Power Semiconductor Chip Bonding Composition for Thermal Cycling
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Solution Overview
Problem
Conventional chip bonding compositions for power semiconductor packages face challenges with high thermal conductivity, adhesion, and durability, particularly for SiC and GaN chips, as they tend to delaminate under thermal cycling and have high modulus, leading to issues like cracking and peeling, especially for mid-to large-sized chips.
Innovation Solution
A chip bonding composition comprising silver powder, a mixture of glycidyl amine-based and bisphenol A epoxy resin, a curing agent, glycidyl ether-based diluent, and polysilsesquioxane resin, which provides high thermal conductivity, low modulus, and excellent adhesion, suitable for pressure-free sintering and applicable to high-power SiC and GaN chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional bonding materials (Ag-Pb, SAC) are used for power semiconductor chips, then cost-effectiveness is improved, but thermal stability deteriorates due to remelting at around 180°C causing defects such as cracks and fatigue failure
Solution Approach 1:
The bonding material's melting point parameter is changed from around 180°C (conventional SAC) to above 200°C (eutectic composition), enabling thermal stability for high-temperature power semiconductor operation while maintaining cost-effectiveness through eutectic alloy design
Solution Approach 2:
The bonding material is designed as a composite system combining eutectic composition (for low melting point and fluidity during bonding) with specific metal powder content (30-70 wt%) to achieve both manufacturability and high-temperature thermal stability in the cured bonding layer
2Reliability
If metal sintering is used to provide high adhesive strength and high thermal conductivity, then bonding performance is improved, but process complexity increases and mass production becomes difficult
Solution Approach 1:
The pressure application step is extracted and removed from the sintering process, transforming it from pressure sintering to pressure-free sintering. This simplifies the equipment requirements and enables mass production while maintaining high bonding performance through optimized material composition and curing conditions
Solution Approach 2:
The sintering process parameters are changed from requiring high pressure (30 MPa) and elevated temperature (200-250°C) to low-pressure or pressure-free conditions with controlled temperature and time, achieving mass production compatibility while preserving adhesive strength and thermal conductivity
3Strength
If pressure sintering is used to bond power semiconductor chips, then adhesive strength is improved, but chip damage occurs due to severe pressing during the sintering process
Solution Approach 1:
The mechanical pressure application is extracted and eliminated from the sintering process, preventing chip damage from severe pressing while maintaining adhesive strength through pressure-free sintering mechanisms involving material flow and chemical bonding at optimized temperature and time conditions
Solution Approach 2:
The bonding material acts as an intermediary that facilitates adhesion without requiring direct mechanical pressure on the chip. The material's eutectic composition and metal powder content enable it to flow and bond surfaces together during low-pressure sintering, transferring the bonding function from mechanical force to material-mediated bonding
4Reliability
If conventional chip bonding compositions are used to ensure high heat dissipation properties, then thermal conductivity is improved, but delamination occurs between chip and bonding material due to high modulus under thermal cycling
Solution Approach 1:
The bonding material is designed as a composite containing metal powder (30-70 wt%) dispersed in a eutectic matrix, where the metal powder provides high thermal conductivity for heat dissipation while the eutectic matrix with specific composition (Sn-3-15 wt% In, 0.5-5 wt% Cu, 0.1-5 wt% Ag, 0.1-5 wt% Bi) provides low modulus and high resistance to thermal shock, preventing delamination under thermal cycling
Solution Approach 2:
The modulus parameter of the bonding material is changed from high (conventional materials) to low (optimized eutectic composition with 30-70 wt% metal powder), enabling the material to accommodate thermal expansion differences between chip and substrate during thermal cycling, thereby preventing delamination while maintaining adequate heat dissipation
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 composition ensures excellent thermal conductivity, adhesion, and durability against thermal shock, maintaining strength at high temperatures without re-melting, and is suitable for mid-to large-sized chips, reducing mechanical stress and enhancing reliability.
Implementation Method 1
silver powder, which provides high thermal conductivity
Implementation Method 2
an epoxy resin, a curing agent
Implementation Method 3
a glycidyl ether-based diluent
Implementation Method 4
a polysilsesquioxane (PSQ) resin
Data Source
AI summary
Disclosed is a chip bonding composition for a power semiconductor package, which, by comprising an epoxy resin including glycidyl amine-based epoxy resin and bisphenol A type epoxy resin, a glycidyl ether-based diluent, and a polysilsesquioxane (PSQ) resin, has high thermal conductivity and adhesion, high heat dissipation characteristics, and low modulus characteristics. The chip bonding composition according to the present invention comprises: silver powder; an epoxy resin; a curing agent; a catalyst; a glycidyl ether-based diluent; and a PSQ resin.