is suitable for flash etching removal. Specifically, the thickness of the first copper layer 2 is less than or equal to 3 microns.

[0064] The present application uses a first copper layer less than 3 microns as the starting copper, which can ensure that after the subsequent electroplating and film stripping of the graphic area, the first copper layer 2 outside the graphic area is removed by a flash etching process; if the first copper layer is too thick, flash etching cannot be achieved, and a complex process of forming an anti-etching layer on the top of the circuit image and then etching to form a circuit pattern will be formed as shown in the reference document in the background technology. The present application uses a flash etching process for a thinner copper layer to further simplify the production process of a leadless gold finger carrier.

[0065] S2: attaching a first layer of dry film 3 on the first copper layer 2, exposing and developing to form a pattern area, wherein the pattern area includes a circuit pattern area and a gold finger area, and the bottom of the pattern area abuts against the first copper layer 2.

[0066] The graphic area defined in this step includes the circuit graphic area and the gold finger area, that is, during the exposure and development process of the first layer of dry film 3, the circuit graphic area and the gold finger area are exposed at the same time. After exposure and development, the first layer of dry film 3 at the position of the circuit graphic area and the gold finger area is removed, exposing the first copper layer 2; other areas are still covered by the first layer of dry film 3; Figure 2 shown.

[0067] In this step, the thickness of the first layer of dry film 3 needs to be designed according to the thickness of the subsequent electroplated copper 4, and it is necessary to ensure that the height of the graphic area after the electroplated copper 4 is less than the height of the first layer of dry film 3; specifically, the height of the graphic area after the electroplated copper 4 can be defined as 3-5 microns less than the height of the first layer of dry film 3.

[0068] In this step, the material of the first layer of dry film 3 needs to be designed according to the minimum spacing between the gold fingers, and it is necessary to ensure that the resolution of the first layer of dry film 3 meets the gold finger width spacing and line width and line spacing capabilities. The dry film resolution represents the size of the minimum spacing between the gold fingers. When the dry film resolution is 25μm, the gold finger spacing can be 25μm.

[0069] S3: Electroplating copper 4 is performed on the graphic area.

[0070] After exposure and development, the carrier 1 is electroplated with copper using an electroplating device, and the positions where copper deposition is not required are covered by the first layer of dry film 3. The positions where copper deposition is required, that is, the bottom of the defined circuit pattern area and the gold finger area is the first copper layer 2, and the first copper layer 2 is used as a conductive layer. Copper 4 is electroplated synchronously in the grooves of the first layer of dry film 3 where the circuit pattern area and the gold finger area are located, so as to form the circuit pattern and the gold finger; Figure 3 shown.

[0071] The height of the graphic area after copper electroplating 4 is 3-5 microns less than the height of the first layer of dry film 3. The end point of copper electroplating 4 can be determined by visual inspection. In the present application, the depths of the grooves in the first layer of dry film 3 after exposure and development are the same, and the first copper layer 2 is used as the conductive layer for electroplating. Therefore, the copper plating speed in the grooves of the first layer of dry film 3 is basically the same. When the electroplating stops, circuit patterns and gold fingers of basically the same height are formed in each groove.

[0072] In this step, the height of the electroplated copper 4 is smaller than the height of the first layer of dry film 3 in order to avoid adding grinding processes, simplify the molding steps, and improve the preparation efficiency of the carrier board 1.

[0073] The present application uses the first copper layer as the starting copper and directly electroplates the graphic area, and the graphic area includes the circuit graphic area and the gold finger area, that is, the present application can directly form the circuit graphic area and the gold finger area in the process of electroplating copper for the graphic area, and after the gold finger is made, the first copper layer is directly flash-etched to remove it, and no additional operations are required to obtain the circuit graphic area, avoiding multiple mask exposure and etching operations for the circuit graphic in the prior art, simplifying the preparation process of the circuit graphic area including the gold finger area. It also avoids the complex process of multiple electroplating for the circuit graphic in the prior art, using the topmost plating layer as the anti-etching layer, and then etching to form the circuit graphic.

[0074] It should be noted that when preparing the circuit pattern area of ​​the present application, only copper electroplating is required to form the circuit pattern, and there is no need to nickel-gold plate the circuit pattern area or electroplate other anti-corrosion layers. This makes the pads in the circuit pattern area more applicable and can be applied to circuit pattern pads with various surface treatment methods, such as OSP and other fields, greatly expanding the scope of application of the present application.

[0075] S4: a second layer of dry film 5 is pasted on the pattern area after copper electroplating 4 and the first layer of dry film 3, and exposed and developed to expose the gold finger area.

[0076] The material of the second layer of dry film 5 can be the same as that of the first layer of dry film 3, and the second layer of dry film 5 is exposed and developed to expose the gold finger area. Since the first layer of dry film 3 and the second layer of dry film 5 are made of the same material, and the height of the circuit pattern and the gold finger is smaller than the height of the first layer of dry film 3, the second layer of dry film 5 can completely cover the circuit pattern and the gold finger surface. At this time, the second layer of dry film 5 is exposed and developed to expose the location of the gold finger. Figure 4 shown.

[0077] It should be noted that, since the height of the copper layer after copper electroplating 4 is less than the thickness of the first layer of dry film 3 , when filling the second layer of dry film 5 , the groove in the first layer of dry film 3 on the top of the gold finger will be filled, and then the second layer of dry film 5 will be globally pasted on the first layer of dry film 3 .

[0078] The present application can also select a second layer of dry film 5 of a different material from the first layer of dry film 3, so that when the second layer of dry film 5 is exposed and developed, a position slightly larger than the gold finger area can be defined, so that the gold finger area and a small area outside the gold finger area are exposed. Since the materials of the first layer of dry film 3 and the second layer of dry film 5 are different, the conditions for the exposure and development of the second layer of dry film 5 are different from those for the exposure and development of the first layer of dry film 3, that is, the exposure and development of the second layer of dry film 5 only acts on the second layer of dry film 5, and does not act on the first layer of dry film 3, so that Figure 4 As shown, the gold finger area in the first layer of dry film 3 is exposed, and the gold finger area and a small area outside the gold finger area in the second layer of dry film 5 are also exposed. The advantage of this is that the subsequent nickel-gold plating can be observed through the larger window in the second layer of dry film 5, thereby improving the accuracy of nickel-gold plating.

[0079] S5: The exposed gold finger area is plated with nickel gold to form a lead-free gold finger.

[0080] like Figure 5 As shown, the height of the gold finger area after nickel-gold plating in this step is less than the height of the first layer of dry film 3. This is because the size of the groove in the second layer of dry film 5 may be larger than the gold finger area. If it exceeds the height of the first layer of dry film 3, the accuracy of the nickel-gold position cannot be controlled.

[0081] S6: removing the first dry film 3 and the second dry film 5, removing the first copper layer 2 exposed after the film is removed, and obtaining the circuit pattern and gold fingers on the surface of the carrier board 1.

[0082] like Figure 6As shown, in this step, the first layer of dry film 3 and the second layer of dry film 5 can be removed by dissolving method. Regardless of whether the materials of the first layer of dry film 3 and the second layer of dry film 5 are the same, they can be dissolved and removed by dissolving liquid. The specific choice of dissolving liquid can be determined according to the material and performance of the dry film. After the dry film is dissolved, the first copper layer 2, the circuit pattern and the gold finger will be exposed, wherein nickel gold is deposited on the gold finger.

[0083] like Figure 7 As shown, the first copper layer 2 outside the graphic area is removed by a flash etching process. Specifically, the height of the electroplated copper 4 is much greater than the height of the first copper layer 2, that is, the height of the circuit pattern and the gold finger is much greater than the height of the first copper layer 2. For example, the height of the electroplated copper 4 is 35 microns, and the height of the first copper layer 2 is 3 microns. Differential etching can be used to reduce the copper as a whole until the first copper layer 2 is completely etched away. And the flash etching solution does not need to etch nickel and gold, it only needs to etch the copper layer. The present application utilizes the significant height difference between the electroplated copper and the first copper layer, and directly performs flash etching to form a circuit pattern in one step, which simplifies the forming efficiency of the circuit pattern, while ensuring that the height of the electroplated pattern meets the requirements.

[0084] The flash etching liquid used in the flash etching process of the present application includes hydrogen peroxide and sulfuric acid; the specific concentration of sulfuric acid can be 60-100g / L; the concentration of hydrogen peroxide can be 20-40g / L, and the hydrogen peroxide and sulfuric acid are compounded according to a mass ratio of 1:1.

[0085] After the flash etching, observe whether the first copper layer 2 in the carrier board 1 is etched cleanly to ensure that only the circuit pattern and the gold finger are left.

[0086] In the present application, the minimum spacing between the gold fingers depends on the resolution capability of the first layer of dry film 3 , and the minimum spacing between the gold fingers on the surface of the carrier board 1 can be 1 mil.

[0087] Example 3

[0088] The present embodiment provides a method for preparing a leadless gold finger substrate, which is used to simultaneously form an outer layer circuit pattern and a gold finger, and specifically includes:

[0089] S1: Figure 8 As shown; an inner layer circuit pattern 11 is formed in the carrier board 1 to form an inner layer core board;

[0090] S2: Laminating the first copper layer 2 on the carrier 1 by vacuum lamination process, wherein the first copper layer 2 is located in a lamination material such as an insulating laminate film 12, and the thickness of the first copper layer 2 is less than or equal to 3 microns. The insulating laminate film 12 can be Ajinomoto ABF, Newface NBF, etc., and has a thin copper layer, i.e., the first copper layer 2, on its surface.

[0091] The insulating laminate film 12 is pressed onto the inner core board by a vacuum laminating machine, and the vacuum laminating parameters are as follows: temperature 110°C, pressure 6kg, time 100s; Fig. 9 The structure of the carrier board 1 is shown.

[0092] S3: Laser drilling: If the product requires blind holes, laser drilling can be performed after browning; for example, if the aperture of the blind hole is 50μm, the laser parameters are set as follows: mask: 1.10mm, laser energy: 2.7mj, pulse width × number of guns: 8μs × 1+3μs × 2; 8us × 1+4us × 2.

[0093] If the product requires vias, mechanical drilling can be performed; the thickness-to-diameter ratio of mechanical drilling is recommended to be ≤6.

[0094] S4: hole metallization treatment: copper is deposited in the laser blind hole or through hole that needs to be connected to form hole copper 13; Fig.10 As shown, the deposited copper thickness is about 1μm; the micro-etching amount in the copper cylinder is controlled at 0.5-1μm; when using the gantry line for production, the baffles need to be thickened on both layers of the production board to avoid excessive micro-etching in the micro-etching cylinder.

[0095] S5: Paste a first layer of dry film 3 on the first copper layer 2 of the inner core board, expose and develop to form a graphic area, wherein the graphic area includes an outer layer circuit graphic area and a gold finger area, and the bottom of the graphic area abuts against the first copper layer 2 or the metallized hole.

[0096] The graphic area defined in this step includes the outer circuit graphic area and the gold finger area, that is, during the exposure and development process of the first layer of dry film 3, the outer circuit graphic area and the gold finger area are exposed at the same time. After exposure and development, the first layer of dry film 3 at the location of the outer circuit graphic area and the gold finger area is removed, exposing the first copper layer 2; other areas are still covered by the first layer of dry film 3; Fig.11 shown.

[0097] In this step, when the thickness of the first layer of dry film 3 is 40 micrometers and the resolution capability of the first layer of dry film 3 is 50 micrometers, the minimum spacing of the gold fingers can be 50 micrometers.

[0098] S6: electroplating copper 4 on the graphic area.

[0099] After exposure and development, the carrier board 1 is electroplated with copper 4 by using electroplating equipment, and the position where copper deposition is not required is covered by the first layer of dry film 3. The position where copper deposition is required, that is, the bottom of the outer layer circuit pattern area and the gold finger area defined is the first copper layer 2, and the first copper layer 2 or the hole copper 13 is used as the conductive layer. The outer layer circuit pattern area and the gold finger area are located in the first layer of dry film 3 where copper 4 is electroplated synchronously to form the outer layer circuit pattern and the gold finger; Fig.12 shown.

[0100] The height of the graphic area after copper electroplating 4 is about 5 microns less than the height of the first layer of dry film 3. The end point of copper electroplating 4 can be determined by visual inspection. In the present application, the depths of the grooves in the first layer of dry film 3 after exposure and development are the same, and the first copper layer 2 is used as the conductive layer for electroplating. Therefore, the copper plating speed in the grooves of the first layer of dry film 3 is basically the same. When the electroplating stops, the outer layer circuit graphics and gold fingers of basically the same height are formed in each groove.

[0101] After the outer layer circuit pattern is electroplated, hot air drying is performed; a conventional horizontal line can be used, with a drying time of 10s and a temperature of 85±5℃.

[0102] S7: Paste a second layer of dry film 5 on the pattern area after copper electroplating 4 and the first layer of dry film 3, and expose and develop to expose the gold finger area; Fig.13 The film pasting temperature of the second layer of dry film 5 may be 110±5°C.

[0103] After the second layer of dry film 5 is exposed and developed, since the height of the gold finger is smaller than that of the first layer of dry film 3, the size of the groove in the first layer of dry film 3 is adapted to the gold finger, and the size of the groove in the second layer of dry film 5 is 50 microns larger than the gold finger in all dimensions; this is convenient for observing the subsequent nickel-gold plating situation.

[0104] S8: Nickel-gold plating is performed on the exposed gold finger area.

[0105] like Fig.14 As shown, the height of the gold finger area after nickel-gold plating in this step is less than the height of the first layer of dry film 3. This is because the size of the groove in the second layer of dry film 5 may be larger than the gold finger area. If it exceeds the height of the first layer of dry film 3, the accuracy of the nickel-gold position cannot be controlled. Specifically, the thickness of the nickel layer is 3-5μm, and the thickness of the gold layer is 0.025μm-0.05μm; the thickness can be changed as needed.

[0106] S9: removing the first dry film 3 and the second dry film 5, removing the first copper layer 2 exposed after the film is stripped, and obtaining the outer layer circuit pattern and gold fingers on the surface of the carrier board 1.

[0107] like Fig.15 As shown, in this step, the first layer of dry film 3 and the second layer of dry film 5 can be removed by dissolving method. Regardless of whether the materials of the first layer of dry film 3 and the second layer of dry film 5 are the same, they can be dissolved and removed by dissolving liquid. The specific choice of dissolving liquid can be determined according to the material and performance of the dry film. After the dry film is dissolved, the first copper layer 2, the circuit pattern and the gold finger will be exposed, wherein nickel gold is deposited on the gold finger.

[0108] like Fig.16As shown, the first copper layer 2 outside the graphic area is removed by flash etching. Specifically, the height of the electroplated copper 4 is much greater than the height of the first copper layer 2, that is, the height of the circuit pattern and the gold finger is much greater than the height of the first copper layer 2. For example, the height of the electroplated copper 4 is 35 microns, and the height of the first copper layer 2 is 3 microns. Differential etching can be used to reduce the copper as a whole until the first copper layer 2 is completely etched away. And the flash etching solution does not need to etch the nickel and gold, but only needs to etch the copper layer.

[0109] The flash etching liquid used in the flash etching process of the present application includes hydrogen peroxide and sulfuric acid; the specific concentration of sulfuric acid can be 60-100g / L; the concentration of hydrogen peroxide can be 20-40g / L, and the hydrogen peroxide and sulfuric acid are compounded according to a mass ratio of 1:1.

[0110] After the flash etching, observe whether the first copper layer 2 in the carrier board 1 is etched cleanly to ensure that only the circuit pattern and the gold finger are left.

[0111] S10: Complete solder mask production until the finished board.

[0112] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a leadless gold finger carrier, characterized in that: include: providing a carrier board including a first copper layer; The thickness of the first copper layer is less than or equal to 3 microns; A first layer of dry film is attached to the first copper layer, and exposed and developed to form a pattern area, wherein the pattern area includes a circuit pattern area and a gold finger area, and the bottom of the pattern area abuts against the first copper layer; Electroplating copper on the graphic area; A second layer of dry film is applied to the graphic area after copper electroplating and the first layer of dry film, and then exposed and developed to expose the gold finger area; Nickel-gold plating is performed on the exposed gold finger area; The first layer of dry film and the second layer of dry film are removed, and the first copper layer exposed after the film is removed to obtain the circuit pattern and gold fingers on the surface of the carrier board.

2. The method for preparing a leadless gold finger carrier according to claim 1, characterized in that: A first copper layer with a thickness less than or equal to 3 microns is deposited on the surface of the carrier board.

3. The method for preparing a leadless gold finger carrier according to claim 1, characterized in that: The height of the graphic area after copper electroplating is smaller than the height of the first layer of dry film.

4. The method for preparing a leadless gold finger carrier according to claim 3, characterized in that: The height of the graphic area after copper electroplating is 3-5 microns smaller than the height of the first layer of dry film.

5. The method for preparing a leadless gold finger carrier according to claim 1, characterized in that: The height of the gold finger area after nickel-gold plating is smaller than the height of the first layer of dry film.

6. The method for preparing a leadless gold finger carrier according to claim 1, characterized in that: The first copper layer outside the pattern area is removed by a flash etching process.

7. The method for preparing a leadless gold finger carrier according to claim 6, characterized in that: The flash etching liquid used in the flash etching process includes hydrogen peroxide and sulfuric acid.

8. The method for preparing a leadless gold finger carrier according to claim 1, characterized in that: The spacing between the gold fingers on the surface of the carrier board is 1-4 mil.

9. A leadless gold finger carrier, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

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