Temperature Slope
Temperature differences measured per unit distance across lamination stacks govern heat transfer rates into multilayer dielectric prepregs. During multilayer board pressing, press thermal gradient dictates the rate of heat penetration from heated platens through separator plates into central laminate layers. Multi-point embedded thermocouples record internal temperatures across time to calculate thermal transfer rates.
Excessive temperature slopes between outer and inner panels induce differential resin flow and curing rates.
Heat Propagation
Stack thickness and separator plate material conductivity control heat delivery into inner panel layers. Steep press thermal gradient values trigger rapid outer-layer resin curing before inner-layer resin achieves fluidity.
Lamination Stress
Thermal gradients across multilayer book stacks produce severe internal mechanical stresses during cooling phases. Asymmetric cooling across dielectric layers causes panel bow and twist defects after release from the lamination press. Large temperature drops between center panels and outer panels result in inconsistent glass transition temperatures within a single press load.
Optimizing ramp rates and incorporating thermal buffer pads flattens internal thermal slopes, ensuring uniform resin melt across all panels. Controlled heating profiles prevent copper foil wrinkling and micro-delamination along inner-layer interfaces. Maintaining balanced thermal profiles across lamination stacks yields dimensionally stable multilayer printed circuit boards.
