The copper surface skived by grinding wheels becomes an accidented surface,you can see the grinding vestige by electric mirror. The surface roughness test is an intuitionistic test which can lay out the sectional roughness into a curve as the following.

In the diagram, Rz means a sum of five max contour apex heights and five max contour depths. According to our statistical data ， contrasting the best effects of preparing the surfaces of PSB's prior to photoresist,debuuring after drilling hole and solder mask,we suggest our customers to control the grinded copper surface roughness with the following standard data.

Table1. Surface Roughness Standard Data After Grinding

In every working procedure of PCB manufacturing,too small surface roughness will lead to the circs of exuviation,peeling off or throwing off oil,if too big roughness,it will make an accidented surface and other bugs, so we suggest the users to choose the brush roller providers carefully and control the pivotal parameters like brushing machine ampere.

Under the condition that grinding test and water break test are both ok,you should also control the surface roughness in the bound of Table One.