TM 11-5820-922-40-1
4.
3.
Feed rosin-cored solder to the
On the reverse side of the board,
pad-eyelet junction. When the solder
trim the lead as flush as possible.
flows, follow the flow around the eye-
5.
let with the solder until the entire
The opposite side of the board
need not be soldered if the entire inner
joint is covered. Remove the iron
surface of the hole has been soldered.
immediately. Use as small an amount of
solder as is practical and still cover
6.
the entire joint.
Repeat steps 2 thru 5 for each
lead on the component.
4.
Allow the soldered joint to cool
7.
Encapsulate the component by the
at least 5 seconds without disturbing
method described in paragraph 3-33.
the joint, as any disturbance during
solidification may cause a fracture or a
cold-solder joint.
REPAIR OF POLYURETHANE CONFORMAL
COATING. The polyurethane conformal
coating seals (encapsulates) the circuit
5.
On the reverse side of the cir-
card and components from moisture and
cuit card, trim the lead as flush as
dust. The coating should not be relied
possible.
upon to impart mechanical strength for
handling. Discontinuities in the poly-
6.
Repeat steps 2 thru 4 for each
urethane conformal coating, such as
lead on the component.
holes caused by test probes, areas
scraped for component replacement or
7.
Encapsulate the component using
etch repair, burned areas caused by the
the method described in paragraph 3-33.
soldering iron , and discontinuities
caused by an uncoated replacement com-
3-32. COMPONENT REPLACEMENT IN PLATED-
ponent itself may be repaired by per-
THROUGH HOLES. Components may be
forming the following steps.
replaced in plated-through holes by
performing the following steps.
WARNING
NOTE
Solvents used in this procedure
are flammable and must be kept
See paragraph 3-30 for compo-
from open flame, heat, and
nent clearance requirements.
sparks. Keep containers tightly
closed and store them in a cool
1.
Make certain that all the poly-
place when not being used. The
urethane coating has been removed from
solvent must be used only in an
the pads on both sides of the circuit
adequately ventilated environ-
card.
ment. Avoid breathing vapors
and repeated contact with skin.
2.
Apply the well-tinned tip of the
Clean hands thoroughly before
soldering iron as close as possible to
smoking, eating, or drinking.
the component lead-pad junction.
3.
Feed rosin-cored solder to the
1. Prepare a mixture of polyurethane
component lead-pad junction opposite the
conformal coating by following the manu-
soldering tip. When the solder flows,
facturer's instructions. Solvent may be
follow the flow around the component
added as required.
lead-pad junction with the solder until
the entire joint is covered. Remove the
2.
Apply a thin, smooth, uniform
iron immediately. Use as small an
coating with a small brush (1/2 inch) to
amount as is practical and still cover
all areas requiring coverage.
the entire joint.
