HumiSeal UV50 is a one-part, high solids dual cure acrylated polyurethane conformal coating possessing excellent chemical resistance, flexibility and moisture resistance. HumiSeal® UV50 has a higher flexibility compared to other UV curable conformal coatings, giving improved performance in thermal cycling tests. The material is tack free after exposure to UV light. A secondary moisture cure mechanism will fully cure any unexposed areas of the coating within 7 days at ambient conditions. The coating fluoresces under UV light to allow coating inspection and can be applied by all selective coating equipment. The coating contains no VOCs or solvent.
Typical Properties of HumiSeal® UV50
|Density||1.0 to 1.1 g/cm3|
|Minimum Solids Content||95%|
|Viscosity, per Fed-Std-141, Meth. 4287||250 – 350 centipoise|
|Recommended Coating Thickness||25 – 125 microns|
|Recommended UV Cure*||See Below|
|Shelf Life at Room Temperature, from DOM||12 months|
|Glass Transition Temperature – DSC||-4°C|
|Coefficient of Thermal Expansion – TMA||152 ppm/°C Below Tg|
313 ppm/°C Above Tg
|Modulus – DMA||4.74 MPa @ 25°C|
|Dielectric Withstand Voltage, per MIL-I-46058C||> 1500 V|
|Insulation Resistance, per MIL-I-46058C||1.38 x 1012 ohms|
|Moisture Insulation Resistance, per MIL-I-46058C||2.0 x 1010 ohms|
|Surface Insulation Resistance, per IPC-J-STD-004 (mod.)||8.58 log10 ohms|
|Resistance to Chemicals||Excellent|
*Microwave UV cure ovens equipped with “H” style bulbs recommended
Application of HumiSeal® UV50
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® UV50 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 vapour and mist are carried away from the operator.
HumiSeal® UV50 may be applied by brush for rework or touch up only. Brushes should be cleaned with solvent promptly after use.
HumiSeal® UV50 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 UV50 using Arc and Microwave based UV curing equipment. The table below outlines the required dosage and irradiance values necessary to render HumiSeal® UV50 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.
|Dose J/cm2*||Irradiance W/cm2*|
*values measured with a Powerpuck II UV radiometer*
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® UV50 contains a reliable secondary moisture cure mechanism which will cure any shadow areas on the assembly within 7 days at ambient moisture.
HumiSeal® UV50 was designed to be cured using a microwave UV oven equipped with an “H” style bulb. Arc systems can cure HumiSeal® UV50 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.
To flush equipment and clean uncured HumiSeal® UV50, non-alcohol based solvents should be used. HumiSeal® Thinner 600 is recommended.
HumiSeal® UV50 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® UV50.
HumiSeal® UV50 is photosensitive. The product should not be exposed to direct sunlight or full spectrum fluorescent lighting. HumiSeal® UV50 should be stored away from excessive heat, in tightly closed opaque containers at 0 to 25°C to ensure maximum shelf life is achieved. Prior to use, allow the product to equilibrate for 24 hours at room temperature. HumiSeal® UV50 is a moisture curing material and care should be taken to protect process vessels and partial containers from moisture. Partial containers must be purged with a dry, inert gas such as dry air, nitrogen or argon before closure, otherwise premature polymerization by atmospheric moisture will occur.
Application of HumiSeal® Conformal Coatings should be carried out in accordance with local and national health and safety regulations.
Use only in well-ventilated areas to avoid inhalation of vapours or spray. Avoid contact with skin and eyes.