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G. Siroky, J. Magnien, D. Melinc, E. Kozeschnik, D. Kieslinger, E. Kraker, W. Ecker:
"Lap shear test for solder materials: Local stress states and their effect on deformation and damage";
Microelectronics Reliability, 109 (2020), 113655; 1 - 11.

This work presents a detailed analysis of stress states and different strain measures of two lap-shear sample
designs. The stress- and strain distribution are discussed for both sample designs through numerical simulation.
Additionally in-situ measurements of lap-shear experiments are performed to compare the large strain and
damage behavior of the different sample designs. Despite the use of in-situ video-extensometer strain measurements,
a deviation among elastic moduli from tensile- and lap-shear experiments is observed. Finite element
analysis reveals that inhomogeneous strains due to boundary effects are the reason for the observed moduli
deviation. A strain correction method is presented to correct video-extensometer measurements. The parameters
of the correction function were obtained from numerical simulation and are provided for several sample dimensions.
To illustrate the effectiveness of the proposed strain correction method, the correction function is
applied to experimental lap-shear test data. The corrected shear moduli compare well with shear moduli calculated
from tensile tests reported in literature.
1. Introduction
The analysis of shear, creep and thermal fatigue behavior of solder
alloys is often done via lap-shear tests. This allows to determine material
properties under shear dominated loads [1-4]. There are no
specific standards for lap-shear samples with respect to materials
testing. Therefore, several sample designs with variation in shape and
dimension are common in material testing of solders. The lap-shear test
characterizes the shear- and interfacial strength of solder joints [5-9]. A
great number of studies exist that illustrate the strength and elastic
deformation of bonded lap-shear joints through simulation and experiments
[4,10-14], focusing on the structural behavior of the components
but not on determining material properties of the joints. Experimental
studies of Zimprich et al. [13] showed that measured
properties depend on the sample design. The solder dimensions such as
thickness t and length l play an important role for the loading condition
[13-15].
Video-extensometer (VE) strain measurements are often used for insitu
studies of lap-shear experiments [9,12,16]. The VE measures displacements
of patterns on the sample surface and displacements are
subsequently used

Lap-shear test, Solder material, In-situ measurements, Strain correction, Finite element modeling, Local stress analysis

http://dx.doi.org/10.1016/j.microrel.2020.113655