Redistribution Substrate Dummy Pattern for UBM Pad Undulation
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Solution Overview
Problem
Existing semiconductor packages face issues with undulation in the redistribution layers due to the large thickness and spacing of under bump metallurgy (UBM) pads, leading to potential failures such as shorts during the curing shrinkage process of the insulating layer.
Innovation Solution
Incorporating a dummy pattern between the UBM pads in the insulating member, which is positioned at a higher level than the UBM pads, to reduce the thickness deviation and spacing, thereby stabilizing the insulating layer and preventing undulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spacing and thickness of UBM pads are increased, then the electrical connection capability is improved, but the insulating layer becomes unstable and undulation occurs during curing shrinkage
Solution Approach 1:
A dummy pattern is introduced as an intermediary element between the UBM pads. This dummy pattern acts as a mediator that fills the excessive spacing between pads, providing support to the insulating layer during curing shrinkage while maintaining the necessary electrical connection capability of the original UBM pad structure
Solution Approach 2:
The dummy pattern is selectively positioned only in the regions between UBM pads where spacing exceeds a predetermined threshold. This localized application maintains the original pad structure and electrical connections while addressing instability only where needed, preserving the functional quality of connected regions
2Stability of the object's composition
If the spacing between UBM pads is reduced, then the insulating layer stability is improved, but the electrical connection capability deteriorates
Solution Approach 1:
The spacing management is segmented into two distinct approaches: regions with excessive spacing receive dummy patterns to provide support, while regions with adequate spacing maintain their original UBM pad structure for optimal electrical connection. This segmentation allows each region to be optimized independently
3Strength
If the thickness of UBM pads is increased, then the electrical connection strength is improved, but the thickness deviation of the insulating layer increases causing undulation
Solution Approach 1:
The dummy pattern acts as a counterweight or compensating element that offsets the thickness deviation caused by thick UBM pads. By providing additional material in the spacing regions, the dummy pattern balances the overall thickness profile, preventing undulation during insulating layer curing while preserving the strength-providing thick pad structure
Data Source
AI summary
A semiconductor package includes a redistribution substrate having first and second surfaces, and an insulating member and a plurality of redistribution layers on different levels in the insulating member and electrically connected together; a plurality of under bump metallurgy (UBM) pads in the insulating member and connected to a redistribution layer, among the plurality of redistribution layers, adjacent to the first surface, the UBM pads having a lower surface exposed to the first surface of the redistribution substrate; a dummy pattern between the UBM pads in the insulating member, the dummy pattern having a lower surface located at a level higher than the lower surface of the UBM pads; and at least one semiconductor chip on the second surface of the redistribution substrate and having a plurality of contact pads electrically connected to a redistribution layer, among the plurality of redistribution layers, adjacent to the second surface.