Copper Particle Bonding Layer Sintering to Prevent Joining Cracks
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Solution Overview
Problem
Existing methods for producing joined bodies using sinterable metal particles, such as copper particles, often result in cracks due to volume contraction in the joining layer, leading to insufficient joining strength between the fillet portion of the joining layer and the substrate.
Innovation Solution
A method involving the use of copper particles with a specific average primary particle size of 0.06 μm to 1 μm and a crystallite size increase rate of 5% or more, sintered in a temperature range of 150°C to 350°C for 45 minutes or less, to form a joining layer that minimizes separation from the target member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If copper particles with high sinterability are used, then sintering temperature can be reduced, but volume contraction increases causing cracks in the joining layer
Solution Approach 1:
The invention changes the particle size parameter of copper particles to a specific range (0.06-1 μm) to achieve optimal sinterability while controlling volume contraction. This parameter optimization allows reduced sintering temperature without causing excessive contraction and cracking in the joining layer.
Solution Approach 2:
The invention performs preliminary action by carefully selecting and preparing copper particles with specific size characteristics before the sintering process. This pre-selection ensures that the particles will sinter properly at lower temperatures without causing the harmful volume contraction that leads to cracks.
2Strength
If the joining layer is sintered to achieve strong bonding, then joining strength improves, but cracks form due to contraction reducing reliability
Solution Approach 1:
The invention optimizes the particle size parameter of copper particles (0.06-1 μm) to achieve a balance between joining strength and crack resistance. This specific size range enables strong bonding while minimizing volume contraction during sintering, thereby preventing crack formation.
Solution Approach 2:
The invention uses copper particles that replicate the optimal size distribution characteristics needed for both strong joining and minimal contraction. By copying the ideal particle size parameters, the process achieves both high strength and high reliability simultaneously.
3Productivity
If copper particles with high crystallite growth rate are used, then sintering speed increases, but volume contraction becomes excessive causing fillet portion separation
Solution Approach 1:
The invention changes the particle size parameter to a specific range (0.06-1 μm) that provides optimal crystallite growth characteristics. This parameter optimization enables sufficient sintering speed while controlling the volume contraction to prevent fillet portion separation, maintaining bonding strength.
Solution Approach 2:
The invention performs preliminary selection of copper particles with specific size characteristics before sintering. This pre-selection ensures that the particles will achieve adequate sintering speed without excessive volume contraction that would cause fillet portion separation, thereby preserving bonding strength.
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 method effectively prevents cracks in the joining layer and enhances the joining strength between the fillet portion and the substrate, ensuring a stable joined body.
Implementation Method 1
heating the coating film to sinter the copper particles to form a joining layer
Implementation Method 2
copper particles having an increase rate of a crystallite size, (D2−D1)/D1×100, of 5% or more, where D1 represents a crystallite size (nm) at 150° C. and D2 represents a crystallite size (nm) at 250° C.
Data Source
AI summary
A method for producing a joined body includes: forming a coating film between a joining target member and a second joining target member, wherein the coating film is formed from a paste containing copper particles, and then heating the coating film to sinter the copper particles to form a joining layer; wherein the copper particles have an average primary particle size of 0.06 μm or more and 1.0 μm or less, and include copper particles having an increase rate of the crystallite size, (D2−D1)/D1×100, of 5% or more, where D1 represents the crystallite size (nm) at 150° C. and D2 represents the crystallite size (nm) at 250° C.; and the coating film is held at a heating temperature of 150° C. or more and 350° C. or less for 45 minutes or less to sinter the copper particles.