Unitek 6-099-04, Operation And Maintenance Manual

Page: 36 / 88

CHAPTER 3: OPERATING INSTRUCTIONS
MICROPULL
®
IV WIRE BOND PULL TESTER
3-8 990-180
15 Increase the UPSTOP control until the MP4 functions properly. Verify that the MODE switch is set to
NON-DESTRUCT and the HOOK RETURN switch to MANUAL. Hook a wire bond. Then decrease
the UPSTOP control until the Test Status Indicator just starts to blink and a force equal to the PRESET
FORCE is displayed on the PEAK FORCE indicator. This is a trial and error process requiring several
cycles. Now the Upstop is located at a point corresponding to the top of the non-destructively stressed
wire bond. Every minor division on the UPSTOP control vernier represents 0.001 inch. If loop height
is critical in your devices, increase the UPSTOP control by 2 to 10 minor divisions and use the control
to detect excessive loop height. Otherwise, set the UPSTOP control to a setting which is greater than
the loop height but less than, or equal to, the setting previously recorded in step 13.
NOTES:
x
The distance between the the Downstop and the Upstop must exceed .003 inch.
x
The MIL-STD states that the NON-DESTRUCT pull should be made in the center of the wire bond
and that the wire bond should be reformed into an equilateral triangle, as shown in figure 1-3. This
requirement means that the hook must either face the MP4, or the operator, and the bond must be
oriented parallel to the front of the MP4.
16 Set the MODE switch to NON-DESTRUCT /and the HOOK RETURN switch to AUTO. Make Non-
Destruct tests at successively lower force settings until the footswitch fails to reset the cycle. This
setting plus one least significant digit, represents the lowest Non-Destruct force that should be preset (on
the PRESET thumb-wheels) for this beam. This value should be 0.10 gf (010) for the 10 gf beam; 1.5 gf
(015) for the 100 gf beam and 100 gf (100) for the 1000 gf beam.
NOTE: Proper operation of the failure detection electronics is not guaranteed below 2% of full scale force.
Example of Destructive Mode Testing
1 Set the MODE switch to DESTRUCT /and the HOOK RETURN switch to MANUAL.
2 With the Control Lever in the up position, turn the UPSTOP control CCW until the red Test Status
Indicator just blinks. The Upstop is now set to the position that corresponds to the highest position of
the beam arm as determined by the beam travel adjustment. This should be between 1/4-inch and 3/4-
inch above the device substrate.
3 Position the hook under the center of the wire bond.
4 Press the footswitch. Force will be applied to the bond until it breaks or the beam hits the Upstop. The
peak force required to break the wire bond will be displayed on the PEAK FORCE indicator. The Test
Status Indicator remains lit. A blinking Test Status Indicator indicates that the beam hit the Upstop.
NOTE:
Beams can be used at forces up to 20% over their nominal rating. That is, 12 gf, 120 gf, and 1200
gf for the 10gf, 100gf and 1000gf Beam, respectively.
5 Place the MODE switch to DESTRUCT /and the HOOK RETURN switch to AUTO.
6 Repeat the previous test on another wire bond. Notice that when the hook automatically returns, it
occasionally rests on top of the broken wire bond. For this reason you may wish to perform Destruct
Tests with the HOOK RETURN set to MANUAL.