Abstract

This paper addresses the analysis of die attach disbonds (delaminations) of silicon die in a multichip module (MCM). A silicon die attached to a silicon substrate in an MCM requires good adhesion for thermal dissipation and reliability purposes. Traditionally, die attach is evaluated by destructively measuring adhesion or non-destructively measuring voiding through x-ray radiography. For this paper, non-destructive acoustic microscopy and destructive dye penetrant testing were used to supplement the x-ray radiography. A sample in which x-ray radiography showed little die attach voiding had significant die attach disbonds at both the die/die attach interface as well as the die attach/substrate interface. The disbonds were identified by the acoustic microscope. Interpretation of the acoustic microscopy data proved complex and required careful comparison of the C-mode images generated with the A-scans at specific locations. The nature of the disbonds at the A-scan locations was confirmed using dye penetrant testing, metallurgical cross section and optical microscopy. The disbonded areas can change the thermal dissipation characteristics and mechanical stress distribution of the sample and indicate processing problems. X-ray radiography is effective for determining density variations or voiding in the die attach and acoustic microscopy is effective for determining interface characteristics and the combination of the two techniques provides an excellent approach for evaluating die attach in MCM’s. These techniques can be applied to interfacial analysis of other structures and can be used to characterize interfaces for modeling and establish evaluation criteria for non-destructive process monitoring.

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