Constrained Solder Interconnect Pads for PCB Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solder interconnect pads on circuit boards are prone to delamination due to bending moments, leading to potential solder migration and shorts between adjacent conductor structures, which complicates increased routing density and manufacturing reliability.
Innovation Solution
Forming solder interconnect pads within openings in the solder mask, where the sidewall sets the lateral extent of the pad, eliminating interfaces between the pad and the mask and creating larger gaps to prevent delamination and shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional solder interconnect pads are formed with lateral dimension larger than solder mask hole, then manufacturing process is simpler, but solder mask delamination occurs due to bending moments
Solution Approach 1:
The patent extracts the problematic interface between the solder mask and bump pad upper surface by forming the solder interconnect pad within the solder mask opening such that the pad is substantially coextensive with the opening. This eliminates the exposed pad surface that was previously prone to delamination under bending moments.
Solution Approach 2:
The patent transitions from a conventional design where pads extend beyond mask holes in the lateral dimension to a design where pads are constrained within the mask opening boundaries. This dimensional constraint in the lateral direction prevents the formation of delamination-prone interfaces while maintaining vertical electrical connectivity.
2Reliability
If bump pads are enlarged to prevent delamination, then solder mask delamination is reduced, but packing density decreases
Solution Approach 1:
The patent uses the solder mask opening as a template or copy to define the exact lateral boundaries of the solder interconnect pad. By forming the pad to be substantially coextensive with the opening, the design achieves precise dimensional control without requiring enlarged pads, thereby maintaining high packing density while preventing delamination.
3Reliability
If greater conductor spacing is required to prevent shorts, then solder mask delamination is prevented, but routing complexity is reduced
Solution Approach 1:
The patent replaces the mechanical constraint of increased conductor spacing with a structural constraint where the solder interconnect pad is formed within the solder mask opening boundaries. This substitution maintains reliable electrical isolation and prevents shorts through the precise lateral confinement of the pad, enabling complex routing without compromising reliability.
4Ease of manufacture
If solder mask opening is vertically registered with bump pad, then manufacturing alignment is simpler, but interface between mask and pad creates delamination pathways
Solution Approach 1:
The patent extracts the harmful interface region by ensuring the solder interconnect pad does not extend beyond the solder mask opening boundaries. Even with vertical registration, the pad is confined within the opening, eliminating the exposed interface that would otherwise create pathways for solder migration and delamination.
Data Source
AI summary
Various circuit boards and methods of manufacturing the same are disclosed. In one aspect, a method of manufacturing is provided that includes forming a solder mask on a circuit board with a first opening that has a sidewall. A solder interconnect pad is formed in the first opening. The sidewall sets the lateral extent of the solder interconnect pad.