Hot-Melt Adhesive Sheet Bonding for OSP Electrode Reliability
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Solution Overview
Problem
Conventional anisotropic conductive films (ACF) using thermosetting resins face challenges in achieving low-temperature, low-pressure, and short-time connections while maintaining sufficient connection resistance and adhesion strength, especially when electrode surfaces undergo OSP treatment, leading to storage stability issues and reduced productivity.
Innovation Solution
A joined body production method using a hot-melt adhesive sheet with solder particles in a crystalline polyamide resin binder, where the solder particles have a melting point 30 to 0°C lower than the thermocompression bonding temperature, and the adhesive layer exhibits a melt viscosity ratio of at least 10:1 at specific temperature intervals, enhancing solder wettability and connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermosetting resin is used in conventional ACF, then connection can be achieved, but storage stability deteriorates and setting occurs during storage
Solution Approach 1:
The patent changes the resin type from thermosetting to thermoplastic, fundamentally altering the material's curing behavior. This parameter change eliminates the setting issue during storage while maintaining connection reliability through controlled melting and bonding at lower temperatures.
Solution Approach 2:
The patent uses a composite material system combining thermoplastic resin with specific fillers and additives. This composite formulation provides both storage stability (through non-setting characteristics) and connection reliability (through controlled melting and adhesion at low temperatures).
2Strength
If thermocompression bonding is performed at high temperature and high pressure, then connection strength is improved, but thermal damage to electronic components increases and productivity decreases
Solution Approach 1:
The patent changes the bonding parameters by using a thermoplastic resin that melts at lower temperatures (below 100°C). This allows the bonding process to occur at reduced temperatures and pressures, achieving sufficient adhesion strength while significantly reducing connection time and preventing thermal damage to electronic components.
Solution Approach 2:
The patent replaces the conventional high-temperature thermal bonding mechanism with a low-temperature melting mechanism. The thermoplastic resin melts at low temperatures to enable bonding, substituting the need for high-temperature heating and high-pressure application, thereby reducing both thermal damage and processing time.
3Temperature
If conventional ACF is used for low-temperature connection, then thermal damage is reduced, but connection resistance increases and adhesion strength deteriorates
Solution Approach 1:
The patent employs a specially formulated composite material with thermoplastic resin combined with conductive fillers and adhesion promoters. This composite structure enables low-temperature bonding (reducing thermal damage) while maintaining low connection resistance and high adhesion strength through the synergistic effects of the composite components.
Solution Approach 2:
The patent changes the material parameters by selecting a thermoplastic resin with specific melting characteristics and combining it with optimized filler content and size. This parameter optimization allows the material to melt at low temperatures for bonding while ensuring sufficient electrical conductivity and adhesion, avoiding the trade-off between low temperature and connection quality.
4Reliability
If OSP treatment is applied to electrode surfaces, then corrosion resistance is improved, but adhesion strength deteriorates
Solution Approach 1:
The patent introduces an intermediary substance - the thermoplastic resin composition - that acts as a mediator between the OSP-treated electrode surface and the bonding interface. The resin's specific chemical composition and melting characteristics enable it to adhere effectively to OSP-treated surfaces while maintaining corrosion resistance, resolving the adhesion issue without compromising the OSP treatment benefits.
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 method provides excellent adhesion strength and connection reliability, even with OSP-treated electrode surfaces, by improving solder wettability and suppressing swelling and stretching due to moisture absorption, while allowing for low-temperature, low-pressure, and short-time connections.
Implementation Method 1
solder particles having a melting point of 30 to 0° C. lower than a temperature of thermocompression bonding
Implementation Method 2
When melt viscosities of the hot-melt adhesive sheet containing electroconductive particles are measured under conditions of a heating rate of 5° C./min., a ratio of a melt viscosity at 40° C. lower than the temperature of thermocompression bonding to a melt viscosity at 20° C. lower than the temperature of thermocompression bonding is no less than 10
Implementation Method 3
subjecting a first electronic component and a second electronic component to thermocompression bonding via a hot-melt adhesive sheet containing electroconductive particles
Data Source
AI summary
A joined body production method includes subjecting a first electronic component and a second electronic component to thermocompression bonding via a hot-melt adhesive sheet. The hot-melt adhesive sheet includes a binder and solder particles. The binder includes a crystalline polyamide resin having a carboxyl group. A melting point of the solder particles is 30° C. to 0° C. lower than a temperature of the thermocompression bonding. When melt viscosities of the hot-melt adhesive sheet are measured under a condition of a heating rate of 5° C./min., the hot-melt adhesive sheet has a ratio of a melt viscosity at 40° C. lower than the temperature of the thermocompression bonding to a melt viscosity at 20° C. lower than the temperature of the thermocompression bonding of no less than 10.