Yaesu FT-2500M Technical Supplement page 6

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Chip
Component
Information
Replacing Chip
Comp
onents
Chip components
are
installed
at
the factory
by
a series
of robots. The first one
places a
spot
of
adhesive
resin at the location where
each
part
is to be installed, and later robots handle
and place parts using vacutun suction.
For single-sided boards, solder paste is ap-
plied and the board is then baked to harden the
resin and
flow
the
solder.
For
double-sided
boards, no solder paste
is
applied,
but
the
board
is
baked (or exposed to ultra-violet
light)
to cure the resin before
dip
soldering.
In our
laboratories and service shops, small
quantities
of chip
components are mounted
manually by applying
a spot
of resin, placing
them
with
tweezers, and
then soldering by
very
small
dual
streams
of hot air
(without
physical contact during soldering).
We
remove
parts by
first removing
solder using
a
vacuurn
suction iron, which applies
a
light,
steady vac-
uum at the iron tip, and
then breaking the
adhesive
with
tweezers.
The special vacuum
soldering/desoldering
equipment
is
recommended if you expect to do
a lot of chip
replacements. Otherwise,
it
is
usually possible
to
remove and replace chip
components
with
only
a
tapered, temperature-
controlled soldering iron,
a set
of tweezers and
braided copper solder wick. Soldering iron
temperature should be less than
280'C
(536
"F).
Precautions
for
Chip Replacement
X Do not disconnect
a
chip forcefully, or the
foil pattern
may peel off the board.
X Never re-use
a
chip component. Dispose of
all removed chip components immediately
to avoid mixing with new
parts.
X
Limit
soldering time to
3 seconds
or
less
to
avoid damaging the component and board.
Remouing Chrp
Comp
onents
3
Remove the solder at
each
joint,
one
joint
at
a
time, using solder
wick
whetted with
non-acidic flux
as
shown below.
Avoid
ap-
plying
pressure, and do not attempt to re-
move the
tinning from
the
chip's
electrode.
Grasp the chip
on
both
sides
with
tweezers,
and gently
twist
the tweezers back and
forth
(to break the
adhesive
bond) while
alternately heating
each
electrode.
Be care-
ful
to avoid peeling the
foil
traces
from
the
board. Dispose of the chip when removed.
D
After removing the chip, use the copper
braid and soldering iron
to
which away any
excess
solder and smooth the land
for
in-
stallation of the replacement part.
tr
1-4
FT-2500M
Technical Supplement