A Detection Method for Effective Silver Electrode Area of High Voltage Ceramic Capacitor Using Sobel-Zernike Moment Operator

The production precision of high voltage ceramic capacitor (HVCC) is mainly affected by material and manufacturing process. The conventional quality control process is performed by human experts and sample testing, which is inefficient and error prone. In recent years, many automatic inspection equipments have been developed and many research works have been published. However, the volume manufacturing industry like capacitor still demands a faster and more reliable inspection method. In this paper, we define the silver electrode effective area of HVCC and analyze its degree of influence. The paper proposes a method which uses Sobel-Zernike moment operator to detect capacitance error caused by ineffective area of HVCC electrodes. In our experiments, the proposed method is proved to be very effective. The detecting error rate is less than 1.7%. Furthermore, the inspection method speeds up the testing process 9.9 times as well as increases the yield rate considerably.

1. Introduction

We are experiencing rapid development of semiconductor industry. In order to satisfy the requirement of electrical equipment, ceramic capacitors are developing toward smaller and more precise. Therefore, the quality control is more challenging than ever before. Traditionally, quality control process of ceramic capacitor wafer is performed by human experts and sample testing. However, humans are slower than the machines and get tired easily. Moreover, the size of components is diminishing to the scale that is hard to be inspected by human eyes. Therefore, in recent years, many automatic inspection equipments have been developed and many research works have been published [1], [2]. Almost all of them inspected the dimension and surface quality of finished product, little research has been done in middle process to control inferior products be taken into latter processes. Also in some manufactories, they introduce mechanical equipments into processes to filter unqualified semi-finished goods, but it is difficult to inspect some parameter, such as the silver electrode area of ceramic capacitor, the edge straightness, the circle concentricity and so on.