Coaxial switch module

Claim 2

A semiconductor switching device module of reduced inductance comprising: a housing having a baseplate and defining a chamber; a first terminal member having a cylindrical body portion and at least one flange, and also having a first inductance; a second terminal member having a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that has at least one flange, and also has a second inductance that is substantially similar to said first inductance; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber on said baseplate in a generally symmetrical array that encircles said terminals, including their flanges; a radially outwardly spacing of each of said substrates from a respective flange portion of each of said terminals, said spacing not being further than about a maximum dimension of one of said chips; a radially inward input electrical connection between each of said chips and a respective flange portion of one of said terminals; a radially inward output electrical connection between each of said chips and a respective flange portion of the other of said terminals; and a spacing between said first and second terminal members, including their flanges, effective to allow said first and second inductances to negate each other.

Claim 3

The module of claim 1 in which each flange is a radially outwardly circumferential flange.

Claim 4

The module of claim 2 wherein the flange on at least one of said terminal members has a plurality of segments.

Claim 5

The module of claim 2 wherein the cylindrical body portion of the second terminal member surrounds the cylindrical body portion of the first terminal member and said body portion has at least one integral outward radial enlargement adapted for attachment of a bus.

Claim 6

The module of claim 4 wherein said cylindrical body portion of said second terminal member has a circumference, the body portion has at least two outward radial enlargements, and said enlargements are substantially symmetrically disposed around the circumference of said body portion of said second terminal member.

Claim 7

The module of claim 1 wherein the housing includes, the coaxial terminal members comprise a subassembly affixed to the housing baseplate, at least one of the coaxial terminals includes a threaded bore for attachment of a electrical bus conductor, the baseplate contains a recess, and a surface of said subassembly contacting said baseplate contains a complementary boss nested in said recess, effective to provide a mechanical lock against rotation when said bus conductor is bolted to said subassembly.

Claim 8

A high power semiconductor device module such as described in claim 1 in which the plurality of insulated gate switching transistor chips in said chamber are insulated gate bipolar transistors and said transistors collectively comprise a single switch.

Claim 9

A high power semiconductor device module capable of operating at high frequency and low parasitic losses comprising: a housing defining a chamber and including a baseplate and a cover; a first cylindrical terminal conductor of a given composition and having an axis perpendicular to said baseplate and a first outwardly extending circumferential flange, said first flange disposed within said chamber parallel to said baseplate for connection to a plurality of high power insulated gate switching transistors in said chamber, and an end of said first terminal conductor disposed outside said chamber for connection to a first external bus, said first terminal conductor having a given electrical resistance and inductance with respect to electrical current flow therethrough; a second cylindrical terminal conductor including a second flange disposed within said chamber for connection to said plurality of high power insulated gate switching transistors and further including an end of said second terminal conductor disposed outside said chamber for connection to a second external bus, effective to permit coaxial nesting of said first and second cylindrical terminal conductors together in spaced relationship in substantial overlapping disposition of cylindrical body portions and also of flange portions; said insulated gate switching transistors having substantially equal electrical performance characteristics and symmetrically, radially and circumferentially disposed within said chamber in proximity to said first and second flanges for reducing electrical inductance and resistance therebetween; an input electrical connection between each of said insulated gate switching transistors and said first flange to provide symmetry in input connection resistance and inductance; an output electrical connection between each of said insulated gate switching transistors and said second flange to provide symmetry in output connection resistance and inductance; at least a portion of said input and output electrical connections for each insulated gate switching transistor in substantially parallel disposition to each other at least in one plane, and in proximity to reduce net electrical inductance of said input and output electrical connections; a gate conductor means having a first portion disposed within said chamber and adapted to supply substantially equal gate voltage to each of said insulated gate switching transistors, and further having a terminal portion disposed outside said chamber for connection to a source of gate control voltage, said first portion including a circuit pattern in said housing surrounding the symmetrical disposition of said insulated gate switching transistors, said circuit pattern including a gate conductor pattern for said insulated gate switching transistors; and gate electrical connections between gate electrodes on each of said insulated gate switching transistors and said gate conductor means, whereby said transistors each operate at a predetermined current level.

Claim 10

A high power semiconductor device module capable of operating at high frequency and low parasitic losses comprising: a housing defining a chamber and including a baseplate and a cover; a first cylindrical terminal conductor of a given composition and having an axis perpendicular to said baseplate and a first outwardly extending circumferential flange, said first flange disposed within said chamber parallel to said baseplate for connection to a plurality of high power insulated gate switching transistors in said chamber, and an end of said first terminal conductor disposed outside said chamber for connection to a first external bus, said first terminal conductor having a given electrical resistance and inductance with respect to electrical current flow therethrough; a second cylindrical terminal conductor including a second flange disposed within said chamber for connection to said plurality of high power insulated gate switching transistors and further including an end of said second terminal conductor disposed outside said chamber for connection to a second external bus, effective to permit coaxial nesting of said first and second cylindrical terminal conductors together in spaced relationship in substantial overlapping disposition of cylindrical body portions and also of flange portions; said insulated gate switching transistors having substantially equal electrical performance characteristics and symmetrically, radially and circumferentially disposed within said chamber in proximity to said first and second flanges for reducing electrical inductance and resistance therebetween; an input electrical connection between each of said insulated gate switching transistors and said first flange to provide symmetry in input connection resistance and inductance; an output electrical connection between each of said insulated gate switching transistors and said second flange to provide symmetry in output connection resistance and inductance; at least a portion of said input and output electrical connections for each insulated gate switching transistor in substantially parallel disposition to each other at least in one plane, and in proximity to reduce net electrical inductance of said input and output electrical connections; a gate conductor means having a first portion disposed within said chamber and adapted to supply substantially equal gate voltage to each of said insulated gate switching transistors, and further having a terminal portion disposed outside said chamber for connection to a source of gate control voltage, said first portion including a circuit pattern in said housing surrounding the symmetrical disposition of said insulated gate switching transistors, said circuit pattern including a gate conductor pattern for said insulated gate switching transistors; and gate electrical connections between gate electrodes on each of said insulated gate switching transistors and said gate conductor means, whereby said transistors each operate at a predetermined current level.

Claim 11

The module of claim 8 wherein the coaxial terminal members comprise a subassembly affixed to the housing baseplate, at least one of the coaxial terminals includes a threaded bore for attachment of an electrical bus conductor, the baseplate contains a recess, and a surface of said subassembly contacting said baseplate contains a complementary boss nested in said recess, effective to provide a mechanical lock against rotation when said bus conductor is bolted to said subassembly.

Claim 12

The module of claim 8 wherein the coaxial terminal members are spaced by a dielectric plastic having a cylindrical portion and a flanged portion analogous to that of said coaxial terminal members, and said dielectric plastic and said coaxial terminal members comprise a molded unitary subassembly.

Claim 13

The module of claim 10 wherein said first cylindrical terminal conductor is disposed outside said second cylindrical terminal conductor, and the molded unitary assembly includes additional dielectric plastic within said second cylindrical terminal conductor and between said second cylindrical terminal conductor and said chamber.

Claim 14

The module of claim 8 wherein said first cylindrical terminal conductor is disposed outside said second cylindrical terminal conductor, and said second cylindrical terminal conductor has a cylindrical body portion that contains integral mounting bolt means.

Claim 15

The module of claim 8 wherein said first cylindrical terminal conductor is disposed outside said second cylindrical terminal conductor, and said second cylindrical terminal conductor has a cylindrical body portion that is hollow, the hollow has axially opposite openings, one of the openings is adjacent the housing baseplate and is large enough to accommodate a mounting bolt head, the other opening is not large enough to accommodate said bolt head but is large enough to accommodate a tool for coaction with said bolt head, a module mounting bolt having such a head and a shank, the bolt is recessable in the hollow with its head adjacent said other opening, the baseplate closes the one opening, the baseplate has an opening to said hollow that is big enough to allow the shank of said bolt to pass through but not the bolt head, effective to form an assembly having a trapped mounting bolt recessable within said hollow.

Claim 16

The module of claim 8 wherein the module housing has a mounting bolt and the mounting bolt compresses a frusto-conical spring-like washer, effective to maintain a predetermined clamping force between a baseplate of the module housing and a module support.

Claim 17

The module of claim 14 wherein the module housing baseplate has a hole in it, the module mounting bolt has a head and a shank, the shank of the mounting bolt is axially movable through the baseplate hole, and the frusto-conical spring-like washer encircles the mounting bolt shank between the mounting bolt head and the baseplate, effective to allow said bolt head not only clamp said baseplate against a support but also to provide integral means for assisting in maintaining the predetermined clamping force during temperature cycling of the module.

Claim 18

A high power semiconductor device module such as described in claim 8 in which said plurality of insulated gate bipolar transistors collectively comprise a single switch.

Claim 19

A high power semiconductor device module such as described in claim 8 in which a third cylindrical terminal conductor is coaxially nested around said first and second cylindrical terminal conductors, said plurality of transistors collectively comprise two groups of transistors and each group comprises a switch, the first and second coaxial flanged terminal conductors are connected only to one of said groups, said gate conductor means and said gate electrical connection means are connected to said one group of transistors, the second and third cylindrical terminal conductors are connected to the other group of transistors, and an additional gate conductor means and an additional gate electrical connection means are connected to the other group of transistors, effective to provide a separate means for gate potential control to the gate electrodes on the transistors of each group.

Claim 20

The module as recited in claim 17 that additionally contains means to provide the same voltage to the gate electrodes of the transistors of both switches.

Claim 21

A high power semiconductor device module such as described in claim 8 in which a trimmable resistance unit is included in series with the gate electrode of at least one of said transistors to supply substantilly equal gate voltage to each of said transistors.

Claim 22

The module of claim 8 wherein a beam trimmable resistance is electrically in series with the gate electrodes of all of said transistors for closely matching voltage applied to each transistor gate electrode from said terminal portion of said gate conductor means.

Claim 23

A high power module such as described in claim 8 in which a trimmable resistance unit is included in series with the gate electrode of each of said transistors for setting voltage applied to each transistor to a predetermined level when a gate control voltage of a given level is applied to the terminal portion of the gate conductor means.

Claim 24

A high power module such as described in claim 8 wherein all of said input electrical connections, and all of said output electrical connections have a similar inductance and resistance.

Claim 25

The module of claim 8 wherein said chamber contains a plurality of discrete similar insulating substrates, each of said substrates has a single insulated gate switching transistor chip mounted on it, and each of said substrates is supported on said baseplate in intimate similar thermal contact therewith.

Claim 26

The module of claim 8 wherein the module also includes a plurality of circumferentially symmetrically arrayed dielectric substrate members, all of said insulated gate switching transistors are disposed on said substrates and each of the substrate members supports only one of the insulated gate switching transistors.

Claim 27

The module of claim 8 wherein the insulated gate switching transistors are insulated gate bipolar transistors, the transistors are matched in performance, each transistor is disposed on a separate chip, each chip is disposed on a separate substrate, the substrates are symmetrically arrayed around the circumferential terminal flanges, and said substrates are symmetrically spaced from the terminal flanges not further than about a maximum planar dimension of one of said chips.

Claim 28

The module of claim 25 wherein the substrates are predominantly of a wafer of dielectric material and the wafer is metallized on its opposite faces.

Claim 29

A semiconductor switching device module of reduced inductance comprising: a housing defining a chamber; a first terminal member having a cylindrical body portion and at least one flange, and also having a first inductance; a second terminal member that has a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that further has at least one flange, and also has a second inductance that is substantially similar to said first inductance; a spacing between said first and second terminal members, including their flanges, effective to allow said first and second inductances to negate one another; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber in a generally symmetrical array that encircles said terminals, including their flanges; a radially outwardly spacing of each of said substrates from a respective flange portion of each of said terminals, said spacing not being further than about a maximum dimension of one of said switching transistor chips; and a circuit pattern surrounding the symmetrical array of insulated gate switching transistor chips, said circuit pattern including a gate conductor pattern for said switching transistor chips, an input kelvin conductor pattern and an output kelvin conductor pattern.

Claim 30

A semiconductor switching device module of reduced inductance comprising: a housing defining a chamber; a first terminal member having a cylindrical body portion and at least one flange, and also having a first inductance; a second terminal member that has a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that further has at least one flange, and also has a second inductance that is substantially similar to said first inductance; a spacing between said first and second terminal members, including their flanges, effective to allow said first and second inductances to negate one another; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber in a generally symmetrical array that encircles said terminals, including their flanges; a radially outwardly spacing of each of said substrates from a respective flange portion of each of said terminals, said spacing not being further than about a maximum dimension of one of said switching transistor chips; and a circuit pattern surrounding the symmetrical array of insulated gate switching transistor chips, said circuit pattern including a gate conductor pattern for said switching transistor chips, an input kelvin conductor pattern and an output kelvin conductor pattern.

Claim 31

The module of claim 27 wherein the circuit pattern is on a circuit board and the circuit board includes at least one trimmable resistor in series with a connector to a gate electrode on one of the insulated gate switching transistor chips, for matching gate voltage applied to said devices.

Claim 32

The module of claim 28 wherein the circuit pattern is a thick film pattern on a porcelainized circuit board and includes a trimmable thick film printed resistor in series with a connector to each of the insulated gate switching transistor chips, effective to provide means for setting gate voltage to each of said transistor chips to a predetermined value when a given voltage is applied to the gate conductor of said circuit pattern.

Claim 33

A high power semiconductor device module such as described in claim 27 in which said the plurality of insulated gate switching transistor chips in said chamber are insulated gate bipolar transistors and said transistors collectively comprise two switches.

Claim 34

A semiconductor switching device module of reduced inductance comprising: a housing having a baseplate and defining a chamber; a first terminal member having a cylindrical body portion and at least one radially outwardly circumferential flange, and also having a first inductance; a second terminal member having a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that has at least one radially outwardly circumferential flange, and also has a second inductance that is substantially similar to said first inductance; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber on said baseplate in a generally symmetrical array that encircles said terminals, including their circumferential flanges; a spacing between said first and second terminal members, including their circumferential flanges, effective to allow said first and second inductances to negate each other; and said terminal members spaced by a dielectric plastic having a cylindrical portion and a flanged portion analogous to that of said coaxial terminal members, said plastic and said terminal members comprising a molded unitary subassembly.

Claim 35

A semiconductor switching device module of reduced inductance comprising: a housing having a baseplate and defining a chamber; a first terminal member having a cylindrical body portion and at least one radially outwardly circumferential flange, and also having a first inductance; a second terminal member having a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that has at least one radially outwardly circumferential flange, and also has a second inductance that is substantially similar to said first inductance; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber on said baseplate in a generally symmetrical array that encircles said terminals, including their circumferential flanges; a spacing between said first and second terminal members, including their circumferential flanges, effective to allow said first and second inductances to negate each other; and said terminal members spaced by a dielectric plastic having a cylindrical portion and a flanged portion analogous to that of said coaxial terminal members, said plastic and said terminal members comprising a molded unitary subassembly.

Claim 36

A semiconductor switching device module of reduced inductance comprising: a housing having a baseplate and defining a chamber; a first terminal member having a cylindrical body portion and at least one radially outwardly circumferential flange, and also having a first inductance; a second terminal member having a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that has at least one radially outwardly circumferential flange, and also has a second inductance that is substantially similar to said first inductance; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber on said baseplate in a generally symmetrical array that encircles said terminals, including their circumferential flanges; a spacing between said first and second terminal members, including their circumferential flanges, effective to allow said first and second inductances to substantially negate each other; and the body portion of one of the coaxial terminals is not only disposed within the body portion of the other terminal, but also contains integral mounting bolt means.

Claim 37

A semiconductor switching device module of reduced inductance comprising: a housing having a baseplate and defining a chamber; a first terminal member having a cylindrical body portion and at least one radially outwardly circumferential flange, and also having a first inductance; a second terminal member having a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that has at least one radially outwardly circumferential flange, and also has a second inductance that is substantially similar to said first inductance; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber on said baseplate in a generally symmetrical array that encircles said terminals, including their circumferential flanges; a spacing between said first and second terminal members, including their circumferential flanges, effective to allow said first and second inductances to substantially negate each other; and the body portion of one of the coaxial terminals is not only disposed within the body portion of the other terminal, but also contains integral mounting bolt means.

Claim 38

The module of claim 32 wherein the integral mounting bolt means includes a hollow in the body portion of the one terminal member, the hollow has axially opposite openings, one of the openings is adjacent the baseplate and is large enough to accommodate a mounting bolt head, the other opening is not large enough to accommodate said bolt head but is large enough to accommodate a tool for coaction with said bolt head, a module mounting bolt having such a bolt head and a shanks, the bolt is recessable in the hollow with its head adjacent the other opening, the baseplate closes the one opening, the baseplate has an opening to said hollow that is big enough to allow the shank of said bolt to pass through but not its head, effective to form an assembly having a trapped mounting bolt recessable within said hollow.

Claim 39

The module of claim 32 wherein the integral mounting bolt means includes a mounting bolt and the mounting bolt compresses a frusto-conical spring-like washer, effective to maintain a predetermined clamping force between a baseplate of the module housing and a module support.

Claim 40

The module of claim 32 wherein the module baseplate has a hole in it and the module mounting bolt means includes a mounting bolt having a head and a shank, the shank of the mounting bolt is axially movable through the baseplate hole, and a frusto-conical spring-like washer encircles the mounting bolt shank between the mounting bolt head and the baseplate, effective to allow said bolt head not only clamp said baseplate against a support but also to provide integral means for assisting in maintaining a predetermined clamping force during temperature cycling of the module.

Claim 41

A high power semiconductor device module capable of operating at high frequency and low parasitic losses comprising: a housing defining a chamber and including a baseplate and a cover; a first cylindrical terminal conductor of a given composition and having an axis perpendicular to said baseplate and a first outwardly extending circumferential flange, said first flange disposed within said chamber parallel to said baseplate for connection to a plurality of high power insulated gate switching transistors in said chamber, and an end of said first terminal conductor disposed outside said chamber for connection to a first external bus, said first terminal conductor having a given electrical resistance and inductance with respect to electrical current flow therethrough; a second cylindrical terminal conductor including a second flange disposed within said chamber for connection to said plurality of high power insulated gate switching transistors and further including an end of said second terminal conductor disposed outside said chamber for connection to a second external bus, effective to permit coaxial nesting of said first and second cylindrical terminal conductors together in spaced relationship in substantial overlapping disposition of cylindrical body portions and also of flange portions; said insulated gate switching transistors having substantially equal electrical performance characteristics and symmetrically, radially and circumferentially disposed within said chamber in proximity to said first and second flanges for reducing electrical inductance and resistance therebetween; an input electrical connection between each of said insulated gate switching transistors and said first flange to provide symmetry in input connection resistance and inductance; an output electrical connection between each of said insulated gate switching transistors and said second flange to provide symmetry in output connection resistance and inductance; at least a portion of said input and output electrical connections for each insulated gate switching transistor in substantially parallel disposition to each other at least in one plane, and in proximity to reduce net electrical inductance of said input and output electrical connections; a gate conductor means having a first portion disposed within said chamber and adapted to supply substantially equal gate voltage to each of said insulated gate switching transistors, and further having a terminal portion disposed outside said chamber for connection to a source of gate control, said first portion including a circuit pattern in said housing surrounding the symmetrical disposition of said insulated gate switching transistors, said circuit pattern including a gate conductor pattern for said insulated gate switching transistors, an input kelvin conductor pattern and an output kelvin conductor pattern; and gate electrical connections between gate electrodes on each of said insulated gate switching transistors and said gate conductor mans, whereby said transistors each operate at a predetermined current level.

Claim 42

A high power semiconductor device module capable of operating at high frequency and low parasitic losses comprising: a housing defining a chamber and including a baseplate and a cover; a first cylindrical terminal conductor of a given composition and having an axis perpendicular to said baseplate and a first outwardly extending circumferential flange, said first flange disposed within said chamber parallel to said baseplate for connection to a plurality of high power insulated gate switching transistors in said chamber, and an end of said first terminal conductor disposed outside said chamber for connection to a first external bus, said first terminal conductor having a given electrical resistance and inductance with respect to electrical current flow therethrough; a second cylindrical terminal conductor including a second flange disposed within said chamber for connection to said plurality of high power insulated gate switching transistors and further including an end of said second terminal conductor disposed outside said chamber for connection to a second external bus, effective to permit coaxial nesting of said first and second cylindrical terminal conductors together in spaced relationship in substantial overlapping disposition of cylindrical body portions and also of flange portions; said insulated gate switching transistors having substantially equal electrical performance characteristics and symmetrically, radially and circumferentially disposed within said chamber in proximity to said first and second flanges for reducing electrical inductance and resistance therebetween; an input electrical connection between each of said insulated gate switching transistors and said first flange to provide symmetry in input connection resistance and inductance; an output electrical connection between each of said insulated gate switching transistors and said second flange to provide symmetry in output connection resistance and inductance; at least a portion of said input and output electrical connections for each insulated gate switching transistor in substantially parallel disposition to each other at least in one plane, and in proximity to reduce net electrical inductance of said input and output electrical connections; a gate conductor means having a first portion disposed within said chamber and adapted to supply substantially equal gate voltage to each of said insulated gate switching transistors, and further having a terminal portion disposed outside said chamber for connection to a source of gate control, said first portion including a circuit pattern in said housing surrounding the symmetrical disposition of said insulated gate switching transistors, said circuit pattern including a gate conductor pattern for said insulated gate switching transistors, an input kelvin conductor pattern and an output kelvin conductor pattern; and gate electrical connections between gate electrodes on each of said insulated gate switching transistors and said gate conductor mans, whereby said transistors each operate at a predetermined current level.

Claim 43

The module of claim 36 wherein the insulated gate switching transistors are insulated gate bipolar transistors, the circuit pattern is on a circuit board and the circuit board includes at least one trimmable resistor in series with a connector to the gate electrode on one of the insulated gate bipolar transistors, for equalizing voltage applied to the gate electrodes of said transistors from said terminal portion of said gate conductor means.

Claim 44

The module of claim 36 wherein the circuit pattern is a thick film pattern on a porcelainized steel circuit board and includes a trimmable thick film printed resistor in series with a connector to the gate electrode on each of the insulated gate switching transistors, effective to provide means for setting voltage applied to the gate electrode of each of said transistors to a predetermined value when a given voltage is applied to the gate conductor of said circuit pattern from said terminal portion of said gate conductor means.

Claim 45

A semiconductor switching device module of reduced inductance comprising: a housing defining a chamber; a first terminal member having a cylindrical body portion and at least one flange, and also having a first inductance; a second terminal member that has a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that further has at least one flange, and also has a second inductance that is similar to said first inductance; a spacing between said first and second terminal members, including their flanges, effective to allow said first and second inductances to negate one another; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber in a generally symmetrical array that encircles said terminals, including their flanges; a radially outwardly spacing of each of said substrates from a respective flange portion of each of said terminals, said spacing not being further than about a maximum dimension of one of said switching transistor chips; and a circuit pattern surrounding the symmetrical array of insulated gate switching transistor chips, said circuit pattern including a gate conductor pattern for said switching transistor chips.

Claim 46

A semiconductor switching device module of reduced inductance comprising: a housing defining a chamber; a first terminal member having a cylindrical body portion and at least one flange, and also having a first inductance; a second terminal member that has a cylindrical body portion that is coaxial and concentric with said first terminal member body portion and that further has at least one flange, and also has a second inductance that is similar to said first inductance; a spacing between said first and second terminal members, including their flanges, effective to allow said first and second inductances to negate one another; a plurality of insulating substrates, each of which contains only one insulated gate switching transistor chip; said substrates disposed in said chamber in a generally symmetrical array that encircles said terminals, including their flanges; a radially outwardly spacing of each of said substrates from a respective flange portion of each of said terminals, said spacing not being further than about a maximum dimension of one of said switching transistor chips; and a circuit pattern surrounding the symmetrical array of insulated gate switching transistor chips, said circuit pattern including a gate conductor pattern for said switching transistor chips.