Vacuum Insulating Glass Seal Using Low-Temperature Solder Diffusion
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Solution Overview
Problem
Conventional high-temperature bonding techniques for hermetically sealing vacuum insulating glass (VIG) units are unsuitable for heat-sensitive components, as they require oven-intensive bulk heating, which can damage thermally tempered glass and organic layers, and traditional lead-based glass frits are being phased out due to environmental concerns, necessitating a low-temperature sealing process that maintains hermeticity and mechanical strength.
Innovation Solution
A method involving a metallic solder pre-form alloy that, when reactively reflowed, forms a hermetic seal by diffusing with multi-layer thin film coatings on the glass substrates, allowing for low-temperature processing without compromising the temper strength of the glass and enabling the use of thermally sensitive materials, such as OLED devices, while avoiding the use of lead-based materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high-temperature bonding techniques are used to hermetically seal VIG units, then sealing reliability is improved, but heat-sensitive components (thermally tempered glass, organic layers, OLED devices) are damaged
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature (above 400°C) to low-temperature (below 200°C) sealing process. This is achieved by using a metallic solder pre-form alloy with a melting point below 200°C, which enables hermetic sealing at temperatures that do not damage heat-sensitive components while maintaining sealing reliability
Solution Approach 2:
The patent employs a composite sealing system consisting of a metallic solder pre-form alloy combined with multi-layer thin film coatings on glass substrates. The solder alloy comprises specific metal combinations (e.g., In-Sn, Ga-In-Sn, Bi-In-Sn) that enable low-temperature bonding, while the thin film coatings provide surface preparation and bonding enhancement, creating a composite material system that achieves hermetic sealing at low temperatures
2Reliability
If lead-based glass frits are used for sealing, then sealing performance is improved, but environmental concerns arise leading to phase-out
Solution Approach 1:
The patent changes the material composition parameter by replacing lead-based glass frits with lead-free metallic solder pre-form alloys. The solder alloys use alternative metal combinations (In-Sn, Ga-In-Sn, Bi-In-Sn, etc.) that provide equivalent or superior sealing performance without the environmental harm of lead, thus eliminating the harmful factor while maintaining sealing reliability
Solution Approach 2:
The patent adopts disposable metallic solder pre-forms that are applied and consumed in the sealing process. These pre-forms are designed for single-use application where the solder is heated, flows, bonds the substrates, and solidifies to form the permanent seal, eliminating the need for reusable lead-based frit systems
3Object-affected harmful factors
If low-temperature sealing process is used to protect heat-sensitive components, then component integrity is improved, but hermeticity and mechanical strength may be compromised
Solution Approach 1:
The patent uses a composite material system where a metallic solder pre-form alloy is combined with multi-layer thin film coatings on the glass substrates. The thin film coatings (metallic or metallizable layers) provide surface preparation, adhesion enhancement, and diffusion control, while the solder alloy provides the hermetic seal. This composite approach ensures that even at low temperatures, the seal achieves sufficient hermeticity and mechanical strength
Solution Approach 2:
The patent optimizes multiple parameters simultaneously: solder alloy composition (using specific metal ratios like In-60Sn-40, Ga-50In-50, etc.), thin film coating composition and thickness, heating rate, peak temperature, and holding time. By carefully controlling these parameters, the patent achieves hermetic sealing with adequate mechanical strength at low temperatures, preventing the worsening of reliability
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 enables the fabrication of VIG units with improved thermal insulation, mechanical strength, and long-term hermeticity at lower temperatures, suitable for harsh environments, without de-tempering the glass or decomposing sensitive layers, and allows for the use of compliant spacers and thin film getter materials.
Implementation Method 1
A first multi-layer thin film coating is formed on a portion of the first substrate that is around and/or on an inner diameter of the hole... A solid solder alloy pre-form is provided in and/or around the hole, with the solid solder alloy pre-form being in direct physical contact with at least a part of the first multi-layer thin film coating... An hermetic hole seal is formed by reactively reflowing the solid solder alloy pre-form to cause material from the first multi-layer thin film coating to diffuse into the solder alloy material and vice versa
Implementation Method 2
forming an inter-metallic compound (IMC) between an uppermost layer of the first multi-layer thin film coating and the reactively reflowed solder
Data Source
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AI summary
Certain example embodiments relate to vacuum insulating glass units having pump-out hole seals formed in connection with solder alloys that, when reactively reflowed, wet pre-coated metallic coatings, and/or associated methods. The alloys may be based on materials that form seals at temperatures that will not de-temper glass and/or decompose a laminate, and/or remain hermetic and lack porous structures in their bulks. SAC, InAg, and/or other preform materials may be used in different example embodiments.