Bonding Process
Polyimide or high glass transition temperature epoxy resins require elevated thermal cycles to crosslink during the layup phase of multilayer fabrication. High temperature lamination describes this stage where hydraulic presses apply controlled pressure at temperatures exceeding 170 degrees Celsius to achieve dielectric consolidation. The press parameters ensure that resin flow fills gaps between copper features while removing entrapped air.
Thermal Mechanics
Voids within the laminate structure pose significant reliability risks during subsequent soldering operations because trapped moisture expands rapidly when exposed to reflow oven profiles. This specific lamination sequence drives the polymer conversion to a solid state that resists mechanical failure during thermal shock or vibration. Fabricators adjust the duration of the heat soak based on the specific resin chemistry provided by the supplier.
Longer hold times allow the adhesive to achieve optimal molecular weight before cooling begins under pressure.
Verification Standards
Electrical integrity and mechanical stability depend upon the prevention of delamination between the prepreg and inner layer cores after the assembly process concludes. Cross-sectional analysis under magnification confirms the absence of air pockets or incomplete resin curing. A microsection prepared from a coupon reveals if the resin flow properly wetted the copper surface at the specified pressure.
Adherence to these temperature profiles prevents board warping and maintains the flatness required for automated component placement equipment.
