Static Expansion Method for Ultra-Fine Leak Calibration
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Solution Overview
Problem
Current technologies for ultra-fine leak testing, such as Kr85 leak testing and helium leak testing, face limitations in achieving reliable calibration and measuring leak rates below 10−13 Pa·m³/s, particularly for MEMS packages, due to the use of radioactive isotopes and lack of standard calibration methods, leading to unreliable extrapolation values and linearity issues in helium leak testing.
Innovation Solution
A reference leak generating device that introduces a precise reference leak of 10−11 Pa·m³/s or less through an orifice or porous plug under controlled molecular flow conditions, using a static expansion method to determine upstream pressure and calibrate a partial pressure analyzer, allowing for on-spot calibration and multipoint calibration in ultra-fine leak testing devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Kr85 leak testing is used to achieve leak testing up to 10^-13 Pa·m³/s, then measurement precision is improved, but reliability deteriorates due to use of radioactive isotopes and inability to perform mass production
Solution Approach 1:
The patent replaces the expensive and hazardous radioactive Kr85 source with a disposable, non-radioactive helium gas supply system. The helium gas can be easily replaced and does not require special safety handling, while achieving the same measurement precision through the static expansion method and calibrated orifice flow control.
Solution Approach 2:
The patent changes the measurement parameter from radioactive isotope decay detection to helium partial pressure measurement. By using the static expansion method to precisely control and measure helium gas flow through a calibrated orifice, the system achieves equivalent measurement precision without the reliability issues of radioactive materials.
2Adaptability or versatility
If helium leak testing with extrapolation values is used to achieve measurement below 10^-10 Pa·m³/s, then measurement range is extended, but reliability deteriorates due to lack of standard calibration and low reliability of extrapolation values
Solution Approach 1:
The patent performs preliminary calibration by introducing a known amount of helium gas into the measurement chamber using the static expansion method before actual leak testing. This establishes a reliable reference point for the measurement range, allowing accurate extrapolation to lower leak rates while maintaining calibration reliability.
Solution Approach 2:
The patent uses a calibrated orifice as an intermediary device to precisely control and measure helium gas flow. The orifice provides a known flow conductance that serves as a reliable reference standard, enabling accurate calibration and extending the measurement range with maintained reliability.
3Ease of operation
If one-point calibration is performed to simplify the calibration process, then ease of operation is improved, but measurement precision deteriorates due to inability to confirm linearity of measuring unit
Solution Approach 1:
The patent segments the calibration process into multiple discrete points by introducing different known amounts of helium gas through the static expansion method. This allows verification of linearity across the measurement range while maintaining operational simplicity through automated control of the expansion process.
Solution Approach 2:
The patent implements feedback by measuring the actual helium partial pressure at each calibration point and comparing it with the expected value based on the static expansion calculation. This feedback mechanism confirms linearity and allows adjustment if deviations are detected, maintaining both ease of operation and measurement precision.
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
Enables precise generation and measurement of ultra-fine leaks, achieving high reliability without the use of radioactive substances, suitable for mass production, and confirming the linearity of the partial pressure analyzer, thereby improving the accuracy and reliability of leak rate measurements.
Implementation Method 1
introduces a reference leak of 10−11 Pam3/s or less into a measurement chamber or the like through an orifice, a porous plug or the like having a molecular flow conductance C and pressure conditions to realize a molecular flow
Implementation Method 2
To precisely determine the upstream pressure p1, a static expansion method is used once or several times
Data Source
AI summary
A static expansion method is performed by expanding a volume of a testing gas from V0 to V0+V1 between a second chamber of the volume V1 which is connected to an upstream side of a measurement chamber and a first chamber of the volume V0 which is connected to an upstream side of the second chamber, wherein the first camber is in communication with the second chamber via a first valve, wherein the second chamber is in communication with the measurement chamber via each of a second valve and an orifice or porous plug, respectively. When the first valve is opened and the second valve is closed, the testing gas flows from the first chamber via the second chamber into the measurement chamber only through the orifice or porous plug.