The reliability of solder joints, crucial for electronic assemblies, is influenced
by factors including intermetallic compound (IMC) growth during aging and surface
properties. This study investigated the impact of atmospheric plasma pre-treatment
on the shear strength and IMC formation of aged (thermal aging and thermal shock)
SAC305 solder joints on various PCB finishes (Cu, ImT, HASL, ENIG). Shear testing
revealed that plasma treatment had a limited effect on mechanical strength under the
applied test conditions. Fracture mode analysis indicated that failures predominantly
occurred at the component’s lead metallization, suggesting that component quality
was the limiting factor, masking potential effects of the plasma treatment applied
to the PCB pads. Thermal shock aging was observed to be more detrimental to joint
strength than thermal aging, particularly affecting the component-level integrity.
IMC analysis showed expected growth with thermal aging. Plasma treatment had negligible
impact on IMC thickness for ENIG finish, while an unexpected trend of reduced IMC
thickness was observed for HASL finish, warranting further investigation. The study
highlights the critical role of component robustness in reliability testing and suggests
its potential to overshadow the influence of PCB surface treatments.
