Specialty Coating Systems discusses the benefits of using Parylene conformal coatings to protect Printed Circuit Boards (PCBs) and related electronic assemblies.
Because each conformal coating material has its unique strengths, selecting the right one for a particular application often depends on the specific environment where the product is to be used.
Parylene conformal coatings provide dependable protection for Printed Circuit Boards (PCBs) and related electronic assemblies. They safeguard components from contaminants, corrosion, dust, fungus, moisture, salt spray, temperature extremes and, in the case of implantable medical devices, bodily fluids.
Commercial Off-The-Shelf (COTS) assemblies and devices have been increasingly used for military and defense purposes. Although COTS electronics were generally not designed for defense applications, escalating budgetary constraints within the Department of Defense have combined with increasingly stringent Restriction of Hazardous Substances’ (RoHS) directives to encourage their use. The exclusive ‘custom design’ that typified most military devices in the past has been modified for COTS-adaptation for many non-critical products.
Product Ruggedization
Ruggedized products are designed to ensure superior performance during harsh operating conditions, including extreme temperatures, material intrusions of dust, rain, soot, water or wind, and persistent, intensive vibrations both within and external to the device. Because of the unusual, punishing performance ecosystems that characterize operational expectations, internal components require ruggedization to safeguard their installed electronics. Protecting delicate, finely-tuned components requires conformal coatings of exceptional performance durability and versatility. For over 50 years, Parylene conformal coatings have been chosen and repeatedly specified by military organizations as they provide exceptional protection for ruggedized applications.
In addition to military embedded systems utilized for extended duration for in-field and on-site service, rugged devices have demonstrated reliable functionality for aerospace computing, emergency healthcare/public safety situations and specialized scientific research or undersea/arctic exploration and surveying. These represent a range of operational environments characterized by exceptional compression/stress, radical changes in temperature and variable atmospheric conditions where components and devices require specialized, in-depth protection. The resistance to harsh working environments provided by Parylene conformal coatings supports functionality where unprotected devices would otherwise fail. Parylene coatings are:
- RoHS-compliant
- Meet IPC-CC-830 requirements
- Listed on the Defense Supply Center Qualified Parts List (QPL) for MIL-I-46058
COTS components adapted for military purposes must meet the specifications of MIL-STD-810F, which stipulates performance standards in response to the impact of artillery/gunfire, extreme acceleration and the presence of contaminants ranging from shrapnel to blood, fungus to salt fog. The MIL-STD-810F spec details procedures for testing a device’s capacity to function in critical environments, including:
- Generate a uniform, bubble-free conformal film
- Withstand vibrations
- Provide excellent barriers against biological, chemical, and moisture agents
- Suppress the formation of metallic whiskers
- Support MEMS and nano technologies
- Strengthen delicate PCB leads and connections by a factor of 10
- Provide high dielectric strength
- Offer mechanical/physical properties that support resistance to environmental tremors, jarring vibrations and natural or man-made disasters
Further, Parylene-ruggedized COTS electronics withstand alterations in altitude and interference generated by magnetic properties or radio frequencies. Approved as a military-spec conformal coating, Parylenes enhance the integrity of ruggedized devices while retaining the device’s functional capacity throughout exposure to these conditions.
Designed to withstand harsh environments, ruggedized products are increasingly numerous. They are manufactured to meet challenging performance standards for industrial, defense, aerospace and commercial applications. Parylene coatings are listed on the QPL and have been used for over 50 years in military and aerospace applications for custom devices; they can also enhance the integrity of COTS devices without adding significant weight or prohibitive cost.
