6.1 Hot air level the pads. In most
instances, sufficient solder will remain on the pads
to attach a new chip; but the surface may be rough,
uneven, or have solder "icicles", making
accurate placement of a new chip impossible. To hot
air level, Locate the circuit board (still in the
Board Holder) under the nozzle, with the component
removed, depress the foot pedal to begin the heating
cycle. It is recommended to add a little more flux to
the contact area to ensure thorough wetting,
don’t worry about flux residue as a cleaning
process 6.3 will remove residues. The GREEN display
will begin counting DOWN to zero. The solder will
melt and become smooth; the solder should cover the
pad(s) completely, with a slightly rounded
"pillow" shape.
6.2 Remove the board and board
holder assembly from beneath the Chipmaster nozzle
(depress cylinder, slide holder and board out). Let
the board cool to ambient temperature.
Using the Cleaning Fluid Pad Prep
Pen from the SMT Tool Kit, release sufficient fluid
by, depressing the valve at the tip to soak the area
and using the cleaning tip proceed to clean entire
contact and surrounding area, using an Antistatic
wipe 8200-1500 to finally remove all traces of
contamination and old material.
6.4 If there is insufficient solder
to cover the contact pad(s), add solder using wire
solder or solder paste and a soldering iron. Apply
no-clean paste flux to aid wetting and clean
afterwards with Pad Prep Cleaner as 6.3.
Now that the contact pads are
coplanar and free of all residues and contaminates,
apply a thin line of no-clean paste flux
(0.025") around all contacts and with the double
sided "clean and flux" brush supplied in
the SMT Tool Kit, use the softer and longer flux
brush end to brush the flux from outside the contacts
to the center, ensure all contacts are adequately
fluxed, it’s important that too much flux is not
applied otherwise the component will float off
position during reflow.
Now, take a new component, (the
removed component may be reinstalled if required,
providing leads are coplanar), and holding the center
of the component between thumb and forefinger of the
right hand and with clear view of the entire left
hand side and half view of the top and bottom of the
component, place the component, aligning the Y axis
(left side) and then gently aligning top and bottom
half sides.
A small hand 2.3 dioptic magnifier
8200-1200 held in the left hand easily provides all
the vision needed to align. Once the component is in
place gently release the chip out and away to the
right, the flux will support the component. Probes
supplied in the SMT Tool Kit will aid fine alignment
or the entire alignment procedure dependent upon
personal preference. Aligning one full side and two
halves should align all four sides but each lead must
be exactly centered over the contact pads. The
no-clean paste flux will hold the component in place
during reflow (melting) of the solder. This flux will
dissipate, however, by the completion of the heating
cycle. The component corners may be tagged with a
soldering iron for extra support prior to reflow, if
so desired.
6.7 Place the board under the
nozzle of the Chipmaster, being careful to center the
component under the nozzle as accurately as possible.
Press the INDEX key on the
Chipmaster controller ONCE, and verify the eutectic
(Removal) time, now add twenty (20) seconds to this
eutectic time to provide sufficient time to reflow
the entire component. Use the UP arrows as described
previously and press ENTER to save the change. Press
the INDEX key FOUR times to return to the
"Operator View Display".
Depress the foot pedal to begin the
heating cycle, (Illustration # 7). When the timer
reaches zero, the reflow is complete, wait for the
solder, component and board to cool remove the Board
Holder and inspect your work.
