PURPOSE: To produce the electronic parts improving the strength of leading terminal against external force by a method wherein a leadframe is used both as a leading terminal and a part of leadframe is provided with slots to cast exterior resin thereinto.

CONSTITUTION: A leadframe 3 coated with insulating resin is provided with several slots extending in parallel with leading terminals in the longitudinal direction while insulating resin is cast into these slots by means of exterior work firmly fixing lead terminals. The slots provided in the lead terminals increase the thermal resistance having little influence upon elements. Besides bonding wire and resin for buffer absorb any thermal distortion while the insulating resin cast into the leadframe slots generates stress against the bending tensile exerted for the lead terminals resisting external force espesially effective for the one exerted in the lateral direction of the lead terminals.