Conformal Coating Application, Circuit Side

TM 11-5820-695-35

(5) Place repaired board under an ultraviolet

(2) Assemble parts on the printed wiring

light and verify that all dirt or other foreign matter has

board making certain that all leads are bent and cut

been removed.

short. Solder parts installed on board.

(6) Vacuum bake the printed wiring board at

WARNING

a temperature of 180F. for four hours.

All cleaning operations must be done

(7) After baking mask all areas of the printed

under a hood which is ventilated to

wiring board which do not require conformal coating.

the outside.

Protective clothing,

(8) Vacuum clean the printed wiring board

rubber gloves and eye protection

immediately prior to conformal coating application (c

must be worn. Avoid breathing the

below).

vapors and avoid skin contact with

resin or catalyst.

b. Conformal Coating Preparation. To insure that

the characteristics of a minimum weight of 100 grams of

(3) Using a medium stiff nylon brush clean

polyurethane is maintained during preparation of the

the repaired area on the printed wiring board using

coating mixture, preparations should be maintained in

Freon TMC solution. Remove all extraneous materials

accordance with the following chart.

such as solder flux, dust, dirt, or fingerprints.

(4) Using a forced drying method, remove all

traces of solvent or moisture.

Polyurethane

Mfr.

Components

Pot life

Parts by

type

weight

PUR

Hysol Corp.

Part A

1 1/2 Hrs.

100

PC-26M

Part B

-------------------------------- ---- 36

PC-29M

Part A

6 Hrs. -------------------------- 100

Part B

-------------------------------- ---- 60

Conap Inc.

Part A

6 Hrs. -------------------------- 100

Part B

-------------------------------- ---- 70

Essex Chemical

Part A

8 Hrs. -------------------------- 100

Part B

-------------------------------- ---- 39

Notes

1. Polyurethane (Part A) must be stored at the temperature specified by the manufacturer. The material

should be free of any film, cloudiness, crystals, or lumps. If the material exhibits any evidence of deterioration,

it should be discarded.

2. Catalyst (Part B) must be stored at the temperature specified by the manufacturer. If the material

exhibits any evidence of deterioration, it should be discarded.

(1) Pot life Is the usable time of the mixture during which viscosity still allow application to the printed

wiring board.

(2) Weight the larger quantity, Part A first, and then add Part B, using a tongue depressor, thoroughly

mix part B into part A.

(3) Place coating solution on a clean air bench and using a stir-master, stir for 16 minutes; then, allow

16 minutes for solvent gal to leave the solution.

c. Conformal Coating Application, Circuit Side.

(2) Place board on a clean surface with circuit

side up.

(1) Coating may be applied by brushing or

spraying. If the spraying method is used, a Zicon Corp.

(3) Application of the coating requires that the

closed system or equivalent should be used.

applier have some degree of skill to assure that a

thorough coverage and uniformity of the coating is

NOTE

maintained.

The Zicon Corporation equipment

permits spraying of solventless

(4) Two or three successive layers of coating

100% solid materials. The coating is

may be required to minimize the possibility of pinholes

atomized by a superheated solvent

(which could provide a path for ingress of moisture).

under high about .003 to .050 inches

to be applied by continuous

NOTE

spraying.

To maintain a constant level of the

WARNING

thickness at all times, viscosity of

All spraying operations must be

the coating must be monitored and

performed in a well ventilated area.

closely maintained by gradual

addition of solvents.

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