Wire Bonding Plug for Hermetic MEMS Cavity Sealing
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Solution Overview
Problem
Current methods for hermetically sealing cavities in MEMS devices require high temperatures, high pressures, or special surface conditions, which are incompatible with standard microelectronic manufacturing processes and do not achieve hermetic seals at low temperatures, especially for temperature-sensitive liquids and harsh environments.
Innovation Solution
The method employs industrially available wire bonding technology to insert a plug into a hole, using a gold wire bond process that forms a ball by electrical discharge, bonds it to the substrate with force and ultrasonic energy, and shears the wire to create a hermetic seal, allowing for low-temperature sealing of cavities without the need for complex structures or additional mechanical stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wafer bonding techniques (fusion bonding, compression bonding, anodic bonding, or eutectic bonding) are used to hermetically seal cavities, then hermetic sealing is achieved, but high temperatures, high pressures, high voltage or special surface conditions are required which are incompatible with standard microelectronic manufacturing processes and temperature-sensitive liquids
Solution Approach 1:
The patent replaces thermal and electrical bonding mechanisms with a mechanical plugging system. A plug made of deformable material is inserted into the cavity opening and deformed using mechanical force to create a hermetic seal, eliminating the need for high-temperature or high-voltage processes that are incompatible with standard microelectronic manufacturing and temperature-sensitive liquids
Solution Approach 2:
The invention changes the sealing mechanism from relying on thermal/electrical parameters (temperature, voltage) to mechanical parameters (force, deformation). The plug material's deformability allows it to conform to the cavity opening under applied force, creating a hermetic seal at low temperatures compatible with standard manufacturing processes
2Reliability
If gold ring embossing or cold welding of overlapping gold sealing rings is used, then more hermetic sealing is achieved compared to adhesive wafer bonding, but additional mechanical stabilization using polymer underfills is required and the liquid must be pipetted into every cavity using a serial process
Solution Approach 1:
The invention extracts and eliminates the need for additional mechanical stabilization components (polymer underfills) by designing a plug system that inherently provides both sealing and structural stability. The deformable plug creates a mechanical interlock with the cavity opening, providing self-stabilization without requiring separate underfill layers
Solution Approach 2:
The plug serves multiple functions simultaneously: it provides hermetic sealing, mechanical stabilization, and structural support without requiring separate components. This multi-functional design simplifies the overall device structure and eliminates the need for additional polymer underfills required by gold ring embossing and cold welding methods
3Temperature
If adhesive wafer bonding is used for low temperature sealing, then compatibility with temperature-sensitive liquids is achieved, but hermetic sealing is not achieved
Solution Approach 1:
The invention uses a composite approach combining a deformable plug material with the cavity structure. The plug material is designed to be mechanically compliant and deformable, allowing it to conform to the cavity opening and create a hermetic seal through mechanical interlocking rather than adhesive bonding, achieving both low-temperature compatibility and hermetic sealing
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 fast, cost-effective, and hermetic sealing of cavities, with leak rates below the detection limit, suitable for both liquid and vacuum applications, and is compatible with standard microelectronic processes, ensuring the integrity of MEMS devices and microelectronic circuits.
Implementation Method 1
A ball is formed by an electrical discharge at the end of a wire
Implementation Method 2
bonds it to the substrate with force and ultrasonic energy
Data Source
Figure 1~1d
Figure 1e~1h
Figure 1i~1k
AI summary
A method for at least partially inserting a plug into a hole, said method comprising the steps of a) providing a at least one substrate with at least one hole wherein said at least one hole has a largest dimension of from 1 μm to 300 μm, b) providing a piece of material, wherein said piece of material has a larger dimension than said at least one hole, c) pressing said piece of material against the hole with a tool so that a plug is formed, wherein at least a part of said piece of material is pressed into said hole, d) removing the tool from the piece of material. There is further disclosed a plugged hole manufactured with the method. One advantage of an embodiment is that an industrially available wire bonding technology can be used to seal various cavities. The existing wire bonding technology makes the plugging fast and cheap.