Spring Coil Interconnects for CTE-Mismatch in Stacked IC Packages
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Solution Overview
Problem
Integrated circuits face joint stress and warpage due to mismatch in the coefficient of thermal expansion (CTE) between stacked substrates, which can lead to structural issues during packaging.
Innovation Solution
The use of spring coils, such as microsprings, to join devices, providing a solid physical and electrical connection while absorbing horizontal and vertical stresses caused by CTE mismatch and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid connectors are used to join stacked substrates, then electrical connectivity is achieved, but joint stress and warpage occur due to CTE mismatch
Solution Approach 1:
The patent employs flexible spring connectors instead of rigid connectors to join stacked substrates. These spring connectors can deform elastically to accommodate differential thermal expansion between substrates with mismatched CTE values, thereby maintaining electrical connectivity while absorbing joint stress and preventing warpage.
Solution Approach 2:
The patent changes the mechanical properties of the connector from rigid to flexible by using spring elements. This parameter change allows the connector to dynamically adjust its stiffness, providing both electrical connectivity and stress absorption capabilities to resolve the contradiction between reliable connection and stress prevention.
2Stress or pressure
If spring coils are used to join devices, then stress absorption is improved, but device complexity increases
Solution Approach 1:
The patent uses dynamic spring connectors that can change their mechanical state based on applied stress. These spring elements provide stress absorption through elastic deformation, allowing the connector structure to adapt to thermal expansion differences without requiring complex active control mechanisms, thus balancing stress absorption with acceptable 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
The spring coils effectively relieve stress and maintain structural integrity, ensuring reliable electrical connectivity and reducing the risk of damage from thermal expansion mismatch.
Implementation Method 1
spring coils, such as microsprings, to join devices, providing a solid physical and electrical connection while absorbing horizontal and vertical stresses caused by CTE mismatch and warpage
Implementation Method 2
reflowing the solder paste to electrically and physically couple the spring connectors of the second package component to the first contact pads of the first package component
Data Source
AI summary
A method includes depositing solder paste over first contact pads of a first package component. Spring connectors of a second package component are aligned to the solder paste. The solder paste is reflowed to electrically and physically couple the spring connectors of the second package component to the first contact pads of the first package component. A device includes a first package component and a second package component electrically and physically coupled to the first package component by way of a plurality of spring coils. Each of the plurality of spring coils extends from the first package component to the second package component.