Silicone Modified Conformal Coating
422B Technical Data Sheet
ISO 9001:2008 Registered Quality System. Burlington, Ontario, CANADA
SAI Global File: 004008
422B
Description
The 422B
Silicone Modified Conformal Coating
is a clear and flexible coating that is ideal for protecting
electronic circuits in high temperature environments or applications requiring extreme flexibility. It
protects against moisture, dirt, dust, and other particulates, and thus avoids corrosion of electronic
components. It also insulates against high-voltage arcing, shorts, and static discharges. As well, it
protects against thermal shock and puts very little stress on components during temperature cycling.
Compared to other typical silicones, the 422B is a one-part, acrylated silicone which makes it is easier to
apply, remove, and rework. Also, it has a faster cure time and a much longer shelf life. It is available in
both aerosol, liquid, and pen form and may be applied by spraying, dipping, or brushing.
The 422B protective coating is UL certified under the
Coatings for Use on Recognized Printed Wiring
Boards—Component
category. It performs as a 94V-0 non-flammable coating. It is intended as an easy-
to-use, cost-effective
solution for protection against the typical risks PCB’s face in high temperature
environments. It is not intended for high voltage applications (>1500 V) with extended exposures (days)
to very high humidity (>95%) and temperature environments (>65 °C [149 °F]). Customers with such
applications should inquire about our line of silicone conformal coatings from Momentive Performance
Materials.
Applications & Usages
The 422B improves reliability and lengthens the life of electronic circuitry. Its primary applications are in
the automobile, marine, aerospace, aviation, communication, instrumentation, and industrial control
equipment industries that involve high temperatures.
Benefits and Features
•
•
•
•
•
•
•
Certified flammability rating of
UL 94V-0
(File #
E203094)
Maximum constant service temperature of 200
°C
Fast drying time—tack
free in 7 min at room temperature; dries in 20 min at 65 °C
Protects electronics
from moisture, corrosion, fungus, thermal shock, and static discharges
Easy to inspect:
fluoresces blue at 437 nm ±65 nm under UVA light
Extended shelf life
avoids worries about premature hardening and wastage
Easy rework and repairs:
o
o
Solders through the coat
Removable with Cat. No. 435 thinner
Page
1
of
6
Rev. Date: 09 August 2018 / Ver. 2.01
Silicone Modified Conformal Coating
422B Technical Data Sheet
ISO 9001:2008 Registered Quality System. Burlington, Ontario, CANADA
SAI Global File: 004008
422B
Usage Parameters
Properties
Tack Free
Shelf life
Drying Time @20 °C [68 °F]
Drying Time @65 °C [149 °F]
Theoretical HVLP Spray
Coverage
a)
Value
5-7 min
5y
48 h
20 min
≤61 800
cm
2
/L
≤6.18
m
2
/L
≤9
580 in
2
/gal
≤67
ft
2
/gal
Temperature Ranges
Properties
Constant Service
Temperature
Value
-40 to 200 °C
[-40 to 392 °F]
a) Idealized estimate based on a coat thickness
of 25
m
[1.0 mil] and 100% transfer
efficiency
Principal Components
Name
Silicone and acrylic resin combination
Xylene
Acetone
Ethyl benzene
CAS Number
proprietary
1330-20-7
67-64-1
100-41-4
Cured 422B Properties
Physical Properties
Color
Solderability
Flexibility
Flammability
UV inspection absorption max
UV inspection
fluorescence max
Electrical Properties
Dielectric Strength @0.0150"
Volume Resistivity @23 °C 50% RH
Surface Resistivity
Dielectric Constant @60 Hz, 25 °C [77 °F]
Dielectric Constant @1 MHz, 25 °C [77 °F]
Dissipation Factor @60 Hz, 25 °C [77 °F]
Dissipation Factor
@1 MHz, 25 °C [77 °F]
Method
Visual
—
—
UL File #
E203094
Absorption spectrum
Emission spectrum
Method
IPC-TM-650 Test 2.5.6.1
ASTM D 257-07
"
ASTM D 150-98
"
"
"
Value
Clear
Fair
Excellent
94V-0
375 nm (near UV)
437 nm (blue)
Value
1 056 V/mil
1.2 x 10
15
Ωcm
4.5 x 10
16
Ω/sq
2.35
1.99
0.037
0.012
Page
2
of
6
Rev. Date: 09 August 2018 / Ver. 2.01
Silicone Modified Conformal Coating
422B Technical Data Sheet
ISO 9001:2008 Registered Quality System. Burlington, Ontario, CANADA
SAI Global File: 004008
422B
Value
253 ppm/°C
None detected
31 °C [88 °F]
Value
5B = 0% area removed
None
No change
None
Thermal Properties
Coefficient of Thermal Expansion (CTE)
Glass Transition Temperature (T
g
)
Softening Point
Environmental & Ageing Study
Salt Spray Test: 7 day @35 °C +Salt/Fog
Cross-hatch adhesion
Cracking, unwashed area
Visual Color, unwashed area
Peeling, unwashed area
Method
IPC-TM-650 Test 2.4.24
"
"
Method
ASTM B117-2011
ASTM D3359-2009
ASTM D661-93
ASTM D1729-96
"
Uncured 422B Properties
Physical Properties
Odor
Viscosity @23 °C [73 °F]
Density
Flash Point
Boiling Point
Solids Content (w/w)
Method
—
Brookfield SP1
Closed Cup
Value
Ethereal
60 cP [0.060 Pa·s]
0.898 g/mL
-18 °C [-0.40 °F]
55 °C [131 °F]
28%
Compatibility with Substrate
The 422B silicone is compatible with most materials found on printed circuit assemblies; however, in an
uncured state it is not compatible with contaminants like water, oil, and greasy flux residues. Therefore, it
is extremely important to clean the printed circuit assembly thoroughly with a suitable electronic cleaner
before applying the coating.
The chosen electronic cleaners should remove moisture, wax, greases, oils, and all other contaminants
that are known to cause defects in this type of conformal coating (see recommended cleaners on page 5).
Health, Safety, and Environmental Awareness
Please see the 422B
Safety Data Sheet
(SDS) for more details on transportation, storage, handling and
other security guidelines.
Environmental Impact:
The 422B formulation is free from ozone depletion compounds. The coating is
RoHS compliant.
Page
3
of
6
Rev. Date: 09 August 2018 / Ver. 2.01
Silicone Modified Conformal Coating
422B Technical Data Sheet
ISO 9001:2008 Registered Quality System. Burlington, Ontario, CANADA
SAI Global File: 004008
422B
Health and Safety:
The liquid is flammable and should be kept away from flames and other ignition
sources. As with most paint materials, avoid breathing in fumes or direct contact with the material.
Solvents therein can cause irritation and other symptoms like headaches, pain, as well as having long
term exposure effects. The cured coating presents no known hazard.
Wear safety glasses and disposable nitrile gloves for short contact (<4 hours). For extended contact use
Viton gloves. Wash hands thoroughly after use. Use in the open air, in fume hoods, or in well ventilated
area. For short or long term (8 hours) at levels of exposures exceeding 100 ppm xylene or 750 ppm
acetone, use NIOSH approved respirator with organic vapor cartridges rated for this order of
concentrations.
HMIS® RATING
HEALTH:
FLAMMABILITY:
PHYSICAL HAZARD:
PERSONAL PROTECTION:
Approximate HMIS and NFPA Risk Ratings Legend:
0 (Low or none); 1 (Slight); 2 (Moderate); 3 (Serious); 4 (Severe)
NFPA® 704 CODES
* 2
3
0
3
2
0
Spray Gun Application Instructions
Read the procedure below and make necessary adjustments according to your spray gun equipment usage
instructions.
Thinning Requirements
Let down is not required for 422B and will usually lead to a dry film thickness of roughly 1 mil [25
m]
in
one coat (depending on the operator). When diluted 1:1, each coat results in a dry film thickness of
roughly 0.5 mil [13
m].
If higher solid percent grade or custom blends are used, contact us for details.
m
[1 to 1.5 mil]. Since it is a
solvent-based and acrylated silicone system, the thickness upper limit is below 75
m
[3 mil]. The usual
limits for solvent-less silicone systems that have thermosetting cure mechanisms do not apply.
Spray Equipment
Use a HVLP (high-volume, low pressure) spray gun using the initial settings described in the following
table. Adjust these settings and recommendations as required.
A
TTENTION
!
MG Chemicals recommends a dry film thickness of 25 to 38
Page
4
of
6
Rev. Date: 09 August 2018 / Ver. 2.01
Silicone Modified Conformal Coating
422B Technical Data Sheet
ISO 9001:2008 Registered Quality System. Burlington, Ontario, CANADA
SAI Global File: 004008
422B
Initial Setting Recommendations
Air Cap
Pressure
Fluid Tip
#3 HVLP
Inlet
23 psi
1.3 mm [0.051"]
Air flow
b)
13.5
1.5 mm [0.059"]
a)
Air cap
10 psi
Note:
These recommendations are based on a generic paint gun and may differ by brands. Please consult
your spray gun manufacturer’s guide.
a) If no or reduced let down is performed, this may be a better tip choice.
b) SCFM = standard cubic foot per minute
To apply the required thickness
1. Mix the paint thoroughly with a paint shaker, mixer, or spatula.
2. Dilute by a ratio of
1:1
(Paint:Thinner) or another ratio of your choice.
3. Make a test spray. Adjust the spray settings for best flow and spray quality, and establish an
appropriate distance to avoid paint runs. A distance between 23 to 30 cm (9 to 12 in) is
recommended.
4. Spray a thin and even coat onto the vertical surface to be coated. For best results, start your
movement off-surface, press the trigger, and only release off-surface at the end of the stroke. Use
a uniform movement of the spray gun parallel to the surface.
5. Wait at least 5 minutes and spray another coat. This delay avoids trapping solvent between coats.
6. Rotate the board 90° to ensure good coverage.
7. Apply additional coats until desired thickness is achieved (go to Step 3).
8. Let dry for 7 minutes (flash off time) at room temperature.
A
TTENTION
!
Spraying overly thick coats may cause paint runs and hamper solvent evaporation.
Prefer the application of many thin wet coats rather than fewer heavy coats.
Pen Application Instructions
Follow the procedure below for best results.
To apply the liquid pen
1.
2.
3.
4.
5.
Ensure that the surface to be coated is clean and oil-free.
Shake the pen vigorously.
Test on a blank to ensure good flow quality and uniformity during application.
Touch the pen lightly on the surface while squeezing the barrel to apply thin and even coat.
Let dry for 3-5 minutes (flash off time) at room temperature before handling.
To cure the conformal coating
•
•
Full cure can be achieved in 48 hours at room temperature.
Full cure can be achieved in 20 minutes by using an infrared lamp or in convection oven at
65 °C [149 °F].
Note:
The procedure above is based on a minimum thickness of 25
m
[1 mil] conformal coating. After
full cure, measure the actual conformal coating thickness to ensure it meets the applications
requirements. Custom cure instructions are required for higher thicknesses (contact us for details).
Page
5
of
6
Rev. Date: 09 August 2018 / Ver. 2.01
stm32/stm8
