I am hoping someone can point me toward some clarity regarding the durability of thin film SMD resistors. Google pointed me toward a number of pages that indicate they are sensitive to humidity and self-etching (e.g., EE Times) as well as to manufacturer pages who claim to have tackled the problem (e.g., Vishay).
In practice, should I be concerned about using all/some thin film SMDs in consumer electronics applications (analog high-performance audio in particular)? Including situations where the user leaves the unit unpowered for long periods and/or the resistor dissipates very little power? Will conformal coating improve/aggravate the problem?
Best Answer
Where I worked at we coated ALL circuit boards with a conformal coating, usually a polyurethane type of spray. Then all of those issues about humidty and self-etching and trace corrosion and capacitor film degrading go away, not to mention creapage currents due to humidity and dust build-up on the board, especially if the board has high voltage greater than 48VAC on it.
Thin film resistors and film capacitors have this corrosion issue, which is why the coating is mandatory for many manufacturing plants. The last thing they want is latent failures or worse yet, a burned board that left soot all over the place.