Electrochemical Copper-Free Process (2)

B. Charge Adjustment or Whole Hole

A typical charge adjustment process is used after degreasing. Generally, in the production of some special boards and multi-layer PCB boards, due to the charge factor of the resin, after the process of removing the slag and etch, it is necessary to adjust the charge. The important role is to “super wet” the non-conductive substrate, in other words, to denature the originally weakly negatively charged resin surface into a weakly positively charged active surface after being treated with the conditioning solution. In some cases, a uniform continuous positive charge polar surface is provided, which can ensure that the subsequent activator can be effectively and fully adsorbed on the pore walls. Sometimes the adjusted drug is added to the degreaser, so it is also called a degreaser adjustment fluid, although separate degreaser and adjustment fluid will work better than a combined degreaser adjustment fluid, but the industry trend has combined the two into one, and the modifier is actually just some surfactants. The adjusted water washing is extremely important. Insufficient water washing will cause the surfactant to remain on the copper surface, contaminate the subsequent micro-etching, and the activation solution, which may affect the final binding force between copper and copper, resulting in reduced chemical copper and substrate bond between copper. Here, attention should be paid to the temperature of the cleaning water and the flow of water for effective cleaning. Special attention should be paid to the concentration of the adjuster, and the use of too high concentration of the adjuster should be avoided, and an appropriate amount of the adjuster will have a more obvious effect.

C. Micro-Etching
The next step in the pretreatment of micro-etching electroless copper deposition is micro-etching or micro-roughening or roughening step. The purpose of this step is to provide a micro-rough active copper surface structure for subsequent electroless copper deposition. If there is no micro-etching step, the bonding force between the chemical copper and the substrate copper will be greatly reduced. The roughened surface can play the following functions:

1. The surface area of ​​the copper foil is greatly increased, and the surface energy is also greatly increased, providing a large contact area between the chemical copper and the base copper.

2. If some surfactants are not removed during washing, the microetching agent can remove the surface active agent on the surface of the substrate by etching away the copper base on the copper surface of the bottom substrate, but it is completely dependent on the microetching agent to remove the surface active agent. It is unrealistic and effective, because when the surface area of ​​the copper surface left by the surfactant is large, the chance of allowing the effect of the microetching agent is very small, and the copper surface at the large surface active agent residue is often not microetched.