WO2024156339A1 - Semiconductor power unit and method for manufacturing a semiconductor power unit - Google Patents

Semiconductor power unit and method for manufacturing a semiconductor power unit Download PDF

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Publication number
WO2024156339A1
WO2024156339A1 PCT/EP2023/051653 EP2023051653W WO2024156339A1 WO 2024156339 A1 WO2024156339 A1 WO 2024156339A1 EP 2023051653 W EP2023051653 W EP 2023051653W WO 2024156339 A1 WO2024156339 A1 WO 2024156339A1
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WO
WIPO (PCT)
Prior art keywords
housing
welding
power module
unit
cooler unit
Prior art date
Application number
PCT/EP2023/051653
Other languages
French (fr)
Inventor
Dominik Truessel
Milad Maleki
Lluis Santolaria
Harald Beyer
Original Assignee
Hitachi Energy Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Energy Ltd filed Critical Hitachi Energy Ltd
Priority to PCT/EP2023/051653 priority Critical patent/WO2024156339A1/en
Publication of WO2024156339A1 publication Critical patent/WO2024156339A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
    • H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K7/00—Constructional details common to different types of electric apparatus
    • H05K7/20—Modifications to facilitate cooling, ventilating, or heating
    • H05K7/2089—Modifications to facilitate cooling, ventilating, or heating for power electronics, e.g. for inverters for controlling motor
    • H05K7/20927—Liquid coolant without phase change
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
    • H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
    • H01L2023/4037—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws characterised by thermal path or place of attachment of heatsink
    • H01L2023/405—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws characterised by thermal path or place of attachment of heatsink heatsink to package
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
    • H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
    • H01L2023/4075—Mechanical elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
    • H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
    • H01L2023/4075—Mechanical elements
    • H01L2023/4081—Compliant clamping elements not primarily serving heat-conduction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/40—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs
    • H01L23/4006—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws
    • H01L2023/4075—Mechanical elements
    • H01L2023/4087—Mounting accessories, interposers, clamping or screwing parts
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
    • H01L23/473—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing liquids

Definitions

  • the present disclosure is related to a semiconductor power unit and a method for manufacturing a semiconductor power unit .
  • Power modules are used in automotive inverters for example and require a cooler to dissipate heat during operation . To enable a stable and secure set up of such power units the power modules are fixed to the cooler by means of screws or screwed clamps .
  • Embodiments of the disclosure relate to a semiconductor power unit which enable stable and secure coupling and which contribute to reliable heat dissipation . Embodiments of the disclosure also relate to a corresponding manufacturing method for such a semiconductor power unit .
  • a semiconductor power unit comprises at least one power module with a baseplate and a housing, and a cooler unit for cooling the at least one power module during operation .
  • the at least one power module is coupled to a housing of the cooler unit by means of welding such that one or more welding j oints are formed between at least two of the housing of the cooler unit , the at least one power module and a coupling element for fixing the at least one power module to the housing of the cooler unit .
  • the semiconductor power unit is feasible that enables a secure and stable coupling between a power module and a cooler unit for liquid cooling and that further contributes to reliable heat dissipation during operation of the power module .
  • the semiconductor power unit is suitable for power modules for use in high voltage applications , for example for a voltage of at least 0 . 5 kV .
  • the welding j oint between the housing of the cooler unit , the at least one power module and/or the coupling element can be formed by means of resistance welding and/or arc welding and/or laser welding .
  • the power module has a substantially rectangular or cuboid form and there can be four welding j oints formed in a vicinity of a respective edge of the cuboid power module , for example .
  • the welding can be done on several locations of each two opposite sides of the power module .
  • the housing of the cooler unit can comprise aluminum .
  • the housing can be made of aluminum entirely or in sections , wherein the housing can comprise aluminum in form of bare aluminum and/or aluminum alloy .
  • the housing can comprise copper and/or a copper alloy .
  • the housing can be made of or comprise any weldable material .
  • the baseplate can comprise aluminum or copper .
  • the baseplate can be made of aluminum or copper entirely or in sections , wherein the baseplate can comprise aluminum or copper in form of bare aluminum or copper and/or aluminum alloy or copper .
  • the baseplate of the power module can be made of or comprise any weldable material .
  • the baseplate can be made of a composite material like AlSiC or MgSiC at least in case of clamping, when the baseplate is not directly welded to the cooler .
  • the housing of the cooler unit and the baseplate comprise the same material or material composition .
  • the aforementioned material options can also apply to the coupling element that can comprise any weldable material i f it is intended for welding .
  • a clamp, a screw and/or a bolt are also made of the aforementioned materials or compositions .
  • a clamp, a screw and/or a bolt are made of steel .
  • a material made of Zinc or Al-Zn alloy can be used for the baseplate , the housing, a clamp, a screw and/or a bolt .
  • the one or more welding j oints are formed directly between an upper surface of the housing of the cooler unit and a lower surface of the baseplate of the power module . Accordingly, the semiconductor power unit can be assembled without any further coupling element and the power module and the cooler unit can be connected by means of welding .
  • the upper surface of the housing reali zes the surface that is facing away from the opposite bottom such that the upper surface not merely describes one or more uppermost portions of the housing but also the upper surface inside a bottom of a recess that is formed at the upper surface of the housing, for example .
  • the baseplate of the power module can comprise one or more recesses at the respective position of the one or more welding j oints . So the thermal impact needed for welding is reduced due to the thinned portion related to a smaller amount of material to be molten of the baseplate or clamp .
  • the semiconductor power unit comprises a coupling element , for example including a clamp, a screw and/or a bolt for fixing the at least one power module to the housing of the cooler unit .
  • the power module is connected to the cooler unit using a screwed clamp and afterwards the connection is reliably secured by means of welding and the formed one or more welding j oints .
  • the coupling element can be reali zed j ust as a clamp holding the power module in place relatively to the cooler unit .
  • the one or more welding j oints can be formed directly between an upper surface of the housing of the cooler unit and a lower surface of the clamp .
  • the clamp can comprise one or more recesses at the respective position of the one or more welding j oints .
  • the coupling element additionally comprises a screw and/or a bolt used for fixing the power module to the cooler unit
  • the clamp comprises one or more recesses at the respective position of the one or more screws and/or bolts are to be inserted .
  • the clamp can comprise a penetrating recess in which the screw or the bolt is arranged .
  • the one or more welding j oints then can be formed between the screw or the bolt and the upper surface of the housing of the cooler unit , inside the penetrating recess of the clamp and/or an upper surface of the clamp facing away from the cooler unit .
  • the screw or bolt can be fixed at a respective screw or bolt head to fix their preassembled holding position .
  • the welding connection can be formed between the screw head and the top surface of the clamp . Moreover, it is possible to directly screw the baseplate to the cooler and the one or more screws are secured by welding by the same methods as described above . According to such an embodiment , the baseplate is configured to receive the screws and comprises corresponding openings .
  • the housing of the cooler unit can comprise one or more recesses in coordination with the one or more penetrating recesses of one or more clamps such that a respective screw or the bolt extends through a penetrating recess of a respective clamp into the associated recess of the housing of the cooler unit .
  • the one or more welding j oints can then be formed between the screw or the bolt and the housing of the cooler unit inside the recess of the housing of the cooler unit .
  • the screw and/or the bolt comprises a respective welding protrusion configured for welding and facing the housing of the cooler unit such that the corresponding welding j oint is formed by melting the welding protrusion .
  • a protrusion is also used to support an ignition of an electric arc in case of arc or resistance welding .
  • a screw or bolt head may have such a protrusion, which face the top surface of the clamp or of the baseplate , i f the baseplate is directly screwed to the cooler . During a welding process the protrusion and a portion of the screw or bolt is molten, respectively .
  • conventional power modules may be mechanically fixed to power units using a clamping and screwing mechanism or direct screwing of the baseplate .
  • Such a conventional configuration including screwed clamps there is a risk of that threaded connections may result in loss of torque and consequently in loss of reliability due to thermal cycling or due to vibrations and thus in the risk of loss of coolant due to leakage in long-term operation .
  • the aforementioned adverse ef fects can be counteracted .
  • the use of the described fixation method of the power modules on the cooler unit can counteract a loosening of screwed or bolted connections caused by vibrations , temperature cycling, and/or pressure cycling that can have mechanical and thermal impact . Consequently, i f screws or bolts are used the described arrangement of the semiconductor power unit can contribute to prevent the screws or bolts to get loose over time , which could result in a leakage of the cooling liquid in an open cooler setup . In a severe case , a replacement of the complete inverter could be necessary .
  • the baseplate of the power module and/or the housing of the cooler unit and/or the coupling element can comprise a coating that partially or completely covers the respective component .
  • a coating can comprise nickel and covers a lower part of the baseplate and/or an interior of the cooler housing that comes into contact with a coolant during operation of the power module and the semiconductor power unit .
  • the nickel coating can be configured to protect the baseplate from corrosion due to its contact to the coolant during operation .
  • the nickel coating can be used for other purposes as well .
  • a respective coating comprising silver and/or gold configured to provide predetermined coupling properties for coupling adj acent components .
  • a coating can be prepared from other materials suitable to provide protection and/or improved welding and connection properties and may be formed electroless or by means of a galvanic process or other applicable processes .
  • the baseplate of the power module can further comprise an underside with a given surface structure facing a flow channel inside the cooler unit and getting in contact with the coolant .
  • a lower part of the baseplate may be formed with a given cooling structure to provide an extensive heat exchange surface between the power module and the coolant .
  • a shape and/or orientation of the given surface structure can be configured to provide laminar flow or preferably turbulent flow of the coolant in part at least .
  • the surface structure can therefore be designed to beneficially influence the streaming behavior of a flowing coolant . In this respect pressure drop and flow rate of the coolant can also be taken into account in view of forming the given surface structure .
  • the surface structure at the bottom of the baseplate can comprise one or more protrusions , for example reali zed by a pin- fin area using pins having cylindrical or conical shape to increase the overall thermal ef ficiency provided with the increased surface area to ef fectively trans fer heat to the coolant .
  • the surface structure can comprise ribs and/or a skived structure and/or meander channels .
  • the lower part of the baseplate can be formed without a speci fic structure on its underside and thus may comprise a flat surface .
  • cooling structures such as pins , ribs , or skived fins can be incorporated in a heatsink to which a flat lower part of the baseplate can be attached .
  • the housing of the power module can be reali zed as a molded body forming an encapsulation with electronics inside that is coupled to the baseplate .
  • the housing can also comprise a frame that is filled with a given resin or gel .
  • the housing can reali ze an upper part of the power module and consequently the baseplate can reali ze a lower part of the power module .
  • the electronics may include power semiconductor devices , integrated circuits , bare or packaged chips , e . g . controllers in an intelligent power module , and/or discrete devices . Chips or other devices are typically mounted, e . g . to an isolating substrate , an insulated metal substrate , a PCB, or a leadframe .
  • an insulating substrate with an electrically isolating ceramic sheet is mounted on the baseplate or according to an alternative setup, an insulated metal substrate incorporates the baseplate as a lower part .
  • a backside or underside of the baseplate can be exposed for mounting and/or cooling purposes .
  • side portions of the baseplate can be exposed from the unit body for mounting, clamping and/or welding the power module to the housing of the cooler unit .
  • the housing of the cooler unit can be made of one piece or several pieces and comprises an internal flow channel to guide a coolant .
  • the housing comprises an inlet and an outlet defining a flow direction of the coolant during operation .
  • the housing further comprises one or more recesses configured to accommodate respective power modules .
  • the cooler unit comprises three recesses or one elongates recess to receive three power modules in a row with respect to the streaming direction of the flowing coolant .
  • the one or more recesses are configured in coordination with the associated baseplate or power module geometrically, and the power modules each are arranged inside and/or above the respective associated recess and each are welded to the housing of the cooler, possibly by means of a coupling element such as a screwed or bolted clamp or alternatively directly welded without a coupling element .
  • the semiconductor power unit comprises a sealing element for sealing a contact area between the power module and the cooler unit .
  • the sealing element is arranged inside a sealing recess , for example configured in the cooler housing, and contacts an upper surface of the housing on the one hand and a lower surface of the baseplate on the other hand .
  • the sealing element is arranged preferably inside the welding j oint or closer to the flow channel than the formed welding j oint .
  • the welding j oint forms a secure fixation of the power module to the cooler, possibly in interaction with a coupling element , and the sealing element securely seals the semiconductor power unit against unwanted leakage of the coolant .
  • the sealing element and the corresponding sealing recess can completely surround the respective recess for the power module .
  • the sealing element can be located inside a perimeter formed by welding j oints .
  • the sealing recess may be formed on the cooler housing and/or on a backside or bottom of the baseplate .
  • a method for manufacturing an embodiment of the described semiconductor power unit comprises providing at least one power module with a baseplate and a housing, and providing a cooler unit for cooling the at least one power module during operation .
  • the method further comprises coupling the at least one power module to a housing of the cooler unit by means of welding such that one or more welding j oints are formed between at least two of the housing of the cooler unit , the at least one power module and a coupling element for fixing the at least one power module to the housing of the cooler unit .
  • the step of coupling the at least one power module to a housing of the cooler unit by means of welding comprises forming the one or more welding j oints by means of at least one of resistance welding, arc welding and laser welding .
  • the step of coupling the at least one power module to a housing of the cooler unit by means of welding can further comprise pressing the at least one power module and the housing of the cooler unit together, and forming the one or more welding j oints directly between an upper surface of the housing of the cooler unit and a lower surface of the baseplate of the power module .
  • the method can comprise providing the coupling element with at least a clamp for fixing the at least one power module to the housing of the cooler unit , and pressing the clamp onto the at least one power module and thereby pressing the at least one power module and the housing of the cooler unit together .
  • the method can then further comprise forming the one or more welding j oints between the housing of the cooler unit , the at least one power module and/or the clamp .
  • the method comprises providing the coupling element with at least one of a screw and a bolt , and fixing the clamp onto the at least one power module and onto the housing of the cooler unit by means of attaching the screw and/or the bolt .
  • the method then further comprises forming the one or more welding j oints between the housing of the cooler unit , the at least one power module and/or the screw and/or the bolt .
  • the described semiconductor power unit can be manufactured using resistance or arc welding, especially stud arc welding, for example .
  • the welding process is done by a manipulation of a top side of the element to be j oined to the cooler housing using a corresponding welding tool .
  • a holding device can be used to hold the j oin partners in place and to exert a given pressure i f needed on one or both j oin partners .
  • Welding of bolts or screws to the metal baseplate of the power module contributes to secure the screws by an additional welding step .
  • Corresponding bolts or screws used for stud arc welding can comprise protrusions on a front tip or on a head for the support of the welding process by improved initiation of an electrical arc .
  • the fixation means can be secured and a loosening of screws or bolts can be prevented by the additional welding step by local welding spots , for example .
  • the welding process can be applied between a tip of the screw and the cooler housing inside a thread hole or between a screw head and a top surface of a clamp using protrusions on a screw tip or screw head, respectively, by means of stud arc welding .
  • the described arrangement can reduce the risk of loosening the screws , but thread holes still consuming space in the cooler structure .
  • an alternative approach refers to an arrangement without the need of screws or bolts , so that a positive impact on a cooling ef ficiency of the cooler can be achieved .
  • there can still be clamps used to hold one or more power modules in place but without screws or bolts .
  • the clamps are attached to the cooler housing surface , for example by a holding device such as a stamp element .
  • the clamps can be directly welded to the cooler housing surface .
  • a bottom surface of a clamp can have one or more protrusions to facilitate or improve an arc welding process . Alternatively or additionally, such protrusions may be also available on the bottom side of the baseplate at the welding location .
  • a further alternative arrangement can be reali zed even without a clamp and other coupling elements .
  • a direct welding of local portions of the power module baseplate to the cooler housing surface can be formed .
  • a corresponding welding process can be applied especially on one or more open baseplate portions in a peripheral regions of the associated power module .
  • the described semiconductor power unit can be related to the sector of E-mobility, but it can be applied to all kinds of power semiconductor modules with baseplates , which are mounted on a housing of a cooler .
  • FIG. 1-4 embodiments of a semiconductor power unit in di f ferent views ;
  • Figure 15 a flow chart for a method for manufacturing an embodiment of the semiconductor power unit .
  • Figure 1 illustrates a perspective view of an embodiment of a semiconductor power unit 1 with a cooler unit 2 and three power modules 10 in a row .
  • the three power modules 10 can also be referred to as a power package . Possible configurations and attachments of the respective power modules 10 are illustrated in the Figs . 2- 14 .
  • the cooler unit 2 is configured for liquid cooling of the power modules 10 ( see also Figs . 2-7 ) .
  • the cooler unit 2 comprises three recesses 22 corresponding to the three power modules 10 ( see also Fig . 3 ) .
  • a respective bottom side of the power modules 10 is arranged to face or extend into the associated recess 22 .
  • the cooler unit 1 further comprises a housing 8 that provides an internal flow channel 6 for a coolant .
  • the housing 8 further comprises an inlet 3 and an outlet 4 for the coolant so that during operation the coolant can flow through the housing 8 .
  • the three recesses 22 penetrate a wall of the housing 8 up to the flow channel 6 in order to receive the respective power modules 10 .
  • the housing 8 can be assembled from two parts , for example . Alternatively, the housing 8 can be made in one piece . According to the illustrated embodiment the inlet 3 and the outlet 4 belong to a lower part of the housing 8 .
  • the recesses 22 are configured in coordination with the power modules 10 geometrically .
  • the power modules 10 of the semiconductor power unit 1 each comprise a respective baseplate 12 and a housing 18 which can be formed as a molded body reali zing an encapsulation for respective electronics inside ( see Fig . 2 ) .
  • the baseplate 12 may be formed as an insulated metal substrate consisting of a metal plate , an isolating resin layer, and circuit metalli zation .
  • the power modules 10 comprise several terminals 19 that reali ze electrical interfaces such as main and auxiliary terminals .
  • the power modules 10 or their respective baseplates 12 are coupled to the housing 8 of the cooler unit 2 by means of welding such that one or more welding j oints 15 are formed between the housing 8 of the cooler unit , the power modules 10 and/or a coupling element for fixing the respective power modules 10 to the housing 8 .
  • the semiconductor power unit 1 can but does not have to comprise an additional coupling element ( see Figs . 1- 14 ) .
  • the semiconductor power unit 1 comprises an additional coupling element this can include a clamp 11 and/or a screw 16 and/or a bolt 17 for fixing the respective power modules 10 to the housing 8 of the cooler unit 2 .
  • the one or more welding j oints 15 can be formed directly between an upper surface 21 of the housing 8 of the cooler unit 2 and a lower surface 121 of the baseplate 12 of the power module 10 ( see Figs . 9- 14 ) .
  • the one or more welding j oints 15 can be formed directly between an upper surface 21 of the housing 8 of the cooler unit 2 and a lower surface 111 of the clamp 11 ( see Fig . 8 ) and/or an outer surface of the respective screw 16 or bolt 17 ( see Figs . 5-7 ) .
  • the one or more welding j oints 15 can be formed by means of resistance welding, arc welding and/or laser welding, for example.
  • the one or both join partners can comprise respective recesses 112 or 122 (see Figs. 8 or 11-14) .
  • the recess 112 belongs to the clamp 11 and realizes a thinned portion of the clamp 11 that forms a prepared coupling area 5 as a region intended for the welding process (see Fig. 8) .
  • the recess 122 belongs to the respective baseplate 12 and realizes a thinned portion of an exposed part 14 of the baseplate 12 such that the coupling area 5 is prepared for the welding process (see Figs. 11-14) .
  • the power modules 10 are mounted to the openings or recesses 22 of the cooler unit 2 for liquid cooling by clamps 11, which are fixed to the cooler housing 8 by screws 16.
  • Sealing elements 7 are arranged inside a corresponding sealing recess 71 between the upper surface 21 of the cooler unit 2 and the lower surface 121 of the baseplates 12 of the power modules 10.
  • a respective sealing recess can be formed on a backside or bottom side of the baseplate 12.
  • both recesses may correspond to each other to receive one common sealing element 7.
  • two or more laterally separated sealing recesses can be formed.
  • the clamps 11 expose force to the exposed baseplate portions 14 in peripheral regions of the power modules 10 (see also Fig.
  • the baseplates 12 may comprise cooling structures at their bottom surfaces, e.g. in form of pin-fin areas extending into the flow channel 6 of the cooler unit 2 ( see Figs . 1 , 3 and 4 ) .
  • Figure 5 shows an embodiment of the semiconductor power unit 1 with screwed clamps 11 and welded screws 16 at their respective head .
  • the clamp 11 and/or the baseplate 12 itsel f and/or the housing 8 can comprise recesses 51 forming screw holes to directly or indirectly fix the power module 10 to the cooler housing 8 by screws 16 .
  • the fixation can be formed by bolts 17 .
  • I f screws 16 are used the corresponding coupling recesses 51 inside the baseplate 12
  • the clamp 11 and/or the housing 8 comprises a thread interacting with the screw 16 , which is inserted into thread recess 51 .
  • the screw 16 is secured against loosening by welding of the bottom surface of the screw head on a top surface of the clamp 11 or the baseplate 12 , for example .
  • An arc welding process can be supported by one or more protrusions on a surface of the screw head in the vicinity of the clamp 11 or baseplate 12 .
  • laser welding generating a local welding spot 15 on the screw head might also be considered as a j oining method .
  • a fixation by welding may be also available inside the penetrating recess 51 of a baseplate or the clamp 11 .
  • a welding connection can be formed at edges of a penetrating recess next to the j oining partner, i f laser welding is used, for example .
  • the screw 16 can be welded to the housing 8 of the cooler unit 2 at its tip as illustrated in Figure 6 .
  • the fixation of the clamp 11 and/or baseplate 12 is done by screws 16 and the respective screw 16 is secured against loosening by a welded connection between the screw tip or lower end of the screw 16 and a bottom surface of the thread hole forming the coupling recess 51 .
  • stud arc welding is typically facilitated or supported by a small protruding pin on the end of the screw 16 forming a screw protrusion 161 intended for welding .
  • Such a protrusion 161 can preset melted to form a corresponding welding j oint 15 .
  • the protrusion 161 is used for creation of high electric field and consequently to support an ignition of an electric arc .
  • Figure 7 shows an alternative embodiment to couple the power module 10 to the cooler unit 2 in terms of material fit connections .
  • the clamp 11 is used for mounting of the power module 10 and is fixed to the cooler unit upper surface 21 by bolts 17 instead of screws .
  • a welded connection is prepared between a bottom surface of the respective bolts 17 and the upper surface 21 of the cooler housing forming the coupling area 5 .
  • An improvement of the welding process may be achieved by a recess in the bolt 17 (not shown) on the location of the welded connection to reduce the needed thermal impact by a locally smaller metal thickness .
  • the bolts 17 may comprise a respective protrusion 171 at their tips to facilitate or improve the welding process .
  • it can be considered to directly fix the baseplate 12 to the cooler housing 8 by bolts without a clamp 11 for fixation .
  • Figure 8 shows a further embodiment to couple the power module 10 to the cooler unit 2 in terms of material fit connections .
  • the welding j oints 15 are directly prepared between a portion of the lower surface 111 of the clamp 11 and the upper surface 21 of the housing 8 of the cooler unit 2 without the need of screws or bolts .
  • An improvement of the welding process and of the welding quality may be on one hand achieved by one or more recesses 112 in the clamp 11 on the location of the welded connection to reduce the needed thermal impact by a locally smaller metal thickness and consequently by a smaller amount of material to be molten
  • a backside of the clamp 11 may have one or more protrusions to facilitate or improve the arc welding process .
  • the upper surface 21 of the cooler housing 8 may have one or more protrusions .
  • thread holes forming the recesses 51 for screws 16 or bolts 17 in the cooler housing 8 cause a loss of space in the cooling structure and can reduce locally a width of the cooling flow channel 6 and consequently a cooling ef ficiency by narrowing and/or partly blocking the coolant flow ( see Fig . 4 ) .
  • FIGS. 9- 14 show further alternative embodiments to couple the power module 10 to the cooler unit 2 in terms of material fit connections without the need for screws or bolts and corresponding coupling recesses . Even clamps for fixation are not needed .
  • the power modules 10 are directly welded to the cooler unit 2 by welded connections between exposed portions 14 of their respective baseplates 12 and the upper surface 21 .
  • the respective power module 10 has each two exposed baseplate parts 14 in two opposite peripheral regions , which are normally used for fixation by clamps .
  • These exposed parts can be used for forming the welding j oints 15 prepared especially by resistance or arc welding .
  • laser welding is possible , especially i f recesses 112 , 122 are available . I f such recesses 112 , 122 are large enough, the one or more welding j oints 15 can be formed by means of ultrasonic welding .
  • an improvement of the welding process may be on one hand achieved by a recess in the baseplate 12 on the location of the welded connection forming the coupling area 5 to reduce the needed thermal impact by a locally smaller metal thickness .
  • a backside or bottom surface of the exposed baseplate part 14 may have one or more protrusions to facilitate or improve the arc welding process .
  • several welded connections using several recessed portions 122 may be considered ( see Figs . 13 and 14 ) .
  • the Figs . 9- 14 show di f ferent variants for welding of an exposed part 14 of the baseplate 12 with and without recesses 122 to the upper surface 21 of the cooler unit 2 .
  • Steps of a corresponding manufacturing method to form the semiconductor power unit 1 can follow the flow chart as shown in Figure 15 .
  • the one or more power modules 10 are provided with the baseplate 12 and the housing 18 .
  • the cooler unit 2 is provided for cooling the power modules 10 during operation .
  • step S3 the power modules 10 are attached or located to the housing 8 of the cooler unit 2 in the corresponding recesses 22 provided for this .
  • a step S4 the power modules 10 and the housing 8 of the cooler unit 2 are coupled together by means of welding such that one or more welding j oints 15 are formed between the housing 8 of the cooler unit 2 , the power modules 10 and/or, i f present , the coupling element in form of the clamp 11 , the screw 16 and/or the bolt 17 .

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Abstract

A semiconductor power unit (1) comprises at least one power module (10) with a baseplate (12) and a housing (18). The semiconductor power unit (1) further comprises a cooler unit (2) for cooling the at least one power module (10) during operation. The at least one power module (10) is coupled to a housing (8) of the cooler unit (2) by means of welding such that one or more welding joints (15) are formed between at least two of the housing (8) of the cooler unit (2), the at least one power module (10) and a coupling element (11, 16, 17) for fixing the at least one power module (10) to the housing (8) of the cooler unit (2).

Description

Description
SEMICONDUCTOR POWER UNIT AND METHOD FOR MANUFACTURING A SEMICONDUCTOR POWER UNIT
The present disclosure is related to a semiconductor power unit and a method for manufacturing a semiconductor power unit .
Power modules are used in automotive inverters for example and require a cooler to dissipate heat during operation . To enable a stable and secure set up of such power units the power modules are fixed to the cooler by means of screws or screwed clamps .
There is a need to provide a semiconductor power unit that enables a secure and stable coupling between a power module and a cooler for liquid cooling and that contributes to reliable and ef fective heat dissipation during operation of the power module .
Embodiments of the disclosure relate to a semiconductor power unit which enable stable and secure coupling and which contribute to reliable heat dissipation . Embodiments of the disclosure also relate to a corresponding manufacturing method for such a semiconductor power unit .
According to an embodiment , a semiconductor power unit comprises at least one power module with a baseplate and a housing, and a cooler unit for cooling the at least one power module during operation . The at least one power module is coupled to a housing of the cooler unit by means of welding such that one or more welding j oints are formed between at least two of the housing of the cooler unit , the at least one power module and a coupling element for fixing the at least one power module to the housing of the cooler unit .
By use of the described configuration a semiconductor power unit is feasible that enables a secure and stable coupling between a power module and a cooler unit for liquid cooling and that further contributes to reliable heat dissipation during operation of the power module . Inter alia, the semiconductor power unit is suitable for power modules for use in high voltage applications , for example for a voltage of at least 0 . 5 kV .
The welding j oint between the housing of the cooler unit , the at least one power module and/or the coupling element can be formed by means of resistance welding and/or arc welding and/or laser welding . There can be multiple separated welding spots each forming a respective welding j oint . There can also be one elongated welding j oint , for example nearly an entire side length of the power module . In order to contribute to a reliable and secure coupling, there is at least each one welding j oint formed on opposite sides of the power module to securely fix it to the cooler . Consequently, there are two or more welding j oints formed preferably . According to an embodiment , the power module has a substantially rectangular or cuboid form and there can be four welding j oints formed in a vicinity of a respective edge of the cuboid power module , for example . The welding can be done on several locations of each two opposite sides of the power module .
The housing of the cooler unit can comprise aluminum . In this respect , the housing can be made of aluminum entirely or in sections , wherein the housing can comprise aluminum in form of bare aluminum and/or aluminum alloy . Alternatively or additionally, the housing can comprise copper and/or a copper alloy . The housing can be made of or comprise any weldable material .
The baseplate can comprise aluminum or copper . In this respect , the baseplate can be made of aluminum or copper entirely or in sections , wherein the baseplate can comprise aluminum or copper in form of bare aluminum or copper and/or aluminum alloy or copper . The baseplate of the power module can be made of or comprise any weldable material . For example , the baseplate can be made of a composite material like AlSiC or MgSiC at least in case of clamping, when the baseplate is not directly welded to the cooler . For example , the housing of the cooler unit and the baseplate comprise the same material or material composition . The aforementioned material options can also apply to the coupling element that can comprise any weldable material i f it is intended for welding . For example , a clamp, a screw and/or a bolt are also made of the aforementioned materials or compositions . Alternatively, a clamp, a screw and/or a bolt are made of steel . Alternatively, a material made of Zinc or Al-Zn alloy can be used for the baseplate , the housing, a clamp, a screw and/or a bolt .
According to an embodiment of the semiconductor power unit , the one or more welding j oints are formed directly between an upper surface of the housing of the cooler unit and a lower surface of the baseplate of the power module . Accordingly, the semiconductor power unit can be assembled without any further coupling element and the power module and the cooler unit can be connected by means of welding . The upper surface of the housing reali zes the surface that is facing away from the opposite bottom such that the upper surface not merely describes one or more uppermost portions of the housing but also the upper surface inside a bottom of a recess that is formed at the upper surface of the housing, for example . In order to contribute to beneficial welding conditions , the baseplate of the power module can comprise one or more recesses at the respective position of the one or more welding j oints . So the thermal impact needed for welding is reduced due to the thinned portion related to a smaller amount of material to be molten of the baseplate or clamp .
According to a further embodiment , the semiconductor power unit comprises a coupling element , for example including a clamp, a screw and/or a bolt for fixing the at least one power module to the housing of the cooler unit . For example , the power module is connected to the cooler unit using a screwed clamp and afterwards the connection is reliably secured by means of welding and the formed one or more welding j oints . Alternatively, the coupling element can be reali zed j ust as a clamp holding the power module in place relatively to the cooler unit . The one or more welding j oints can be formed directly between an upper surface of the housing of the cooler unit and a lower surface of the clamp . Additionally, in order to beneficially af fect the welding process the clamp can comprise one or more recesses at the respective position of the one or more welding j oints .
I f the coupling element additionally comprises a screw and/or a bolt used for fixing the power module to the cooler unit , the clamp comprises one or more recesses at the respective position of the one or more screws and/or bolts are to be inserted . The clamp can comprise a penetrating recess in which the screw or the bolt is arranged . The one or more welding j oints then can be formed between the screw or the bolt and the upper surface of the housing of the cooler unit , inside the penetrating recess of the clamp and/or an upper surface of the clamp facing away from the cooler unit . The screw or bolt can be fixed at a respective screw or bolt head to fix their preassembled holding position . The welding connection can be formed between the screw head and the top surface of the clamp . Moreover, it is possible to directly screw the baseplate to the cooler and the one or more screws are secured by welding by the same methods as described above . According to such an embodiment , the baseplate is configured to receive the screws and comprises corresponding openings .
According to a further embodiment , the housing of the cooler unit can comprise one or more recesses in coordination with the one or more penetrating recesses of one or more clamps such that a respective screw or the bolt extends through a penetrating recess of a respective clamp into the associated recess of the housing of the cooler unit . The one or more welding j oints can then be formed between the screw or the bolt and the housing of the cooler unit inside the recess of the housing of the cooler unit .
According to a further embodiment of the semiconductor power unit , the screw and/or the bolt comprises a respective welding protrusion configured for welding and facing the housing of the cooler unit such that the corresponding welding j oint is formed by melting the welding protrusion . Such a protrusion is also used to support an ignition of an electric arc in case of arc or resistance welding . Also a screw or bolt head may have such a protrusion, which face the top surface of the clamp or of the baseplate , i f the baseplate is directly screwed to the cooler . During a welding process the protrusion and a portion of the screw or bolt is molten, respectively .
It is a recognition in connection with the present disclosure that conventional power modules may be mechanically fixed to power units using a clamping and screwing mechanism or direct screwing of the baseplate . Such a conventional configuration including screwed clamps there is a risk of that threaded connections may result in loss of torque and consequently in loss of reliability due to thermal cycling or due to vibrations and thus in the risk of loss of coolant due to leakage in long-term operation .
Due to the described structure of the semiconductor power unit and its secured welding connection, the aforementioned adverse ef fects can be counteracted . The use of the described fixation method of the power modules on the cooler unit can counteract a loosening of screwed or bolted connections caused by vibrations , temperature cycling, and/or pressure cycling that can have mechanical and thermal impact . Consequently, i f screws or bolts are used the described arrangement of the semiconductor power unit can contribute to prevent the screws or bolts to get loose over time , which could result in a leakage of the cooling liquid in an open cooler setup . In a severe case , a replacement of the complete inverter could be necessary .
Furthermore , i f no screws or bolts are used in the described arrangement of the semiconductor power unit there is no need for bolt holes or thread holes for screws in the cooler structure . Therefore , according to such embodiments a loss of space in the cooling structure , especially inside a coolant channel , can be avoided, which would be used for receiving the screws or bolts and which may reduce an ef ficiency of the cooler due to partly narrowing and/or blocking a coolant flow, and increase the total weight due to additional material needed for the thread or bolt placement .
According to a further embodiment , the baseplate of the power module and/or the housing of the cooler unit and/or the coupling element can comprise a coating that partially or completely covers the respective component . For instances , such a coating can comprise nickel and covers a lower part of the baseplate and/or an interior of the cooler housing that comes into contact with a coolant during operation of the power module and the semiconductor power unit . The nickel coating can be configured to protect the baseplate from corrosion due to its contact to the coolant during operation . However, the nickel coating can be used for other purposes as well .
Alternatively or additionally, there can be a respective coating comprising silver and/or gold configured to provide predetermined coupling properties for coupling adj acent components . Alternatively or additionally, there can be formed a coating in the area where the one or more welding j oint are to be made to improve the formation of the respective welding j oint and thus the coupling of the power module to the housing of the cooler unit . Besides the aforementioned possibilities of nickel , silver and/or gold, a coating can be prepared from other materials suitable to provide protection and/or improved welding and connection properties and may be formed electroless or by means of a galvanic process or other applicable processes . The baseplate of the power module can further comprise an underside with a given surface structure facing a flow channel inside the cooler unit and getting in contact with the coolant . Thus , a lower part of the baseplate may be formed with a given cooling structure to provide an extensive heat exchange surface between the power module and the coolant . A shape and/or orientation of the given surface structure can be configured to provide laminar flow or preferably turbulent flow of the coolant in part at least . The surface structure can therefore be designed to beneficially influence the streaming behavior of a flowing coolant . In this respect pressure drop and flow rate of the coolant can also be taken into account in view of forming the given surface structure .
The surface structure at the bottom of the baseplate can comprise one or more protrusions , for example reali zed by a pin- fin area using pins having cylindrical or conical shape to increase the overall thermal ef ficiency provided with the increased surface area to ef fectively trans fer heat to the coolant . Additionally or alternatively, the surface structure can comprise ribs and/or a skived structure and/or meander channels . Alternatively, the lower part of the baseplate can be formed without a speci fic structure on its underside and thus may comprise a flat surface . Alternatively or additionally, cooling structures such as pins , ribs , or skived fins can be incorporated in a heatsink to which a flat lower part of the baseplate can be attached .
The housing of the power module can be reali zed as a molded body forming an encapsulation with electronics inside that is coupled to the baseplate . The housing can also comprise a frame that is filled with a given resin or gel . The housing can reali ze an upper part of the power module and consequently the baseplate can reali ze a lower part of the power module . The electronics may include power semiconductor devices , integrated circuits , bare or packaged chips , e . g . controllers in an intelligent power module , and/or discrete devices . Chips or other devices are typically mounted, e . g . to an isolating substrate , an insulated metal substrate , a PCB, or a leadframe . For example , an insulating substrate with an electrically isolating ceramic sheet is mounted on the baseplate or according to an alternative setup, an insulated metal substrate incorporates the baseplate as a lower part . A backside or underside of the baseplate can be exposed for mounting and/or cooling purposes . Moreover, side portions of the baseplate can be exposed from the unit body for mounting, clamping and/or welding the power module to the housing of the cooler unit .
The housing of the cooler unit can be made of one piece or several pieces and comprises an internal flow channel to guide a coolant . The housing comprises an inlet and an outlet defining a flow direction of the coolant during operation . The housing further comprises one or more recesses configured to accommodate respective power modules . For example , the cooler unit comprises three recesses or one elongates recess to receive three power modules in a row with respect to the streaming direction of the flowing coolant . The one or more recesses are configured in coordination with the associated baseplate or power module geometrically, and the power modules each are arranged inside and/or above the respective associated recess and each are welded to the housing of the cooler, possibly by means of a coupling element such as a screwed or bolted clamp or alternatively directly welded without a coupling element . According to a further embodiment , the semiconductor power unit comprises a sealing element for sealing a contact area between the power module and the cooler unit . The sealing element is arranged inside a sealing recess , for example configured in the cooler housing, and contacts an upper surface of the housing on the one hand and a lower surface of the baseplate on the other hand . The sealing element is arranged preferably inside the welding j oint or closer to the flow channel than the formed welding j oint . Thus , the welding j oint forms a secure fixation of the power module to the cooler, possibly in interaction with a coupling element , and the sealing element securely seals the semiconductor power unit against unwanted leakage of the coolant . The sealing element and the corresponding sealing recess can completely surround the respective recess for the power module . The sealing element can be located inside a perimeter formed by welding j oints . The sealing recess may be formed on the cooler housing and/or on a backside or bottom of the baseplate .
According to an embodiment , a method for manufacturing an embodiment of the described semiconductor power unit comprises providing at least one power module with a baseplate and a housing, and providing a cooler unit for cooling the at least one power module during operation . The method further comprises coupling the at least one power module to a housing of the cooler unit by means of welding such that one or more welding j oints are formed between at least two of the housing of the cooler unit , the at least one power module and a coupling element for fixing the at least one power module to the housing of the cooler unit . As a result of that the described method is configured in particular to manufacture an embodiment of the described semiconductor power unit , described features and characteristics of the semiconductor power unit are also disclosed with respect to the manufacturing method and vice versa .
According to an embodiment of the method, the step of coupling the at least one power module to a housing of the cooler unit by means of welding comprises forming the one or more welding j oints by means of at least one of resistance welding, arc welding and laser welding .
The step of coupling the at least one power module to a housing of the cooler unit by means of welding can further comprise pressing the at least one power module and the housing of the cooler unit together, and forming the one or more welding j oints directly between an upper surface of the housing of the cooler unit and a lower surface of the baseplate of the power module .
Alternatively or additionally, the method can comprise providing the coupling element with at least a clamp for fixing the at least one power module to the housing of the cooler unit , and pressing the clamp onto the at least one power module and thereby pressing the at least one power module and the housing of the cooler unit together . The method can then further comprise forming the one or more welding j oints between the housing of the cooler unit , the at least one power module and/or the clamp .
According to a further embodiment , the method comprises providing the coupling element with at least one of a screw and a bolt , and fixing the clamp onto the at least one power module and onto the housing of the cooler unit by means of attaching the screw and/or the bolt . The method then further comprises forming the one or more welding j oints between the housing of the cooler unit , the at least one power module and/or the screw and/or the bolt .
The described semiconductor power unit can be manufactured using resistance or arc welding, especially stud arc welding, for example . The welding process is done by a manipulation of a top side of the element to be j oined to the cooler housing using a corresponding welding tool . Additionally, a holding device can be used to hold the j oin partners in place and to exert a given pressure i f needed on one or both j oin partners . Welding of bolts or screws to the metal baseplate of the power module , for example by stud arc welding, contributes to secure the screws by an additional welding step . Corresponding bolts or screws used for stud arc welding can comprise protrusions on a front tip or on a head for the support of the welding process by improved initiation of an electrical arc .
Due to the aforementioned setup, where power modules are fixed to the cooler by screwed or bolted clamps , the fixation means can be secured and a loosening of screws or bolts can be prevented by the additional welding step by local welding spots , for example . The welding process can be applied between a tip of the screw and the cooler housing inside a thread hole or between a screw head and a top surface of a clamp using protrusions on a screw tip or screw head, respectively, by means of stud arc welding . As a result , the described arrangement can reduce the risk of loosening the screws , but thread holes still consuming space in the cooler structure .
Accordingly, an alternative approach refers to an arrangement without the need of screws or bolts , so that a positive impact on a cooling ef ficiency of the cooler can be achieved . For example , there can still be clamps used to hold one or more power modules in place , but without screws or bolts . On one hand, the clamps are attached to the cooler housing surface , for example by a holding device such as a stamp element . The clamps can be directly welded to the cooler housing surface . A bottom surface of a clamp can have one or more protrusions to facilitate or improve an arc welding process . Alternatively or additionally, such protrusions may be also available on the bottom side of the baseplate at the welding location .
A further alternative arrangement can be reali zed even without a clamp and other coupling elements . A direct welding of local portions of the power module baseplate to the cooler housing surface can be formed . A corresponding welding process can be applied especially on one or more open baseplate portions in a peripheral regions of the associated power module .
The described embodiments of the semiconductor power unit enable one or more of the following benefits due to the j oined connection by welding :
• better securing of the mounting of the power module on the cooler is achievable . A possible leakage of the cooling liquid due to loosening of screws on customer site e . g . by vibrations is prevented or a risk is reduced signi ficantly . • design freedom for the cooler and possibly the cooling ef ficiency can be improved due to no demand of space for thread holes for screws or bolts in the cooler housing, which is at least partly blocking the coolant flow . Related to this , the cooler weight can be reduced by using the extra space for the cooling circuit .
• cost reduction and reduced bill-of-materials can be enabled because there is no need for screws and/or clamps depending on the selected configuration .
The described semiconductor power unit can be related to the sector of E-mobility, but it can be applied to all kinds of power semiconductor modules with baseplates , which are mounted on a housing of a cooler .
Exemplary embodiments are explained in the following with the aid of schematic drawings and reference numbers . The figures show :
Figures 1-4 embodiments of a semiconductor power unit in di f ferent views ;
Figures 5- 14 embodiments of manufacturing the semiconductor power unit in a di f ferent views ; and
Figure 15 a flow chart for a method for manufacturing an embodiment of the semiconductor power unit .
The accompanying figures are included to provide a further understanding . It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale . Identical reference numbers designate elements or components with identical functions . In so far as elements or components correspond to one another in terms of their function in the figures , the description thereof is not repeated for each of the following figures . For the sake of clarity elements might not appear with corresponding reference symbols in all figures possibly .
Figure 1 illustrates a perspective view of an embodiment of a semiconductor power unit 1 with a cooler unit 2 and three power modules 10 in a row . The three power modules 10 can also be referred to as a power package . Possible configurations and attachments of the respective power modules 10 are illustrated in the Figs . 2- 14 . The cooler unit 2 is configured for liquid cooling of the power modules 10 ( see also Figs . 2-7 ) . The cooler unit 2 comprises three recesses 22 corresponding to the three power modules 10 ( see also Fig . 3 ) . A respective bottom side of the power modules 10 is arranged to face or extend into the associated recess 22 .
The cooler unit 1 further comprises a housing 8 that provides an internal flow channel 6 for a coolant . The housing 8 further comprises an inlet 3 and an outlet 4 for the coolant so that during operation the coolant can flow through the housing 8 . The three recesses 22 penetrate a wall of the housing 8 up to the flow channel 6 in order to receive the respective power modules 10 . The housing 8 can be assembled from two parts , for example . Alternatively, the housing 8 can be made in one piece . According to the illustrated embodiment the inlet 3 and the outlet 4 belong to a lower part of the housing 8 . The recesses 22 are configured in coordination with the power modules 10 geometrically . The power modules 10 of the semiconductor power unit 1 each comprise a respective baseplate 12 and a housing 18 which can be formed as a molded body reali zing an encapsulation for respective electronics inside ( see Fig . 2 ) . The baseplate 12 may be formed as an insulated metal substrate consisting of a metal plate , an isolating resin layer, and circuit metalli zation . Moreover, the power modules 10 comprise several terminals 19 that reali ze electrical interfaces such as main and auxiliary terminals .
The power modules 10 or their respective baseplates 12 are coupled to the housing 8 of the cooler unit 2 by means of welding such that one or more welding j oints 15 are formed between the housing 8 of the cooler unit , the power modules 10 and/or a coupling element for fixing the respective power modules 10 to the housing 8 . Thus , the semiconductor power unit 1 can but does not have to comprise an additional coupling element ( see Figs . 1- 14 ) . I f the semiconductor power unit 1 comprises an additional coupling element this can include a clamp 11 and/or a screw 16 and/or a bolt 17 for fixing the respective power modules 10 to the housing 8 of the cooler unit 2 .
Accordingly, the one or more welding j oints 15 can be formed directly between an upper surface 21 of the housing 8 of the cooler unit 2 and a lower surface 121 of the baseplate 12 of the power module 10 ( see Figs . 9- 14 ) . Alternatively or additionally, in combination with an additional coupling element the one or more welding j oints 15 can be formed directly between an upper surface 21 of the housing 8 of the cooler unit 2 and a lower surface 111 of the clamp 11 ( see Fig . 8 ) and/or an outer surface of the respective screw 16 or bolt 17 ( see Figs . 5-7 ) . The one or more welding j oints 15 can be formed by means of resistance welding, arc welding and/or laser welding, for example.
In order to contribute to a beneficial welding process by a reduced needed thermal impact, the one or both join partners can comprise respective recesses 112 or 122 (see Figs. 8 or 11-14) . The recess 112 belongs to the clamp 11 and realizes a thinned portion of the clamp 11 that forms a prepared coupling area 5 as a region intended for the welding process (see Fig. 8) . The recess 122 belongs to the respective baseplate 12 and realizes a thinned portion of an exposed part 14 of the baseplate 12 such that the coupling area 5 is prepared for the welding process (see Figs. 11-14) .
According to Figure 1 and 3 the power modules 10 are mounted to the openings or recesses 22 of the cooler unit 2 for liquid cooling by clamps 11, which are fixed to the cooler housing 8 by screws 16. Sealing elements 7 are arranged inside a corresponding sealing recess 71 between the upper surface 21 of the cooler unit 2 and the lower surface 121 of the baseplates 12 of the power modules 10. Alternatively or additionally, a respective sealing recess can be formed on a backside or bottom side of the baseplate 12. In case of an additional sealing recess on a baseplate backside, both recesses may correspond to each other to receive one common sealing element 7. Also two or more laterally separated sealing recesses can be formed. The clamps 11 expose force to the exposed baseplate portions 14 in peripheral regions of the power modules 10 (see also Fig. 2) . In this respect, terms such as "upper", "lower", "top", "bottom", "side" are used to refer to positions and/or orientations as illustrated in the figures. The baseplates 12 may comprise cooling structures at their bottom surfaces, e.g. in form of pin-fin areas extending into the flow channel 6 of the cooler unit 2 ( see Figs . 1 , 3 and 4 ) .
Figure 5 shows an embodiment of the semiconductor power unit 1 with screwed clamps 11 and welded screws 16 at their respective head . The clamp 11 and/or the baseplate 12 itsel f and/or the housing 8 can comprise recesses 51 forming screw holes to directly or indirectly fix the power module 10 to the cooler housing 8 by screws 16 . Alternatively or additionally, the fixation can be formed by bolts 17 . I f screws 16 are used the corresponding coupling recesses 51 inside the baseplate 12 , the clamp 11 and/or the housing 8 comprises a thread interacting with the screw 16 , which is inserted into thread recess 51 . The screw 16 is secured against loosening by welding of the bottom surface of the screw head on a top surface of the clamp 11 or the baseplate 12 , for example . An arc welding process can be supported by one or more protrusions on a surface of the screw head in the vicinity of the clamp 11 or baseplate 12 . Alternatively or additionally, laser welding generating a local welding spot 15 on the screw head might also be considered as a j oining method . A fixation by welding may be also available inside the penetrating recess 51 of a baseplate or the clamp 11 . Alternatively or additionally, a welding connection can be formed at edges of a penetrating recess next to the j oining partner, i f laser welding is used, for example .
Alternatively or additionally, the screw 16 can be welded to the housing 8 of the cooler unit 2 at its tip as illustrated in Figure 6 . The fixation of the clamp 11 and/or baseplate 12 is done by screws 16 and the respective screw 16 is secured against loosening by a welded connection between the screw tip or lower end of the screw 16 and a bottom surface of the thread hole forming the coupling recess 51 . For instances , stud arc welding is typically facilitated or supported by a small protruding pin on the end of the screw 16 forming a screw protrusion 161 intended for welding . Such a protrusion 161 can preset melted to form a corresponding welding j oint 15 . The protrusion 161 is used for creation of high electric field and consequently to support an ignition of an electric arc .
Figure 7 shows an alternative embodiment to couple the power module 10 to the cooler unit 2 in terms of material fit connections . The clamp 11 is used for mounting of the power module 10 and is fixed to the cooler unit upper surface 21 by bolts 17 instead of screws . A welded connection is prepared between a bottom surface of the respective bolts 17 and the upper surface 21 of the cooler housing forming the coupling area 5 . An improvement of the welding process may be achieved by a recess in the bolt 17 (not shown) on the location of the welded connection to reduce the needed thermal impact by a locally smaller metal thickness . On the other hand, the bolts 17 may comprise a respective protrusion 171 at their tips to facilitate or improve the welding process . Alternatively, it can be considered to directly fix the baseplate 12 to the cooler housing 8 by bolts without a clamp 11 for fixation .
Figure 8 shows a further embodiment to couple the power module 10 to the cooler unit 2 in terms of material fit connections . The welding j oints 15 are directly prepared between a portion of the lower surface 111 of the clamp 11 and the upper surface 21 of the housing 8 of the cooler unit 2 without the need of screws or bolts . An improvement of the welding process and of the welding quality may be on one hand achieved by one or more recesses 112 in the clamp 11 on the location of the welded connection to reduce the needed thermal impact by a locally smaller metal thickness and consequently by a smaller amount of material to be molten On the other hand, a backside of the clamp 11 may have one or more protrusions to facilitate or improve the arc welding process . Alternatively or additionally, the upper surface 21 of the cooler housing 8 may have one or more protrusions .
Due to the described configurations using coupling elements in the form of clamps 11 , screws 16 and/or bolts 17 it is possible to securely fix the power modules 10 on the cooler unit 2 . This allows for reliable sealing of the semiconductor power unit 1 and counteracts loosening of screws 16 or bolts 17 due to vibrations , temperature cycling, and/or pressure cycling that have mechanical and thermal impact on the corresponding connections . Consequently, the described configurations counteract the risk of a leakage of the cooling liquid in a cooler setup . Besides , thread holes forming the recesses 51 for screws 16 or bolts 17 in the cooler housing 8 cause a loss of space in the cooling structure and can reduce locally a width of the cooling flow channel 6 and consequently a cooling ef ficiency by narrowing and/or partly blocking the coolant flow ( see Fig . 4 ) .
Consequently, the Figures 9- 14 show further alternative embodiments to couple the power module 10 to the cooler unit 2 in terms of material fit connections without the need for screws or bolts and corresponding coupling recesses . Even clamps for fixation are not needed . The power modules 10 are directly welded to the cooler unit 2 by welded connections between exposed portions 14 of their respective baseplates 12 and the upper surface 21 . For example , the respective power module 10 has each two exposed baseplate parts 14 in two opposite peripheral regions , which are normally used for fixation by clamps . These exposed parts can be used for forming the welding j oints 15 prepared especially by resistance or arc welding . Alternatively or additionally, also laser welding is possible , especially i f recesses 112 , 122 are available . I f such recesses 112 , 122 are large enough, the one or more welding j oints 15 can be formed by means of ultrasonic welding .
Similar to a welded connection between a clamp and the cooler unit 2 , an improvement of the welding process may be on one hand achieved by a recess in the baseplate 12 on the location of the welded connection forming the coupling area 5 to reduce the needed thermal impact by a locally smaller metal thickness . On the other hand, a backside or bottom surface of the exposed baseplate part 14 may have one or more protrusions to facilitate or improve the arc welding process . Also several welded connections using several recessed portions 122 may be considered ( see Figs . 13 and 14 ) . The Figs . 9- 14 show di f ferent variants for welding of an exposed part 14 of the baseplate 12 with and without recesses 122 to the upper surface 21 of the cooler unit 2 . Accordingly, due to the fact that there is no screw or bolt used in such configurations there is no need for corresponding coupling recesses 51 and thus the described configurations as shown in the Figures 9- 14 can contribute to an enhanced ef ficiency of the cooler unit 2 , and a reduced overall weight as e . g . additional material can be saved for the thread positions .
Steps of a corresponding manufacturing method to form the semiconductor power unit 1 can follow the flow chart as shown in Figure 15 . In a step S I the one or more power modules 10 are provided with the baseplate 12 and the housing 18 . In a step S2 the cooler unit 2 is provided for cooling the power modules 10 during operation .
In a step S3 the power modules 10 are attached or located to the housing 8 of the cooler unit 2 in the corresponding recesses 22 provided for this .
In a step S4 the power modules 10 and the housing 8 of the cooler unit 2 are coupled together by means of welding such that one or more welding j oints 15 are formed between the housing 8 of the cooler unit 2 , the power modules 10 and/or, i f present , the coupling element in form of the clamp 11 , the screw 16 and/or the bolt 17 .
Thus , a closed and securely sealed semiconductor power unit 1 is feasible .
The embodiments shown in or described by the figures 1 to 15 as stated represent exemplary embodiments of the improved semiconductor power unit 1 and the manufacturing method for ; therefore , they do not constitute a complete list of all embodiments . Actual arrangements and methods may vary from the embodiments shown in terms of cooler units , for example .
Reference signs
1 semiconductor power unit
2 cooler unit
21 upper surface of the cooler unit
22 power module recess of the cooler unit
3 inlet of the cooler unit
4 outlet of the cooler unit
5 coupling area
51 coupling recess
6 flow channel of the cooler unit
7 sealing element
71 sealing recess of the cooler unit
8 housing of the cooler unit
10 power module
11 cl amp
111 lower surface of the clamp
112 recess of the clamp
12 baseplate of the power module
121 lower surface of the baseplate
122 recess of the baseplate
13 cooling structure of the power module
14 exposed baseplate part
15 welding j oint
16 screw
161 screw protrusion
17 bolt
171 bolt protrusion
18 molded body /housing of the power module
19 terminal
S ( i ) steps of a method for manufacturing a semiconductor power unit

Claims

Claims
1. A semiconductor power unit (1) , comprising:
- at least one power module (10) with a baseplate (12) and a housing (18) , and
- a cooler unit (2) for cooling the at least one power module (10) during operation, wherein the at least one power module (10) is coupled to a housing (8) of the cooler unit
(2) by means of welding such that one or more welding joints
(15) are formed between at least two of the housing (8) of the cooler unit (2) , the at least one power module (10) and a coupling element (11, 16, 17) for fixing the at least one power module (10) to the housing (8) of the cooler unit (2) .
2. The semiconductor power unit (1) according to claim 1, wherein the welding joint (15) between the housing (8) of the cooler unit (2) , the at least one power module (10) and/or the coupling element (11, 16, 17) is formed by means of at least one of resistance welding, arc welding and laser welding .
3. The semiconductor power unit (1) according to any one of the preceding claims, wherein the one or more welding joints (15) are formed directly between an upper surface (21) of the housing (8) of the cooler unit (2) and a lower surface (121) of the baseplate (12) of the power module (10) .
4. The semiconductor power unit (1) according to claim 3, wherein the baseplate (12) of the power module (10) comprises one or more recesses (122) at the respective position of the one or more welding joints (15) .
5. The semiconductor power unit (1) according to any one of the preceding claims, wherein the coupling element comprises at least one of a screw (16) , a bolt (17) and a clamp (11) for fixing the at least one power module (10) to the housing (8) of the cooler unit (2) .
6. The semiconductor power unit (1) according to claim 5, wherein the one or more welding joints (15) are formed directly between an upper surface (21) of the housing (8) of the cooler unit (2) and a lower surface (111) of the clamp (11) •
7. The semiconductor power unit (1) according to claim 6, wherein the clamp (11) comprises one or more recesses (112) at the respective position of the one or more welding joints (15) .
8. The semiconductor power unit (1) according to one of the claims 5 to 7, wherein the clamp (11) comprises a penetrating recess in which the screw (16) or the bolt (17) is arranged, and wherein the one or more welding joints (15) are formed between the screw (16) or the bolt (17) and at least one of an upper surface (21) of the housing (8) of the cooler unit (2) , inside the penetrating recess of the clamp (11) and an upper surface of the clamp (11) facing away from the cooler unit ( 2 ) .
9. The semiconductor power unit (1) according to claim 8, wherein the housing (8) of the cooler unit (2) comprises a recess in coordination with the penetrating recess of the clamp (11) such that the screw (16) or the bolt (17) extends through penetrating recess of the clamp (11) into the recess of the housing (8) of the cooler unit (2) , and wherein the one or more welding joints (15) are formed between the screw
(16) or the bolt (17) and the housing (8) of the cooler unit (2) inside the recess of the housing (8) of the cooler unit (2) .
10. The semiconductor power unit (1) according to one of the claims 5 to 9, wherein the screw (16) and/or the bolt (17) comprises a respective welding protrusion (161, 171) configured for welding and facing the housing (8) of the cooler unit (2) such that the corresponding welding joint
(15) is formed at least partly by melting the welding protrusion (161, 171) .
11. The semiconductor power unit (1) according to claim 10, wherein the respective welding protrusion (161, 171) is formed at a head and/or a tip of the screw (16) or the bolt
(17) .
12. The semiconductor power unit (1) according to any one of the preceding claims in conjunction with claim 5, wherein the screw (16) and/or the bolt (11) comprises one or more recesses (112) at the respective position of the one or more welding joints (15) .
13. The semiconductor power unit (1) according to any one of the preceding claims, comprising: a sealing element (7) for sealing a contact area between the power module (10) and the cooler unit (2) , wherein the sealing element (7) is arranged inside a sealing recess (71) and contacts an upper surface (21) of the housing (8) on the one hand and a lower surface (121) of the baseplate (12) on the other hand.
14. A method for manufacturing a semiconductor power unit
( 1 ) , comprising :
- providing at least one power module (10) with a baseplate (12) and a housing (18) ,
- providing a cooler unit (2) for cooling the at least one power module (10) during operation, and
- coupling the at least one power module (10) to a housing (8) of the cooler unit (2) by means of welding such that one or more welding joints (15) are formed between at least two of the housing (8) of the cooler unit (2) , the at least one power module (10) and a coupling element (11, 16, 17) for fixing the at least one power module (10) to the housing (8) of the cooler unit (2) .
15. The method according to claim 14, wherein the step of coupling the at least one power module (10) to a housing (8) of the cooler unit (2) by means of welding comprises: forming the one or more welding joints (15) by means of at least one of resistance welding, arc welding and laser welding .
16. The method according to claim 14 or 15, wherein the step of coupling the at least one power module (10) to a housing (8) of the cooler unit (2) by means of welding comprises:
- pressing the at least one power module (10) and the housing (8) of the cooler unit (2) together, and
- forming the one or more welding joints (15) directly between an upper surface (21) of the housing (8) of the cooler unit (2) and a lower surface (121) of the baseplate (12) of the power module (10) .
17. The method according to any one of the claims 14 to 16, comprising : - providing the coupling element with at least a clamp (11) for fixing the at least one power module (10) to the housing (8) of the cooler unit (2) ,
- pressing the clamp (11) onto the at least one power module (10) and thereby pressing the at least one power module (10) and the housing (8) of the cooler unit (2) together, and
- forming the one or more welding joints (15) between the housing (8) of the cooler unit (2) , the at least one power module (10) and/or the clamp (11) .
18. The method according to claim 17, comprising:
- providing the coupling element with at least one of a screw (16) and a bolt (17) , and
- fixing the clamp (11) onto the at least one power module (10) and onto the housing (8) of the cooler unit (2) by means of attaching the screw (16) and/or the bolt (17) , and
- forming the one or more welding joints (15) between the housing (8) of the cooler unit (2) , the at least one power module (10) and/or the screw (16) and/or the bolt (17) .
PCT/EP2023/051653 2023-01-24 2023-01-24 Semiconductor power unit and method for manufacturing a semiconductor power unit WO2024156339A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2023/051653 WO2024156339A1 (en) 2023-01-24 2023-01-24 Semiconductor power unit and method for manufacturing a semiconductor power unit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2023/051653 WO2024156339A1 (en) 2023-01-24 2023-01-24 Semiconductor power unit and method for manufacturing a semiconductor power unit

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013236035A (en) * 2012-05-11 2013-11-21 Meidensha Corp Semiconductor module and manufacturing method of the same
US20170271239A1 (en) * 2016-03-15 2017-09-21 Fuji Electric Co., Ltd. Semiconductor module and manufacturing method of semiconductor module
US20220046830A1 (en) * 2019-03-04 2022-02-10 Audi Ag Electronic converter designed on the basis of welding technologies
CN114361122A (en) * 2021-08-11 2022-04-15 华为技术有限公司 Packaging structure and packaging method of power module
US20220142016A1 (en) * 2019-03-04 2022-05-05 Audi Ag Direct cooling of a power converter by using a stamped plate
US20220254653A1 (en) * 2019-07-25 2022-08-11 Hitachi Energy Switzerland Ag Arrangement of a Power Semiconductor Module and a Cooler

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013236035A (en) * 2012-05-11 2013-11-21 Meidensha Corp Semiconductor module and manufacturing method of the same
US20170271239A1 (en) * 2016-03-15 2017-09-21 Fuji Electric Co., Ltd. Semiconductor module and manufacturing method of semiconductor module
US20220046830A1 (en) * 2019-03-04 2022-02-10 Audi Ag Electronic converter designed on the basis of welding technologies
US20220142016A1 (en) * 2019-03-04 2022-05-05 Audi Ag Direct cooling of a power converter by using a stamped plate
US20220254653A1 (en) * 2019-07-25 2022-08-11 Hitachi Energy Switzerland Ag Arrangement of a Power Semiconductor Module and a Cooler
CN114361122A (en) * 2021-08-11 2022-04-15 华为技术有限公司 Packaging structure and packaging method of power module

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