TY - JOUR
T1 - A fluxless fabrication process producing Sn-rich Bi - Sn joints with high melting temperature
AU - Lee, Chin C.
AU - Chuang, Ricky W.
AU - Kim, Dong W.
N1 - Funding Information:
The fluxless bonding research project is funded by Jet Propulsion Laboratory (JPL) and NASA System-On-A-Chip (SOAC) program.
Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2004/6/15
Y1 - 2004/6/15
N2 - A fluxless bonding process to produce tin-rich bismuth-tin solder joints is presented. The process was designed using Sn-Bi multilayer structure deposited in high vacuum to inhibit oxidation and to achieve the fluxless feature. The composition was chosen to be tin-rich, 95.0 wt.% Sn and 5.0 wt.% Bi, to achieve a solidus temperature significantly higher the 139 °C eutectic temperature of the 57Bi-43Sn eutectuic alloy. The resulting joints were imaged with a scanning acoustic microscope (SAM) and shown to be nearly void-free. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were used to study the microstructure and compositions of the joints. The measured joint thickness was 4.1 μm. SAM and EDX results indicate that the solder joint consists of (β-Sn) matrix embedded with small grains of (Bi) solid solution phase. The melting temperature of the joint was measured to be 210-215 °C, as expected from the designed composition. The fluxless feature of this process gives the packaging community another process to consider for use in devices and packages where the use of flux is prohibited, such as some biomedical, MEMs, fiber optical and photonic devices.
AB - A fluxless bonding process to produce tin-rich bismuth-tin solder joints is presented. The process was designed using Sn-Bi multilayer structure deposited in high vacuum to inhibit oxidation and to achieve the fluxless feature. The composition was chosen to be tin-rich, 95.0 wt.% Sn and 5.0 wt.% Bi, to achieve a solidus temperature significantly higher the 139 °C eutectic temperature of the 57Bi-43Sn eutectuic alloy. The resulting joints were imaged with a scanning acoustic microscope (SAM) and shown to be nearly void-free. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were used to study the microstructure and compositions of the joints. The measured joint thickness was 4.1 μm. SAM and EDX results indicate that the solder joint consists of (β-Sn) matrix embedded with small grains of (Bi) solid solution phase. The melting temperature of the joint was measured to be 210-215 °C, as expected from the designed composition. The fluxless feature of this process gives the packaging community another process to consider for use in devices and packages where the use of flux is prohibited, such as some biomedical, MEMs, fiber optical and photonic devices.
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U2 - 10.1016/j.msea.2004.03.011
DO - 10.1016/j.msea.2004.03.011
M3 - Article
AN - SCOPUS:2642588187
VL - 374
SP - 280
EP - 284
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
IS - 1-2
ER -