Polymer-Free Silver Nanoparticle Die Attach for Low-Temperature Sintering
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Solution Overview
Problem
Current die bonding technologies for wide bandgap semiconductor devices, such as silicon carbide and gallium nitride, face limitations in high-temperature operations due to the unsatisfactory thermal and electrical conductivities of solder alloys and conductive adhesives, and the use of polymer binders in silver nanoparticle pastes leads to porosity and mechanical instability.
Innovation Solution
A low-temperature, low-pressure sintering process using silver nanoparticles, synthesized without polymer binders, is applied to form a sintered silver die attachment layer between the semiconductor die and substrate, ensuring controlled particle sizes and minimal contamination, thereby improving conductivity and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder alloys and conductive adhesives are used for die bonding, then the bonding process is simple, but the thermal and electrical conductivities are insufficient for wide bandgap devices operating at elevated temperatures
Solution Approach 1:
The invention changes the material parameters by using silver nanoparticles instead of traditional solder alloys or conductive adhesives. This material substitution enables significantly improved thermal and electrical conductivities while maintaining processability through the sintering process, directly resolving the contradiction between performance and manufacturability
Solution Approach 2:
The invention employs composite material structure by combining silver nanoparticles with organic vehicle to form a paste that can be screen-printed, then sintered to create a dense metallic bonding layer. This composite approach enables both ease of application and superior final properties
2Manufacturing precision
If traditional sintering process is used for silver nanoparticles, then high density bonding layer can be achieved, but premature particle agglomeration occurs and requires high temperature and pressure
Solution Approach 1:
The invention applies local quality control by using organic vehicles that provide localized protection to individual silver nanoparticles during storage and processing. This localized protective mechanism prevents premature agglomeration at the particle level, enabling low-temperature sintering while achieving high density in the final bonding layer
Solution Approach 2:
The organic vehicle acts as an intermediary substance that mediates between the silver nanoparticles and the environment. It prevents direct contact and agglomeration of particles before sintering, and facilitates controlled densification during low-temperature sintering, thereby achieving high density without requiring extreme temperature and pressure
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 process results in a polymer-free, low-porosity silver bonding layer with enhanced thermal and electrical conductivity, supporting reliable high-temperature operations of wide bandgap semiconductor devices.
Implementation Method 1
the silver nanoparticle is synthesized through a chemical reduction process in an organic solvent
Implementation Method 2
the organic solvent is removed through evaporation with a flux of inert gas being injected into the solution
Implementation Method 3
The sintered silver die attachment layer is formed by sintering silver nanoparticle paste under a very low temperature, for example, lower than 200° C. and in some embodiments at about 150° C., and under a pressures lower than or equal to 5 MPa
Data Source
AI summary
The disclosure is directed to wide band-gap semiconductor devices, such as power devices based on silicon carbide or gallium nitride materials. A power device die is attached to a carrier substrate or a base using sintered silver as a die attachment material or layer. The carrier substrate is, in some embodiments, copper plated with silver. The sintered silver die attachment layer is formed by sintering silver nanoparticle paste under a very low temperature, for example, lower than 200° C. and in some embodiments at about 150° C., and with no external pressures applied in the sintering process. The silver nanoparticle is synthesized through a chemical reduction process in an organic solvent. After the reduction process has completed, the organic solvent is removed through evaporation with a flux of inert gas being injected into the solution.