In the copper-clad laminate lamination production process, white base is a common defect that occurs frequently on-site, mainly manifested as local whitening of the board surface, uneven base material, and abnormal light transmission. White base not only affects the appearance grade (visible directly on single-sided panels) but also easily leads to insufficient density of the board, laying the groundwork for delamination, poor pressure resistance, and other potential problems.
The core causes of white base and the on-site improvement countermeasures are summarized as follows:
1. Main causes of white base
1.1 PP gel time (GT) is too low
Using semi-cured sheets with GT values below the operation limit causes the resin to react too quickly and prematurely cure, resulting in insufficient flow and infiltration, and the glass fiber pores cannot be filled, leading to the formation of white base on the board surface.
1.2 Unreasonable pressurization timing during lamination
The transition to full pressure occurs too early, when the resin is in a viscoelastic state, and full pressure is applied. At this time, the resin has poor fluidity and cannot be fully spread and filled, causing the base material to be loose and the board surface to become white.
1.3 Poor consistency in PP weft and warp directions
The same sheet of PP has large deviations in PPW and GT locally, resulting in uneven resin distribution and inconsistent lamination reactions, leading to local white base and color patterns on the base material.
2. Improvement countermeasures (can be directly implemented on-site)
2.1 Strictly control PP GT parameters
All incoming PP must be within the operation plan GT range. Strictly prohibit the use of low-GT materials. This can prevent resin from curing too quickly, which causes white base, from the source.
(For low-GT semi-cured sheets, they go through the process of process review and special board consumption)
2.2 Optimize lamination process curve
Adjust the lamination transition to full pressure point, avoiding the resin in the viscoelastic zone, ensuring that full pressure is applied in the resin's viscous and flowable zone, to ensure that the resin is fully infiltrated, filled, and compacted.
2.3 Control the consistency of PP weft and warp directions
Strengthen incoming material inspection, strictly control the deviation of local and overall indicators of a single sheet of PP, and isolate the use of batches with large differences in the weft and warp directions and poor stability to reduce local whitening defects.
3. Summary
The essence of white base defects is abnormal PP indicator parameters + improper lamination timing, resulting in insufficient resin infiltration.
By stabilizing PP GT indicators, optimizing lamination processes, and controlling material consistency, white base defects can be effectively reduced, stabilizing the board surface appearance and the intrinsic