University of Oulu

J. Putaala et al., "Power Module Interconnection Reliability in BTS Applications," in IEEE Transactions on Device and Materials Reliability, vol. 19, no. 3, pp. 484-493, Sept. 2019. doi: 10.1109/TDMR.2019.2920316

Power module interconnection reliability in BTS applications

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Author: Putaala, Jussi1; Hagberg, Juha1; Kangasvieri, Tero2;
Organizations: 1Microelectronics Research Unit, University of Oulu, Oulu, Finland
2Research and Development, Nokia, Oulu, Finland
3Research and Development, Nokia Bell Labs, Espoo, Finland
4Research and Development, Nokia, Espoo, Finland
5Materials and Mechanical Engineering Unit, University of Oulu, Oulu, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 1.3 MB)
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Language: English
Published: Institute of Electrical and Electronics Engineers, 2019
Publish Date: 2019-09-20


In this paper, the reliability of RF power transistors’ solder attachments is characterized through experiments and simulations. Test cases consisted of power amplifier (PA) modules on AlSi10Mg substrates with either a low or high mutual thermal mismatch. The module’s flange interconnections were stressed by means of thermal cycling testing (TCT) in the 15 °C–95 °C range. Scanning acoustic microscopy (SAM) was used intermittently to inspect the interconnections of selected structures during cycling breaks. Optical cross-polarization microscopy and scanning electron microscopy were used in the failure analysis of the solder joints. Different materials and dimensional variations were tested in simulations to observe differences in thermal stress. The viscoplastic behavior of lead-free solder in the interconnection was modeled using Anand’s constitutive equations. The first cracks could be observed with SAM after 100 cycles. SAM imaging showed that in the worst case, 72% of the interconnection area had cracked at the end of the 1100-cycle TCT. Only a marginal amount of cracks could be observed in PA modules with a better coefficients of thermal expansion match to the substrate. Simulations indicated that it is possible to decrease creep energies significantly and thereby increase the lifetime expectancy of interconnections by selecting the correct materials and structures.

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Series: IEEE transactions on device and materials reliability
ISSN: 1530-4388
ISSN-E: 1558-2574
ISSN-L: 1530-4388
Volume: 19
Issue: 3
Pages: 484 - 493
DOI: 10.1109/TDMR.2019.2920316
Type of Publication: A1 Journal article – refereed
Field of Science: 213 Electronic, automation and communications engineering, electronics
216 Materials engineering
222 Other engineering and technologies
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