Lead-Free Conductive Paste for SiC Chip Bonding
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Solution Overview
Problem
Conductive pastes used in semiconductor devices often contain harmful materials like lead, arsenic, tellurium, or antimony, and struggle to maintain bond strength at high temperatures, especially when bonding silicon carbide (SiC) chips to substrates.
Innovation Solution
A conductive paste comprising conductive particles, a lead-free glass frit with a remelting temperature of 320 to 360°C, and a solvent, along with optional metal oxides, which allows for bonding at low temperatures and maintains strength at high temperatures through controlled heating and cooling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional low melting-point glass (PbO-B2O3 glass) is used, then bonding temperature can be reduced, but harmful materials (lead, arsenic, tellurium, antimony) are introduced
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by replacing harmful materials (PbO, TeO2, Sb2O3, As2O3) with safe alternatives (Bi2O3, ZnO, B2O3, SiO2) while maintaining the low melting point property through optimized ratios of these substitute components
Solution Approach 2:
The patent uses readily available, environmentally friendly oxide materials (bismuth oxide, zinc oxide, boron oxide, silicon oxide) that can be easily sourced and processed, replacing expensive and hazardous materials while achieving the same functional effect of low-temperature bonding
2Temperature
If glass with lower remelting temperature is used, then bonding temperature is reduced, but bond strength at high temperature deteriorates
Solution Approach 1:
The patent creates a composite glass frit system combining multiple oxide components (Bi2O3, ZnO, B2O3, SiO2) where each component contributes specific properties: Bi2O3 and ZnO provide low melting point, while B2O3 and SiO2 contribute to high-temperature stability and bond strength, achieving both low bonding temperature and high temperature resistance
Solution Approach 2:
The patent assigns different functional roles to different components within the glass frit: Bi2O3 and ZnO primarily responsible for lowering the remelting temperature to enable low-temperature bonding, while B2O3 and SiO2 provide structural stability and maintain bond strength at high operating temperatures (300-350°C)
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 paste enables effective bonding of SiC chips to substrates at low temperatures and maintains bond strength even at high temperatures (300 to 350°C), reducing heat energy consumption and ensuring high reliability and thermal cycling properties.
Implementation Method 1
a glass frit containing substantially no lead, arsenic, tellurium, and antimony and having a remelting temperature of 320 to 360°C.
Implementation Method 2
ensuring high reliability and thermal cycling properties
Data Source
AI summary
A conductive paste including (A) conductive particles, (B) a glass frit containing substantially no lead, arsenic, tellurium, and antimony, and (C) a solvent. The glass frit (B) has a remelting temperature of 320 to 360° C., wherein the remelting temperature is indicated by a peak top of at least one endothermic peak having an endotherm of 20 J/g or more in a DSC curve as measured by a differential scanning calorimeter. The conductive paste can also include at least one metal oxide (D) selected from the group consisting of tin oxide, zinc oxide, indium oxide, and copper oxide. The glass frit (B) can further include (B-1) Ag2O, (B-2) V2O5, and (B-3) MoO3. The conductive paste can achieve binding at a relatively low temperature (such as 370° C. or lower) and maintains a bond strength at a relatively high temperature (such as 300 to 360° C.).