Coated Silver Sintering Paste for Pressureless Copper Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing silver sintering methods face challenges in forming reliable connections on non-precious metal contact surfaces, such as copper, without mechanical pressure and at low sintering temperatures, and often require pretreatment of the metal surfaces.
Innovation Solution
A silver sintering method using a silver sintering preparation comprising 70-95 wt.% coated silver particles with silver acetylacetonate or silver salts thermally decomposable above 160°C, applied as a paste or preform, which forms reliable connections between electronic components without pretreatment and mechanical pressure, even at room temperature, by decomposing into elemental silver during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If silver sintering is performed on non-precious metal contact surfaces like copper without pretreatment, then the process complexity is reduced, but the connection reliability deteriorates
Solution Approach 1:
The patent applies preliminary action by incorporating a coating on silver particles that contains compounds (such as organic acids, carboxylic acids, or their derivatives) which react with copper surfaces in advance during the sintering process. This pre-reactive coating enables the silver to bond reliably with copper without requiring separate pretreatment steps like oxidation or cleaning, thus reducing process complexity while maintaining connection reliability
Solution Approach 2:
The patent uses an intermediary substance - the coating on silver particles containing reactive compounds - that mediates between the silver and the copper surface. This coating acts as a chemical intermediary that facilitates bonding between dissimilar metals (silver and copper) without requiring direct contact or complex surface preparation, resolving the contradiction between simple process and reliable connection
2Use of energy by moving object
If silver sintering is performed at low temperatures without mechanical pressure, then the energy consumption is reduced, but the connection strength deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the sintering process by using silver particles with specific coatings containing compounds that lower the effective reaction temperature. The coating compounds (such as organic acid derivatives) enable chemical reactions and bonding at lower temperatures than conventional sintering, achieving strong connections without high energy input or mechanical pressure
Solution Approach 2:
The patent replaces the mechanical sintering system (which requires high pressure and temperature) with a chemical system where the coating compounds facilitate bonding through chemical reactions. This substitution allows connection formation at low temperatures without mechanical pressure, reducing energy consumption while maintaining connection strength
3Reliability
If pretreatment of metal surfaces is applied before silver sintering, then the connection reliability is improved, but the manufacturing time increases
Solution Approach 1:
The patent merges the pretreatment function and the sintering function into a single integrated process step. The coating on silver particles performs both the surface preparation role (by reacting with and preparing the copper surface) and the bonding role (by forming the silver-copper connection) simultaneously during one sintering cycle, eliminating separate pretreatment time while maintaining connection reliability
Solution Approach 2:
The patent incorporates the pretreatment action into the sintering process itself through the pre-applied coating on silver particles. The coating compounds are already present on the silver particles before sintering, so they perform the surface preparation function during the sintering reaction, eliminating the need for separate pretreatment steps and reducing manufacturing time
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 method achieves strong and reliable connections between electronic components with varying metal contact surfaces, including non-precious metals like copper, without the need for pretreatment or high sintering temperatures, ensuring stability at both room and elevated temperatures.
Implementation Method 1
wherein the at least one silver salt is thermally decomposable at >160° C.
Data Source
AI summary
A silver sintering preparation in the form of a silver sintering paste comprising 70 to 95 wt.-% of coated silver particles (A) and 5 to 30 wt.-% of organic solvent (B) or in the form of a silver sintering preform comprising 74.5 to 100 wt.-% of coated silver particles (A) and 0 to 0.5 wt.-% of organic solvent (B), wherein the coating of the coated silver particles (A) comprises at least one silver salt of the formula CnH2n+1COOAg with n being an integer in the range of 7 to 10, and wherein the at least one silver salt is thermally decomposable at >160° C.