Cost of Parylene Dimer

Perhaps the most reliable of the conformal coatings, the cost of applying Parylene coatings (poly para-xylylene) varies depending on labor requirements (e.g., cleaning, masking, application, demasking, inspection, etc.), raw material costs and batch size (number of parts to be coated at one time).

Parylene CVD and Dimer Requirements

The Parylene chemical vapor deposition (CVD) process is unique and generates one of the most reliable conformal coatings for an abundance of products and purposes. The CVD process causes a gaseous monomer to seep deep within the substrate surface, producing a micro-thin protective film of exceptional durability. However, Parylene does not start as a vapor; it begins as a solid state dimer material (di-para-xylylene) that is transformed into a gas during CVD.

A chemical compound in powder form, dimer is the essential ingredient of Parylene conformal coatings. During CVD, the dimer undergoes pyrolysis while under vacuum in a Parylene deposition system where the dimer is transformed from a solid state into a monomeric vapor. Gaseous monomer polymerizes at a very low pressure and becomes a structurally continuous film that entirely conforms to the physical configurations of the substrate’s surface. Polymerization occurs at near-room temperature to create the Parylene coating.

In addition to completely uniform, pinhole-free coverage, Parylenes typically provide exceptional resistance to solvents and moisture as well as incredible dielectric strength. Not all Parylenes are equal; while all share exceptional barrier properties; each type has a distinct set of coating properties compared to one another. Parylenes C, N, D and Parylene HT^® are among the most frequently used Parylene types. Other variants are also available; their selection and use depend on the specific coating assignment.

Dimer/Project Costs

Required coating thickness factors into the kind of Parylene dimer used and its quantity. Regarding cost, the amount of dimer needed to produce the required film thickness across the assembly needs to be carefully calculated for optimal results. This issue emerges because Parylene can be effectively deposited in thicknesses ranging from angstroms to well over 2 millimeters. Determining a project’s required thickness helps ensure application of the correct dimer quantity and, therefore, determines the raw material expense to the client/manufacturer. Each of the different types of dimer has its own associated manufacturing processes and, thus, costs as well.

Different projects and their diverse assembly/component functions are best served by different types of Parylene coating, depending on a host of variable properties, including dielectric strength, the degree of barrier protection and temperature limitations. Depending on the coating type and required thickness to achieve the desired properties, typical Parylene deposition rates range between 1 and 5 microns per hour; therefore, coating runs can vary from as little as 1 hour for small production batches to over 24 hours for larger-scale projects.

In summary, selecting the appropriate Parylene type is paramount to successful coating. Saving money on dimer cost by opting for a dimer variant just because it is less expensive, for example, is never recommended. The resulting Parylene film could malfunction or perform well below standard, leading to assembly breakdown. The Parylene type chosen should be based on the properties required and ultimately tested on the substrates to ensure functionality. Attention should also be paid to who manufacturers the raw material and what quality management systems and/or certifications they achieve.