10% Model Outgassing Rate Measurement

1
10 Model Outgassing Rate Measurement

• Model building status
• Setup
• Method explanation
• Throughput method w/ variable conductance
• Rate-of-rise method

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Assembly Status Shingled Substrate
3
Assembly Status Dummy Silicon

• Silicon assembly
• ROC
• Sensor
• HDI
• Almost complete

4
Assembly Status

• Substrate to be modified to fit dummy silicon
  assemblies

5
Test Setup - Chamber

• Stainless steel
• 19.5 inches ID
• 66 inches length

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Test Setup Vacuum Vessel

• 3 turbo pumps in parallel
• Total pumping speed 2550 L/sec
• Fixed rotating disk dividing chamber into 2
  volumes
• Rotating disk with different sized holes

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Test Setup Vacuum Vessel

• Volume 1 (w/ sample) 50 length
• Volume 2 16 length
• RGA

8
Test Setup Variable Conductance

• Rotate disk to different pumping speeds between
  volumes
• 2, 23, 6
• Largest A500 cm2
• Blank (no seals between disks)

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Methods to measure gas load

• Throughput method with variable conductance
• Measurements at pressures between 10-3 10-6
  torr
• Extrapolate to 10-7 torr (test cant reach this)

• Rate-of-rise method
• Cross-check measurements from throughput method

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Throughput method w/ variable conductance

• For a given orifice size
• QP1SP2Spump

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Assumptions

• Q nd na
• where Q outgassing rate
• nd desorption rate
• na adsorption rate
• Outgassing rate is dependent on chamber pressure
• Decrease pressure, decrease na, more accurate
  measure of Q

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Capability of Test Setup

• When the orifice size changes, what happens to
• P1
• ratio of sample surface area (3 m2) to effective
  area of pumping orifice (S/11.6 L/sec-cm2)

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Assumptions in Test Design

• Constant gas load of 0.01 torr-L/sec (Q is
  independent of P1)
• Outgassing rate of test chamber is negligible
• Flow through orifice is air _at_ room temperature

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Varying pumping speed
Ratio sample surface area (3m2) effective
area of pumping orifice
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Rate-of-Rise Method

• Different than previous rate-of-rise test
• Use same test chamber
• Use largest orifice
• P1 settles at steady-state condition
• Then, change to blank position
• Long settling time
• Measure outgassing rate at beginning of transient
• Use as a cross-check for throughput method