Semiconductor Package Thermal Interface Material Design for Warpage Reduction
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Solution Overview
Problem
Integrated semiconductor packages face reliability issues due to warpage caused by differences in coefficients of thermal expansion, leading to delamination and cracks during manufacturing and use.
Innovation Solution
A semiconductor package design incorporating a package substrate with first and second semiconductor chips separated by a gap, where a first thermal interface material layer with a lower modulus of elasticity is placed between them, and second thermal interface material layers with a higher modulus of elasticity are applied on each chip, along with a heat spreader for improved heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If semiconductor chips are integrated in an integrated semiconductor package, then multi-function and high-capacity are achieved, but warpage occurs due to various coefficients of thermal expansion leading to delamination and cracks
Solution Approach 1:
The patent applies different modulus of elasticity values to different regions of the thermal interface material structure. The first thermal interface material layer (filling the gap between chips) has a lower modulus of elasticity to absorb stress, while the second thermal interface material layer (on chip surfaces) has a higher modulus of elasticity for effective thermal conduction. This local differentiation allows the structure to simultaneously accommodate thermal expansion differences and maintain thermal performance.
Solution Approach 2:
The patent uses a composite thermal interface material structure consisting of two distinct material layers with different properties. The first layer uses a softer material (lower modulus) for stress absorption, while the second layer uses a harder material (higher modulus) for thermal conduction. This composite approach allows the system to benefit from both stress accommodation and effective heat transfer, resolving the contradiction between integration versatility and package reliability.
2Reliability
If thermal interface material is used to fill gaps between semiconductor chips, then stress is reduced and delamination is prevented, but thermal conductivity may be compromised
Solution Approach 1:
The patent optimizes thermal interface material properties for different functional requirements at different locations. The first layer (gap-filling) prioritizes stress absorption with lower modulus, while the second layer (chip-contact) prioritizes thermal conduction with higher modulus. This local optimization ensures that each region performs its primary function effectively without compromising overall system performance.
Solution Approach 2:
The patent employs a composite thermal interface structure where two materials with different modulus of elasticity values work together. The softer first layer provides stress relief and prevents delamination, while the harder second layer ensures efficient thermal conduction from the chip surfaces. This composite design resolves the trade-off between reliability enhancement through stress reduction and maintenance of thermal conductivity.
3Temperature
If a rigid thermal interface material is used for better thermal conduction, then heat dissipation is improved, but stress from thermal expansion differences causes delamination and cracks
Solution Approach 1:
The patent strategically places materials with different mechanical properties in different locations within the thermal interface structure. The rigid second layer contacts the chips for effective heat conduction, while the compliant first layer fills the gap to absorb thermal expansion stress. This spatial differentiation of material properties allows simultaneous achievement of good thermal conduction and stress management.
Solution Approach 2:
The patent creates a composite thermal interface system combining rigid and compliant materials. The rigid second layer (higher modulus) provides the necessary thermal conduction pathway, while the compliant first layer (lower modulus) acts as a stress buffer against thermal expansion mismatches. This composite material approach resolves the contradiction between heat dissipation efficiency and package reliability by allowing each material to perform its specialized function.
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 design enhances package reliability by reducing stress and facilitating heat dissipation, preventing delamination and cracking, while maintaining effective thermal conductivity.
Implementation Method 1
a first thermal interface material layer formed in the gap and having a first modulus of elasticity; and a second thermal interface material layer formed on each of the first semiconductor chip and the second semiconductor chip and having a second modulus of elasticity, wherein the first modulus of elasticity is less than the second modulus of elasticity
Implementation Method 2
a heat spreader supported on the package substrate and contacting all of the first thermal interface material layer and the second thermal interface material layer formed on each of the first semiconductor chip and the second semiconductor chip
Data Source
AI summary
A semiconductor package includes a first semiconductor chip mounted on the package substrate, a second semiconductor mounted on the package substrate and set apart from the first semiconductor chip in a horizontal direction thereby forming a gap between the first semiconductor chip and the second semiconductor chip. The semiconductor package further includes a first thermal interface material layer formed in the gap and having a first modulus of elasticity and a second thermal interface material layer formed on each of the first semiconductor chip and the second semiconductor chip and having a second modulus of elasticity, wherein the first modulus of elasticity is less than the second modulus of elasticity.