Chemical copper is widely used in a through-hole printed circuit board production and processing, its main purpose is to through a series of chemical processing in the non-conductive layer of copper deposited on the substrate, and then through follow-up so thick the plating method to design a specific thickness, under normal circumstances is 1mil (25.4um) or thicker, and sometimes even directly deposited by chemical methods to the entire line of copper thickness.

No electrochemical copper process
The main purpose of pre-treatment steps:
1. To ensure that the electroless copper layer and the non-conductive substrate binding force between the
2. Electroless copper deposition layer to ensure the continuous integrity;
3. Copper foil substrate to ensure chemical bonding between;
4. Inner layer copper foil to ensure chemical bonding between
These are the chemical copper / electroless copper brief description of the role of pre-treatment.

Sulfuric acid method:
Bath have a very good after washing, preferably hot water, try to avoid strong alkaline solution when washed. Sulfonate may form some of the sodium salt of epoxy residues generated, this compound is difficult to removed from the hole clean. It will form the existence of hole pollution, can cause a lot of plating problems.

Chromic acid method:
The presence of holes causing hexavalent chromium chemical copper coverage hole many of the problems. It will damage through the oxidation mechanism of palladium tin colloid and hinder the chemical reduction of copper. Holes break this is the result of obstruction caused by the common. This kinds of situations can be resolved by the second activation, but the high cost of rework or secondary activation, especially in the auto line, the secondary activation process is not very mature.
Chromate treatment often have in the tank and steps to address the general use of sodium bisulfite to hexavalent chromium reduced to 3. Neutralizer sodium bisulfite solution temperature is generally about 100F, the temperature during and after the washing usually in the 120-150F, sulfite can be cleaned to avoid additional bath into the process, interfere with activation.