The Carbon style are the older type and I try to stay away from them, especially if they carry the rated current, they tend to change value with age/heat, the Metal film are one of the most common,especially in the small wattage range, they are stable and generally smaller than their carbon counterpart, with capacitors, anything 1µfd and up is generally either electrolytic or (much smaller) tantalum, these are generally used where pure DC or low frequency ripple is present. They cannot be used on high frequency or pure AC, one reason is they posses inductance and leakage on AC.
For large values on AC a high quality AC low loss (non-electrolytic) type capacitor should be used, for small values you can use MKT or MKP which has extremely low losses due to polypropylene dielectric.
Al
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.