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Failure Mechanism of the SnAgCu/SnPb Mixed Soldering Process in a Ball Grid Array Structure
- Source :
- Journal of Electronic Materials. 49:6223-6231
- Publication Year :
- 2020
- Publisher :
- Springer Science and Business Media LLC, 2020.
-
Abstract
- In this study, the influence of different reflow profiles and dosages of SnPb solder paste on the reliability of the SnAgCu/SnPb mixed assembly process was investigated. The interfacial microstructures were carefully examined through scanning electron microscopy, and two failures modes were found. Firstly, when reflowed at 245°C for 95 s, Pb-rich phases were buried within an intermetallic compound (IMC) layer and led to micro-voids and cracks under thermal stress or mechanical stress. However, upon increasing the reflow temperature or time further led to melting the solder ball totally, and the Pb element dissolved into a liquid phase and precipitated into uniform and small granules during the cooling process. Further, among the samples with different dosages of SnPb solder paste, severe shrinkage occurred at the solder joints with the addition of 12 wt.% eutectic SnPb component. Electron back-scattered diffraction analysis was conducted in order to determine the mechanism of different shrinkages. The solder ball consisted of several primary Sn grains, and the shrinkage and Pb-rich phase are preferred to appear at the grain boundary. When the solder ball consisted of a single grain, no preferred orientation of the shrinkage and Pb-rich phase were detected. The shrinkage appeared at the final solidification region, which is near the IMC layer. Moreover, the shrinkages connect to each other, and a continuous crack formed on the chip side, leading to the failure.
- Subjects :
- 010302 applied physics
Materials science
Intermetallic
Solder paste
02 engineering and technology
021001 nanoscience & nanotechnology
Condensed Matter Physics
Microstructure
01 natural sciences
Electronic, Optical and Magnetic Materials
Ball grid array
Soldering
0103 physical sciences
Materials Chemistry
Grain boundary
Electrical and Electronic Engineering
Composite material
0210 nano-technology
Shrinkage
Eutectic system
Subjects
Details
- ISSN :
- 1543186X and 03615235
- Volume :
- 49
- Database :
- OpenAIRE
- Journal :
- Journal of Electronic Materials
- Accession number :
- edsair.doi...........15b40d3644ae8b9e9722d827bea71ca7