Semiconductor Module Solder Composition for Ni Diffusion Suppression
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Solution Overview
Problem
Conventional power semiconductor modules face reliability issues during high-temperature operation due to thermal stress and size constraints, leading to challenges in maintaining long-term reliability and preventing void formation and Ni diffusion in solder joints.
Innovation Solution
A semiconductor module with a solder composition of Sn-(6-8.5)Sb-(2-4.5)Ag-(1.25-2.0)Cu is used, where Cu diffuses to form a protective SnCu alloy at the Ni interface, preventing Ni diffusion and ensuring wettability, thus maintaining the Ni residual film and preventing voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solder composition is used, then manufacturing cost is reduced, but Ni diffusion and void formation occur leading to poor reliability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of multiple alloying elements (Sb: 5-10 mass%, Ag: 2-5 mass%, Cu: 1-3 mass%, Ni: 0.01-1 mass%) in the solder. This multi-parameter optimization prevents Ni diffusion and void formation while maintaining manufacturing feasibility, resolving the contradiction between reliability improvement and harmful factor suppression.
Solution Approach 2:
The patent uses a composite solder material containing multiple alloying elements (Sn-Sb-Ag-Cu-Ni system) rather than pure tin or simple alloys. This composite composition creates synergistic effects where each element contributes specific functions: Sb and Ag prevent Ni diffusion, Cu enhances strength, and Ni improves wettability. The composite material approach simultaneously addresses reliability and harmful factor prevention.
2Volume of moving object
If module size is reduced for automotive applications, then installation space is saved, but thermal stress increases leading to reliability issues
Solution Approach 1:
The patent applies parameter changes by optimizing the solder's thermal and mechanical properties through controlled alloying element concentrations. The specific composition range (Sb: 5-10 mass%, Ag: 2-5 mass%, Cu: 1-3 mass%) adjusts the material's thermal expansion coefficient and strength to match the compact module's thermal stress conditions, enabling small size while maintaining high-temperature reliability.
Solution Approach 2:
The patent uses a cost-effective solder composition that provides sufficient reliability for the application lifecycle. The alloying elements are selected and quantified to achieve the necessary performance in compact modules without excessive cost, balancing material longevity requirements with economic constraints in automotive applications.
3Reliability
If solder composition is optimized for reliability, then Ni diffusion is suppressed, but manufacturing complexity increases
Solution Approach 1:
The patent defines specific parameter ranges for each alloying element (Sb: 5-10 mass%, Ag: 2-5 mass%, Cu: 1-3 mass%, Ni: 0.01-1 mass%) that balance reliability improvement with manufacturing feasibility. These ranges are wide enough to allow standard manufacturing tolerances while narrow enough to prevent Ni diffusion and void formation, resolving the contradiction between reliability optimization and manufacturing simplicity.
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 enhances the reliability of power semiconductor modules by suppressing Ni diffusion and void formation, improving thermal resistance and long-term reliability, as demonstrated by power cycling tests showing high P/C capability.
Implementation Method 1
Cu diffuses to form a protective SnCu alloy at the Ni interface
Implementation Method 2
form a protective SnCu alloy
Implementation Method 3
a solder bonding the back surface of the semiconductor device element to the stacked substrate
Data Source
AI summary
A semiconductor module, including: a stacked substrate; a semiconductor device element mounted on the stacked substrate, the semiconductor device element having an Ni layer at a back surface thereof; and a solder bonding the back surface of the semiconductor device element to the stacked substrate. The solder is formed of a composition containing: Sb in a range of more than 6 mass % but not more than 8.5 mass %, Ag in a range of 2 mass % to 4.5 mass %, Cu in a range of 1.25 mass % to 2.0 mass %, and Sn as a remaining portion thereof.