Parylene and Tin Whiskers

Tin whiskers have long been a frustrating occurrence for those manufacturing and using electronic devices. First discovered in the 1940s, the whiskering of metal has been the cause of serious problems, including the damaging of vital and difficult to replace equipment. Finding ways to prevent or slow the growth of whiskers has been a focus of engineers and scientists for quite some time.

What are Tin Whiskers?

The exact mechanism behind the development of tin whiskers is not fully understood. However, the growth of these whiskers is believed to be encouraged by mechanically and thermally-induced stresses. Over time, the tin solder used to assemble electronics will begin to “grow” tiny hair-like appendages. These growths are known to cause short circuits and arcing which can result in devastating damage to electrical devices. Tin whiskers have been responsible for damaging vital equipment including pacemakers, power plants and even satellites.

How Can Tin Whiskers be Prevented?

Mitigating tin whiskers is necessary to ensure the durability and reliability of electronics. In the past, lead was used instead of tin to avoid whiskering. While still prone to whiskering, lead is known to greatly reduce the growth rate of whiskers. However, using lead in manufacturing has its drawbacks. Lead is a highly toxic heavy metal, and its use in electronics poses a grave health risk. As such, the use of lead in consumer products is restricted in many places, including an almost outright ban in the European Union. Without the use of lead, electronics manufacturers have had to turn to alternative methods to mitigate tin whiskers. Perhaps the most effective method discovered thus far is Parylene coating.

How Does Parylene Coating work?

Parylene helps mitigate tin whiskers when used in a process known as conformal coating. This process protects circuitry from environmental hazards like water, dust and temperature cycling. Parylene is one of the only coatings that prevents water molecule penetration. Conformal coating creates a barrier to prevent tin whiskers from damaging equipment by physically separating components. This prevents whiskers from bridging components and causing shorts. While whisker growth cannot be entirely prevented, Parylene significantly slows it down and prevents equipment damage. Traditional materials like acrylic, silicone, and urethane are ineffective against whiskering, unlike Parylene.

What Benefits does Parylene Coating have Over Alternatives?

The primary benefit of Parylene coating is avoiding toxic heavy metals like lead. Additionally, Parylene has unique properties that make it ideal for electrical equipment use. These properties include:

• Uniform thickness, which protects the entire substrate evenly
• Room temperature, stress-free application
• Transparency, allowing use with optical elements
• FDA Approval
• High tensile strength
• Stability in a wide range of temperatures

Where can Parylene Coating be Applied?

Tin whiskering is a universal occurrence in electrical equipment. The phenomenon is not confined to certain industries or sectors. Whiskering has been observed in a wide range of applications including aerospace and defense products, consumer and industrial electronics and medical equipment. Manufacturers want products not only to be of high quality and durable, but safe for use. Parylene fulfills this need perfectly. If you’re looking to protect electronics in harsh conditions, Parylene is a highly versatile and durable coating.

Why Use Parylene?

Parylene coating is the simple solution to a complex problem. The exact causes behind tin whiskers are still not fully understood and their complete elimination is not yet possible. However, Parylene coating provides one of the most effective and safe ways to mitigate this unfortunate phenomenon. Parylene is safe for use, poses no health risks, is extremely versatile, and has shown to be extremely effective at reducing the growth of tin whiskers and preventing penetration.