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

Executive Briefing

According to reporting by NASA Space & Missions, For more information, contact Joel W. Sills, Langley Research Center, joel.w.sills@nasa.gov. Download PDF here Chip resistors are widely used in NASA projects, yet cases of alumina substrate cracking during environmental testing are rare. Two instances of.

Detailed Factual Report

For more information, contact Joel W. Sills, Langley Research Center, joel.w.sills@nasa.gov .

Chip resistors are widely used in NASA projects, yet cases of alumina substrate cracking during environmental testing are rare. Two instances of thick-film chip resistor cracking were observed during thermal cycling after vibration, with fractures occurring across the short axis due to bending. Failure analyses ruled out defective lots and fatigue, identifying board flexure, component orientation, excessive solder, and mounting stresses as contributing factors. The bulletin recommends careful component placement, finite element analysis, controlled solder fillet height, thorough inspection, and functional thermal shock testing to mitigate flexure-induced cracking risks in ceramic body components on printed circuit boards.

Causal Relationships Initial theories pointed to vibration-induced damage of potentially defective resistors since both resistors came from the same production lot. However, the resistor lot not only meets the requirements of procurement specification MIL-PRF-55342 but additional tests were performed and did not reveal any direct evidence of a defective resistor lot. There was no evidence of an elevated risk of defective resistors within the production lot.

Failure Analyses Independent failure analyses concluded that the cracked chip resistors were due to bending/tensile failures. There was no clear-cut root cause or visible defect identifying a crack initiation site. Both resistors exhibited a single, straight crack across the short axis (perpendicular to the long axis), indicating a bending/tensile failure without twisting.

Verified Data Points & Key Takeaways

Geographic Scope & Community Impact

Recommended Action & Safety Guidelines

Source & Verification Provenance

Information in this article was compiled directly from records provided by NASA Space & Missions. Access the primary source document at: https://www.nasa.gov/centers-and-facilities/nesc/tb-26-10-printed-circuit-board-assembly-chip-resistor-body-cracking/. Reporting and editorial review conducted by the USA NOW News Desk.