Electroplating Process Learning Materials (2)

(3) Acid Degreasing
① Purpose and Function: Remove the oxides on the copper surface of the circuit, the residual glue of the ink residue film, and ensure the bonding force between the primary copper and the patterned copper or nickel electroplating.
② Remember to use an acid degreaser here, why not use an alkaline degreaser and the alkaline degreaser has better degreasing effect than an acid degreaser? There are two main reasons. Because the graphic ink is not resistant to alkali, it will damage the graphic circuit, so only acid degreaser can be used before graphic plating.
③ Only need to control the concentration and time of the degreaser during production. The degreaser concentration is about 10%, and the time is guaranteed to be 6 minutes. A little longer time will not have adverse effects. The supplementary addition is 0.5-0.8L per 100 square meters liquid.

(4) Micro-Etching:
① Purpose and Function: Clean and roughen the copper surface of the circuit to ensure the bonding force between the patterned copper electroplating and the primary copper.
② Sodium persulfate is mostly used for micro-etching agents. The roughening rate is stable and uniform, and the washing property is good. The concentration of sodium persulfate is generally controlled at about 60 g/L, and the time is controlled at about 20 seconds. Copper content is controlled below 20 g/L. Other maintenance and replacement of cylinders are micro-etched with copper sinking.

(5) Pickling
①Function and Purpose:
Remove the oxide 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 water from being brought into the tank and causing the sulfuric acid content to be unstable.
② The acid leaching time should not be too long to prevent oxidation of the board surface. After a period of use, the acid solution should be replaced in time when the acid is turbid or the copper content is too high to prevent contamination of the electroplating copper cylinder and the surface of the board.
③ C.P grade sulfuric acid should be used here.

6) Graphic copper plating: also known as secondary copper, copper plating on the circuit
① Purpose and Function: In order to meet the rated current load of each line, each line and hole copper need to reach a certain thickness, and the purpose of copper plating the line is to thicken the hole copper and line copper to a certain thickness in time.
② Other items are the same as the whole plating.

7) Electroplating Tin
① Purpose and Function: The purpose of pure tin electroplating in graphics is mainly to use pure tin as a metal anti-corrosion layer to protect circuit etching.
② The bath is mainly composed of stannous sulfate, sulfuric acid and additives. The content of stannous sulfate is controlled at about 35 g/L, and the sulfuric acid is controlled at about 10%. The addition of tin plating additives is generally supplemented by the method of thousand ampere hours or according to the actual situation The effect of the production board. The current calculation of electroplating tin is generally calculated by 1.5A/square decimeter multiplied by the electroplatable area on the PCB board. The temperature of the tin cylinder is maintained at room temperature, the general temperature does not exceed 30 degrees, and it is mostly controlled at 22 degrees. Because the temperature is too high in summer, it is recommended to install a cooling temperature control system for the tin cylinder.

③Process maintenance: Supplement the tin-plating additives in time according to the thousand ampere hours every day. Check whether the filter pump is working normally and whether there is air leakage. Wipe the cathode conductive rod with a clean wet rag every 2-3 hours. Analyze it regularly every week. The tin cylinder is stannous sulfate (1 time/week), sulfuric acid (1 time/week), and the content of tin plating additives is adjusted through the Hall cell test, and the relevant raw materials are replenished in time. Terminal electrical connector; electrolyze with low current 0.2-0.5ASD for 6-8 hours every week. Check whether the anode bag is damaged every month, and replace the damaged one in time. And check whether there is anode sludge accumulated at the bottom of the anode bag, such as it should be cleaned up in time. Continuous filtration with carbon core for 6-8 hours every month, and low-current electrolysis to remove impurities. Every six months or so, it is determined whether large-scale treatment (activated carbon powder) is required according to the pollution of the tank liquid; the filter should be replaced every two weeks.

Large processing procedure:
A. Take out the anode, remove the anode bag, clean the surface of the anode with a copper brush, rinse it with water, put it into the anode bag, and put it in the acid tank for standby.
B. Put the anode bag into 10% lye solution Soak for 6-8 hours, rinse with water and dry, then soak with 5% dilute sulfuric acid, rinse with water and dry for later use.
C. Transfer the tank liquid to the standby tank, and slowly dissolve the activated carbon powder into the tank at a rate of 3-5 g/L.
After the solution is completely dissolved, adsorb for 4-6 hours, filter the tank liquid with a 10um PP filter element and filter aid powder to the cleaned working tank, put it in the anode, hang it on the electrolytic plate, and press 0.2-0. 5ASD current density and low current electrolysis for 6-8 hours.
D. After laboratory analysis, adjust the sulfuric acid and stannous sulfate content in the tank to within the normal operating range. Supplement tin plating additives according to the Hall cell test results.
E. Plates to be electrolyzed After the color of the surface is uniform, stop electrolysis.
F. Trial plating.
④When supplementing drugs, such as stannous sulfate and sulfuric acid in a large amount. After adding, electrolyze with low current. Pay attention to safety when supplementing sulfuric acid, and when adding a large amount (above 10 liters), it should be slowly divided into several times. Supplement; otherwise, the temperature of the bath will be too high, the stannous will be oxidized, and the aging of the bath will be accelerated.
⑤Calculation formula for drug addition:
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