Copper Preform Bonding Sheet for Void-Free Sintered Joints
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Solution Overview
Problem
Existing bonding methods for electronic components face challenges such as high manufacturing costs, reliability concerns due to voids from organic substances, and low strength of intermetallic compounds, leading to potential collapse of porous sheets used as preform materials.
Innovation Solution
A bonding sheet with a porous preform layer composed of copper particles coated with copper nanoparticles, where the average porosity is between 11% and 78%, and the average particle diameter of the nanoparticles is between 9.59 nm and 850 nm, is used to create a strong bonding layer by sintering when pressed between a substrate and an electronic component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a paste containing micrometer-sized metal particles, binder, and solvent is used for bonding, then bonding performance is improved, but manufacturing cost increases and voids are generated leading to decreased bonding reliability
Solution Approach 1:
The invention extracts and removes the problematic organic components (binder, flux, solvent) from the bonding material system, replacing them with a solvent-free paste containing only metal particles and copper powder. This eliminates void formation from organic substance decomposition while maintaining bonding effectiveness.
Solution Approach 2:
The invention employs a porous preform sheet made of copper powder with controlled pore structure. This porous structure allows for efficient sintering and bonding while eliminating the need for organic binders and solvents, thereby preventing void formation and reducing manufacturing complexity.
2Strength
If an intermetallic compound such as Cu6Sn5 is used for bonding, then bonding strength is improved, but the preform material strength becomes low and shape collapse occurs
Solution Approach 1:
The invention creates a composite preform material consisting of copper powder particles embedded in a porous copper matrix. This composite structure provides both the bonding strength needed for reliable connections and the structural stability required to maintain shape during handling and assembly processes.
Solution Approach 2:
The invention changes the physical and chemical parameters of the preform material by using copper powder with specific particle size distributions and controlling the porosity of the matrix. These parameter adjustments enable the material to achieve optimal balance between bonding strength and shape stability.
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 bonding sheet provides high strength and prevents shape collapse, ensuring a reliable bond between the substrate and electronic component with improved sinterability and bonding strength.
Implementation Method 1
the copper nanoparticles are easily sintered to bind the copper particles to each other
Data Source
AI summary
This bonding sheet (10, 20) with a preform layer (13) is a bonding sheet (10, 20) for bonding a substrate (16) and an electronic component (17), the bonding sheet (10, 20) includes a copper sheet (11) and a porous preform layer (13) including copper particles (12) provided on one surface or both surfaces of the copper sheet (11), in which surfaces of the copper particles (12) are coated with copper nanoparticles (12a) having an average particle diameter smaller than an average particle diameter of the copper particles (12), the average particle diameter of the copper nanoparticles (12a) calculated from a BET value is 9.59 nm or more and 850 nm or less, and an average porosity of the preform layer (13) is 11% or more and 78% or less.