Ni-Fe Core Solder Paste for Void-Suppressed Heat-Resistant Joints
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Solution Overview
Problem
Existing solder pastes used in high-temperature applications, such as those for silicon carbide power semiconductor elements, suffer from void formation due to gasified flux remaining in the molten solder, leading to reduced fluidity and poor heat resistance.
Innovation Solution
A solder paste composition comprising a first metal powder of Sn with optional additives and a second metal powder with a core of Ni-Fe alloy and a Ni-containing surface layer, designed to suppress void formation and enhance heat resistance by controlling the formation of high-melting point compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flux is used in the solder paste, then the soldering process can be facilitated, but the flux gasifies during melting and remains in the molten solder, causing a large amount of voids to occur during solidification
Solution Approach 1:
The invention changes the chemical composition parameters of the flux by specifying precise ratios of organic acid (0.5-5 parts by mass), carboxylic acid (0.5-5 parts by mass), and alcohol (1-10 parts by mass). This parameter optimization controls the flux's gasification behavior to reduce void formation while maintaining soldering facilitation.
Solution Approach 2:
The invention uses a composite flux system combining multiple components (organic acid, carboxylic acid, alcohol, and optional additives) to achieve both soldering facilitation and reduced void formation. The composite nature allows synergistic effects where each component contributes to different aspects of the soldering process.
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 solder paste effectively suppresses voids and enhances heat resistance by allowing controlled flux release and formation of high-melting point compounds, ensuring reliable solder joints under high-temperature conditions.
Implementation Method 1
the solder powders form a high-melting point compound during heating. As a result, even in a case where the solder joint is re-heated, it is possible to suppress remelting, so that it is possible to increase heat resistance
Implementation Method 2
the flux gasified during melting of the solder powder remains in the molten solder, and a large amount of voids are thus likely to occur during solidification
Data Source
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AI summary
A solder paste containing a first metal powder, a second metal powder, and a flux is employed. The first metal powder contains Sn. A second metal powder 20A has a core portion 201 formed of an alloy containing Ni and Fe, and a surface layer 202 that covers the core portion 201 and is formed of a metal containing Ni. An Ni content in the metal forming the surface layer 202 of the second metal powder 20A is 50% by mass or more relative to a total mass of the metal forming the surface layer 202 of the second metal powder 20A. The surface layer 202 of the second metal powder 20A has a thickness of 0.05 µm or more and 0.30 µm or less.