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VXR-5000
Replacing
Chip
Components
Chip components are installed at the fac-
tory by a series of robots. The first
one
places
a spot of adhesive resi:tl
at the
location
where
each part is to b-= installed, and later robots
handle and place parts using vacuum suc-
tion.
For
single-sided boards, solder
paste
is ap-
plied to 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
UV
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
with
tweezers,
and then
solder-
ing by very small dual
streams of
hot
air
(without
physical
contact
during soldering).
We remove the parts by first removing solder
using a
vacuum
suction
iron,
which applies a
light, steady
vacuu
m
at
the iron
tip,
and then
breaking the adhesive
w ith
tweezers.
The special vacuum soldering/ de-solder-
ing equipment is recommended if
you
expect
to do a lot of chip replacements. Otherwise, it
is usually possible
to
remove and
replace
chip
ccmponents
with
only
a
tapered,
tempera-
ture controlled soldering iron, a set
of
tweez-
ers and braided copper solder wick.
Soldering iron
temperature sh
ould
be
below
280°C (536°F).
5-2
Precautions
for
Chip
Replacement
K
Do not disconnect a chip forcefully, or tne
foil
pattern may
peel off the board.
K
Never re-use a chip component.
Dispose
of
all
removed chip
components immedi-
ately
to
avoid
mixing
with
new parts.
K
Limit soldering
time
to 3 seconc.s oL'
less to
avoid damaging
the comp
cnent and
board.
Removing
Chip
Components
o
Remove
the
solder
at
each
joint,
one
joint
at
a
time,
usin
g
solder
wick wetted with
non-acidic
flux
as
shown
below.
Avoid
ap-
plying p ressure,
and
do not
attempt
to re-
move
the
tinning
from the
chip's electrode.
o
Grasp
the
chip
on both sides
with
tweez-
ers,
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 w
hen removed.
o
After
removing the chip, use the copper
braid and soldering iron to wick away any
excess solder and smooth the land for in-
stallation of
the
replacement part.
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