Solder Joining for Power Semiconductors
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Solution Overview
Problem
Power semiconductors experience interface peeling due to thermal expansion differences between materials, leading to reduced reliability and increased risk of failure, especially in high-temperature applications.
Innovation Solution
A solder joining technique using a solder material with specific compositions, including Sn, Sb, Ag, Ni, and optionally Ge or Cu, forming intermetallic compounds like (Cu, Ni)6(Sn, Sb)5 and (Ni, Cu)3(Sn, Sb)X at the interface with Cu or Cu-alloy members, enhancing shear strength and thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Pb-free solders (Sn-Ag-based) are used for high-temperature applications, then environmental compatibility is improved, but interface peeling occurs due to thermal expansion differences between materials
Solution Approach 1:
The patent modifies the solder composition by precisely controlling the content of specific elements (Sb: 3-10 mass%, Ag: 2-4 mass%, Ni: 0.1-1.0 mass%, Cu: 0.1-1.2 mass%) to change the physical and chemical properties of the solder joint, thereby improving its resistance to thermal expansion mismatch and interface peeling
Solution Approach 2:
The patent creates a composite solder material combining multiple elements (Sn-Sb-Ag-Ni-Cu) to form a complex alloy system that leverages the beneficial properties of each component: Sb for high-temperature strength, Ag for wettability, Ni for interface stability, and Cu for thermal conductivity, collectively resisting thermal expansion differences
2Temperature
If Sn-Sb-based solder is used for high-temperature joining, then thermal resistance is improved, but ductility deteriorates at elevated temperatures
Solution Approach 1:
The patent optimizes the Sb content within a specific range (3-10 mass%) to balance thermal resistance and ductility, avoiding excessive Sb addition that would improve high-temperature strength but severely compromise ductility, while also incorporating Ni and Cu to maintain ductility at elevated temperatures
3Adaptability or versatility
If repeated thermal cycling occurs in solder joints, then power semiconductor operation is enabled, but crack formation and peeling increase due to repetitive distortion
Solution Approach 1:
The patent adjusts the chemical composition parameters of the solder (specific element contents) to modify the joint's mechanical properties, enabling it to withstand repeated thermal cycling without crack formation or peeling by optimizing the balance between flexibility and strength
Solution Approach 2:
The patent incorporates Ni and Cu elements in specific amounts to create a solder composition that proactively cushions against thermal stress accumulation during thermal cycling, preventing crack initiation and propagation before they can occur
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 provides high-temperature thermal resistance and prevents local shear strain concentration, improving the reliability and durability of electronic devices by maintaining a strong joining interface despite thermal cycling and high environmental temperatures.
Implementation Method 1
forming intermetallic compounds like (Cu, Ni)6(Sn, Sb)5 and (Ni, Cu)3(Sn, Sb)X at the interface with Cu or Cu-alloy member
Implementation Method 2
forming a particular structure at a joining interface
Implementation Method 3
a joining at an interface between different materials peeling off due to a difference in coefficient of thermal expansion
Data Source
AI summary
The present invention suppresses fracture at an interface between different materials, and provides a solder joining which includes: a solder joining layer 10 having a melted solder material, containing Sb at more than 5.0% by mass and 10.0% by mass or less, Ag at 2.0 to 4.0% by mass, Ni at more than 0 and 1.0% by mass or less, and a balance made up of Sn and inevitable impurities; and joining members 11 and 123 at least one of which is a Cu or Cu-alloy member 123, in which the solder joining layer includes a first structure 1 containing (Cu, Ni)6(Sn, Sb)5 and a second structure 2 containing (Ni, Cu)3(Sn, Sb)X (in the formula, X is 1, 2, or 4) at an interface with the Cu or Cu-alloy member 123, and an electronic device and a semiconductor device including the solder joining.