In-Sn-Ag Alloy Solder for Low-Temperature Reflow
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Solution Overview
Problem
Existing electrical apparatuses with soldered semiconductor devices on printed wiring boards face reliability issues due to warping and poor mechanical and electrical connections caused by high reflow temperatures, and insufficient resistance to drop impacts, especially when using low-melting-point solder materials like InSn eutectic solder.
Innovation Solution
The use of an In—Sn—Ag alloy with a specific composition containing AgIn2 and Ag2In, where the Ag2In content is lower than the AgIn2 content, is employed as the bonding material, which provides high strength and ductility, and is reflowed at low temperatures to minimize warping and enhance connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high reflow temperatures are used for soldering, then the melting and bonding process is effective, but warping of the semiconductor device and printed wiring board occurs, resulting in poor reliability
Solution Approach 1:
The patent changes the material composition parameter by using In-Sn-Ag alloy solder material containing specific intermetallic compounds (AgIn2 and Ag2In) to achieve low-temperature reflow soldering. This parameter change allows effective bonding at lower temperatures, preventing warping while maintaining connection reliability.
2Temperature
If low-melting-point solder materials like InSn eutectic solder are used, then low-temperature reflow is achieved, but the strength and resistance to drop impact are insufficient
Solution Approach 1:
The patent creates a composite solder material by adding intermetallic compounds (AgIn2 and Ag2In) to the In-Sn-Ag alloy base material. This composite structure combines the low-melting-point characteristic of the In-Sn alloy with the high strength of the intermetallic compounds, achieving both low-temperature reflow and high joint strength.
Solution Approach 2:
The patent applies local quality by distributing specific intermetallic compounds (AgIn2 and Ag2In) within the solder joint structure. These intermetallic compounds are localized within the bonding portion to provide enhanced strength and impact resistance at critical locations while maintaining overall low-temperature processability.
3Shape
If solder materials with low melting points are used, then warping is reduced, but the mechanical and electrical connection reliability under impact or stress is poor
Solution Approach 1:
The patent uses composite In-Sn-Ag alloy solder material containing intermetallic compounds to simultaneously achieve low warping (through low melting point) and high connection reliability (through the strength-providing intermetallic compounds AgIn2 and Ag2In).
Solution Approach 2:
The patent enhances local quality at the bonding interface by incorporating intermetallic compounds that specifically improve mechanical strength and impact resistance at the connection points, while the overall low-melting-point alloy prevents warping of the entire assembly.
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 In—Sn—Ag alloy with a lower Ag2In content than AgIn2 content achieves high strength and ductility, improving the mechanical and electrical connection reliability of the bonding portion, even under impact or stress, while allowing for low-temperature reflow to prevent warping, thus enhancing the overall reliability of the electrical apparatus.
Implementation Method 1
reflowed at low temperatures to minimize warping and enhance connection reliability
Implementation Method 2
mounting methods utilizing soldering are widely used to mount electrical components
Implementation Method 3
a solder material having a low melting point contains an intermetallic compound in order to increase the strength of the solder material
Data Source
AI summary
An electrical apparatus includes a first electrical component; a second electrical component; and an In—Sn—Ag alloy connecting the first electrical component and the second electrical component, the In—Sn—Ag alloy containing AgIn2 and Ag2In, a Ag2In content being lower than a AgIn2 content.