Noble Metal Paste for Semiconductor Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing precious metal pastes for bonding semiconductor elements face issues such as contamination from residual resins, uneven coating, and void generation due to organic solvent volatilization, which affect the quality of the sintered compact and bonding performance.
Innovation Solution
A precious metal paste comprising a high-purity (99.9 mass %) powder with an average particle diameter of 0.1 to 0.5 μm and an organic solvent with a boiling point of 200 to 350°C, combined with a thixotropy index of 6.0 or more, ensuring uniform coating, preventing contamination, and allowing controlled outgassing during sintering to prevent void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resin-containing paste is used for bonding, then the paste can be uniformly coated and maintains good adhesion, but the resin remains after bonding and causes contamination of the semiconductor element
Solution Approach 1:
The invention extracts and removes the resin component from the paste formulation, replacing it with an organic solvent that evaporates completely during heating. This eliminates the contamination source while maintaining the paste's coating properties through proper formulation of metal powder and solvent ratios.
Solution Approach 2:
The invention changes the chemical composition parameters of the paste by specifying metal powder purity of 99.9 mass% or more and using organic solvents with specific boiling points (200-350°C). These parameter changes ensure complete decomposition and evaporation without residue, solving the contamination problem while maintaining coating quality.
2Object-affected harmful factors
If a paste without resin is used to avoid contamination, then contamination is reduced, but the paste becomes difficult to coat uniformly due to metal particle aggregation and organic solvent bleeding
Solution Approach 1:
The invention optimizes multiple parameters simultaneously: metal powder purity (99.9 mass% or more), particle diameter (0.1 to 0.5 μm), organic solvent boiling point (200-350°C), and paste viscosity (10 to 100 Pa·s at 20°C). These coordinated parameter changes prevent particle aggregation and solvent bleeding while maintaining coatability.
Solution Approach 2:
The invention creates a composite paste system combining high-purity metal powder with specifically selected organic solvents. This composite formulation achieves synergistic effects where the solvent properly wets and disperses the metal particles during coating, then evaporates cleanly during heating, resolving both coating and contamination issues.
3Temperature
If a paste with organic solvent is used for low-temperature bonding, then bonding temperature can be reduced, but voids are generated in the sintered compact due to solvent volatilization
Solution Approach 1:
The invention changes the organic solvent selection to compounds with boiling points of 200-350°C, which volatilize at controlled rates during heating. This parameter change allows complete solvent removal before final sintering, preventing void formation while maintaining low bonding temperatures below 300°C.
Solution Approach 2:
The invention ensures continuous and complete evaporation of the organic solvent during the heating process by selecting solvents with appropriate volatility characteristics. This continuous removal prevents solvent trapped in the sintered compact from forming voids, maintaining compact quality throughout the bonding process.
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 enables contamination-free bonding, uniform coating, and dense sintering of the precious metal paste, achieving high bonding strength and adhesion without residual solvent or voids, making it suitable for large-area die bonding.
Implementation Method 1
the organic solvent has a boiling point of 200 to 350° C.... outgassing by volatilization and decomposition of the organic constituent can be uniformly released when heating in bonding
Implementation Method 2
the precious metal paste has a thixotropy index (TI) value of 6.0 or more... dispersibility of the precious metal particle after coating can be uniformly maintained
Implementation Method 3
sintering the gold by heating the paste after coating... the generation of a void can be suppressed
Data Source
AI summary
A precious metal paste which does not cause contamination of a member, which can be uniformly coated to a member to be bonded, and which is in good condition after bonding is provided. The present invention relates to a precious metal paste for bonding a semiconductor element, of the paste including a precious metal powder and an organic solvent, in which the precious metal powder has a purity of 99.9 mass % or more and an average particle diameter of 0.1 to 0.5 μm, the organic solvent has a boiling point of 200 to 350° C., and a thixotropy index (TI) value calculated from a measurement value of a viscosity at a shear rate of 4/s with respect to a viscosity at a shear rate of 40/s at 23° C. by means of a rotational viscometer is 6.0 or more.