Stacking process (4)

The key terms of the pressing process are as follows:

 

Heating Rate: This refers to the speed at which heat is raised over a certain period. It is necessary for prepreg forming since heat is required for the process.

 

1st Step Heat: This is the point where actual prepreg forming occurs. The temperature at this point is determined using viscosity data. Appropriate pressure should be applied at this stage.

 

Peak Temperature: After the prepreg forming is complete, cross-linking reactions (formation of intermolecular bonds) take place, and the resin fully solidifies.

 

Pre-Pressure: When applying curing pressure directly, it can lead to stress on the product, causing problems like interlayer distortion. Pre-pressure is applied to mitigate the impact before the curing pressure is applied.

 

Pressure: Pressure is necessary to improve the adhesion of prepreg and to extract air bubbles within the prepreg. Higher pressure increases resin flow, but there is a risk of dimensional changes, resin depletion, and inadequate thickness at high pressure. On the other hand, lower pressure reduces resin flow and makes void removal difficult.

 

Vacuum: During prepreg forming, vacuum is used to remove inherent air bubbles within the product and to eliminate gases generated from the resin due to high temperature, preventing the formation of marks on the copper foil.

 

Actual Profile: This refers to the actual temperature graph that the product experiences when the programmed profile is applied to the product.