Open-Passivation BGA Pads for Reduced Dummy Area
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Solution Overview
Problem
The challenge in semiconductor fabrication lies in maintaining small feature sizes during the back-end-of-line processes, particularly in passive on glass technology, where high-performance components like inductors and capacitors are built on insulative substrates, leading to increased design complexity and cost due to dummy areas at die boundaries.
Innovation Solution
The implementation of open-passivation ball grid array pads, which involve a conductive bump assembly with a conductive bump pad supported by a passive substrate and surrounded by merged passivation layer openings, reduces the dummy area by removing the first passivation layer block between the bump pad and the dicing street, thereby minimizing the non-functional boundary area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional passivation layers are used to surround conductive bump pads, then the conductive bump pad is protected and isolated, but a dummy area is created at the die boundary increasing the footprint and cost
Solution Approach 1:
The patent extracts the first passivation layer block between the conductive bump pad and the dicing street, removing it entirely at the die boundary. This allows the second passivation layer opening to directly surround the conductive bump pad edge, eliminating the dummy area while maintaining protection through the remaining passivation structure.
Solution Approach 2:
The patent segments the passivation structure into multiple layers with different configurations. The first passivation layer is selectively removed at the boundary while the second passivation layer provides continuous protection. This segmentation allows the conductive bump pad to be protected where needed while eliminating unnecessary dummy areas at the die edge.
2Manufacturing precision
If passivation layers are maintained close to the dicing street, then manufacturing precision is improved, but the dummy area increases leading to higher cost
Solution Approach 1:
The patent removes the first passivation layer block that would otherwise extend to the dicing street, eliminating the dummy area and associated costs. The second passivation layer is positioned to provide necessary protection without requiring the expensive dummy area, thus reducing fabrication cost while maintaining adequate manufacturing precision.
3Productivity
If the conductive bump assembly footprint is reduced, then productivity and design efficiency improve, but maintaining protection and isolation becomes more difficult
Solution Approach 1:
The patent uses a multi-layer passivation structure where the first passivation layer provides protection in the bulk area and the second passivation layer provides protection at the boundary. This segmentation allows the footprint to be minimized while maintaining adequate protection through the coordinated arrangement of different passivation layers.
Solution Approach 2:
The patent transitions from a two-dimensional planar protection approach to a three-dimensional multi-layer passivation structure. By stacking passivation layers vertically and configuring them differently in the vertical dimension, the patent achieves protection with a smaller horizontal footprint, improving design efficiency while maintaining reliability.
Data Source
AI summary
A conductive bump assembly may include a passive substrate. The conductive bump assembly may also include a conductive bump pad supported by the passive substrate and surrounded by a first passivation layer opening. The conductive bump assembly may further include a second passivation layer opening on the passive substrate. The second passivation layer opening may be merged with the first passivation layer opening surrounding the conductive bump pad proximate an edge of the passive substrate. The conductive bump assembly may also include a conductive bump on the conductive bump pad.