Selection Guide: Consideration Factors for Choosing PCB Conformal Coating

Selection Guide: Consideration Factors for Choosing PCB Conformal Coating

Apr 15,2021

Printed Circuit Boards (PCBs) drive most electronic applications that we use today. Electronic or electromechanical systems from industries like automobile, modern electronics, military, and aerospace, etc highly rely on PCBs for functioning. Minute errors in the PCBs can potentially cause abrupt failure or serious damage to the industrial systems. This is why each element of PCB fabrication is usually performed with care. PCB conformal coating is one of the elements of PCBs that contribute to the performance, tolerance from external factors, and overall durability. There are multiple types of PCB conformal coating, and each type offers different characteristics and benefits to the application. This certainly makes the selection of conformal coating makes confusing. This post guides the readers through factors of consideration for the selection of appropriate PCB conformal coating.

An Overview of PCB Conformal Coating

The conformal coating is a thin layer of polymeric film applied on the surface of PCB along with the mounted components. This is a protective coating as it protects the component leads, current traces, solder joints, and other metallic elements against chemical exposure, erosion, dust, and foreign entities. Generally, the PCB conformal coating is only 25 microns thick but it holds a lot of importance in the PCB fabrication and its performance abilities. The conformal coating plays an important role in industrial applications exposed to high temperature, chemicals, pressure, moisture, etc.

Now let us discuss how to select appropriate conformal coating for the PCB fabrication.

Factors to Consider While Choosing the PCB Conformal Coating

An appropriate type of conformal coating for enhancing the performance of PCBs can be chosen in the following ways

  • Gain an Understanding of Types of Conformal Coating and Their Benefits:

    There are multiple types of conformal coating and each has a different set of benefits to offer. Let us discuss the types and their benefits.

    • Acrylic Resin (AR) Coating:

      This coating features a thin layer of acrylic material, and it is beneficial for applications where moderate flexibility, high dielectric strength, and resistance to abrasion and moisture are required.

    • Silicon Resin (SR) Coating:

      In this type of conformal coating, an ultra-thin layer of silicon is applied. It is a popular type of PCB conformal coating as it offers several benefits like moisture resistance, chemical resistance, salt-spray resistance, and high flexibility. This type of coating is suitable for the PCBs exposed to fluctuating high temperatures and high humidity.

    • Polyurethane Resin Coating:

      This type of coating features a layer of urethane or polyurethane resin. This type of coating is excellent for applications exposed to chemicals, solvents, and water.

    • Epoxy Coating:

      This type of conformal coating features a thin yet hard layer of epoxy resins (ER). This type of coating is not flexible or permeable however it offers excellent abrasion and chemical resistance.

    • Parylene Coating:

      This type of coating features a thin layer of Parylene applied using the vapor phase deposition technique. This type of coating is excellent for overall circuit board protection as it is highly resistant to moisture, solvents, chemicals, and high temperature.

    • Nano Coating:

      This type of coating features an ultra-thin layer of fluorocarbon-based solvent sprayed on the PCBs. This type of coating protects a PCB from short-time exposure to water.

  • Methods of Application:

    There are different methods of applying conformal coating on the PCBs. Commonly, brush, dip, spray, etc are the methods used in the industry. The chosen type of coating should be compatible with the method of application. This could impact the thickness of the coating.

  • Methods of Curing:

    Curing is the technique adopted post-application of conformal coating on PCBs. It helps in settling the layer of coating material and deposit to the best of possibility. Evaporative curing, moisture curing, heat curing, and ultraviolet (UV) curing are the common curing methods used. The compatibility of coating type and curing method must be considered.

  • Methods of Removal:

    Sometimes, the conformal coating needs to be removed and reapplied after a specific duration. Some types of coating like Parylene coating are difficult to remove with solvent removal. However, it can be removed with micro-blasting. Solvent removal, scraping, thermal burn-through, peeling are the methods of removal used. Therefore, a suitable method of removal must be considered while selecting a coating type.

No matter what type of conformal coating you choose, the quality of coating and PCB fabrication is essential. You should partner with a manufacturer that offers IPC/MIL/UL compliant PCB coating services. Creative Hi-Tech is the company that offers PCB coating and fabrication services compliant with the mentioned standards. They also offer RoHS-compliant services which ensure minimum harm to the environment without lowering the quality of their services.

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