Anisotropic Conductive Material Bonding Reliability
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Solution Overview
Problem
Conventional anisotropic conductive materials using low melting point particles face issues with high contact resistance between upper and lower conductors and low insulation resistance between adjoining conductors due to excessive fluidity of low melting point particles during thermocompression bonding.
Innovation Solution
The use of low melting point particles with a solidus temperature of at least 125°C and a peak temperature of no more than 200°C, ensuring a temperature difference of at least 15°C, which prevents premature melting and maintains reliable bonding and conductivity by controlling the fluidity of the particles within the thermosetting resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low melting point particles are used in anisotropic conductive material, then bonding reliability is improved, but contact resistance increases and insulation resistance decreases due to excessive fluidity during thermocompression bonding
Solution Approach 1:
The invention changes the temperature parameter characteristics of low melting point particles by specifying a solidus temperature of at least 125°C and a peak temperature of no more than 200°C with a temperature difference of at least 15°C. This parameter optimization controls the fluidity of particles during thermocompression bonding, preventing premature melting while ensuring reliable bonding, thereby resolving the contradiction between bonding reliability and electrical resistance characteristics
Solution Approach 2:
The invention utilizes the dynamic melting process of low melting point particles during thermocompression bonding. By controlling the temperature difference between solidus and peak temperatures to be at least 15°C, the particles exhibit controlled fluidity dynamics - remaining solid during positioning but melting appropriately during bonding to ensure reliable contact while maintaining proper contact and insulation resistance
2Strength
If low melting point particles melt during thermocompression bonding, then bonding strength is improved, but particle fluidity causes short circuits between adjoining conductors
Solution Approach 1:
The invention optimizes the melting temperature parameters of low melting point particles by setting the solidus temperature at least 125°C and peak temperature at most 200°C with a temperature difference of at least 15°C. This controlled parameter range ensures particles melt at the appropriate stage during thermocompression bonding to provide bonding strength while preventing premature melting that would cause short circuits between adjoining conductors
Solution Approach 2:
The invention controls the melting process to occur at the precise moment needed - during thermocompression bonding when bonding strength is required. The temperature difference of at least 15°C between solidus and peak temperatures creates a controlled transition that skips the harmful intermediate state where particles would be too fluid and cause short circuits, rushing through to the bonded state when strength is achieved
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 ensures stable metallic bonding between conductors, maintaining conductivity and insulation resistance, even under temperature fluctuations and environmental changes, thereby enhancing the reliability and performance of anisotropic conductive materials.
Implementation Method 1
low melting point particles having a solidus temperature measured with a DSC of at least 125° C. and a peak temperature of no more than 200° C., and having a temperature difference between the solidus temperature and the peak temperature of at least 15° C.
Implementation Method 2
When they are bonded to FPC's (flexible printed circuits), an anisotropic conductive material such as an anisotropic electric-conductive adhesive is used. The anisotropic conductive material achieves thermocompression bonding
Implementation Method 3
If heating by the heater block 8 is continued and the curing temperature of the thermosetting resin is reached, the thermosetting resin 6 is cured and the upper and lower substrates are securely bonded to each other.
Data Source
Figure 1~2
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Figure 5~6
AI summary
[PROBLEMS] To provide an anisotropic electroconductive material which can solve problems of the conventional anisotropic electroconductive material using low-melting particles as electroconductive particles that the electroconductivity between conductors in a vertical direction necessary for good continuity is low and, further, the insulating resistance between adjacent conductors necessary for high insulating resistance is low. [MEANS FOR SOLVING PROBLEMS] An anisotropic electroconductive material in which the solidus line of low-melting particles is 125°C or above, the peak temperature is 200°C or below, and the difference in temperature between the solidus line temperature and the peak temperature is 15°C or above. The low melting point particles are made of an alloy having a composition in the range of 25 -75 mass % of Bi, optionally a total of at most 2 mass % of at least one of Ag, Cu, Ni, Co, P, Ge, and Zn and a remainder of Sn. Among the low-melting particles, the maximum diameter of the low-melting particles is smaller than one-fourth of the distance between the adjacent conductors.