Parylene vs HumiSeal®

The conformal coating process establishes a protective barrier for product substrates. The selection of coating material is influenced by various factors:

• The type of assembly/product being coated
• The coating substance’s ability to provide appropriate protection
• The external environment of the item’s material composition/intended use
• The coating’s process requirements and cost relative to other coating materials

HumiSeal® is a leading provider of conformal coating materials, offering a range of coating types. Among these, the acrylic-based 1B31 stands out for its popularity due to its ease of application and protective qualities. Similarly, its urethane-based 1A33 provides reliable coating options for specific products.

Contrary to these two coatings, Parylene conformal coatings stand out as polymer-based substrate coatings. It delivers an ultra-thin, pinhole-free protection of exceptional durability, catering to various products such as printed circuit boards (PCBs) across aerospace, defense, automotive, commercial, industrial and medical industries.

HumiSeal 1B31 and 1A33

Among HumiSeal diverse roster of effective conformal coatings, acrylic 1B31 and urethane 1A33 are widely used. Both offer excellent protection against moisture, dust and other environmental elements that can potentially damage electronic components.

HumiSeal 1B31

Acrylic-based conformal coatings, such as HumiSeal’s 1B31, are commonly utilized. This rapid-drying solution minimizes heat emission during curing, safeguarding temperature-sensitive components, while attaining optimal physical properties within minutes. It also offers the following beneficial properties:

• Resistant to fungus and shrinkage
• Endures humidity during component operation,
• Exhibits low glass-transition temperatures,
• Easily removable for repair using solvent on the specific area
• Provides significant flexibility after application
• Fluoresces under UV light for easy inspection
• Allows soldering if needed

1B31 is commonly used as a conformal coating for PCBs to safeguard against moisture. It is MIL-I-46058C qualified, complies with IPC-CC-830 and RoHS Directive 2002/95/EC.

Like most conformal coatings, care must be taken to assure extreme cleanliness of the substrate so that no dirt, grease, moisture, residues or wax remain after application. Contamination beneath the coating can hinder the effectiveness of 1B31, resulting in product failure over time. The coating can be applied by brushing, dipping, spraying or automated robotic processes. Acrylics are typically applied at thicknesses ranging from 0.002” to 0.005”.

HumiSeal 1A33

Ideal for PCB applications, polyurethane HumiSeal 1A33 adheres to stringent professional product and performance standards. It is

• IPC-CC-830 and RoHS Directive 2011/65/EC compliant
• Qualified according to MIL-I-46058C stipulations
• Recognized under UL File Number E105698

1A33 supports reliable inspection, containing neither fluoresces nor free isocyanates.

Prior to applying 1A33, substrates must be meticulously cleaned. Any residual surface contaminants left on the substrate beneath the coating can significantly compromise its protective properties. Similar to acrylic 1B31, urethane 1A33 is administered through dipping, brushing or spraying methods. To adjust viscosity and ensure a uniform coating, HumiSeal Thinner 503 may be necessary.

Urethane 1A33 offers robust chemical and humidity resistance. Its two-component formula can achieve optimal curing in just one hour, although three hours is more common.

Parylene

Parylene’s properties differ significantly from both HumiSeal 1B31 and 1A33, surpassing them in terms of uses and capabilities. The ultra-thin, pinhole-free polymer coatings of Parylene offer valuable substrate-treatment properties such as:

• Application between .0001” and .002”
• Excellent chemical, dielectric and moisture barrier protection
• Dry-film lubricity
• Exceptional functional durability
• Thermal/UV-stability

The unique properties of Parylene make it an excellent coating choice for a wide range of applications such as aerospace, military, automotive, commercial, electronics, industrial, and medical devices. This coating is particularly well-suited for microelectromechanical (MEMS) and ruggedized products.

Parylene vs Humiseal

Parylene’s chemical vapor disposition (CVD) application process is the primary source of its functional advantages over either 1B31 and 1A33, which employ wet chemistry application. Solid-state raw Parylene dimer is heated between 100ºC – 150ºC and vaporizedExposure to high temperatures in a vacuum triggers dimer sublimation, breaking down the molecule into monomers that are meticulously deposited one by one onto the substrate. The result is a considerably more cohesive bond to the substrate.

When comparing HumiSeal’s acrylic 1B31 to Parylene, Parylene stands out for its superior resistance to solvents, high temperatures, and tin-whisker growth. In contrast to urethane-based 1A33, Parylene excels in vibration protection with a more flexible coating that offers reliable resistance to extreme vibrations like those experienced in aircraft or automobiles. Both HumiSeal’s 1B31 and 1A33 lack the heat resistance provided by Parylene. Parylene’s moisture protection matches that of either HumiSeal product, and its thinner coatings make it ideal for smaller assemblies.

Both acrylic and urethane conformal coatings have advantages. While 1B31 and 1A33 are easier and cheaper to apply initially compared to Parylene, Parylene’s adaptability and reliability offer long-term functional benefits. Its versatility across various product applications and ability to withstand harsh environmental conditions justify the higher production cost, providing durable conformal solutions.