Segmented Conductive Elements Prevent Solder Bridging
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Solution Overview
Problem
Conventional flip-chip packages experience solder bridging issues due to decreasing distances between copper pillar bumps, leading to increased fabrication costs and stress between copper pillars and the UBM layer, which reduces contact area and increases the risk of cracking.
Innovation Solution
A semiconductor device and structure with conductive elements featuring a first conductive portion and a second conductive portion sequentially formed on the UBM layer, where the second conductive portion is narrower and shorter than the first, reducing the distance between adjacent conductive elements and eliminating the need for an insulating layer, thereby preventing solder bridging and reducing fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the distance between copper pillar bumps is decreased to increase I/O counts, then the integration density is improved, but solder bridging easily occurs between the bumps
Solution Approach 1:
The conductive element is segmented into two distinct parts: a first conductive portion (wider base) and a second conductive portion (narrower top). This segmentation allows the structure to simultaneously provide mechanical stability through the wider base and sufficient spacing for solder balls through the narrower top portion, resolving the contradiction between high I/O density and solder bridging prevention.
Solution Approach 2:
Different parts of the conductive element have different local qualities: the first conductive portion has a larger width for stability and stress distribution, while the second conductive portion has a smaller width for preventing solder bridging. This local differentiation allows each part to optimize its function for the specific requirements at that location.
2Reliability
If the width of copper pillars is reduced to prevent solder bridging, then solder bridging is alleviated, but the contact area between copper pillars and UBM layer is reduced, increasing stresses
Solution Approach 1:
The conductive element is divided into two segments with different widths: the first conductive portion maintains a larger width to ensure sufficient contact area with the UBM layer for stress distribution, while the second conductive portion has a reduced width to prevent solder bridging. This segmentation resolves the contradiction between preventing solder bridging and maintaining structural strength.
Solution Approach 2:
The structure applies local quality by having the first conductive portion (at the UBM interface) be wider for strength, while the second conductive portion (exposed to solder) be narrower for bridging prevention. Each local region is optimized for its specific functional requirement.
3Strength
If an insulating layer is added to reduce stresses, then stress management is improved, but the fabrication cost is increased
Solution Approach 1:
The insulating layer is extracted/removed from the structure. Instead of adding an insulating layer to manage stress, the invention uses the segmented conductive element structure itself to provide both stress distribution (through the wider first portion) and solder bridging prevention (through the narrower second portion), eliminating the need for additional insulating layers and reducing fabrication cost.
Solution Approach 2:
The segmented conductive element serves multiple functions simultaneously: the first conductive portion provides mechanical stability and stress distribution, while the second conductive portion provides solder bridging prevention. This multi-functionality replaces what would otherwise require separate components (conductive element plus insulating layer), reducing complexity and cost.
Data Source
AI summary
A semiconductor device is disclosed, which includes: a substrate having a plurality of connecting pads; a semiconductor component having a plurality of bonding pads formed on a surface thereof and corresponding to the connecting pads and a UBM layer formed on the bonding pads; a plurality of conductive elements each having a first conductive portion and a second conductive portion sequentially formed on the UBM layer, wherein the second conductive portion is less in width than the first conductive portion; and a plurality of solder balls formed between the second conductive portions and the connecting pads for connecting the semiconductor component and the substrate, thereby preventing solder bridging from occurring between the adjacent conductive elements and reducing stresses between the conductive elements and the UBM layer.