I recently dealt with an experience where I had a PCB that needed to be waterproofed using an epoxy resin coating. The PCB board was completely covered with this epoxy coating. The design and circuit worked just fine before the epoxy coating was applied, but after drying the circuit had all kinds of issues and misc. problems. After the coating was removed, it was found that the some of the packages had suffered damage being pulled apart and some of the ICs were pulled off the board during drying. I then found that when a PCB board is covered with any type of material, certain things need to be taken into consideration.
-What type of material that is being used?
-Is the drying time and temperature not going to damage any PCB or ICs that you are covering?
-Are the CTEs (Coefficient of Thermal Expansion) for all of the material that you are using (PCB, ICs, Passives) the same or close to the same? This one is VERY important because if you have one object that has a different expansion from another, then they will expand differently and pull apart from one another. Hence, the pulling packages off the board.
-Is the process that you are doing to cover the board going to cause any stress on the board or components after the process is complete and the device is in the field?
Please take these things into consideration if you are thinking about covering the board with any types of overmoldings. Thank you.
