Wire bond short reduction by encapsulation

It is common place in the semiconductor packaging industry to inspect wires and remove shorts by rework prior to molding, in order to maximize yield. This process creates technical and commercial challenges for ultra fine pitch devices, multiple layers of wires, and stacked die applications. An alternative, automated method of removing wire shorts is presented in this paper. Experimental results demonstrate that the controlled application of a filled polymer with tailored rheology and surface tension can separate electrically shorted wires. This paper shows the separation of wires in cross sections of encapsulated devices, electrical test results of 35 μm bond pitch devices pre and post-encapsulation, and discusses the physics that make this process possible. The packaging process and the process impact on device yield are also described.