TB 26-10 Printed Circuit Board Assembly Chip Resistor Body Cracking

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Briefings

Two thick-film chip resistors on identical NASA printed circuit boards cracked during thermal cycling after vibration testing, exhibiting transverse fractures at the mid-span. Independent failure analyses ruled out defective lots and fatigue, identifying board flexure, component orientation, excessive solder, and mounting stresses as contributing factors. The incident occurred in 2026 during environmental acceptance testing on two identical boards with resistors installed near the board edge.

Key points

Two thick-film chip resistors on identical NASA printed circuit boards cracked during thermal cycling after vibration testing, exhibiting transverse fractures at the mid-span.

Failure analyses ruled out defective lots and fatigue, identifying board flexure, component orientation, excessive solder, and mounting stresses as contributing factors.

Context

Chip resistors are ubiquitous across NASA projects, yet cases of alumina substrate cracking during environmental testing are rare. This incident involved two instances of thick-film chip resistor cracking observed during thermal cycling after vibration testing on identical boards, highlighting specific assembly risks for large footprint ceramic components near board edges.

Limitations

Evidence covers only two specific instances of thick-film chip resistor cracking on identical NASA boards. No additional background on historical NESC reporting or broader industry practices is supplied. The causal relationship between board flexure and component orientation remains unverified without further testing. The bulletin is a recommendation rather than a confirmed root cause report.

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