Lead-Free Semiconductor Encapsulation Glass with CeO2 Refining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lead-based glasses for semiconductor encapsulation face issues with adhesion to metallic wires, air-tightness, and environmental concerns due to the use of Sb2O3, which can reduce to metal particulates and affect semiconductor device characteristics, and require high-temperature melting with oxidizing agents, while also lacking automation-friendly properties.
Innovation Solution
A lead-free glass composition with controlled Sb2O3 content at 0.1% or less and the introduction of CeO2, which acts as a refining agent, with a viscosity temperature of 670°C or lower, using a SiO2-B2O3-R2O-based glass with specific oxide ratios to ensure adhesion, low-temperature encapsulation, and automation-friendly inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Sb2O3 is added to the glass composition to improve refinability and air-tightness, then the glass can effectively remove bubbles and ensure encapsulation integrity, but Sb2O3 may reduce to metal particulates that adversely affect semiconductor device characteristics
Solution Approach 1:
The patent changes the chemical composition parameters by strictly limiting Sb2O3 content to 0.1% or less and introducing CeO2 at 0.01-6% by mass. This parameter change prevents Sb reduction to metal particulates while maintaining refining effectiveness through CeO2, thus resolving the contradiction between air-tightness and harmful particulate formation.
Solution Approach 2:
CeO2 acts as an intermediary refining agent that replaces Sb2O3's bubble-removing function. The CeO2 provides oxygen to the glass without reducing to harmful metal particulates, mediating between the need for refinability and the avoidance of Sb metal contamination.
2Reliability
If the glass is melted at high temperature with oxidizing agents to prevent reduction of Sb2O3, then the glass maintains stability and avoids Sb metal formation, but the environmental load increases and production cost rises
Solution Approach 1:
The patent extracts and removes oxidizing agents from the glass composition, eliminating the source of environmental pollution. By using CeO2 instead of Sb2O3 as the refining agent, the need for additional oxidizing agents during melting is eliminated, thus resolving the contradiction between glass stability and environmental load.
Solution Approach 2:
The patent replaces expensive and environmentally harmful oxidizing agents with CeO2, which serves as both the refining agent and oxygen source. This substitution eliminates the need for separate oxidizing agents, reducing both cost and environmental impact while maintaining glass stability.
3Strength
If the oxide film on metallic wire becomes too thick (dark red color), then adhesion between glass and metal wire is strong, but the oxide film may peel off (black color) and encapsulation fails
Solution Approach 1:
The patent changes the encapsulation temperature parameter to 670°C or lower, which controls the oxidation rate and oxide film thickness. At this lower temperature, the oxide film forms at an optimal thickness that ensures strong adhesion without peeling, resolving the contradiction between adhesion strength and encapsulation stability.
4Ease of manufacture
If the glass tube is made transparent for visual inspection, then quality control is easy, but automated inspection by CCD camera becomes difficult
Solution Approach 1:
The patent introduces CeO2 which provides fluorescence properties to the glass. This color/optical property change enables automated CCD camera inspection while maintaining quality control capabilities, resolving the contradiction between visual inspection ease and automation friendliness.
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 lead-free glass provides stable encapsulation, reduces environmental impact, enhances refinability, and allows for automated appearance inspection through fluorescence, ensuring reliable semiconductor device encapsulation without the risks associated with Sb2O3 reduction.
Implementation Method 1
CeO2, which acts as a refining agent
Implementation Method 2
allows for automated appearance inspection through fluorescence
Implementation Method 3
Sb2O3 is apt to be subjected to a reduction action, and also has a function to provide oxygen to the glass, Sb2O3 itself is reduced to metal
Data Source
AI summary
The technical task of the present invention is to provide a lead-free glass for semiconductor encapsulation, which is easy to automate an appearance inspection, and furthermore, has excellent refinability and encapsulatability of semiconductor devices. In the lead-free glass for semiconductor encapsulation according to the present invention, a temperature at which the viscosity of glass is 106 dPa·s is 670° C. or lower, and, as a glass composition, the content of CeO2 is from 0.01 to 6% by mass, and the content of Sb2O3 is 0.1% by mass or less.