Package Substrate Recessed Solder Mask Structure Against Undercut Peeling
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Solution Overview
Problem
Conventional package substrates suffer from poor reliability due to the formation of large undercut structures in the solder mask design, leading to peeling off of the insulating protective layer.
Innovation Solution
The insulating protective layer is designed with non-solder mask definition (NSMD) such that it is bonded to or received in recessed portions, eliminating the need for solder mask material on the surface, thereby preventing excessive undercut structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-solder mask defined (NSMD) design is used with solder mask material disposed on the surface of the dielectric layer around the opening, then the insulating protective layer can be formed, but large undercut structures are produced causing the bottom of the insulating protective layer to peel off
Solution Approach 1:
The patent introduces a recessed portion that extends downward from the surface of the dielectric layer into the bulk material. This vertical dimensionality change allows the insulating protective layer to be supported by the recessed structure rather than relying solely on surface adhesion, thereby preventing peeling while maintaining NSMD design benefits
Solution Approach 2:
The recessed portion acts as an intermediary structure between the dielectric layer and the insulating protective layer. It provides mechanical support and a bonding interface that prevents direct peeling of the insulating protective layer from the dielectric layer surface, resolving the adhesion problem without requiring traditional solder mask defined designs
Data Source
AI summary
A package substrate is provided, which includes an insulating protective layer formed on a circuit structure, wherein circuit structure includes an insulating layer and a first circuit layer bonded to the insulating layer, and the insulating layer has at least one recessed portion, so that the insulating protective layer is bonded to a bonding layer formed in the recessed portion, or the insulating protective layer is received in the recessed portion and protruded from the recessed portion. Therefore, when the insulating protective layer is designed as NSMD, the portions around the openings will not be disposed on the surface of the insulating layer to avoid excessive undercut structures in the insulating protective layer. Also provided is a manufacturing method for the package substrate.