This guide covers parylene coating benefits for neodymium magnets.
Learn how it provides corrosion resistance and thermal stability.
Discover the essentials of parylene coating.
If you use neodymium magnets, this is essential reading.
Let’s explore how parylene coatings enhance neodymium magnets.
Why Parylene for Neodymium Magnets
With Parylene coatings, you can protect your electronic devices from those risks.
Parylene for electronics in harsh environments has benefits such as:
Biocompatibility
The Food and Drug Administration (FDA) has approval for medical devices containing Parylene coatings.
- The coatings comply with USP Class VI Plastics requirements.
- And they are MIL-I-46058C / IPC-CC-830B listed.
Conformity
Properly applied parylene coating is pinhole-free with uniform controllable thickness greater than 0.5 micrometers to 1 millimeter on any surface or design.
Durability
The formation process ensures lightweight, protective performance over time.
Parylene has high-quality barrier, physical and electrical properties.
Stability
Parylene coatings can handle very hot and very cold temperatures without breaking down.
- The coating won’t peel, crack, or lose effectiveness between -200°C / -328°F and +200°C / 842°F.
Stress-free
Parylene coats at room temperature, avoiding thermal stresses that could compromise adhesion or accelerate cracking.
The stress-free formation preserves coating integrity and prolongs protective function.
Inert and stable
Parylene is totally chemically inactive.
- Harsh chemicals cannot react with or break down the coating.
- This inertness provides an impermeable shield against corrosion, even in acidic or caustic environments.
Parylene also resists molds, bacteria, and other biological growths that could degrade the coating.
- As an inert barrier, Parylene isolates and protects the magnet surface from external threats like moisture, chemicals, dirt, and microbes.
- Users benefit from Parylene’s unrivaled environmental stability and longevity across a broad range of conditions.
Protectablity
Parylene coats even 0.01mm cracks on neodymium magnets, fully encapsulating the porous surface. This seals vulnerable gaps thoroughly against corrosion, maximizing magnet longevity. The complete, void-free coating provides comprehensive protection.
6 Types
There are several types of parylene coatings available in the market.
Each with different chemical structures and characteristics.
Generally, they have 6 common types and we’ve listed some brief intro below.
Parylene N
This is the simplest and original form of parylene, consisting of only carbon and hydrogen atoms.
- It has the highest dielectric constant, the lowest dissipation factor, and the best high-frequency properties among all parylene types.
- It also has good vacuum stability and gas permeability.
- Parylene N is suitable for applications that require high electrical performance, such as circuit boards, sensors, and antennas.
Parylene C
This is the most widely used type of parylene, accounting for about 80% of all parylene applications.
It has a chlorine atom attached to the benzene ring of each molecule, which makes it more resistant to moisture, chemicals, and corrosive gases than parylene N.
It also has a lower dielectric constant and dissipation factor than parylene N, which improves its electrical insulation.
Parylene C is suitable for applications that require protection from harsh environments, such as medical devices, aerospace components, and automotive parts.
Parylene D
This type of parylene has two chlorine atoms attached to the benzene ring of each molecule, which makes it even more resistant to moisture, chemicals, and corrosive gases than parylene C.
It also has the highest thermal stability among all parylene types, being able to withstand temperatures up to 125°C.
However, it has lower biocompatibility and higher dissipation factor than parylene C, which limits its use in some applications.
Parylene D is suitable for applications that require high temperature resistance, such as LED lights, solar cells, and power supplies.
Parylene F
This type of parylene has two fluorine atoms attached to the alpha carbon of each molecule, which makes it more stable against UV radiation and oxidation than parylene HT.
It also has a lower dielectric constant and dissipation factor than parylene HT, which improves its electrical insulation.
Parylene F can withstand temperatures up to 450°C, making it the most thermally stable type of parylene.
Parylene F is suitable for applications that require exposure to high-energy radiation or extreme temperatures, such as satellites, radars, and lasers.
Parylene HT
This type of parylene has a fluorine atom attached to the alpha carbon of each molecule, which makes it more stable against UV radiation and oxidation than other parylene types.
It also has the lowest dielectric constant and dissipation factor among all parylene types, which enhances its electrical insulation.
Parylene HT can withstand temperatures up to 350°C, making it the most thermally stable type of parylene.
Parylene HT is suitable for applications that require exposure to high-energy radiation or extreme temperatures, such as satellites, radars, and lasers.
Parylene AF-4
This type of parylene has a fluorine atom attached to the benzene ring of each molecule, which makes it more hydrophobic and oleophobic than other parylene types.
It also has a very low coefficient of friction and a high optical clarity.
Parylene AF-4 is suitable for applications that require lubricity or transparency, such as catheters, lenses, or optical fibers.
When to use
Parylene coatings can be a suitable option for neodymium magnets in certain conditions.
Here are some situations where Parylene coatings may be appropriate:
Medical and dental applications
Parylene coatings are commonly used to protect neodymium magnets in medical and dental applications, particularly when the magnets will be used intra-orally.
Corrosion resistance
Parylene coatings provide excellent resistance to moisture and chemicals, making them suitable for use in harsh environments where corrosion is a concern.
Conformal coverage
Parylene coatings offer excellent conformal coverage, meaning they can coat complex shapes and surfaces uniformly.
Electrical insulation
Parylene coatings have excellent electrical insulation properties, making them useful for applications where electrical insulation is required.
It’s worth noting that the durability of Parylene coatings can be influenced by various factors, including the specific application, environmental conditions, and proper application techniques.
Advantages over PTFE
Parylene offers advantages in terms of durability, conformal coating capabilities, chemical resistance, and electrical insulation.
Application Flexibility
Parylene is often a better choice due to its application-specific considerations.
It offers more flexibility in terms of its suitability for various applications.
Crack and Wear Resistance
Parylene tends to have better resistance against cracking and wear compared to PTFE.
This makes it a more durable option, especially in environments where mechanical stress or friction is a concern.
Conformal Coating
Parylene is a conformal coating, meaning it can uniformly cover complex shapes and surfaces with a thin, pinhole-free film[6]. This makes it suitable for protecting delicate electronic components and ensuring proper performance.
Chemical Resistance
Parylene exhibits excellent chemical resistance, making it suitable for applications where exposure to harsh chemicals or solvents is expected.
It can provide a protective barrier against corrosive substances.
Electrical Insulation
Parylene is an exceptional electrical insulator[5]. It is commonly used in the manufacture of printed circuit boards (PCBs) and electrical cables, where it provides insulation and protection against electrical shorts.
According to our experience and simulated tests, the choice between Parylene and PTFE depends on the specific requirements of the application.
- PTFE may have a lower coefficient of friction.
Recommended Applications
Here are some specific applications where Parylene is good choice.
Medical Devices
Parylene is commonly used to coat medical devices such as coronary stents, probes, needles, catheters, and hearing aids.
It is a biocompatible material that can provide a protective barrier against bodily fluids and other contaminants.
Electronics
Parylene is an excellent electrical insulator and is commonly used in the manufacture of printed circuit boards (PCBs) and electrical cables.
It can provide insulation and protection against electrical shorts.
Industrial Applications
Parylene is a conformal coating that can uniformly cover complex shapes and surfaces with a thin, pinhole-free film.
This makes it suitable for protecting industrial components such as bearings, pipe liners, valves, pumps, and sealing components.
Chemical Resistance
Parylene exhibits excellent chemical resistance, making it suitable for applications where exposure to harsh chemicals or solvents is expected.
It can provide a protective barrier against corrosive substances.
High Temperature Applications
Parylene can be used in high-temperature applications up to 450°C.
It is useful in applications where long-term UV stability is required.
Common quality issues
Some frequently occurring coating problems that can occur if Parylene is not properly applied are as below.
Bubbles
These are air pockets or voids that form within or under the Parylene coating, creating an uneven or rough surface. Bubbles can affect the smoothness, uniformity, and quality of the coated product. Bubbles can be caused by moisture, air, or solvents trapped in the coating during the curing process, or by overheating or overcuring the coating.
Moisture diffusion
This is when water molecules penetrate through the Parylene coating and reach the substrate, causing corrosion, oxidation, or degradation of the coated product. Moisture diffusion can affect the electrical insulation, chemical resistance, and mechanical strength of the Parylene coating. Moisture diffusion can be influenced by the environmental humidity, temperature, pressure, and exposure time.
Pinholes
These are small holes or gaps in the Parylene coating that expose the substrate to the environment. Pinholes can increase the risk of corrosion, oxidation, or contamination of the coated product. Pinholes can be caused by dust, dirt, or foreign particles on the coating surface, or by insufficient coating thickness or coverage.
Checklist
- Dimension of the neodymium magnets? Length, width, and max thickness?
- What are the intended applications of neodymium magnets to be Parylene coated?
- What is the thickness of Parylene coatings required?
- What is the working temperature for the magnets?
- What are the tests to comply after the neodymium magnets are Parylene coated?
- What is the end applications of the magnets?