Resin-sealed semiconductor device, leadframe with die pads, and manufacturing method for leadframe with die pads

Abstract

A resin-sealed semiconductor device with built-in heat sink prevents internal bulging and cracking caused by exfoliation of a semiconductor element from the heat sink when the vapor pressure of moisture absorbed into a gap between the semiconductor element and the heat sink rises during mounting of the semiconductor device to a printed circuit board using lead-free solder. By providing a plurality of separated die pads ( 502 ) in a mounting area for a semiconductor element ( 301 ) and adhering the semiconductor element ( 301 ) to the heat sink ( 105 ) via the die pads ( 502 ), space is opened up between the semiconductor element ( 301 ) and the heat sink ( 105 ) for sealing resin ( 304 ) to run into.

1 . A resin-sealed semiconductor device having a semiconductor element mounted on a heat sink, comprising: 
 a plurality of outer leads for external electrical connection extending at right angles to sides of a rectangle;    a plurality of inner leads in series at one end with the outer leads;    the heat sink adhered to an underside of an opposite end of the inner leads;    a plurality of substantially square openings provided in the heat sink so as to lie partially outside a mounting area for the semiconductor element and with sides thereof positioned at an angle to a direction in which the outer leads extend;    the semiconductor element adhered by adhesive to an upper surface of the heat sink in an area sandwiched by the openings;    a plurality of metallic wires electrically connecting the inner leads with corresponding electrode pads of the semiconductor element; and    a sealing resin that seals the inner leads, the semiconductor element and the metallic wires, with the outer leads left exposed.    
     
     
         2 . The resin-sealed semiconductor device of  claim 1 , wherein 
 the sides of the openings are positioned at an approximately 45° angle, and    the semiconductor element is adhered to the heat sink via a plurality of die pads.    
     
     
         3 . The resin-sealed semiconductor device of  claim 1  further comprising a loop-shaped body encircled by the ends of the inner leads and surrounding the mounting area, the loop-shaped body being adhered to the upper surface of the heat sink via an underside thereof and having an inward protrusion positioned centrally on each side thereof.  
     
     
         4 . A leadframe for use in a resin-sealed semiconductor device having a semiconductor element mounted on a heat sink, comprising: 
 a plurality of outer leads for external electrical connection extending at right angles to sides of a rectangle;    a plurality of inner leads in series at one end with the outer leads and electrically connected to electrode pads of the semiconductor element via connecting members;    the heat sink adhered to an underside of an opposite end of the inner leads;    a plurality of substantially square die pads adhered to the heat sink in a mounting area for the semiconductor element so that sides thereof are positioned at an angle to a direction in which the outer leads extend; and    a plurality of openings provided in the heat sink so as to form a checkered pattern with the die pads.    
     
     
         5 . The leadframe of  claim 4 , wherein 
 the sides of the die pads are positioned at an approximately 45° angle,    the openings have rounded vertices, and    each opening positioned circumferentially lies partially outside the mounting area.    
     
     
         6 . A method of manufacturing a leadframe for use in a resin-sealed semiconductor device having a semiconductor element mounted on a heat sink, comprising the steps of: 
 etching or stamping a piece of sheet metal to manufacture a metallic member that includes outer leads for external electrical connection extending at right angles to sides of a rectangle, inner leads in series at one end with the outer leads, substantially square die pads positioned with sides thereof at an angle to a direction in which the outer leads extend, a coupling ring coupling together the die pads, a dambar coupling the inner leads to the outer leads in side directions of the rectangle, and hanging leads holding the die pads from vertices of the dambar;    adhering an upper surface of the heat sink to an underside of an opposite end of the inner leads and an underside of the die pads; and    providing a plurality of openings in the heat sink to form a checkered pattern with the die pads and at the same time sectioning the coupling ring and the hanging leads.