Epoxy Strain Transfer Efficiency Loss under Cyclic Thermal Loading
Cyclic thermal loading degrades epoxy shear modulus, causing strain transfer loss that demands strict bondline guard-banding in technical files.
In-Situ Interrogation
Thermal Verification
Board fabrication requires precise control over inner layer registration and dielectric thickness before lamination locks the stackup into a permanent laminate. In-situ interrogation evaluates internal temperatures and stress profiles dynamically while the press cycle applies heat and pressure. Thermocouples embedded directly within the test coupon substrate record localized exothermic excursions during resin polymerization.
Measuring actual board temperatures instead of relying on platen feedback prevents premature gelation or void formation in high layer count printed circuit boards.
Structural Mapping
Automated optical inspection and cross sectioning catch geometric defects after the press cycle finishes, but structural degradation during reflow soldering often stems from hidden laminate voids. In-situ interrogation detects internal delamination and fiber weave skew by monitoring acoustic impedance shifts during thermal transients. Piezoelectric sensors coupled to the press platens capture ultrasonic reflections continuously throughout the cure schedule.
Analyzing wave attenuation patterns exposes localized resin starvation before destructive testing confirms the structural failure mode.
Electrical Continuity
Final electrical testing verifies open circuits and short circuits on finished printed circuit board assemblies, but intermittent faults during thermal cycling originate from compromised barrel plating in microvias. In-situ interrogation measures dynamic resistance changes across plated through holes while thermal shock chambers subject the assembly to rapid temperature swings. High speed data acquisition hardware logs millivolt drops continuously to isolate microcrack propagation in copper plating.
Detecting resistance spikes during thermal loading separates robust interconnects from latent assembly failures.