HumiSeal UV40-250 is a single component, high solids, UV curable, acrylated polyurethane conformal coating that possesses excellent chemical resistance, surface hardness, flexibility and moisture resistance. The material is tack-free after exposure to UV light. A secondary moisture cure mechanism will cure unexposed areas of the coating within 2-3 days at ambient conditions. The coating fluoresces under UV light to allow for coating inspection and can be applied by all selective coating equipment. HumiSeal® UV40-250 is recognized under UL File Number E105698 and is IPC-CC-830 and RoHS Directive 2002/95/EC compliant.
Cleanliness of the substrate is extremely important to the successful application of a conformal coating. Surfaces should 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.
HumiSeal® UV40-250 can be applied via standard selective coating. The source air used for spraying must be dry (a dry inert gas is highly recommended) to prevent premature curing by the secondary cure mechanism. The spraying should be done with adequate ventilation so that the vapour and mist are carried away from the operator.
HumiSeal® UV40-250 is a highly cross linked coating. In order to achieve maximum cross linking density the product must be exposed to the correct spectral output. The table below outlines the required dosage and irradiance values necessary to properly cure HumiSeal® UV40-250. After UV exposure and return to room temperature the coating should be tack free.
Values measured with a Powerpuck II UV radiometer
HumiSeal® UV40-250 was designed to be cured using a microwave UV oven equipped with an “H” style bulb. Arc systems can cure HumiSeal® UV40-250. However, care must be taken during the equipment selection process to ensure minimum dosage and irradiance values can be obtained. For additional cure information please contact HumiSeal technical assistance.
To flush equipment and clean uncured HumiSeal® UV40-250, non-alcohol based solvents should be used. HumiSeal® Thinner 600 is recommended.
HumiSeal® UV40-250 is a highly cross linked UV cured coating. The cured film has a high degree of environmental and chemical resistance and will be more difficult to remove than traditional conformal coatings. Thermal displacement, mechanical abrasion and, where available, HumiSeal® Stripper 1100 are suitable options for rework of HumiSeal® UV40-250.
|Minimum Solids Content||95 %|
|Viscosity, per Fed-Std-141, Meth. 4287||300 ± 50 centipoise|
|Recommended Coating Thickness||25 – 125 microns|
|Recommended UV Dose*||see curing section above|
|Shelf Life at Room Temperature, DOM||6 months|
|Recommended Stripper**||HumiSeal® Stripper 1100|
|Thermal Shock, 50 cycles per MIL-I-46058C||-65°C to 125°C|
|Glass Transition Temperature – DSC||26°C|
|Coefficient of Thermal Expansion||112 ppm/°C Below Tg|
283 ppm/°C Above Tg
|Modulus – DMA||1060 MPa -60°C|
|Flammability, per UL-94||V-0|
|Dielectric Withstand Voltage, per MIL-I-46058C||>1500 volts|
|Dielectric Constant, at 1MHz and 25°C per ASTM D150-98||2.41|
|Dissipation Factor, at 1MHz and 25°C per ASTM D150-98||0.01|
|Insulation Resistance, per MIL-I-46058C||8.0 x 1014 ohms (800TΩ)|
|Moisture Insulation Resistance, per MIL-I-46058C||4.7 x 1010 ohms (47GΩ)|
|Fungus Resistance, per ASTM G21||Pass|
|Resistance to Chemicals||Excellent|
*Microwave UV cure ovens equipped with “H” style bulbs recommended
**Stripper 1100 is not available in the EU