Reliability of unencapsulated SMD plastic film capacitors

Small and low cost unencapsulated SMD plastic film capacitors were manufactured with different terminal metal compositions and dielectric materials. Capacitors made with a polyethylene naphthalate film dielectric were produced using a winding method. The terminals were metallized using the flame spraying process. The terminals of the test capacitors consisted of three different metal layers. The base metal layer, which was aluminum, was coated with brass or copper. The top layer was a sprayed lead‐free, tin‐based solder to ensure the solderability of the terminals. The reliability of the unencapsulated test capacitors was evaluated using standard temperature cycling, humidity storage, and high temperature environmental tests. Solderability and resistance to soldering heat were tested by mounting the test capacitors using the reflow soldering technique. The electrical properties including capacitance, insulation resistance, and dissipation factors at 1kHz and 100kHz were verified.