CIS Conformal Coating & Encapsulation 1 — Questions and Answers
Question 1: In IPC conformal coating designations, what does 'ER' stand for?
- Ethylene Resin
- Epoxy Resin (Correct answer)
- Ester Resin
- Elastomeric Rubber
Correct answer: Epoxy Resin
ER designates Epoxy Resin per IPC-CC-830, the standard qualification specification for conformal coatings.
Question 2: Which conformal coating type is most difficult to rework once fully cured?
- Acrylic (AR)
- Silicone (SR)
- Epoxy (ER) (Correct answer)
- Urethane (UR)
Correct answer: Epoxy (ER)
Epoxy (ER) coatings are thermoset and chemically cross-linked after curing, making them extremely resistant to solvents and very difficult to remove for rework.
Question 3: Which conformal coating type offers the widest operating temperature range and best high-temperature performance?
- Acrylic (AR)
- Urethane (UR)
- Epoxy (ER)
- Silicone (SR) (Correct answer)
Correct answer: Silicone (SR)
Silicone (SR) coatings retain flexibility and protective properties from approximately -65°C to +200°C, outperforming all other coating types at temperature extremes.
Question 4: Which of the following is NOT a standard method for applying conformal coating to electronic assemblies?
- Brush application
- Selective robotic coating
- Vacuum plasma deposition (Correct answer)
- Dip coating
Correct answer: Vacuum plasma deposition
Standard conformal coating application methods include brush, dip, spray, and selective coating; vacuum plasma deposition is not a recognized IPC application method for conformal coatings.
Question 5: Per IPC-A-610, conformal coating that exhibits delamination from the board surface is classified as which condition?
- Target condition
- Acceptable condition
- Process indicator
- Defect (Correct answer)
Correct answer: Defect
Delamination of conformal coating exposes the assembly to environmental attack and represents a failure of the protective function, making it a defect per IPC-A-610.
Question 6: What primary function does conformal coating serve on a completed electronic assembly?
- Improve electrical conductivity between components
- Protect against moisture, chemical attack, and environmental contaminants (Correct answer)
- Increase the mechanical strength of individual solder joints
- Reduce the overall weight of the board assembly
Correct answer: Protect against moisture, chemical attack, and environmental contaminants
Conformal coating is applied as a thin protective film to shield the assembly from moisture, chemicals, dust, and other environmental stressors that could degrade performance or cause failure.
Question 7: Why do most commercial conformal coatings contain fluorescent UV additives?
- To accelerate the curing process under UV lamps
- To allow visual verification of coating coverage using a UV black light (Correct answer)
- To improve the coating's moisture resistance properties
- To meet RoHS compliance requirements
Correct answer: To allow visual verification of coating coverage using a UV black light
UV fluorescent tracers cause the coating to glow visibly under ultraviolet light, enabling inspectors to quickly identify coated versus uncoated areas during quality control inspection.
CIS Conformal Coating & Encapsulation 1
In IPC conformal coating designations, what does 'ER' stand for?