Conformal Coating Comparison Guide

The following guide is only general in nature and serves as a broad comparison of strengths and weaknesses.

ACRYLIC

5 Strengths of Coating Type

5 Weaknesses of Cure Type

  • Ease of rework
  • Simple drying process
  • Good moisture resistance
  • High Fluorescence level
  • Ease of viscosity adjustment

Solvent Evaporation

  • High VOC potential
  • Difficult to maintain viscosity
  • Requires close monitoring of solvent concentration, hence creates a 2-part scenario
Full Comparison

EPOXY

5 Strengths of Coating Type

5 Weaknesses of Cure Type

  • Useful to about 150ƒC [302ƒF]
  • Harder durometer, abrasion resistance
  • CTE closer to epoxy PCB substrate
  • Higher T g
  • Good dielectric properties

Solvent Evaporation

  • Higher chloride contamination potential
  • Process intensive, difficult to maintain viscosity, complex mix ratios
  • Potential for high stress during temperature cycling conditions
Full Comparison

POLYURETHANE

5 Strengths of Coating Type

5 Weaknesses of Cure Type

  • Good dielectric properties
  • Good moisture resistance
  • Solvent resistance
  • Less reversion potential
  • Abrasion resistance

Solvent Evaporation

  • Moisture affects cure rate and desired properties
  • Long complete cure time (up to 30 days)
  • Health and safety concerns
Full Comparison

SILICONES

5 Strengths of Coating Type

5 Weaknesses of Cure Type

  • Stable over wide temperature range (in general, -40ƒC to 200ƒC)[104ƒF to 392ƒF]
  • Flexible, provides dampening and impact protection
  • Good moisture, humidity, and UV/sunlight resistance

Room Temperature Vulcanization (RTV)

  • Requires humidity (minimum 20% RH) to cure and only intermittent solvent resistance
  • Low abrasion resistance
  • Short pot life
Full Comparison

POLY-PARA-XYLELENE C, D, N

5 Strengths of Coating Type

5 Weaknesses of Cure Type

  • Excellent uniformity regardless of part geometry ‘ no pinholes, fillets, or bridging
  • Chemical inertness/barrier properties ‘ insoluble in organic solvents, acids, or bases, with very low permeability rates

Vapor Deposition Polymerization

  • Parts are processed by batches in a vacuum chamber, not an in-line process
  • Masking required for no-coat areas
Full Comparison

FLUORINATED POLY-PARA-XYLELENE

5 Strengths of Coating Type

5 Weaknesses of Cure Type

  • Excellent uniformity regardless of part geometry ‘ no pinholes, fillets, or bridging
  • Chemical inertness/barrier properties ‘ insoluble in organic solvents, acids, or bases, with very low permeability rates

Vapor Deposition Polymerization

  • Parts are processed by batches in a vacuum chamber, not an in-line process
  • Masking required for no-coat areas
Full Comparison

AMORPHOUS FLUOROPOLYMER

5 Strengths of Coating Type

5 Weaknesses of Cure Type

  • Low dielectric constant
  • High glass temperature
  • Low surface energy

Solution Deposition

  • Requires special liquids for polymer swelling
  • Limited solubility which limits film thickness
Full Comparison