Method of making plastic encapsulated semiconductor devices

A method of preparing plastic encapsulated semiconductor devices which comprises the steps of:

• preparing a connected metal plate in which a plurality of semiconductor element holding parts are connected in series in one direction with at least two connecting arms, disposed between each pair of semiconductor holding parts, said connecting arms each having an area smaller than that of said semiconductor element holding parts;
• forming all of said connecting arms inside the side surfaces of said semiconductor element holding parts in the connecting direction for substantially preventing the formation of dulls caused by punching a metal plate;
• providing semiconductor elements having a pair of main surfaces in parallel with each other and a pn junction in said semiconductor elements, the exposed pn junction being coated with one of a glass passivation and a nitride passivation;
• bonding the semiconductor elements on one main surface of said semiconductor element holding parts;
• providing a lead frame having a plurality of spaced parallel ribbon lead electrodes extending from a common connecting part;
• bonding the free ends of the ribbon lead electrodes on the other of the main surfaces of said semiconductor elements;
• plastic encapsulating said semiconductor elements, said semiconductor element holding parts and said ribbon lead electrodes except said connecting arms, the other main surface of said semiconductor element holding parts and the connecting part of said ribbon lead electrodes;
• separating said semiconductor devices by cutting said connecting arms of said connected metal plate and the connecting part of said ribbon lead electrodes;
• and
• supporting the connecting arms along the entire width of the connecting arms against the action of cutting of the connecting arms so as to prevent deformation of the semiconductor element holding parts.