Method for electrolessly plating a PCB with copper

Abstract

The invention relates to the field of PCB manufacture and especially to a method for electrolessly plating a PCB with copper. The method comprises an activation process. The activation process comprises first-time activation and second-time activation that are executed in different activation cylinders. The activation intensity of the second-time activation is less than that of the first-time activation. The first-time activation has a main activation effect so as to basically achieve an effect of activating the wall of a hole. The second-time activation has an auxiliary or supplement activation effect. Because of the activation intensity of the second-time activation is relatively lower, activation liquid may easily enter the hole so as to effectively and fully activate the wall of the hole. Thus, a possible defect caused by the first-time activation is well compensated to a certain extent and probability is greatly reduced that thin copper or no copper is left in the hole.

Description

technical field [0001] The invention relates to the field of PCB board manufacture, in particular to a method for depositing copper on a PCB board. Background technique [0002] Electroless Plating Copper (Eletcroless Plating Copper) is also commonly known as sinking copper or porosity (PTH) is an autocatalytic redox reaction. First, it is treated with an activator, so that the surface of the insulating substrate is adsorbed with a layer of active particles, usually metal palladium particles, copper ions are first reduced on these active metal palladium particles, and these reduced metal copper crystal nuclei It becomes the catalytic layer of copper ions again, so that the reduction reaction of copper continues on the surface of these new copper crystal nuclei. [0003] Electroless copper plating has been widely used in the PCB board manufacturing industry. The typical application is the hole metallization of the PCB board. Carry out the subsequent electroplating copper pr...

AI Technical Summary

Problems solved by technology

[0004] Palladium is a very expensive metal, the price is high and has been rising. In the copper sinking process, the cost of palladium accounts for about 80% of the cost of the copper sinking process. In many factories, the main consumption of palladium is not adsorbed on the PCB board. Necessary consumption, but the consumption of the PCB board. Some manufacturers reduce the consumption of palladium by reducing the concentration of activated palladium in the activation cylinder, prolonging the time of changing the cylinder of activated palladium and prolonging the dripping time of the PCB board in the activation cylinder, but these The method poses a challenge to the quality of the PCB board to a certain extent

Reducing the concentration of activated palladium in the activation cylinder will easily lead to insufficient activation strength, which cannot guarantee the activation effect of the entire hole wall, and will easily cause poor backlight. If the cylinder is not changed for a long time, the activation solution in the cylinder will age, and there will be many suspended impurities in the solution. The surface of the hole is rough and there is even no copper in the hole. Excessively prolonging the dripping time in the activation tank may cause the activated palladium to be oxidized, which will have a negative impact on the subsequent copper deposition process, and the probability of no copper or thin copper in the hole will increase.

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