Patent Description:
Power control modules, e.g. Solid State Power Controller (SSPC) modules, can be used instead of conventional electro-mechanical relays and circuit breakers for power distribution in a number of different applications. Some SSPC modules are widely used in aircraft secondary distribution systems. A typical SSPC a power semiconductor device, e.g. a power transistor such as a metal-oxide-semiconductor field-effect transistor (MOSFET), and control circuitry are typically contained in a printed wiring board (PWB). A plurality of SSPC modules are often assembled onto a common PWB that includes multiple control circuit channels.

Traditionally, all the power transistors, e.g. MOSFETs, and control circuit channels are all on a single PWB. This is convenient for assembly but results in thermal dissipation being limited to whatever the surface area of that PWB allows for. This also means that the SSPC have been thermally limited to the energy that can be dissipated from the PWB. Previous heat sink methods have faced manufacturing inefficiencies due to manual operations required.

Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved methods of heat dissipation in SSPC modules, improved methods of manufacturing for SSPC modules with heat sinks, and improved module assemblies to facilitate such improved methods. <CIT> describes a structure for fixing an electronic device to a substrate.

A power control module according to the invention is described herein and defined in claim <NUM>.

In accordance with some embodiments, the access hole is a plate access hole defined in the heat sink plate to allow for soldering access during assembly. The plate access hole can be aligned with the second side of the power device. The access hole can be a PWB access hole defined in the PWB. The PWB access hole can be aligned with the first side of the power device. The PWB access hole and plate access hole can face towards one another across the power device. The PWB access hole can define a central axis. The PWB access hole and the plate access hole can be aligned such that the central axis of the PWB access hole extends through the plate access hole. The power device can be electrically connected to the PWB by at least one of a drain lead, a source lead or a gate lead. The power device can be an ISOTAB transistor. It is contemplated that the heat sink plate can be a copper plate heat sink.

A method of assembling a power control module according to the invention is also described herein and defined in claim <NUM>.

In accordance with some embodiments, soldering includes soldering at least one of a gate lead, a drain lead or a source lead. Pushing the power device toward the heat sink plate can include inserting a push pin through a PWB access hole and pushing the power device. Soldering the power device can include accessing the power device with a soldering tip through a plate access hole. Pushing and soldering can occur at the same time. Pushing the power device toward the heat sink plate can include inserting a push pin through the PWB access hole and pushing the power device from a first side. Soldering the power device can include accessing a second side of the power device with a soldering tip through the plate access hole. The second side of the power device can be opposite from the first side of the power device.

It is contemplated that the method can include aligning the power device with the PWB access hole. The method can include forming the at least one lead of the power device by bending the at least one lead. In accordance with some embodiments, the method includes aligning the PWB access hole with the plate access hole. The method can include moving the PWB and/or the heat sink plate with an automated X-Y table to align the PWB access hole and/or the plate access hole with at least one of a push pin or a soldering tip.

These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the embodiments taken in conjunction with the drawings.

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a power control module assembly constructed in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. Other embodiments of power control module assemblies in accordance with the disclosure, or aspects thereof, are provided in <FIG>, as will be described. The systems and methods described herein can be used to improve heat dissipation and ease of manufacturing of power control modules, e.g. Solid State Power Controller (SSPC) modules, such as those used in aircraft power distribution systems. The resulting power control module assembly provides about <NUM>% more printed wiring board (PWB) area to accommodate for more power devices, e.g. a single PWB can include <NUM>-<NUM> power devices, and can provide improved current limiting during current inrush events as compared with traditional power control module assemblies that have power devices directly mounted on the PWB. Moreover, embodiments of the present disclosure result in about <NUM>% more power dissipation per module, as compared with traditional modules that use the PWB for heat dissipation.

As shown in <FIG>, a power control module assembly <NUM> includes a plurality of power control modules <NUM>. Each power control module <NUM> includes a power device <NUM>, e.g. a semiconductor device, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), having a first side <NUM> and a second side <NUM>. Second side <NUM> is opposite from the first side <NUM> and includes a metallic tab <NUM> of the MOSFET inlaid therein. In <FIG>, metallic tab <NUM> is shown in the center MOSFET <NUM>, however, those skilled in the art will readily appreciate that the right and left side MOSFETs, and any others included in the assembly <NUM> would also have a similar configuration. Each transistor <NUM> is packaged as an ISOTAB MOSFET <NUM>, e.g. where the drain is electrically isolated from the metallic tab <NUM> of the MOSFET <NUM>. Those skilled in the art will readily appreciate that while transistor <NUM> is shown and described as an ISOTAB MOSFET, there are a variety of suitable semiconductor power devices that may be used for assembly <NUM>. Power control module assembly <NUM> includes a PWB <NUM> spaced apart from each first side <NUM> of each MOSFET <NUM>. PWB <NUM> is electrically connected to each MOSFET <NUM> by way of a source lead <NUM>, a drain lead <NUM> and a gate lead <NUM>. From the side view of <FIG>, only gate leads <NUM> of the MOSFETs <NUM> are visible. In the view of <FIG>, however, a respective MOSFET <NUM> is shown from its first side <NUM> and PWB <NUM> is not shown so that source lead <NUM>, and drain lead <NUM> of the respective MOSFET <NUM> are also visible. Leads <NUM>, <NUM> and <NUM> are bent upward and out of the page, away from the direction that an outer surface <NUM> of the tab <NUM> of MOSFET <NUM> faces. This is the opposite from standard leads, which are typically bent to longitudinally extend in the same direction that the tab surface faces. Those skilled in the art will readily appreciate that the side profile for source and drain leads <NUM> and <NUM>, respectively, would be similar to that of gate lead <NUM> and would be soldered to PWB <NUM> in a similar manner. PWB <NUM> includes a plurality of control circuit channels, where each channel corresponds to at least one of the MOSFETs <NUM> to form a respective power control module <NUM>.

With continued reference to <FIG>, assembly <NUM> includes a heat sink plate, e.g. a copper plate heat sink <NUM>, parallel to the main PWB <NUM> with all the power MOSFETs <NUM> mounted on it. Copper plate heat sink <NUM> is soldered to the second side <NUM> of each MOSFET <NUM> for heat dissipation from MOSFETs <NUM>. The metallic tab <NUM> is inlaid within the bottom surface of second side <NUM> and outer surface <NUM> of the metallic tab <NUM> faces copper plate heat sink <NUM>. Metallic tab <NUM> is connected to copper plate heat sink <NUM> by way of the solder to dissipate heat from the MOSFET <NUM> to the heat sink <NUM>. This is schematically indicated by solder material <NUM>. Copper plate heat sink <NUM> can be coupled to an aluminum chassis of the assembly by way of a wedge lock coupling. Copper plate heat sink <NUM> includes plate access holes <NUM> defined therethrough to allow for soldering access by a soldering tip <NUM> to each respective MOSFET <NUM> during assembly, which is described in more detail below. For clarity, a portion of copper plate heat sink <NUM> are broken away and shown in cross-section to show access holes <NUM> and soldering tip <NUM> extending through the middle access hole <NUM>. Each plate access hole <NUM> is aligned with a second side <NUM> of a respective MOSFET <NUM>.

As shown in <FIG>, PWB <NUM> includes PWB access holes <NUM> defined therethrough to allow a push pin <NUM> to extend through PWB <NUM> during assembly. For clarity, a portion of PWB <NUM> is broken away and shown in cross-section to show an access hole <NUM> and push pin <NUM> extending therethrough. Push pin <NUM>, as described in more detail below, is used to hold one of the MOSFETs <NUM> in place against copper plate heat sink <NUM> during soldering. Each PWB access hole <NUM> is aligned with first side of a respective MOSFET <NUM>. PWB access holes <NUM> and plate access holes <NUM> approximately face towards one another across their respective MOSFETs <NUM>. PWB access holes <NUM> each define a respective central axis A and PWB access holes <NUM> and plate access holes <NUM> are aligned such that each central axis A extends through the corresponding plate access hole <NUM>. While only a single soldering tip <NUM> and a single push pin <NUM> are shown, those skilled in the art will readily appreciated that the automated machinery can operate in a step and repeat operation in order to solder multiple MOSFETs <NUM>, as described below, or can include multiple soldering tips and push pins in order to solder more than one MOSFET <NUM> to copper plate <NUM> at a given time. An automated configuration with multiple soldering tips and push pins can also operate in a step and repeat operation, e.g. soldering two or more MOSFETs at a given time and then moving onto another set of MOSFETs.

With continued reference to <FIG>, a method of assembling a power control module assembly, e.g. assembly <NUM>, includes forming the source, drain and/or gate lead, e.g. source lead <NUM>, drain lead <NUM> and gate lead <NUM>, of a given transistor, e.g. MOSFET <NUM>, by bending at least one of the leads toward a PWB, e.g. PWB <NUM>. The method includes prepping the PWB by forming respective PWB access holes, e.g. PWB access holes <NUM>, for each transistor in the PWB. Those skilled in the art will readily appreciate that the PWB and its access holes are typically manufactured before any assembly is started. The method includes aligning each transistor with its respective PWB access hole. The method includes electrically connecting at least one of the leads for each of the transistors to the PWB by soldering. Solder material is indicated schematically by solder <NUM>. A portion of PWB <NUM> (on the right-hand side as oriented in <FIG>) is shown in cross-section to show the solder <NUM> connection between lead <NUM> and PWB. Assembly <NUM>, shown in <FIG>, is assembled by using an automated machine which includes a push pin, e.g. push pin <NUM>, and a soldering tip, e.g. soldering tip <NUM>.

As shown in <FIG>, the method can include aligning the PWB access hole with its corresponding plate access hole, and/or the method includes moving at least one of the PWB or the copper plate heat sink with the automated X-Y table to align at least one of the PWB access hole or the plate access hole with the push pin and/or the soldering tip. Automated X-Y table <NUM> is schematically shown in <FIG> and those skilled in the art will readily appreciate that X-Y table <NUM> may have a variety of configurations to permit movement relative to push pin <NUM> and/or soldering tip <NUM>.

Once aligned, the method includes pushing the transistor toward and against a copper plate heat sink, e.g. copper plate heat sink <NUM>, with the automated push pin from a first side of the transistor, e.g. first side <NUM>. The push pin is inserted through the PWB access hole. The method includes accessing a second side, e.g. second side <NUM>, of the transistor by inserting the soldering tip through a plate access hole, e.g. copper plate access hole <NUM>. While the push pin is pushing the transistor against the copper plate heat sink from the first side, the automated soldering tip solders the second side of the transistor to the copper plate heat sink through the plate access hole. Once the soldering is completed, the soldering tip and push pin are retracted out of their respective access holes. Then, an X-Y table, e.g. X-Y table <NUM>, moves the board to the next location, e.g. the access holes on the PWB and copper plate corresponding to the next unsoldered transistor. The pushing towards the PWB and the soldering to the copper plate is then repeated for each transistor. Once all of the transistors are soldered to the copper plate, or even in between soldering steps, assembly <NUM> can be cleaned.

This method of mounting the power MOSFETs on copper plate <NUM> can result in at least a <NUM>% increase in thermal dissipation by assembly <NUM> and allows more board area on the PWB for additional SSPC circuit channels. The large shared thermal resource (e.g. the copper plate heat sink) easily consumes thermal transients from lightning and inductive clamping and, due to the increase in thermal dissipation, even allows for short term current limiting during inrush and overload events.

Claim 1:
A power control module (<NUM>) comprising:
a transistor (<NUM>) having a first side and a second side opposite from the first;
a heat sink plate (<NUM>);
a printed wiring board "PWB" (<NUM>) spaced apart from the first side of the transistor (<NUM>), wherein the PWB (<NUM>) is electrically connected to the transistor (<NUM>) and includes an access hole arranged and configured to allow for pushing the transistor towards the sink plate; and the power control module characterized in that the heat sink plate (<NUM>) is soldered to a second side of the transistor (<NUM>) for heat dissipation from the transistor (<NUM>), and in that the heat sink plate (<NUM>) includes a respective access hole (<NUM>, <NUM>) arranged and configured to allow for a soldering tip to access through the heat sink plate (<NUM>) and solder the transistor (<NUM>) during assembly.