Stress Relieved Thermal Base for IC Packaging
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Solution Overview
Problem
Integrated circuit packaging faces challenges due to differing coefficients of thermal expansion (CTE) among materials, leading to mechanical stress and potential package failure, while maintaining electrical performance and environmental ruggedness.
Innovation Solution
A thermal base with a thermally conductive body featuring a rib, recess, and pedestal, integrated with a leadframe assembly, where the pedestal height positions the integrated circuit chip bonding pad coplanar with the leads, reducing mechanical stress and improving electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different materials are used for package components to perform different functions, then functional performance is improved, but mechanical stress increases due to different coefficients of thermal expansion
Solution Approach 1:
The thermal base incorporates a stress relief layer with specific local properties (different CTE characteristics) at the interface between the leadframe and the base body. This layer is positioned specifically where stress concentration occurs, allowing different materials to be used for functional purposes while the localized stress relief layer mitigates the thermal expansion mismatch stress.
2Reliability
If the bonding pad is positioned at a height coplanar with the leads, then electrical characteristics are improved, but additional manufacturing complexity is introduced
Solution Approach 1:
The pedestal structure is pre-formed as an integral part of the thermal base during base manufacturing, rather than being added as a separate post-processing step. This preliminary formation of the height-adjustment feature allows the bonding pad to be positioned at the correct coplanar height during subsequent assembly operations, improving electrical characteristics without significantly increasing overall manufacturing 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
This configuration reduces bonding wire length, enhances frequency response, impedance matching, and increases adhesion between components, while providing enhanced environmental protection and reduced moisture sensitivity.
Implementation Method 1
a body of thermally conductive material
Data Source
AI summary
A package is formed by a thermal base and a leadframe assembly. The thermal base includes a body of thermally conductive material having a top surface, wherein the top surface of the body includes a pedestal. An integrated circuit chip is mounted to the pedestal, the integrated circuit chip including bonding pads. The leadframe assembly includes leads and an encapsulant ring that partially embeds the leads. The leadframe assembly is mounted to the top surface of said body surrounding the pedestal. The pedestal is configured with a thickness that positions the bonding pad at a height substantially coplanar with the leads. Bonding wires extend from the bonding pads to the leads with a shortened length so as to provide for improved electrical characteristics of frequency response, impedance and inductance.