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• 3 types of Conformal Coating: Silicone Resin (SR) -✓✓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) -
✓✓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 -✓✓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 -✓✓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 -✓✓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 -✓✓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immersed, Then withdrawn from the conformal coating solution.
Immersion speed, withdrawn speed, Immersion time, and Viscosity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 -✓✓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 -✓✓What are the Conformal Coating Removal
Methods by IPC? (4)
• (6) Most Common Coating Defects and causes:
Capillary Flow -✓✓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 -✓✓Visual cracks and creases on components.