Semiconductor Package Pad Layout for UBM Corner Crack Prevention
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Solution Overview
Problem
The challenge in semiconductor packaging lies in managing tensile stress at the corners of under bump metallurgy structures, which can lead to cracking of insulating layers, particularly in 3D packaging where coefficient of thermal expansion differences cause stress concentration, affecting the reliability and performance of the package structure.
Innovation Solution
Incorporating a conductive pad that entirely covers the corner of the under bump metallurgy structure contacting the insulating layer, thereby mitigating the concentrated tensile stress and reducing the risk of cracking, using a package structure design that includes a conductive pad, under bump metallurgy structure, and conductive via for stress relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a smaller package structure is used to increase density, then production efficiency improves and costs decrease, but tensile stress concentration at corners increases leading to insulating layer cracking
Solution Approach 1:
The conductive pad is designed to specifically cover the corner regions of the under bump metallurgy structure where tensile stress concentrates during thermal cycling. This localized reinforcement at stress-prone areas provides targeted protection without requiring a complete redesign of the entire package structure, thus maintaining production efficiency while improving reliability.
Solution Approach 2:
The conductive pad acts as a pre-positioned stress-distributing element that mitigates tensile stress concentration before it can cause insulating layer cracking. By having this protective structure in place before thermal cycling occurs, the design prevents damage rather than addressing it after failure.
2Reliability
If the conductive pad entirely covers the corner of the under bump metallurgy structure, then tensile stress concentration is reduced and cracking risk decreases, but device complexity increases
Solution Approach 1:
The conductive pad serves multiple functions simultaneously: it provides electrical connection, acts as a stress-distributing element to prevent cracking, and serves as a structural component of the package. By combining these functions into a single element, the design improves reliability without proportionally increasing complexity.
Solution Approach 2:
The conductive pad is designed to perform multiple roles: electrical conduction, mechanical stress distribution, and structural support. This multi-functionality allows a single component to address multiple requirements, reducing the need for additional separate elements and thereby limiting the increase in device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces the risk of insulating layer cracking, enhancing the performance and reliability of the package structure by distributing stress more evenly, thus improving manufacturing yield and reducing costs.
Implementation Method 1
The conductive pad entirely covers the corner of the under bump metallurgy structure contacting the insulating layer, thereby reducing or mitigating a tensile stress concentrated at the corner
Data Source
AI summary
A package structure is provided. The package structure includes a first conductive pad in an insulating layer, a first under bump metallurgy structure under the first insulating layer, and a first conductive via in the insulating layer. The first conductive via is vertically connected to the first conductive pad and the first under bump metallurgy structure. In a plan view, a first area of the first under bump metallurgy structure is confined within a second area of the first conductive pad.