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What Is Conformal Coating and Why Is It Used During PCB SMD Assembly?

Conformal Coating and Why Is It Used During PCB SMD Assembly

Conformal coating is applied to the exposed surfaces of a pcb smd assembly to protect them from environmental exposure and improve durability. There are many factors to consider when selecting the best conformal coating to meet your specific requirements including: – The type of electronics being produced.

Some types of circuit boards (especially those with delicate components) require a thicker conformal coating than others to prevent damage during handling or during shipping and storage. – The operating temperature range of the circuit board – Some conformal coatings are not suitable for use at high temperatures and may need to be modified during the design phase in order to lower the maximum operating temperature.

How the conformal coating will be applied – The application method is also a critical factor to consider. There are a number of different methods available including dipping, spraying and brushing and each has advantages and disadvantages. – Production throughput requirements – The amount of prep work required for the board and the speed at which it needs to be coated will influence which technique is most appropriate.

Component type and placement – Some circuit boards have very close-together connectors that will need to be carefully protected from the conformal coating during manufacture. This will require careful masking to avoid the coating being transferred to areas it is not needed. – Rework and repair – The ability for the conformal coating to be easily removed is important if it is found to be defective or in need of rework. Electrolube offers a selection of products to facilitate the removal of conformal coating.

What Is Conformal Coating and Why Is It Used During PCB SMD Assembly?

There are a variety of conformal coating materials available on the market today, each with different properties and benefits. The most common are silicones and acrylics. Silicones are very easy to apply and are tolerant of high temperatures and moisture. Acrylics are good for a wide range of temperature and humidity conditions, but are not as flexible as silicones.

Whichever type of conformal coating is selected, it is essential that the PCB is thoroughly cleaned before the process begins to ensure that the coating adheres to the surface of the board and does not cause any further issues. This is a step that is often overlooked and can lead to problems such as corrosion and poor electrical performance.

The cleanliness of the PCB will also impact on the reliability of the finished product. Almost all conformal coating material suppliers recommend that the PCB be pre-washed and dried before coating to reduce the risk of any contamination transferring from the board to the conformal coating. In the event that there are cost or time constraints that would not allow the PCB to be cleaned before conformal coating, qualification procedures should be undertaken (such as ion chromatography) to ensure that the coating will still provide the required level of protection.

Typically, the inspection will be carried out manually by an inspector who will examine each component under a high-intensity UV light to check for compliance with standards. However, automated optical inspection systems (AOI) are increasingly being used in the industry to automate the process.

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