@INPROCEEDINGS{Unger2015,
  howpublished = {Conference Proceedings},
  author = {Andreas Unger AND Walter Sextro AND Tobias Meyer AND Paul Eichwald
	AND Simon Althoff AND Florian Eacock AND Michael Brökelmann AND
	Matthias Hunstig AND Karsten Guth},
  title = {Modeling of the Stick-Slip Effect in Heavy Copper Wire Bonding to
	Determine and Reduce Tool Wear},
  booktitle = {2015 17th Electronics Packaging Technology Conference},
  year = {2015},
  abstract = {To increase quality and reliability of copper wire bonds, self-optimization
	is a promising technique. For the implementation of self-optimization
	for ultrasonic heavy copper wire bonding machines, a model of stick-slip
	motion between tool and wire and between wire and substrate during
	the bonding process is essential. Investigations confirm that both
	of these contacts do indeed show stick-slip movement in each period
	oscillation. In a first step, this paper shows the importance of
	modeling the stick-slip effect by determining, monitoring and analyzing
	amplitudes and phase angles of tool tip, wire and substrate experimentally
	during bonding via laser measurements. In a second step, the paper
	presents a dynamic model which has been parameterized using an iterative
	numerical parameter identification method. This model includes Archard’s
	wear approach in order to compute the lost volume of tool tip due
	to wear over the entire process time. A validation of the model by
	comparing measured and calculated amplitudes of tool tip and wire
	reveals high model quality. Then it is then possible to calculate
	the lifetime of the tool for different process parameters, i.e. values
	of normal force and ultrasonic voltage.},
  doi = {10.1109/EPTC.2015.7412375}
}