Spherical Metal Joining Material for Low-Pressure Dense Sintering
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Solution Overview
Problem
Existing joining materials using silver or copper particles face issues of cracking and porosity when forming thick joining portions under low pressure, which can lead to thermal stress concentration and reduced thermal conductivity.
Innovation Solution
A joining material comprising substantially spherical metal particles with specific size distributions and a solvent, applied at low pressure, to form a dense joining portion with reduced porosity and crack resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high pressure (60 MPa) is applied during firing to reduce porosity and form a dense sintered film, then the joining portion has high resistance to thermal shock and high reliability, but there is a risk of cracking semiconductor chips or deforming substrates and frequent maintenance of press equipment
Solution Approach 1:
The invention changes the particle size parameters of metal particles from conventional fine particles (e.g., 20 nm) to larger particles with D50 of 0.3-0.5 μm and Dmin greater than 0.08 μm. This parameter change allows the joining material to form a dense structure with fewer pores even under low pressure (20 MPa or less), thereby achieving high reliability without causing cracking or deformation
2Reliability
If high pressure (60 MPa) is applied during firing to form a dense sintered film with few pores, then the thermal conductivity of the joining portion is improved, but the press equipment requires frequent maintenance
Solution Approach 1:
By changing the particle size parameters to D50 of 0.3-0.5 μm and Dmin greater than 0.08 μm, the invention enables dense sintered film formation with high thermal conductivity under low pressure conditions, significantly reducing maintenance requirements for press equipment
3Object-affected harmful factors
If low pressure (20 MPa or less) is applied during firing to avoid cracking and deformation, then semiconductor chips and substrates are protected, but the joining portion develops more pores and has reduced thermal conductivity
Solution Approach 1:
The invention uses metal particles with specific size parameters (D50 of 0.3-0.5 μm, Dmin greater than 0.08 μm) that enable effective packing and dense sintering even under low pressure conditions, thereby maintaining high thermal conductivity while protecting semiconductor chips from cracking
Solution Approach 2:
The invention uses a composite particle size distribution with metal particles (A) having D50 of 0.3-0.5 μm and metal particles (B) with Dmin greater than 0.08 μm, creating a densely packed structure that achieves high thermal conductivity under low pressure firing conditions
4Reliability
If conventional fine metal particles (e.g., 20 nm) are used to form a dense sintered film, then high resistance to thermal shock is achieved, but the joining material requires high pressure (60 MPa) application
Solution Approach 1:
The invention changes the particle size from conventional fine particles (20 nm) to larger particles with D50 of 0.3-0.5 μm, which naturally form a denser packed structure requiring significantly lower pressure (20 MPa or less) to achieve the same level of density and thermal shock resistance
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 material effectively suppresses cracking and forms a dense joining portion with few pores even at low pressures, enhancing thermal conductivity and reliability.
Implementation Method 1
a solvent for dispersing the metal particles
Implementation Method 2
the joining material is heated while a laminate of conductive components and the joining material is pressed in the lamination direction
Data Source
Figure 1~2E
Figure 3A~3E
Figure 4~5
AI summary
A joining material includes: metal particles including substantially spherical metal particles (A); and a solvent for dispersing the metal particles, wherein the metal particles (A) have D50 of 0.3 µm to 0.5 µm and a minimum particle size Dmin of greater than 0.08 µm.