Back To Basics: PCB Conformal Coating

Posted under Back to Basics, Educational, Product Design, Technology on November 24th, 2024 by

I was playing around with PCB conformal coating for a client project. Wanted to share my takeaways.
Conformal coating is a thin, non-conductive layer applied to the surface of a PCB. It conforms (hence the name) to the board’s contours, including components and traces, forming a protective barrier. This coating acts as the PCB’s protection armor against environmental damages like humidity, dust, or chemical exposure.

Why use it? It provides humidity protection. When your device needs to work in high-humidity areas, condensation can happen on the PCB surface to short the circuits and can even erode the tracks with continuous exposure. In industrial or automotive environments, exposure to chemicals like solvents or oils can degrade PCBs. Coatings provide a barrier against that. Some coatings are done all around the PCB not just as a thin layer to make it mate with an enclosure to be a temperature insulator and to provide vibrational rigidity to the PCBs. Also used as a high-voltage insulation barrier.

Conformal Coatings are of a few types:
Acrylic: Affordable, easy to apply, and repairable. Good for hobby projects. You can solder/rework them if needed. Usually transparent and comes with and without UV glow. UV glow is a cool feature that will allow you to see where the coating has been applied under UV light(Check pics).
Epoxy: Strong and durable, but rigid when hardened. They are often seen as black material covering bare dies or chips, commonly used to prevent reverse engineering of PCBs as they are difficult to remove without aggressive chemicals and significant effort. You will see them a lot in defense products.
Silicone: Great for extreme temperatures and flexible surfaces. Common in automotive or aerospace applications.
Common methods of applying it include spray coating, brush application, dipping, or selective dispensing by machines for large volumes. The application really depends on the type, MoQ volume, thickness and precision needed.

Feel free to try them out on your next projects. They can make or break a product in the right environmental conditions!

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Back To Basics: Thermal Pads vs Thermal Paste

Posted under Back to Basics, Educational, Hacks, Repair, Technology on November 17th, 2024 by

Recently, I was working on a client project where I had to decide between using thermal pads or thermal paste for a custom heat dissipation solution. It’s a decision many engineers face, and I thought it’d be helpful to break it down here.

Basics first. Transferring heat is critical to ensure your electronics last longer and perform better. It can be SoCs, LEDs, Power MOSFETs etc. Both thermal paste and thermal pads are materials used to fill microscopic air gaps between a heat-generating component and a heatsink. But when should you use one over the other?

Thermal paste/Thermal grease is a viscous material that provides great thermal conductivity. It’s often preferred in cases where the contact surfaces are perfectly aligned or where you require maximum heat transfer. Since they are in paste form they virtually have no “thickness” so the metal heatsink technically has max contact with the heat source for maximum heat transfer.

Thermal pads are pre-formed, solid sheets of thermal material that are easy to apply and is not messy to use at all. Here the overall heat transfer is less because this material has some thickness and it acts as an insulator between the heat source and the heatsink. So why would you want to use this if conductivity is lower? It’s for those cases where you can’t have flush contact between the heatsink and the source for different reasons like non-flat surface due to manufacturing tolerance or if you are using the same heatsink for multiple ICs of varying heights. The spongy nature of thermal pads handles this height variation. Another great thing is it doesn’t dry out over time. Make sure you choose thermal pads of the minimum thickness possible.

In summary, both materials have their place. If max heat transfer is needed and surfaces are flat go for thermal grease, else use thermal pads. Hope this helps.

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