Off-Center Semiconductor Electrode Design for Thermal Strain Reduction
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Solution Overview
Problem
High-temperature semiconductor modules experience significant thermal strain at the bonding section due to differences in linear expansion coefficients, leading to potential breakage and inadequate cooling efficiency, as existing solutions like double-sided cooling structures and plate-shaped conductor members do not effectively mitigate strain at high temperatures.
Innovation Solution
A semiconductor module design featuring a first wiring layer, a semiconductor element bonded with a first bonding layer, a first electrode bonded with a second bonding layer, and a second electrode connected to the first electrode, where the second electrode is positioned off-center and has a wider width than the first electrode's thickness, along with a second wiring layer, to reduce thermal strain through improved heat dissipation and structural alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a double-sided cooling structure is used to improve cooling efficiency, then cooling performance is enhanced, but thermal strain in the bonding section increases due to high rigidity at the center position
Solution Approach 1:
The heat sink is designed with different local properties: a first heat dissipation section with higher rigidity at the center position for effective cooling, and a second heat dissipation section with lower rigidity at the peripheral position to reduce thermal strain. This local differentiation allows the structure to simultaneously achieve good cooling performance and reduced thermal stress in the bonding section.
2Strength
If a plate-shaped conductor member is provided for connection with the heat sink, then structural connection is achieved, but heat dissipation property is low and cooling performance is poor due to narrow heat dissipation path
Solution Approach 1:
The heat sink transitions from a narrow plate-shaped conductor to a three-dimensional structure with extended heat dissipation sections. This dimensional change creates multiple heat dissipation paths and increases the surface area for heat transfer, thereby improving heat dissipation property while maintaining structural connection strength.
3Reliability
If high melting point solder with lead content is used for bonding at high temperatures, then bonding durability is improved, but the material is excluded from RoHS and future compliance is uncertain
Solution Approach 1:
The bonding material is changed from lead-based high melting point solder to lead-free sintered metal material. This parameter change in material composition maintains the necessary high temperature resistance and bonding durability while achieving RoHS compliance, allowing the device to operate at 200°C or higher without violating environmental regulations.
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 effectively reduces thermal strain in the bonding section between semiconductor chips and conductor members, enhancing cooling performance and module reliability without requiring complex processes, as demonstrated by finite element analysis and temperature comparisons.
Implementation Method 1
Sintered metal materials obtained by sintering nano-metal particles or micrometer-order metal particles are expected as these alternative materials, and development with regard to bonding with sintered silver or sintered copper is advanced
Implementation Method 2
a thermal strain caused by a difference in coefficients of linear expansion between members concentrates mainly on a bonding section of the power device and breaks the bonding section
Data Source
AI summary
Provided is a semiconductor module enabling to effectively reduce, with a relatively simple structure, a thermal strain occurring in a bonding section between a semiconductor chip and other conductor members. The semiconductor module is characterized by being provided with: a first wiring layer; a semiconductor element bonded on the first wiring layer via a first bonding layer; a first electrode bonded on the semiconductor element via a second bonding layer; a second electrode connected on the first electrode; and a second wiring layer connected on the second electrode. The semiconductor module is also characterized in that: the width of the second electrode, said width being in the short-side direction, is more than the thickness of the first electrode; and the second electrode is disposed at a position off the center position of the semiconductor element.