Board Mechanics
Drop-test method JESD22-B111 defines mechanical shock response testing for surface mount electronic components in surface mount technology assemblies. The specification evaluates solder joint reliability under high-impact conditions by mounting test boards to a rigid fixture and subjecting them to specified acceleration pulses. Peak table acceleration and pulse duration parameters dictate the severity of the shock event.
Component failure occurs when fracture develops across the intermetallic compound layer of the solder joint.
Solder Stress
Shock energy transfers through the printed circuit board assembly substrate, creating bending moments that load peripheral interconnects. Component corners experience maximum strain during board flexing events because displacement values peak furthest from the neutral axis. Stiff packages transmit higher forces to individual solder joints than compliant alternatives possessing similar footprints.
Solder alloy composition and reflow profile characteristics govern the elastic deformation limits of the attachment point.
Failure Criterion
Electrical discontinuity monitoring during the drop event isolates transient connection failures from permanent metallurgical rupture. Resistance spikes exceeding specific ohm thresholds for defined durations indicate internal cracking within the solder matrix. Destructive physical analysis via cross-sectioning confirms the crack propagation path following completion of the shock sequence.
Standardized testing parameters enable direct comparison of component robustness across different substrate thicknesses and pad designs.
