Conformal coating protects wind power electronics

To create a self-sustainable environment, it is imperative to reduce our reliance on fossil fuels for power generation. Government agencies, power suppliers, and consumers are all turning to renewable energy sources to meet this goal. Electricity generation is a key technology that is rapidly growing in demand, and wind power is becoming a major source for clean, renewable energy. The American Wind Energy Association (AWEA) says this soaring demand has spurred expansion of wind-turbine manufacturing in the United States.

 

Wind turbines come in many sizes and configurations which are unique to each manufacturer. However, regardless of proprietary designs, almost all wind turbines contain up to 8,000 parts. These parts include gearboxes, power systems, generators, sensors and electronic control, and power systems. All must be produced, assembled and maintained for long-life and trouble free operation. These and other components are typically housed in the nacelle, which is mounted on the tower, and must be able to withstand and operate with constant vibration, temperature extremes, environmental conditions (land or offshore), and limited accessibility.

 

 

Moving Into New Electronics and Automation

 

Photo of SCS Parylene coated (top) and non-coated(bottom) boards after testing in salt-fog environment

 

Most electrical/electronic control and monitoring systems in wind turbines are housed in an IPC-rated electrical cabinet for a certain level of protection. There are still issues with moisture however, and its effects on components within the nacelle. Previously when electronics failured the industry tended to simply replace the faulty component without determining a root cause. As the complexity of systems increases and the number of installations continues upward, wind turbine manufacturers are seeing that swapping components is simply not a cost-effective policy. Thus today, manufacturers are expanding the use of sensors in wind turbines to monitor component operation and performance to better understand and identify potential failures — before they occur.

 

To remain competitive, manufacturers and operators must improve the design and operation of turbines to bring down total operating costs and deliver power at competitive rates. The goal, as with all renewable energy sources, is grid parity or less. Also, as manufacturers increase the number of turbines in the field, they must continue to drive down their manufacturing costs. Part of a manufacturer’s strategy must be to provide components that last longer, thus reducing warranty and replacement costs. If manufacturers begin protecting their electronics systems with Parylene conformal coatings, they will increase component life, thus reducing the frequency of maintenance and long-term cost while achieving maximum hours of power generation.

 

The wind turbine market offers challenges similar to those already in the harsh environments of aerospace, military, and automotive applications. Recent industry research confirmed that 52% of wind-turbine failures are related to electronics. This includes everything from circuit boards to component monitoring electronics and various sensors inside and outside the nacelle. Sensors outside may determine the pitch of a blade, sensors inside tell computers on the ground (and operators) whether or not the turbine is generating power and why

 

 

Understanding Parylene

 

Recognized as excellent conformal coatings for harsh environment applications, the family of Parylene coatings provides an inert, pinhole-free conformal coating that is applied in a room temperature, vapor-phase deposition process.

 

Parylene coatings are typically applied in thickness ranging from 500 angstroms to 75 microns. A 25 micron coating, for example, has a dielectric capability in excess of 5,000 volts. No other conformal coating materials can be applied as thinly and uniformly as Parylene and still provide the same level of protection. An added benefit of Parylene is that it can actually strengthen delicate wire bonds by an estimated factor of 10, providing excellent durability where vibration is present.

 

Parylene coatings grow one molecule at a time through the vapor deposition process. The deposition chamber and items to be coated remain at room temperature throughout the process. Additionally, there are no solvents, catalysts, or plasticizers used in the coating process and no cure forces are are required. Because there is no liquid phase in this deposition process, there are no subsequent meniscus, pooling, or bridging effects as seen in the application of many liquid coatings. As a result, dielectric properties are never compromised.

 

The polymerization process and ultra-thin nature of Parylene let it to conform to all surfaces, edges and crevices of a substrate, including the interior of multi-layer electronic packages and PCBs. This assures complete encapsulation of the substrate without blocking or bridging even the smallest openings. In addition, Parylene coatings are lightweight and do not add significant mass or dimension to delicate components.

 

SCS Parylenes are applied as a vapor in a vacuum deposition process

 

 

Parylene Variants

 

Illustration of liquid coating and Parylene coating

 

Many properties are similar between Parylene variants. All Parylenes provide excellent barriers for moisture, chemical and biological agents and because they are applied by vapor deposition, where the coating molecules basically “grow” to an ultra-thin barrier completely covering all components, they create minimal added weight. Parylenes actually strengthen, by 10x, delicate leads and connections. This gives excellent durability wherever vibration is present. Additionally, Parylene coatings are RoHS compliant and have been shown to suppress the formation of metallic whiskers in lead-free solder applications.

 

As a result of Parylene’s vacuum deposition process, there is no potential for the trapping of air bubbles in or under the coating unlike coatings that are sprayed, dipped, or brushed on. When air bubbles are present and the component is subjected to harsh environments, voids have the potential to open and expose the component to the environment … and a possible short circuit.

 

 

Helping Wind Technology Grow

 

Wind-turbine technology will need to evolve to meet the projected goal of 7,000 installations per year in 2017. As the number of installations increase, engineers will need to make all wind turbines more reliable to reduce service calls and maximize output. This is true whether they are built to meet the larger, taller, and more robust designs needed for major wind farms, or designed to fit into the latest paradigm of smaller, uniquely configured rooftop systems. Parylene coatings are well-suited to play a role in providing long-term reliable protection to sensors and electronic components as added protection allows turbines to enjoy long, trouble-free life and lowers the overall maintenance and operational costs to manufacturers and the end user.