A production process of three-sided gold-plated gold finger

Abstract

The application discloses a production process of a three-breaded gold-plated gold finger, which is connected to the front end of the gold finger in the form of outer pull lead + silk screen wet film, makes the gold finger conductive with the whole PCB board surface, completes the production of the gold-plated gold finger in the form of electroplated nickel gold, then etches off the lead, and then carries out the production of the post-process; the main key points of the process are as follows: the quality of the silk screen wet film, the temperature and time of pre-baking, the exposure energy, the parameters during the plating of the gold finger, and the quality during the etching of the lead; the production process is simple and easy to implement, optimizes the production process of the three-breaded gold-plated gold finger, solves the lead residue caused by the traditional hand tearing lead process and the abnormal plating caused by the dry film pressing or blue glue pressing process, and the produced gold finger has better operability, higher yield and better quality, and can be mass-produced.

Description

Technical Field

[0001] This invention relates to a manufacturing process for gold fingers, specifically a manufacturing process for three-sided gold-plated fingers, belonging to the field of PCB boards. Background Technology

[0002] With the rapid development of the electronics industry, the demand for cutting-edge and specialized products is urgent. Simple single- or double-sided circuit boards can no longer meet market needs. PCB companies must develop products with higher precision, finer circuitry, and greater complexity and diversity to survive in this highly competitive industry. During the PCB manufacturing process, gold fingers are plated on the board to transmit signals. These gold fingers are finger-like pads that are inserted into slots and make contact with the metal spring contacts inside the slots. Because this design requires high wear resistance and conductivity on the pad surface, a layer of nickel and a layer of gold are plated on the pad surface.

[0003] With the rise of electronic products, the demand for PCB circuit boards has gradually increased, leading to higher performance, appearance, and quality requirements for the finger components connecting high-speed signal lines. Current production processes for three-sided gold-plated fingers typically involve beveling, manually tearing leads, applying blue adhesive, or pressing dry film. This results in persistent issues such as lead residue, plating bleed, gaps, exposed copper, substrate damage, and finger tip lifting. Manual production is inefficient, significantly increasing costs and reducing competitiveness, especially for long / short and segmented gold fingers. To address this, patent CN107318231A describes a method for manufacturing gold fingers and a PCB. By setting up interpolating leads and three outer layer pattern transfers, it enables the production of long, short, and / or segmented gold fingers. This method is not only simple but also ensures gold finger quality, meeting industry demands, simplifying the PCB manufacturing process, and improving production efficiency. Patent CN107734876A... The method of gold plating the gold fingers on PCB boards uses a simple method to remove the gold finger leads on the PCB board. The process requirements are not high, the cost is low, it is suitable for mass production, and the quality of the PCB boards produced is stable. However, the above patents have not optimized the yield of the gold fingers. At present, the appearance yield of the gold fingers is low and the problem remains unsolved. Therefore, a new process and method are urgently needed to improve or solve the main anomalies, thereby improving the yield and enhancing competitiveness. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a production process for three-sided gold-plated fingers. This production process is simple and easy to implement, and the produced gold fingers have a higher yield and better quality.

[0005] To solve the above technical problems, the present invention provides a manufacturing process for three-sided gold-plated fingers, specifically including the following steps:

[0006] S1: From material cutting to pretreatment of inner core board, wet film coating, exposure, development and etching, to complete the pattern transfer of inner layer circuit, then to inner layer AOI inspection and punching out rivet holes, and then to lamination production.

[0007] S2: The inner core board undergoes pretreatment browning, then PP is cut, pre-stacked, and then the boards are arranged for the outermost layer pressing production. If multiple pressing is required, the production is carried out in multiple cycles between the five processes of laser / drilling → electroplating → circuit → AOI → pressing.

[0008] S3: The PCB board produced by the last lamination is transferred to laser or drilling processing, and then the holes are metallized and made conductive by copper plating. Then, blind holes are filled and through holes are electroplated on the whole board.

[0009] S4: After electroplating, the PCB board will undergo pattern transfer processing of the outer layer circuit. The pattern transfer process is as follows: pretreatment - lamination - exposure - development - etching - stripping. During the pattern transfer process, the gold finger guide lines of the unit will be made. At the same time, during the pattern transfer process, it is important to ensure that the dry film is not pressed off-center during lamination. Copper must be left at the board edge >1mm. After etching, the board will be transferred to AOI for inspection and repair.

[0010] S5: PCBs that have passed inspection are transferred to solder mask production. The solder mask production process is as follows: pretreatment - silkscreen printing / spraying - pre-baking - exposure - development. Specifically:

[0011] After the roughened copper surface and cleaned board surface are pretreated, the solder resist ink is evenly coated on the PCB board by screen printing or spraying. After pre-baking, it is exposed and developed. Note that the solder resist ink is not completely covered on the false exposure and the edge of the PCB board. At the same time, the gold finger guide line in the unit is opened out.

[0012] S6: After the PCB board for solder mask production is completed, the characters are produced. The characters are silkscreened and the thickness of the characters is controlled to be <30um. Then the impedance test is performed.

[0013] S7: After character production is complete, proceed to solder resist screen printing wet film. The solder resist screen printing wet film process is: pretreatment - screen printing - pre-baking - exposure - development - air exposure / UV baking - AVI, specifically:

[0014] The pretreatment only involves acid washing, controlling the thickness of the screen printing wet film, the pre-baking temperature and time, and the exposure energy. After development, it needs to be air-exposed or UV-baked, and then transferred to AVI for inspection. After scanning, the residual adhesive, foreign matter and dirt on the copper surface of the gold fingers are manually scraped off.

[0015] S8: After AVI repair, the PCB is transferred to the outer layer for gold plating dry film. Without pretreatment, the film is directly laminated, then exposed and developed to cover the areas that do not need gold plating. Then it is transferred to the surface treatment for nickel-gold plating of the gold fingers.

[0016] S9: After the gold fingers are plated, the PCB board is transferred to the outer layer for dry film and wet film removal. Then, without pretreatment, the dry film of the leads is etched, exposed, developed and etched. The leads are completely etched away, and then the film is removed. Then, without pretreatment, the selective dry film is directly etched, exposed and developed. After development, it is transferred to the surface treatment to complete selective gold plating. Then the film is removed again, followed by molding, electrical testing and final inspection processes.

[0017] The technical solution further defined in this invention is:

[0018] Furthermore, in the aforementioned three-sided gold-plated finger production process, when cutting PP in step S2, if the PP is high-density adhesive or multiple PP sheets or multiple core boards are pressed together, hot melting and riveting operations are performed.

[0019] Technically, this invention addresses the issue that when PP is high-density adhesive or multiple PP sheets or multiple core boards are laminated, existing technologies must be used for hot-melt and riveting operations based on the specific circumstances to prevent the sliding plate from causing layer misalignment.

[0020] In the aforementioned three production processes of gold-plated fingers, the gold fingers include ordinary gold fingers that are the same length and flush, gold fingers of different lengths within a unit, and segmented fingers where the fingers within a unit are divided into one or more segments.

[0021] In the aforementioned three-sided gold-plated finger manufacturing process, in step S1, inner layer processing is performed on the PCB board, and 6-8 rivet holes are punched out.

[0022] In the aforementioned three-sided gold-plated finger production process, in step S3, lamination, drilling, copper plating, and electroplating are performed on the PCB board. The HDI board requires at least two laminations, the backlight level of the copper plating is >9, the blind holes are filled during electroplating, and the dimple degree is controlled to be <15um.

[0023] In the aforementioned three-sided gold-plated finger production process, the etching solution used in step S4 is sodium persulfate solution, and all the circuits on the outer layer of the PCB board are made, including the gold fingers of the unit with external leads, forming ordinary gold fingers, long and short gold fingers or segmented gold fingers.

[0024] In the aforementioned three-sided gold-plated finger production process, the area not covered by the solder resist ink on the board edge during step S5 solder resist production must be >2mm.

[0025] Technical effect: In step S5 of this invention, care should be taken to ensure that the exposed areas and the solder mask ink on the edge of the PCB board are not completely covered, otherwise it will affect the quality of the subsequent gold-plated fingers. At the same time, the gold finger guide lines in the unit need to be exposed through windows to facilitate subsequent lead etching.

[0026] In the aforementioned three-sided gold-plated finger production process, in step S7, the wet film thickness is 40-50um during solder resist wet film production. After screen printing, it needs to stand for 15-20 minutes, pre-baking at 70-75℃ for 15-35 minutes, exposure energy of 9-10 divisions, and the film expansion and contraction controlled within + / -0.025mm. After development, it is air-exposed and then exposed to 200mJ energy or UV-baked once.

[0027] Technically, the pretreatment only involves acid washing, controlling the thickness of the screen-printed wet film, the pre-baking temperature and time, and the exposure energy. After development, air exposure or UV baking is required to better cure the film, increase the adhesion between the wet film and the copper surface, and reduce the risk of plating leakage when gold-plating fingers.

[0028] In the aforementioned three-sided gold-plated finger production process, the current during the nickel-gold electroplating process in step S8 is <2.5A.

[0029] Technically, excessive current can easily burn the board and cause plating to penetrate more easily, posing a significant risk.

[0030] In the aforementioned three-sided gold-plated finger production process, the dewetting film and dry film after electroplating nickel and gold in step S9 are produced at a linear speed of 0.5-0.8 m / min. The etching lead solution is an ammonium chloride solution with a side etching amount of <0.025 mm. The three defilm removal solutions are all sodium hydroxide solutions.

[0031] For technical effectiveness, a production line speed of 0.5-0.8 m / min is used to strip the dry and wet films at a relatively low speed to prevent incomplete stripping from affecting subsequent etching.

[0032] The beneficial effects of this invention are:

[0033] In the pattern transfer process, S4 of this invention requires that the dry film not be pressed off-center. Pressing off-center will cause the copper on the edge of the PCB board to be etched away. Copper needs to be left on the edge of the board to avoid insufficient contact area during gold plating, which would affect the conductivity and thus affect the quality of the gold plating.

[0034] In step S6 of this invention, in order to avoid the abnormality of incomplete film removal due to film entrapment during the three film removal processes after gold-plated fingers, which would affect the appearance quality, especially the recognition of QR codes, only screen printing is allowed, not inkjet printing. Furthermore, the character thickness must be reduced as much as possible while meeting customer requirements.

[0035] In step S7 of this invention, after development, air exposure or UV baking is required to better cure the film, increase the adhesion between the wet film and the copper surface, reduce the risk of plating through during gold plating of the fingers, and then transfer the film to AVI for inspection. After scanning, the residual glue, foreign matter and dirt on the copper surface of the gold fingers are manually scraped off to reduce the proportion of poor quality fingers with exposed copper during gold plating.

[0036] This invention, under the premise of existing equipment and process capabilities, adapts to local conditions and optimizes the process in the early stage. It uses a production method of solder mask wet film printing + gold plating dry film + lead etching. The outer layer circuit, AOI inspection, and solder mask production are normal. The characters need to be produced by screen printing to avoid the characters being too high and film clamping when the gold fingers are plated in the subsequent gold plating dry film. The parameters of subsequent processes such as screen printing width, wet film thickness, pre-baking temperature, exposure energy, development, and gold plating current and voltage are also subject to high requirements. When etching the leads, it is also necessary to carefully control the side etching amount of the fingers to ensure that the gold suspension of the fingers is OK and reduce the risk of quality abnormalities such as finger gaps / collapse edges and lead residue. Therefore, without changing the overall process and equipment, the continuous optimization of the production parameters of each process becomes very important to meet the increasingly stringent appearance and quality requirements of PCB boards. This invention conducts DOE comparative tests on the production parameters of key processes to confirm the optimal production process and process parameters, improve the first pass rate in the production process, and make the finished product yield above 92%, gradually improving and maintaining stability.

[0037] In the later stages of this invention, new automated equipment was introduced in a targeted manner to further improve the pass rate, inspection efficiency and standardization of inspection in the production process. For example, the introduction of AVI automatic scanning machine + maintenance can effectively remove residual glue, foreign matter and other dirt from the copper surface of the fingers before gold plating, reducing the process defect rate by at least 5%.

[0038] With the effective improvement of personnel, machinery, materials, methods, and environment, this invention not only increases the final yield of three-sided gold-plated products from 80%-85% to 90%-97%, but also gradually moves from samples to small batches and large batches, meeting customer needs, significantly improving production efficiency, and greatly enhancing competitiveness. Attached Figure Description

[0039] Figure 1 This is a flowchart of the production process of the three gold-plated fingers in an embodiment of the present invention;

[0040] Figure 2 The image shows a finished product of a regular gold finger produced using the three-sided gold plating process in an embodiment of the present invention.

[0041] Figure 3 The image shows finished products of gold fingers of varying lengths produced using a three-sided gold plating process according to an embodiment of the present invention.

[0042] Figure 4 This is a finished product image of segmented gold fingers produced using a three-sided gold plating process according to an embodiment of the present invention; Detailed Implementation

[0043] Example 1

[0044] This embodiment provides a manufacturing process for a three-sided gold-plated finger, such as... Figure 1 The process shown includes the following steps:

[0045] S1: From material cutting to pretreatment of inner core board, wet film coating, exposure, development and etching, to complete the pattern transfer of inner layer circuit, then to inner layer AOI inspection and punching out 6-8 rivet holes, and then to lamination production.

[0046] The specific process of inner layer pretreatment is as follows: board entry → degreasing → water washing → micro etching → water washing → acid washing → water washing → drying → board exit. The function of inner layer pretreatment is to clean the board surface, remove copper surface oxidation, increase the micro-roughness of the copper surface, and enhance the adhesion between the copper surface and the dry or wet film.

[0047] S2: The inner core board undergoes pretreatment browning, then PP is cut, pre-stacked, and then the boards are arranged for the outermost layer pressing production. If multiple pressing is required, the production is carried out in multiple cycles between the five processes of laser / drilling → electroplating → circuit → AOI → pressing.

[0048] The pre-lamination process is as follows: board loading → pickling → water washing → alkali washing → water washing → pre-immersion → browning → water washing → drying → board unloading. The purpose of the pre-lamination process is to remove oxides and oil stains from the copper surface, roughen the copper surface, and form an organic metal film with the copper surface to enhance the bonding force with PP.

[0049] S3: The PCB board produced by the last lamination is transferred to laser or drilling processing (HDI board requires laser + drilling processing), and then the holes are metallized and conductive through copper plating treatment is performed. Then, blind holes are filled and through holes are electroplated on the whole board.

[0050] S4: After electroplating, the PCB board will undergo pattern transfer processing of the outer layer circuit. The pattern transfer process is as follows: pretreatment - lamination - exposure - development - etching - stripping. During the pattern transfer process, the gold finger guide lines of the unit will be made. At the same time, during the pattern transfer process, it is important to ensure that the dry film is not pressed off-center during lamination. Copper must be left at the board edge >1mm. After etching, the board will be transferred to AOI for inspection and repair.

[0051] The specific process of the outer layer pretreatment is as follows: board entry → pickling → water washing → grinding → water washing + ultrasonic immersion → ultra-roughening → water washing → pickling → water washing → drying → board exit. The function of the outer layer pretreatment is to clean the board surface, remove copper oxides, oil stains and other dirt, roughen the copper surface, and enhance the adhesion between the copper surface and the dry film.

[0052] S5: PCBs that have passed inspection are transferred to solder mask production. The solder mask production process is as follows: pretreatment (slightly different from that of outer layer circuitry) - silkscreen printing / spraying - pre-baking - exposure - development, specifically:

[0053] After the roughened copper surface and cleaned board surface are pretreated, the solder resist ink is evenly coated on the PCB board by screen printing or spraying. After pre-baking, exposure and development are performed. Note that the solder resist ink should not be completely covered on the false exposure and the edge of the PCB board. The area of ​​the solder resist ink not covered on the edge of the board should be >2mm. At the same time, the gold finger guide line in the unit is opened out.

[0054] The specific process of pretreatment before solder resist is as follows: board entry → pickling → water washing → grinding → volcanic ash → water washing + ultrasonic immersion → water washing → drying → board exit. The purpose of pretreatment before solder resist is to remove oxides, oil and impurities from the board surface, thoroughly clean and roughen the board surface, so that it has good adhesion to the solder resist ink.

[0055] S6: After the PCB board for solder mask production is completed, the characters are produced. The characters are silkscreened and the thickness of the characters is controlled to be <30um. Then the impedance test is performed.

[0056] S7: After character production is complete, the process moves to solder resist screen printing wet film. The solder resist wet film printing process is as follows: pretreatment (only acid pickling is on, abrasive brushes and volcanic ash are off) - screen printing - pre-baking - exposure - development - air exposure / UV baking - AVI, specifically:

[0057] Pre-treatment only involves acid washing, controlling the thickness of the wet screen printing film to 40-50um. After screen printing, it needs to stand for 15-20 minutes, pre-baking temperature 70-75℃, pre-baking for 15-35 minutes, exposure energy 9-10 divisions, and the film expansion and contraction controlled within + / -0.025mm. After development, it is air-exposed and then baked once with 200mj energy or UV. Then it is transferred to AVI for inspection. After scanning, the residual adhesive, foreign matter and dirt on the copper surface of the gold fingers are manually scraped off.

[0058] S8: After AVI inspection, the PCB is transferred to the outer layer for gold plating dry film. No pretreatment is performed. The film is directly laminated, then exposed and developed to cover the areas that do not need to be gold plated. Then it is transferred to the surface treatment for nickel-gold electroplating of the gold fingers. The current during the nickel-gold electroplating process is <2.5A.

[0059] S9: After the gold fingers are plated, the PCB board is transferred to the outer layer for dry and wet film stripping at a line speed of 0.5-0.8 m / min. Then, without pretreatment, the lead wires are etched, exposed, developed, and etched completely. No lead wire residue is allowed. The film is then stripped again, and without pretreatment, the selective dry film is directly etched, exposed, and developed. After development, it is transferred to the surface treatment stage for selective gold plating. The film is then stripped again, followed by molding, electrical testing, and final inspection. The final gold fingers are shown below. Figure 2-4 As shown;

[0060] No incomplete removal of the film is allowed in any of the three stripping processes. The etching solution used for the lead wires is an ammonium chloride solution, and no lead wire residue is allowed. The lateral etching depth is <0.025 mm. The three stripping solutions are all sodium hydroxide solutions.

[0061] In this embodiment, when cutting PP in step S2, if the PP is high-density adhesive or multiple PP sheets or multiple core boards are pressed together, hot melting and riveting operations are performed.

[0062] In this embodiment, the gold fingers include ordinary gold fingers that are the same length and aligned, gold fingers of different lengths within a unit, and segmented fingers within a unit that are divided into one or more segments.

[0063] In this embodiment, in step S3, lamination, drilling, copper plating, and electroplating are performed on the PCB board. The HDI board requires at least two laminations. The backlight level of the copper plating is >9. During blind hole electroplating, it is necessary to fill the holes as much as possible and control the dimple degree to be <15um.

[0064] In this embodiment, the etching solution used in step S4 is sodium persulfate solution, and all circuits on the outer layer of the PCB board are fabricated, including the gold finger leads of the unit, such as... Figure 2-4 This can be used to create standard gold fingers, long and short gold fingers, or segmented gold fingers.

[0065] In step S7, after the characters are produced, the process is transferred to the solder mask screen printing wet film. The production parameters of the screen printing wet film are compared with existing technologies using DOE (Design of Experiments) tests. The specific data are shown in Table 1.

[0066] Table 1. DOE Comparison Test Data

[0067]

[0068] As shown in Table 1, this invention performs DOE comparative tests on the production parameters of the screen printing wet film process. Therefore, in the production of solder resist wet film, the wet film thickness is 40µm, after screen printing, it needs to stand for 15-20 minutes, pre-baking at 75℃ for 15-35 minutes, the exposure energy is 9-10 divisions, the film expansion and contraction is controlled within + / -0.025mm, after development, it is air-exposed and then exposed to 200mJ energy or baked with UV once. Under these process parameters, the first pass rate in the production process is improved, and the finished product yield is above 92% or even reaches 97%, which is gradually improved and maintained stably.

[0069] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A manufacturing process for three-sided gold-plated fingers, characterized in that, The specific process includes the following steps: S1: From material cutting to pretreatment of inner core board, wet film coating, exposure, development and etching, to complete the pattern transfer of inner layer circuit, then to inner layer AOI inspection and punching out rivet holes, and then to lamination production. S2: The inner core board undergoes pretreatment browning, then PP is cut, pre-stacked, and then the boards are arranged for the outermost layer pressing production. If multiple pressing is required, the production is carried out in multiple cycles between the five processes of laser / drilling → electroplating → circuit → AOI → pressing. S3: The PCB board produced from the final lamination is then transferred to laser or drilling processing. ， Then, the holes are metallized and made conductive by copper plating, followed by filling of blind holes and electroplating of the entire board for through holes. S4: After electroplating, the PCB board will undergo pattern transfer processing of the outer layer circuit. The pattern transfer process is as follows: pretreatment - lamination - exposure - development - etching - stripping. During the pattern transfer process, the gold finger guide lines of the unit will be made. At the same time, during the pattern transfer process, it is important to ensure that the dry film is not pressed off-center during lamination. Copper must be left at the board edge >1mm. After etching, the board will be transferred to AOI for inspection and repair. S5: PCBs that have passed inspection are transferred to solder mask production. The solder mask production process is as follows: pretreatment - silkscreen printing / spraying - pre-baking - exposure - development. Specifically: After the roughened copper surface and cleaned board surface are pretreated, the solder resist ink is evenly coated on the PCB board by screen printing or spraying. After pre-baking, it is exposed and developed. Note that the solder resist ink is not completely covered on the false exposure and the edge of the PCB board. At the same time, the gold finger guide line in the unit is opened out. S6: After the PCB board for solder mask production is completed, the characters are produced. The characters are silkscreened and the thickness of the characters is controlled to be <30um. Then the impedance test is performed. S7: After character production is complete, proceed to solder resist screen printing wet film. The solder resist screen printing wet film process is: pretreatment - screen printing - pre-baking - exposure - development - air exposure / UV baking - AVI, specifically: The pretreatment only involves acid washing, controlling the thickness of the screen printing wet film, the pre-baking temperature and time, and the exposure energy. After development, it needs to be air-exposed or UV-baked, and then transferred to AVI for inspection. After scanning, the residual adhesive, foreign matter and dirt on the copper surface of the gold fingers are manually scraped off. S8: After AVI repair, the PCB is transferred to the outer layer for gold plating dry film. Without pretreatment, the film is directly laminated, then exposed and developed to cover the areas that do not need gold plating. Then it is transferred to the surface treatment for nickel-gold plating of the gold fingers. S9: After the gold fingers are plated, the PCB board is transferred to the outer layer for dry film and wet film removal. Then, without pretreatment, the dry film of the leads is etched, exposed, developed and etched. The leads are completely etched away, and then the film is removed. Then, without pretreatment, the selective dry film is directly etched, exposed and developed. After development, it is transferred to the surface treatment to complete selective gold plating. Then the film is removed again, followed by molding, electrical testing and final inspection processes.

2. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S2, when cutting PP, if the PP is high-density rubber or multiple PP sheets or multiple core boards are pressed together, hot melting and riveting operations are performed.

3. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: The gold fingers mentioned include ordinary gold fingers with fingers of the same length and aligned, gold fingers with varying lengths within a unit, and segmented fingers with fingers divided into one or more segments within a unit.

4. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S1, inner layer processing is performed on the PCB board, and 6-8 rivet holes are punched out.

5. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S3, lamination, drilling, copper plating, and electroplating are performed on the PCB board. The HDI board requires at least two laminations. The backlight level of the copper plating is >9. The blind holes are filled during electroplating, and the dimple is controlled to be <15um.

6. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S4, the etching solution used during etching is sodium persulfate solution, and all circuits on the outer layer of the PCB board are fabricated, including the gold fingers of the unit with external leads, forming ordinary gold fingers, long and short gold fingers, or segmented gold fingers.

7. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S5 of the solder resist production process, the area of ​​the board edge not covered by the solder resist ink must be >2mm.

8. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S7, the wet film thickness is 40-50µm during solder resist wet film production. After screen printing, it needs to stand for 15-20 minutes, pre-baking at 70-75℃ for 15-35 minutes, exposure energy of 9-10 divisions, and the film expansion and contraction controlled within + / -0.025mm. After development, it is air-exposed and then exposed to 200mJ energy or UV-baked once.

9. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S8, the current during the nickel-gold electroplating process is <2.5A.

10. The manufacturing process of the three-sided gold-plated finger according to claim 1, characterized in that: In step S9, the dewetting film and dry film after electroplating nickel and gold are produced at a linear speed of 0.5-0.8 m / min. The etching lead solution is an ammonium chloride solution, and lead residue is not allowed. The lateral etching amount is <0.025 mm. The three defilm removal solutions are all sodium hydroxide solutions.

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