Silver Paste Bonding Material for Electronic Parts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for bonding electronic parts, such as Si chips, to metal substrates using silver pastes often result in surface warping or cracking due to uneven film formation and reaction with the substrate, leading to reduced bonding strength.
Innovation Solution
A silver paste bonding material comprising a diol solvent, fine silver particles, and a triol addition agent with a boiling point of 200 to 300 °C and viscosity of 2000 to 10,000 mPa·s, which prevents film cracking and enhances bonding strength by maintaining film flatness and preventing void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is increased to flatten the predried film surface, then surface flatness is improved, but the electronic part may warp or break
Solution Approach 1:
The patent changes the chemical composition parameters of the silver paste by incorporating specific organic compounds (polyols and their derivatives) that modify the film formation characteristics. This allows the predried film to achieve adequate flatness through chemical modification rather than mechanical pressure, thereby protecting the electronic part from warping or breakage
Solution Approach 2:
The organic compounds in the silver paste act as intermediaries that mediate between the solvent and the silver particles during film formation. These intermediaries control the evaporation process and film leveling, enabling flat surface formation without requiring excessive pressure that would damage the electronic part
2Strength
If thickness of predried film is increased to obtain stress relaxation, then bonding strength is improved, but cracks are easily formed due to solvent evaporation
Solution Approach 1:
The patent modifies the physical and chemical parameters of the solvent system by using polyols with specific molecular structures and boiling points. This parameter change allows the film to maintain integrity during solvent evaporation even at increased thickness, enabling stress relaxation without crack formation
Solution Approach 2:
The silver paste is formulated as a composite material containing silver particles dispersed in a specially designed polyol-based solvent system with added organic compounds. This composite structure provides both the necessary stress relaxation capacity and crack resistance during the drying process
3Manufacturing precision
If dispersant is added to form flat coating film, then surface flatness is improved, but dispersant reacts with copper substrate to form aggregates and cracks
Solution Approach 1:
The patent replaces the problematic dispersant with organic compounds that serve their function temporarily during film formation and then decompose or volatilize during the sintering process. These short-living organic additives provide the needed surface leveling effect without leaving harmful residues that would react with the copper substrate
Solution Approach 2:
The patent changes the chemical nature of the additives by selecting organic compounds with specific functional groups and volatility characteristics. These parameter changes ensure the additives provide surface flatness during film formation but do not cause harmful reactions with the copper substrate during 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 proposed solution effectively prevents film cracking and enhances bonding strength, ensuring a strong and reliable bond between the electronic parts and substrates even with increased film thickness, without surface warping or voids.
Implementation Method 1
the silver paste is heated to remove the solvent to form a predried film on the substrate
Implementation Method 2
heating the bonding material to sinter silver therein to form a silver bonding layer to bond the articles to each other
Data Source
AI summary
A bonding material of a silver paste contains: fine silver particles having an average primary particle diameter of 1 to 200 nm, each of the fine silver particles being coated with an organic compound having a carbon number of not greater than 8, such as sorbic acid; and a solvent mixed with the fine silver particles, wherein a diol, such as an octanediol, is used as the solvent and wherein a triol having a boiling point of 200 to 300 °C, a viscosity of 2,000 to 10,000 mPa at 20°C and at least one methyl group, such as 2-methylbutane-2,3,4-triol or 2-methylbutane-1,2,4-triol, is mixed with the solvent as an addition agent.