With the globalization of the supply chain, you may manufacture PCBA boards in China, perform final assembly in India, and ultimately package them for sale in the United States. However, during the lengthy transportation, these fragile components may be susceptible to contamination, vibrations, corrosion, and moisture threats, leading to potential failures. To mitigate these risks, an effective protective measure is potting. In this article, TechSparks will delve into everything related to PCB potting to help you better implement this process.
What is PCB Potting
Potting, also known as “encapsulation”, is a technique used in electronic engineering to protect circuits or components from climatic interactions by filling a circuit board with some compound. These compounds include materials such as epoxy or silicone. Unlike conformal coatings, which apply a protective layer to the surface of the board, potting typically completely surrounds the board with a protective shell by injecting a fluid into a pot or enclosure, which allows for greater protection.
The potting process can be done manually or by machine, hand for prototyping and machine for bulk orders. Material selection is not arbitrary, but PCB potting compounds are selected based on specific applications (such as aerospace, automotive, or industrial) to balance cost and performance, providing project flexibility.
Why Potting PCB
For some cutting-edge applications, it is very important to have necessary protection measures because these boards are very expensive, especially in industrial or medical fields. Any component failure on the board may cause the entire PCBA to fail and cause serious economic losses.
Most sealants should be ionic, resistant to moisture, insensitive to thermal cycling, and have low shrinkage modulus. Adaptability and low psychology are essential for the sealant as they also act as an integral part of the strain support frame for the wire leads. PCB encapsulation reduces the weight of the wires and limits the risk of them breaking.
Potting forms a thick block on the PCB collection and may not be a reasonable decision for applications with weight or thickness constraints. It is difficult to evaluate or improve PCB collection configuration issues due to extra thickness and weight. A more complex two-stage blend and age intensity can be applied.
The benefits of potting PCB are:
- Eliminates the coefficient of thermal expansion, preventing issues caused by heat-induced delamination.
- Protects the PCB and components on the board from physical damage.
- Prevents the PCB from coming into contact with moisture and chemicals.
- Secures ICs from other security threats, such as replication or tampering.
- Colored encapsulation materials can deter competitors from disassembling the project.
Potting vs. Conformal Coating
Since the main topic of this article is related to PCB Potting, its twin brother, Conformal Coating, should also be mentioned. These two similar technologies are both used to protect the circuitry.
Further Reading: How to Choose Between Potting and Conformal Coating
| Feature | Potting | Conformal Coating |
|---|---|---|
| Concept | Potting or encapsulation involves wrapping the entire PCB, similar to amber. | Conformal coating, or three-proof paint, involves applying a protective film only on the surface. |
| Process | Pouring and molding involve pouring potting gel into a mold. | Brushing, spraying, or dipping. |
| Coverage | Provides protection for the entire PCBA board, including components and connectors. | According to the needs, it can be implemented as a whole or designated areas can be selected. |
| Flexibility | The process is simple, but once a component or circuit fails, it is difficult to repair. | If there is a fault, remove conformal coating on the PCB and re-implemented after repair. |
| Cost | Expensive and requires more manpower and material resources. | Relatively cheap and suitable for automated processes. |
| Applications | Protecting the PCB from extreme environmental threats by isolating it to mitigate physical and chemical damage. | Suitable for environments with humidity and dust, but the thin protective film results in lower physical and chemical resistance. |
PCB Potting Process Steps
Potting is after for assembly, and before implementation, it is essential to thoroughly clean the PCBA board to ensure its surface is free from dust, grease, or other impurities. Due to potentially irritating odors from some potting materials, it is recommended to carry out the entire potting process in a well-ventilated environment and to wear protective gear. Some equipment and materials needed include:
- Potting material: Choose epoxy resin, polyurethane, silicone rubber, or others based on specific application requirements.
- Protective gear: Gloves, goggles, masks, and similar items.
- Equipment: Includes potting machines, mixers, ovens, and a range of devices. If potting individual components, customized molds are also required.
Once all facilities are prepared, follow the PCB potting process:
- Potting is sensitive to moisture and in order to prevent circuit failure, the PCBA enclosure should be baked in a 60°C oven to remove any moisture.
- Use a marker pen to mark the required resin level on the box to ensure accurate dosage and identification.
- According to the manufacturer’s product manual or technical data, prepare the resin that meets the requirements and wear protective measures before mixing isocyanate and polyol.
- Continue to pour in the resin until the desired marking level is reached. It should be noted that pouring the resin vertically into the casing may cause bubbles, so place the pad under the casing at a 30-degree angle before pouring.
- The resin usually takes several hours to several days to cure at room temperature, depending on the material and amount used. After the resin is fully cured, the shell is placed in an 80°C oven for 24 hours.
- After the curing process is complete, remove the enclosure from the oven and use an analog Shore A hardness tester to check the final hardness of the resin at 20°C. It should be between Shore A 85 and 90.
Ending
PCB potting is a vital process for protecting sensitive circuit boards from environmental threats, ensuring their longevity and reliability in demanding applications. Whether you’re working in aerospace, automotive, industrial, or medical fields, the right potting material and process can safeguard your PCBs from moisture, vibrations, and physical damage. While potting offers superior protection compared to conformal coatings, it also comes with its own set of challenges, such as cost and the difficulty of repair once sealed.
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