Dual Cure Acrylated Urethane Coating
HumiSeal UV40 is a one-part high solids dual cure acrylated polyurethane conformal coating possessing excellent chemical resistance, surface hardness, flexibility and moisture resistance. The material is tack free after exposure to UV light and the secondary moisture cure mechanism will fully cure any unexposed areas of the coating within 2-3 days at ambient conditions. The secondary cure can be accelerated by baking at 60-800 C with a small pan of water placed in the oven to increase humidity. The coating fluoresces under UV light to allow coating inspection and can be applied by all selective coating equipment. This coating is MIL-I46058C and IPC-CC-830 qualified and is recognized under the Component Program of Underwriters Laboratories, Inc., File Number E 105698. HumiSeal UV40 is in full compliance with the RoHS Directive (Directive 2002/95/EC).
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. Contamination under the coating will cause problems that may lead to assembly failures.
HumiSeal UV40 is not suitable for dipping.
UV40 - Spraying
HumiSeal UV40 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 is highly recommended) to prevent premature curing of UV40’s effective secondary cure mechanism.. The spraying should be done with adequate ventilation so that the vapor and mist are carried away from the operator.
Brushing – UV40
HumiSeal UV40 may be applied by brush. The actual uniformity of the finished coating will depend on component density and operator technique. Brushed may be cleaned promptly using solvent.
To flush equipment and clean uncured UV40, organic solvents such as methyl ethyl ketone, t-butylacetate, glycol ether acetates etc. can be used.
HumiSeal UV40 is a highly crosslinked 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. The following options are available for rework of UV40.
Thermal Removal: The most effective method for removal of UV40 for selective rework applications is to burn through the coating directly using a hot soldering iron. The high temperature of the soldering iron (typically 300-400C) softens and decomposes the coating and allows it to be easily displaced from the substrate. This allows access to the underlying solder connections for component removal and replacement. A hot air desoldering tool may also be used also. Apply heat to the desired area and the coating can be removed mechanically after it softens. Care should be taken to avoid damage to any heat sensitive components.
Mechanical Removal: This method involves the use of “micro-blasting” equipment that safely removes the cured coating by using a pressurized abrasive. After coating removal, the abrasive can be removed from the assembly surface without damage to the components. HumiSeal UV40 has been successfully removed using the Micro-Blaster System from Comco Inc. (800-796-6626, www.comcoinc.com), but there are several companies that supply similar systems.
Chemical Removal: If the UV40 coating has been UV cured only and not allowed to undergo any further moisture curing, HumiSeal Stripper 1072 could be used to remove the UV-cured film. Extended dwell times and periodic mechanical agitation could be required. Warming the 1072 solution can increase its effectiveness.
Refer to MSDS to insure proper storage conditions. HumiSeal UV40 should be stored at 0-1000 F, away from excessive heat, in tightly closed opaque containers. Prior to use allow the product to equilibrate for 24 hours at room temperature. Since UV40 is photosensitive, the product should not be exposed to direct sunlight or full spectrum fluorescent lighting. UV40 is a moisture curing material and care should be taken to protect process vessels and partial containers from moisture. Partial, opened containers should be purged with a dry, inert gas such as dry air, nitrogen or argon before closure, otherwise premature polymerization by atmospheric moisture will occur.