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PCB electrogold plating nickel plating
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PCB electrogold plating nickel plating

① Purpose and function: the nickel plating layer is mainly used as a barrier layer between the copper layer and the gold layer to prevent the gold and copper from diffusing each other, affecting the weldability and service life of the board; At the same time, the nickel substrate also greatly increases the mechanical strength of the gold layer;

② Full-board PCB electroplating copper related process parameters: the addition of nickel plating additives is generally supplemented by the method of thousand ampere-hours or according to the actual production board effect, the addition amount is about 200ml/KAH; The current calculation of graphic PCB electroplating nickel is generally calculated by 2 amp/square decimeter multiplied by the PCB plating area on the board; The temperature of the nickel cylinder is maintained at 40-55 degrees, and the general temperature is about 50 degrees, so the nickel cylinder should be equipped with heating and temperature control system;

③ Process maintenance: timely addition of nickel plating additives according to kiloampere hours per day; Check whether the filter pump works properly and there is no air leakage; Use a clean wet rag to scrub the cathode conductive rod every 2-3 hours; The content of nickel sulfate (nickel sulfamate), nickel chloride (once/week) and boric acid (once/week) in copper cylinder should be analyzed regularly every week, and the content of nickel plating additives should be adjusted through Hall tank test, and relevant raw materials should be supplemented in time. Every week to clean the anode conductive rod, the groove both ends of the electrical joint, timely supplement the anode nickel Angle in the titanium basket, with low current 0. 2-0. 5ASD electrolysis 6-8 hours; The titanium basket bag of the anode should be checked every month for damage, and the damaged should be replaced in time; And check whether there is anode mud accumulated at the bottom of the anode titanium basket, if there should be cleaned up in time; Continuous filtration with carbon core for 6-8 hours, while low current electricity to remove impurities; Every six months or so, according to the specific pollution status of the tank liquid, it is necessary to determine whether large-scale treatment (activated carbon powder); Replace the filter element of the filter pump every two weeks;


④ Large treatment procedures: 

A. remove the anode, pour the anode out, 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 until it is uniform pink, wash it dry, put it in the titanium basket, and put it into the acid tank for use. 

B. The anode titanium basket and anode bag are soaked in 10% lye for 6-8 hours, washed dry, then soaked in 5% dilute sulfuric acid, washed dry for later use.

C. Transfer the tank liquid to the spare tank, add 1-3ml/L of 30% hydrogen peroxide, start heating, when the temperature increases to about 65 degrees, turn on the air and stir, hold the air and stir for 2-4 hours.

D. Turn off the air mixing, slowly dissolve the activated carbon powder into the tank by 3-5 g/l, and open the air mixing after the solution is completely dissolved, so that the heat preservation 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, filter the tank liquid with 10um PP filter element and filter powder to clean the working tank, turn on the air to stir, put the anode, hang the electrolytic plate, and press 0. It's 2-0. 5ASD current density low current electrolysis 6-8 hours. 

G. After laboratory 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 cell test. 

H. After the color of the electrolytic plate surface is uniform, the electrolysis can be stopped, and then press 1-1. The current density of 5ASD is electrolyzed for 10-20 minutes to activate the anode; I. Test plating OK.

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

⑥ After nickel plating, it is recommended to add a recovery 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, recover and wash after two countercurrent rinsing;

⑦ Drug addition calculation formula:

Nickel sulfate (unit: 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

It is divided into PCB electroplating hard gold (gold alloy) and water gold (pure gold) process, hard gold plating and soft gold bath liquid composition is basically the same, but there are more trace metals nickel or cobalt or iron and other elements in the hard gold bath;

① Objective and function: 

As a precious metal, gold has good weldability, oxidation resistance, corrosion resistance, small contact resistance, good wear resistance and so on.

② At present, PCB electroplating is mainly citric acid gold bath, which is widely used for its simple maintenance and easy operation;

③ The water gold content is controlled at about 1 g/l, and the PH value is about 4.5, the temperature is 35 degrees, the specific gravity is about 14 baumes, 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 maintain the stability of the gold cylinder;

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

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

The organic pollution of the gold cylinder should be continuously filtered with carbon core, and an appropriate amount of gold-plating additives should be added.

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