Patent Description:
Document <CIT> discloses a spacer system for a semiconductor switching device which is formed as a spacer ring and a plurality of insulating elements. Document <CIT> discloses a switching device comprising a semiconductor element and a housing comprising a spring system with a ring-shaped washer laterally surrounding the semiconductor element for clamping the semiconductor element between two pole pieces.

Embodiments of the disclosure relate to an improved semiconductor switching device.

According to a first aspect of the disclosure a semiconductor switching device comprises a gate ring and a gate connector element for contacting the gate ring and comprises a pressure system for pressing the gate connector element onto the gate ring. The pressure system comprises an insulating ring and a plurality of spring beams arranged circumferentially on the insulating ring, wherein the insulating ring comprises a plurality of supports for supporting ends of the spring beams.

As examples, the semiconductor switching device may be a Gate Commutated Thyristor (GCT) or a Gate Turn-off Thyristor (GTO). The semiconductor switching device may be an Integrated Gate Commutated Thyristor (IGCT).

Semiconductor switching devices are often transported to a customer as a single piece and a plurality of devices may be stacked by the customer. In the stack, each of the devices is clamped. The pressure system presses the gate connector element onto the gate ring in the clamped state.

The gate connector element may comprise a plurality of fingers. Each of the fingers may rest on one of the spring beams. The fingers may rest on a central section of the spring beam. The fingers may be partly bend around the spring beams.

For preventing a movement of the spring beams in a circumferential direction, a wall may be present between adjacent ones of the supports. Thereby, the spring beams can be kept in alignment with fingers of the gate connector element.

The spring beams may comprise a thickening in their central sections. Accordingly, the spring beams may be thicker in their central sections than at their ends. The thickening may protrude axially beyond the supports. Thereby, a clearance between the gate ring and the supports can be enlarged. In addition to that, a clearance between the cathode pole piece and the semiconductor substrate can be ensured during a non-clamped state of the device.

The insulating ring may comprise a plurality of pins at a second side of the insulating ring opposite to a first side where the spring beams are arranged, wherein the plurality of pins are configured to provide a rotational locking of the insulating ring and/or further parts of the semiconductor switching device. As an example, a rotational locking of the gate connector element may be achieved.

The switching device may comprise a spacer ring for insulating the gate connector element from a cathode pole piece. The pressure system may provide a rotational locking of the spacer ring. The spacer ring may comprise a plurality of support elements for supporting the gate connector element and a plurality of slots between the support elements, wherein the pins engage in the slots. Accordingly, a rotational locking can be achieved by simply inserting the pins in the slots.

Each of the support elements may comprise a first portion and a second portion. The gate connector element may rest on the first portion and be prevented from rotating in one rotational direction by the second portion. The first and second portion may be provided as steps.

The pressure system is configured to be provided as a single piece for assembly of the semiconductor switching device. Accordingly, the spring beams are securely fixed to the insulating ring by the supports of the pressure system. This enables a fast and simply assembly and disassembly of the device.

According to a further aspect of the disclosure, a method for assembling a semiconductor switching device comprises the steps of providing a housing assembly of the semiconductor switching device and providing a pressure system for pressing a gate connector element onto a gate ring of the switching device. The housing assembly comprises a housing, a gate connector element and a cathode pole piece. The pressure system comprises an insulating ring and a plurality of spring beams arranged circumferentially on the insulating ring, wherein the insulating ring comprises a plurality of supports for supporting ends of the spring beams. In the method, the pressure system is assembled with the housing assembly, wherein the pressure system is provided as a single piece. The semiconductor switching device assembled in this method may have any structural and functional characteristics of the device described in the foregoing.

By providing the pressure system in the form of a single piece the assembly can be simplified. Thereby costs can be reduced and a correct assembly can be easily ensured when compared to a pressure system where single parts are provided and the parts are separately assembled with parts of the device.

Before assembling the pressure system with the housing assembly, a spacer ring for insulating the gate connector element from the cathode pole piece may be provided. The spacer ring comprises a plurality of support elements, wherein the spacer ring is placed around the cathode pole piece and rotated until the gate connector element is positioned on the support elements of the spacer ring.

In particular, fingers of the gate connector element may be positioned on first support portions of the support element and a further rotation of the spacer ring is blocked by second portions of the support element.

When assembling the pressure system, pins of the pressure system may be inserted in slots of the spacer ring. Thereby, a simple and effective self-locking mechanism of the pressure system and the spacer ring may be achieved.

After assembly of the pressure system, fingers of the gate connector element may be bend to be positioned on the spring beams.

The present disclosure comprises several aspects and embodiments. Every feature described with respect to one of the aspects and embodiments is also disclosed herein with respect to the other aspects and embodiments, even if the respective feature is not explicitly mentioned in this context.

Further features, refinements and expediencies become apparent from the following description of the exemplary embodiments in connection with the figures. In the figures, elements of the same structure and/or functionality may be referenced by the same reference signs. It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

All embodiments fall within the scope of the claimed invention.

<FIG> shows a detail of a semiconductor switching device <NUM>. The switching device <NUM> may be a GCT (Gate-Commutated Thyristor), in particular an IGCT (Integrated Gate-Commutated Thyristor). The IGCT may be a large-area IGCT, where the gate structure on the GCT wafer is placed on wafer periphery.

The switching device <NUM> comprises a semiconductor substrate <NUM>, a cathode pole piece <NUM>, an anode pole piece <NUM> and gate ring <NUM>. The cathode pole piece <NUM> comprises a cathode strain buffer plate <NUM> and the anode pole piece <NUM> comprises an anode strain buffer plate <NUM>. The strain buffer plates <NUM>, <NUM> are made of an electrically conductive material having a coefficient of thermal expansion which is between that of the semiconductor substrate <NUM> and the respective pole piece <NUM>, <NUM>. The gate ring <NUM> is electrically connected by a gate connector element <NUM>.

A pressure system <NUM> serves to apply a required pressure force on the gate connector element <NUM>. The gate connector element <NUM> transfers the force on the gate ring <NUM> to ensure proper switching capability of the semiconductor substrate <NUM>.

In addition to that, the pressure system <NUM> serves to lock elements in place, e.g. during transport or during vibrations tests. The pressure system <NUM> locks a spacer ring <NUM> and prevents it from turning around. The spacer ring <NUM> electrically insulates the gate connector element <NUM> from the cathode pole piece <NUM>.

The switching device <NUM> comprises a housing <NUM> comprising creepage sections at the outside. The housing <NUM> is connected to the anode pole piece <NUM> by an anode flange <NUM>.

During transport and vibration tests, the switching device <NUM> is usually provided as a single piece. In operation, a stack of clamped switching devices <NUM> can be formed for electrically interconnecting the switching devices <NUM>. In the stack, the anode pole piece <NUM> is pressed towards the semiconductor substrate <NUM>.

<FIG> shows the pressure system <NUM> which is part of the switching device <NUM> of <FIG> and is assembled with a housing assembly when forming the switching device <NUM> (see <FIG>). <FIG> shows an enlarged detail of <FIG> shows an enlarged detail of <FIG>.

The pressure system <NUM> comprises an insulating ring <NUM> of an insulating material. The insulating ring <NUM> may comprise a plastic material, for example.

The pressure system <NUM> further comprises a plurality of spring beams <NUM>. The pressure system <NUM> consists of the insulating ring <NUM> and the plurality of spring beams <NUM>. The spring beams <NUM> are configured to deflect and return to their original shape afterwards. The spring beams <NUM> may comprise a spring material such as spring steel. The pressure system <NUM> can be denoted as "segmented" pressure system <NUM> due to the plurality of spring beans <NUM> instead of a single spring extending circumferentially along the insulating ring <NUM>.

The spring beams <NUM> are mounted on a first side <NUM> of the insulating ring <NUM>. The first side <NUM> can be denoted as top side. The spring beams <NUM> are arranged circumferentially along the first side <NUM> and form a closed ring. Each of the spring beams <NUM> is fixed at each of its ends <NUM>, <NUM> in one of a plurality of supports <NUM>, <NUM>. The supports <NUM>, <NUM> may be an integral part of the insulating ring <NUM>. The spring beams <NUM> may be held into the supports <NUM>, <NUM>. The supports <NUM>, <NUM> have a flexible self-locking design such that the spring beams <NUM> are securely fixed to the ring <NUM>. As an example, the spring beams <NUM> can be clicked into the supports <NUM>, <NUM>.

A wall <NUM> between adjacent supports <NUM>, <NUM> provides positioning of the spring beams <NUM> in the correct circumferential position. This ensures that the spring beams <NUM> are centered with respect to a gate connector element <NUM> to ensure correct pressure distribution.

Due to the segmented design of the insulating ring <NUM>, a tuning of the pressure force on the gate ring <NUM> can be easily adjusted by changing the length, diameter or the total number of the spring beams <NUM>. Furthermore, the segmented design enables reducing the total height of the pressure system <NUM>, which allows to reduce the total height of the housing <NUM> of the switching device <NUM>. This may allow to reduce the total height particularly in case of designs for lower voltage classes.

The pressure system <NUM> comprises pins <NUM> at a second side <NUM> of the insulating ring <NUM>. The second side <NUM> is a side opposite to the first side <NUM> and may be a bottom side of the insulating ring <NUM>. The pins <NUM> serve to hold further part of the switching device <NUM> in place as will be explained in detail in connection with <FIG>. The pins <NUM> may be an integral part of the insulating ring <NUM>.

<FIG> shows the switching device <NUM> of <FIG> in a clamped state. As distinguished from the non-clamped state as shown in <FIG>, the anode pole piece <NUM> is pressed towards the semiconductor substrate <NUM>. The gap between the cathode strain buffer plate <NUM> and the semiconductor substrate <NUM> is removed.

In addition to that, the spring beams <NUM> are deflected downwards in their central sections and, thus strained.

Accordingly, the spring beams <NUM> exert a spring force onto the gate connector element <NUM> towards the gate ring <NUM>. In the non-clamped state as shown in <FIG>, the sprig beams <NUM> are relaxed. It is also possible that the spring beans <NUM> are already slightly deflected and, thus, strained in the non-clamped state. It is also possible that the pressure system slightly presses the gate connector element onto the gate ring already in the non-clamped state of the device.

<FIG> shows a perspective view of the spacer ring <NUM> and <FIG> shows a detail thereof. The spacer ring <NUM> comprises a ring-shaped wall <NUM> and a plurality of support elements <NUM> arranged circumferentially at a bottom side of the wall <NUM>.

Each of the support elements <NUM> comprises a first portion <NUM> and a second portion <NUM>, wherein the first portion <NUM> has a smaller height than the second portion <NUM>. The first portion <NUM> is provided for supporting the gate connector element <NUM>, in particular fingers <NUM> of the gate connector element <NUM> (see also <FIG>).

The second portion <NUM> is configured to from a stop for the fingers <NUM> when assembling the switching device <NUM> (see also <FIG>). The second portion <NUM> may additionally form a support for the pressure system <NUM>.

The slots <NUM> are configured to receive the pins <NUM> of the pressure system <NUM> (see <FIG>).

<FIG> shows steps in a method for assembling a switching device <NUM>. The switching device <NUM> and the components thereof may be as described in connection with the foregoing figures.

In <FIG>, a housing assembly <NUM> of the switching device <NUM> including the housing <NUM>, the cathode pole piece <NUM> and the gate connector element <NUM> is provided. The gate connector element <NUM> is fixed to the housing <NUM>, as an example soldered between two parts of the housing <NUM>. The housing assembly <NUM> comprises also a further gate connector element <NUM> (see <FIG>) fixed to the housing <NUM> and fixed to the cathode pole piece <NUM>.

A spacer ring <NUM> is inserted into the housing assembly <NUM> from the top. The slots <NUM> are initially aligned with the fingers <NUM> of the gate connector element <NUM>. Once the spacer ring <NUM> sits on the cathode pole piece <NUM>, the spacer ring <NUM> is rotated until the fingers <NUM> sit on the first portions <NUM> of the support element <NUM>. The rotation is stopped by abutment of the fingers <NUM> on the left side of the second portion <NUM>. The rotation is clockwise when seen from a top to a bottom of the housing <NUM>. <FIG> shows the fingers <NUM> in their end position after rotation.

<FIG> shows a subsequent step, in which the pressure system <NUM> is inserted into the housing <NUM> from a top side such that the pins <NUM> fit into the slots <NUM>. The pressure system <NUM> is inserted as a single pre-assembled piece. The pressure system <NUM> may then sit on the second portion <NUM> of the support element <NUM> and/or directly on the cathode pole piece <NUM>.

In this position, the pressure system <NUM> prevents the fingers <NUM> from moving back anti-clockwise. The spacer ring <NUM>, the pressure system <NUM> and the fingers <NUM> are locked together and prevented from rotation. Accordingly, a self-locking design of pressure system <NUM>, gate connector element <NUM> and spacer ring <NUM> is provided.

Moreover, due to the pins <NUM>, which fit properly into the slots <NUM>, the spring beams <NUM> are also properly aligned with the fingers <NUM>. In a subsequent step, the fingers <NUM> are bend over the spring beams <NUM>. The fingers <NUM> are aligned with a central section of the beams <NUM> so that the pressure onto the gate ring <NUM> can be distributed homogeneously.

After that, the gate ring <NUM>, the semiconductor substrate <NUM> and the anode pole piece <NUM> is inserted in the housing <NUM> from the top side and the anode flange <NUM> is fixed to the anode pole piece <NUM>.

The rotational locking by inserting the pins <NUM> in the slots <NUM> is simple and does not require special tools. Accordingly, the assembly is simpler and faster than in the prior art where fingers <NUM> are bend into a specific position of a spacer ring for preventing the spacer ring from rotation.

<FIG> show a further embodiment of a semiconductor switching device <NUM> with a pressure system <NUM>. The only distinguishing feature from the embodiments described in the foregoing is that the spring beams <NUM> have a thickening <NUM> in a central section. The thickening <NUM> may be an integral part with the rest of the spring beam <NUM>. It is also possible that the thickening <NUM> is an additional element enclosing the rest of the spring beam <NUM>.

Due to the thickening <NUM> the spring beam <NUM> protrudes in an axial direction beyond the supports <NUM>, <NUM>.

Thereby, a clearance <NUM> between the cathode pole piece <NUM> and the semiconductor substrate <NUM> can be enlarged. Furthermore, it is ensured that a proper distance between the supports <NUM>, <NUM> and the gate ring <NUM> is maintained. The thickening <NUM> also enables a larger bending of the spring beams <NUM> without that the gate ring <NUM> sits on the supports <NUM>, <NUM>.

Overall, the segmented pressure system <NUM> makes the assembly of the switching device <NUM> easier, faster and poka-yoke, because the pressure system <NUM> can be inserted in the housing <NUM> as a pre-assembled part. This is an advantage over the prior art where several disc springs and spring washers have to be individually inserted into the housing <NUM> during assembly of a GCT element, and each of the elements has to be correctly oriented.

In addition to that, the segmented pressure system <NUM> can be made more compact in terms of total height. Thereby, also the housing <NUM> can have a smaller height and cost saving, as long as it is sufficient for the desired voltage class.

A fine tuning of the spring characteristics of the pressure system <NUM> can be achieved by adjusting the number, diameters or lengths of the spring beams <NUM> to achieve the required pressure force applied on the gate ring <NUM>.

Claim 1:
A semiconductor switching device (<NUM>) comprising a gate ring (<NUM>) and a gate connector element (<NUM>) for contacting the gate ring (<NUM>) and comprising a pressure system (<NUM>) for pressing the gate connector element (<NUM>) onto the gate ring (<NUM>), characterized in that the pressure system (<NUM>) comprises an insulating ring (<NUM>) and a plurality of spring beams (<NUM>) arranged circumferentially on the insulating ring (<NUM>), wherein the insulating ring (<NUM>) comprises a plurality of supports (<NUM>, <NUM>) for supporting ends (<NUM>, <NUM>) of the spring beams (<NUM>).