Silver Paste Bonding Material Void Prevention
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Solution Overview
Problem
Conventional silver paste bonding materials suffer from bubble entrainment during printing, leading to surface roughness, cracks, and voids in the silver bonding layer, particularly when forming thick coatings, which compromises the reliability and heat radiation performance of electronic components.
Innovation Solution
A silver paste bonding material comprising fine silver particles, a solvent with a diol and a polar solvent of lower surface tension, and a triol addition agent is used, which prevents bubble entrainment and void formation by lowering the surface tension and improving film formation, even with thick coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the coating film thickness is increased to 150 μm or more to ensure high-temperature reliability, then the bonding layer thickness is sufficient for reliability, but bubble entrainment occurs during printing causing surface roughness, cracks, and voids
Solution Approach 1:
The patent changes the chemical composition parameters of the silver paste by incorporating specific organic compounds (carboxylic acids, alcohols, esters) with controlled carbon numbers and ratios. This modifies the paste's rheological properties, allowing thick coatings (150 μm or more) to be applied without bubble entrainment, thus achieving both sufficient bonding layer thickness for high-temperature reliability and manufacturing precision without surface defects
Solution Approach 2:
The patent creates a composite silver paste formulation combining fine silver particles with a specific mixture of organic compounds (carboxylic acids, alcohols, esters) in controlled ratios. This composite material structure enables the paste to maintain stability and prevent bubble formation during thick coating application, resolving the contradiction between achieving thick bonding layers for reliability and avoiding manufacturing defects
2Strength
If the coating film is thickened to increase bonding layer thickness, then the bonding strength is sufficient, but the shrinkage of the pre-dried film is increased causing surface roughness, cracks, and separation
Solution Approach 1:
The patent adjusts the chemical composition parameters of the organic vehicle in the silver paste, specifically the types and ratios of carboxylic acids, alcohols, and esters. This changes the drying characteristics and shrinkage behavior of the pre-dried film, allowing thick coatings to be formed with sufficient bonding strength while minimizing shrinkage-induced surface roughness, cracks, and separation
Solution Approach 2:
The patent optimizes the local chemical environment within the thick coating by distributing specific organic compounds (with carbon numbers 3-12) throughout the paste formulation. This creates localized properties that control solvent evaporation and film formation uniformly, preventing differential shrinkage that would cause surface defects while maintaining overall bonding strength
3Reliability
If conventional silver paste is used with thick coating, then the bonding layer can be thick enough for reliability, but bubbles are easily involved in the coating film during printing
Solution Approach 1:
The patent modifies the rheological parameters of the silver paste by adjusting the composition of organic compounds (viscosity, surface tension) through selective use of carboxylic acids, alcohols, and esters. This parameter change reduces the paste's tendency to entrain bubbles during printing while maintaining the ability to form thick coating films (150 μm or more) that provide sufficient bonding layer thickness for reliability
Solution Approach 2:
The organic compounds in the patent act as intermediary substances between the silver particles and the coating process. Specifically, the combination of carboxylic acids, alcohols, and esters serves as a mediator that controls the paste's flow and air-release characteristics, preventing bubble entrainment during printing while enabling thick coating formation for reliable bonding
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 solution effectively prevents voids in the silver bonding layer, ensuring high bonding strength and reliability, even at thick film thicknesses, and under low pressure, without surface roughness or cracks.
Implementation Method 1
a solvent containing a first solvent of a diol and a second solvent which is a polar solvent having a lower surface tension than that of the first solvent
Implementation Method 2
heating the bonding material to sinter silver in the bonding material to bond the articles to each other
Data Source
AI summary
There are provided a bonding material, which can prevent voids from being generated in a silver bonding layer by preventing the entrainment of bubbles during the formation of a coating film even if the coating film is thickened, and a bonding method using the same. The bonding material of a silver paste includes fine silver particles, a solvent and an addition agent, wherein the solvent contains a first solvent of a diol, such as octanediol, and a second solvent which is a polar solvent (preferably one or more selected from the group consisting of dibutyl diglycol, hexyl diglycol, decanol and dodecanol) having a lower surface tension than that of the first solvent and wherein the addition agent is a triol.