optical leak testing technology - norcom systems inc · cumulative helium leak detection ... and...
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Optical Leak Testing Technology
October 9th, 2014
Hermetic Leak Test Methods Helium Mass Spectrometry (Fine) Bubble Leak testing (Gross) Dye Penetrant (Gross) (Destructive) Residual Gas Analysis (Destructive) Cumulative Helium Leak Detection ( Fine and Non-Batch Gross) Optical Leak Testing ( Fine and Gross Batch Testing)
Historic Limitations and Technical Issues Conventional HMS, and Bubble Leak Testing
Helium absorption on the package body High bomb pressures and long cycle times One way leakers “Virtual leakers” Inability to test at the board level Repeatable leak rate test coverage in the 10-05 cc- atm/sec range Problems with helium backfills Product contamination and masking of fine leaks during bubble testing Costs of flourinert , and environmental concerns
using perfluorocarbon with bubble leak testing
Range of Leak Sensitivity (Component Level)
Bubble Helium Optical Leak Test
True Leak Rate (deceasing )
Gross Leak -6 Fine Leak
Only Optical Leak Testing covers the full required test range in one method.
Optical Leak Testing Features
Simultaneous gross and fine leak inspection on up to 200 devices in a single test Shortened test cycles (eliminates He bombing) Quantitative results in cc-atm/second, He Can test PC board mounted devices One-step calibration and setup High volume production testing Results can be networked for SPC or to a pick and place machine to remove rejected devices.
Component Testing Butterflies Pacemakers Display Devices Frequency Control
Quartz Crystals Hybrids
Fiber Optics Custom TO Styles Power Devices
Sources of Leaks in Packages
Along the weld
At the glass to metal feedthrough
Or through a defect in the package itself
Optical Leak Testing
Test Procedure
Start Test
Package Lid is Flat
End Test
Gross or Open
Fine Leaker
Hermetic Sealed
No Change
Lid Moves Up
Chamber Pressure Deforms Lid
Optical Leak Testing Schematic Diagram
Laser Interferometer Phase Maps
Hermetic: only one
fringe
Gross: no fringes.
No lid movement.
Fail: Many fringes indicate lid moving up.
1 fringe = 0.26 um = ½ wavelength of light
Example of Leaking Device and Relative Lid Deflection
Optical Leak Testing
Fine Leak Testing
True Leak Rate Measurement Achieved by:
• Determining lid deflection (um) due leak in
the package.
• Modulating the chamber pressure sinusoidally to determine lid stiffness (um/psi).
• Lid Stiffness: um/psi
• Modulate the chamber pressure
sinusoidally to determine lid stiffness.
60.1 psig 60.0 psig 59.9 psig
Test Pressure
Start End of test
• Leakage is change in package pressure.
• Leakage= Lid movement (um) Lid stiffness (um/psi) • Leak Rate = - Ln Delta P final V Delta P initial t • Volume (cc) is free air volume. • t (sec) test time in seconds. • Delta P initial = test pressure. • Delta P final = test pressure – leakage.
• The measured leak rate is converted to a
standard leak rate by dividing by the chamber pressure.
• Leak Rate (standard) = Leak Rate (measured)
Test Pressure (atm) • The output from the Optical Leak Tester
is a true leak rate (cc-atm / sec) which is called “L” in MIL-STD-883.
• OLT can test to the ‘11’s Lair or ‘14’s R1 • Recent test on wafer level device.
• 24 hours, 64 psig, 0.01 cc, • stiffness -0.05 um/psi. • Lhe = 1.04 x 10-10 cc-atm/sec (actual) • Lair = 3.87 x 10-11 cc-atm/sec (calculated) • R1 = 3.93 x 10-14 cc-atm/sec (calculated)
• OLT can match the test sensitivity or any leak test method available including Krypton 85.
System Operation
Testing a full matrix of pig tailed butterfly packages.
Butterfly devices in process tray
Operator places tray into system
Operator Chooses the Appropriate Part number
The operator then presses Start
Automatic Test Analysis with a set Accept/Reject threshold shows 6 leaking and 4 hermetic packages.
Test Results
Optical Leak Test Systems
Collected on production parts from Vectron International, Hudson NH beginning in Jan 2003
Three different package volumes/styles and four different machines
Over 110,000 parts tested, only a very small percentage of parts failed and were confirmed by conventional HMS and bubble test per TM 1014
During Beta site testing the parts were tested to equivalent air leak rate below 1EE-08 cc/sec air.
Beta Site Production Test Data
Volume .03cc 5 mil thick kovar lid (7.5 X 7.5 mm) 50 psi chamber pressure, 4 minute test Test Sensitivity level set at 7.4 X10-09 cc/sec LHe Equivalent to 2.7X10-09 cc/sec AIR
Package Details (XTAL Oscillators)
Volume .1cc 5 mil thick kovar lid (7X14mm) lid stiffness 1 μm/psi 25 PSI chamber pressure, 4 minute test Test Sensitivity level set at 9.8 X10-08 cc/sec LHe Equivalent to 3.7X10-08 cc/sec AIR
Package Details (XTAL Oscillators)
Source: Vectron Qual Data
X-Tal PKG A: # Tested TM 1014 Rejects OLT Rejects (gross/fine) Machine #1 3106 12 12 Machine #3 2582 20 19 X-Tal PKG B: Machine #1 892 0 0 Machine #3 892 0 0 Totals 7742 32 31 Bottom Line: .01% of total parts tested (only one in 7742) passed using OLT but failed TM 1014
Machine Qualification Test Data
Testing Board Mounted Devices
Discrete hermetic devices that pass MIL STD 883 helium testing may fail during or after board assembly due to helium absorption. Because Optical Leak Testing is not subject to gas absorption issues, devices on assembled circuit cards can be leak tested with OLT.
Optical Leak Testing History MIL-STD-883
• Included into MIL-Std-883 Method 1014 in 1995. • Updated in 2004 for Gross and Fine leak testing on
both individual, components and board level testing. • The system outputs true leak rate instead of lid
deflection. • Leaking devices samples are no longer needed for
calibration. • Revision J draft has been submitted to DSCC (DLA)
in May of 2012. • Failure criteria and test methodology is better defined.
Optical leak testing using advanced laser interferometry technology
Tests for Gross and Fine leaks in one test No Helium bombing required No Helium absorption problems Eliminates bubble leak testing for gross leaks Used in production in the following industries:
MEMS, communications, micro-electronics, automotive and aerospace devices and sensors, implantable medical electronics.
Mature technology with a proven track record. (Over 100 systems installed worldwide)
