High Temperature Interconnect Assembly Using Transition Pads
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Solution Overview
Problem
High temperature electronic chip packaging faces limitations due to bond degradation and failure at interfaces of incompatible metals, such as gold-aluminum, which become impractical above 200°C, leading to impracticality in environments exceeding 225°C.
Innovation Solution
A high temperature interconnect assembly using first-metal to first-metal and second-metal interconnects, facilitated by a transition pad that is compatible with both, eliminating incompatible metal interfaces, with exemplary embodiments featuring platinum-based or silicon-on-insulator transition pads to maintain electrical communication without interface degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If incompatible metals (e.g., gold-aluminum) are used to interconnect chip and package, then electrical communication is achieved, but bond degradation and failure occur at temperatures above 200°C
Solution Approach 1:
A transition pad made of compatible metal (e.g., platinum or nickel) is introduced as an intermediary between the aluminum chip pad and the gold package contact. This transition pad serves as a mediator that eliminates the direct incompatible metal interface, allowing the system to operate reliably at temperatures above 200°C by preventing the formation of degraded intermetallic compounds between aluminum and gold.
Solution Approach 2:
The original single-interface interconnect structure (aluminum directly to gold) is segmented into two separate interfaces: aluminum-to-transition-pad and transition-pad-to-gold. Each interface uses compatible metal pairs that form stable intermetallic compounds, thereby dividing the problematic single interface into two reliable interfaces that can withstand high temperatures.
2Temperature
If alternative metallurgical interconnection schemes (e.g., aluminum wire to gold plated glass) are used, then temperature resistance is improved, but Kirkendall voids and intermetallic formation still cause failure above 200°C
Solution Approach 1:
The transition pad acts as a mediator that eliminates the direct aluminum-to-gold interface responsible for Kirkendall void formation. By introducing a compatible metal layer (platinum or nickel) between aluminum and gold, the system prevents the diffusion mismatch that causes Kirkendall voids, thereby maintaining interconnection stability at elevated temperatures.
Solution Approach 2:
The invention changes the material parameters of the interconnect interface by replacing incompatible metal pairs (aluminum-gold) with compatible metal pairs (aluminum-platinum/nickel and platinum/nickel-gold). This parameter change in material compatibility prevents intermetallic formation and Kirkendall voids, enabling stable operation above 200°C.
3Reliability
If separate aluminum-to-aluminum and gold-to-gold interfaces are used, then excellent performance above 250°C is achieved, but incompatible metal interfaces must be eliminated
Solution Approach 1:
The transition pad serves as a mediator that enables separate aluminum-to-aluminum and gold-to-gold interfaces to coexist in a single interconnect structure. By introducing this intermediate layer, the system achieves the reliability of homogeneous metal interfaces (aluminum-to-aluminum and gold-to-gold) while maintaining a practical three-layer structure (aluminum-chip-to-transition-pad-to-gold-package) that is manufacturable and structurally sound.
Data Source
AI summary
An interconnect assembly that operates in environments well exceeding 200° C. without degradation and/or failure. The interconnect assembly of the present invention eliminates the incompatible metal interfaces of the prior art and relies on aluminum first-metal wire to electrically connect to first-metal pads on a chip and a second-metal wire to electrically connect to second-metal plated contacts on a package. Both wire types are then electrically connected together utilizing a high temperature transition pad disposed between the chip and contacts on the package, therefore eliminating incompatible metal interfaces of the prior art.