Wiring Substrate Pad Peeling Prevention via Inverted Groove
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wiring substrates lack a structure to prevent peeling of pads, which can occur during bonding with semiconductor chips or after bonding.
Innovation Solution
A wiring substrate design featuring an insulating layer, a wiring layer, a first metal layer, a solder resist layer with open portions exposing the first metal layer, and additional metal layers formed on top, where the solder resist layer covers the outer periphery of the first metal layer to prevent peeling and suppress plating solution flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pad is formed on the wiring layer to project from the solder resist layer for bonding with semiconductor chips, then bonding capability is improved, but the pad is prone to peeling during or after bonding
Solution Approach 1:
The invention extends the pad structure into a third dimension by forming an inverted groove that recesses beneath the wiring layer surface. This dimensional extension creates a mechanical interlock structure where the pad material fills the groove and bonds to both the wiring layer above and the support layer below, preventing peeling while maintaining bonding capability.
Solution Approach 2:
The pad structure is segmented into multiple functional zones: the upper pad surface for bonding, the inverted groove for mechanical anchoring, and the support layer for structural reinforcement. This segmentation allows each zone to perform its specific function optimally - bonding, anchoring, and supporting - thereby preventing peeling while maintaining ease of bonding.
2Reliability
If the solder resist layer completely covers the first metal layer for protection, then protection is improved, but the pad cannot be accessed for bonding
Solution Approach 1:
The solder resist layer is applied with local quality variation - it completely covers the first metal layer in most areas for protection, but selectively exposes the pad region through the inverted groove structure. This allows the pad to be accessible for bonding while the rest of the metal layer remains protected by the solder resist.
Solution Approach 2:
The inverted groove acts as an intermediary structure that reconciles the conflicting requirements of protection and accessibility. The groove allows the pad to protrude through the solder resist layer, creating a localized access path while maintaining overall coverage and protection of the metal layer.
3Reliability
If plating solution is applied to form additional metal layers, then bonding performance is improved, but plating solution may flow under the solder resist and damage lower layers
Solution Approach 1:
The inverted groove structure is formed beforehand to create a physical barrier that prevents plating solution from flowing under the solder resist layer. This preliminary structural preparation ensures that when plating solution is subsequently applied for forming additional metal layers, it remains contained and cannot reach and damage the lower wiring layers.
Solution Approach 2:
The potential harmful flow of plating solution is converted into a beneficial contained plating process. The inverted groove structure that initially seems to add complexity actually prevents the harmful effect of solution leakage while concentrating the plating solution where it is needed - on the pad surface - thereby improving bonding performance.
Data Source
AI summary
A wiring substrate includes a first metal layer formed on a wiring layer; a solder resist layer that covers the wiring layer and the first metal layer, and is provided with an open portion that exposes a part of an upper surface of the first metal layer; a second metal layer formed on the upper surface of the first metal layer that is exposed within the open portion; and a third metal layer formed on the second metal layer, wherein the solder resist layer covers an outer peripheral portion of the upper surface of the first metal layer to expose the part of the upper surface of the first metal layer within the open portion, and wherein an upper surface of the second metal layer is flush with an upper surface of the solder resist layer or projects from the upper surface of the solder resist layer.