Laser Sealed Glass Substrate Bonding with Composite Sealant
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Solution Overview
Problem
The existing methods for sealing between glass substrates in electronic devices, such as flat panel displays and solar cells, face challenges in achieving high bonding strength and airtightness due to residual stress generated by local heating processes like laser sealing, which reduces the reliability of these devices.
Innovation Solution
A process involving a sealing layer formed by locally heating a material containing sealing glass, a low-expansion filler, and an electromagnetic wave absorbent, with reacted layers produced in the glass substrates to enhance bonding strength, using bismuth glass with specific compositions and heating conditions to ensure effective sealing and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If laser sealing is used to locally heat and melt the sealing material layer, then the thermal influence on the electronic element portion is suppressed, but residual stress is generated at the bonding interfaces causing cracks or fractures and decreased bonding strength
Solution Approach 1:
The patent changes the heating parameters by controlling the laser power, scanning speed, and heating temperature to be at least (T+200°C) to at most (T+800°C) where T is the softening point temperature of sealing glass. This parameter optimization ensures sufficient melting and bonding while controlling residual stress generation.
Solution Approach 2:
The sealing material layer is designed as a composite material containing sealing glass, low-expansion filler, and electromagnetic wave absorbent. This composite structure enables simultaneous achievement of low residual stress (through low-expansion filler matching glass substrates), effective laser heating (through electromagnetic wave absorbent), and proper melting behavior (through sealing glass).
2Reliability
If sealing glass with softening point temperature of 400 to 600°C is used, then moisture resistance is improved, but the electronic element portion properties are deteriorated due to high firing temperature
Solution Approach 1:
The patent replaces conventional thermal field heating (firing furnace) with localized electromagnetic wave heating (laser irradiation). This substitution enables precise spatial control of heating, applying high temperature only where needed for sealing while keeping the electronic element portion at safe temperatures.
Solution Approach 2:
The sealing material layer is designed with localized properties: electromagnetic wave absorbent for selective heating, low-expansion filler for stress control, and sealing glass for moisture resistance. The heating process itself applies local quality by concentrating thermal energy only at the sealing regions between glass substrates.
3Ease of manufacture
If local heating and sealing process is applied, then sealing between glass substrates is achieved, but bonding strength is insufficient due to residual stress generation
Solution Approach 1:
The patent optimizes heating parameters including temperature range (T+200°C to T+800°C), laser power density (250 to 10,000 W/cm²), and scanning speed to achieve proper melting and bonding. These parameter changes ensure sufficient bonding strength while maintaining the advantages of local heating.
Solution Approach 2:
The composite sealing material layer with low-expansion filler reduces thermal expansion mismatch between the sealing layer and glass substrates, thereby reducing residual stress. The electromagnetic wave absorbent ensures efficient energy absorption and uniform heating, improving bonding quality.
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 approach improves the bonding strength between glass substrates and the sealing layer, enhancing the airtightness and reliability of electronic devices while maintaining high reproducibility.
Implementation Method 1
the sealing material containing sealing glass, a low-expansion filler and an electromagnetic wave absorbent
Implementation Method 2
irradiating the sealing material layer with an electromagnetic wave through the first glass substrate and/or the second glass substrate to locally heat the sealing material layer
Implementation Method 3
the sealing material layer is heated at a temperature in a range of at least (T+200° C.) to at most (T+800° C.), whereby the sealing material layer is melted to form a sealing layer
Implementation Method 4
reacted layers are produced in the first and second glass substrates by reaction with the sealing layer
Data Source
AI summary
When local heating by use of laser sealing or the like is applied, the bonding strength between glass substrates and a sealing layer is improved to provide an electronic device having increased reliability. An electronic device includes a first glass substrate, a second glass substrate, and a sealing layer to seal an electronic element portion disposed between these glass substrates. The sealing layer is a layer obtained by locally heating a sealing material by an electromagnetic wave, such as laser light or infrared light, to melt-bond the sealing material, the sealing material containing sealing glass, a low-expansion filler and an electromagnetic wave absorber. In the first and second glass substrates, each reacted layer is produced to have a maximum depth of at least 30 nm from an interface with the sealing layer.