Abstract

Current methods used for package level destructive physical analysis (DPA) such as chemical and mechanical decapsulation methods, reactive ion etching (RIE) and diamond saw x-section methods could potentially result in artifacts such as die cracking, delamination or corrosion when used on complex packaging technologies such as multiple thin die stacked packages with combination of flip chip and wire bond interconnections. Many of the shortcoming of these ubiquitous DPA tools are being addressed by a laser milling approach to DPA. The system described in this paper consists of a ultraviolet (UV) laser used for local micromachining or milling to access package internal features and a near infrared(IR) laser used for precise soldering of fine wires to enable testing and fault isolation. Applications of the laser milling tool described in the paper are 1) Delayering of multilayer printed circuit board (PCB) substrates to expose internal metal traces so that they can be tested to fault isolate the failure without loosing electrical functionality of the product. 2) Silicon milling to expose flip chip interconnections. 3) Package cross sectioning and 4) Plastic package decapsulation.

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