Case 140 · Public preview
Reflow Contraction Can Overstress an Otherwise Normal-Looking LED Bond
Post-assembly LEDs developed intermittent electrical failures even though failed and control bond geometries appeared broadly similar.
Optical microscopyCross-sectioningSEMFailed-control comparison
What the evidence preview establishes
The LED wire failed in shear at the heel of the wedge bond on the post. Thermal contraction after reflow, acting through a structure with limited thermal stability, was the most credible source of mechanical stress.
Why this case matters
A sound-looking bond can fail when package members move relative to one another. Evaluate wire routing, post and die-cup geometry, encapsulant constraint, reflow contraction, and tolerance stack-up—not only the local bond appearance.
Full evidence reserved for MEMBER and STOREThe complete case includes the evidence sequence, four interpreted figures, alternative explanations, limitations, and practical application guidance.