HumiSeal UV500 is a high solids UV dual cure elastomeric acrylate conformal coating. HumiSeal® UV500 exhibits excellent flexibility, moisture resistance and electrical insulation properties as well as good chemical resistance. The formulation allows chemical stripping using a dedicated stripper. HumiSeal® UV500 is tack free after exposure to UV light and the secondary moisture cure mechanism will fully cure any unexposed areas of the coating within 7 days at ambient conditions. Cured HumiSeal® UV500 has a higher flexibility compared to other UV curable conformal coatings, giving improved performance in thermal cycling tests. The coating fluoresces under UV light to allow coating inspection and can be applied by all selective coating equipment.
Typical Properties of HumiSeal® UV500
|Density||1.0 to 1.1 g/cm3|
|Minimum Solids Content||98 %|
|Viscosity, per Fed-Std-141, Meth. 4287||275 – 375 centipoise|
|Recommended Coating Thickness||25 – 125 microns|
|Recommended UV Cure||See Curing Below|
|Shelf Life at Room Temperature, from DOM||6 Months|
|Glass Transition Temperature – DSC||-43°C|
|Coefficient of Thermal Expansion – TMA||137 ppm/°C Below Tg|
311 ppm/°C Above Tg
|Modulus – DMA||0.4 MPa @ 25°C|
|Dielectric Withstand Voltage, per MIL-I-46058C||>1500 V|
|Surface Resistivity per ASTM D-257||2.0 x 1011 ohms|
|Volume Resistivity per ASTM D-257||8.0 x 1012 ohms.cm|
|Insulation Resistance, per MIL-I-46058C||4.5 x 1011 ohms|
|Moisture Insulation Resistance, per MIL-I-46058C||1.6 x1010 ohms|
|Surface Insulation Resistance (per IPC J-STD-004 (mod.))||8.9 log10 ohms|
|Resistance to Chemicals||Good|
Application of HumiSeal® UV500
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® UV500 Technical Data Sheet
HumiSeal® UV500 can be applied via standard selective coating equipment or by conventional hand spray equipment. The source air used for spraying must be dry (a dry inert gas (nitrogen or argon) is highly recommended) to prevent premature curing of the secondary cure mechanism. The spraying should be done with adequate ventilation so that the vapor and mist are carried away from the operator.
HumiSeal® UV500 may be applied by brush for rework or touch up only. Brush must be cleaned with solvent promptly after use.
HumiSeal® UV500 is a highly cross linked coating. In order to achieve maximum cross linking density the product must be exposed to the correct spectral output. Humiseal has modelled the performance of UV500 using Arc and Microwave based UV curing equipment. The table below outlines the required dosage and irradiance values necessary to render HumiSeal® UV500 tack free post UV exposure with both equipment types. Minimum figures should provide a tack free surface. The maximum recommendation represents highest tested values by Humiseal. The cure recommendations may change as curing technology develops.
Heat is also an important component with UV cure, and different systems produce different heat outputs. Higher heat levels allow UV cure at lower dose/irradiance levels. Consequently, Humiseal recommend that curing is discussed with HumiSeal® Technical staff to ensure the exact customer process being used will meet the coating cure requirements. After UV exposure and return to room temperature the coating should be tack free.
HumiSeal® UV500 contains a reliable secondary moisture cure mechanism which will cure any shadow areas on the assembly within 7 days at ambient moisture.
HumiSeal® UV500 was designed to be cured using a microwave UV oven equipped with an “H” style bulb. Arc systems can cure HumiSeal® UV500 however care must be taken during the equipment selection process to ensure minimum dosage and irradiance values obtained will properly cure the coating. Because of the variations possible in curing equipment type and configuration, it is strongly recommended that you contact HumiSeal Technical Support to discuss your equipment and process in detail.
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