Etched Micro-Spring Spacers for Low-Stress Chip Interconnects
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Solution Overview
Problem
Conventional flip-chip mounting methods face challenges such as stiffness in connections, mechanical stress due to thermal expansion mismatches, and difficulties in easy replacement or manual installation, especially when interfacing ICs with varying surface flatness and thermal expansion rates.
Innovation Solution
The development of micro-springs with intrinsic stress profiles on substrates, where elastic members are etched and spacers are co-fabricated to form out-of-plane structures that can compress against chip contact pads, allowing for flexible connections and improved assembly compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flip-chip mounting methods are used, then electrical connections are established, but the connections become stiff and generate mechanical stress due to thermal expansion mismatches
Solution Approach 1:
The patent applies the dynamics principle by transforming rigid, static connections into flexible, dynamic ones through the introduction of micro-springs. These springs can compress and expand, allowing the connection to adapt to thermal expansion mismatches and surface flatness variations, thereby reducing mechanical stress while maintaining reliable electrical connections
Solution Approach 2:
The patent employs flexible thin films in the form of micro-springs as elastic members that provide mechanical compliance. These flexible structures absorb thermal stress and accommodate surface variations, solving the contradiction between connection reliability and mechanical stress reduction
2Productivity
If conventional mounting methods are used, then chips are assembled, but replacement and manual installation become difficult
Solution Approach 1:
The dynamic flexibility of micro-springs enables both efficient automated assembly and easy manual replacement. During assembly, springs compress to make contact; during replacement, the flexible nature allows for gentle disconnection without damage, improving both productivity and ease of repair
3Stability of the object's composition
If rigid connections are used, then structural stability is achieved, but adaptability to varying surface flatness and thermal expansion rates is reduced
Solution Approach 1:
The patent resolves this contradiction by using dynamic micro-spring structures that maintain stable electrical connections while adapting to surface variations and thermal expansion. The springs provide both structural stability through consistent contact force and adaptability through their ability to deform elastically
Solution Approach 2:
The patent applies parameter changes by utilizing the elastic properties of micro-springs to dynamically adjust contact pressure and position. This allows the system to maintain stable connections while adapting to varying surface flatness and thermal expansion rates through controlled deformation of the spring structures
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 enables compact, adaptable, and forgiving multi-chip module assemblies with reduced mechanical stress, facilitating easier assembly and rework while maintaining reliable electrical connections.
Implementation Method 1
The elastic metal has an intrinsic stress profile... The intrinsic stress profile in the elastic member biases the free end of the elastic member away from the substrate to form an out of plane structure
Data Source
AI summary
An electronic assembly and methods of making the assembly are disclosed. The electronic assembly includes a substrate with an elastic member having an intrinsic stress profile. The elastic member has an anchor portion on the surface of the substrate; and a free end biased away from the substrate via the intrinsic stress profile to form an out of plane structure. The substrate includes one or more spacers on the substrate. The electronic assembly includes a chip comprising contact pads. The out of plane structure on the substrate touches corresponding contact pads on the chip, and the spacers on the substrate touch the chip forming a gap between the substrate and the chip.