Wire Wound Devices

• magnets
• wire wound ferrite cores
• powdered ferrite cores

Parylene was originally developed to protect printed circuit boards from salt spray and high humidity applications. Several new markets and applications were found where the traditional spray or dip coatings were not able to perform to spec.

One of these new application areas was the wire wound device market. Parylene uses a vapor deposition process performed in a vacuum. This process gives certain advantages over other common coating techniques such as spraying, dipping or brushing. Parylene is a gaseous monomer which builds from the surface outward. This produces a pinhole free (pinhole free @ .6 micrometer or higher) conformal layer of uniform thickness. Surface tension causing the pulling away of sharp edges, bridging or thin out when conventional coatings are used in the curing process does not occur with the parylene process.

Parylene coating is a batch process where parts are put into a chamber, either horizontal (tumbler) or vertical. The components in the chamber are at or near room temperature. There is no need for a high cure temperature cycle, thus there is no thermal or mechanical stress. When the coating process is finished and the specified thickness is achieved, the parts are ready.

Along with a low temperature no cure process, parylene offers outstanding insulation and high dielectric constant properties over a wide range of frequencies. Parylene also eliminates abrasion damage to the wire in the winding process along with uniform coating thickness. Unlike the variance of thickness (bridging, shrinking, thin out and pinholes) with conventional liquid, spray or brushed on coatings, parylene gives a maximum winding window.

Parylene does not impart magnetostrictive or permeability problems that may be encountered with conventional varnish impregnation.

With parylene’s low water vapour transmission properties it provides excellent corrosion protection. Again, because parylene is a batch process where many parts can be coated at a time in a tumble system, parylene offers a cost effective solution for many applications.

See Technical Information for details.

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