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PCB Plating Process Introduction

Dec 28, 2017

Circuit board plating process, can be classified about: acid bright copper plating, nickel / gold plating, electroplating tin. Plate processing is, plating technology and process, as well as specific methods of operation.


One. Process

       Pickling → full plate copper plating → graphic transfer → acid degreasing → secondary countercurrent rinsing → microetching → secondary countercurrent rinsing → pickling → tinning → secondary countercurrent → rinsing → countercurrent rinsing → pickling → graphic copper plating → Two countercurrent rinsing → nickel plating → two washing → leaching citric acid → gold plating → recycling → 2-3 → pure water washing → drying.


two. Flow Description


   (A) pickling acid

      ① role and purpose:

       Removal of surface oxides, activated surface, the general concentration of 5%, and some remained at about 10%, mainly to prevent the introduction of water caused by bath sulfuric acid content is not stable;

      ② acid leaching time should not be too long to prevent plate oxidation; use for a period of time, the acid appears cloudy or copper content is too high should be promptly replaced to prevent the pollution of copper plating and plate surface;

      ③ here should be used C.P grade sulfuric acid.


   (B) the whole board Plating copper: also known as a copper, plate, Panel-plating.

      ① role and purpose:


Protection of just deposited thin chemical copper, chemical oxidation of copper to prevent acid erosion, by adding it to a certain extent after plating;


      ② full-board copper plating process parameters: the main components of copper sulfate bath and sulfuric acid, the use of high-acid low-copper formula to ensure uniformity of plate thickness distribution and plating deep hole deep plating capacity; sulfuric acid content and more In the 180 g / L, more than 240 g / L; copper sulfate content is generally about 75 g / L, the other bath was added a trace amount of chloride ions, as an auxiliary gloss and copper agent together play a gloss effect; copper The amount of light agent or the amount of open cylinder is generally 3-5ml / L, the addition of copper agent generally in accordance with the method of thousands of hours to supplement or according to the actual production board effect; the whole board plating current calculation generally 2A / square Multiply the board can be plated area, for the whole board of electricity, that plate length dm × width dm × 2 × 2A / DM2; copper cylinder temperature maintained at room temperature, the general temperature does not exceed 32 degrees, and more control At 22 degrees, so in the summer due to the temperature is too high, the copper cylinder is recommended to install cooling temperature control system;



③ process maintenance

      Daily according to 1000 hours to replenish the copper agent, add 100-150ml / KAH added; check the filter pump is working properly, with or without leakage; every 2-3 hours with a clean wet cloth to the cathode conductive rod Scrub clean; regular weekly analysis of copper copper sulfate (1 / week), sulfuric acid (1 / week), chloride (2 times / week) content, and through the Holzer test to adjust the light content, and Timely replenishment of related raw materials; Weekly to clean the anode conductive rod, the tank at both ends of the electrical connector, and promptly replenish the anode basket copper ball, with a low current 0.2-0.5ASD electrolysis 6-8 hours; monthly inspection anode titanium Basket is damaged, damaged should be promptly replaced; and check the bottom of the anode titanium basket is deposited with anode mud, if any, should be promptly cleaned; and continuous filtration with a carbon core 6-8 hours, while low current electrolysis impurity; every six months About the specific decision according to tank status whether the need for large treatment (activated carbon powder); every two weeks to replace the filter pump filter;


      ④ large processing procedures: A. Remove the anode, the anode poured out, wash the anode surface anode film, and then placed in a barrel copper anode, with a micro-etchant roughening copper surface to a uniform pink, washed with water After loading into the titanium basket, side into the acid tank spare B. The anode titanium basket and anode bag into 10% alkali soak 6-8 hours, washed with water, then dilute with 5% sulfuric acid, washed with water C, the transfer of the bath to the spare tank, adding 1-3ml / L of 30% hydrogen peroxide, began to heat until the temperature is increased to about 65 degrees open the air stirring, holding air stirring 2-4 hours; D Turn off the air mixing, according to 3: 5 g / l slowly dissolve the activated carbon into the bath solution, to be dissolved thoroughly, open the air stirring, so heat 2-4 hours; E. Turn off the air mixing, heating, So that the active carbon slowly precipitated to the bottom of the tank; F. until the temperature dropped to about 40 degrees, with 10um PP filter plus help filter powder filter tank to clean the work tank, open the air mixing, into the anode, hanging Into the electrolysis board, according to 0.2-0.5ASD current density low current electrolysis 6-8 hours, G. By laboratory analysis, adjust the tank Sulfuric acid, copper sulfate, chloride ion content to the normal operating range; according to the Holzer test results to add light agent; H. Electrolytic plate to be uniform color, you can stop the electrolysis, and then 1-1.5ASD current density Electrolytic membrane treatment 1-2 hours until the anode to generate a layer of uniform and dense adhesion of black phosphorus can be good;


      ⑤ anode copper ball contains 0.3-0.6% of the phosphorus, the main purpose is to reduce the anode dissolution efficiency and reduce the production of copper powder;


      ⑥ supplementary drugs, such as larger amount of added, such as copper sulfate, sulfuric acid; add should be low-current electrolysis; additional sulfuric acid should pay attention to safety, additional amount larger (10 liters above) should be divided into several times slowly fill Plus; otherwise it will cause the bath temperature is too high, light decomposition speed up, pollution bath;


      ⑦ additional chloride ion should pay special attention, because the chloride ion content is particularly low (30-90ppm), additional time must be measured with a measuring cylinder or measuring cup before adding; 1ml hydrochloric acid chloride ions about 385ppm;


      ⑧ add drugs formula:

       Copper sulfate (unit: kg) = (75-X) × tank volume (liter) / 1000

       Sulfuric acid (unit: liter) = (10% -X) g / L × tank volume (liter)

       Or (unit: liter) = (180-X) g / L × tank volume (liter) / 1840

       Hydrochloric acid (unit: ml) = (60-X) ppm × tank volume (liter) / 385


   (C) Acid degreasing

      ① purpose and purpose: remove the copper lines on the line oxide, residual ink residue film to ensure that a copper and copper or nickel electroplating between the binding force;


② Remember where to use acid degreasing agent, why not alkaline degreasing agent and alkaline degreasing agent degreasing effect is better than acid degreasing agent, mainly because the graphics ink is not alkali, will damage the graphics lines, so Graphical plating can only be used before acid degreasing agent;


      ③ only need to control the degreasing agent concentration and time of production, degreasing agent concentration of about 10%, time to ensure that in 6 minutes, the longer the time will not have an adverse effect; bath replacement is also in accordance with 15 square meters / liter work Liquid, add to add 0.5-0.8L according to 100 square meters.


   (D) micro-erosion

      ① Purpose and Function: Clean roughening lines of copper surface to ensure the binding between the patterned copper plating and primary copper;


      ② micro-etchant more sodium persulfate, the roughening rate of stable, washed well, sodium persulfate concentration generally controlled at about 60 grams / liter, the time control in about 20 seconds, the drug added by 100 square meters 3-4 kg ; Copper content controlled at 20 g / L or less;


   (E) pickling

      ① role and purpose: remove the surface oxide, activated surface, the general concentration of 5%, and some remained at about 10%, mainly to prevent the introduction of water caused by bath sulfuric acid content is not stable;


      ② acid leaching time should not be too long to prevent plate oxidation; use for a period of time, the acid appears cloudy or copper content is too high should be promptly replaced to prevent the pollution of copper plating and plate surface;


      ③ here should be used C.P grade sulfuric acid.


   (F) Graphical copper plating: also known as secondary copper, copper circuit.

      ① Purpose and Function: In order to meet the rated current load of each line, each line and hole copper copper need to reach a certain thickness. The purpose of circuit copper plating is to thicken the hole copper and the line copper to a certain thickness in time;


      ② other projects are the same plate plating.


   (G) electroplating tin

      ① Purpose and Function: The purpose of electroplating pure tin is mainly to use pure tin as a metal resist to protect the circuit from etching.


      The bath is mainly composed of stannous sulfate, sulfuric acid and additives; the stannous sulfate content is controlled at about 35 g / l and the sulfuric acid is controlled at about 10%; the addition of the tinning additive is generally added according to the method of 1000 hrs or according to the actual The effect of the production plate; tin plating current calculation generally by 1: 5 A / dm multiplied by the plate can be plating area; tin cylinder temperature maintained at room temperature, the general temperature of not more than 30 degrees, and more control at 22 degrees, so in Due to the temperature is too high in summer, tin cylinder cooling system is recommended to install cooling;


      ③ process maintenance: daily according to the thousands of hours to replenish tin additives; check the filter pump is working properly, with or without leakage phenomenon; every 2-3 hours to apply a clean wet cloth to clean the cathode conductive rod; each Week to regularly analyze the tin cylinder stannous sulfate (1 / week), sulfuric acid (1 / week), and through the Hall tank test to adjust the content of tin additives, and timely replenishment of related raw materials; weekly to clean the anode conductive rod , The tank ends of the electrical connector; weekly low current 0.2-0.5ASD electrolysis 6-8 hours; monthly anode bags should be checked for damage, breakage should be promptly replaced; and check the bottom of the anode bag is stacked anode slime, If there is should be promptly cleaned up; continuous use of carbon core filter 6-8 hours a month, while low current electrolysis impurity; every six months or so depending on the tank liquid pollution status decide whether the need for large processing (activated carbon powder); every two weeks to be replaced Filter pump filter;


      ④ large handling procedures: A. Remove the anode, remove the anode bag, with a copper brush cleaning the anode surface, washed with water, into the anode bag, into the acid tank spare B. The anode bag into 10% lye Soak for 6-8 hours, washed with water, and then soaked with 5% dilute sulfuric acid, washed with water after standby ;. C will be transferred to the tank standby tank, according to 3: 5 g / L slowly dissolve activated carbon into the tank Liquid, to be completely dissolved, adsorption 4-6 hours, with 10um PP filter plus help filter powder filter tank to clean the work tank, into the anode, hanging into the electrolysis board, according to 0.2-0.5ASD current density Low current electrolysis 6-8 hours, D. by laboratory analysis, adjust the tank sulfuric acid, stannous sulfate content to the normal operating range; according to the Hall tank test results to add tin additives; E to be electrolysis board surface uniform color After that, stop electrolysis; F.


      ⑤ supplementary drugs, such as a larger amount of added, such as stannous sulfate, sulfuric acid; added should be low-current electrolysis; additional sulfuric acid should pay attention to safety, when the additional amount larger (10 liters or more) should be divided into several slow Additional; otherwise it will cause the bath temperature is too high, stannous oxide, to accelerate the tank aging;


      ⑥ drug add calculation formula:

       Stannous sulfate (unit: kg) = (40-X) × tank volume (liter) / 1000

       Sulfuric acid (unit: liter) = (10% -X) g / L × tank volume (liter)

       Or (unit: liter) = (180-X) g / L × tank volume (liter) / 1840


   (Eight) nickel plating

      ① purpose and purpose: nickel-plated layer as the main copper layer and the barrier between the gold layer to prevent mutual diffusion of gold and copper, affecting board solderability and service life; at the same time the nickel layer also greatly increased the base layer of gold Mechanical strength;


      ② full-board copper plating process parameters: Nickel additive generally added in accordance with the method of thousands of hours to supplement or according to the actual production plate effect, the amount added about 200ml / KAH; graph nickel plating current calculation generally by 2 A / square Multiplied by the board can be plating area; nickel cylinder temperature is maintained at 40-55 degrees, the general temperature of about 50 degrees, so nickel cylinder to install heating, temperature control system;


      ③ process maintenance: daily according to thousands of hours to add nickel-plated additives promptly; check the filter pump is working properly, with or without leakage phenomenon; each 2-3 hours a clean wet cloth to clean the cathode conductive rod; weekly To regularly analyze the copper cylinder nickel sulfate (nickel sulfamate) (1 / week), nickel chloride (1 / week), boric acid (1 / week) content, and through the Hall tank test to adjust the nickel plating additive Content, and timely replenishment of related raw materials; Weekly to clean the anode conductive rod, the tank ends of the electrical connector, and promptly replenish the titanium anode basket nickel angle, low current 0.2-0.5ASD electrolysis 6-8 hours; monthly should check Anode titanium basket with or without damage, damage should be promptly replaced; and check the bottom of the anode titanium basket is deposited with anode mud, if timely cleaning should be cleaned with carbon core continuous 6-8 hours, while the low current electrolysis impurity removal ; Every six months or so depending on the specific status of tank liquid pollution decision whether the need for large processing (activated carbon powder); every two weeks to replace the filter filter cartridge;


      ④ large processing procedures: A. Remove the anode, the anode poured out, wash the anode, and then placed in the barrel of nickel packing, with micro-etchant surface roughened nickel angle to uniform pink, washed with water after the installation Into the titanium basket, side into the acid tank spare B. The anode titanium basket and anode bag into 10% alkali soak 6-8 hours, washed with water, then 5% dilute sulfuric acid soaking, washed with water after standby; C. The bath was transferred to the spare tank, adding 1-3ml / L of 30% hydrogen peroxide, began to heat until the temperature was added to about 65 degrees open the air stirring, heat air stirring for 2-4 hours; D. turn off Air agitation, press 3: 5 g / l slowly dissolve the activated carbon into the bath solution, to be dissolved thoroughly, open the air stirring, so heat 2-4 hours ;. E turn off the air stirring, warming, so that activated carbon F slowly until the temperature dropped to about 40 degrees, with 10um PP filter plus help filter powder filter tank to clean the work tank, open the air mixing, into the anode, hang the electrolysis board , According to 0.2-0.5ASD current density low current electrolysis 6-8 hours, G. By laboratory analysis, adjust the tank of nickel sulfate or ammonia Nickel sulfonate, nickel chloride, boric acid content to the normal operating range; according to the Hall groove test results added nickel additive ;. H to be electrolysis board surface color uniformity, you can stop electrolysis, and then by 1-1.5ASD Current density for electrolytic treatment 10-20 minutes to activate the anode;


  ⑤ supplementary drugs, such as adding a larger amount, such as nickel sulfate or nickel sulfamate, nickel chloride, after the addition should be low-current electrolysis; additional boric acid should be added to the amount of boric acid into a clean anode bag hanging Nickel cylinder can not directly join the tank;


      ⑥ recommended after nickel plus a recycling washing, with pure water cylinder, can be used to supplement the nickel cylinder


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