Abstract: In a circuit board of the present invention, a lead frame includes an electrode for mounting an electronic component. The lead frame is encapsulated in a resin portion. The lead frame includes a step portion exposed from a surface of the resin portion so that the electrode is formed. Accordingly, not only lead type electronic components but also surface mount type electronic components can be mounted on the surface of the circuit board. Therefore, because the electronic components can be concentrated, the lead frame circuit board can be miniaturized.

Abstract: In a circuit board of the present invention, a lead frame includes an electrode for mounting an electronic component. The lead frame is encapsulated in a resin portion. The lead frame includes a step portion exposed from a surface of the resin portion so that the electrode is formed. Accordingly, not only lead type electronic components but also surface mount type electronic components can be mounted on the surface of the circuit board. Therefore, because the electronic components can be concentrated, the lead frame circuit board can be miniaturized.

Abstract: An intelligence power device (IPD), having a temperature-sensitive and heat-damage protecting function, is used as a semiconductor relay which controls load current supplied to an electric load. A target sensitive temperature T.sub.SD of IPD is determined according to an allowable load current value, using an equation T.sub.SD =I.sup.2 .times.R.sub.ON .times.R.sub.TEMP +T.sub.ROOM, where I represents an allowable load current value, R.sub.ON represents an on-resistance value of a power MOSFET, R.sub.TEMP represents a thermal resistance value of an entire radiation system of IPD, and T.sub.ROOM represents an ambient temperature of IPD. When the load current exceeds the allowable load current value, IPD stops the load current so that the load circuit can be prevented from being subjected to excessively large current.