______________________________________________
HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
203
2.
Procedure:
a.
Make sure you are ESD safe through the entire procedure.
b.
Take the FET to be installed and make sure the back side is clean.
Make sure that the heat sink mounting surface is clean as well. If the
surfaces are not clean, clean them with a Q-tip dipped in cleaning
solvent. Make sure solvent is dry before proceeding.
c.
Use the Xacto knife (blade #11). Only use a clean, fresh blade (this
blade should only be used for this procedure). Measure out a small
amount (1-2mm from the tip of the syringe) of compound from the
dispensing syringe onto the Xacto blade.
d.
Apply the compound evenly on the FET by moving the flat side of
the blade in a circular motion on the back side of the FET. Clean
excess compound off the blade.
e.
Holding the Xacto blade at a 45 degree angle or less from the FETs
surface, gently press down with the blade edge.
f.
Continuing to hold the blade at 45 degrees or less, and starting at one
end of the FET, sweep slowly across the FET. Made sure the blade
does not lift up. There should be a thin opaque film left on the surface
after sweeping. The gold flashed back of the FET is slightly
concave, the heat sink compound should be thickest in the center.
There should be excess heat sink compound on the blade. Carefully
wipe the excess compound off on a clean cloth (do NOT try to re-use
this compound).
g.
Place FET firmly into the holes of the PC board. Try to pull the FET
up, applying moderate force. If the FET resists being pulled up, it is
well seated. If it is easily pulled up, clean both surfaces, inspect for
surface irregularities, and try again.
h.
Install spacer, levelers and leaf spring. Insure that leaf spring and
levelers are centered over the FET packages and that the spacer is
resting flush with the heatsink. Tighten the screw securely. The leaf
spring should bottom out on the spacer and the split washer should
be fully compressed.
i.
Solder the leads using low-temperature solder. Inspect for solder
bridges. Scrape away any flux using a small knife. Do not use any
sprays or liquids that may run under the transistor and dissolve the
heatsink compound. Inspect for proper flow of solder between the
FET leads and the board foil.