Vent Hole Air-Release Mechanism for Cavity Package Lid Stability
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Solution Overview
Problem
Conventional device packages for motion sensors face issues with stress and reliability due to thermal expansion mismatches and increased pressure within the cavity, leading to lid deformation or popping off during high-temperature processing and mounting.
Innovation Solution
Incorporating a vent hole in the package substrate allows air to escape, reducing internal pressure and preventing lid displacement by providing a pathway for air to pass in and out of the cavity during temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cavity is sealed during high-temperature processing, then environmental protection and RF shielding are improved, but internal pressure increases causing lid deformation or popping off
Solution Approach 1:
A vent hole is extracted from the package substrate to allow air escape during high-temperature processing, reducing internal cavity pressure and preventing lid deformation while maintaining the sealed cavity structure for environmental protection and RF shielding
Solution Approach 2:
The package substrate has different properties in different locations: most areas are sealed for protection, but a localized vent hole provides pressure relief. This local opening does not compromise the overall sealing quality of the cavity package
2Object-affected harmful factors
If the cavity is sealed to protect the device, then environmental protection is improved, but thermal expansion stress increases due to trapped air
Solution Approach 1:
A vent hole is extracted from the sealed cavity structure to allow thermal expansion and contraction of air, reducing thermal expansion stress on the device while maintaining environmental protection through the overall sealed configuration
Solution Approach 2:
The vent hole acts as an intermediary that allows the trapped air to adjust its volume during temperature variations, mediating between the sealed cavity requirement for protection and the need to accommodate thermal expansion
3Reliability
If a vent hole is added to release pressure, then lid deformation is prevented, but package complexity increases
Solution Approach 1:
The vent hole is integrated into the existing package substrate structure, combining the pressure relief function with the substrate's structural role. This merging approach adds minimal complexity while achieving the reliability benefit of preventing lid deformation
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 vent hole effectively mitigates the risk of lid tilt, deformation, or popping off, enhancing the bonding strength and reliability of the device package by managing pressure and stress within the cavity.
Implementation Method 1
Sealing such devices in an epoxy encapsulant or glob top may result in undesirable stress to the devices due to different coefficients of thermal expansion
Data Source
AI summary
A housing for integrated devices that includes an air-release mechanism is disclosed. This is achieved, in various embodiments, by forming a vent hole in a package substrate, and arranging a package lid over the package substrate. The vent hole allows air to be released from within the cavity package, thereby ensuring that the package lid remains stably affixed to the package substrate despite increased temperatures during processing. The vent hole may be sealed upon mounting the package onto a mounting substrate.