Parylene is a conformal coating exhibiting extraordinary properties such as high mechanical strength and biocompatibility. It is a transparent (colorless) film in the UV-V is range of the solar spectrum (Parylene N and C absorb below ≈280 nm). The high transmittance of the polymers in the visible region (90%) make them eligible for use in optical applications. For further information on the optical properties of Parylene you can visit “Parylene’s Optical Properties and Performance”.

Multilayer conformal coatings are advantageous in resolving diffusion or stability issues. A vast amount of knowledge is available in the literature about the use of multilayered stacks of Parylene and stacks making use of different intermediate materials such as metals and so on. Mostly, use of Multiple layers of Parylene C was commonly reported for Medical Implants [1].

Under ambient conditions (room temperature, in air) Parylene is a lifetime conformal coating. The exposure to environmental stressors like temperature, oxygen, UV-light and chemicals can degrade the lifetime especially when two or more are existent at the same time.

Parylene is a chemically inert conformal coating [1]. It has a well-established chemical vapor deposition process and patterning methods. It is a great candidate for use in various application areas (health, aerospace, oil and gas, microelectronics, and so on.) due to its mechanical, physical, optical and chemical properties. Parylene is known to withstand highly corrosive environments and it can be utilized as a barrier material against various etchants in different processes (e.g. Hydrofluoric acid (HF), nitric acid, and acetic acid; potassium hydroxide; and tetramethylammonium hydroxide).

At Diamond MT we often get the question: “Can my xxx be parylene coated?”  The number of substrate surfaces that can be coated with parylene is plenty. In the table below a number of industrial applications that using Parylene conformal coatings are listed. The examples can be extended.

The stability and insulation property of Parylene conformal coating is critical for the reliable operation of electronic devices throughout their lifetime (PCBs, MEMS, sensors, implants and so on.). The failure mechanism of the conformal coating layers is known to be due to pore formation, blistering, delamination and thinning or pinhole formation due to dielectric breakage of the coating over time [1], [2]. Therefore, the surface where the interface between the conformal coating and the substrate will be formed is of high importance. The cleanliness of this surface has a great impact on the final results of the conformal coating process and the coatings durability. At Diamond MT we provide professional surface cleaning services ensuring the long lasting results for your components. Also, the parylene conformal coating thickness and parylene varieties required for different service are considerations to take into account. We offer our professional services to direct our customers. Some of the variables of different service conditions can be listed as:

Parylene XY is a transparent, thin (hundreds of nanometers to a few micrometers), well adhering, pin-hole and defect free conformal coating. They are coated uniformly on flat surfaces and component configurations with sharp edges, points, flat surfaces, crevices or exposed internal surfaces are coated uniformly without voids.

Oil & Gas industry makes use of sensors which face extremely high temperature and high pressure (HTHP) environments as in downhole drilling (>200°C and 30 kspi). In US natural gas supply lie in reservoirs below 15,000 ft. Wells at these depths pose environmental challenges of drilling due to the temperature, pressure and gasses. Increasing the lifetime of drilling equipment and possibility for recalibration of sensors that drift at such depths would save millions of dollars if they can be preserved under these HTHP environments. The packaging of sensors is a key element in providing this kind of protection.

Poly(para-xylylene) derivatives (parylenes) are used as conformal coatings in a wide range of applications in the automotive, medical, electronics, military and semiconductor industries. They are inert, transparent and have excellent barrier properties as dielectric thin films. Because their deposition takes placeunder vacuum sub-micron range crevices can be coated leading to excellent barrier properties (void free) and they have extraordinary purity that is of great importance in electronic applications. Not all parylene derivatives show same dielectric properties (Table 1). It is also important to note that dielectric properties of parylenes depend on their thickness thus their %crystallinity which is explained below.

The answer is “No!”