Material Sequence
Structural sequencing of resin-impregnated glass cloth and copper foils forms the basis of multilayer circuit board construction. A composite panel lay-up involves the precise stack of core materials and prepreg sheets in a symmetrical arrangement to prevent mechanical instability during lamination. This order ensures that the final thickness meets electrical impedance requirements and physical board specifications.
Press Cycle
Vacuum pressing bonds the individual layers into a solid mass through the application of heat and hydraulic force. The composite panel lay-up dictates the flow of resin into the inner layer copper patterns during the fluid stage of the cure cycle. Proper alignment of the grain in the glass fabric across the stack reduces the risk of internal registration errors during the pressing stage.
If the sequence is asymmetrical, the unequal distribution of tension leads to warping or twisting of the finished panel.
Dimensional Stability
Material properties like the resin content and the glass style define the limits of the bonding process. Large panels require specific tacking methods to keep the composite panel lay-up from shifting as the stack enters the press. Excess resin squeeze out during the cycle indicates an incorrect pressure setting or a misalignment of the layer boundaries.
