Molding Package Cavity Layout for Low-Stress Power Modules
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Solution Overview
Problem
Current high-power semiconductor device modules face issues with mechanical stress and thermal performance due to excessive molding compound volume during sintering, leading to potential die cracks and reduced reliability, especially in applications like electric vehicles where thermal imbalances exacerbate stress.
Innovation Solution
Incorporating a gel-filled cavity within the molding package to reduce stress and warpage, combined with a direct-bonded metal structure for single-sided cooling and a clip design for mechanical and electrical connections, which also helps in dissipating heat and sensing environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large volume of molding compound is used to encapsulate the semiconductor die, then the die is well protected, but excessive mechanical stress is applied to the die during sintering which can cause die cracks
Solution Approach 1:
The molding compound is segmented into two distinct regions: a first molding compound surrounding the die and providing protection, and a second molding compound (gel material) filling the cavity and providing stress relief. This segmentation allows each region to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the molding package are assigned different material properties: the first molding compound has high mechanical strength for protection, while the second gel material has high elasticity and stress-absorbing properties. This local differentiation optimizes both die protection and stress management.
2Reliability
If a large volume of molding compound is used, then the die is well protected, but the warpage of the molding package increases during sintering
Solution Approach 1:
The molding package is divided into a rigid first molding compound for structural integrity and a flexible second gel material for warpage compensation, allowing the package to maintain shape stability during thermal processing.
Solution Approach 2:
The gel material's viscoelastic properties change with temperature, allowing it to accommodate thermal expansion and contraction during sintering, thereby reducing warpage while maintaining die protection.
3Reliability
If traditional molding compound is used, then the die is protected, but thermal performance is degraded due to poor heat dissipation
Solution Approach 1:
The gel material in the cavity region provides superior thermal management properties compared to traditional molding compound, while the first molding compound maintains its protective function. This localized optimization improves overall thermal performance without compromising die protection.
Solution Approach 2:
The molding package uses a composite structure combining traditional molding compound with gel material, leveraging the complementary properties of both materials to achieve both protection and enhanced thermal performance.
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 solution significantly reduces stress on semiconductor dies by over 60% and warpage by up to 45% during sintering, enhancing the reliability and thermal performance of high-power semiconductor device modules, making them more robust for automotive and hybrid electric vehicle applications.
Implementation Method 1
the gel material includes one or more of JCR6101 and HD-8820
Implementation Method 2
a direct-bonded metal (DBM) structure that provides single sided cooling for the power inverter circuit
Implementation Method 3
the sense pad configured to sense pressure applied to the molding package
Data Source
AI summary
A high-power semiconductor device module is implemented with a cavity in the molding package. The cavity reduces a volume of the molding compound, preventing an accumulation of stress in the module, and associated warpage of the package. Chip assemblies within the module are designed to fit within the cavity, so that semiconductor dies, and sensing devices therein are protected from damage during a sintering process in which the module is mounted to a heat sink. After the sintering process, the cavity can be sealed with a gel material. The molding package described herein can also enhance reliability of the module during operation, ensuring that the product is robust for electric and hybrid electric vehicle applications.