by Florian Eacock, Andreas Unger, Paul Eichwald, Olexandr Grydin, Florian Hengsbach, Simon Althoff, Mirko Schaper, Karsten Guth
Abstract:
Ultrasonic heavy wire bonding is a commonly used technology to conduct electrical devices in power electronics. In order to facilitate powerful solutions combined with an increased efficiency, involving a material change from aluminum to copper wire as conductor material takes place in recent years. Due to the material related properties, copper wire bonding requires significant higher bond processing parameters such as bond force and ultrasonic power compared to aluminum which can lead to damages or a failure of the bonded component. Therefore, a profound knowledge of the processes prevailing during wire bonding is essential to optimize the application of the copper wires and consequently to achieve the demands on quality and reliability. The behavior of different natural surface oxides of aluminum and copper are assumed to be one reason for the deviation in the required bond parameters. Accordingly, the impact of differently pre-treated substrates surfaces on which the bonding is applied were investigated in this study. First, all conditions investigated (as-received, oxidefree, AlOx and the CuOx) were characterized by utilizing scanning electron microscopy, energy dispersive X-ray spectroscopy, focused ion beam microscopy and atomic force microscopy. In addition, hardness tests were performed as well as perthometer measurements. Afterwards, a 500 $\mu$ m copper wire was bonded on the generated surfaces investigated. In consideration of the roughness, shear test of various bond times and microscopic images were evaluated. Finally, the results were compared and discussed. Overall, the current study indicates that an Al-oxide layer is beneficial for welding process in Cu wire bonding. On the contrary, the Cu-oxide is detrimental and leads to a delayed welding of the joining parts. Based on the obtained results, it can be expected that due to an ideal set of Al-oxide layers, lower optimal bond parameters can used to reach high bond strength with good reliability properties.
Reference:
Eacock, F.; Unger, A.; Eichwald, P.; Grydin, O.; Hengsbach, F.; Althoff, S.; Schaper, M.; Guth, K.: Effect of different oxide layers on the ultrasonic copper wire bond process. IEEE 66th Electronic Components and Technology Conference, 2016. (Preprint: https://groups.uni-paderborn.de/ldm/publications/download/Eacock2016preprint.pdf)
Bibtex Entry:
@INPROCEEDINGS{Eacock2016,
author = {Florian Eacock AND Andreas Unger AND Paul Eichwald AND Olexandr Grydin
AND Florian Hengsbach AND Simon Althoff AND Mirko Schaper AND Karsten
Guth},
title = {Effect of different oxide layers on the ultrasonic copper wire bond
process},
booktitle = {IEEE 66th Electronic Components and Technology Conference},
year = {2016},
pages = {2111-2118},
abstract = {Ultrasonic heavy wire bonding is a commonly used technology to conduct
electrical devices in power electronics. In order to facilitate powerful
solutions combined with an increased efficiency, involving a material
change from aluminum to copper wire as conductor material takes place
in recent years. Due to the material related properties, copper wire
bonding requires significant higher bond processing parameters such
as bond force and ultrasonic power compared to aluminum which can
lead to damages or a failure of the bonded component. Therefore,
a profound knowledge of the processes prevailing during wire bonding
is essential to optimize the application of the copper wires and
consequently to achieve the demands on quality and reliability. The
behavior of different natural surface oxides of aluminum and copper
are assumed to be one reason for the deviation in the required bond
parameters. Accordingly, the impact of differently pre-treated substrates
surfaces on which the bonding is applied were investigated in this
study. First, all conditions investigated (as-received, oxidefree,
AlOx and the CuOx) were characterized by utilizing scanning electron
microscopy, energy dispersive X-ray spectroscopy, focused ion beam
microscopy and atomic force microscopy. In addition, hardness tests
were performed as well as perthometer measurements. Afterwards, a
500 $\mu$ m copper wire was bonded on the generated surfaces investigated.
In consideration of the roughness, shear test of various bond times
and microscopic images were evaluated. Finally, the results were
compared and discussed. Overall, the current study indicates that
an Al-oxide layer is beneficial for welding process in Cu wire bonding.
On the contrary, the Cu-oxide is detrimental and leads to a delayed
welding of the joining parts. Based on the obtained results, it can
be expected that due to an ideal set of Al-oxide layers, lower optimal
bond parameters can used to reach high bond strength with good reliability
properties.},
comment = {Preprint: \url{https://groups.uni-paderborn.de/ldm/publications/download/Eacock2016preprint.pdf}},
doi = {10.1109/ECTC.2016.91},
file = {Eacock2016preprint.pdf:Eacock2016preprint.pdf:PDF},
keywords = {Ultrasonic copper wire bonding, Al-oxide, Cuoxide, oxide-free, roughness,
morphology},
owner = {tobiasm},
timestamp = {2016.06.13},
url = {http://ieeexplore.ieee.org/document/7545715/}
}