PCB News - Why should PCB be browned

We all know that there are many procedures for making PCB from planning and feeding to the last step, one of which is called browning. Some people may ask what is the role of browning? What's the difference between it and blackening? Today Xiaobian will take you to seek this answer.

Browning and blackening in the PCB manufacturing process are to increase the adhesion between the original board and pp. if browning is not good, it will lead to problems such as delamination of PCB oxidation surface, unclean etching of inner layer, infiltration plating and so on.

Browning has the following three functions

1. Remove grease and sundries on the surface to ensure the cleanliness of the board surface.

2. After browning, there is a layer of uniform fluff on the copper surface of the substrate, so as to increase the binding force between the substrate and PP and avoid layered plate explosion.

3. After browning, it must be pressed within a certain time to avoid water absorption of browning layer, so as to cause plate explosion.

There are two major differences between browning and blackening:

Similarities between browning and blackening

A. Increase the contact area between copper foil and resin and increase the bonding force between them.

B. Increase the wettability between copper and flowing resin, so that the resin can flow into each dead corner and have stronger adhesion after hardening;

C. A fine passivation layer is formed on the surface of copper to prevent the reaction between hardener and copper under high temperature and high pressure to generate water and produce plate explosion.

Differences between browning and blackening

1. The thickness of blackened villi is different from that of browning villi;

2. The micro erosion rate of blackening solution is higher than that of browning solution;

3. Blackening potion is more expensive than browning potion in price;

4. Blackened potions are more difficult to control than browning potions;

5. Quality: the surface roughness of the blackened PCB is large. If the inner line is slightly scratched or patched, the blackening can cover up well, but not browning.