Urethane 1A33 LTX & Pre-blended Products

HumiSeal® 1A33 LTX conformal coating is:

  • Polyurethane conformal coating
  • single component
  • suitable for general printed circuit board applications
  • MIL-I-46058C qualified
  • IPC-CC-830
  • RoHS Directive 2011/65/EU compliant and recognized under UL File Number E105698

*Standard GB30981-2020 defines limits on VOCs and solvent usage for Conformal Coatings. Standard GB/T 23990-200 defines the test method for Solvent % analysis.

HumiSeal 1A33 LTX conformal coating has:

  • Protection against moisture, salt, and corrosive environments and dirt
  • Easy application with automated systems
  • Low moisture vapor permeability.
  • Fluoresces under UV for ease of inspection and is easily repaired.
  • Range of pre-blends thinners available for different application methods
  • Compliant with GB30981-2020

Application of 1A33 LTX 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, flux residues and all other contaminants. Contamination under the coating could cause problems that may lead to assembly failures.

HumiSeal®1A33 LTX Pre-blend Products are specifically diluted to a viscosity for immediate use. No additional dilution is required. Customers should establish which Pre-Blend is suitable for their equipment and application method before commercial use.  HumiSeal® Technical Support should be contacted if any further advice on Pre-blend Products and equipment is required.

Depending on the complexity, density and configuration of components on the assembly, it may be necessary to reduce the viscosity of HumiSeal 1A33 with HumiSeal Thinner 503 in order to obtain a uniform film. Once optimum viscosity is determined, a controlled rate of immersion and withdrawal (typically, 5 to 15 cm/min) will further ensure even deposition of the coating and provide a uniform film. During application, evaporation of solvent causes an increase in viscosity that should be adjusted by adding small amounts of HumiSeal® Thinner 503. Viscosity in the dip tank should be checked regularly using a simple measuring device, such as a Zahn or Ford viscosity cup. 

HumiSeal® 1A33 LTX and Pre-Blends should be stored away from excessive heat or cold, in tightly closed containers.  HumiSeal® products may be stored at temperatures of 0 to 35°C.  Prior to use, allow the product to equilibrate for 24 hours at a room temperature of 18 to 32°C.

Application of HumiSeal® Conformal Coatings should be carried out in accordance with local and National Health and Safety regulations.

The solvents in HumiSeal® Conformal Coatings are flammable. The material should not be used in presence of open flame or sparks. Use only in well-ventilated areas to avoid inhalation of vapors or spray.  Avoid contact with skin and eyes.

Properties of HumiSeal® 1A33 LTX Pre-blended Products

Product Viscosity








1A33 LTX 160- 240 44 ± 2 0.95 ± 0.02 532
1A33 LTX/521 PB65 60 – 75 40 ± 2 0.93 ± 0.02 559

Product Specification

Recommended Coating Thickness 25 – 75 microns
Drying Time to Handle per Fed-Std-141, Meth. 4061 15 minutes
Optional Curing Conditions to Reach Optimum Properties 30 days @ RT

30 hours @ 76°C

20 hours @ 88°C

Recommended Stripper HumiSeal® Stripper 1063
Thermal Shock, 50 cycles per MIL-I-46058C -65°C to 125°C
Coefficient of Thermal Expansion – TMA 193 ppm/°C
Glass Transition Temperature – DSC 26°C
Modulus – DMA 27.2 MPa
Flammability, per UL 94 V-0
Dielectric Withstand Voltage, per MIL-I-46058C >1500 volts
Dielectric Breakdown Voltage, per ASTM D149 7500 volts
Dielectric Constant, at 1MHz and 25°C per ASTM D150-98 3.6
Dissipation Factor, at 1MHz and 25°C, per ASTM D150-98 0.03
Insulation Resistance, per MIL-I-46058C 2.0 x 1014 ohms (200TΩ)
Moisture Insulation Resistance, per MIL-I-46058C 1.6 x 1010 ohms (16GΩ)
Fungus Resistance, per ASTM G21 Passes