Semiconductor Package UBM Via Structure for Reliable Bump Connection
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Solution Overview
Problem
The reliability of connections between semiconductor packages and substrates is affected by the connectivity of connection bumps and redistribution layers, necessitating an enhancement in board level reliability through an under-bump metal (UBM) structure.
Innovation Solution
A semiconductor package design incorporating a redistribution structure with an insulating layer, a redistribution layer, and an under-bump metal (UBM) structure featuring a pad protruding from the first surface and a via penetrating through the insulating layer to connect the redistribution layer and the UBM pad, with a second pad having a larger width than the first pad and a via with a step configuration to enhance connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UBM structure is formed between the redistribution layer and the connection bump to enhance board level reliability, then connection reliability is improved, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The UBM structure employs a nested configuration where the UBM pad is positioned within the via opening, the via penetrates through the insulating layer, and the connection bump is disposed on the UBM pad. This nested arrangement integrates multiple functional elements (electrical connection, mechanical support, and bonding interface) into a compact vertical stack, improving connection reliability while managing structural complexity through efficient spatial organization.
Solution Approach 2:
The via structure transitions from a simple planar connection to a three-dimensional vertical penetration through the insulating layer. The via opening has a defined area in the planar dimension, while the via itself extends in the vertical dimension to connect the UBM pad to the redistribution layer. This dimensional transition enables reliable electrical connection through the insulating barrier while maintaining a compact overall structure.
2Reliability
If the via penetrates through the insulating layer to connect the redistribution layer and the UBM pad, then electrical connectivity is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The via opening is formed in the insulating layer at a predetermined location before the UBM pad is formed. This preliminary positioning ensures that the via opening is pre-aligned with the intended connection path between the redistribution layer and the UBM pad. The UBM pad is then formed within this pre-positioned opening, guaranteeing proper alignment and electrical connectivity while reducing the precision requirements for subsequent manufacturing steps.
Solution Approach 2:
The via opening in the insulating layer serves as an intermediary structure that facilitates the electrical connection between the redistribution layer and the UBM pad. By providing a pre-formed conductive pathway through the insulating barrier, the via opening mediates the connection process and reduces the alignment precision requirements for the UBM pad and connection bump formation steps.
3Reliability
If the second pad has a larger width than the first pad to enhance connection reliability, then the bonding area is increased, but the device footprint increases
Solution Approach 1:
The UBM structure employs different pad widths at different locations to optimize local functions. The first pad (redistribution pad) has a width matched to the redistribution layer trace, while the second pad (UBM pad) has a larger width to provide adequate bonding area for the connection bump. This local differentiation ensures reliable electrical connection and mechanical bonding where needed, while maintaining compact dimensions in other areas of the device.
Data Source
AI summary
A semiconductor package includes a redistribution structure including an insulating layer and a redistribution layer on the insulating layer, and having a first surface and a second surface opposing the first surface, and an under-bump metal (UBM) structure including an UBM pad protruding from the first surface of the redistribution structure, and an UBM via penetrating through the insulating layer and connecting the redistribution layer and the UBM pad. A lower surface of the UBM via has a first area in contact with the UBM pad, and a second area having a step configuration relative to the first area and that extends outwardly of the first area.