Analysis of Parameters Influencing Stresses in the Solder Joints of Leadless Chip Capacitors

The purpose of this study was to evaluate parameters such as solder joint standoff and fillet heights, termination cap length, chip eccentricity, chip rotation, etc. that influence stresses in the solder joints as well as the leadless chip capacitors. This analysis covers COG and X7R ceramic chip capacitors on multi-layer FR-4, and G-30 PWB or Alumina substrates. From the values of the stresses computed, it appears that (i) the stand-off height should be at least 100μm (.004 in.) (ii) the solder fillet height should be around half the chip thickness, (iii) the chip eccentricity on the mounting pad should be restricted to 8 percent of the chip length and (iv) chip rotation should be within 3.5 deg, while maintaining minimum solder stand-off height of 100μm (0.004 in.). The recommendations given here should be used only as preliminary design guidelines and not as a substitute for design and analysis or the requirements of manufacturing standards.