Laser-Bonded Thin-Film Hermetic Package for Low-Stress Sealing
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Solution Overview
Problem
Existing hermetically sealed packages face challenges in being thin and flexible, making them unsuitable for applications like fingerprint sensors and intracranial pressure sensors, as they tend to bulge and exhibit high internal stress, and laser joining processes can damage thin substrates.
Innovation Solution
A hermetically sealed package design featuring a thin film cover substrate with a laser bonding line that joins it directly to another substrate without adhesives, allowing for precise thickness control and stress reduction, enabling the creation of thin, flexible, and optically transparent packages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a thin substrate is used for the package, then the package can be made thin and flexible for applications like fingerprint sensors and intracranial pressure sensors, but the substrate tends to bulge and exhibit high internal stress
Solution Approach 1:
The patent employs a thin film substrate (thickness < 200 μm) as the cover substrate to achieve the desired thin and flexible package structure. This thin film design enables applications in fingerprint sensors, contact lenses, and intracranial pressure sensors while maintaining the necessary mechanical flexibility and optical transparency.
Solution Approach 2:
A laser bonding line is introduced as an intermediary joining mechanism between the thin cover substrate and the second substrate. This laser bonding line provides mechanical support and stress distribution without requiring additional bonding materials, enabling the thin substrate to maintain structural integrity while remaining thin and flexible.
2Reliability
If laser joining processes are applied to thin substrates, then hermetic sealing can be achieved, but material will be burned or removed if the laser is targeted too close to the surface
Solution Approach 1:
The laser bonding line acts as an intermediary that absorbs and distributes laser energy away from the thin substrate surface. By positioning the laser bonding line at a specific distance from the outer surface, the laser energy is deposited in the bonding line rather than directly on the thin substrate, preventing material burn-off while achieving hermetic sealing.
Solution Approach 2:
The patent optimizes the distance parameter between the laser bonding line and the outer surface of the thin cover substrate. By carefully controlling this distance, the laser processing parameters are adjusted to enable hermetic sealing without damaging the thin substrate material.
3Strength
If additional bonding materials are used to join substrates, then joining strength can be improved, but the package complexity and manufacturing process become more complicated
Solution Approach 1:
The patent removes additional bonding materials from the joining process by using a laser bonding line that directly joins the thin cover substrate to the second substrate. This extraction of unnecessary bonding materials simplifies the package structure and manufacturing process while maintaining hermetic sealing and joining strength.
Solution Approach 2:
The patent replaces mechanical bonding methods (adhesives, bonding materials) with a laser-based bonding mechanism. The laser bonding line creates a direct bond between substrates through localized heating and material fusion, eliminating the need for additional bonding materials and simplifying the overall joining system.
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 solution provides enhanced shear strength, reduced material stress, and improved dimensional stability, allowing for sensitive optical and pressure measurements while maintaining hermetic sealing, thus expanding the package's applicability to previously inaccessible fields.
Implementation Method 1
A laser bonding line joins the cover substrate and the second substrate that adjoin the cover substrate directly
Implementation Method 2
Joining processes involving lasers cannot be applied with thin substrates since material will be burned or removed if the laser is targeted too close to the surface
Implementation Method 3
the package can be designed so as to be transparent at least partially, i.e. at least in certain areas and/or at least for a range of wavelengths. This transparency furthermore provides for communication processes, for example, for data or power transfer
Data Source
AI summary
A hermetically sealed package includes: at least one cover substrate which is sheet-like and includes a flat outer surface and a circumferential narrow side, the at least one cover substrate being formed as a transparent thin film substrate, the at least one cover substrate having a thickness of less than 200 μm; a second substrate which is adjoined to the at least one cover substrate and in direct contact with the at least one cover substrate; at least one functional area enclosed by the hermetically sealed package, the at least one functional area being between the at least one cover substrate and the second substrate; and a laser bonding line which joins the at least one cover substrate and the second substrate directly and in a hermetically tight manner.