Yaesu FT-5100, Техническое дополнение

Страница: 6 / 100

General
Replacing Chip Components
Chip components are installed at the fac­
tory 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 vacuum 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) 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 soldering by very
small dual streams of hot air (without physical
contact during soldering). We remove parts by
first removing solder using a vacuum suction
iron, which applies a light, steady vacuum 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 below 280 °C (536 °F).
1 - 4
Precautions for Chip Replacement
K
Do not disconnect a chip forcefully, or the
foil pattern may peel off the board.
K
Never re-use a chip component. Dispose of
all removed chip components immediately
to avoid mixing with new parts.
K
Limit soldering time to 3 seconds or less to
avoid damaging the component and
board.
Removing Chip Components
D Remove the solder at each joint, one joint at
a time, using solder wick whetted with non­
acidic flux as shown below. Avoid applying
pressure, and do not attempt to remove the
tinning from the chip's electrode.
D
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.
FT- 5100 Technical Supplement