Electronic – When to use film capacitor

MLCC capacitors, especially of large values, are notoriously voltage dependent so NO, I would never use one of them for an integrator if you care about the precision of your time constants. Typical dynamic capacitance of these capacitors can drop to as little as 30% of their nominal value by the time you have reached half of their rated voltage.

Also, be very careful not to crack it by bending your PCB even slightly, as when inserting connectors. Don't place them anywhere near a board edge that will be removed. If removing board edges, please don't use priers (!).

I use MLCC capacitors for decoupling supplies and to get scared. Their failure mode is typically a short-circuit. Presumably, in your application, a short-circuit means run-away heating in your control loop.

Film capacitors have a very stable capacitance over DC bias. Look at this:

But it comes to happen that film capacitors are not the only ones immune to DC bias:

So, the actual question is why do ceramic capacitor have such a bad behaviour with DC bias? And the answer lies in the dielectric.

In order to achieve high capacitance values in small capacitor sizes, a high-K dielectric materials like Barium Titanate have to be used. Unfortunately Barium Titanate also has ferroelectric properties that reduce its capacitance value under DC bias:

When spontaneous polarization is reversed under no voltage stress (no DC bias), MLCCs achieve a high capacitance. However, if an external bias is applied to the spontaneous polarization process, the free reversal of spontaneous polarization is much more difficult. As a result, the capacitance gained is lower compared to the capacitance before the application of the bias. This is why capacitance decreases when DC bias is applied-hence the term DC bias characteristic.

Sources:

Quote: Understanding DC Bias Characteristics in High-Capacitance MLCCs.

Images: this comparison document from NIC Components.