Registration Vector Analysis in Sequential High Density Core Lamination
Sequential core lamination registration requires X-ray target vector mapping and dynamic affine drill scaling to maintain zero breakout microvia alignment.
Prepreg Relaxation
Stress Release
Recovery of a semi cured resin sheet from the mechanical tensions induced during its manufacture leads to small changes in its physical dimensions. When the material is cut from a roll into individual sheets, prepreg relaxation occurs as the internal fibers and the resin matrix adjust to the lack of external pull.
Storage Condition
Temperature and humidity levels in the storage area greatly affect the speed of the movement. During prepreg relaxation, the moisture absorbed by the resin can cause the sheet to swell or contract before it is placed in the lamination press. Fabricators often allow the cut sheets to stabilize in a controlled environment for several hours before use.
This stabilization ensures that the material has reached a steady state and will not move unexpectedly during the layup process. Controlled storage racks prevent the material from sagging or stretching under its own weight.
Lamination Accuracy
If the sheets are pinned or bonded before the movement is complete, the resulting stress is trapped until the heat of the lamination cycle releases it. This delayed prepreg relaxation can cause the inner layers to shift out of alignment with the outer layer targets. Managing this effect is particularly important for thin materials used in flexible or rigid flex circuits.
The process of monitoring these changes stops once the resin reaches its gel point.