miniaturized microwave circuits assumed to be beyond the frequency range of vibration testing are in fact susceptible to damage induced by hammer blows used in HALT/HASS equipment

1. Mechanical resonances in
microwave integrated circuits
and packages
Above 2000 hz who cares ??
9/14/2016
Don Blanchet
3B Associates
dwb3298@verizon.net

2. Known
 From inception 1930’s-40’s vibration
testing is limited over the range of
10hz to 2000hz.
 At 2000hz and above the response
displacements are very small as well
as component stresses.
 Small Parts with high resonant
frequencies rarely experience any
fatigue failures.

3. Known (con.)
 Electronics design has evolved from
thru-hole mounting to much smaller
surface mount technology
 Microwave electronic circuits can
experience signal noise due to
vibration and shock excitation.
 Microwave integrated circuit
components are very small and exhibit
very high mechanical resonant
frequencies.

4. Known (con.)
 If testing rarely exceeds 2000hz where
is the source of the mechanical noise ?
– Severe shock events
 Gunfire
 Missile steering pulse rocket motors
 Missile stage separation
 Repetitive hammer blows such as those
in HALT/HASS 6 degree of freedom
quality control test machines.
Shock pulse

5. Problems
 Design of HALT/HASS machines
include digital control that treats the
repetitive shock as random “vibration”.
 The output control loop filters above
2500 hz and calculates a Grms
response to display to the test
engineer.
 This is falsely represented as random
vibration to manufacturing and quality
test engineers.

6. Potential Problem for
microwave designers
 Repetitive hammer blows do contain high
frequency components.
 The machine control loop can’t undo a
hammer blow !
 Repetitive strikes tend to be additive and
“ring up” the high frequency input to the
test fixture and unit under test.
 Significant electrical noise and possible
fatigue damage can be expected over the
duration (hours) of these lengthy 6 dof
tests.

8. Measurements from
HALT/HASS vibration
testing
evidence of shock pulse
components > >2000 hz
References from COTS Journal

9. Halt test statistical analysis
many strikes above 3 sigma a
poorly controlled test

10. Significant number
of high G measurements
In the HIGH FREQUENCY
Range > 2000hz ,
Up to 100 Khz !
measured on
a 6 dof HALT
hammer blow machine.

11. High frequency excitation
from hammer blows
PSD
Shock pulses

12. Random excitation above 2Khz
measured on HALT fixture!

13. HALT machine also known as 6
degree of freedom test is
capable out to 20Khz !
Air driven hammers

14. COTS Journal June 2009
measurement out to 10khz

15. Solidworks Simulation
Advanced Dynamics

16. FEA of sample small
Microwave components
 Determine resonant frequency
 Sine sweep characterization 5-35000 hz
 Wideband random “vibration” hammer
blows

17. Case #1
Covered header package
Formed lid

18. Model
formed lid
f1= 7100 hz
Resonant
Frequency
From FEA
Lid oil can
Mode

19. Cover 1g sine sweep
Q=14.5 @ 7100 hz

20. Cover sine sweep
displacement at cover center

21. Cover response to HALT
machine hammer blows input
at 15 g rms
6 sigma displacement = 3.0 e-04 inches

22. Case #2
Gold ribbon bond wire

23. model
.002 x .012 x 0.23
f1 = 5300 hz

24. Ribbon 1g sine sweep
Q=107 @ 5300 hz

25. Other susceptible components

26. VCO circuit

27. T-pack amplifier

28. MIC mixer brick

29. Laser welded
hermetic cover
Thin aluminum seal cover
thickness = .020 inch

30. Semi-rigid coaxial cable

31. Conclusions
 Multiple references have shown that
there is significant excitation > 2000hz
in 6 degree of freedom HALT/HASS
machines using repetitive hammer
blows.
 Mechanical resonances of small
components such as those found in
microwave integrated circuits do exist.
 These resonances can induce electrical
signal noise and potentially metal
fatigue fracture.

32. Opinion
 Micro electronic surface mount
assemblies and high frequency
assemblies should be screened for
defects at the board level using
traditional well controlled
electrodynamic shakers.