Copper Paste Composition for Void-Free Sintered Copper Pillars
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Solution Overview
Problem
The formation of sintered copper pillars using copper paste can result in voids, cracks, and peeling at the interface with bonding members, which affects the long-term reliability of the bonded body.
Innovation Solution
A copper paste containing a specific ratio of first sub-micro, second sub-micro, and spherical micro copper particles, along with an organic dispersion medium, is used to form a sintered copper pillar, where the copper particles have specific volume-average particle sizes and shapes to reduce voids, cracks, and peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copper paste containing copper particles and organic dispersion medium is used to form pillar precursor, then sintered copper pillar can be efficiently formed with accuracy, but voids and cracks may occur in the sintered copper pillar and peeling may occur at the interface
Solution Approach 1:
The patent applies parameter changes by precisely controlling the volume-average particle sizes of three different copper particle types (first sub-micro: 0.05-0.35 μm, second sub-micro: 0.5-1.5 μm, spherical micro: 2-5 μm) and their respective mass ratios. This multi-parameter optimization of particle size distribution enables efficient sintering while minimizing voids and cracks, resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The patent uses a composite copper particle system combining three different types of copper particles with specific size ranges and shapes. This composite approach creates a synergistic effect where smaller particles fill gaps between larger particles, densifying the structure and reducing defects, thereby improving both formation accuracy and long-term reliability simultaneously
2Productivity
If electroplating method is used to form copper pillar, then copper pillar can be formed on device, but time is taken to form the pillar and unevenness in height increases when increasing plating rate
Solution Approach 1:
The patent replaces the electroplating process (electrical/chemical system) with a sintering process using copper paste (thermal/mechanical system). This substitution allows the copper pillar to be formed by heating and consolidating copper particles, achieving both high formation speed and height uniformity without the limitations of electroplating rate control
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 use of this copper paste composition effectively minimizes voids, cracks, and peeling at the interface of the sintered copper pillar and bonding members, enhancing the reliability and performance of the bonded body.
Implementation Method 1
a method of forming a pillar precursor between bonding members by using copper paste containing copper particles and an organic dispersion medium, and sintering the pillar precursor to form a sintered copper pillar
Data Source
AI summary
Copper paste for forming a sintered copper pillar containing copper particles and an organic dispersion medium, in which the copper paste contains first sub-micro copper particles having a volume-average particle size of 0.05 to 0.35 μm, second sub-micro copper particles having a volume-average particle size of 0.5 to 1.5 μm, and spherical micro copper particles having a volume-average particle size of 2 to 5 μm as the copper particles, a content of the first sub-micro copper particles is 40 to 70% by mass on the basis of the total mass of the copper particles, a content of the second sub-micro copper particles is 10 to 40% by mass on the basis of the total mass of the copper particles, and a content of the spherical micro copper particles is 15 to 45% by mass on the basis of the total mass of the copper particles.