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PCB process electroplating process learning data
2021-10-07
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Author:Aure

PCB process electroplating process learning data



one. Classification of electroplating process:

Acid bright copper electroplating Nickel/gold electroplating tin electroplating

 

two. PCB process flow:
Acid pickling→full board copper electroplating→graphic transfer→acid degreasing→secondary countercurrent rinsing→micro-etching→secondary→acid pickling→tin plating→secondary countercurrent rinsing →Nickel plating→Secondary washing→Citric acid immersion→Gold plating→Recycling→2-3 pure water washing→drying

 

three. Flow Description:

(1) Pickling

① Function and purpose: to remove oxides on the surface of the board and activate the surface of the board, the general concentration is 5%, and some are maintained at about 10%, mainly to prevent the instability of the sulfuric acid content of the tank liquid due to the introduction of moisture;

② The acid leaching time should not be too long to prevent oxidation of the board surface; after a period of use, when the acid solution becomes turbid or the copper content is too high, it should be replaced in time to prevent contamination of the electroplating copper cylinder and the surface of the board;

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

 


PCB process electroplating process learning data


(2) Full board copper electroplating: also called once copper, board electricity, Panel-plating

① Function and purpose: Protect the thin chemical copper that has just been deposited, prevent the chemical copper from being etched away by acid after oxidation, and add it to a certain extent by electroplating

② All-board copper electroplating related process parameters: the main components of the bath are copper sulfate and sulfuric acid. The high acid and low copper formula is adopted to ensure the uniformity of the plate surface thickness distribution and the deep plating ability for deep holes and small holes during electroplating; the sulfuric acid content is high At 180 g/l, more often reach 240 g/l; copper sulfate content is generally around 75 g/l, and a trace amount of chloride ions are added to the bath solution, which acts as an auxiliary brightener and copper brightener to jointly exert the gloss effect; copper The amount of brightening agent added or the amount of open cylinder is generally 3-5ml/L, the addition of copper brightening agent is generally supplemented by the method of thousand ampere hours or according to the actual production board effect; the current calculation of the full-plate electroplating is generally 2A/square Decimeter multiplied by the electroplatable area of the board, for the whole board, it is the board length dm×the board width dm×2×2A/DM2; the temperature of the copper cylinder is maintained at room temperature, generally the temperature does not exceed 32 degrees, more control At 22 degrees, because the temperature is too high in summer, it is recommended to install a cooling temperature control system for the copper cylinder;

③ Process maintenance: replenish the copper polish in time according to the thousand-ampere hours every day, and add 100-150ml/KAH; check whether the filter pump is working properly and there is no air leakage; apply a clean wet cloth every 2-3 hours Clean the cathode conductive rod; analyze the copper sulphate (1 time/week), sulfuric acid (1 time/week), and chloride ion (2 times/week) content in the copper cylinder every week, and adjust the light through the Hall cell test. The anode conductive rod and the electrical joints at both ends of the tank should be cleaned every week, and the anode copper balls in the titanium basket should be refilled in time, with a low current of 0. 2-0. 5ASD electrolysis 6-8 hours; every month should check whether the anode titanium basket bag is damaged, and the damaged one should be replaced in time; and check whether there is anode mud accumulated at the bottom of the anode titanium basket, if any, it should be cleaned up in time; and continuously filtered with a carbon core 6-8 hours, at the same time, low current electricity to remove impurities; every six months or so according to the tank liquid pollution status to determine whether a major treatment (active carbon powder) is needed; the filter element of the filter pump should be replaced every two weeks;]

④ Major processing procedure: A. Take out the anode, pour out the anode, clean the anode film on the anode surface, and then put it in the barrel of the copper anode. Use a microetching agent to roughen the surface of the copper corner to a uniform pink color, and then rinse and dry. Then, put it into the titanium basket, and then put it into the acid tank for use. B. Put the anode titanium basket and anode bag into 10% lye for 6-8 hours, wash and dry, then soak with 5% dilute sulfuric acid, wash and rinse dry After standby; C. Transfer the tank liquid to the standby tank, add 1-3ml/L of 30% hydrogen peroxide, start heating, wait until the temperature is about 65 degrees, turn on air stirring, and keep warm air for 2-4 hours; D .Turn off the air stirring, slowly dissolve the activated carbon powder into the tank liquid at a pressure of 3-5 g/L, and when the dissolution is complete, turn on the air to stir and keep it warm for 2-4 hours; E. Turn off the air stirring and heat up. Let the activated carbon powder slowly settle to the bottom of the tank; F. When the temperature drops to about 40 degrees, use a 10um PP filter element to add filter powder filter tank liquid to the clean working tank, turn on the air and stir, put in the anode, and hang Enter the electrolytic board and press 0. 2-0. 5ASD current density and low current electrolysis for 6-8 hours, G. After laboratory analysis, adjust the sulfuric acid, copper sulfate, and chloride ion content in the tank to the normal operating range; supplement the light agent according to the test results of the Hall cell; H. wait for the electrolysis plate After the color of the board is uniform, you can stop the electrolysis, and then press 1-1. The current density of 5ASD is electrolytically grown for 1-2 hours, and a layer of black phosphorous film with good adhesion and uniformity is formed on the anode; I. Trial plating is OK.

⑤ The anode copper ball contains 0. 3-0. The main purpose of 6% phosphorus is to reduce the anode dissolution efficiency and reduce the production of copper powder;

⑥ When replenishing drugs, if the amount of addition is large, such as copper sulfate or sulfuric acid; after adding, electrolysis should be performed at a low current; when adding sulfuric acid, pay attention to safety, and when adding large amounts (above 10 liters), add several times slowly. Add; otherwise it will cause the bath temperature to be too high, the decomposition of the light agent will accelerate, and the bath will be contaminated;

⑦ Special attention should be paid to the addition of chloride ions, because the content of chloride ions is particularly low (30-90ppm). When adding, it must be accurately weighed with a graduated cylinder or measuring cup before adding; 1ml of hydrochloric acid contains about 385ppm of chloride ions.

⑧ Formula for adding medicine: 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

 

(3) Acid degreasing

① Purpose and function: to remove the oxide on the copper surface of the circuit, the remaining glue of the ink residual film, and to ensure the bonding force between the primary copper and the pattern electroplating copper or nickel

② Remember that acidic degreaser is used here, why not use alkaline degreaser and alkaline degreaser has better degreasing effect than acid degreaser? The main reason is that the graphic ink is not resistant to alkali and will damage the graphic circuit. Therefore, only acidic degreasing agent can be used before the graphic plating.

③ You only need to control the concentration and time of the degreaser during production. The concentration of the degreaser is about 10%, and the time is guaranteed to be 6 minutes. If the time is longer, there will be no adverse effects; the replacement of the tank liquid is also based on 15 square meters per liter. Liquid, supplemented and added according to 100 square meters 0. 5-0. 8L;

 

 (4) Micro-etching:

① Purpose and function: clean the copper surface of the roughened circuit to ensure the bonding force between the patterned copper plating and the primary copper

② The micro-etching agent mostly uses sodium persulfate, the coarsening rate is stable and uniform, and the washing performance is good. The concentration of sodium persulfate is generally controlled at about 60 grams/liter, and the time is controlled at about 20 seconds. ; The copper content is controlled below 20 g/liter; other maintenance and cylinder replacement are the same as sinking copper and micro-corrosion.

 

(5) Pickling

①Function and purpose: to remove oxides on the board surface and activate the board surface. The general concentration is 5%, and some are kept at about 10%, mainly to prevent the instability of the sulfuric acid content of the tank liquid due to the introduction of moisture;

②The acid leaching time should not be too long to prevent oxidation of the board surface; after a period of use, when the acid solution becomes turbid or the copper content is too high, it should be replaced in time to prevent contamination of the electroplating copper cylinder and the surface of the board;

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

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