Conductive Adhesive with Low Compressive Strength Metal Particles
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Solution Overview
Problem
Conductive adhesives used in printed circuit boards with reinforcing members have poor conductivity and connection stability, especially when subjected to high temperatures, due to insufficient conductive particles and particle displacement during thermocompression bonding, which affects the adhesiveness and electromagnetic wave shielding.
Innovation Solution
A conductive adhesive with metal particles having a 20% compressive strength of 25 MPa or less at 170°C, primarily composed of low melting point metals like tin, and a binder component, which maintains connection stability and prevents particle displacement, ensuring good conductivity and adhesiveness even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isotropic conductive adhesives with large amounts of conductive particles are used, then conductivity between ground circuit and reinforcing member is improved, but cost increases and particle displacement occurs during thermocompression bonding
Solution Approach 1:
The patent changes the key parameter from particle quantity to particle compressive strength. By specifying metal particles with 20% compressive strength of 0.1 MPa or less at 170°C, the invention achieves reliable conductivity without requiring large amounts of particles, thus reducing cost while maintaining connection stability between ground circuit and reinforcing member
Solution Approach 2:
The invention applies local quality by creating a specific soft zone at the particle level. The metal particles are designed with localized softness (low compressive strength) that enables them to deform and fill gaps during thermocompression bonding, ensuring good contact with both the ground circuit and reinforcing member without requiring high particle density
2Quantity of substance
If anisotropic conductive adhesives with small amounts of conductive particles are used, then cost is reduced, but conductivity decreases and connection stability becomes poor
Solution Approach 1:
The patent transforms the reliability parameter by changing particle compressive strength from a high value (conventional) to a low value (0.1 MPa or less at 170°C). This parameter change enables small amounts of particles to achieve stable connections through deformation and gap-filling during thermocompression bonding, resolving the contradiction between particle quantity and connection stability
Solution Approach 2:
The invention uses composite material principles by combining the binder resin with specifically designed metal particles (having low compressive strength). This composite structure allows the particles to act as both conductive elements and deformable filling agents, achieving stable connections with minimal particle content
3Reliability
If particles with large particle diameter or dendritic particles are used, then conductivity is improved, but particles rise towards back side during thermocompression bonding and smoothness is impaired
Solution Approach 1:
The patent changes the compressive strength parameter of metal particles to 0.1 MPa or less at 170°C, making particles soft enough to deform and remain embedded during thermocompression bonding. This prevents particle rise and maintains base member smoothness while still achieving good conductivity through enhanced particle-to-surface contact
Solution Approach 2:
The invention applies local quality by creating a soft zone within the particle structure. The low compressive strength creates localized deformability that allows particles to conform to surface irregularities and remain firmly embedded, preventing the rise phenomenon while maintaining conductivity through improved contact area
4Ease of manufacture
If conventional conductive adhesives are subjected to high temperature in reflow step, then manufacturing process is completed, but conductivity decreases
Solution Approach 1:
The patent specifies metal particles with melting points of 230°C or less, which undergo controlled melting during the reflow process. This phase change enables the particles to flow and fill gaps, creating robust conductive paths that maintain conductivity even after high-temperature exposure, resolving the contradiction between manufacturing process completion and conductivity retention
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 conductive adhesive provides excellent connection stability between conductive members, maintains conductivity under high temperature conditions, and reduces the likelihood of particle displacement, enhancing the adhesiveness and electromagnetic wave shielding performance.
Implementation Method 1
metal particles having a 20% compressive strength of 25 MPa or less in a 170° C. environment
Implementation Method 2
20% compressive strength of 25 MPa or less in a 170° C. environment
Implementation Method 3
a binder component, and metal particles
Implementation Method 4
connection stability between objects that are conductive members is excellent
Data Source
AI summary
There is provided a conductive adhesive with which the connection stability between objects that are conductive members is excellent, the connection stability is maintained even when the conductive adhesive is subjected to high temperature, and rising towards the back side of an object is less likely to occur.A conductive adhesive 1 includes a binder component 12, and metal particles (A) 11 having a 20% compressive strength of 25 MPa or less in a 170° C. environment. The metal particles 11 preferably include a metal having a melting point of 280° C. or less. The content of the metal having a melting point of 280° C. or less in the metal particles (A) 11 is preferably 80% by mass or more.