Ceramic-Framed Package Sealing for Heat Sink Expansion Mismatch
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Solution Overview
Problem
Existing semiconductor package designs face reliability issues with the junction between the heat sink and the lid due to high thermal expansion coefficients, leading to adhesive layer cracking and compromised hermeticity, especially when the heat sink has a coefficient of thermal expansion of 9 ppm/°C or more, which also limits thermal conductivity.
Innovation Solution
A package design featuring a heat sink with a coefficient of thermal expansion between 9 ppm/°C and 15 ppm/°C, combined with a ceramic frame and lid, where the frame and lid edges have chamfers to reduce stress concentration on the adhesive layer, ensuring reliable sealing and high thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the heat sink has a high coefficient of thermal expansion (9 ppm/°C or more) to achieve high thermal conductivity, then heat dissipation is improved, but the adhesive layer cracks during heating cycles leading to loss of hermeticity
Solution Approach 1:
The patent optimizes the coefficient of thermal expansion of the heat sink to be within 9-15 ppm/°C, balancing thermal conductivity requirements with mechanical compatibility to the ceramic frame and lid, preventing adhesive layer cracking while maintaining effective heat dissipation
Solution Approach 2:
The patent employs a composite structure consisting of a heat sink, ceramic frame, and ceramic lid with controlled thermal expansion properties, creating a multi-material system that reconciles the conflicting requirements of high thermal conductivity and low thermal expansion
2Strength
If the heat sink has a coefficient of thermal expansion of 9 ppm/°C or more, then thermal conductivity is improved, but stress concentration on the adhesive layer increases causing cracks
Solution Approach 1:
The patent precisely controls the coefficient of thermal expansion parameter of the heat sink within the range of 9-15 ppm/°C, optimizing the balance between thermal conductivity and stress generation to prevent adhesive layer failure
Solution Approach 2:
The patent uses materials with matched thermal expansion coefficients (heat sink, ceramic frame, and ceramic lid) to create a homogeneous thermal expansion behavior across the junction, minimizing differential stress and preventing adhesive layer cracking
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 design effectively reduces stress on the adhesive layer, preventing cracking and maintaining hermeticity while achieving higher heat dissipation, even with a heat sink having a high thermal expansion coefficient, thus enhancing the reliability of the junction and thermal performance.
Implementation Method 1
the heat sink having a coefficient of thermal expansion of 9 ppm/° C. or more and 15 ppm/° C. or less from 25° C. to 100° C.
Implementation Method 2
the heat sink having a coefficient of thermal expansion of 9 ppm/° C. or more and 15 ppm/° C. or less from 25° C. to 100° C.
Data Source
AI summary
A package has a cavity to be sealed by a lid. The package includes a heat sink having a coefficient of thermal expansion of 9 ppm/° C. or more and 15 ppm/° C. or less from 25° C. to 100° C. and a frame disposed on the heat sink, made of ceramics, and surrounding the cavity in plan view. An outer edge of the frame includes a first linear portion extending along a first direction, a second linear portion extending along a second direction orthogonal to the first direction, and a chamfer connecting the first linear portion and the second linear portion in plan view.