Sintering Paste for Die Attachment with Low-Pressure Bonding
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Solution Overview
Problem
Conventional sintering processes require high pressure and temperature, which can be costly and inefficient, and often result in intermetallics and organic residues, limiting the reliability and uniformity of bond lines in component attachment.
Innovation Solution
A composition comprising a metal powder with a d50 range of 0.001 to 10 micrometers, a binder with a softening point between 50 and 170°C, and a solvent, applied as a film on a substrate, followed by low-pressure and low-temperature sintering, allowing for flexible bond line thickness and reduced porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional sintering processes use high pressure and temperature, then attachment strength is achieved, but material costs and energy consumption increase significantly
Solution Approach 1:
The patent changes the physical and chemical parameters of the sintering process by using a specifically formulated paste with controlled particle size distribution (d50: 0.001-10 micrometers), binder content (0.1-5 wt%), and solvent composition. These parameter changes enable effective sintering at reduced temperature (175-400°C) and pressure (0.5-20 MPa) while maintaining attachment strength
Solution Approach 2:
The invention uses a composite paste material comprising metal powder (30-95 wt%), binder (0.1-5 wt%), and solvent, where the binder acts as a flux to facilitate sintering at lower temperatures. This composite formulation enables the sintering process to achieve strong attachments with reduced energy input compared to conventional pure metal powder sintering
2Strength
If conventional sintering processes use high pressure and temperature, then attachment is achieved, but intermetallics and organic residues form, reducing reliability
Solution Approach 1:
The patent optimizes the chemical composition parameters including metal powder purity, binder type and content, and solvent selection to control the sintering reaction. The binder acts as a flux that promotes uniform metal particle bonding while decomposing completely to leave no harmful residues, achieving reliable attachments without intermetallic formation
Solution Approach 2:
The binder material is designed as a temporary component that serves its function during sintering (facilitating particle bonding and acting as flux) and then decomposes completely, leaving no permanent residue. This disposable nature of the binder ensures no contamination or reliability issues from organic residues
3Strength
If conventional sintering processes are used, then component attachment is achieved, but material loss and capital costs increase
Solution Approach 1:
The patent optimizes the metal powder particle size distribution (d50: 0.001-10 micrometers) and packing density to maximize material utilization. The controlled sintering parameters (temperature, pressure, time) ensure complete bonding with minimal material spatter or waste, reducing material loss while maintaining attachment strength
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
This method achieves high thermal and electrical conductivity bonds with uniformity and reliability, reducing material loss and capital costs, enabling lead-free interconnections without intermetallics and minimizing post-cleaning needs, suitable for various industries including electronics and renewable energy.
Implementation Method 1
a binder having a softening point between about 50 and about 170° C.
Implementation Method 2
sintering the assembly at a temperature of about 175 to about 400° C. for about 0.25 seconds to about 30 minutes
Data Source
AI summary
Methods for die attachment of multichip and single components including flip chips may involve printing a sintering paste on a substrate or on the back side of a die. Printing may involve stencil printing, screen printing, or a dispensing process. Paste may be printed on the back side of an entire wafer prior to dicing, or on the back side of an individual die. Sintering films may also be fabricated and transferred to a wafer, die or substrate. A post-sintering step may increase throughput.