IPC-A-610 Test Questions With Complete Solutions
3 types of Conformal Coating: Acrylic Resin (AR) - Answer-This type of coating provides FAIR elasticity and general protection. It has high dielectric strength, and fair moisture and abrasion resistance. This coating is different from others beca...
3 types of Conformal Coating: Acrylic Resin (AR) - Answer-This type of coating provides
FAIR elasticity and general protection. It has high dielectric strength, and fair moisture
and abrasion resistance. This coating is different from others because its facility for
removal. This type are EASILY and quickly removed by a variety of solvents, often
without requiring agitation. This makes rework and field repair very practical and
economical. This type doesn't protect against solvents and solvent vapors.
/.3 types of Conformal Coating: Silicone Resin (SR) - Answer-This type of coating
provides EXCELLENT protection in a very wide temperature range. This coating
provides good chemical resistance, moisture, and salt spray resistance, and is very
flexible. This type is NOT abrasion resistant because of its rubbery nature, but this
property does make it resilient against vibrational stresses. Commonly used in high-
humidity environments. Removal can be CHALLENGING. requiring specialized
solvents, long soak time, and agitation from a brush.
/.3 types of Conformal Coating: Urethane (Polyurethane) Resin (UR) - Answer-This type
of coating is known for its EXCELLENT moisture and chemical resistance. It is also very
abrasion resistant. Combining those factors with its SOLVENT RESISTANCE results in
a conformal coating that is very difficult to remove. Like SR, full removal generally
requires special solvents, long soak time, and agitation with a brush. This is common in
aerospace application. ex: Conathane
/.5 Coating application methods: Manual Spraying - Answer-Aerosol can or handheld
spray gun. Time consuming method of coating for a small quantity of boards. Lots of
masking beforehand. Quality and consistency of outcome are operator- dependent.
/.5 Coating application methods: Automated spraying - Answer-Programmed spray
system that moves the board on a CONVEYOR under an alternative spray head that
applies a conformal coating.
/.5 Coating application methods: Selective coating - Answer-An automated conformal
coating process that uses PROGRAMMABLE ROBOTIC SPRAY NOZZLES to apply
the coating to very specific areas on the circuit board. May eliminate the need for
masking using the program. The UV lamp in machine helps cure the coating right after it
is sprayed.
/.5 Coating application methods: Dipping - Answer-The circuit board is first immersed,
Then withdrawn from the conformal coating solution. Immersion speed, withdrawn
speed, Immersion time, and Viscosity determine the resulting film formation. Common
for high volume processing. Masking may increase. This method is good to coat both
Front and Back of the board.
, /.5 Coating application methods: Brushing - Answer-Simple application method used
mainly in repair and rework. Conformal Coating is applied with a BRUSH to specific
areas on the board. Low-cost method but requires lots of manual labor and is highly
variable depending on operator proficiency and consistency. This is the best for a small
batch or a single board.
/.1. Solvent Removal
2. Peeling
3. Microblasting: using a concentrated mix of soft abrasive and compressed air to
abrade the coating.
4. Grinding/Scaping - Answer-What are the Conformal Coating Removal Methods by
IPC? (4)
/.(6) Most Common Coating Defects and causes:
Capillary Flow - Answer-occurs when coating migrates from one area of a board to
another, leaving behind an inconsistent, uneven finish on the surface.
Causes: -application of too much coating
- coating with low viscosity or high surface tension.
- low surface energy of component being coated.
/.(6) Most Common Coating Defects and causes:
Cracking and Ripples - Answer-Visual cracks and creases on components.
Causes: -coating is too thick
- thermal shock
- coating cured too quickly
/.(6) Most Common Coating Defects and causes:
Dewetting - Answer-Coating will not evenly coat the surface to which its applied.
Causes: - uneven coating application.
- improper mixture of two- part material.
- Residue on coating surface.
- Surface tension and surface energy.
/.(6) Most Common Coating Defects and causes:
Delamination - Answer-When coating has lifted up and away from the board. This
hinders protection because the area below the coating is left exposed. (Ex:Ripping off
more coating after demasking and pulling off too much coating around the area.
Causes:
-too thick of coating
- coating not adhering to previous coating layer.
-contamination of surface of the board.
/.(6) Most Common Coating Defects and causes:
Orange Peel - Answer-Coating appears dull, resembling the skin of a fruit or basketball.
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