Red pad is one of the major defects on PCB board and will result in quality issue of de-lamination. When your IQC reports a red pad issue in your PCB shipment, you need to work with your PCB supplier to identify the risk. Now PCB manufacturer china Sun&Lynn Circuits reveals the root cause and impact of PCB red pad. 

Generally speaking, the red pad is caused by the etching of chemical solvent at inner layer of PCB board. It impacts the black oxide treatment and result in the red or pink color at the copper layer. Most of the plated through holes are designed with a copper ring and when the red pad extends to outside of the ring, it will be recognized as the red pad appearance. Most of this case is classified as a quality defect since it impact the quality consistency of your PCB board and will be scrapped to prevent quality issue in your assemblies, so PCB manufacturer china Sun&Lynn Circuits suggests you to understand the importance of the red pad and work with your PCB supplier to get this under control.

The major root causes of the red pad include:
1), improper process at black oxide treatment;
2), improper lamination pressing that result in the poor combination between resin and oxide layer;
3), plated through hole drilling, the inconsistent internal stress and treat may cause the de-lamination and breaks at inner layer of your PCB board;
4), the residual acid solvent in the plated through hole at copper plating process;

The red pad is not only a cosmetic defect, but also brings potential quality issue to your assemblies. For most of the practice, the red pad is classified as the quality defact and will be scrapped at your RMA inventory. This also impact your production. What you can do with your PCB supplier to prevent this situation from happening? PCB manufacturer china Sun&Lynn Circuits tells you the corrective actions of this issue:
1), improve the thickness and fixture of the oxidation area;
2), stack-up the PCB raw material;
3), modify the parameter of lamination pressing;
4), improve the drilling process;
5), improve the plating process;

With these actions in place, the red pad issue can be improved significantly.