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WO2012085952A1 - Assembly for the heat dissipation and the electrical connection of current-rectifier button diodes - Google Patents

Assembly for the heat dissipation and the electrical connection of current-rectifier button diodes Download PDF

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Publication number
WO2012085952A1
WO2012085952A1 PCT/IT2010/000525 IT2010000525W WO2012085952A1 WO 2012085952 A1 WO2012085952 A1 WO 2012085952A1 IT 2010000525 W IT2010000525 W IT 2010000525W WO 2012085952 A1 WO2012085952 A1 WO 2012085952A1
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WIPO (PCT)
Prior art keywords
assembly
fins
diode
diodes
insulator
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Ceased
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PCT/IT2010/000525
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French (fr)
Inventor
Valerio LOMI
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Pellini SpA
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Pellini SpA
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Publication of WO2012085952A1 publication Critical patent/WO2012085952A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of semiconductor or other solid state devices
    • H01L25/03—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes
    • H01L25/10—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices having separate containers
    • H01L25/11—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices having separate containers the devices being of a type provided for in subclass H10D
    • H01L25/115—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices having separate containers the devices being of a type provided for in subclass H10D the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/02—Containers; Seals
    • H01L23/04—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls
    • H01L23/043—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls the container being a hollow construction and having a conductive base as a mounting as well as a lead for the semiconductor body
    • H01L23/051—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls the container being a hollow construction and having a conductive base as a mounting as well as a lead for the semiconductor body another lead being formed by a cover plate parallel to the base plate, e.g. sandwich type
    • 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
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H01L23/367—Cooling facilitated by shape of device
    • H01L23/3672—Foil-like cooling fins or heat sinks
    • 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
    • H01L23/4012—Mountings or securing means for detachable cooling or heating arrangements ; fixed by friction, plugs or springs with bolts or screws for stacked arrangements of a plurality of semiconductor devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/71—Means for bonding not being attached to, or not being formed on, the surface to be connected
    • H01L24/72—Detachable connecting means consisting of mechanical auxiliary parts connecting the device, e.g. pressure contacts using springs or clips
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of semiconductor or other solid state devices
    • H01L25/03—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes
    • H01L25/04—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
    • H01L25/07—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group subclass H10D
    • H01L25/072—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group subclass H10D the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of semiconductor or other solid state devices
    • H01L25/03—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes
    • H01L25/10—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices having separate containers
    • H01L25/11—Assemblies consisting of a plurality of semiconductor or other solid state devices all the devices being of a type provided for in a single subclass of subclasses H10B, H10D, H10F, H10H, H10K or H10N, e.g. assemblies of rectifier diodes the devices having separate containers the devices being of a type provided for in subclass H10D
    • H01L25/117—Stacked arrangements of devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4258—Arrangements for improving power factor of AC input using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/02—Bonding areas; Manufacturing methods related thereto
    • H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
    • H01L2224/06—Structure, shape, material or disposition of the bonding areas prior to the connecting process of a plurality of bonding areas
    • H01L2224/061—Disposition
    • H01L2224/0618—Disposition being disposed on at least two different sides of the body, e.g. dual array
    • H01L2224/06181—On opposite sides of the body
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/02—Bonding areas ; Manufacturing methods related thereto
    • H01L24/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
    • H01L24/06—Structure, shape, material or disposition of the bonding areas prior to the connecting process of a plurality of bonding areas
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01029—Copper [Cu]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/11—Device type
    • H01L2924/13—Discrete devices, e.g. 3 terminal devices
    • H01L2924/1301—Thyristor
    • H01L2924/13033—TRIAC - Triode for Alternating Current - A bidirectional switching device containing two thyristor structures with common gate contact
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Definitions

  • the present invention concerns the field of the industrial current rectifier circuits, and more particularly to an assembly for the heat dissipation and the electrical connection of current-rectifier button diodes.
  • FIG. 1 gives a diagram of a full-wave, three-phase rectifier that receives three-phase voltages Fl, F2, F3 displaced by 120° one from another and presents a direct voltage output V+ and V- affected by a residual ripple of 13.5% to be levelled by a suitable capacitor.
  • the rectifier uses six diodes Dl, D2, D3, D4, D5, D6 connected in a Graetz bridge configuration where, in a period of 360° of phase voltage, each diode conducts for a fraction of the phase angle of 120°, dissipating electric power on its internal resistance; though of a low value, this can produce a considerable amount of heat by the Joule effect where strong conduction currents are present.
  • Each diode in the bridge must therefore be efficiently cooled and for this the diodes are mounted on devices for dissipating the larger quantities of heat into the environment or connected to heat exchangers for cooling by forced circulation of water or some other cooling fluid.
  • Figure 2 shows a perspective of a button diode 1, consisting of a slightly convex cylindrical case 2 of thermosetting plastic, from whose upper and lower bases respectively two cylindrical electrodes 3, 4 project. These form the anode and cathode of diode 1 and their diameter is smaller than that of the diode case.
  • Press-fit technique in holes made through the thickness of a rectangular fin acting as a heat dissipator, is often used for mounting diodes of type 1.
  • the fin contains several diodes in previously decided positions all having the same pole connected to the fin, some for negative polarity and others for positive polarity.
  • the button diode is a semiconductor chip between two nickel-plated copper heat dissipators in thermal and electrical continuity with the respective electrodes that emerge from the case of thermosetting plastic. The way it is made clearly shows how the heat from inside is transmitted through the electrodes.
  • FIGs 3, 4, 5 shows how the press-fit technique is used in building the diode bridge in Figure 1.
  • FIG 3 shows the full- wave rectifier bridge in Figure 1 where each diode is represented by a respective aluminium fin 10 carrying four diodes connected in parallel to increase the passage of current.
  • the bridge therefore equips six identical heat dissipating fins of type 10 marked DDI, DD2, DD3, DD4, DD5, DD6 corresponding to diodes Dl, D2, D3, D4, D5, D6.
  • Terminals for phase input are marked FFl, FF2, FF3, output terminals for rectified current being marked VV+ and VV-.
  • a screw 16 penetrates into longitudinally aligned holes, present in all the elements forming the pile, to tighten the fins by a nut 17. Screw 16 and nut 17 are electrically insulated by elements in the pile.
  • Figure 4 shows the completion of a fin 10 with four diodes la, lb, lc, Id at the vertices of a quadrilateral with a hole 11 at the centre.
  • a ceramic cylinder 12 with central hole stands on the fin 10 and is glued in place aligned with the axis of hole 11.
  • a tinned-iron washer 13 is laid on the front face of the cylinder 12.
  • the washer 13 has a central hole and is cut to create four leads 14 projecting from the circular edge of the washer in the form of a cross.
  • the four diodes are connected to their respective leads 14 by elongated terminals 6 bent at 90°. One end of each terminal 6 is brazed onto an electrode of the diode and the other end is connected to the lead 14 by resistance welding.
  • an aluminium washer 15 Laid against the washer 13, with the four welds, is an aluminium washer 15 also with a hole in its centre; the diameter of the washer 15 is sufficient to cover the welded leads 14 and protect the terminals 6. Resting against the washer 15 is a thin metal bar FF3 that constitutes an electrical terminal for the four diodes connected in parallel. The screw 16 passes through a hole in the terminal FF3 and through holes aligned on the axis of hole 11 to tighten the piled up elements.
  • the fins of type 10 completed as described, can be made with two polarities.
  • electrode 3 either anode or cathode, of diode la is oven-brazed to the flared head 5 of terminal 6.
  • a low-temperature alloy 7 is used as a filler between the two surfaces to be welded.
  • the liquid metal fills by effect of capillarity all the voids and, when cool, solidifies creating a strong join.
  • the same process is carried out for the other electrode 4 to join it to a cylindrical metal boss 8.
  • the boss is driven through a hole 9 made in the thickness of the metal fin 10, constituting a heat dissipator at the electrical potential of the electrode 4.
  • the same process of brazing and press-fit is carried out for all the diodes mounted on fin 10.
  • the chief drawback to the mounting process described above is that it allows cooling diodes of a mono-facial type, namely those that can dissipate the heat at a single electrode; the number of diodes on the dissipating fin being equal, this limitation makes necessary a much larger fin surface as the quantity of current used increases, to a point where the fin becomes a heavy and bulky plate.
  • a further drawback consists in the complex process of brazing the anode and cathode electrodes of each diode to their respective terminals, bosses and nails, for which careful testing is required.
  • the press-fit technique needs special equipment; the washers and nails must be designed and manufactured separately.
  • One last drawback lies in the fact that the fins are usually of a standard size, e.g. mm 100x100, 100x200, 100x250 and so on, but these sizes are not always the best for the number of diodes in use.
  • Purpose of the present invention is to permit bifacial cooling of button diodes.
  • a further purpose is to avoid having to resort to oven-brazing for connections to the electrodes.
  • Another purpose is to avoid the use of press-fit technique in mounting the diodes on the dissipators.
  • Another purpose is to simplify assembly as far as possible and therefore disassembly for carrying out repairs.
  • Another purpose is to avoid waste of metal if the dissipators are not fully used.
  • Another purpose is to secure a drastic reduction in production costs of rectifier bridges or other devices that include diodes.
  • subject of the present invention is an assembly for thermal dissipation and for electrically connecting current-rectifier button diodes in which, according to the invention, for at least one power diode the assembly includes:
  • said two shoulders can be fitted onto the case by an element made of the same insulating material mounted between them, said element being designed to accept insertion of the diode.
  • the two said shoulders form an integral part of the diode case.
  • Threfore another subject of the invention is a button diode for the assembly described above wherein the case has two rigid shoulders forming part of the case itself, the two shoulders standing on diametrically opposite sides of the case, each shoulder having two ends that extend beyond respective electrodes of the diode, each end having a protrusion facing towards the protrusion on the opposite shoulder.
  • said holes are rectangular to take parallelepiped-shaped shoulders that fit into the holes without appreciable play.
  • said protrusion delimits a transversal groove in the contiguous body of the shoulder open towards an opposite groove to receive a respective end of a flat spring.
  • the assembly further includes:
  • an insulator with a central hole and two opposite flat faces and at least one depression in each flat face, the insulator being inserted between the two fins at a vertex of said fins, said vertex fitting into a respective depression;
  • a slit in the fins set at a distance from the vertex greater than the depth of the depression in the insulator so limiting heat transfer towards said insulator.
  • said washers are made of metal, a terminal for electrical connection being inserted between at least one washer and the fixing means.
  • said washers are insulating.
  • faston male connectors are formed by notches cut in the edge of the fins.
  • the assembly also includes:
  • each unitary assembly said vertex of the respective fins subtending an angle of 2 / ⁇ radian, and is cut off;
  • the insulator is ring-shaped and has N symmetrical depressions to contain an equivalent number of fin parts at the respective cut-off vertices, said fin parts being electrically insulated one from another by protrusions that delimit adjacent depressions.
  • the fins are shaped like circular sectors and the cut-off vertex like an identical angular part of a ring.
  • the assembly for current rectifier circuits with full- wave M phases includes:
  • the present invention offers numerous advantages that entirely avoid the drawbacks described above.
  • Button diodes can be cooled on both sides due to the close contact maintained between the fins and electrodes on the diode ensured by the strong pressure exerted by the two flat springs. Efficient cooling increases reliability of the rectifier bridges and lengthens their working life. In addition less expensive diodes can be used at a value of current closer to the maximum allowed. As the electrodes of the diode are in direct contact with the fins, the fins themselves can function as electrical terminals making both oven-brazing for applying terminals and press-fit unnecessary.
  • M fins only can be assembled avoiding waste of metal there would have been if the standard sized fins required for press-fit had been needed.
  • edges of thin fins can be bent over the eges, thus avoiding possible objections to sharp edges.
  • Figure 1 shows a circuit scheme of a full-wave three-phase current rectifier in a six-diode Graetz bridge configuration.
  • Figure 2 is a perspective view of a button diode.
  • Figure 3 is a perspective view of a current rectifier in which the circuit in Figure 1 is realized according to the known press-fit art.
  • Figure 4 is a perspective view of a fin of the rectifier in Figure 3 for four button diodes in parallel.
  • Figure 5 is a partial view in cross section along a plane that passes through the centre of both electrodes of a diode.
  • Figure 6 is an exploded perspective view of the assembly here invented applied to a single button diode.
  • Figure 7 shows a partial recomposition of the elements forming the previous figure.
  • Figure 8 is a section on a plane perpendicular to the fin through the radial axis shown in Figure 7.
  • Figure 9 is a view from above of an assembly in figure 7 repeated for four button diodes.
  • Figure 10 shows an elevation of the assembly in Figure 9.
  • Figure 11 is a perspective view of the assembly in Figure 9.
  • Figure 12 is the circuit scheme in Figure 1 wherein each diode is replaced by four diodes in parallel.
  • Figure 13 is a perspective view of a current rectifier that realizes the circuit scheme in Figure 12, as a pile of assemblies as that shown in Figure 11.
  • Figure 14 is a longitudinal section of the current rectifier in Figure 13.
  • FIG. 6 shows a button diode 20 with two electrodes 62, 63, anode and cathode respectively, projecting from case 64 at the centre of an assembly comprising: a container 21 to hold the diode 20, two identical heat-dissipating fins 22, 23 shaped substantially like a circular sector, two flat springs 24, 25 slightly curved towards a respective fin, a ring-shaped insulator 26 and two metal washers 27, 28.
  • fin 22 are two rectangular holes 29, 30 perfectly symmetrical to a radial axis, cut at about halfway along the radius.
  • the circular-sector shape with a central angle of 90° of the fins 22 and 23, changes before reaching the vertex becoming that of a sector of a ring, respectively 33 and 34, of equal angular amplitude. Between the two forms is a slot, respectively 35 and 36, that approximately extends from one side to the other of the fin.
  • fin 23 In fin 23 are two holes 31, 32, identical to holes 29, 30 and situated at identical positions on the fin.
  • a short length of the ends of the flat springs 24, 25 is turned over onto the convex part.
  • the insulator 26 is cylindrical with a central hole 37 and four identical protrusions for each base, disposed crosswise and aligned between the two faces; most clearly seen are the protrusions 38, 39, 40, 41 on the upper face.
  • the protrusions are rectangular and delimit four depressions shaped as sectors of a ring 42, 43, 44, 45 their size being substantially identical with that of the terminal part 33 of the fin 22.
  • the insulator 26 may be described as having four depressions, shaped as sectors of a ring, 42, 43, 44, 45, on each face shaped separated by four protrusions 38, 39, 40, 41.
  • the diameter of the metal washers 27, 28 is substantially equal to that of the insulator 26.
  • An electrically insulated screw (not shown) passes through the aligned holes in the washers 27, 28.
  • the container 21 consists of a central ring 50 its internal diameter permitting the button diode 20 to be inserted by applying a slight pressure, alternatively by allowing a small tolerance on the internal diameter of the central ring compared with that of the diode case.
  • the central ring 50 is held in place by two identical parallelepiped-shaped shoulders 51, 52, one opposite the other, and of a size that enables them to enter the holes in the fins 22, 23 without appreciable play between the two dimensions of the hole.
  • At the two ends of the shoulder 51 is a projection that delimits a groove, respectively 53 and 54, in the contiguous body of the shoulder.
  • the two ends of the shoulder 52 end with a projection that delimits a groove, respectively 55 and 56, in the contiguous body of the shoulder.
  • the grooves in the one shoulder are open towards those in the other shoulder, namely towards the inside of the container 21.
  • the fins 22, 23 are of aluminium, thickness 0.8 mm.
  • the container 21 is a single body of thermosetting epoxy resin.
  • the diode 20 presents no limitations, being chosen from among those available on the market possessing the necessary requisites of inverse voltage and maximum conduction current set for the specific circuits in which it is used.
  • the diode 20 is fitted into the ring 50 in the container 21 after which the ends of the shoulders 51, 52 containing the button diode 20, are fitted into the rectangular holes 29, 30 in fin 22, and into the rectangular holes 31, 32 in fin 23.
  • Shoulder height is such that grooves 53, 54 and 55, 56 will project from the external face of respective fins 22 and 23 when the anode and cathode of diode 20 make contact with them at the strips of fin comprised between rectangular holes 29, 30 and 31, 32.
  • the ends of the flat spring 24 are fitted into the opposite grooves 53, 55 present in the upper ends of shoulders 51, 52 with the convexity in contact with the fin 22.
  • the ends of the flat spring 25 are then fitted into the opposing grooves 54, 56 at the lower ends of shoulders 51, 52.
  • the first flat spring 24 fits in without apparent effort while application of the second flat spring 25 requires some pressure to compress the first flat spring.
  • the two flat springs 24, 25 will exert pressure of between 78.4 and 98 Newton (8-10 kg) and will become almost completely flat since, as shown in Figure 7, the base of the grooves projects from the rectangular holes by about the thickness of the flat spring.
  • the insulator 26 fits in between the two fins 22, 23 to allow the two terminal pieces, shaped as sectors of ring 33, 34 to enter the respective depressions 45. Protrusions 38, 41 prevent the terminal part 33 from moving beyond the edge of the hole 37.
  • Figure 8 shows the section of the assembly in Figure 7 according to the radial axis in this figure.
  • the two electrodes 62, 63 of diode 20 are held firmly against the fins 22, 23 due to compression exerted by the flat springs 24, 25 placed immediately above. In this way heat produced by the diode is conducted by the electrodes to the respective fins and, in addition, fins 22, 23 assume the polarity of the respective electrodes 62, 63 and could therefore be used directly as terminals.
  • This solution is illustrated in Figure 7a where two male faston connectors 60, 61 can be seen at a pair of distal vertices of fins 22, 23, obtaind by simply cutting two suitably long notches and two holes aligned for each connector.
  • the faston connectors 60, 61 make the assembly in Figure 7 highly flexible in use especially in multiple assemblies on the same insulator 26.
  • the figure 8 shows the gap 35 between fins 22, 23 and insulator 26 that limits transfer of heat towards the latter.
  • Figure 9 shows a quadruple assembly DDI in which the assembly in Figure 7, here marked AS1, is repeated four times, completing all the depressions 42, 43, 44, 45 between protrusions 38, 39, 40, 41 present on the two faces of the central cylindrical insulator 26.
  • Assembly DDI therefore consists of the four contiguous assemblies ASl, AS2, AS3, AS4 separated by four open spaces 68, 69, 70, 71 on the extension of protrusions 38, 39, 40, 41.
  • the upper face of assembly DDI is seen with assembly ASl showing the upper fin 22 and the flat spring 24 compressed between shoulders 51, 52.
  • Assembly AS2 shows an upper fin 65 with a flat spring 72 compressed between two shoulders 73 and 74.
  • Assembly AS3 shows an upper fin 66 with a flat spring 75 compressed between two shoulders 76 and 77; and assembly AS4 shows an upper fin 67 with a flat spring 78 compressed between two shoulders 79 and 80.
  • the two aluminium washers 27, 28 lie one above the other at the ends of the fins in their seats on the insulator 26 connecting in parallel the four diodes held between the respective fins.
  • insulating washers can be used for mechanically constraining the fins of the four assemblies against the two faces of the central insulator 26, making the various diodes independent. In that case faston connections made on the fins can be used.
  • Figure 10 shows an elevation of the quadruple assembly DDI viewed from the left hand side of this figure.
  • DDI assembly is perfectly symmetrical, this view is the same for all equivalent positions.
  • This is an extended view of assembly ASl and partly of adjacent assemblies, AS4 to the right and AS2 to the left seprated by open gaps 71 and 68.
  • assembly ASl button diode 20 appears with its case fitted into the ring-wise seat 50 of its container, the anode and cathode being in contact either with fin 22 or with fin 23, pressed against the electrodes by the upper flat spring 24 and by a lower flat spring 83 held by the grooves in the opposing shoulders 51, 52 that project from the fins.
  • Assembly AS4 shows a button diode 81 with its case fitted into a ringwise seat of a relative container, and also its height above the two fins.
  • assembly AS2 shows a button diode 82 with the case fitted into a circular seat of a relative container.
  • Figure 11 gives details of the plan view in Figure 9 also showing the lower fins of the four assemblies and the side of the insulator 26.
  • fin 22 lies above a fin 23; in assembly AS2 fin 65 lies above a fin 83; in assembly AS3 fin 66 lies above a fin 84; in assembly AS4 fin 67 lies above a fin 85.
  • Figure 12 shows a diode current-rectifier circuit equivalent to the three-phase Graetz bridge in Figure 1, if single diodes Dl, D2, D3, D4, D5, D6 are replaced with the parallel of four diodes from each assembly ASl, AS2, AS3, AS4.
  • FIG. 13 A realization of the current rectifier in Figure 12 is shown in Figure 13 with a pile of quadruple assemblies identical to assembly DDI in Figure 11.
  • the pile of elements includes: quadruple assemblies DDI, DD2, DD3, DD4, DD5, DD6 connected as shown in Figure 12 by phase contact terminals FF1, FF2, FF3 and U-shaped terminals VV+ and VV- for positive and negative polarity contacts.
  • the pile of quadruple assemblies including terminals is tightened by a central screw 90 that passes through the central hole 37 of all the insulators 26, of all the aluminium washers 27, 28 and interposed terminals. Screw 90 is kept electrically insulated by the walls of the holes through which it passes, as also by the tightening walls with insulating washers as will be better explained in the next figure.
  • Figure 14 is a cross section of the pile in Figure 13 along a longitudinal plane of symmetry.
  • the screw 90 passes through the pile and emerges at the two ends where it is bolted by two nuts, 91a, 91b, two washers 92a, 92b, and two insulating washers 93a, 93b.
  • the screw 90 is inserted in an insulating cylinder ensuring permanent electrical insulation.
  • An insulating screw can be used as an alternative.
  • the figure shows that pierced terminals FF1, FF2, FF3, VV+ and VV- are connected by inserting them between adjacent metal washers. More generally, for M phases there will be 2M multiple assemblies, M phase terminals and M - 1 terminals for each polarity of rectified current.
  • Each multiple assembly includes N button diodes making a total of 2MxN diodes.
  • Figure 14 shows a realization of the invention in all its compactness, modular structure and efficacy making clear its capacity to control strong current while employing button dioides of submultiple amperage; these can be used at values closer to the maximum permetted thanks to the efficacy of bifacial cooling.
  • each protrusion consists of a trapezoidal tooth placed at the end of a shank in the body of the shoulder through the hole in the fin.
  • the flat spring can have a small notch at each end to accommodate the shank while the base of the tooth presses against the fin.

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Abstract

A bifacial heat dissipator for a power button diode (20) comprises two fins (22,23) shaped like circular sectors, with the cut-off vertex contiguous to a part of said fins shaped like a sector of a ring having the same angular amplitude. In each fin there are two rectangular holes (29,30,31.32) specular in relation to a radial axis, aligned in the same substantially central positions. The fins form part of an assembly that also uses two flat springs (24,25) to exert pressure against the anode (62) and the cathode (63) of the diode in a container of thermosetting plastic. The container consists of a ring between two rectangular shoulders (51,52) all forming a single whole. In each shoulder there is an inward- facing transversal groove (53,54,55,56) close to each end. The grooves project beyond the external face of the fins for insertion under pressure of flat springs. An assembly of four diodes in parallel comprises a ring-shaped insulator (26) with flat faces and four protrusions set crosswise that delimit four seperate depressions (42,43,44,45) to receive the terminal parts of the fins. Two aluminium washers (27,28) are superimposed over the terminal parts projecting beyond the edge of their seats. With a pile of these assemblies a three-phase full -wave Graetz bridge rectifier can be realized. An electrically insulated central screw (90, 91a, 91b) tightens all the assemblies together with the phase and terminal polarities of the rectified current placed between adjacent washers in suitable positions.

Description

Assembly for the heat dissipation and the electrical connection of current-rectifier button diodes
Field of application of the invention
The present invention concerns the field of the industrial current rectifier circuits, and more particularly to an assembly for the heat dissipation and the electrical connection of current-rectifier button diodes.
Review of the known art
Many industrial activities require availability of direct current, for example for rail traction, for recharging car batteries, for radio transmission systems and so on. The power levels needed vary from a few kilowatts to thousands, raising the problem of how to make such power levels available where they are needed. The main electrical network can supply three-phase sinusoidal alternating current (AC) at 50 Hz and 380V all over the country through its substations. AC current must be brought to the required voltage and converted to DC. Figure 1 gives a diagram of a full-wave, three-phase rectifier that receives three-phase voltages Fl, F2, F3 displaced by 120° one from another and presents a direct voltage output V+ and V- affected by a residual ripple of 13.5% to be levelled by a suitable capacitor. The rectifier uses six diodes Dl, D2, D3, D4, D5, D6 connected in a Graetz bridge configuration where, in a period of 360° of phase voltage, each diode conducts for a fraction of the phase angle of 120°, dissipating electric power on its internal resistance; though of a low value, this can produce a considerable amount of heat by the Joule effect where strong conduction currents are present. Each diode in the bridge must therefore be efficiently cooled and for this the diodes are mounted on devices for dissipating the larger quantities of heat into the environment or connected to heat exchangers for cooling by forced circulation of water or some other cooling fluid. The problem of heat dissipation in diodes is common to other solid-state power devices as well, such as FET, SCR, BJT, triac and others and for each device ad hoc solutions have been worked out. Limiting the field of application to power diodes only, several models of these devices are available but differ as to case form and to the position of the electrodes, such as button, disc and screw diodes, etc. For each model there are mounting solutions that include mechanical immobilization, electrical connection and heat dissipation. Three-phase and monophase rectifiers are available on the market as a single assembly especally for the lower power range. The invention that will be described here concerns "button" diodes only, so named because their shape is similar to that of a button.
Figure 2 shows a perspective of a button diode 1, consisting of a slightly convex cylindrical case 2 of thermosetting plastic, from whose upper and lower bases respectively two cylindrical electrodes 3, 4 project. These form the anode and cathode of diode 1 and their diameter is smaller than that of the diode case. Press-fit technique, in holes made through the thickness of a rectangular fin acting as a heat dissipator, is often used for mounting diodes of type 1. The fin contains several diodes in previously decided positions all having the same pole connected to the fin, some for negative polarity and others for positive polarity. The button diode is a semiconductor chip between two nickel-plated copper heat dissipators in thermal and electrical continuity with the respective electrodes that emerge from the case of thermosetting plastic. The way it is made clearly shows how the heat from inside is transmitted through the electrodes.
Figures 3, 4, 5 shows how the press-fit technique is used in building the diode bridge in Figure 1.
Figure 3 shows the full- wave rectifier bridge in Figure 1 where each diode is represented by a respective aluminium fin 10 carrying four diodes connected in parallel to increase the passage of current. The bridge therefore equips six identical heat dissipating fins of type 10 marked DDI, DD2, DD3, DD4, DD5, DD6 corresponding to diodes Dl, D2, D3, D4, D5, D6. Terminals for phase input are marked FFl, FF2, FF3, output terminals for rectified current being marked VV+ and VV-. A screw 16 penetrates into longitudinally aligned holes, present in all the elements forming the pile, to tighten the fins by a nut 17. Screw 16 and nut 17 are electrically insulated by elements in the pile. Figure 4 shows the completion of a fin 10 with four diodes la, lb, lc, Id at the vertices of a quadrilateral with a hole 11 at the centre. A ceramic cylinder 12 with central hole stands on the fin 10 and is glued in place aligned with the axis of hole 11. A tinned-iron washer 13 is laid on the front face of the cylinder 12. The washer 13 has a central hole and is cut to create four leads 14 projecting from the circular edge of the washer in the form of a cross. The four diodes are connected to their respective leads 14 by elongated terminals 6 bent at 90°. One end of each terminal 6 is brazed onto an electrode of the diode and the other end is connected to the lead 14 by resistance welding. Laid against the washer 13, with the four welds, is an aluminium washer 15 also with a hole in its centre; the diameter of the washer 15 is sufficient to cover the welded leads 14 and protect the terminals 6. Resting against the washer 15 is a thin metal bar FF3 that constitutes an electrical terminal for the four diodes connected in parallel. The screw 16 passes through a hole in the terminal FF3 and through holes aligned on the axis of hole 11 to tighten the piled up elements.
In accordance with the foregoing, the fins of type 10, completed as described, can be made with two polarities.
With reference to Figure 5 showing diode la mounted on the fin 10, it will be seen that electrode 3, either anode or cathode, of diode la is oven-brazed to the flared head 5 of terminal 6. For brazing purposes a low-temperature alloy 7 is used as a filler between the two surfaces to be welded. The liquid metal fills by effect of capillarity all the voids and, when cool, solidifies creating a strong join. The same process is carried out for the other electrode 4 to join it to a cylindrical metal boss 8. By means of a press-fit device the boss is driven through a hole 9 made in the thickness of the metal fin 10, constituting a heat dissipator at the electrical potential of the electrode 4. The same process of brazing and press-fit is carried out for all the diodes mounted on fin 10.
Technical problems encountered in the known art
The chief drawback to the mounting process described above is that it allows cooling diodes of a mono-facial type, namely those that can dissipate the heat at a single electrode; the number of diodes on the dissipating fin being equal, this limitation makes necessary a much larger fin surface as the quantity of current used increases, to a point where the fin becomes a heavy and bulky plate.
A further drawback consists in the complex process of brazing the anode and cathode electrodes of each diode to their respective terminals, bosses and nails, for which careful testing is required. The press-fit technique needs special equipment; the washers and nails must be designed and manufactured separately.
Complex repairs constitute another drawback. As the diodes are in parallel, all the nails on each washer must be unsoldered to discover a faulty diode, in the worst case the operation has to be repeated for all the washers on the fin, after which the faulty diode must be removed by a compressor and replaced with another, with terminals already brazed, by means of the press-fit process; finally, rewelding all the nails previously unsoldered. A complication of no mean kind!
One last drawback lies in the fact that the fins are usually of a standard size, e.g. mm 100x100, 100x200, 100x250 and so on, but these sizes are not always the best for the number of diodes in use.
There are solutions for cooling the bifacial so-called disk-type diodes but, unlike the button diodes, their electrodes lie flush with the insulating container and therefore need mounting of a different kind. This geometrical arrangement of the diodes favours realization of structures with superimposed flat fins in which the diode is pressed between two dissipator fins so that each electrode is in close contact with a respective fin. But mounting diodes at the dissipators is not as simple as it might seem as special "beaker"-type insulators are needed through which to pass the screws for tightening the dissipators against their respective electrodes to be cooled. This drastically limits the number of diodes that can be mounted at the dissipators, usually one only at the centre of the fins. Purpose of the invention
Purpose of the present invention is to permit bifacial cooling of button diodes. A further purpose is to avoid having to resort to oven-brazing for connections to the electrodes.
Another purpose is to avoid the use of press-fit technique in mounting the diodes on the dissipators.
Another purpose is to simplify assembly as far as possible and therefore disassembly for carrying out repairs.
Another purpose is to avoid waste of metal if the dissipators are not fully used.
Another purpose is to secure a drastic reduction in production costs of rectifier bridges or other devices that include diodes.
Summary of the invention
To achieve these purposes, subject of the present invention is an assembly for thermal dissipation and for electrically connecting current-rectifier button diodes in which, according to the invention, for at least one power diode the assembly includes:
- two rigid shoulders of insulating material to fit onto the diametrically opposite sides of the case of the diode there being at the two ends of each one a protrusion facing towards a similar protrusion on the opposite shoulder;
- two metal fins each having two holes equally spaced in the two fins for insertion of respective ends of the two shoulders, said protrusions extending beyond the external face of the fins, and said fins being in contact with respective electrodes on the button diode;
- resilient means placed between said protrusions and respective fins for exerting pressure on the fins to maintain their close contact with said electrodes, as described in claim 1.
Further characteristics of the present invention, in its various realized forms considered innovative, are described in the dependent claims. According to one aspect of the invention said two shoulders can be fitted onto the case by an element made of the same insulating material mounted between them, said element being designed to accept insertion of the diode.
According to one aspect of the invention the two said shoulders form an integral part of the diode case.
Threfore another subject of the invention is a button diode for the assembly described above wherein the case has two rigid shoulders forming part of the case itself, the two shoulders standing on diametrically opposite sides of the case, each shoulder having two ends that extend beyond respective electrodes of the diode, each end having a protrusion facing towards the protrusion on the opposite shoulder.
According to one aspect of the invention, said holes are rectangular to take parallelepiped-shaped shoulders that fit into the holes without appreciable play. According to one aspect of the invention, said protrusion delimits a transversal groove in the contiguous body of the shoulder open towards an opposite groove to receive a respective end of a flat spring.
According to one aspect of the invention the assembly further includes:
- an insulator with a central hole and two opposite flat faces and at least one depression in each flat face, the insulator being inserted between the two fins at a vertex of said fins, said vertex fitting into a respective depression;
- a washer for each flat face of the insulator, resting on that part of the fin that raises above the edge of the depression;
- means for fixing the washers on the fins, said means crossing the insulator and pressing against the two washers.
According to one aspect of the invention, there is a slit in the fins set at a distance from the vertex greater than the depth of the depression in the insulator so limiting heat transfer towards said insulator.
According to one aspect of the invention, said washers are made of metal, a terminal for electrical connection being inserted between at least one washer and the fixing means.
According to one aspect of the invention that permits independent use of single diodes, said washers are insulating. According to one aspect of the invention, faston male connectors are formed by notches cut in the edge of the fins.
In one example of its execution for N button diodes, the assembly also includes:
- N identical assemblies per power diode, in each unitary assembly said vertex of the respective fins subtending an angle of 2 /Ν radian, and is cut off;
- the insulator is ring-shaped and has N symmetrical depressions to contain an equivalent number of fin parts at the respective cut-off vertices, said fin parts being electrically insulated one from another by protrusions that delimit adjacent depressions.
According to one aspect of the invention the fins are shaped like circular sectors and the cut-off vertex like an identical angular part of a ring.
According to one aspect of the invention the fins are square in shape by N = 4. According to one aspect of the invention the assembly for current rectifier circuits with full- wave M phases includes:
- 2M identical assemblies for N button diodes one above another to form a pile;
- M input terminals of the phases and M-l output terminals for each of the two polarities of rectified current, said terminals being bored at one end between adjacent washers;
- a large screw passed through the centre of the pile, electrically insulated against the conductors through which the screw passess.
Advantages of the invention
The present invention offers numerous advantages that entirely avoid the drawbacks described above.
Button diodes can be cooled on both sides due to the close contact maintained between the fins and electrodes on the diode ensured by the strong pressure exerted by the two flat springs. Efficient cooling increases reliability of the rectifier bridges and lengthens their working life. In addition less expensive diodes can be used at a value of current closer to the maximum allowed. As the electrodes of the diode are in direct contact with the fins, the fins themselves can function as electrical terminals making both oven-brazing for applying terminals and press-fit unnecessary.
The assembly and disassembly of diodes is greatly simplified; in the N diode assembly even one diode only can be assembled and disassembled without having to touch the others.
Where M<N diodes are used in parallel, M fins only can be assembled avoiding waste of metal there would have been if the standard sized fins required for press-fit had been needed.
The edges of thin fins can be bent over the eges, thus avoiding possible objections to sharp edges.
Production costs of rectifier bridges are drastically reduced by the assembly according to the invention where the process is entirely cold.
Short description of the figures
Further purposes and advantages of the present invention will be made clear by the following detailed description of an example of its realization illustrated by the attached drawings provided purely for explanatory reasons and in no way limitative, wherein:
Figure 1 shows a circuit scheme of a full-wave three-phase current rectifier in a six-diode Graetz bridge configuration.
Figure 2 is a perspective view of a button diode.
Figure 3 is a perspective view of a current rectifier in which the circuit in Figure 1 is realized according to the known press-fit art.
Figure 4 is a perspective view of a fin of the rectifier in Figure 3 for four button diodes in parallel.
Figure 5 is a partial view in cross section along a plane that passes through the centre of both electrodes of a diode.
Figure 6 is an exploded perspective view of the assembly here invented applied to a single button diode.
Figure 7 shows a partial recomposition of the elements forming the previous figure. Figure 8 is a section on a plane perpendicular to the fin through the radial axis shown in Figure 7.
Figure 9 is a view from above of an assembly in figure 7 repeated for four button diodes.
Figure 10 shows an elevation of the assembly in Figure 9.
Figure 11 is a perspective view of the assembly in Figure 9.
Figure 12 is the circuit scheme in Figure 1 wherein each diode is replaced by four diodes in parallel.
Figure 13 is a perspective view of a current rectifier that realizes the circuit scheme in Figure 12, as a pile of assemblies as that shown in Figure 11.
Figure 14 is a longitudinal section of the current rectifier in Figure 13.
Detailed description of some preferred forms of realizing the invention
In the following description scale and proportions of the various parts shown may not correspond to the real ones.
The exploded view in Figure 6 shows a button diode 20 with two electrodes 62, 63, anode and cathode respectively, projecting from case 64 at the centre of an assembly comprising: a container 21 to hold the diode 20, two identical heat-dissipating fins 22, 23 shaped substantially like a circular sector, two flat springs 24, 25 slightly curved towards a respective fin, a ring-shaped insulator 26 and two metal washers 27, 28. In fin 22 are two rectangular holes 29, 30 perfectly symmetrical to a radial axis, cut at about halfway along the radius. The circular-sector shape, with a central angle of 90° of the fins 22 and 23, changes before reaching the vertex becoming that of a sector of a ring, respectively 33 and 34, of equal angular amplitude. Between the two forms is a slot, respectively 35 and 36, that approximately extends from one side to the other of the fin. In fin 23 are two holes 31, 32, identical to holes 29, 30 and situated at identical positions on the fin. A short length of the ends of the flat springs 24, 25 is turned over onto the convex part. The insulator 26 is cylindrical with a central hole 37 and four identical protrusions for each base, disposed crosswise and aligned between the two faces; most clearly seen are the protrusions 38, 39, 40, 41 on the upper face. The protrusions are rectangular and delimit four depressions shaped as sectors of a ring 42, 43, 44, 45 their size being substantially identical with that of the terminal part 33 of the fin 22. The insulator 26 may be described as having four depressions, shaped as sectors of a ring, 42, 43, 44, 45, on each face shaped separated by four protrusions 38, 39, 40, 41. The diameter of the metal washers 27, 28 is substantially equal to that of the insulator 26. An electrically insulated screw (not shown) passes through the aligned holes in the washers 27, 28.
The container 21 consists of a central ring 50 its internal diameter permitting the button diode 20 to be inserted by applying a slight pressure, alternatively by allowing a small tolerance on the internal diameter of the central ring compared with that of the diode case. The central ring 50 is held in place by two identical parallelepiped-shaped shoulders 51, 52, one opposite the other, and of a size that enables them to enter the holes in the fins 22, 23 without appreciable play between the two dimensions of the hole. At the two ends of the shoulder 51 is a projection that delimits a groove, respectively 53 and 54, in the contiguous body of the shoulder. Similarly, the two ends of the shoulder 52 end with a projection that delimits a groove, respectively 55 and 56, in the contiguous body of the shoulder. The grooves in the one shoulder are open towards those in the other shoulder, namely towards the inside of the container 21. The fins 22, 23 are of aluminium, thickness 0.8 mm. The container 21 is a single body of thermosetting epoxy resin. The diode 20 presents no limitations, being chosen from among those available on the market possessing the necessary requisites of inverse voltage and maximum conduction current set for the specific circuits in which it is used.
The elements described reappear in Figure 7, less the washers 27, 28 to make the drawing clearer. The diode 20 is fitted into the ring 50 in the container 21 after which the ends of the shoulders 51, 52 containing the button diode 20, are fitted into the rectangular holes 29, 30 in fin 22, and into the rectangular holes 31, 32 in fin 23. Shoulder height is such that grooves 53, 54 and 55, 56 will project from the external face of respective fins 22 and 23 when the anode and cathode of diode 20 make contact with them at the strips of fin comprised between rectangular holes 29, 30 and 31, 32. At this point the ends of the flat spring 24 are fitted into the opposite grooves 53, 55 present in the upper ends of shoulders 51, 52 with the convexity in contact with the fin 22. The ends of the flat spring 25 are then fitted into the opposing grooves 54, 56 at the lower ends of shoulders 51, 52. The first flat spring 24 fits in without apparent effort while application of the second flat spring 25 requires some pressure to compress the first flat spring. At the centre, the two flat springs 24, 25 will exert pressure of between 78.4 and 98 Newton (8-10 kg) and will become almost completely flat since, as shown in Figure 7, the base of the grooves projects from the rectangular holes by about the thickness of the flat spring. The insulator 26 fits in between the two fins 22, 23 to allow the two terminal pieces, shaped as sectors of ring 33, 34 to enter the respective depressions 45. Protrusions 38, 41 prevent the terminal part 33 from moving beyond the edge of the hole 37. The figure shows that uniform thickness of fin 22 (and 23) is greater than the height of protrusions 38 and 41 thereby permitting contact with the metal washer 27 (28). The assembly thus obtained would as such be usable in systems with a single button diode, but for one including the rectifier bridge in Figure 12 it will be completed as explained in the following figure.
Figure 8 shows the section of the assembly in Figure 7 according to the radial axis in this figure. The two electrodes 62, 63 of diode 20 are held firmly against the fins 22, 23 due to compression exerted by the flat springs 24, 25 placed immediately above. In this way heat produced by the diode is conducted by the electrodes to the respective fins and, in addition, fins 22, 23 assume the polarity of the respective electrodes 62, 63 and could therefore be used directly as terminals. This solution is illustrated in Figure 7a where two male faston connectors 60, 61 can be seen at a pair of distal vertices of fins 22, 23, obtaind by simply cutting two suitably long notches and two holes aligned for each connector. The faston connectors 60, 61 make the assembly in Figure 7 highly flexible in use especially in multiple assemblies on the same insulator 26. The figure 8 shows the gap 35 between fins 22, 23 and insulator 26 that limits transfer of heat towards the latter.
Figure 9 shows a quadruple assembly DDI in which the assembly in Figure 7, here marked AS1, is repeated four times, completing all the depressions 42, 43, 44, 45 between protrusions 38, 39, 40, 41 present on the two faces of the central cylindrical insulator 26. Assembly DDI therefore consists of the four contiguous assemblies ASl, AS2, AS3, AS4 separated by four open spaces 68, 69, 70, 71 on the extension of protrusions 38, 39, 40, 41. In this figure the upper face of assembly DDI is seen with assembly ASl showing the upper fin 22 and the flat spring 24 compressed between shoulders 51, 52. Assembly AS2 shows an upper fin 65 with a flat spring 72 compressed between two shoulders 73 and 74. Assembly AS3 shows an upper fin 66 with a flat spring 75 compressed between two shoulders 76 and 77; and assembly AS4 shows an upper fin 67 with a flat spring 78 compressed between two shoulders 79 and 80.
In realizing the current rectifier in Figure 12 the two aluminium washers 27, 28 (Figure 6) lie one above the other at the ends of the fins in their seats on the insulator 26 connecting in parallel the four diodes held between the respective fins. For other purposes insulating washers can be used for mechanically constraining the fins of the four assemblies against the two faces of the central insulator 26, making the various diodes independent. In that case faston connections made on the fins can be used.
Figure 10 shows an elevation of the quadruple assembly DDI viewed from the left hand side of this figure. As the DDI assembly is perfectly symmetrical, this view is the same for all equivalent positions. This is an extended view of assembly ASl and partly of adjacent assemblies, AS4 to the right and AS2 to the left seprated by open gaps 71 and 68. In assembly ASl button diode 20 appears with its case fitted into the ring-wise seat 50 of its container, the anode and cathode being in contact either with fin 22 or with fin 23, pressed against the electrodes by the upper flat spring 24 and by a lower flat spring 83 held by the grooves in the opposing shoulders 51, 52 that project from the fins. Assembly AS4 shows a button diode 81 with its case fitted into a ringwise seat of a relative container, and also its height above the two fins. Similarly assembly AS2 shows a button diode 82 with the case fitted into a circular seat of a relative container.
Figure 11 gives details of the plan view in Figure 9 also showing the lower fins of the four assemblies and the side of the insulator 26. In particolar, in assembly ASl, fin 22 lies above a fin 23; in assembly AS2 fin 65 lies above a fin 83; in assembly AS3 fin 66 lies above a fin 84; in assembly AS4 fin 67 lies above a fin 85.
Figure 12 shows a diode current-rectifier circuit equivalent to the three-phase Graetz bridge in Figure 1, if single diodes Dl, D2, D3, D4, D5, D6 are replaced with the parallel of four diodes from each assembly ASl, AS2, AS3, AS4.
A realization of the current rectifier in Figure 12 is shown in Figure 13 with a pile of quadruple assemblies identical to assembly DDI in Figure 11. In the following order from the top downwards, the pile of elements includes: quadruple assemblies DDI, DD2, DD3, DD4, DD5, DD6 connected as shown in Figure 12 by phase contact terminals FF1, FF2, FF3 and U-shaped terminals VV+ and VV- for positive and negative polarity contacts. The pile of quadruple assemblies including terminals is tightened by a central screw 90 that passes through the central hole 37 of all the insulators 26, of all the aluminium washers 27, 28 and interposed terminals. Screw 90 is kept electrically insulated by the walls of the holes through which it passes, as also by the tightening walls with insulating washers as will be better explained in the next figure.
Figure 14 is a cross section of the pile in Figure 13 along a longitudinal plane of symmetry. The screw 90 passes through the pile and emerges at the two ends where it is bolted by two nuts, 91a, 91b, two washers 92a, 92b, and two insulating washers 93a, 93b. The screw 90 is inserted in an insulating cylinder ensuring permanent electrical insulation. An insulating screw can be used as an alternative. The figure shows that pierced terminals FF1, FF2, FF3, VV+ and VV- are connected by inserting them between adjacent metal washers. More generally, for M phases there will be 2M multiple assemblies, M phase terminals and M - 1 terminals for each polarity of rectified current. Each multiple assembly includes N button diodes making a total of 2MxN diodes. Figure 14 shows a realization of the invention in all its compactness, modular structure and efficacy making clear its capacity to control strong current while employing button dioides of submultiple amperage; these can be used at values closer to the maximum permetted thanks to the efficacy of bifacial cooling.
Based on the description given of a preferred example of realization of the invention, some changes can obviously be made by a specialist in the field without thereby departing from its sphere as will appear from the following claims. One possible minimum variation is to have circular holes in the fins for insertion of cylindrical shoulders that have transversal grooves at the two ends. Another possible variation is that in which each protrusion consists of a trapezoidal tooth placed at the end of a shank in the body of the shoulder through the hole in the fin. In this case the flat spring can have a small notch at each end to accommodate the shank while the base of the tooth presses against the fin.

Claims

Claims
1. Assembly for thermal dissipation and for electrically connecting current-rectifier button diodes (20),
characterized in that for at least one power diode the assembly includes:
- two rigid shoulders (51, 52) of insulating material (21) to fit onto the diametrically opposite sides of the case (64) of the diode (20) there being at the two ends of each one a protrusion facing towards a similar protrusion on the opposite shoulder;
- two metal fins (22, 23) each having two holes (29, 30, 31, 32) equally spaced in the two fins for insertion of respective ends of the two shoulders
(51, 52), said protrusions extending beyond the external face of the fins, and said fins being in contact with respective electrodes (62, 63) on the button diode (20);
- resilient means (24, 25) placed between said protrusions and respective fins for exerting pressure on the fins to maintain their close contact with said electrodes (62, 63).
2. Assembly as in claim 1, characterized in that said two shoulders (51, 52) can be fitted onto the case (64) by an element (50) made of the same insulating material (21) mounted between them, said element being designed to accept insertion of the diode (20).
3. Assembly as in claim 1, characterized in that said two shoulders (51, 52) form an integral part of the diode case (64).
4. Assembly as in claim 1, characterized in that said holes (29, 30; 31, 32) are rectangular to take parallelepiped-shaped shoulders (51, 52) that fit into the holes without appreciable play.
5. Assembly as in claim 1, characterized in that said protrusion delimits a transversal groove (53, 54; 55, 56) in the contiguous body of the shoulder (51 , 52) open towards an opposite groove to receive a respective end of a flat spring (24, 25).
6. Assembly as in claim 1, characterized in that it further includes:
- an insulator (26) with a central hole and two opposite flat faces and at least one depression (42, 43, 44, 45) in each flat face, the insulator being inserted between the two fins (22, 23) at a vertex (33, 34) of said fins, said vertex fitting into a respective depression;
- a washer (27, 28) for each flat face of the insulator (26), resting on that part of the fin that rises above the edge of the depression;
- means (90, 91a, 91b) for fixing the washers onto the fins, said means (90) crossing the insulator (26), and pressing against the two washers (27, 28).
7. Assembly as in claim 6, characterized in that there is a slit (35, 36) in the fins (22, 23) set at a distance from the vertex greater than the depth of the depression in the insulator (26) so limiting heat transfer towards said insulator.
8. Assembly as in claim 6, characterized in that the assembly (DDI) for
N button diodes also includes:
- N identical assemblies (AS1, AS2, AS3, AS4) per power diode, in each unitary assembly said vertex of the respective fins subtending an angle of 2π/Ν radian and is cut off;
- the insulator (26) is ring-shaped and has N symmetrical depressions (42, 43, 44, 45) to contain an equivalent number of fin parts (22, 23; 65, 83; 66, 84; 67, 85) at the respective cut-off vertices, said fin parts being electrically insulated one from another by protrusions (38, 39, 40, 41) that delimit adjacent depressions.
9. Assembly as in claim 8, characterized in that said washers (27, 28) are made of metal and connect the N diodes in parallel.
10. Assembly as in claim 6, characterized in that said washers (27, 28) are insulating.
11. Assembly as in claim 1, characterized in that faston male connectors (60, 61) are formed by notches cut in the edge of the fins (22, 23).
12. Assembly as in claim 8, characterized in that the fins are shaped like circular sectors and the cut-off vertex like an identical angular part of a ring.
13. Assembly as in claim 8, characterized in that the fins are square in shape by N = 4.
14. Assembly as in claim 9, characterized in that the assembly for full-wave M-phase current rectifier circuits includes: - 2M identical assemblies (DDI, DD2, DD3, DD4, DD5, DD6) for N button diodes (AS1, AS2, AS3, AS4) one above another to form a pile;
- M input terminals of the phases and M-l output terminals for each of the two polarities of rectified current, said terminals being bored at one end between adjacent washers;
- a long screw (90, 91a, 91b) passed through the centre of the pile, electrically insulated (93 a, 93 b) against the conductors through which the screw passes.
15. Button diode for the assembly as in claim 1, characterized in that the diode case has two rigid shoulders forming part of the case itself, the two shoulders standing on diametrically opposite sides of the case, each shoulder having two ends that extend beyond respective electrodes of the diode, each end having a protrusion facing towards the protrusion on the opposite shoulder.
PCT/IT2010/000525 2010-12-22 2010-12-30 Assembly for the heat dissipation and the electrical connection of current-rectifier button diodes Ceased WO2012085952A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI2010A002350 2010-12-22
ITMI2010A002350A IT1403604B1 (en) 2010-12-22 2010-12-22 ASSEMBLY FOR THERMAL DISSIPATION AND ELECTRICAL CONNECTION OF CURRENT RECTIFYING BUTTON DIODES

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WO2012085952A1 true WO2012085952A1 (en) 2012-06-28

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Cited By (1)

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CN104981901A (en) * 2012-12-07 2015-10-14 Abb技术有限公司 Semiconductor assembly

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US3619473A (en) * 1968-01-26 1971-11-09 Westinghouse Electric Corp Clamping bracket for flat package semiconductor devices and a semiconductor assembly utilizing the same
US6528911B1 (en) * 1998-10-07 2003-03-04 Electro-Dyn Electronics Corporation Rectifier assembly for automotive alternators

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3619473A (en) * 1968-01-26 1971-11-09 Westinghouse Electric Corp Clamping bracket for flat package semiconductor devices and a semiconductor assembly utilizing the same
US6528911B1 (en) * 1998-10-07 2003-03-04 Electro-Dyn Electronics Corporation Rectifier assembly for automotive alternators

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104981901A (en) * 2012-12-07 2015-10-14 Abb技术有限公司 Semiconductor assembly
JP2016500474A (en) * 2012-12-07 2016-01-12 エービービー テクノロジー エルティーディー． Semiconductor assembly
CN104981901B (en) * 2012-12-07 2018-05-15 Abb 技术有限公司 Semiconductor subassembly
US9984953B2 (en) 2012-12-07 2018-05-29 Abb Schweiz Ag Semiconductor assembly having a press pack stack
EP2929562B1 (en) * 2012-12-07 2021-04-28 ABB Power Grids Switzerland AG Semiconductor assembly

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IT1403604B1 (en) 2013-10-31

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