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Negative Tare Indicator – This is a minus sign to the left of the PEAK FORCE display. This error
condition will be displayed for negative inputs which exceed 0.1% of full scale.
Computer Busy Indicator - A colon lights to the left of the PEAK FORCE display if the MP4 is
inhibited from further operation as a result of receiving the appropriate message, via the RS-232C
interface, from an external source. A printer cannot inhibit the MP4. The Computer Busy feature
prevents data from being lost before it is recorded by the data logging system.
MODE Switch - In the DESTRUCT position, force is applied until either the wire bond breaks or the
beam reaches the Upstop. The maximum peak force applied by the hook will be displayed until reset.
The MP4 is designed to detect wire bond failures that occur between 4% and 120% of full scale, as
defined in table 1-3. In the NON-DESTRUCT position, the pull force is preset, in 0.1% of full scale
increments, by using the three decade PRESET FORCE thumbwheel switches. The minimum
guaranteed PRESET FORCE is 1% of full scale or 0.5 gf, whichever is greater. As required by MIL-
STD, the peak force which is actually applied to the bond is displayed by the MP4. Under some
circumstances the peak force can exceed the PRESET FORCE as a result of excessive pull speed,
inertia, or vibration from an external source. Should a wire bond fail before reaching the PRESET
FORCE, the force at which the failure occurred will be displayed.
BEAM TRAVEL Control – This control changes the movement of the beam from ¼ to ¾ inch for full
movement of the Control Lever. The ratio of the Control Lever movement to beam movement is
variable from 4.5:1 to 13:1. Device holders with height variations up to 2 inches can be accommodated
by using the five mounting positions for the Beam Module together with the DOWNSTOP control and
BEAM TRAVEL control. This control is a screwdriver adjustment to prevent inadvertent changes.
DOWNSTOP Control – This control provides a fast, convenient method to electronically adjust the
position of the Downstop. The range of adjustment is ¾ inch when the BEAM TRAVEL control is set
to MIN and is reduced to ¼ inch when the BEAM TRAVEL control is set to MAX.
UPSTOP Control – This is a ten-turn potentiometer which changes the position of the Upstop. The
resolution is 0.001 inch per minor division on the vernier dial. The red Test Status Indicator, visible at
the test site, continuously blinks if the beam reaches the Upstop. The Upstop can be set to activate in
any position between full-scale travel and approximately 0.003 inch from the location of the Downstop.
A mechanical lock is provided to prevent inadvertent changes.
HOOK RETURN Switch - the HOOK RETURN switch is set to MANUAL for testing multilevel
substrates. In this mode, the hook will remain stationary after the completion of each test. In the Non-
Destruct Mode test, the red Test Status Indicator will go out, as a signal to the operator to lower the
hook, after the PRESET FORCE is reached and the HOLD TIME expires. The hook must be lowered to
the desired level by using the Control Lever. The hook cannot be raised until the operator actuates the
footswitch, which in turn lights the red Test Status Indicator. After a test, the footswitch is inhibited
until the applied pull force has been reduced by at least 5%, by lowering the hook. This feature prevents
the operator from accidentally subjecting a bond to multiple tests. When the HOOK RETURN switch is
set to MANUAL, the rear panel ZERO switch (see below) should be set to MAN (in the out position).
Otherwise if the operator should press the footswitch before the force on the hook is completely
removed, the force would be considered as tare and would be added to the force applied during the next
test.
990-180
®
MICROPULL
IV WIRE BOND PULL TESTER
CHAPTER 1: SYSTEM DESCRIPTION
1-11
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