Urethane 1A20R

HumiSeal® 1A20R conformal coating is:

  • Urethane chemistry
  • fast curing, chemically resistant
  • single component
  • used in combination with Thinner 521
  • recognized under UL File Number E105698.

HumiSeal 1A20R conformal coating has:

  • excellent moisture and environmental protection for printed circuit assemblies
  • fluorescence under UV light for ease of inspection
  • MIL-I-46058C qualified
  • IPC-CC-830 compliance

HumiSeal 1A20R has similar performance properties to 1A20, but offers a better stability and longer shelf life.

Application of 1A20R Conformal Coating

Cleanliness of the substrate is of extreme importance for the successful application of a conformal coating. Surfaces must be free of moisture, dirt, wax, grease, and all other contaminants. Otherwise, ionic or organic residues on the substrate could be trapped under the coating and cause problems with adhesion or electrical properties. The highest long term reliability for a coated printed circuit assembly will be when the conformal coating is applied over a clean, dry substrate.

The application of conformal coatings over no clean flux is a common practice. The user should perform adequate testing to confirm compatibility between the conformal coating and their particular assembly materials and process conditions. Please contact HumiSeal for additional information.

Although its formulation allows HumiSeal® 1A20R to be applied using a wide variety of methods, care should be taken to ensure that it is only applied in an environment where the ambient relative humidity is at 60% or less. Application of the coating when the RH is higher than 60% can cause acceleration of the cure reaction, resulting in bubbles in the dried film.


Depending on the complexity, density and configuration of components on the assembly, it may be necessary to reduce the viscosity of HumiSeal® 1A20R with HumiSeal® Thinner 521 or 521EU in order to obtain a uniform film. Once optimum viscosity is determined, a controlled rate of immersion and withdrawal (5-15 cm/min) will further ensure even deposition of the coating and ultimately a uniform film. During the application, evaporation of solvent causes an increase in viscosity that should be adjusted by adding small amounts of HumiSeal® Thinner 521 or 521EU. Viscosity in the dip tank should be checked regularly, using a simple measuring device such as a Zahn or Ford viscosity cup.


HumiSeal® 1A20R can be sprayed using conventional spraying equipment. Spraying should be done in an environment with adequate ventilation so that the vapour and mist are carried away from the operator. The addition of HumiSeal® Thinner 521 or 521EU is necessary to ensure a uniform spray pattern resulting in pinholefree film. The amount of thinner and spray pressure will depend on the specific type of spray equipment used and operator technique. The recommended ratio of HumiSeal® 1A20R to HumiSeal® Thinner 521 or 521 EU is 5:2 by volume; however the ratio may need to be adjusted to obtain a uniform coating.


HumiSeal® 1A20R may be brushed with a small addition of HumiSeal® Thinner 521 or 521EU. Uniformity of the film depends on component density and operator’s technique.

Product Specification
Density, per ASTM D1475 1.02 ± 0.02 g/cm3
Solids Content, % by weight per Fed-Std-141, Meth. 4044 50 ± 3 %
Viscosity, per Fed-Std-141, Meth. 4287 100 ± 30 centipoise
VOC 511grams/litre
Recommended Coating Thickness 25 -75 microns
Drying Time to Handle per Fed-Std-141, Meth. 4061 60 minutes
Recommended Curing Conditions 24 hrs @ RT or 3 hrs @ 76°C
Time Required to Reach Optimum Properties 7 days
Thinner, if needed (dipping, brushing, spraying)  HumiSeal® Thinner 521, 521EU
Recommended Stripper  HumiSeal® Stripper 1072
Shelf Life at Room Temperature, DOM  6 months
Thermal Shock, per MIL-I-46058C  -65°C to 125°C
Coefficient of Thermal Expansion – TMA 515 ppm/°C
Glass Transition Temperature – DSC  71°C
Modulus – DMA  89.6 MPa
Flammability, per UL94  V-0
Dielectric Withstand Voltage, per MIL-I-46058C  >1500 volts
Dielectric Constant, at 1MHz and 25°C per ASTM D150-98  3.5
Dissipation Factor, at 1MHz and 25°C per ASTM D150-98  0.028
Insulation Resistance, per MIL-I-46058C 3.0 x 1014 ohms (300TΩ)
Moisture Insulation Resistance, per MIL-I-46058C  4.8 x 1010 ohms (48GΩ)
Fungus Resistance, per ASTM G21 Passes
Resistance to Chemicals  Excellent