Non-Newtonian Flow Dynamics in Thin Prepreg Dielectric Micro-Channels
Non-Newtonian resin flow inside thin prepreg micro-channels governs void formation, trace displacement, and dielectric thickness stability during high-pressure lamination.
Vacuum Dwell Time
Lamination Process
The duration of the low-pressure stage applied during multilayer lamination ensures the extraction of trapped air from the stackup. Adjusting the vacuum dwell time is essential to prevent micro-voids from forming between internal trace layers as the prepreg begins to melt. This process parameter is managed within the lamination press program.
Void Elimination
Before the application of mechanical press force, a high-vacuum pump draws air and volatile gases out of the layered board stackup. The vacuum dwell time must be long enough to clear all moisture and entrapped air, especially around thick copper traces where gaps are large. If the duration is too short, residual air will be trapped as the resin liquifies, leading to voids that will expand and cause delamination when the board undergoes solder reflow.
The pre-vacuum phase typically lasts between thirty and sixty minutes depending on the board’s complexity. Once the dwell time is complete, the press begins to apply mechanical pressure and high heat to cure the resin.
Yield Assurance
Proper void extraction improves the long-term reliability of the multilayer stack by preventing the thermal and mechanical stresses that cause failures. Inspecting sample boards with cross-sectioning verifies that the lamination is fully dense and void-free. This optimization ensures a high manufacturing yield for high-layer count boards.