MECHANICAL SHOCK TESTING
Mechanical Shock is the result of suddenly applied
forces or abrupt changes in motion. Shocks of this type may
disturb operating characteristics or cause damage similar
to that resulting from excessive vibration, particularly if
the shock pulses are repetitive.
The Shock Test is intended to determine the suitability
of the devices for use in electronic equipment that are subjected
to moderately severe shocks as the result of rough handling,
transportation, or field operation.
The Shock Apparatus is a commercial piece of equipment
designed to provide the Half-Sine Shock Pulse that
is the normal test specified for electronic components and
assemblies. Typically, the device is subjected to 5 shock
pulses of the peak (g) level specified in the selected test
condition and for the pulse duration specified in each of
the orientations X1, X2, Y1, Y2, Z1 and Z2. For devices with
internal elements mounted with the major plane perpendicular
to the Y-axis, the Y1 orientation shall be defined as that
one in which the element tends to be removed from its mount.
Typical conditions are 500 g’s for 1.0 ms, and/or 1500
g’s for 0.5 ms.
Tooling is generally required to attach the component
to the Shock Apparatus. The simplest and least expensive
is to add holes to Silicon Cert’s existing adapter plates
if the component has screw attachment holes. If the component
has no such attachment means, special fixtures must be designed
and fabricated. These unique fixtures are then attached to
the adapter plates and are attached to the “I Beam”
mounting block. This unique design allows for the shock testing
of all six axes.
The tooling should allow the accelerometer to be mounted
as close as possible to the centerline of the component being
shocked. As standard practice, the new tooling will be run
dry (without test components) to calibrate the machine. In
addition, calibration is performed in all orientations before
product is run.
Various Standards use different requirements, and
are summarized below:
MIL-STD-202F for Electronic and Electrical Component
Parts
Method 213B: Half–sine waveform, 3 shocks in each of
6 axes, (D) 500 g’s for 1 ms/(E) 1000 g’s for 0.5
ms/(F) 1500 g’s for 0.5 ms. Amplitude of measured pulse
shall be within +/- 20 % of the ideal amplitude; measured
duration shall be within +/- 15 % of the specified duration.
MIL-STD-750 for Discrete Semiconductor Devices
Method 2016: Half–sine waveform; number and direction
of blows,
acceleration and duration to be specified. Amplitude of measured
pulse
shall be within +/- 20 % of the ideal amplitude; measured
duration shall be
within +/- 30 % of the specified amplitude duration.
MIL-STD-883 for Microcircuits
Method 2002: Half–sine waveform, 5 shocks in each of
6 axes, (A) 500 g’s for
1 ms/(B) 1500 g’s for 0.5 ms. Amplitude of measured
pulse shall be within +/- 20 % of the ideal amplitude; measured
duration shall be within +/- 30 % of the specified amplitude
duration. Condition B is default.
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