To read the full version of this content please select one of the options below:

Characterization of Sn7In4.1Ag0.5Cu solder in lead‐free composite solder joints of LTCC/PWB assembly

O. Nousiainen (Materials Engineering Laboratory and EMPART Research Group of Infotech Oulu, University of Oulu, Oulu, Finland)
T. Kangasvieri (Microelectronics and Materials Physics Laboratories and EMPART Research Group of Infotech Oulu, University of Oulu, Oulu, Finland)
R. Rautioaho (Materials Engineering Laboratory and EMPART Research Group of Infotech Oulu, University of Oulu, Oulu, Finland)
J. Vähäkangas (Microelectronics and Materials Physics Laboratories and EMPART Research Group of Infotech Oulu, University of Oulu, Oulu, Finland)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 27 June 2008

Abstract

Purpose

The purpose of this paper is to present a novel Sn7In4.1Ag0.5Cu/Plastic Core Solder Ball/Sn4Ag0.5Cu composite solder joint configuration for second‐level ball grid array (BGA) interconnections of low temperature co‐fired ceramic (LTCC) modules and the thermal fatigue durability of the configuration. The purpose of using the Sn7In4.1Ag0.5Cu solder was to increase the creep/fatigue resistance of critical regions on the LTCC side of the joint.

Design/methodology/approach

Test LTCC module/printed wiring board (PWB) assemblies were fabricated and exposed into temperature cycling tests over the 0 to 100°C and −40 to 125°C temperature ranges. The characteristic lifetimes of these assemblies were determined using DC resistance measurements. The failure mechanisms of the test assemblies were verified using scanning acoustic microscopy, FE‐SEM, and SEM investigation.

Findings

The test assemblies were exposed to thermal cycling tests (TCT) over test ranges of 0 to 100°C and −40 to 125°C, and characteristic lifetimes of over 5,500 and 1,400 cycles, respectively, were achieved. Compared with Sn4Ag0.5Cu/plastic‐core solder balls (PCSB)/Sn4Ag0.5Cu joints, the characteristic lifetime of the SAC‐In/PCSB/SAC joints increased over 55 per cent in the harsh (−40 to 125°C) TCT conditions. In the milder test conditions (0 to 100°C), the characteristic lifetime of the SAC‐In/PCSB/SAC joints increased 30 per cent compared with the SAC/PCSB/SAC joints.

Originality/value

The results proved that the enhanced creep/fatigue properties of the solder matrix resulted in satisfactory lifetime durations in the present lead‐free composite solder joints and, consequently, different primary failure mechanisms on the LTCC side due to the use of indium alloyed solder. Thus, the present joint configuration is assumed to be a promising solution for the further design of a reliable second‐level solder interconnection in LTCC/PWB assemblies with a high‐global thermal mismatch.

Keywords

Citation

Nousiainen, O., Kangasvieri, T., Rautioaho, R. and Vähäkangas, J. (2008), "Characterization of Sn7In4.1Ag0.5Cu solder in lead‐free composite solder joints of LTCC/PWB assembly", Soldering & Surface Mount Technology, Vol. 20 No. 3, pp. 11-17. https://doi.org/10.1108/09540910810885679

Publisher

:

Emerald Group Publishing Limited

Copyright © 2008, Emerald Group Publishing Limited