TECHNICAL FIELD

The present invention relates to a semiconductor device having a deterioration detection function.

BACKGROUND ART

A semiconductor element (power module) in which a power semiconductor element is packaged is used as a switching element in a wide range of fields. The semiconductor device may be used as a primarily component of a power supply system or motor drive system in general purpose devices (such as home appliances, electric vehicles, trains, or elevators) or industrial apparatuses (such as servomotors), for example.

Some semiconductor devices have a deterioration detection function. Japanese Patent Laying-Open No. 2010-93289 (PTL 1) discloses a power semiconductor module which detects deterioration of multiple metal wires (bonding wires) by measuring a potential difference between a surface electrode of a semiconductor element and an electrode metal plate which is connected to the surface electrode by the bonding wires.

CITATION LIST

Patent Literature

PTL 1: Japanese Patent Laying-Open No. 2010-93289

SUMMARY OF INVENTION

Technical Problem

Many of semiconductor devices, in which a power semiconductor element is packaged, interconnect a semiconductor element by ultrasonic bonded (bonded) bonding wires. When the semiconductor device is used for switching operation, a large current flows through the semiconductor device upon energized, and heat is thus generated due to a resistive component within the current path and also due to combination of electrons and holes at a P-N junction. The heat generated within the semiconductor device increases the temperature within the semiconductor device. The semiconductor device has a large heat value when energized, and thus is often connected to a heat sink to be air cooled or liquid cooled. When the semiconductor device is shut off, the temperature decreases. In general, a coefficient of thermal expansion is different between the semiconductor element and a component which includes metal interconnect and a solder, etc., and thermal stress can occur due to such changes in temperature. Changes in temperature, due to generation of heat and cooling, are significant particularly near the semiconductor element, and thus a stress is applied to and a crack is likely to occur at the joint between a bonding wire and the semiconductor element. As a crack is developed at the bonding wire, the bonding wire is easily come off or disconnected. The semiconductor device may fail due to such deterioration of the bonding wire. For this reason, there is a need to detect the deterioration of the bonding wire with high accuracy, in order to determine the life of the semiconductor device.

As the bonding wire connecting the surface electrode of the semiconductor element and an electrode metal plate is deteriorated, the resistance between the surface electrode of the semiconductor element and the electrode metal plate changes. The power semiconductor module disclosed in Japanese Patent Laying-Open No. 2010-93289 (PTL 1) detects deterioration of a bonding wire by detecting the changes in the resistance as changes in the potential difference between the surface electrode of the semiconductor element and the electrode metal plate.

If the surface electrode of the semiconductor element is formed from a single electrode pad, as the power semiconductor module disclosed in Japanese Patent Laying-Open No. 2010-93289 (PTL 1), the resistance (sheet resistance) of the electrode pad may be negligibly small, as compared to a combined resistance of multiple bonding wires. In such a case, changes in resolution between the surface electrode of the semiconductor element and the electrode metal plate is substantially equal to the changes in the combined resistance of multiple bonding wires.

Changes in the combined resistance of multiple bonding wires are primarily used to detect the deterioration of the semiconductor device, as Japanese Patent Laying-Open No. 2010-93289 (PTL 1), it may be difficult to detect the changes in the combined resistance of bonding wires if the changes are small.

The present invention is made to solve the problem as described above, and an object of the present invention is to increase the accuracy in detecting the deterioration of the semiconductor device.

Solution to Problem

A semiconductor device according to the present invention includes a first electrode and a second electrode, a control electrode, a controller, a first metal pattern and a second metal pattern, a connector, and a plurality of bonding wires. The controller applies a voltage to the control electrode to control current flow from the first electrode to the second electrode. The first metal pattern and the second metal pattern are connected to the controller. The connector connects the first metal pattern and the second electrode. The plurality of bonding wires connect the second metal pattern and the second electrode. The second electrode includes a plurality of electrode pads and a resistor. The plurality of electrode pads include a first electrode pad and a second electrode pad. The resistor is connected between the first electrode pad and the second electrode pad. The plurality of bonding wires include a first bonding wire and a second bonding wire. The first bonding wire connects the first electrode pad and the second metal pattern. The second bonding wire connects the second electrode pad and the second metal pattern. The controller is configured to detect deterioration of the semiconductor device when a potential difference between the first metal pattern and the second metal pattern is above a first threshold.

In the semiconductor device according to the present invention, as the bonding wire that is connecting the second electrode and the second metal pattern deteriorates, a value of resistance between the second electrode and the second metal pattern changes. Since the second electrode is connected to the first metal pattern, the change in the resistance value is detected by the controller, as a potential difference between the first metal pattern and the second metal pattern.

If any of the first bonding wire and the second bonding wire deteriorates, a portion of current which had flown through the deteriorated bonding wire will then pass through the resistor connected between the first electrode pad and the second electrode pad. As a result, the current distribution to the first electrode pad and the second electrode pad changes, which increases the sheet resistance of the second electrode. In the semiconductor device according to the present invention, as the bonding wire deteriorates, the sheet resistance of the second electrode also includes, in addition to the combined resistance of the plurality of bonding wires. As a result, changes in the potential difference between the first metal pattern and the second metal pattern upon deterioration of the bonding wire is greater than the case where the second electrode is formed from a single electrode pad.

Advantageous Effects of Invention

According to the present invention, the detection of changes in the potential difference due to the deterioration of a bonding wire can be facilitated. As a result, an increased accuracy in detecting the deterioration of the semiconductor device can be achieved.

