Adhesion Promoter Layer for Flip Chip Underfill Flow

The patent removes the solder mask layer from the substrate surface in the die attach area to increase the gap between the IC die and substrate, enabling proper underfill flow. This extraction of the solder mask layer from the specific region resolves the contradiction by prioritizing gap size for underfill flow while accepting that adhesion must be maintained through alternative means (adhesion promoter layer or surface roughening) applied to the exposed metal surface.

The patent applies local quality by selectively removing the solder mask layer only in the die attach area where the IC die will be mounted, while potentially retaining it in other areas. This localized modification increases the gap precisely where needed for underfill flow without compromising adhesion in other regions. The adhesion promoter layer or surface roughening is also applied locally to the exposed metal surface in the die attach area to maintain adhesion properties.

The patent employs parameter changes by modifying the surface properties of the substrate metal through adhesion promoter layer deposition or surface roughening processes. These treatments alter the surface energy, chemistry, or topography to enhance adhesion. The contradiction is resolved by applying these treatments to the exposed metal surface after solder mask removal, ensuring that the thin adhesion promoter layer or surface modification does not significantly reduce the already increased gap, while still providing the necessary adhesion enhancement.