Improvement of the near short failure through foreign particle reduction in package

Abstract

The presence of foreign metal particle inside the encapsulation of IC package can seriously cause a near short failure mechanism. The near short typically formed with two neighbour wires or bond pad with a small spacing. The near short will be degraded to an intermittent contact and finally a short at the early life. Especially with the high pin counts and finer bond pad pitch package, a 8um metal particle can cause the near short phenomena. In this paper, the source of foreign metal particle had been identified using EDX technique. Initial finding show the foreign metal particle consists of Cu, Ag, Fe, Cr, Al elements. It is believe that the source of foreign particles is coming from the raw material and assembly process parts. In order to further understand the presence of the particles from each assembly process steps, a detailed process mapping (mouse trap monitoring) had been carried out to further identified the potential risk area. A total of 3 concepts had been applied to reduce the particles in the package which are prevention of metal particle drop into the package, reduction of the friction between two metals and the 5S control. It was found that by installing the roller bearing at indexer track to minimize the friction between two metals is successfully reduce 93% of the particle burr that will drop off and mold in the package. Avoid metals friction will helps to reduce foreign metal particle to eliminate near short failure.