Adhesive Voids and CTE Mismatch Can Consume Heater-Assembly Thermal Margin

What the evidence preview establishes

X-ray and microsection evidence showed voids and fractures in both the heat-transfer adhesive and resistor enamel. These features increased thermal impedance and reduced design margin, but they were present in both passing and failing assemblies.

Why this case matters

A passing control can contain the same developing damage as a failed unit. When thermal margin is narrow, degree and distribution of porosity, interfacial damage, power application, and accumulated service damage may matter more than the presence of one defect.