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Fluxless In&z.sbnd;Sn bonding process at 140 °C
- Source :
-
Materials Science & Engineering: A . Aug2002, Vol. 333 Issue 1/2, p45. 6p. - Publication Year :
- 2002
-
Abstract
- Device packages usually need more than one soldering operation to complete. For photonic and fiber optic device packaging, indium solder is often used due to its ductility. Since indium has a relatively low melting temperature of 156.6 °C, the subsequent bonding operation requires a process temperature that is lower than 156 °C. In this paper, we report a new bonding process at 140 °C based on an indium–tin multilayer composite. This is a fluxless bonding technique. In fabrication, a chromiurn–tin–indium–gold multilayer composite is deposited on silicon die in one high vacuum cycle to prevent oxidation. Immediately upon deposition, gold and indium react to form a stable AuIn2 protective outer layer against oxidation. Silicon substrates are deposited with thin chromium–gold layers. The silicon die and substrate are bonded in a hydrogen environment at 140 °C. Scanning acoustic microscopy (SAM) analysis is used to evaluate the joint quality. This bonding technique consistently achieves uniform and void-free joints. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analyses also are performed on the joint cross sections. The SEM image shows a uniform joint thickness of 5 μm and the joint microstructure. SEM and EDX results indicate the joint consists of In–Sn alloy with embedded AuIn2 grains. The re-melting temperature of the joint is found to be 125–150 °C, which shows that the joint composition is not exactly eutectic that has a melting temperature of 118 °C, but rather is Sn-rich. The success of this design illustrates the solid-state interdiffusion between Sn and In to form a thin layer of Sn–In eutectic alloy. The fluxless feature of this technology is valuable for bonding and assembling many emerging photonic devices that simply cannot tolerate fluxes. [Copyright &y& Elsevier]
- Subjects :
- *INDIUM
*TIN
*EUTECTIC alloys
Subjects
Details
- Language :
- English
- ISSN :
- 09215093
- Volume :
- 333
- Issue :
- 1/2
- Database :
- Academic Search Index
- Journal :
- Materials Science & Engineering: A
- Publication Type :
- Academic Journal
- Accession number :
- 7826165
- Full Text :
- https://doi.org/10.1016/S0921-5093(01)01815-9