Parylene vs. Urethane Conformal Coatings: Here’s What You Need to Know

Electronic devices are highly sensitive to many environments. Moisture, static, and vibrations may damage unprotected electronics. That’s why engineers apply a conformal coating to circuit boards and other components. There are two main types of coatings available for these purposes, but which one is the best for your application? Here’s everything you need to know about the most popular conformal coatings before making a decision.

What Are the Most Common Coatings?

Conformal coatings are vital in the world of electronics. When applied, these coatings become one with the device and offer superior protection. Engineers often find themselves deciding between parylene conformal coating (PCC) and urethane conformal coating (UCC). While both of these materials serve a similar purpose, they are vastly different from one another.

PCC is a robust polymer that was first discovered in 1947. Since then, it’s been used in a variety of applications, including automotive, electronics, and aerospace. It’s also FDA approved and used on medical implants. Those who choose PCC over other options do so because of its reputation for being durable and long-lasting. It creates an extremely thin film layer and doesn’t add any bulkiness to items.

Different types of urethane have been in use since the 1930s. Similar to PCC, urethane also creates a very durable and reliable barrier. This material is most commonly used on electronics. FDA approved urethane is also used in the food service industry. Although it’s thicker than other coatings, it’s believed that the added volume provides an additional layer of protection.

How Are PCC and UCC Alike?

Since both PCC and UCC are used in similar applications, it’s safe to assume they share some characteristics. However, these similarities are not always beneficial. For example, it’s difficult to remove and alter both coatings. PCC, in particular, is impervious to chemicals. Removing this durable coating often requires the use of micro-abrasion tools that gradually break down the surface. Removing urethane with strong chemicals is easier, but it’s still resistant to many solutions. Relying on mechanical reworking techniques is often necessary.

Both materials also have heat thresholds. Urethane can withstand temperatures up to 125-degrees Celsius, while PCC has a temperature rating of around 80-degrees Celsius. These limits don’t pose a problem in most applications, such as on circuit boards. However, the heat of an oven or engine may prove too hot for these coatings. Extremely cold environments may also reduce the effectiveness of both materials.

PCC and UCC do share a common benefit. Both of these materials slow down the formation of tin whiskers. Although there is still much to learn about this crystalline phenomenon, these whiskers can pose a threat to electronic devices. Luckily, these common conformal coatings create a thick enough layer to protect tin surfaces and reduce the risk of short-circuiting.

How Does the Application Process Differ?

The deposition and curing method for PCC is more complicated than urethane. This coating uses vacuum deposition, which requires highly specialized equipment to vaporize the material. Once vaporized, it’s applied in a vacuum. The length of the process takes depends on the desired thickness of the finished product. However, PCC doesn’t need to cure because it’s not a liquid. PCC is dry and ready for use as soon as it’s applied to the substrate

Depositing urethane, however, is a much simpler process. It’s a liquid coating, and most people choose to brush it on the desired item. Other application methods include dipping and spraying. Since urethane is wet, it must dry fully before use. Even if the surface feels dry to the touch, more time is needed to ensure the entire coat is cured. It can take several hours or days for urethane coatings to cure completely.

What Is the Durability of Each Coating?

Effective coatings must not only provide an airtight seal, but they also need to be highly durable in a range of environments. PCC and UCC vary when it comes to hardness. Since PCC is thinner, it tends to be more flexible. This added flexibility helps PCC perform better under intense vibrations. UCC is much harder, and while that may seem like an advantage, it also makes the coating more brittle and likely to crack under vibration.

However, hardness does give urethane a major advantage when it comes to abrasion. Even under extreme circumstances, urethane can resist more abrasive wear. Although PCC can withstand abrasive forces, this somewhat softer coating doesn’t compare to UCC. Before settling on a specific coating, it’s best to consider how much contact the item will have with intense vibrations or abrasive settings.

Is There a Price Difference?

Budget also plays a significant role when deciding between PCC or UCC. In most cases, urethane is a more affordable coating option. However, it’s not wise to select this material if the substrate will be exposed to vibrations. It’s also not a good choice if you require an extremely thin coating. When picking out a coating material, price shouldn’t always be the deciding factor. Instead, it’s better to weigh the pros and cons of each material before even considering the cost.

Although you should keep a budget in mind, selecting the wrong coating now may prove more costly down the road. For example, if you choose urethane but then expose the device to high vibrations, you may end up reworking the coating sooner than desired. On the contrary, spending more money on PCC isn’t a wise option if abrasive wear is a concern. Always consider device usage and the environment before making a final decision.

Which One Is the Best Choice?

Does it matter which coating you select for your electronics? Many people assume these materials are interchangeable, and while that does hold some truth, it’s not always the case. Both PCC and UCC make excellent coating choices; however, your specific application will determine which one is best. While it may not be easy to decide on which material is right for you, a coating expert can lead you in the right direction. With proper application and maintenance, you can expect a conformal coating to last for the lifetime of most devices.

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