Intermetallic Growth And ,Wire Bonding Characterization On Aluminium Bond Pad
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Date
2003-04
Authors
Chan, Weng Heng
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Abstract
The objective of this project is to characterise the semiconductor technology of \vire
bonding devices which base material study is on Aluminium bond pad. The research and
development on wire bonding process is carried out to improve the capability of gold
wire bonding process. This thesis studies intermetallic phase formation and intermetallic
growth during thermal aging as a function of bonding parameters for fine pitch ball
bonding. The analyses include wire bonding parameter characterisation on first ball
bond and free air ball formation. The major bonding process parameters are power;
. force and free ai,r ball size were adjusted to achieve l)ptimum shear strength. The.
responses of this characterisation by using Design of Experiment methodology to
evaluate the performance of bonding process are shear strength and pull strength results.
In addition, an evaluation is analysed with applying different thermal storage conditions
with response of intermetallic growth thickness as a correlation of shear strength and
pull strength performance. The relationships between initial intermetallic phase
coverage, shear strength, pull strength and intermetallic growth were also investigated.
A simple image analysis method was used to accurately calculate the initial coverage
and intermetallic phase growth was studied by metallographic cross-section techniques.
From this experimental data. intermetallic coverage patterns were related to the
intermetallic phase thickness growth and the degradation of the IP joints was
investigated. The results of analysis shown that different diffusion mechanisms at higher
teTiij5eratures, making doubtful a simple scaling of growth rates and bond degradation
obtained at higher temperatures to realistic levels. Hence, these studies indicated that the
magnitude of grOWth in intermetallic AI-Au is proportional to the amount duration of
curing time at 175°C aging temperature.
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Keywords
Wire bonding devices , on Aluminium bond pad