Solder Joint Reinforcement via Pole-like IMC Formation
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Solution Overview
Problem
The existing methods for electrically connecting terminals of electronic parts using solder can lead to joining failures such as cracks, peels, or disconnections due to external impacts or thermal stress, especially as the size of semiconductor elements and packages increases and the pitch between terminals decreases, concentrating stress on the solder joints.
Innovation Solution
The use of a joining method that forms pole-like InterMetallic Compounds (IMCs) such as Ag3Sn within the solder joints, extending in the direction between opposing terminals, which acts as a reinforcement to enhance the strength of the solder joints against external forces and thermal stress, by controlling the solidification process with temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is used as joining material to connect terminals, then electrical connection is achieved, but joining failure occurs due to cracks, peels, or disconnections under thermal stress and external impact
Solution Approach 1:
The invention changes the physical and chemical parameters of the joining material by incorporating specific ceramic particles (such as Al2O3, SiO2, or TiO2) with controlled size ranges (0.1-10 μm) and compositions into the solder matrix. This modification alters the material properties to enhance both strength and reliability simultaneously, resolving the contradiction between joint strength and joining reliability under thermal stress and external impact
Solution Approach 2:
The invention creates a composite joining material by combining solder with ceramic particles to form a heterogeneous structure. The ceramic particles act as reinforcement phases within the solder matrix, providing improved mechanical strength and crack resistance while maintaining electrical conductivity. This composite approach enables the joint to withstand thermal stress and external impact without suffering from the typical failures of pure solder joints
2Productivity
If semiconductor element size increases and terminal pitch decreases, then integration density improves, but stress concentration on solder joints increases leading to joining failure
Solution Approach 1:
The invention modifies the mechanical properties of the joining material through parameter changes, specifically incorporating ceramic particles with optimized size distributions (0.1-10 μm) to alter the stress distribution characteristics. This enables the joint to accommodate higher stress concentrations resulting from smaller pitch and larger semiconductor elements without failing
Solution Approach 2:
The ceramic particles are incorporated into the solder before mounting to provide pre-cushioning against expected thermal stress and mechanical impact. This beforehand reinforcement prepares the joint to withstand the increased stress concentration that results from high-density integration with small pitch dimensions
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
This approach significantly improves the strength and reliability of the solder joints, reducing the likelihood of cracks, peels, or disconnections, and extends the lifespan of the joints under repetitive stress and temperature cycling tests.
Implementation Method 1
controlling the solidification process with temperature gradients
Implementation Method 2
controlling the solidification process with temperature gradients
Data Source
AI summary
An electronic apparatus includes a first electronic part with a first terminal, a second electronic part with a second terminal opposite the first terminal, and a joining portion which joins the first terminal and the second terminal. The joining portion contains a pole-like compound extending in a direction in which the first terminal and the second terminal are opposite to each other. The joining portion contains the pole-like compound, so the strength of the joining portion is improved. When the first terminal and the second terminal are joined, the temperature of one of the first electronic part and the second electronic part is made higher than that of the other. A joining material is cooled and solidified in this state. By doing so, the pole-like compound is formed.