PCB nickel plating

① Purpose and function: Nickel plating layer is mainly used as a barrier layer between copper layer and gold layer to prevent gold and copper mutual diffusion, affecting the weldability and service life of the plate; At the same time, the nickel layer has greatly increased the mechanical strength of the gold layer;

② Process parameters related to full-plate copper plating: the addition of nickel plating additive is generally supplemented by the method of kiloampere hour or according to the actual production effect of the plate, the addition amount is about 200ml/KAH; The current of graphic nickel plating is generally calculated as 2 ampere/square decimeter times the plating area on the plate; Nickel cylinder temperature is maintained at 40-55 degrees, the general temperature is about 50 degrees, so the nickel cylinder should be installed with heating, temperature control system;

③ Process maintenance:

Daily according to thousands of hours to timely supplement nickel plating additives; Check whether the filter pump works normally and there is no leakage; Scrub the cathode conductive rod with a clean wet rag every 2-3 hours; The content of nickel sulfate (nickel sulfamesulfonic acid) (once a week), nickel chloride (once a week) and boric acid (once a week) in copper cylinder should be analyzed regularly every week, and the content of nickel plating additives should be adjusted by Hall chamber test, and relevant raw materials should be supplemented in time; Every week to clean the anode conductor rod, the tank body at both ends of the electrical joint, timely supplement the anode nickel Angle in the titanium basket, with low current 0.2-0.5asD electrolysis for 6-8 hours; Monthly check whether the anode titanium basket bag is damaged, damaged should be replaced in time; And check whether there is anode mud at the bottom of the anode titanium basket, if there is, it should be cleaned up in time; With carbon core continuous filtration for 6-8 hours, at the same time low current to remove impurities; Every half a year or so according to the specific tank pollution situation to decide whether to need large treatment (activated carbon powder); Replace the filter element of the filter pump every two weeks;

(4) Large processing procedures: A. Take out the anode, pour out the anode, clean the anode, and then put it in the bucket of packaging nickel Angle, coarsing the surface of the nickel Angle with micro-etching agent to uniform pink, wash and dry, put it into the titanium basket, square into the acid tank reserve B. The anode titanium basket and anode bag were soaked in 10% lye for 6-8 hours, washed and dried, then soaked in 5% dilute sulfuric acid, washed and dried for later use; C. Transfer the tank to the spare tank, add 1-3ml/L 30% hydrogen peroxide, start heating, when the temperature increases to about 65 degrees, turn on the air stirring, keep the air stirring for 2-4 hours; D. Turn off the air stirring, and slowly dissolve the activated carbon powder into the tank at the rate of 3-5 g/l. After the solution is completely dissolved, open the air stirring, so as to hold the heat for 2-4 hours; E. Turn off the air, stir, heat, let the activated carbon powder slowly precipitate to the bottom of the tank; F. When the temperature drops to about 40 degrees, use 10um PP filter element and filter powder to filter the tank into the clean working tank, turn on the air and stir, put in the anode, hang the electrolytic plate, press 0. It's 2-0. 5ASD current density low current electrolysis 6-8 hours, G. After analysis, adjust the content of nickel sulfate or nickel sulfonic acid, nickel chloride, boric acid in the tank to the normal operating range; Nickel plating additives were added according to the results of Hall groove test. H. When the color of the electrolytic plate surface is uniform, the electrolysis can be stopped, and then the electrolytic treatment is carried out at the current density of 1-1.5ASD for 10-20 minutes to activate the anode; I. Test plating OK.

⑤ Supplement drugs, such as the addition of large amount such as nickel sulfate or nickel sulfonic acid, nickel chloride, after adding low current electrolysis; When adding boric acid, the supplementary amount of boric acid should be loaded into a clean anode bag hanging into the nickel cylinder, can not be directly added to the tank;

After nickel plating, it is recommended to add a recovery of water washing, open the cylinder with pure water, which can be used to supplement the liquid level of the nickel cylinder due to heating and volatilization, recovery of water after two countercurrent rinsing;

⑦ Calculation formula of drug addition:

Nickel sulfate (kg) = (280-X) x tank volume (L) /1000

Nickel chloride (unit: kg) = (45-X) x tank volume (L) /1000

Boric acid (kg) = (45-X) x tank volume (L) /1000

Electroplating: divided into electroplating hard gold (gold alloy) and water gold (pure gold) process, hard gold plating and soft gold liquid composition is basically the same, but the hard gold groove more than some trace metal nickel or cobalt or iron and other elements;

Objective and effect: As a kind of precious metal, gold has good weldability, oxidation resistance, corrosion resistance, small contact resistance, good wear resistance and so on.

At present, the main gold-plated circuit board is citrate gold bath, which is widely used for its simple maintenance, simple and convenient operation;

(3) Water gold content is controlled at about 1g/l, PH value 4. About 5, the temperature is 35 degrees, the specific gravity is about 14 beaum, the current density is about 1ASD;

(4) The main added drugs are acid adjusting salt and basic adjusting salt to adjust PH value, conductive salt to adjust specific gravity and gold-plated supplementary additives and gold salt;

(5) In order to protect the gold cylinder, a citric acid dipping tank should be added before the gold cylinder, which can effectively reduce the pollution of the gold cylinder and keep the stability of the gold cylinder;

After electroplating, a pure water washing is used as recovery washing, which can also be used to supplement the liquid level of the evaporation change of the gold cylinder. After recovery washing, it is washed with two counter current pure water, and 10 g/l lye is put into the gold plate to prevent the oxidation of the gold plate.

 The gold cylinder should use platinum-plated titanium mesh as anode, generally 316 stainless steel is easy to dissolve, resulting in nickel iron chromium and other metal pollution of the gold cylinder, resulting in gold plating white, dew plating, black and other defects;

Organic pollution of gold cylinder using carbon core continuous filtration, and add appropriate amount of gold-plated additives.