A micromechanism study of thermosonic gold wire bonding on aluminium pad
A micromechanism of thermosonic gold wire bonding was elaborated by examining its interfacial characteristics as a result of the bonding process, including the fragmentation of the native aluminum oxide layer on Al pads, and formation of initial intermetallic compounds...
| Main Authors: | , , , , , , , |
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| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
| Published: |
2012
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/94156 http://hdl.handle.net/10220/7694 |
| Summary: | A micromechanism of thermosonic gold wire bonding was elaborated by examining its interfacial
characteristics as a result of the bonding process, including the fragmentation of the native
aluminum oxide layer on Al pads, and formation of initial intermetallic compounds (IMCs). It is
found that the existence of an approximately 5 nm thick native oxide layer on original Al pads has
a significant effect on the bonding, and the nucleation of IMCs during the bonding process must
overcome this relatively inert thin film. Bonding strength was fundamentally determined by the
degree of fragmentation of the oxide films, through which the formation of IMCs can be initiated
due to the direct contact of the metal surfaces to be bonded. The extent of fracture the oxide layer
was strongly influenced by the level of ultrasonic power, as at its high level alumina fragmentation
becomes pervasive resulting in contiguous alloy interfaces and robust bonds. The IMCs formed at
the interfaces were identified as Al4Al and AuAl2 with a thickness of 150–300 nm. The formation
mechanism of such IMCs was explained by the effective heat of formation theory. |
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