A circuit board, which is often referred to as a PCB (printed circuit board), is a support for electrical and electronic components. It is used for mechanically fastening and electrically connecting electrical and electronic circuit components. Separate components, such as power (semiconductor) components, may be arranged on circuit boards in addition to more or less complex analogue and digital integrated circuits. In power electronics, power semiconductor components are designed for controlling and switching high electrical currents and/or voltages.
A requirement for reliable operation of these power semiconductor components is that heat produced during operation is dissipated. The heat energy generated is usually conducted to a heat sink which is provided in the housing of the power semiconductor component and emits the energy to the environment via the outside of the housing. It is essential for the cooling that this heat sink is thermally coupled to the circuit board or that a heat sink is provided on the circuit board. If heat energy generated is not effectively dissipated, it may lead to heat accumulation on the circuit board and in the component.
As a result, the power semiconductor components used may rapidly degrade in an undesired manner, and this may lead to the functional impairment or the malfunction of the power semiconductor component.
When using such leadframes as heat sinks for dissipating the heat energy generated, power semiconductor components may be soldered directly to the leadframe by the external terminals thereof. Here, the leadframe carries out both the function of low-resistance current conduction and the heat distribution and dissipation for effectively cooling the power semiconductor component.
Such power semiconductor components often only have one single power output terminal, via which the power current for operating the load is conducted to the outside. This output terminal is electrically and mechanically connected to the contact surface arranged on the circuit board by means of a single soldered joint. Since this soldered joint has a relatively small cross section, a relatively high level of power loss is produced at this narrow point which is caused by the resistance produced there, which power loss ultimately heats both the output terminal and the soldered joint to a greater or lesser extent. The higher the output current generated by the power semiconductor component for switching or operating the load and/or the lower this effective cross section of the output terminals, the higher the resistance and the associated level of heating caused by the power loss.
For this reason, primarily in power semiconductor components that are designed for high output currents, a plurality of output terminals are used in order to increase the effective cross section for the output current and thus to reduce the resistance caused by the output terminal. As a result, however, mounting on a leadframe is more difficult.
One aspect of the mounting consists in placing the power semiconductor components that are provided with a plurality of output terminals on the contact terminals available for this purpose in a targeted manner. While this is still relatively simple for just one output terminal and one control terminal, it becomes increasingly difficult for a plurality of output and control terminals, in particular if the output terminals and the control terminal are arranged directly beside one another and the respective contact surfaces and the distance between the output and control terminal are relatively small.
A further aspect consists in that a larger amount of solder material is required on the contact surface for contacting the plurality of output terminals. As a result, there is the additional risk that solder material will overflow from the contact surface for the output terminals onto the contact surface for the control terminal, in particular if the two contact surfaces are arranged very close to one another. Owing to said material running together, an undesired short circuit is produced between the contact terminals, as a result of which the power semiconductor component will become inoperative.