Low profile, highly configurable, current sharing paralleled wide band gap power device power module

Abstract

A method of making a power module includes providing a base plate defining a topology pattern, providing a power substrate above the base plate, providing at least two power contacts and arranging solder catches in the at least two power contacts, soldering the at least two power contacts to the power substrate utilizing the solder catches, and securing a housing to the power substrate.

Claims

1. A power module apparatus, comprising: a base plate defining a topology pattern; a power substrate positioned above the base plate; at least two power contacts, each of the at least two power contacts electrically connected to the power substrate; and a housing secured to the power substrate, wherein the power module comprises a height that is less than 20 mm.

2. The power module according to claim 1, wherein the height is at least three times thinner than prior art power modules.

3. The power module according to claim 1 wherein the height is 10 mm or less.

4. The power module according to claim 1 further comprising solder catches arranged on the at least two power contacts, wherein the at least two power contacts are soldered to the power substrate through the solder catches.

5. The power module according to claim 1 further comprising: a gate and source board provided above the power substrate; gate drive connectors electrically connected to the gate and source board; at least two parallel shared current path power devices electrically connected to the at least two power contacts; and the gate drive connectors and the at least two power contacts are configured to extend through the housing.

6. The power module according to claim 5 wherein the gate and source board comprises a plurality of interconnection channels being configured in one of a plurality of positions to provide a plurality of power module configurations.

7. The power module according to claim 1 wherein the power module is configured to implement at least one of a plurality of power electronic topologies including at least one of the following: a half bridge, a common source, and a common drain.

8. The power module according to claim 1 wherein the power module is configured to receive one of a plurality of different gate and source board configurations; and wherein each one of the plurality of different gate and source board configurations comprise a different configuration of a plurality of interconnection channels.

9. The power module according to claim 1 wherein the power module is configured to utilize up to 60% of a total footprint area for conduction of power.

10. The power module according to claim 1 further comprising a plurality of power devices, wherein the plurality of power devices are evenly spaced across the power substrate.

11. A power module apparatus, comprising: a base plate defining a topology pattern; a power substrate positioned above the base plate; at least two power contacts, each of the at least two power contacts electrically connected to the power substrate; solder catches arranged on the at least two power contacts; and a housing secured to the power substrate.

12. The power module according to claim 11 wherein the power module comprises a height that is at least two times thinner than prior art power modules.

13. The power module according to claim 11 wherein the at least two power contacts are soldered to the power substrate through the solder catches.

14. The power module according to claim 11 further comprising: a gate and source board provided above the power substrate; gate drive connectors electrically connected to the gate and source board; at least two parallel shared current path power devices electrically connected to the at least two power contacts; and the gate drive connectors and the at least two power contacts are configured to extend through the housing.

15. The power module according to claim 11 wherein the power module is configured to implement at least one of a plurality of power electronic topologies including at least one of the following: a half bridge, a common source, and a common drain.

16. The power module according to claim 11 wherein the power module is configured to receive one of a plurality of different gate and source board configurations; and wherein each one of the plurality of different gate and source board configurations comprise a different configuration of a plurality of interconnection channels.

17. The power module according to claim 11 wherein the power module is configured to utilize up to 60% of a total footprint area for conduction of power.

18. The power module according to claim 11 further comprising a plurality of power devices, wherein the plurality of power devices are evenly spaced across the power substrate.

19. A power module apparatus, comprising: a base plate defining a topology pattern; a power substrate positioned above the base plate; at least two power contacts, each of the at least two power contacts electrically connected to the power substrate; and a housing secured to the power substrate, wherein each of the at least two power contacts comprise a bonding surface, a body portion connected to the bonding surface through a first bent portion, and a contact connected to the bonding surface through a second bent portion.

20. The power module according to claim 19 wherein the power module comprises a height that is at least two times thinner than prior art power modules.

21. The power module according to claim 19 wherein the power module comprises a height of 10 mm or less.

22. The power module according to claim 19 further comprising: a gate and source board provided above the power substrate; gate drive connectors electrically connected to the gate and source board; at least two parallel shared current path power devices electrically connected to the at least two power contacts; and the gate drive connectors and the at least two power contacts are configured to extend through the housing.

23. The power module according to claim 19 wherein the power module is configured to receive one of a plurality of different gate and source board configurations; and wherein each one of the plurality of different gate and source board configurations comprise a different configuration of a plurality of interconnection channels.

24. The power module according to claim 19 wherein the power module is configured to utilize up to 60% of a total footprint area for conduction of power.

25. The power module according to claim 19 further comprising a plurality of power devices, wherein the plurality of power devices are evenly spaced across the power substrate.

26. A power module apparatus, comprising: a base plate defining a topology pattern; a power substrate provided above the base plate; at least two power contacts electrically connecting to the power substrate; and a housing secured to the power substrate, wherein the power module comprises a height of 10 mm or less.

27. The power module according to claim 26 wherein the height is at least two times thinner than prior art power modules.

28. The power module according to claim 26 further comprising: a gate and source board provided above the power substrate; gate drive connectors electrically connected to the gate and source board; and at least two parallel shared current path power devices electrically connected to the at least two power contacts, wherein the gate drive connectors and the at least two power contacts are configured to extend through the housing.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) In the following drawings, which form a part of the specification and which are to be construed in conjunction therewith, and in which like reference numerals have been employed throughout wherever possible to indicate like parts in the various views:

(2) FIG. 1 shows a perspective view of the power module.

(3) FIG. 2 shows an exploded view of the power module.

(4) FIG. 3 shows a relative size to thickness comparison of the power module.

(5) FIG. 4 shows the equalized current flow for multiple paralleled devices.

(6) FIG. 5 shows the power contact design.

(7) FIG. 6 shows the low profile power contact bending.

(8) FIG. 7 shows the power module base plate.

(9) FIG. 8 shows the gate and source kelvin secondary substrate.

(10) FIG. 9 shows the gate & source kelvin board half bridge arrangement.

(11) FIG. 10 shows the gate & source kelvin board common source arrangement.

(12) FIG. 11 shows the gate & source kelvin board common drain arrangement.

(13) FIG. 12 shows the single layer modular gate and source kelvin example layout.

(14) FIG. 13 shows the power substrate half bridge arrangement.

(15) FIG. 14 shows the power substrate common source arrangement.

(16) FIG. 15 shows the power substrate common drain arrangement.

(17) FIG. 16 shows the high temperature plastic housing topside features.

(18) FIG. 17 shows the high temperature plastic housing backside features.

(19) FIG. 18 shows the housing attached to power module assembly.

(20) FIG. 19 shows the power contact guides.

(21) FIG. 20 shows the half bridge, single channel common source or drain module.

(22) FIG. 21 shows the full bridge, dual channel common source or drain module.

(23) FIG. 22 shows the extended single housing side-by-side module configuration.

DETAILED DESCRIPTION OF THE DISCLOSURE

(24) As shown in FIG. 1 of the drawings, one exemplary aspect of the present disclosure is generally shown as a power module 100. The power module 100 may be configurable in multiple useful power electronic topologies such as half bridge, full bridge, common source, and common drain, and can be configured in up to two separate channels. It is uniquely suited to take advantage of all wide band gap technology has to offer, while being flexible enough to meet the demands of many customer systems through custom configurations.

(25) The power module 100 may include the primary elements outlined in FIG. 2. These elements may include the base plate 200, power substrate 300, power contacts 400, power devices 500, gate and source kelvin interconnection board 600, gate drive connectors 700, injection molded housing 800, and fasteners 900.

(26) Specific focus was placed on using a footprint common in the power electronics industry, a 62 mm107 mm base plate 200 with M6 mounting holes 48 mm93 mm apart. This configuration may allow for customers with existing systems to evaluate these high performance modules without investing in a complete system redesign.

(27) While the length and width of the module 100 may fit industry standards, the height of the module is 2 to 3 thinner than contemporaries. It is 10 mm thick in total. This may dramatically reduce the module inductance and increase current carrying capability partially by utilizing lower path lengths. It may also provide a major source of system level volume savings in a power converter.

(28) The comparison of top size to thickness dimensions of the power module 100 are presented in FIG. 3 in the top and side view comparison. The module 100 measures 65 mm110 mm10 mm. The plastic housing 800 may extend like a sheath over the base plate 200 for voltage isolation, which may account for the extra 3 mm on each side over the base plate 200 dimensions. It may have a volume of 71.5 cm.sup.3 and weigh approximately 140 g.

(29) The power module 100 may utilize 57.5 mm73 mm, 42 cm.sup.2, of the total footprint area for conduction. This represents an impressive 60% utilization solely for current carrying. The remaining area is used for mounting, 5%, gate drive connections, 5%, and plastic features including minimum wall thickness, voltage creepage extenders, and strengthening ribs, 30%.

(30) Power Loop

(31) As noted by FIG. 4, the driving focus of the power module 100 power loop 110 may effectively parallel a large number of devices 500. Shown are a first power device 501, second power device 502, third power device 503, fourth power device 504, fifth power device 505, sixth power device 506, seventh power device 507, eight power device 508, ninth power device 509, tenth power device 510, and eleventh power device 511. The module 100 can either have two or four switch positions, depending on configuration, which is detailed later. FIG. 4 shows the upper position 480 and the lower position 490. This allows for a large amount of flexibility in the formation of each switch position, such that they may be tailored to specific applications without costly module 100 modifications. For example, the positions may have an equal number of diodes to the power switches 500, only a few diodes, or none at all. FIG. 4 is a representation of the power loop 110, depicting the even, shared current paths 120 for current traveling from the 20 V+ terminal 410 to the Mid terminal 420, the V-terminal 430 is also shown that is used for devices 500 in the lower position 490. An additional benefit of this layout is that the even spacing of each device 500 may aid in the spreading of the heat sources across the module 100 instead of concentrating them in a few locations.

(32) As displayed in FIG. 4, nearly the entire width of the power module 100 is utilized for the conduction of current. Many benefits would be lost if the module 100 was too tall. In the worst case, the length the current might travel through the power contact 410, 420, 430 might be longer than the path it travels once it reaches the substrates 300. Accordingly, the power contacts 400 were designed to have a relatively low height such that they contribute a negligible amount to the resistance and inductance of the system.

(33) The relatively low height of the power contacts 400 was achieved by using a dual bending process. First, the power contacts 400 may be formed through either a metal stamping operation or by etching followed by forming in a press brake. The 90 bend at the base 450 may create an L shaped connector with a vertical body 460. The base 450 may be soldered down to the power substrates 300. The base 450 may be relatively thin in comparison to the overall shape. This may reduce the area consumed by this bond, allowing for more active device 500 area inside of the module 100. To improve adhesion of this thin bond, staggered holes called solder catches 454 may be etched or formed along the bonding surface 452 on the bottom of the base 450. Molten solder travels up the catches 454 through capillary action. Once solidified, the solder inside of the catches 454 substantially improves bond strength in many directions. An exemplary contact 400 with solder catches 454 is presented in FIG. 5.

(34) Also shown in FIG. 5 is how the L shaped contacts 400 may be bent a second time at the end of the fabrication process to form a contact top 470. Before bending, the vertical body 460 of the contact 400 allows for single piece plastic housing 800 to be dropped into place, as there may be no undercuts present. The radius of the second bend 472 may not be as tight as the first bend 462. This provides some tolerance in the process and is a smoother bending operation. The second radius 472 may be facilitated through a pre-formed radius 810 in the plastic housing 800, which, at this stage, is touching the leading edge 464 of the contacts 400. Specifically designed rotating bending hardware presses flatly on the opposite surface 466, folding the contacts 400 down over the captive fasteners 900. An illustration of the bending of the L shaped contacts into C shaped forms is pictured in FIG. 6.

(35) Underneath the folded contacts 400 are low profile threaded fasteners 900 shown as nuts 900. These fasteners 900 are captured underneath the power contacts 400. They are otherwise loose. The captive fasteners 900 serve an important purpose. When the module 100 is bolted to buss bars, the loose fasteners 900 and the contacts 400 may be pulled upwards into the bussing, creating a quality electrical connection. If the fasteners 900 were affixed to the housing 800, they could act to pull the bussing down into the module 100 and could create a poor connection due to the stiffness of the buss bars.

(36) Base Plate

(37) The base plate 200 is a critical element of the module, providing mechanical support, heat spreading, and a means to effectively bolt down to a heat sink or cold plate. The material properties of the base plate 200 become increasingly important as the temperature of operation elevates. An effective example is found in the coefficient of thermal expansion, CTE, where materials in the assembly expand at different rates due to heat and may create large stresses in their interfaces.

(38) The power module 100 utilizes a Metal Matrix Composite, MMC, material, which is a composite of a high conductivity metal, copper, aluminum, etc., and either a low CTE metal such as moly, beryllium, tungsten, or a nonmetal such as silicon carbide, beryllium oxide, graphite. These composite materials combine the best features of each contributing element, allowing for a high thermal conductivity with a CTE which is matched with the power substrate 300 to which it is attached.

(39) FIG. 7 shows how the power module 100 base plate 200 was designed to match an industry standard 62 mm geometry, which has a set diameter and location for the mounting holes 203 in the corners. The thickness of the plate 200 was fine-tuned through the use of parametric finite element analysis of the CAD model. This was achieved by sweeping the thickness between pre-defined practical limits and measuring the thermal and mechanical responses. The material and thickness combinations that achieved the best thermal performance with a minimal mechanical deflection were selected. Additional features of the power module 100 plate may include machined or molded, depending on the MMC material, standoffs 210 with a threaded board hole 212, and housing hole 290 each. The standoff 210 provides a planar surface with the power substrate 300 such that the internal gate & source kelvin board 600 can be bolted down without bowing.

(40) Gate Drive Loop

(41) Independent electrical paths for each switch position are required to form gate and source kelvin connections, which are necessary for controlling the power switches. This may become difficult with the number of devices 500 in parallel, as ideally the gate and source kelvin routing would not interfere with the wide, equalized power paths.

(42) FIG. 8 shows how the power module 100 and its variations include a single piece secondary substrate 600 which is placed over the power substrate 300 and then bolted down to the base plate 200. As shown in FIGS. 8 through 11, the gate and source kelvin substrate 600 has two interconnection channels 602, 604 which may be located in one of four positions top or first 611, upper middle or second 612, lower middle or third 613, and bottom or fourth 614 to define die apertures such as an external die aperture 603 or middle die aperture 605 to allow for a multitude of module 100 configurations. Essentially, the relative layout of each interconnection channel 602, 604 may be the same; however, the location and direction may be adapted to match the associated die aperture 603, 605 and die 500 placement and rotation to match each topology. This is illustrated in FIG. 9, FIG. 10, and FIG. 11 with the arrows indicating the gate direction for a half bridge, common source, and common drain topology, respectively. Each of those may consist of a single or dual channel arrangement, depending on the layout of the power substrate 300 and the format of the power contacts 400 and housing 800.

(43) As shown in FIG. 12, to aid in paralleling, individual ballast resistors 640 may be included on the interconnection board 600. While there are many different layouts these boards can utilize such as parallel planes, clock tree distribution, etc., one of the more effective is a low cost single layer modular arrangement with many bonding locations 642. As shown, a gate track 650 and source track 652 go across the length of the interconnection channels 654. Source wire bonds are formed directly on the source track 652. Each gate is bonded to individual gate pads 651 which are connected to the gate track through resistors 640. The values of the resistors 640 are device and application dependent and will vary between module 100 configurations.

(44) Power Substrate

(45) FIG. 13 shows the power substrate 300 which may be a metal-ceramic-metal layered structure designed to handle very high currents and voltages with the arrows again showing the gate direction to be matched with the boards 600. Metals may be copper or aluminum at varying thicknesses, while the ceramic materials are typically alumina, Al203, aluminum nitride, AlN, or silicon nitride, Si3N4. The metal layers 302 may be etched into topology specific patterns 330, 340 350 as illustrated in FIG. 13 for a half bridge substrate 330, FIG. 14 for a common source substrate 340, and FIG. 15 for a common drain substrate 350 showing the upper and lower die 500 positions for each configuration. Also note that each of these layouts may be split into a dual channel arrangement by etching a line down the center of the substrates 300. They may also be split into individual substrates per channel if desired. This may be useful for more harsh environments as the smaller substrates will experience less stress.

(46) Housing

(47) The housing 800 may be formed in an injection molding process with reinforced high temperature plastic. The housing 800 may serve many functions in addition to being a protective barrier to the sensitive semiconductors 500. These functions may include voltage blocking, mechanical support for the captive fasteners 900, guides for the power contact bending process, entry zones for gel passivation, vents for the gel passivation process, and self-strengthening internal ribs 812. Many of these features are depicted in FIG. 16 and FIG. 17. High aspect ratio trenches may be placed around the periphery of the power contacts 400 to increase the surface distance between exposed metal contacts, increasing voltage blocking capability.

(48) FIG. 16 shows the high temperature plastic housing topside features including the creepage extenders 802, the passivation entries and vents 804, the captive fasteners apertures 806, the labeling area 808, and the power contact pinch and radius 810. FIG. 17 shows the backside features including the strengthening ribs 812, the thick bolt hole core sections 814, the bolt head clearance recess 816, the bottoms of the fastener insets 818, the power contact entryways 820, and the wire bond clearance apertures 822.

(49) FIG. 18 shows how the housing 800 slides over the electronic sub assembly to form the top of the module 100, with the power contacts 400 routed through the narrow openings 820. The housing 800 may be bolted 830 at two points to threaded holes 290 on the base plate 200. At this stage the gel passivation material is injected into the module 100 and fully cured. Multiple openings and vents 804 assist this assembly step. The slices 820 in the housing 800 for the power contacts 400 have drafted guides to aid this process, and a rounded fillet 810 on top to aid in the bending procedure. These are illustrated in FIG. 19.

(50) Configurability

(51) As discussed earlier n this document, the power module 100 may be configurable in a variety of useful power electronic topologies. These topologies may include half bridge, common source, and common drain. Splitting the channels, through layout changes in the power substrate 300 and gate and source kelvin board 600 and alterations to the power contacts 400 and housing 800, allows three more configurations, including a full bridge, common source dual channel, and common drain dual channel.

(52) FIG. 20 displays the first external configuration 150 for half bridge, single channel common source, and single channel common drain configurations. There may be four locations 701, 702, 703, 704 for the gate driver connections 700, two on each side. Either or both sides may be used for this purpose. For the dual channel arrangement 152, shown in FIG. 21, the power contacts 400 are split and provide two fully isolated channels. Gate drive connectors 700 on both sides are now required. This arrangement may be used for a full bridge, dual channel common source, and dual channel common drain topologies.

(53) For higher currents and for customers who desire a single module, a larger side-by-side arrangement of a dual power module 200 may be fabricated from two modules built side by side into a single housing 800. This is illustrated in FIG. 22.

(54) Reference numerals used throughout the detailed description and the drawings correspond to the following elements:

(55) power module 100

(56) power loop 110

(57) shared current paths 120

(58) first external configuration 150

(59) dual channel arrangement 152

(60) base plate 200

(61) mounting holes 203

(62) standoffs 210

(63) threaded holes 212

(64) threaded holes 290

(65) power substrate 300

(66) metal layers 302

(67) first topology pattern half bridge substrate 330

(68) second topology pattern common source substrate 340

(69) third topology pattern common drain substrate 350

(70) power contacts 400

(71) first power contact 410

(72) second power contact 420

(73) third power contact 430

(74) base 450

(75) bonding surface 452

(76) solder catches 454

(77) vertical body 460

(78) first bend 462

(79) leading edge 464

(80) opposite surface 466

(81) contact top 470

(82) second bend 472

(83) upper position 480

(84) lower position 490

(85) power devices 500

(86) first paralleled power device 501

(87) second paralleled power device 502

(88) third paralleled power device 503

(89) fourth paralleled power device 504

(90) fifth paralleled power device 505

(91) sixth paralleled power device 506

(92) seventh paralleled power device 507

(93) eight paralleled power device 508

(94) ninth paralleled power device 509

(95) tenth paralleled power device 510

(96) eleventh paralleled power device 511

(97) gate & source kelvin interconnection board 600

(98) first interconnection channel 602

(99) external die aperture 603

(100) second interconnection channel 604

(101) internal die aperture 605

(102) first interconnection position 611

(103) second interconnection position 612

(104) third interconnection position 613

(105) fourth interconnection position 614

(106) individual ballast resistors 640

(107) bonding locations 642

(108) gate track 650

(109) gate pads 651

(110) source track 652

(111) interconnection channels 654

(112) gate drive connectors 700

(113) first gate driver connection location 701

(114) second gate driver connection location 702

(115) third gate driver connection location 703

(116) fourth gate driver connection location 704

(117) housing 800

(118) creepage extenders 802

(119) passivation entries and vents 804

(120) captive fasteners apertures 806

(121) labeling area 808

(122) power contact pinch and radius 810

(123) strengthening ribs 812

(124) bolt hole core sections 814

(125) bolt head clearance recess 816

(126) fastener insets 818

(127) power contact entryway slices 820

(128) wire bond clearance apertures 822

(129) bolt 830

(130) fasteners 900

(131) From the foregoing, it will be seen that this disclosure well adapted to obtain all the ends and objects herein set forth, together with other advantages which are inherent to the structure. It will also be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims. Many possible embodiments may be made of the disclosure without departing from the scope thereof. Therefore, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

(132) When interpreting the claims of this application, method claims may be recognized by the explicit use of the word method in the preamble of the claims and the use of the ing tense of the active word. Method claims should not be interpreted to have particular steps in a particular order unless the claim element specifically refers to a previous element, a previous action, or the result of a previous action. Apparatus claims may be recognized by the use of the word apparatus in the preamble of the claim and should not be interpreted to have means plus function language unless the word means is specifically used in the claim element. The words defining, having, or including should be interpreted as open ended claim language that allows additional elements or structures. Finally, where the claims recite a or a first element of the equivalent thereof, such claims should be understood to include incorporation of one or more e such elements, neither equiring nor excluding two or more such elements.