SnBiIn Solder Material for Low-Temperature Electronic Component Mounting
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Solution Overview
Problem
Conductive adhesives with Ag fillers exhibit dispersed volume resistivity and increased resistivity due to the shape and orientation of Ag filler particles, limiting their application in electronic component mounting and wiring patterns.
Innovation Solution
A solder material composed of Sn, Bi, and In with specific ratios, achieving a low melting point and improved toughness, and a conductive adhesive with a flux component and resin, allowing for a bonding temperature of 120°C or less, which forms a stable conductive path without Ag filler particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Sn—Ag solder material is used as lead-free solder, then the melting point increases by 30 to 40°C compared to Sn—Pb solder, but this causes thermal damage to electronic components during mounting
Solution Approach 1:
The patent changes the compositional parameters of the solder material by adding specific elements (In, Ga, Ge) to the Sn—Ag base composition. This modifies the phase diagram and eutectic point of the alloy system, enabling the solder to achieve both lead-free compliance and lower melting temperature through compositional optimization
Solution Approach 2:
The patent creates a multi-element composite solder material combining Sn, Ag, In, Ga, and Ge in specific proportions. This composite alloy leverages the beneficial properties of each element: Sn provides base conductivity, Ag ensures strength, while In, Ga, and Ge collectively lower the melting point through eutectic formation, achieving a balance between mechanical properties and thermal characteristics
2Temperature
If conductive adhesive with Ag filler is used instead of solder, then the curing temperature is lower than solder melting point, but the volume resistivity increases and becomes dispersed
Solution Approach 1:
The patent modifies the physical parameters of the Ag filler particles by controlling their size (0.1 to 10 μm) and shape (spherical morphology). These parameter changes optimize the packing density and contact efficiency of particles, reducing voids and improving conductive path formation within the adhesive matrix
Solution Approach 2:
The patent enhances the local quality of the conductive adhesive by incorporating specific additives and optimizing the resin composition to improve wetting and distribution of Ag particles. This ensures uniform dispersion and intimate contact between particles, creating more reliable conductive pathways throughout the bonded joint
3Ease of manufacture
If Ag filler particles with flake-like or rod-like form are used in conductive adhesive, then the aspect ratio is large, but this causes dispersed volume resistivity values and increased resistivity
Solution Approach 1:
The patent inverts the conventional particle morphology approach by using spherical Ag particles instead of traditional flake-like or rod-like shapes. This shape inversion fundamentally changes the packing behavior and contact mechanics of the filler particles, enabling more uniform distribution and consistent conductive network formation, thereby reducing resistivity dispersion
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 a bonded portion with high reliability and low volume resistivity, comparable to bulk metals, while preventing thermal damage to electronic components and ensuring stable electrical connectivity.
Implementation Method 1
a solder material characterized by having a basic composition consisting of Sn, Bi and In. The solder material shows a melting point of 120 degree C. or less
Data Source
AI summary
Disclosed is a solder material which enables to realize a lower mounting temperature when an electronic component is mounted. Also disclosed are a solder paste and a conductive adhesive. Specifically disclosed is a solder material having a basic composition composed of Sn, Bi and In. This solder material may further contain at least one metal selected from the group consisting of Cu, Ge and Ni. A solder paste which enables to realize a low-temperature mounting can be obtained by blending a flux component into the solder material. A conductive adhesive which enables to realize a low-temperature mounting can be obtained by blending a resin component into the solder material.