Meaning
Structural material defects occurring between laminate layers in printed circuit boards cause mechanical separation during thermal stress. Printed circuit board delamination weakens dielectric isolation and fractures conductive copper traces during reflow soldering operations. The scope covers physical separation of resin or glass weave layers, terminating where external physical cracking of outer soldermask begins.
Physical Mechanism
Moisture trapped inside internal fiberglass weaves vaporizes rapidly when circuit boards enter high-temperature reflow ovens. Expanding steam exerts intense localized pressure against internal resin bonds, exceeding interfacial adhesion strength. Microscopic voids expand into broad internal blisters that detach inner copper planes from surrounding prepreg layers.
Defect Root
Inadequate surface preparation before lamination leaves chemical residues or oxidation on copper foil surfaces. Insufficient resin curing during lamination cycles leaves unreacted polymers that degrade when exposed to assembly temperatures. Storage in high-humidity factory environments accelerates moisture absorption through board edges, rendering raw circuit boards vulnerable to thermal expansion forces.
Fabrication facilities mitigate risks by enforcing strict desiccation storage and optimizing lamination press cycles. Incoming material inspections utilize thermal stress tests to detect sub-surface weakness prior to component assembly.
Microscopic Inspection
Quality assurance technicians utilize acoustic microscopy or cross-sectional microsectioning to identify internal separations. Acoustic reflection signals reveal hidden air gaps between layers without destroying circuit boards. Microsection polishing exposes interfacial fracture lines under optical microscopes for root cause analysis.
