Die Edge Contacts for Thermal Stress Mitigation
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Solution Overview
Problem
Conventional semiconductor devices face issues with thermal expansion mismatch between different substrates, leading to stress and delamination problems in solder joints due to varying coefficients of thermal expansion, which can cause cracking and other reliability issues.
Innovation Solution
The implementation of die edge contacts formed by a conductive trench extending from a contact to the die edge, with the option of a through-substrate via, allows for a larger contact area and improved attachment to a packaging substrate, reducing stress and enhancing structural integrity by accommodating thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder bumps are used to provide electrical connection between die and substrate, then electrical connectivity is achieved, but thermal expansion mismatch causes stress and cracking in the joint region
Solution Approach 1:
The patent transitions from point-contact solder bumps to edge-contact connections that extend along the die edge. This dimensional change from 0D point contacts to 1D linear contacts distributes the thermal stress along a longer path, reducing stress concentration at any single point and improving joint reliability under thermal cycling conditions.
Solution Approach 2:
The invention changes the contact geometry parameters by extending the contact area from small solder bumps to elongated edge contacts. This parameter change increases the contact length and distributes the thermal expansion mismatch stress over a larger area, reducing the stress magnitude and preventing cracking.
2Reliability
If conventional point-contact solder bumps are used, then electrical connection is established, but the contact area is limited leading to high stress concentration
Solution Approach 1:
The patent extends the contact from point-like solder bumps to linear edge contacts along the die perimeter. This dimensional transformation increases the contact area from a small circular footprint to an elongated linear feature, distributing stress and improving electrical connection reliability.
Solution Approach 2:
The edge contact structure can be viewed as segmented along the die edge, with multiple contact points or zones distributed along the length. This segmentation allows the total contact area to be distributed across multiple locations, reducing stress concentration at any single point while maintaining overall electrical connectivity.
3Adaptability or versatility
If different substrates with different CTE are used, then device functionality is achieved, but thermal cycling causes expansion/contraction mismatch leading to delamination
Solution Approach 1:
The invention changes the contact geometry parameter from small solder bumps to extended edge contacts. This parameter change increases the contact length and distributes the thermal expansion mismatch stress over a larger area, reducing the stress magnitude and preventing delamination during thermal cycling while maintaining compatibility with different substrates.
Solution Approach 2:
The patent addresses thermal expansion mismatch by designing edge contacts that can accommodate the differential expansion between substrates. The extended contact length allows for gradual stress distribution and deformation, accommodating the thermal expansion differences without causing catastrophic failure or delamination.
Data Source
AI summary
A semiconductor device utilizing die edge contacts is provided. An integrated circuit die has a post-passivation layer with a trench filled with a conductive material extending from a contact to a die edge, thereby forming a die edge contact. Optionally, a through substrate via may be positioned along the die edge such that the conductive material in the trench is electrically coupled to the through-substrate via, thereby forming a larger die edge contact. The integrated circuit die may be placed in a multi-die package wherein the multi-die package includes walls having a major surface perpendicular to a major surface of the integrated circuit die. The die edge contacts are electrically coupled to contacts on the walls of the multi-die package. The multi-die package may include edge contacts for connecting to another substrate, such as a printed circuit board, a packaging substrate, a high-density interconnect, or the like.