Moisture and electronics do not get along.

If your board will be used in greenhouses, boats, fish farms, coastal areas, or anywhere that experiences heavy condensation, moisture protection should be considered.

In many cases, it is not necessary to coat the entire PCB. Applying a conformal coating to sensitive areas, especially fine-pitch components such as QFP packages, is often enough.

Just be careful not to get coating material inside connectors or sockets, as this can lead to poor electrical contact.

Don't forget about heat.

Electronics generally prefer cool environments.

A board that works perfectly on a workbench may behave very differently inside a sealed enclosure on a hot summer day. Temperatures inside equipment can rise surprisingly high if there is no airflow.

If significant heat is expected, consider adding heatsinks, ventilation openings, or cooling fans.

I've even seen systems placed inside completely sealed enclosures with no way for heat to escape. Those systems usually work well—until they don't.

A small cooling fan is often a cheap and effective way to improve long-term reliability.

Keep control circuits away from noise sources.

Transformers, motors, contactors, and other large inductive devices generate electrical noise whenever they operate.

Placing a microcontroller or control circuit right next to these components is asking for trouble.

Whenever possible, keep control electronics physically separated from high-power equipment. If space allows, placing them on separate boards is even better.

If they must be located close together, consider using a metal shield between them to help reduce electrical interference.

Many noise problems can be avoided simply by paying attention to layout and component placement before the design is finalized.

←Noise Is My Friend