Setout ellipse curve with the traditional method of four-center will bring up offset of point and deformation of chart .

四心圆法测设椭圆曲线会造成点位偏移,图形变形。

In the production process of PCB, there are many defects such as surface smudginess, solder mask unevenness, text excursion, pad damage, track damage etc.

在印刷电路板的生产过程中,会产生外观不整洁、阻不均匀、文字偏移、线路及盘破损等缺陷。