Isotropic conductive adhesives (ICA) have been considered as replacement materials for lead-tin solder alloys. In this paper, the post-impact shear strength of ICA surface mount (SM) joints was obtained experimentally and compared with that of SM lead-tin joints. The dynamic impact energy was provided in the form of three-point bending on the PCB using equipment called the split Hopkinson bar. Strain rates of over 4000/s were used for the impact bending test. The action of impact bending was used to simulate the effect on the PCB and the interconnection as a result of high energy impact on an electronic equipment. Shear test was then performed to examine the change in strength of the ICA joints as a result of impact damage. It was found that the SM ICA joints failed due to impact at a strain rate just over 4000/s. Microstructural examination carried out using a scanning electron microscope revealed that the interface between the ICA and copper pad on the PCB was the weakest region of the joint.

Issue Section:
Technical Papers
Keywords:
surface mount technology, printed circuit testing, bending, impact testing, impact strength, adhesives, shear strength, interconnections, circuit reliability, scanning electron microscopy, failure (mechanical)
Topics:
Adhesives, Copper, Fracture (Materials), Impact testing, Reliability, Shear (Mechanics), Shear strength, Solders, Silver, Resistors, Alloys, Failure, Testing, Damage, Scanning electron microscopes, Surface mount packaging, Surface mount technology, Stress, Circuits, Compression, Electronic equipment, Impact strength, Scanning electron microscopy
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Copyright © 2002
 by ASME
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