Control method for preventing plating leakage in PCB (Printed Circuit Board) electroless gold plating

Abstract

The invention relates to a control method for preventing skip plating in PCB electroless gold plating, which is characterized in that a deburring process is added before needle brush treatment in a board grinding process in an electroplating process, three groups of needle brush board grinding processing are adopted, and grinding crack parameters, water breaking parameters and board surface roughness in the electroplating process, a circuit process and a solder mask process are respectively controlled. Key process parameters are controlled in the copper deposition and electroplating processes, angle parameters and pressure parameters of a hole plugging cutter are controlled in the hole plugging process, grinding crack parameters, micro-etching amount, sand blasting sand content and water breaking parameters are controlled in the chemical gold pretreatment process, and key process parameters in the whole chemical gold process are controlled; and in the chemical gold post-treatment procedure, the plate placing speed, the pickling concentration, the liquid medicine spraying pressure parameter, the ultrasonic power and the drying temperature are controlled. Through a series of control, compared with an existing technological method, the production qualification rate is increased by 24-30%. According to the invention, the production cost is reduced, the product quality is improved, and the quality guarantee is provided for users.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB board production, and in particular to a control method for preventing leakage plating of gold on a PCB board. Background Art

[0002] The surface treatment of PCB boards (printed circuit boards) is a gold plating process. During the production process, unclean copper surfaces and chemicals hidden in the holes will lead to gold plating leakage, which will seriously affect the quality of the product. At the same time, there are functional risks such as poor tinning, which must be strictly controlled.

[0003] The existing gold-making process mainly includes the following processes: 1. Electroplating process: In this process, only a needle brush is used for grinding the plate, and the burr of the hole of the PCB board is not removed. Ordinary electroplating is used during electroplating, and the hole nodules are present, and the deep plating ability is poor (only 80%), which will cause poor subsequent plugging. 2. Anti-soldering process: In this process, the plugging and printing are used together, which may cause the plugging to be incomplete, poor plugging and cracks; 3. Text process: In this process, a vertical oven is used to bake the plate after printing the text, which is not very efficient; 4. Metallization process: In this process, the wear scar test width of the pre-treatment is 6-11mm, the micro-etching depth is 0.6-1.2um, and the sand content of sand blasting (280 mesh) is: (17+ / -3)%.

[0004] According to the above-mentioned existing electroless gold process, there will be electroless gold plating leakage, resulting in a low PCB board qualification rate and an increase in the amount of rework.

[0005] In order to solve the above problems, this solution proposes a control method for preventing gold plating leakage on PCB boards. Summary of the invention

[0006] The invention aims to solve the problem that the existing chemical gold process has deficiencies that cause chemical gold leakage, resulting in low PCB board qualification rate and increased rework. The specific solution is as follows: A control method for preventing leakage plating of PCB board gold is carried out according to the following steps: Step 1: In the electroplating process, a deburring machine is added before the needle brushing process when grinding the board to deburr the PCB board openings. The grinding needle brushing is performed in three groups to control the wear mark parameters, water breakage parameters and board surface roughness after grinding. There are no glue stains and pollutants on the PCB board surface. The copper deposition process controls the backlight parameters, micro-etching rate, adhesive removal rate and copper deposition rate respectively; The electroplating process uses pulse electroplating. The current parameters are set according to the required copper thickness. After the electroplated board comes out, the color of the board surface is uniform and bright, and the copper on the sliced hole surface meets the requirements. In step 2, in the circuit process, the pre-treatment process controls the grinding mark parameters, water break parameters, and board surface roughness after grinding respectively. There are no glue stains, pollutants, and water marks on the PCB board surface. The film laminating process controls the temperature parameter and the film laminating pressure parameter respectively. There are no wrinkles and bubbles during film laminating. In the exposure process, the exposure scale is 6 - 8 grids, and there are no exposure defects. In the developing process, the developing point test is at 45 - 55%, and after development, a copper chloride test is performed and there is no incomplete development. The etching process is carried out according to the circuit design specifications. After etching, the line width, IC, PAD, impedance, and insertion loss of the PCB board should meet the design requirements. In step 3, in the solder mask process, the grinding mark parameters, water break parameters, and board surface roughness are controlled during grinding. There are no glue stains, pollutants, and water marks on the PCB board surface. In the via filling process, special via filling ink and clean and pollution-free special backing plates are used. A special via filling machine is adopted to control its via filling knife angle parameter and pressure parameter. It is necessary to confirm that there is ink oozing out of the hole after via filling. The pre-baking temperature is 75°C * 45 min; the via filling fullness ≥ 70%, and there are no cracks in the via filling ink in the holes connecting the pads. When exposing and developing after printing the solder mask surface oil, confirm that the developing point test is at 45 - 55%. At the same time, the first production board needs to be tested with copper chloride, and there is no incomplete development. In step 4, in the text and baking process, the board is baked using a tunnel oven after the text. The tunnel oven should be maintained before baking and its exhaust air volume should be measured and controlled. In step 5, in the immersion gold process, in the pre-treatment process before immersion gold, the grinding mark parameters, micro-etching amount, sandblasting sand content, and water break parameters are controlled. There are no water stains, oil stains, and abnormalities on the PCB board surface. In the immersion gold process, the temperature and cleaner concentration are controlled during degreasing. After degreasing, there are no oil stains and pollutants on the PCB board surface; the micro-etching amount is controlled, and after the board surface is roughened, the copper surface color is uniform and there are no foreign matters. The pre-immersion acid equivalent is 0.15 - 0.25 N; the activated Pd concentration, acidity, copper ion, and temperature are controlled; the chemical nickel Ni concentration, PH value, NaH2PO2 concentration, and temperature are controlled. The rated voltage is 0.9 V, the protection current < 1 A, the life ≤ 4.0 MTO, and the pressure of the filter is 0.3 - 0.9 kg / cm 2;After electroless nickel plating, the sterilizing lamp needs to be turned on during the water washing process to prevent the inner layer and gold layer from peeling off due to fungal contamination; in the gold plating bath, the Au+ concentration is 0.4 - 0.5 g / l, the pH is controlled at 4.3 - 5, Ni2+ ≤ 600 PPM, Cu2+ < 5 PPM, the temperature is controlled at 83 - 87 °C, and the pressure of the filtration pump is 0.2 - 0.6 kg / cm 2 ;The sterilizing lamp should be normally turned on for gold recovery; after gold plating, the temperature of the hot water wash is controlled at 25 - 35 °C, and the water inlet flow rate is controlled at 10 - 60 L / H; In the post-treatment process of gold plating, control the plate loading speed, pickling concentration, spray pressure parameter of the chemical solution, ultrasonic power, and drying temperature; after the PCB board comes out, the board surface should be clean, free of water stains and foreign objects; Step 6: Detect the thickness of gold and nickel, and there is no missing plating on the board surface.

[0007] Furthermore, in step 1, The burr remover uses 800-mesh sandpaper. The method of using the grinding needle brush in three groups is to first use a group of 320-mesh needle brushes to grind the board, and then use two groups of 500-mesh needle brushes to grind the board respectively; The method of controlling the scratch mark parameter, water break parameter, and board surface roughness after grinding the board is as follows: the scratch mark is controlled at 8 - 14 mm, the water break test after grinding the board is 45 seconds, and the board surface roughness is Ra: 0.2 - 0.5 um, Rz: 1.5 - 4 um; The method of controlling the backlight parameter, micro-etching rate, desmearing rate, and electroless copper plating rate in the electroless copper plating process is as follows: the backlight for electroless copper plating is controlled at ≥ 9 levels, the micro-etching rate is 0.8 - 1.2 um, the desmearing rate is 0.1 - 0.5 mg / cm 2 , and the electroless copper plating rate is 0.35 - 0.55 um.

[0008] Furthermore, in step 2, The method of controlling the scratch mark parameter, water break parameter, and board surface roughness after grinding the board in the pretreatment process is as follows: the scratch mark is controlled at 8 - 14 mm, the water break test after grinding the board is 45 seconds, and the roughness is Ra: 0.2 - 0.5 um, Rz: 1.5 - 3 um; The method of controlling the temperature parameter and film laminating pressure parameter in the film laminating process is as follows: the temperature is controlled at 110 ± 10 °C, and the film laminating pressure is controlled at 3 - 5 kg / cm 2 .

[0009] Furthermore, in step 3, In the solder mask process, the method of controlling the scratch mark parameter, water break parameter, and board surface roughness during grinding is as follows: the scratch mark of grinding the board is controlled at 8 - 14 mm, the water break test after grinding the board is 45 seconds, and the board surface roughness is Ra: 0.15 - 0.4 um, Rz: 1.5 - 3 um; The method for controlling the angle parameter and pressure parameter of the plug hole knife is as follows: the angle of the plug hole knife is controlled at 8 - 13° (degrees), and the pressure is controlled at 5 - 15 kg / cm 2 .

[0010] Further, in step 3, if cracks and incompleteness occur in the plug hole ink in the hole at the position of the connection pad and cannot be solved, then one of the following methods is used for substitution: Change the ink plug hole method to a resin plug hole method. The resin plug hole fullness can meet the requirements and there is no allowable phenomenon of cracks in the resin oil in the hole after curing; Or design the hole that needs to be plugged with ink into a non-plugged through hole.

[0011] Further, in step 4, the method for maintaining the tunnel baking oven and measuring and controlling its air extraction volume before baking is as follows: confirm that there is no oil dripping, dirt, and abnormal phenomena in the tunnel baking oven, and the air extraction volume is controlled at 8 - 12 m / min.

[0012] Further, in step 5, The method for controlling the scratch mark parameter, micro-etching amount, sand content of sandblasting, and water break parameter in the pre-treatment process of immersion gold is as follows: the scratch mark is controlled at 8 - 14 mm, the micro-etching amount is controlled at: 0.8 - 1.5 um, 280 - mesh sand is used for sandblasting, and the sand content is: (20 ± 5)%; the water break test is: 45 seconds; In the immersion gold process, the method for controlling the temperature and cleaner concentration during degreasing is as follows: the degreasing control temperature is at 37 - 43 °C, and the cleaner concentration is controlled at 40 - 60 ml / l.

[0013] Further, in step 5, The controlled micro-etching amount is: 0.4 - 0.9 um; The method for controlling the activated Pd concentration, acidity, copper ions, and temperature is as follows: the activated Pd concentration is controlled at 8 - 10 PPM, the acidity is controlled at 0.2 - 0.35 N, the copper ions ≤ 120 PPM, and the temperature is controlled at 26 - 30 °C.

[0014] Further, the method for controlling the chemical nickel Ni concentration, PH value, NaH2PO2 concentration, and temperature in step 5 is as follows: the chemical nickel Ni concentration is controlled at 4.5 - 5.2 g / l, the PH is controlled at 4.1 - 4.8, the NaH2PO2 concentration is controlled at 20 - 34 g / l, and the temperature is controlled at 80 - 84 °C.

[0015] Further, in the post-treatment process of gold plating, the methods for controlling the board feeding speed, pickling concentration, chemical solution spraying pressure parameter, ultrasonic power, and drying temperature are as follows: the board feeding speed is controlled at 3 - 4 m / min; the pickling concentration is controlled at 3 - 6%; the chemical solution spraying pressure is controlled at 1 - 2 kg / cm2; the ultrasonic power is controlled at 80 - 100%; and the drying temperature is controlled at 80 - 90 °C.

[0016] In summary, the technical solution of the present invention has the following beneficial effects: The present invention solves the problem of insufficient gold plating in the existing gold plating process, which causes gold plating omission, resulting in a low qualified rate of PCB boards and an increase in rework volume. In the grinding process of the electroplating process of the present invention, a deburring process using 800-mesh sandpaper is added before the needle brush treatment, and three groups of needle brushes (one group of 240 mesh + two groups of 320 mesh) are used for grinding plate processing, effectively controlling the grinding mark parameters, water break parameters, and board surface roughness in the electroplating process, circuit process, and solder mask process. The key process parameters are controlled in the copper deposition and electroplating processes. In the plug hole process, special plug hole ink and special backing plates are used, and a special plug hole machine is used to control the plug hole tool angle parameter and pressure parameter. In the baking process, a tunnel oven is used for baking, improving the baking efficiency, and the tunnel oven is maintained and its exhaust air volume is controlled before baking; in the gold plating process, in the pre-treatment process of gold plating, the grinding mark parameters, micro-etching amount, sandblasting sand content, and water break parameters are controlled, and the key process parameters in the whole process of the gold plating process are controlled. In the post-treatment process of gold plating, the board feeding speed, pickling concentration, chemical solution spraying pressure parameter, ultrasonic power, and drying temperature are controlled. After this series of control measures, compared with the existing process method, the production qualified rate of PCB board gold plating production using the new process control method of the present invention has been significantly improved: from the yield rate of 68 - 75% of the existing process to the yield rate of 98 - 99% of the new process, that is, the qualified rate has increased by 24 - 30%. The present invention reduces the production cost of the factory, improves the quality of PCB board products, and provides quality assurance for PCB board users. Specific Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0018] A control method for preventing gold plating omission on a PCB board is carried out according to the following steps: Step 1, in the electroplating process, add a deburring machine before the needle brushing process during the panel grinding process to deburr the orifices of the PCB boards. The panel grinding needle brushing is carried out in three groups to control the grinding mark parameters, water break parameters, and surface roughness after panel grinding. There are no glue stains and contaminants on the surface of the PCB boards. During the electroless copper plating process, control the backlight parameters, micro-etching rate, glue removal rate, and electroless copper plating rate respectively. During the electroplating process, pulse electroplating is used. Set the current parameters according to the copper thickness requirements. After the electroplated boards come out, the surface color is uniform and bright, and the copper in the sliced holes meets the requirements. Step 2, in the circuit process, during the pretreatment process, control the grinding mark parameters, water break parameters, and surface roughness after panel grinding. There are no glue stains, contaminants, and water marks on the surface of the PCB boards. During the film laminating process, control the temperature parameters and film laminating pressure parameters respectively. There are no wrinkles and bubbles during film laminating. During the exposure process, expose at 6 - 8 grids of the exposure scale, and there are no exposure defects. During the developing process, the developing point test is at 45 - 55%, and after developing, perform a copper chloride test and there is no incomplete development. During the etching process, carry out according to the circuit design specifications. After etching, the line width, IC, PAD, impedance, and insertion loss of the PCB boards should meet the design requirements. Step 3, in the solder mask process, during the panel grinding process, control the grinding mark parameters, water break parameters, and surface roughness. There are no glue stains, contaminants, and water marks on the surface of the PCB boards. During the via filling process, use special via filling ink and clean and pollution-free special backing plates, and adopt a special via filling machine to control the via filling knife angle parameters and pressure parameters. After the ink is filled into the vias, it is necessary to confirm that there is ink oozing out of the orifices. The pre-baking temperature is 75°C * 45 min (minutes); the via filling fullness ≥ 70%, and there are no cracks in the via filling ink in the holes connecting to the pads. When performing exposure and development after the solder mask surface oil is printed, confirm that the developing point test is at 45 - 55%. At the same time, when producing the first board, perform a copper chloride test and there is no incomplete development. Step 4, in the text and baking process, use a tunnel oven to bake the boards after the text process. Before baking, the tunnel oven should be maintained and its exhaust air volume should be measured and controlled. Step 5, in the immersion gold process, during the pretreatment process before immersion gold, control the grinding mark parameters, micro-etching amount, sand content of sandblasting, and water break parameters. There are no water marks, oil stains, and abnormalities on the surface of the PCB boards. Gold plating process: Control the temperature and cleaner concentration during degreasing. After degreasing, the PCB board surface should be free of oil stains and contaminants. Control the micro-etching amount. After the board surface is roughened, the copper surface color should be uniform without foreign objects, and the pre-immersion acid equivalent is 0.15 - 0.25N (equivalent). Control the activation Pd (palladium) concentration, acidity, copper ions and temperature. Control the chemical nickel Ni concentration, pH value, NaH2PO2 concentration and temperature. The rated voltage is 0.9V, the protection current < 1A, the life ≤ 4.0MTO, and the filter pressure is 0.3 - 0.9kg / cm 2 ; After nickel plating, turn on the germicidal lamp during water washing to prevent the inner layer and gold layer from peeling due to fungal contamination. The Au+ concentration in the gold plating bath is 0.4 - 0.5g / l (grams per liter), the pH is controlled at 4.3 - 5, Ni2+ ≤ 600PPM, Cu2+ < 5PPM, the temperature is controlled at 83 - 87°C, and the filter pump pressure is 0.2 - 0.6kg / cm 2 ; Turn on the germicidal lamp normally during gold recovery. After gold plating, control the hot water washing temperature at 25 - 35°C and the water inlet flow rate at 10 - 60L / H (liters per hour); Post-gold plating treatment process: Control the plate loading speed, pickling concentration, chemical solution spraying pressure parameters, ultrasonic power and drying temperature. After the board is taken out, the PCB board surface should be clean, free of water stains and foreign objects; Step 6: Detect the thickness of gold and nickel, and there should be no missing plating on the board surface.

[0019] Specifically, in step 1, Use 800-mesh sandpaper for the burr remover. The method of using the grinding plate needle brush in three groups is to first use a group of 320-mesh needle brushes to grind the board, and then use two groups of 500-mesh needle brushes to grind the board respectively; The methods for controlling the grinding mark parameters, water break parameters and board surface roughness after grinding are as follows: The grinding marks are controlled within 8 - 14mm, the water break test after grinding is 45 seconds, and the board surface roughness is Ra: 0.2 - 0.5um, Rz: 1.5 - 4um; (Note: Ra is the abbreviation of Roughness Average, representing the arithmetic mean deviation of the profile. Rz is the ten-point height of micro-irregularities, which refers to the sum of the average value of the five largest profile peak heights and the average value of the five largest profile valley depths within the sampling length.) The methods for controlling the backlight parameters, micro-etching rate, desmearing rate and copper deposition rate in the copper deposition process are as follows: The copper deposition is controlled with a backlight ≥ 9 levels, the micro-etching rate is 0.8 - 1.2um, the desmearing rate is 0.1 - 0.5mg / cm 2 , and the copper deposition rate is 0.35 - 0.55um.

[0020] Specifically, in step 2, The methods for controlling the scratch parameters, water break parameters, and board surface roughness respectively in the pretreatment process are as follows: the scratch is controlled within 8 - 14 mm, the water break test is conducted for 45 seconds after board grinding, and the surface roughness is Ra: 0.2 - 0.5 um, Rz: 1.5 - 3 um; The methods for controlling the temperature parameter and the film laminating pressure parameter respectively in the film laminating process are as follows: the temperature is controlled at 110 ± 10 °C, and the film laminating pressure is controlled at 3 - 5 kg / cm 2 .

[0021] Specifically, in step 3, In the solder mask process, the methods for controlling the scratch parameters, water break parameters, and board surface roughness during board grinding are as follows: the scratch of the ground board is controlled within 8 - 14 mm, the water break test is conducted for 45 seconds after board grinding, and the board surface roughness is Ra: 0.15 - 0.4 um, Rz: 1.5 - 3 um; The methods for controlling the plug hole cutter angle parameter and the pressure parameter are as follows: the plug hole cutter angle is controlled at 8 - 13° (degrees), and the pressure is controlled at 5 - 15 kg / cm 2 .

[0022] Specifically, in step 3, if there are cracks and non - fullness in the plug hole ink in the holes connecting the pad positions and it cannot be solved, then one of the following methods is adopted for substitution: Change the ink plug hole method to the resin plug hole method. The fullness of the resin plug hole should meet the requirements and there should be no crack phenomenon after the resin oil in the hole is cured; Or design the holes that need to be ink - plugged into non - plugged through - holes.

[0023] Specifically, in step 4, the method for maintaining the tunnel oven and measuring and controlling its exhaust air volume before baking the board is as follows: confirm that there is no oil dripping, dirt, and abnormal phenomenon in the tunnel oven, and the exhaust air volume is controlled at 8 - 12 m / min.

[0024] Specifically, in step 5, In the pretreatment process before immersion gold plating, the methods for controlling the scratch parameters, micro - etching amount, sand content in sandblasting, and water break parameters are as follows: the scratch is controlled within 8 - 14 mm, the micro - etching amount is controlled at: 0.8 - 1.5 um, 280 - mesh sand is used for sandblasting, and the sand content is: (20 ± 5)%, and the water break test is: 45 seconds; In the immersion gold plating process, the methods for controlling the temperature and the concentration of the cleaning agent during degreasing are as follows: the degreasing temperature is controlled at 37 - 43 °C, and the concentration of the cleaning agent is controlled at 40 - 60 ml / l (milliliters per liter).

[0025] Specifically, in step 5, Control the micro - etching amount to be: 0.4 - 0.9 um; The method for controlling the activated Pd concentration, acidity, copper ions and temperature is as follows: the activated Pd concentration is controlled at 8 - 10 PPM, the acidity is controlled at 0.2 - 0.35 N (equivalent), the copper ions ≤ 120 PPM, and the temperature is controlled at 26 - 30 °C.

[0026] Specifically, the method for controlling the electroless nickel Ni concentration, pH value, NaH2PO2 concentration and temperature in step 5 is as follows: the electroless nickel Ni concentration is controlled at 4.5 - 5.2 g / l (grams per liter), the pH is controlled at 4.1 - 4.8, the NaH2PO2 concentration is controlled at 20 - 34 g / l (grams per liter), and the temperature is controlled at 80 - 84 °C.

[0027] Specifically, in the post-treatment process of gold plating in step 5, the method for controlling the plate loading speed, pickling concentration, chemical solution spraying pressure parameters, ultrasonic power and drying temperature is as follows: the plate loading speed is controlled at 3 - 4 m / min; the pickling concentration is controlled at 3 - 6%, the chemical solution spraying pressure is controlled at 1 - 2 kg / cm 2 , the ultrasonic power is controlled at 80 - 100%; the drying temperature is controlled at 80 - 90 °C.

[0028] Using the new process control method of the present invention, compared with the existing process method, the production qualified rate of PCB board gold plating production has been significantly improved. As shown in the following table, we respectively selected three different specifications of PCB boards: namely, 41936 type board, 46372 type board, 35384 type board, and 50 PCB boards of each type were used for the comparative test of the new process and the existing process. The results are as follows: Comparative Test Table

[0029] It can be seen from the table that the yield rate has increased from 68 - 75% of the existing process to 98 - 99% of the new process, that is, the qualified rate has increased by 24 - 30%.

[0030] Special note: (1) The control method of this solution only shows the process step content related to controlling the gold plating omission, and is not the entire gold plating process content, because the content of other process steps is prior art. (2) Starting from the material cost and actual needs, the gold plating process of this solution is to plate gold on the basis of prior nickel plating, which not only reduces the cost, but also has stronger adhesion. These are also common practices in this industry.

[0031] In summary, adopting the technical solution of the present invention has the following beneficial effects: The present invention solves the problem of gold immersion leakage caused by the deficiencies in the existing gold immersion process, resulting in a low qualified rate of PCB boards and an increase in rework volume. In the grinding process of the electroplating process of the present invention, a deburring process using 800-mesh sandpaper is added before the needle brushing treatment, and three groups of needle brushes (one group of 240 mesh + two groups of 320 mesh) are used for grinding plate processing, effectively controlling the grinding mark parameters, water break parameters, and board surface roughness in the electroplating process, circuit process, and solder mask process. The key process parameters are controlled in the copper deposition and electroplating processes. In the plugging process, special plugging ink and special backing plates are used, and a special plugging machine is adopted to control the plugging tool angle parameters and pressure parameters. In the baking process, a tunnel oven is used for baking, improving the baking efficiency, and the tunnel oven is maintained and its air extraction volume is controlled before baking; in the gold immersion process, in the pre-treatment process before gold immersion, the grinding mark parameters, micro-etching amount, sandblasting sand content, and water break parameters are controlled, and the key process parameters in the whole process of the gold immersion process are controlled. In the post-treatment process after gold immersion, the plate placing speed, pickling concentration, liquid medicine spraying pressure parameters, ultrasonic power, and drying temperature are controlled. After this series of control measures, compared with the existing process method, the new process control method adopted by the present invention has significantly improved the production qualified rate of PCB board gold immersion production: the qualified rate has increased from 68 - 75% of the existing process to 98 - 99% of the new process, that is, the qualified rate has increased by 24 - 30%. The present invention reduces the production cost of the factory, improves the quality of PCB board products, and provides quality assurance for PCB board users.

[0032] The above-described embodiments do not constitute a limitation on the protection scope of the technical solution. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the above-described embodiments shall be included in the protection scope of the technical solution.

Claims

1. A control method for preventing missing plating in PCB immersion gold plating, characterized in that, Proceed as follows: Step 1: In the electroplating process, add a deburring machine before the needle brushing process during the panel grinding to deburr the PCB hole openings. The panel grinding needle brushing is carried out in three groups, respectively controlling the grinding mark parameters, water break parameters, and board surface roughness after grinding. There are no glue stains and contaminants on the PCB board surface; In the electroless copper plating process, control the backlight parameters, micro-etching rate, desmearing rate, and electroless copper plating rate respectively; In the electroplating process, pulse electroplating is used. Set the current parameters according to the copper thickness requirements. After the electroplated board comes out, the board surface color is uniform and bright, and the copper in the sliced hole surface meets the requirements; Step 2: In the circuit process, in the pretreatment process, control the grinding mark parameters, water break parameters, and board surface roughness after grinding respectively. There are no glue stains, contaminants, and water marks on the PCB board surface; In the film laminating process, control the temperature parameters and film laminating pressure parameters respectively. There are no wrinkles and bubbles during film laminating; In the exposure process, the exposure scale is 6 - 8 grids, and there are no exposure defects; In the developing process, the developing point test is at 45 - 55%, and after developing, a cupric chloride test is done with no incomplete development; In the etching process, it is carried out according to the circuit design specifications. After etching, the line width, IC, PAD, impedance, and insertion loss of the PCB board should meet the design requirements; Step 3: In the solder mask process, during panel grinding, control the grinding mark parameters, water break parameters, and board surface roughness. There are no glue stains, contaminants, and water marks on the PCB board surface; In the via filling process, use special via filling ink and a clean and pollution-free special backing plate, adopt a special via filling machine, control its via filling knife angle parameters and pressure parameters. After via filling, it is necessary to confirm that the ink oozes out of the hole openings; The pre-baking temperature is 75°C * 45 min; the via filling fullness ≥ 70%, and there are no cracks in the via filling ink in the holes connecting to the pads; When exposing and developing after printing the solder mask surface oil, confirm that the developing point test is at 45 - 55%. At the same time, when producing the first board, a cupric chloride test is required with no incomplete development; Step 4: In the legend and baking process, use a tunnel oven to bake the board after legend. Before baking, the tunnel oven should be maintained and its extraction air volume should be measured and controlled; Step 5: In the immersion gold process, in the pretreatment process before immersion gold, control the grinding mark parameters, micro-etching amount, sandblasting sand content, and water break parameters. There are no water stains, oil stains, and abnormalities on the PCB board surface; Gold plating process, control the temperature and cleaner concentration during degreasing, and there should be no oil stains and contaminants on the surface of the PCB board after degreasing; control the micro-etching amount, the color of the copper surface is uniform and there are no foreign objects after the board surface is roughened, and the pre-immersion acid equivalent is 0.15 - 0.25N; control the activation Pd concentration, acidity, copper ions and temperature; control the chemical nickel Ni concentration, pH value, NaH2PO2 concentration and temperature, the rated voltage is 0.9V, the protection current < 1A, the life ≤ 4.0MTO, and the pressure of the filter is 0.3 - 0.9kg / cm 2 ; After electroless nickel plating, turn on the germicidal lamp during water washing to prevent the inner layer and gold layer from peeling off due to fungal contamination; the Au+ concentration in the gold plating bath is 0.4 - 0.5g / l, the pH is controlled at 4.3 - 5, Ni2+ ≤ 600PPM, Cu2+ < 5PPM, the temperature is controlled at 83 - 87°C, and the pressure of the filter pump is 0.2 - 0.6kg / cm 2 ; Turn on the germicidal lamp normally during gold recovery; the temperature of hot water washing after gold plating is controlled at 25 - 35°C, and the water inlet flow rate is controlled at 10 - 60L / H; In the post-treatment process after immersion gold, control the board placing speed, pickling concentration, chemical solution spraying pressure parameters, ultrasonic power, and drying temperature; after the board comes out, the PCB board surface is clean, without water stains and foreign objects; Step 6: Detect the gold and nickel thickness, and there is no non-plating phenomenon on the board surface.

2. The control method for preventing non-plating on PCB immersion gold according to claim 1, characterized in that, In Step 1, The deburring machine uses 800-mesh sandpaper. The method of carrying out the panel grinding needle brushing in three groups is to first use a group of 320-mesh needle brushes to grind the board and then use two groups of 500-mesh needle brushes to grind the board respectively; The method of respectively controlling the grinding mark parameters, water break parameters, and board surface roughness after grinding is: the grinding marks are controlled at 8 - 14 mm, the water break test after grinding is 45 seconds, and the board surface roughness is Ra: 0.2 - 0.5 μm, Rz: 1.5 - 4 μm; The method for controlling the backlight parameter, micro-etching rate, degumming rate, and copper deposition rate in the copper deposition process is as follows: the backlight for copper deposition is controlled to be ≥9 levels, the micro-etching rate is 0.8 - 1.2 μm, the degumming rate is 0.1 - 0.5 mg / cm 2 , and the copper deposition rate is 0.35 - 0.55 μm.

3. The control method for preventing non-plating on PCB immersion gold according to claim 1, characterized in that, In Step 2, The methods for controlling the scratch parameters, water break parameters, and board surface roughness in the pretreatment process are as follows: the scratch is controlled within 8 - 14 mm, the water break test after board grinding is 45 seconds, and the roughness is Ra: 0.2 - 0.5 um, Rz: 1.5 - 3 um; The method for controlling the temperature parameter and the film laminating pressure parameter in the film laminating process is as follows: the temperature is controlled at 110 ± 10 °C, and the film laminating pressure is controlled at 3 - 5 kg / cm 2 .

4. The control method for preventing non-plating on PCB immersion gold according to claim 1, characterized in that, In step 3, In the solder mask process, the methods for controlling the scratch parameters, water break parameters, and board surface roughness during board grinding are as follows: the scratch of the board grinding is controlled within 8 - 14 mm, the water break test after board grinding is 45 seconds, and the board surface roughness is Ra: 0.15 - 0.4 um, Rz: 1.5 - 3 um; The method for controlling the angle parameter and pressure parameter of the plug hole knife is as follows: the angle of the plug hole knife is controlled to be 8-13°, and the pressure is controlled to be 5-15 kg / cm 2 .

5. The control method for preventing non-plating on PCB immersion gold according to claim 1, wherein In step 3, if cracks and non - fullness occur in the hole plugged with hole - filling ink at the position of the connection pad and cannot be solved, then one of the following methods is used for substitution: Change the ink hole - plugging method to a resin hole - plugging method. The resin hole - plugging fullness should meet the requirements, and there should be no cracks after the resin oil in the hole cures; Or design the holes that need to be plugged with ink into non - plugged through - holes.

6. The control method for preventing non-plating of PCB immersion gold according to claim 1, wherein In step 4, the methods for maintaining the tunnel oven and measuring and controlling its exhaust air volume before baking are as follows: confirm that there is no oil dripping, dirt, or abnormality in the tunnel oven, and the exhaust air volume is controlled at 8 - 12 m / min.

7. The control method for preventing non-plating leakage in PCB immersion gold according to claim 1, characterized in that In step 5, In the gold plating pretreatment process, the methods for controlling the scratch parameters, micro - etching amount, sand content of sandblasting, and water break parameters are as follows: the scratch is controlled within 8 - 14 mm, the micro - etching amount is controlled at 0.8 - 1.5 um, 280 - mesh sand is used for sandblasting, the sand content is: (20 ± 5)%, and the water break test is: 45 seconds; In the gold plating process, the methods for controlling the temperature and cleaner concentration during degreasing are as follows: the degreasing temperature is controlled at 37 - 43 °C, and the cleaner concentration is controlled at 40 - 60 ml / l.

8. The control method for preventing non-plating leakage of PCB immersion gold according to claim 1, characterized in that, In step 5, The controlled micro - etching amount is: 0.4 - 0.9 um; The methods for controlling the activated Pd concentration, acidity, copper ions, and temperature are as follows: the activated Pd concentration is controlled at 8 - 10 PPM, the acidity is controlled at 0.2 - 0.35 N, the copper ions ≤ 120 PPM, and the temperature is controlled at 26 - 30 °C.

9. A control method for preventing non-plating on PCB immersion gold according to claim 1, characterized in that, The methods for controlling the chemical nickel Ni concentration, PH value, NaH2PO2 concentration, and temperature in step 5 are as follows: the chemical nickel Ni concentration is controlled at 4.5 - 5.2 g / l, the PH is controlled at 4.1 - 4.8, the NaH2PO2 concentration is controlled at 20 - 34 g / l, and the temperature is controlled at 80 - 84 °C.

10. The control method for preventing non-plating on PCB immersion gold according to claim 1, characterized in that, For the post-treatment process of gold plating described in Step 5, the methods for controlling the plate feeding speed, pickling concentration, chemical solution spraying pressure parameters, ultrasonic power, and drying temperature are as follows: the plate feeding speed is controlled at 3 - 4 m / min; the pickling concentration is controlled at 3 - 6%; the chemical solution spraying pressure is controlled at 1 - 2 kg / cm 2 , the ultrasonic power is controlled at 80 - 100%; the drying temperature is controlled at 80 - 90 °C.

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