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Analysis of the friction processes in ultrasonic wedge/wedge-bonding

 
: Gaul, H.; Schneider-Ramelow, M.; Reichl, H.

:

Microsystem Technologies 15 (2009), No.5, pp.771-775
ISSN: 0946-7076
English
Journal Article
Fraunhofer IZM ()

Abstract
Research on wire bonding, the most common chip interconnection technology, has been done for over 40 years by now. The most common description is a model of three phases: friction, approach and interdiffusion (Lang 1988; Osterwald 1999). To quantify this model, with the main aspect at the duration of the friction phase, ultrasonic oscillation was filmed with a high speed camera. A pulsed LED light-source allowed very short exposure times of 2 mu s. For the first time it was possible to make the movement of the wire visible in a reflected light exposure. After the friction phase, the end of friction (EOF) occurs. Laser vibration measurements of the tool and the pad amplitude turned out that the EOF correlates with a second, characteristic plateau of the pad amplitude. At this time, the tool amplitude has already shown its characteristic maximum and was attenuated to approximately 80% of the maximum value. After the EOF, when the wedge is bonded to the pad, a bending of the wire towards the wedge in the heel region was observed. This is a possible reason for a weakening of the heel by the US-power. While a change of the wire texture could be proved in recent investigations (GeiAler et al. 2006), the exposure of the heel to reverse bending cycle was never verified before.

: http://publica.fraunhofer.de/documents/N-93063.html