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Measurements of true leak rates of MEMS packages.

Han B - Sensors (Basel) (2012)

Bottom Line: Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages.In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion).In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.

View Article: PubMed Central - PubMed

Affiliation: CALCE Electronic Products and Systems Center, Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA. bthan@umd.edu

ABSTRACT
Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages. In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion). In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.

No MeSH data available.


Schematic diagram of the geometry of 1-D axisymmetric case (the top and bottom surfaces are adiabatic).
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f3-sensors-12-03082: Schematic diagram of the geometry of 1-D axisymmetric case (the top and bottom surfaces are adiabatic).

Mentions: An axisymmetric model is formulated to illustrate the transient boundary conditions. Its normalized form will be utilized later for an extensive parametric study. A schematic diagram of the axisymmetric model is illustrated in Figure 3. The axisymmetric form of Equation (8) can be expressed as:(9)∂p∂t=D∇2 pand the boundary and initial conditions are:(10)p(ro, t)=pa,  p(ri, t)=pc, and p(r,0)=0where pa and pc are the ambient and cavity pressure, respectively. The cavity pressure change during each time step (Δt) can be calculated as:(11)pc(t+Δt)=pc (t)−Ai R0 TMVc∫ΔtJr=ri (t)dtwhere Ai is the inner surface area (= 2πrih), M is the gas molar mass (kg/mol) and Vc is the cavity volume .


Measurements of true leak rates of MEMS packages.

Han B - Sensors (Basel) (2012)

Schematic diagram of the geometry of 1-D axisymmetric case (the top and bottom surfaces are adiabatic).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376579&req=5

f3-sensors-12-03082: Schematic diagram of the geometry of 1-D axisymmetric case (the top and bottom surfaces are adiabatic).
Mentions: An axisymmetric model is formulated to illustrate the transient boundary conditions. Its normalized form will be utilized later for an extensive parametric study. A schematic diagram of the axisymmetric model is illustrated in Figure 3. The axisymmetric form of Equation (8) can be expressed as:(9)∂p∂t=D∇2 pand the boundary and initial conditions are:(10)p(ro, t)=pa,  p(ri, t)=pc, and p(r,0)=0where pa and pc are the ambient and cavity pressure, respectively. The cavity pressure change during each time step (Δt) can be calculated as:(11)pc(t+Δt)=pc (t)−Ai R0 TMVc∫ΔtJr=ri (t)dtwhere Ai is the inner surface area (= 2πrih), M is the gas molar mass (kg/mol) and Vc is the cavity volume .

Bottom Line: Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages.In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion).In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.

View Article: PubMed Central - PubMed

Affiliation: CALCE Electronic Products and Systems Center, Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA. bthan@umd.edu

ABSTRACT
Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages. In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion). In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.

No MeSH data available.