Choose the safety position first, then capacitance and dielectric, then the package format. Package codes are STE format names, not EIA chip sizes. Land pattern and approval scope: see the datasheet.
- 01
Confirm the X1 or Y1 position
Define whether the capacitor sits line-to-line, line-to-earth or across an isolation barrier. A Y1 position requires the matching safety approval and insulation coordination in the end equipment.
- 02
Define the voltage envelope
Include nominal AC voltage, switching overshoot, surges and abnormal conditions. The 4 kVAC withstand is a test condition, not a continuous working-voltage rating.
- 03
Choose capacitance and dielectric
SL covers the lowest values with the highest stability; Y5P, Y5U and Y5V extend capacitance in that order. Capacitance change over temperature and tolerance: see the datasheet.
- 04
Verify footprint and creepage
Use the body and land dimensions of the selected package. Recheck creepage and clearance on the assembled PCB, including pollution degree, coating and spacing to the chassis.
- 05
Validate the assembly process
Handle the series as MSL 3, validate the reflow profile and observe the floor life after opening the bag. Confirm cleaning agents, coatings and potting compounds on the production assembly.