SiC Chip Solder Joint Composition for Thermal Stress Reliability
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Solution Overview
Problem
The use of silicon carbide (SiC) substrates in semiconductor chips leads to potential cracking and damage due to high Young's modulus, which is three times higher than silicon (Si), necessitating improved joining members to maintain connection reliability and suppress deformation under thermal stress.
Innovation Solution
A semiconductor device with a double-sided heat dissipation structure using lead-free solder with an alloy composition of 3.2 to 3.8% Ag, 0.6 to 0.8% Cu, 0.01 to 0.2% Ni, x% Sb, y% Bi, 0.001 to 0.3% Co, 0.001 to 0.2% P, and a balance of Sn, where x+2y≤11 mass% and x+14y≤42 mass%, x≥5.1 mass%, to enhance creep resistance and maintain high connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If silicon carbide (SiC) substrates are used in semiconductor chips, then thermal conductivity and power handling capability are improved, but cracking and damage occur due to high Young's modulus being three times higher than silicon (Si)
Solution Approach 1:
The patent changes the material parameters of the joining member by specifying precise alloy composition ranges (Sn-3.2 to 3.8Ag-0.6 to 0.8Cu-0.01 to 0.2Ni-xSb-yBi-0.001 to 0.3Co-0.001 to 0.2P) to optimize the balance between creep resistance and deformation characteristics, allowing the joining member to accommodate the high Young's modulus of SiC without causing cracking
Solution Approach 2:
The patent uses a composite alloy material combining multiple elements (Sn, Ag, Cu, Ni, Sb, Bi, Co, P) to create a joining member with tailored properties that simultaneously provide adequate strength for SiC substrates and sufficient ductility to prevent cracking under thermal stress
2Reliability
If conventional joining members are used with SiC substrates, then connection is established, but deformation occurs under thermal stress reducing connection reliability
Solution Approach 1:
The patent optimizes the alloy composition parameters to achieve a specific balance: sufficient Ag (3.2 to 3.8 mass%) and Cu (0.6 to 0.8 mass%) for strength, controlled Sb (x mass%) and Bi (y mass%) for creep resistance with x+2y≤11 and x+14y≤42, and trace Co (0.001 to 0.3 mass%) and P (0.001 to 0.2 mass%) for microstructure control, resulting in a joining member that maintains shape stability under thermal stress while ensuring reliable connection
Solution Approach 2:
The patent employs a lead-free solder material that is optimized for single-use in high-reliability applications, where the joining member is designed to withstand the specific thermal stress conditions of SiC devices without requiring long-term reusability, achieving adequate performance through cost-effective alloy composition
3Reliability
If lead-free solder with optimized alloy composition is used, then creep resistance is enhanced and connection reliability is maintained, but manufacturing complexity increases due to precise composition control
Solution Approach 1:
The patent defines specific parameter ranges for alloy composition (Sn-3.2 to 3.8Ag-0.6 to 0.8Cu-0.01 to 0.2Ni-xSb-yBi-0.001 to 0.3Co-0.001 to 0.2P with x+2y≤11, x+14y≤42, x≥5.1) that balance performance requirements with manufacturability, where the ranges are narrow enough to ensure reliability but wide enough to allow standard manufacturing tolerances
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 lead-free solder composition effectively suppresses deformation and maintains high connection reliability, even under thermal stress, suitable for semiconductor devices with SiC substrates, enhancing the lifespan and performance of the semiconductor device.
Implementation Method 1
The lead-free solder having the above-described alloy composition has excellent creep resistance. Therefore, the lead-free solder having the above-described alloy composition is able to suppress the deformation of the semiconductor chip
Data Source
AI summary
A semiconductor device includes a semiconductor chip having first and second main electrodes disposed on opposite surfaces of a silicon carbide substrate, first and second heat dissipation members disposed so as to sandwich the semiconductor chip, and joining members disposed between the first main electrode and the first heat dissipation member and between the second main electrode and the second heat dissipation member. At least one of the joining members is made of a lead-free solder having an alloy composition that contains 3.2 to 3.8 mass % Ag, 0.6 to 0.8 mass % Cu, 0.01 to 0.2 mass % Ni, x mass % Sb, y mass % Bi, 0.001 to 0.3 mass % Co, 0.001 to 0.2 mass % P, and a balance of Sn, where x and y satisfy relational expressions of x+2y≤11 mass %, x+14y≤42 mass %, and x≥5.1 mass %.