Copper Bonding Composition for Uniform Pressurized Sintering
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Solution Overview
Problem
Conventional bonding compositions for conductors using sintered copper particles can flow out from between conductors, leading to uneven thickness and reduced reliability in semiconductor packages, especially when applied under pressure.
Innovation Solution
A bonding composition containing copper powder, a liquid medium, and a reducing agent with specific properties, including at least one amino group and multiple hydroxyl groups, is applied, dried, and then sintered under pressure to form a dense joint portion with controlled thickness and high bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sintering is performed under pressure to increase bonding strength, then bonding strength is improved, but the composition flows out from between the conductors causing uneven thickness
Solution Approach 1:
The patent applies parameter changes by carefully controlling the melting point of the binder within a specific range (100°C to 200°C) and setting the sintering temperature (150°C to 350°C) above this melting point. This parameter optimization allows the binder to melt and facilitate particle bonding under pressure while maintaining sufficient viscosity to prevent excessive flow-out, thus achieving both high bonding strength and thickness uniformity
Solution Approach 2:
The patent uses a composite material system consisting of copper particles (50-200 μm), binder (1-20 parts by weight per 100 parts copper), and liquid medium. This composite structure combines the high strength of sintered copper with the flow control properties of the optimized binder, enabling the composition to maintain shape during pressurized sintering while achieving strong bonding between conductors
2Ease of manufacture
If solder is used as bonding material, then ease of manufacture is improved, but heat resistance deteriorates
Solution Approach 1:
The patent fundamentally changes the material parameter from conventional solder to a sinter-type bonding material with copper particles and a specifically designed binder system. This material substitution enables the bonding to withstand temperatures above 175°C while maintaining ease of manufacture through a simplified process that requires only heating to the sintering temperature range (150°C to 350°C) without complex multi-step procedures
Solution Approach 2:
The patent replaces the mechanical alloying and complex metallurgical processes of traditional soldering with a thermal sintering process. By using copper particles as the primary bonding material and a organic binder as aid, the process substitutes complex mechanical/chemical soldering operations with a simpler heating and pressing operation, achieving both ease of manufacture and high heat 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 composition effectively prevents overflow during pressure sintering, ensuring uniform thickness and high bonding strength, enhancing the reliability and thermal conductivity of the conductor joints.
Implementation Method 1
a reducing agent having a plurality of hydroxyl groups; the reducing agent has a boiling point that is higher than the boiling point of the liquid medium; and the reducing agent has a melting point that is equal to or below the sintering temperature of the copper powder
Implementation Method 2
drying the coating film, to remove at least a portion of the liquid medium
Implementation Method 3
heating the dried coating film, to sinter the copper powder contained in the dried coating film
Implementation Method 4
the reducing agent has a melting point that is equal to or below the sintering temperature of the copper powder
Data Source
AI summary
A bonding composition contains copper powder, a liquid medium, and a reducing agent. The reducing agent contains at least one amino group and a plurality of hydroxyl groups. The reducing agent has a boiling point that is higher than the boiling point of the liquid medium. The reducing agent has a melting point that is equal to or below the sintering temperature of the copper powder. Preferably, the reducing agent is bis(2hydroxyethyl)iminotris(hydrox ymethyl)methane. Preferably, the bonding composition has a viscosity of from 10 Pa·s to 200 Pa·s at a shear rate of 10 s−1 at 25° C. Preferably, the bonding composition contains from 0.1 parts to 10 parts by mass of the reducing agent and from 10 parts to 40 parts by mass of the liquid medium with respect to 100 parts by mass of the copper powder.