HumiSeal®️ UV40 is a single-component, high solids, UV-curable acrylated polyurethane conformal coating that offers excellent chemical resistance, surface hardness, flexibility, and moisture resistance. The material becomes tack-free upon exposure to UV light. A secondary moisture cure mechanism cures areas not exposed to light within 2–3 days under ambient conditions. The coating fluoresces under UV light to enable inspection and can be applied using selective coating equipment. HumiSeal®️ UV40 coating is recognized under UL File Number E105698 and is approved to MIL-I-46058C; it is also compliant with IPC-CC-830 and RoHS Directive 2011/65/EC.
Properties of HumiSeal®️ UV40:
Density: 1.10 ± 0.05 g/cm³
Minimum Solids Content: 95%
Viscosity: 650 ± 150 centipoise
Recommended coating thickness: 25–125 microns
Recommended UV curing: See curing section below
Shelf life at room temperature: 12 months
Recommended remover**: HumiSeal®️ Stripper 1100
Thermal shock (50 cycles according to MIL-I-46058C): -65°C to 125°C
Flammability: UL-94 V-0
Conformal coatings can be successfully applied to surfaces that have been cleaned prior to coating, as well as to surfaces assembled using low-residue, “no-clean” materials. Users should perform the necessary testing to verify compatibility between the conformal coating and their specific assembly materials, process conditions, and cleanliness levels.
Curing:
HumiSeal®️ UV40 is a highly cross-linked coating material. To achieve maximum cross-link density, the product must be exposed to the correct spectral irradiation. HumiSeal has modeled the performance of UV40 using arc and microwave-based UV curing equipment. The table below summarizes the dosage and irradiation levels required to eliminate tackiness of HumiSeal®️ UV40 after UV exposure with both types of equipment. Minimum values should provide a tack-free surface. The maximum recommendations represent the highest values tested by HumiSeal. Curing recommendations may change as curing technologies evolve.
| | Dose J/cm2 * | Irradiance W/cm2 * |
|---|
| | UVA | UVB | UVC | UVA | UVB | UVC |
|---|
| Min | Arc System |
1.5 |
1.5 |
0.40 |
0.50 |
0.50 |
0.10 |
|---|
| Min | Microwave System |
2.0 |
2.0 |
0.40 |
0.70 |
0.70 |
0.15 |
|---|
| Max | Arc System |
2.8 |
2.7 |
0.80 |
0.90 |
0.80 |
0.20 |
|---|
| Max | Microwave System |
3.0 |
3.0 |
0.60 |
1.15 |
1.15 |
0.24 |
|---|
*Values were measured using a Powerpuck II UV radiometer.
Heat is also an important factor in the UV curing process, and different systems generate varying levels of heat output. Higher heat levels can enable UV curing at lower dose/irradiance levels. Therefore, HumiSeal®️ recommends consulting with its technical team to ensure that the curing process fully meets the coating’s requirements. After exposure to UV radiation and once returned to room temperature, the coating should be tack-free. It includes a reliable secondary moisture cure mechanism that will cure shadowed areas on the assembly within 7 days under ambient humidity. It is designed to be cured using a microwave UV oven equipped with an “H” type bulb. Arc systems can cure HumiSeal®️ UV40; however, care must be taken during equipment selection to ensure that the achieved minimum dose and irradiance values are sufficient for proper curing. Due to potential variations in curing equipment type and configuration, it is strongly recommended to contact HumiSeal Technical Support to discuss your specific equipment and process in detail.
Cleaning:
Alcohol-free solvents should be used to clean equipment and remove uncured material. The use of HumiSeal®️ Thinner 521 or Thinner 521EU is recommended.
Rework:
This is a highly cross-linked, UV-cured coating. The cured film exhibits high environmental and chemical resistance and is more difficult to remove than conventional conformal coatings. Thermal displacement, mechanical abrasion, and, where available, HumiSeal®️ Stripper 1100 are suitable options for reworking HumiSeal®️ UV40.
Storage:
Light-sensitive. The product should not be exposed to direct sunlight or full-spectrum fluorescent light. For maximum shelf life, store in tightly sealed opaque containers between 0°C and 25°C, away from excessive heat. Before use, allow the product to equilibrate at room temperature for 24 hours. It is a moisture-curing material, and care should be taken to protect process containers and partially filled containers from moisture. Partially filled containers should be purged with a dry, inert gas such as dry air, nitrogen, or argon before sealing; otherwise, premature polymerization may occur due to atmospheric moisture.
