Conformal coatings are used to protect printed circuit boards (PCBs) from dust, humidity/moisture, mildew/mold, temperature extremes, and other elements whose prolonged contact might interfere with assembly function. Coatings also enhance electrical clearance-tolerance, while safeguarding PCB components from contamination (particulate or otherwise), corrosive materials, and mechanical stress.Read More
Parylene Coating Blog by Diamond-MT
Selecting a suitable conformal material for coating printed circuit boards (PCBs), related electronics, or other devices requires recognition of each coating type’s unique combination of benefits and drawbacks. These must be considered in relation to a given application.Read More
If, for some reason, you are told parylene is NOT a conformal coating, simply because it has no liquid phase of application, just walk away. And maybe have yourself a good laugh. For, as you may already know, parylene has repeatedly proven itself to be the most definitive of conformal coatings, for a variety of reasons, including:Read More
Application methods must first reflect the targeted substrate’s susceptibility to the coating material. Liquid coatings – acrylic, epoxy, silicone and urethane – each possess specific performance properties. Optimal protection and operational efficiency depend onRead More
Printed circuit boards (PCBs) electrically connect and power all but the simplest electronic products. To function as designed, PCBs and their components – capacitors, resistors, etc. – require protection against operating problems caused by corrosive liquids, dust, physical shock, temperature extremes and, in the case of medical implants, bodily fluids. Conformal coatings are applied over PCBs to safeguard mechanisms and maintain functionality.Read More
Conformal coatings insulate printed circuit boards (PCBs) and similar electronics; their protection increases devices’ tolerance to harsh environments. The result is undisturbed function through a range of frequently harsh operating environments and performance conditions. Conformal coatings provide these services for aerospace/defense, automotive, consumer, and medical devices. They are adaptable for LED uses, as well as MEMS/nanotechnology, and other uses.Read More
The conformal coating process requires watchful administration to ensure successful implementation. Recognizing the unique properties of various coating-types is critical to selecting the kind most applicable to the project and its purposes, while meeting clients’ material and operational specifications. Regardless of the coating material and the substrate, these five fundamental procedures are essential to good conformal films.Read More
Managing the conformal coating process begins with a precise definition of coverage required. Pre-process negotiations between the client, the coating provider, and end-user, clarify coating requirements. They include agreement about whether:Read More
Liquid application resins acrylic, epoxy, silicone and urethane are applied to electronic circuitry in a liquid format by brush, dip or spray techniques, either manually or through robotic processes; they require curing before they can be used.Read More
Masking tapes and boots both protect components for a selected range of masking functions. Choosing between the two is crucial to achieving optimal masking protection. Conductivity needs to be maintained in all cases. In addition, such operational factors as the:Read More
Understanding the characteristics of various conformal coating types, and their interactions with the extreme range of products and materials to which they are applied, ensures optimal function, performance reliability and product-life. Designers and users of conformal coatings should be aware of the properties of various types of conformal coatings and their interactions with the parts/materials they cover, to protect the products in their respective end-use environments for the expected design-life of each component.Read More
The National Aerospace and Defense Contractors Accreditation ProgramRead More
Printed circuit boards are extremely susceptible to a wide range of contaminants that can significantly damage or ruin them in a relatively short period of time. These contaminants include moisture, dust, and harmful chemicals. In addition, electronic circuits are also susceptible to extreme temperatures and environments.
Type AR (acrylic resin) conformal coatings are a popular choice for conformal coating projects because of their moisture protection, low cost, and ease of application. There are many different varieties of type AR conformal coatings such as:
Nexus3C, the Conformal Coating Centre, have arranged a program of workshops and conferences over the next twelve months across North America, Asia and Europe for users of conformal coating.
- HumiSeal 1A33
- HumiSeal 1A20
- Humiseal 1A27
- Humiseal 2A64
- HumiSeal 1A34
- Hysol PC18M
- CONATHANE CE-1155-35
- CONAP CE-1170
- CONATHANE CE-1164
- Techspray Fine-L-Kote
- MG Chemicals 4223
- Electrolube PUC
You should consider using type ur conformal coating whenever your application has any issues with chemical resistivity as type ur coatings are very resistant to chemical solvents. Type ur conformal coating is also smart to include in any tin whisker mitigation strategy, as NASA studies have shown that urethane conformal coatings are one of the few ways to successfully mitigate tin whisker growth. Finally, applications that can see any direct mechanical wear against the coating should consider urethane conformal coatings as well.
Tin whiskers are electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin (especially electroplated tin) is used as a final finish. They typically grow from lengths of 1-2 millimeters (mm) but have been observed to lengths in excess of 10 mm. They are a serious issue in the electronics world because they have been known to cause short circuits between circuit elements.
NASA-STD 8739.1 is the Workmanship Standard for Polymeric Application on Electronic Assemblies, which describes NASA’s technical requirements, procedures, and documenting requirements for staking, conformal coating, bonding, and encapsulation of printed wiring boards and electronic assemblies. Included are requirements which establish the responsibility for documenting, fabrication, and inspection procedures to be used for NASA work including supplier innovations, special processes, and changes in technology. NASA-STD 8739.1 was initially released in August of 1999, with improvements and minor changes to the standard in recent years. The current up-to-date revision is NASA-STD 8739.1A with Change 2.
Stripping or removal of unwanted conformal coating from a printed circuit board (PCB) can be a relatively simple process or a very messy difficult job. It does depend on several factors including the type of conformal coating you need to remove, where the coating is found and the type of components on the board.
The Conformal Coating Standards that currently exist can be considered from two points of view. First, there are the standards that are used by the manufacturers of conformal coatings to qualify the products, whether that is done by self-certification or completed by independent testing. Second, the standards are a method for users to determine the quality of the conformal coatings they are considering to select.
Last time, we discussed the general requirements necessary to open a conformal coating facility. Now I will discuss the equipment that is required in order to have a properly operating facility.
Conformal Coatings are used regularly in an attempt to cover technology designs on printed circuit boards (PCBs). Normally, this is done by using a pigmented (coloured) conformal coating which obscures the components below the conformal coating material.
One thing to consider is the coating house’s experience level. Developing solid procedures and processes for conformal coating take time and experience. Many new vendors claim to be able to apply conformal coating as well as the experienced guys, but fall short whenever they run into issues they do not have the experience to troubleshoot. It will be tough to get referrals from your coating house, as a lot of times they are required to sign a non-disclosure agreement. A good way to evaluate their experience level would be to ask how many years they have been in business and their typical weekly, monthly, and yearly volumes processed. A visit to their facility, if warranted by the volume of the project, should give a good indication of the seriousness of their abilities.
Silicone conformal coating is becoming an increasingly popular choice for conformal coating applications. Because of its high temperature capabilities, moisture protection, and ease of application/rework, people are strongly considering silicone coatings for their projects.
Solvents can be used safely. However, the exposure of the operator to the solvent fumes must be REGULARLY measured and RECORDED. This ensures a safe operating environment and if an OSHA problem does arise in the future, evidence exists to rule out the conformal coating process as the culprit.
In applications that have an exposure to solvents, acrylic conformal coating is not the best choice. Acrylic conformal coating can be removed with a weaker solvent such as isopropyl alcohol or xylene. Whenever it faces even stronger solvents, it will not offer the protection that is needed, especially if your product is a mission critical device. Other coatings, such as urethane or parylene conformal coating have a far better resistance to solvents than acrylics.
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Medical Conformal Coatings Used
While all conformal coating types can be used for different applications, for many medical devices, parylene is the way to go. Because parylene is biologically inert, FDA approval of parylene coated devices is well-documented. The coatings comply with USP Class VI plastics requirements and are MIL-I-46058C / IPC-CC-830B listed. Another benefit for medical devices such as stents and catheters is that parylene is entirely conformal, meaning that component configurations with sharp edges, points, flat surfaces, crevices or exposed internal surfaces are coated uniformly without voids or pinholes.
Tags: parylene conformal coating, parylene coating process, Diamond-MT, conformal coating, silicone conformal coating, conformal coatings, LED conformal coating, Automotive conformal coatings, Medical conformal coatings, conformal coating standards