PCB electroplating technology classification process and precautions
First, the classification of PCB plating process:
Acid bright copper PCB electroplating PCB electroplating nickel/gold PCB electroplating tin
2. Process flow:
Acid leaching → full-board PCB copper plating → Pattern transfer → acid degreasing → secondary counter-current rinsing → micro-etching → secondary → Acid leaching → tinning → secondary counter-current rinsing
Counter-current rinsing → acid leaching → Graphic PCB copper plating → secondary counter-current rinsing → nickel plating → secondary water washing → citric acid leaching → Gold plating → Recovery →2-3 pure water washing → drying
3. Process Description:
Dip in acid
① Action and purpose: remove the surface oxide, activate the surface, the general concentration is 5%, and some are kept at about 10%, mainly to prevent water from being brought into the tank resulting in unstable sulfuric acid content;
② The acid leaching time should not be too long to prevent the oxidation of the board; After a period of use, when the acid appears cloudy or the copper content is too high, it should be replaced in time to prevent pollution of the PCB electroplating copper cylinder and the surface of the plate;
③ C.P grade sulfuric acid should be used here;
Full board PCB copper plating: also called copper, plate electricity, Panel-plating
① Function and purpose: protect the thin chemical copper that has just been deposited, prevent the chemical copper from being corroded by acid after oxidation, and add it to a certain extent through PCB electroplating
② Full-board PCB electroplating copper related process parameters: the main components of the bath are copper sulfate and sulfuric acid, and the formula of high acid and low copper is used to ensure the uniformity of the thickness distribution of the board surface during PCB electroplating and the deep plating ability of deep holes; The content of sulfuric acid is mostly 180 g/l and 240 g/L; The copper sulfate content is generally about 75 grams/liter, and a trace of chloride ions are added to the other tank, which is used as an auxiliary gloss agent and copper gloss agent to exert the luster effect; The amount of copper polishing agent added or the amount of cylinder opening is generally 3-5ml/L, and the addition of copper polishing agent is generally supplemented by the method of thousand ampere-hours or according to the actual production plate effect; The current calculation of full-board PCB electroplating is generally calculated by 2 amp/square decimeter multiplied by the PCB electroplating area on the board, which is the board length dm× board width dm×2×2A/ DM2; Copper cylinder temperature is maintained at room temperature, the general temperature does not exceed 32 degrees, mostly controlled at 22 degrees, so in the summer because the temperature is too high, copper cylinder is recommended to install cooling temperature control system;
③ Process maintenance: Timely addition of copper polish according to kiloampere hours per day, according to 100-150ml/KAH supplement; 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 copper sulfate (once/week), sulfuric acid (once/week) and chloride ion (twice/week) in copper cylinder should be analyzed regularly every week, and the content of light agent 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 copper ball 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 surface anode film, and then put in the bucket of packaging copper anode, coarser the copper corner surface with micro-etching agent until it is uniform pink, wash and dry, put into the titanium basket, square 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 sulfuric acid, copper sulfate, chloride ion content in the tank to the normal operating range; The light agent was 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 treated with electrolysis film for 1-2 hours, and a layer of uniformly dense black phosphorus film with good adhesion is formed on the anode.
I. Test plating.