Solder Alloy Composition for Spalling-Resistant ECU Joints
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Solution Overview
Problem
Solder joints in in-vehicle electronic circuits, particularly ECUs, face issues with 'spalling' due to thermal expansion and contraction, leading to crack generation and malfunction, which can cause serious accidents, and existing solder alloys with Ni exacerbate this problem by affecting acoustic quality and heat cycle characteristics.
Innovation Solution
A solder alloy composition of Ag: 3.1 to 4.0% by mass, Cu: 0.6 to 0.8% by mass, Bi: 1.5 to 5.5% by mass, Sb: 1.0 to 6.0% by mass, Co: 0.001 to 0.030% by mass, Fe: 0.02 to 0.05% by mass, and a balance of Sn, with optional As and Zr, is developed to prevent spalling and enhance heat cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni is added to the solder alloy to improve heat cycle characteristics, then the solder joint can withstand thermal expansion and contraction better, but spalling occurs more frequently and acoustic quality deteriorates
Solution Approach 1:
The patent removes Ni from the solder alloy composition to eliminate the harmful spalling effect and acoustic quality deterioration. The composition specifies Ag: 1 to 4% by mass, Cu: 0.6 to 0.8% by mass, Sb: 1 to 5% by mass, and the balance Sn, with no Ni content, thereby extracting the problematic element while maintaining heat cycle resistance through the remaining alloying elements.
Solution Approach 2:
The patent changes the compositional parameters by defining specific ranges for Ag (1-4%), Cu (0.6-0.8%), and Sb (1-5%), and setting the balance as Sn. This parameter optimization achieves improved heat cycle characteristics without Ni, preventing spalling while maintaining structural integrity under thermal stress.
2Adaptability or versatility
If the solder joint is subjected to repeated thermal cycling in extreme temperature environments, then the electronic circuit can operate in severe conditions, but cracks generate in the solder joint and reliability decreases
Solution Approach 1:
The patent employs a composite solder alloy system combining multiple elements (Ag, Cu, Sb, Sn) in specific proportions. This composite composition creates a synergistic effect where Ag and Cu provide strength and ductility, while Sb enhances heat cycle resistance, collectively enabling the solder joint to withstand repeated thermal cycling without crack generation.
Solution Approach 2:
The patent optimizes the compositional parameters within specific ranges: Ag at 1-4% by mass, Cu at 0.6-0.8% by mass, and Sb at 1-5% by mass. These parameter adjustments create a balanced microstructure that accommodates thermal expansion and contraction, maintaining solder joint integrity under extreme temperature variations.
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 proposed solder alloy effectively suppresses spalling and void generation, improving acoustic quality and heat cycle performance, reducing crack rates and maintaining shear strength even under extreme temperature conditions, thus ensuring reliable operation of in-vehicle electronic circuits.
Implementation Method 1
the electronic component and the printed board each cause thermal expansion and contraction
Implementation Method 2
stress is thus repeatedly applied due to the temperature changes
Data Source
AI summary
A solder alloy comprises Ag: 3.1 to 4.0% by mass, Cu: 0.6 to 0.8% by mass, Bi: 1.5 to 5.5% by mass, Sb: 1.0 to 6.0% by mass, Co: 0.001 to 0.030% by mass, Fe: 0.02 to 0.05% by mass, and a balance Sn.