Variable Interconnect Geometry for Thermal Expansion Management
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Solution Overview
Problem
Conventional electronic packages face challenges in achieving optimal electrical performance while maintaining mechanical reliability due to uniform interconnect geometry, which fails to accommodate differential thermal expansion, leading to potential cracking or delamination of low-K dielectric materials in high-performance microprocessors.
Innovation Solution
Implementing a variable interconnect geometry that varies in compliance from the center to the edge of the die, using a combination of columnar and helix interconnect designs, allowing for tailored mechanical and electrical performance through sequential lithography and electroplating processes, ensuring high compliance at the edge to accommodate thermal expansion without compromising the low-K dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform interconnect geometry is used, then manufacturing simplicity is maintained, but mechanical reliability deteriorates due to inability to accommodate differential thermal expansion
Solution Approach 1:
The patent applies local quality by varying the interconnect geometry (from columnar at center to helix at edges) to provide different compliance characteristics in different locations. This allows each region to be optimized for its specific thermal expansion conditions while maintaining a single fabrication process.
Solution Approach 2:
The interconnect array is segmented into different geometric types (columnar and helix structures) based on location, allowing differential compliance characteristics to be introduced without requiring separate fabrication processes for each region.
2Power
If low-K dielectric material is used, then power density is increased, but mechanical reliability deteriorates due to cracking and delamination from thermo-mechanical stresses
Solution Approach 1:
The variable geometry interconnects act as an intermediary compliant structure between the low-K dielectric and the substrate, absorbing thermo-mechanical stresses and preventing them from being transmitted to the dielectric material, thus preventing cracking and delamination.
Solution Approach 2:
The patent changes the mechanical parameters (compliance, geometry) of the interconnect structure to match the thermal expansion characteristics of the low-K dielectric, reducing stress transmission and maintaining dielectric integrity under high power density conditions.
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 approach enhances electrical performance and extends the fatigue life of interconnects while preventing cracking or delamination of low-K dielectric materials, maintaining mechanical reliability and supporting increased power density and performance in microprocessors.
Implementation Method 1
the differential expansion due to coefficient of thermal expansion (CTE) mismatch (between chip and board or chip and interposer/substrate or package and board) increases
Implementation Method 2
using a compliant structure as an off-chip interconnect allows for isolation of the die from the substrate
Implementation Method 3
tailored mechanical and electrical performance through sequential lithography and electroplating processes
Data Source
AI summary
Disclosed is a variable interconnect geometry formed on a substrate that allows for increased electrical performance of the interconnects without compromising mechanical reliability. The compliance of the interconnects varies from the center of the substrate to edges of the substrate. The variation in compliance can either be step-wise or continuous. Exemplary low-compliance interconnects include columnar interconnects and exemplary high-compliance interconnects include helix interconnects. A cost-effective implementation using batch fabrication of the interconnects at a wafer level through sequential lithography and electroplating processes may be employed.