component qualification testing does not predict system level response

1. Packaging shock sensitive
electronic components
mythology
3/28/18 rev A
Don Blanchet
3B Associates
dwb3298@verizon.net

2. Myths
 Shock acceleration commonly
measured by ‘G’ units are not the
same as the ‘G’ units we feel on
carnival rides.
 Using a component qualified to a 50G
shock level does not guarantee it will
survive a system exposure to 50G
shock.

3. Groundrules for design
 Establish system level shock
requirements.
 Obtain component qualification
specifications.
 Design component mounting and
consider alternatives.
 Perform calculations of the dynamic
response of the component mounted
in the system. (done easily with FEA)

4. Scenario
 System spec ½ sine 50G , 11msec
shock pulse duration.
 Component selected was qualified to
the exact same shock input pulse.
 First rookie assumption design is o.k.
 ….Problem – depending on the
mounting and location the component
it may experience higher than the 50G
qual level at the system level.

5. Component shock spec.

6. Simple example: crystal
oscillator component

7. FEA dynamic model
component qualification
Measurement
location
Apply
Y-axis
shock

8. Single part test response

9. System Assembly
Mounting screws 4 places

10. System shock spec.

11. FEA model peak displacement
response to 50G 11 msec pulse

12. Results – peak acceleration
response on crystal oscillator
70 G’s
Circuit board Assembly damping
70/50 = 1.4 increase in component exposure

13. Conclusions
 Systems contain many degrees of
freedom when exposed to shock and
vibration excitation.
 Thinking in the basic modeling
conceptual framework – there can be
many springs, masses and dampers in
a system.
 The response of a single component in
an application must take into account
this level of complexity.