Laser Sealing of Membrane Vent Holes With Controlled Solidification
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Solution Overview
Problem
The formation of surface asperity during laser sealing of membrane vent holes in inertial measurement units (IMUs) due to complex process physics like Marangoni flow and silicon phase changes can damage the device quality.
Innovation Solution
A method involving a main pulse followed by one or more supplemental pulses with controlled power profiles and durations to form a seal with reduced surface asperity, utilizing computational fluid dynamics (CFD) modeling and multi-physics simulations to optimize laser irradiation parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pulse laser irradiation technique is used to seal the vent hole, then the seal zone is formed to capture critical sensor cavity pressures, but surface asperity forms rough edges on the seal zone surface
Solution Approach 1:
The laser pulse is divided into multiple segments: a main pulse for initial sealing and multiple supplemental pulses applied at different times. This segmentation allows control over the solidification process - the main pulse creates the seal while subsequent supplemental pulses modify the surface topology by controlling cooling rates, thereby reducing surface asperity while maintaining seal integrity
Solution Approach 2:
The main laser pulse is applied first to create the seal zone and melt the silicon membrane. This preliminary action establishes the seal structure before the supplemental pulses are applied. The supplemental pulses then perform the secondary function of modifying surface asperity by controlling the solidification cooling rate, ensuring the seal is already formed before surface refinement begins
2Productivity
If the main pulse is applied to form the seal, then the vent hole is sealed, but complicated process physics like Marangoni flow and silicon phase changes affect seal zone quality
Solution Approach 1:
The method uses computational fluid dynamics (CFD) modeling and multi-physics simulations to model Marangoni flow and silicon phase changes during laser irradiation. This feedback mechanism allows optimization of laser parameters (power, pulse duration, wavelength) to control the complex physics processes, ensuring high seal zone quality while maintaining rapid sealing speed
Solution Approach 2:
The invention changes multiple laser parameters including power level, pulse duration, and wavelength to control the solidification cooling rate. By adjusting these parameters, the complex physics processes (Marangoni flow, phase changes) are managed to produce desired seal zone quality with minimal surface asperity while maintaining high productivity
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
Reduces surface asperity by controlling the solidification cooling rate, resulting in improved seal quality and device integrity.
Implementation Method 1
applying a main pulse from a main laser to the membrane vent hole
Implementation Method 2
the silicon phase changes
Implementation Method 3
the one or more supplemental pulses may include a first supplemental pulse, a second supplemental pulse, a third supplemental pulse, and a fourth supplemental pulse... form a seal over the membrane vent hole. The seal includes a seal surface having a controlled surface asperity characteristic
Implementation Method 4
the seal zone quality can be significantly affected by complicated process physics, such as Marangoni flow and/or silicon phase changes
Data Source
AI summary
A method for controlling surface asperity during laser sealing of a membrane vent hole. The method includes applying a main pulse from a main laser to the membrane vent hole at a first time. The main pulse has a main pulse cross-sectional shape, a main pulse power profile, and a main pulse duration. The method further includes applying one or more supplemental pulses from one or more supplemental lasers to the membrane vent hole at a second time later than the first time. The one or more supplemental pulses have supplemental pulse cross-sectional shape(s), supplemental pulse power profile(s), and supplemental pulse duration(s). The first and second applying steps form a seal over the membrane vent hole. The seal includes a seal surface having a controlled surface asperity characteristic.