Nonformal Coating with 1B31 (Humiseal)

TM 11-6125-259-30

Table 3-4 Cross Reference To Module/Component Assemblies

Needing Repair Materials-Continued

MODULE/COMPONENT ASSEMBLY

REPA1R PROCEDURE AND COMPONENT PARTS

POWER CAPACITORS AND DRIVER MODULE A4 (fig. 3-13)

Resistors R424 and R425 are secured with a fillet of Epocast

202 (101 parts of 202).

Plate SP04B-112B24 is secured across transformer T402

core with Eocast 202 (100 parts of 202).

COMPONENT ASSEMBLY A4A1 (fig. 3-14)

a. Transistors, Q400 through Q411 are secured with Epocast

202 (100 parts of 202).

A4A1 is conformal coated with 1B31 (Humiseal), both sides.

COMPONENT ASSEMBLY A4A1 (fig. 3-16)

Capacitors C51l and C513 are secured with a fillet of

Epocast 202 (100 parts of 202).

b. A5A1 is conformal coated with 1B31 (Humiseal).

LOGIC COMPONENT ASSEMBLY A6 (fig. 3-17)

A6 component assembly is conformal coated with 1B31

(Humiseal), both sides.

BOOST REGULATOR COMPONENT ASSEMBLY A7

A7 component assembly is conformal coated with 1B31

(Humiseal), both sides.

the above is evident, perform repair procedure

3-17. Nonformal Coating with 1B31 (Humiseal)

again.

The following procedure shall apply to the

g. After all areas are repaired, the board can be

replacement of a comformal coated component

reinstalled in its permanent position.

mounted on either a module or component

assembly.

3-18. Use of Epocast 202

WARNING

To accomplish repair of the components which are

Do not use 1B31 and Tuluol/Toluene in

held with Epocast 202, proceed as follows.

presence of open flame or sparks. Avoid

NOTE

inhalation of vapors. Adequate ven-

Required mix of either 100 parts or

tilation to the outdoors is necessary.

60 parts of resin 202 is specified in table

Prevent contact with eyes and skin. If

3-4.

contact occurs, wash with soap and

a. Preparation of Epocast 202. Combine 100 parts

water.

by weight of hardener 9615 with 60 or 100 parts by

a. Dissolve existing 1B31 from small rework area

weight of resin 202 and stir thoroughly until a

with isopropyl alcohol and cotton swab stick.

uniform color is obtained. Mix only quantities which

b. Replace the defective part using good work-

will be used within 2-1/2 hours. If not used within

manship standards.

2-1/2 hours, discard mixed material.

c. Replace the conformal coating with Type 1B31

b. Repair Using Epocast 202.

used full strength from its container. Shelf life of

CAUTION

1B31 in the container is six months at room tem-

perature. 1B31 maybe thinned with Tuluol/Toluene

Use care in heating Epocast 202 not

to damage nearby components. Use

to adjust thickness, if necessary. Expose only

either 50 watt max soldering iron or heat

quantities of 1B31 to the atmosphere that will be

used within 1-1/2 hours. Any material that has been

gun, whatever will cause the least heating

of components.

exposed 1-1/2 hours, or more, shall be scrapped.

Material shall be stored at room temperature, away

(1) Heat area of Epocast 202 with 50 watt max

from excessive heat.

soldering iron or heat gun until material is soft. Lift

d. Apply a thin coat of conformal coating to the

small component away from material. While still

affected area, overlapping the existing coat about

soft, remove material using a non-metallic tool.

1/16 of an inch to obtain a moisture seal. A short

Clean area of grease, oil, flux and contamination

artist brush will serve as an applicator.

with soft brush and isopropyl alcohol.

e. Allow ten minutes air drying before handling.

(2) When a fillet bond is required, apply fillet

Apply heat by means of an infra-red heat lamp,

along the length of component. A thin layer of

forced-air heat gun or cure in oven. Object is to

adhesive may blend over a portion of the body of the

increase the surface temperature of the coated area

component. When components must be en-

to 170F 5F for one hour.

capsulated, apply adhesive (5 to 20 mils thick) over

f. After the application and cure of conformal

the entire mounting surface of the components.

coating, inspect repair area for any blistering,

(3) Cure adhesive for two to four hours at 150

wrinkling, cracking or peeling of coating. If any of

10F or for 24 hours at room temperature. Clamp

3-25