WO2016185148A1 - Method for welding without filler material and electronic power module produced by this method - Google Patents

Method for welding without filler material and electronic power module produced by this method Download PDF

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Publication number
WO2016185148A1
WO2016185148A1 PCT/FR2016/051201 FR2016051201W WO2016185148A1 WO 2016185148 A1 WO2016185148 A1 WO 2016185148A1 FR 2016051201 W FR2016051201 W FR 2016051201W WO 2016185148 A1 WO2016185148 A1 WO 2016185148A1
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WO
WIPO (PCT)
Prior art keywords
welding
laser beam
substrate
power module
directed
Prior art date
Application number
PCT/FR2016/051201
Other languages
French (fr)
Inventor
Jean-Michel Morelle
Ky Lim Tan
Laurent Vivet
Anthony Brisset
Original Assignee
Valeo Equipements Electriques Moteur
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Application filed by Valeo Equipements Electriques Moteur filed Critical Valeo Equipements Electriques Moteur
Publication of WO2016185148A1 publication Critical patent/WO2016185148A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/21—Bonding by welding
    • B23K26/22—Spot welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/21—Bonding by welding
    • B23K26/24—Seam welding
    • B23K26/244—Overlap seam welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/32—Bonding taking account of the properties of the material involved
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/36—Electric or electronic devices

Definitions

  • the present invention relates to a welding process without adding material for the realization of the interconnections of an electronic power module.
  • the new generations of electronic power modules require high compactness and power density.
  • the electrical connections to the power semiconductors are carried out by the conductive tracks of the DBC substrates (acronym for "Direct Bonded Copper” in English terminology, which means copper and a ceramic material directly connected), DBA (acronym for "Direct Bonded Aluminum “), and AMB (acronym for” Active Metal Brazing “, which refers to a brazed ceramic substrate).
  • These tracks are connected to the terminals of the belt of the housing by various processes using son or aluminum strips whose ends are welded by ultrasound, or using welded connections with material supply, connections made by resistive welding ( electrical welding), or spring blade connections.
  • solder particularly lead-free solder
  • Solders used for power applications at high operating temperatures contain lead, but their use is limited by a European directive (RoHS).
  • RoHS European directive
  • the ultrasonic welding of a terminal on the substrate that is used by some manufacturers eliminates the supply of material soldering.
  • the ultrasonically welded joint can withstand the stresses associated with the high operating temperature.
  • the brazed joint that is sensitive to stress thermomechanical due to the difference in coefficient of thermal expansion (CDT)
  • the Cu - Cu bond produced by ultrasound undergoes neither plastic deformation nor fatigue in operation.
  • this ultrasonic welding process which requires applying a high mechanical force on the surface to be welded sometimes leads to damage to the ceramic substrate DBC, AMB or DBA .
  • an ultrasonic weld is a weld surface very sensitive to the surface condition of the substrate (oxide, pollution), and generally requires cleaning after the brazing operation of the semiconductors to remove any trace of organic residue, such as solder flux residues.
  • Ultrasonic welding is also known to be very sensitive to the presence of vacuum between the layers that make up the structure of the substrate.
  • Soldering processes without brazing are also known.
  • the company VALEO ELECTRONIQUE AND SYSTEMES DE LIAISON describes a soldering process without adding material for connecting an electrical component, provided with at least one electrical connection pin, with a substrate.
  • the present invention therefore aims to overcome the disadvantages of electrical interconnection methods known for producing electronic power modules.
  • It relates to a material-free soldering process for interconnecting first and second elements made of metallic materials of the type in which: a second welding element of the second element connected by a fold to a support part of this first element is brought into contact with the first element;
  • a laser beam is directed on the welding part so as to locally cause a melting of the materials.
  • the first element is a conductive track of a power module formed on a plane substrate
  • the second element is a connection terminal of the power module
  • the laser beam is directed on the welding part perpendicularly to the substrate.
  • the laser beam forms a continuous weld seam of a predetermined pattern.
  • the laser beam forms a succession of soldering points of a predetermined pattern.
  • this pattern consists of substantially parallel or zigzag lines.
  • a plating mask advantageously maintains the connection terminal against the conductive track.
  • the connecting terminal is made of aluminum or copper coated with nickel.
  • the substrate is of the DBC, AMB or DBA type.
  • the laser beam is directed by fast galvanic mirrors.
  • This laser beam is advantageously generated by an Nd: YAG type laser having a peak power of several kilowatts.
  • the invention also relates to an electronic power module of the type comprising a substrate and at least one connecting terminal.
  • this connection terminal is welded to the substrate by the soldering method without the addition of material described above.
  • Figure 1 shows an electronic module of power in progress by the soldering process without adding material according to the invention.
  • Figure 2 is a sectional view of the power electronics module shown in Figure 1.
  • FIGS. 3a and 3b show, in plan view, weld points, in parallel and zigzag lines, respectively, of connection terminals of the power electronic module shown in FIG. 1.
  • the welding method according to the invention is applicable to a power module 1, such as that shown in Figure 1, using DBC, AMB or DBA substrate technologies.
  • These substrates 2, 3 comprise, as shown in the section of FIG. 2 (cross section along a section line AA), on one face of a ceramic plate 2, such as alumina, a layer of copper or aluminum 3 which can be etched (or not) to form conductive tracks 3 isolated from each other.
  • a ceramic plate 2 such as alumina
  • a layer of copper or aluminum 3 which can be etched (or not) to form conductive tracks 3 isolated from each other.
  • the power module 1 comprises the substrate 2, 3, soldered power semiconductors on this substrate 2, 3 control and power terminals 4 inserted or molded in a plastic belt 5.
  • the proposed invention consists in using an autogenous welding method by means of a laser beam 7 (continuous or in points) for welding a welding part 8 of a power or signal terminal 4, called a terminal of connection 4, including a support portion 9 is integral with the belt 5, on the copper or aluminum layer 3 of a substrate DBC, AMB or DBA.
  • This nickel coating is not necessary in the case of an aluminum connection terminal 4.
  • a plating mask 10 makes it possible to keep the welding part 8 connected by a fold 1 1 in contact with the support part 9 of the connection terminal 4 and the conductive track 3 of the substrate 2, 3, and protects during the welding operation the electronic components already assembled on the substrate 2, 3 of the diffuse reflection of the incident laser beam 7 by the surface as well as possible projections of metal.
  • the welding parameters are adjusted to ensure a good quality of welding.
  • the very high stability of Nd: YAG type (yttrium-aluminum-doped neodymium-garnet) solid state lasers allows excellent control of the penetration depth of a welded joint 12 in the copper or aluminum layer 3 of the substrate 2, 3, and guarantees the integrity of the underlying ceramic layer 2.
  • the high speed of realization of the welds limits the extent of the heat affected zone around the weld to a few tens of ⁇ , which contributes to respect the integrity of the structure of the substrate 2, 3.
  • Laser welding heads using fast galvanometric mirrors make it possible to weld through openings 13 of the mask 10 according to different predetermined patterns 14, 15 as shown in FIGS. 3a and 3b.
  • a pattern of a continuous weld seam, or a succession of weld points 14, 15, is executed without moving parts to be welded 3, 4. It can be easily adapted to the geometry of each of the assemblies 3, 4 to achieve and the surface of the welded joint 12 desired.
  • a small diameter of the laser beam 7 (typically 400 ⁇ m) at the focal point 12 allows great fineness in the resolution of the solder patterns.
  • the welding points 14, 15 are made by laser pulses, of square temporal profile, for a peak power of several kW and an irradiation duration of several ms.
  • the welded joint 12 produced passes through the thickness of the welding part 8 of the connection terminals 4 and penetrates into the copper layer 3 of the substrate 2, 3, without reaching the ceramic layer 2.
  • Two galvanometric mirrors (not shown) move the position of the laser beam 7 laterally and longitudinally before it is focused by an output optic, which allows the realization of the weld bead with a very high precision without movement of the parts 3, 4 to assemble.
  • FIG. 3a shows a succession of soldering points 14 distributed along two parallel lines 14 in a width of the connection terminal 4.
  • solder points 15 form a zigzag pattern 15.
  • the interconnections thus made can have the capacity to convey high currents. They resist strong thermomechanical stresses and they make it possible to avoid damage to the constituents of the power module 1.
  • a copper-copper seal 12 makes it possible to withstand considerably the thermomechanical stress during operation, initially and after prolonged aging.

Abstract

The method according to the invention concerns welding without filler material in order to link together first and second elements (3, 4) made from metal materials, and involves bringing a welding part (8) of the second element (4) linked by a fold (11) to a support part (9) of the second element (4) into contact with the first element (3), and directing a laser beam (7) on the welding part in such a way as to cause the materials to melt locally. In the present application, the first element (3) is a conductive track of a power module (1) formed on a flat substrate (2, 3), the second element (4) is a connection terminal of the power module (1), and the laser beam (7) is directed on the welding part perpendicularly to the substrate (2, 3).

Description

PROCEDE DE SOUDURE SANS APPORT DE MATIERE ET MODULE ELECTRONIQUE DE PUISSANCE REALISE PAR CE PROCEDE  WELDING PROCESS WITHOUT CONTENT OF MATERIAL AND ELECTRONIC POWER MODULE MADE THEREBY
DOMAINE TECHNIQUE DE L'INVENTION. TECHNICAL FIELD OF THE INVENTION
La présente invention concerne un procédé de soudure sans apport de matière pour la réalisation des interconnexions d'un module électronique de puissance.  The present invention relates to a welding process without adding material for the realization of the interconnections of an electronic power module.
ARRIERE PLAN TECHNOLOGIQUE DE L'INVENTION. BACKGROUND ART OF THE INVENTION.
Les nouvelles générations de modules électroniques de puissance exigent une compacité et une densité de puissance élevées. Les liaisons électriques vers les semi-conducteurs de puissance sont réalisées par les pistes conductrices des substrats DBC (acronyme de "Direct Bonded Copper" en terminologie anglaise, ce qui désigne du cuivre et un matériau céramique directement liés), DBA (acronyme de "Direct Bonded Aluminium"), et AMB (acronyme de "Active Métal Brazing", qui désigne un substrat céramique brasé). Ces pistes sont connectées aux terminaux de la ceinture du boîtier par différents procédés utilisant des fils ou rubans d'aluminium dont les extrémités sont soudés par ultrasons, ou bien mettant en œuvre des liaisons soudées avec apport de matière, des liaisons réalisées par soudure résistive (soudure électrique), ou encore des liaisons par lame ressort.  The new generations of electronic power modules require high compactness and power density. The electrical connections to the power semiconductors are carried out by the conductive tracks of the DBC substrates (acronym for "Direct Bonded Copper" in English terminology, which means copper and a ceramic material directly connected), DBA (acronym for "Direct Bonded Aluminum "), and AMB (acronym for" Active Metal Brazing ", which refers to a brazed ceramic substrate). These tracks are connected to the terminals of the belt of the housing by various processes using son or aluminum strips whose ends are welded by ultrasound, or using welded connections with material supply, connections made by resistive welding ( electrical welding), or spring blade connections.
Tous ces procédés présentent des avantages et des inconvénients.  All of these methods have advantages and disadvantages.
L'interconnexion utilisant une brasure, en particulier une brasure sans plomb, est la plus simple et la plus couramment utilisée. Mais elle ne permet pas de fonctionner à température élevée.  The interconnection using solder, particularly lead-free solder, is the simplest and most commonly used. But it does not work at high temperatures.
Les brasures utilisées pour les applications de puissance à des températures de fonctionnement élevées contiennent du plomb, mais leur utilisation est limitée par une directive européenne (RoHS).  Solders used for power applications at high operating temperatures contain lead, but their use is limited by a European directive (RoHS).
De plus, les caractéristiques thermiques et électriques de ces brasures à l'initial et après vieillissement sont limitées par l'alliage du joint brasé sélectionné. A part les alliages d'or, les brasures sans plomb ne sont pas stables  In addition, the thermal and electrical characteristics of these solders at the initial and after aging are limited by the alloy of the selected soldered joint. In addition to gold alloys, lead-free solders are not stable
La soudure par ultrason d'un terminal sur le substrat qui est utilisée par certains fabricants permet d'éliminer l'apport de matière du brasage. Le joint soudé par ultrason peut résister aux contraintes liées à la température de fonctionnement élevée. Et, contrairement, au joint brasé qui est sensible aux contraintes thermomécaniques dues à la différence de coefficient de dilatation thermique (CDT), la liaison Cu - Cu réalisée par ultrason ne subit ni de déformation plastique, ni de fatigue en fonctionnement. Cependant, ce procédé de soudure par ultrason qui nécessite d'appliquer un effort mécanique élevé sur la surface à souder conduit parfois à l'endommagement de la céramique du substrat DBC, AMB ou DBA.. De plus, une soudure par ultrason est une soudure superficielle très sensible à l'état de surface du substrat (oxyde, pollution), et nécessite généralement un nettoyage après l'opération de brasage des semi-conducteurs pour éliminer toute trace de résidu organique, comme les résidus de flux de brasage. The ultrasonic welding of a terminal on the substrate that is used by some manufacturers eliminates the supply of material soldering. The ultrasonically welded joint can withstand the stresses associated with the high operating temperature. And, unlike the brazed joint that is sensitive to stress thermomechanical due to the difference in coefficient of thermal expansion (CDT), the Cu - Cu bond produced by ultrasound undergoes neither plastic deformation nor fatigue in operation. However, this ultrasonic welding process which requires applying a high mechanical force on the surface to be welded sometimes leads to damage to the ceramic substrate DBC, AMB or DBA .. In addition, an ultrasonic weld is a weld surface very sensitive to the surface condition of the substrate (oxide, pollution), and generally requires cleaning after the brazing operation of the semiconductors to remove any trace of organic residue, such as solder flux residues.
La soudure ultrason est aussi connue pour être très sensible à la présence de vide entre les couches qui composent la structure du substrat.  Ultrasonic welding is also known to be very sensitive to the presence of vacuum between the layers that make up the structure of the substrate.
L'interconnexion réalisée par des ressorts de contact a de bonnes caractéristiques électriques et thermiques. Mais le mécanisme de maintien en pression des terminaux ressorts est plus compliqué, car il nécessite un nombre important de pièces additionnelles.  The interconnection made by contact springs has good electrical and thermal characteristics. But the pressure holding mechanism of the spring terminals is more complicated because it requires a large number of additional parts.
On connaît également des procédés de soudure sans brasure. Par exemple, dans la demande de brevet français FR2877865, la société VALEO ELECTRONIQUE ET SYSTEMES DE LIAISON décrit un procédé de soudure sans apport de matière permettant de connecter un composant électrique, muni d'au moins une broche de raccordement électrique, avec un substrat. Un faisceau laser dirigé dans l'axe d'une patte de support, brasée sur le substrat et en contact avec cette broche, provoque une fusion en masse de la patte est assure la connexion de la broche.  Soldering processes without brazing are also known. For example, in the French patent application FR2877865, the company VALEO ELECTRONIQUE AND SYSTEMES DE LIAISON describes a soldering process without adding material for connecting an electrical component, provided with at least one electrical connection pin, with a substrate. A laser beam directed in the axis of a support leg, brazed to the substrate and in contact with this pin, causes a mass melting of the leg is ensures the connection of the pin.
Mais un tel procédé ne convient pas non plus à la connexion des terminaux aux pistes des substrats, car la fusion en masse des terminaux endommagerait ces pistes.  However, such a method is not suitable for connecting the terminals to the tracks of the substrates, because the mass melting of the terminals would damage these tracks.
DESCRIPTION GENERALE DE L'INVENTION. GENERAL DESCRIPTION OF THE INVENTION
La présente invention vise donc à pallier les inconvénients des procédés d'interconnexion électriques connus pour la réalisation de modules électroniques de puissance.  The present invention therefore aims to overcome the disadvantages of electrical interconnection methods known for producing electronic power modules.
Elle concerne un procédé de soudure sans apport de matière destiné à relier entre eux des premier et second éléments en matériaux métalliques du type dans lequel: - on met en contact avec le premier élément une partie de soudage du second élément reliée par un pli à une partie de support de ce premier élément; It relates to a material-free soldering process for interconnecting first and second elements made of metallic materials of the type in which: a second welding element of the second element connected by a fold to a support part of this first element is brought into contact with the first element;
- on dirige sur la partie de soudage un faisceau laser de façon à provoquer localement une fusion des matériaux.  a laser beam is directed on the welding part so as to locally cause a melting of the materials.
Dans le procédé selon l'invention:  In the process according to the invention:
- le premier élément est une piste conductrice d'un module de puissance formée sur un substrat plan;  the first element is a conductive track of a power module formed on a plane substrate;
- le second élément est un terminal de raccordement du module de puissance; the second element is a connection terminal of the power module;
- le faisceau laser est dirigé sur la partie de soudage perpendiculairement au substrat. the laser beam is directed on the welding part perpendicularly to the substrate.
Dans un mode de réalisation de l'invention, le faisceau laser forme un cordon de soudure continu d'un motif prédéterminé.  In one embodiment of the invention, the laser beam forms a continuous weld seam of a predetermined pattern.
Dans un autre mode de réalisation de l'invention, le faisceau laser forme une succession de points de soudure d'un motif prédéterminé.  In another embodiment of the invention, the laser beam forms a succession of soldering points of a predetermined pattern.
Selon l'invention, dans l'un ou l'autre mode de réalisation, ce motif est constitué de lignes sensiblement parallèles ou en zigzag.  According to the invention, in one or the other embodiment, this pattern consists of substantially parallel or zigzag lines.
Selon le procédé de l'invention, un masque de plaquage maintient avantageusement le terminal de raccordement contre la piste conductrice.  According to the method of the invention, a plating mask advantageously maintains the connection terminal against the conductive track.
Dans le procédé selon l'invention, le terminal de raccordement est constitué d'aluminium ou de cuivre revêtu de nickel.  In the method according to the invention, the connecting terminal is made of aluminum or copper coated with nickel.
Dans le procédé selon l'invention encore, le substrat est de type DBC, AMB ou DBA.  In the process according to the invention, the substrate is of the DBC, AMB or DBA type.
De préférence, selon l'invention, le faisceau laser est dirigé par des miroirs galvaniques rapides.  Preferably, according to the invention, the laser beam is directed by fast galvanic mirrors.
Ce faisceau laser est généré avantageusement par un laser de type Nd:YAG d'une puissance de crête de plusieurs kilowatts.  This laser beam is advantageously generated by an Nd: YAG type laser having a peak power of several kilowatts.
L'invention concerne également un module électronique de puissance du type comprenant un substrat et au moins un terminal de raccordement.  The invention also relates to an electronic power module of the type comprising a substrate and at least one connecting terminal.
Dans le module électronique de puissance selon l'invention, ce terminal de raccordement est soudé sur le substrat par le procédé de soudure sans apport de matière décrit ci-dessus.  In the power electronic module according to the invention, this connection terminal is welded to the substrate by the soldering method without the addition of material described above.
Ces quelques spécifications essentielles auront rendu évidents pour l'homme de métier les avantages apportés par le procédé de soudure sans apport de matière, et par le module électronique de puissance réalisé par ce procédé, par rapport à l'état de la technique antérieur. These few essential specifications will have made obvious to the skilled person the advantages brought by the soldering process without input of material, and by the electronic power module produced by this method, compared to the state of the prior art.
Les spécifications détaillées de l'invention sont données dans la description qui suit en liaison avec les dessins ci-annexés. Il est à noter que ces dessins n'ont d'autre but que d'illustrer le texte de la description et ne constituent en aucune sorte une limitation de la portée de l'invention.  The detailed specifications of the invention are given in the following description in conjunction with the accompanying drawings. It should be noted that these drawings have no other purpose than to illustrate the text of the description and do not constitute in any way a limitation of the scope of the invention.
BREVE DESCRIPTION DES DESSINS. BRIEF DESCRIPTION OF THE DRAWINGS
La Figure 1 montre un module électronique de puissance en cours de réalisation par le procédé de soudure sans apport de matière selon l'invention.  Figure 1 shows an electronic module of power in progress by the soldering process without adding material according to the invention.
La Figure 2 est une vue en coupe du module électronique de puissance montré sur la Figure 1.  Figure 2 is a sectional view of the power electronics module shown in Figure 1.
Les Figures 3a et 3b montrent en vue de dessus des points de soudure, respectivement en lignes parallèles et en zigzag, de terminaux de raccordement du module électronique de puissance montré sur la Figure 1.  FIGS. 3a and 3b show, in plan view, weld points, in parallel and zigzag lines, respectively, of connection terminals of the power electronic module shown in FIG. 1.
DESCRIPTION DES MODES DE REALISATION PREFERES DE L'INVENTION. DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
Le procédé de soudure selon l'invention est applicable à un module de puissance 1 , tel que celui montré sur la Figure 1 , utilisant les technologies de substrats DBC, AMB ou DBA.  The welding method according to the invention is applicable to a power module 1, such as that shown in Figure 1, using DBC, AMB or DBA substrate technologies.
Ces substrats 2, 3 comportent, comme le montre la coupe de la Figure 2 (coupe transversale selon une ligne de coupe A-A), sur une face d'une plaque de céramique 2, telle que de l'alumine, une couche de cuivre ou d'aluminium 3 qui peut être gravée (ou non) pour former des pistes conductrices 3 isolées entre elles.  These substrates 2, 3 comprise, as shown in the section of FIG. 2 (cross section along a section line AA), on one face of a ceramic plate 2, such as alumina, a layer of copper or aluminum 3 which can be etched (or not) to form conductive tracks 3 isolated from each other.
Le module de puissance 1 comprend le substrat 2, 3, des semi-conducteurs de puissance brasés sur ce substrat 2,3, des terminaux de contrôle et de puissance 4 insérés ou moulés dans une ceinture en plastique 5.  The power module 1 comprises the substrate 2, 3, soldered power semiconductors on this substrate 2, 3 control and power terminals 4 inserted or molded in a plastic belt 5.
Le substrat 2, 3, qui peut également être formé d'un empilement Cu - céramique - Cu, est brasé ou collé sur un dissipateur thermique 6.  The substrate 2, 3, which may also be formed of a Cu - ceramic - Cu stack, is brazed or bonded to a heat sink 6.
L'invention proposée consiste à utiliser un procédé de soudure autogène au moyen d'un faisceau laser 7 (continue ou par points) pour souder une partie de soudage 8 d'un terminal de puissance ou de signal 4, appelé terminal de raccordement 4, dont une partie de support 9 est solidaire de la ceinture 5, sur la couche de cuivre ou d'aluminium 3 d'un substrat DBC, AMB ou DBA. The proposed invention consists in using an autogenous welding method by means of a laser beam 7 (continuous or in points) for welding a welding part 8 of a power or signal terminal 4, called a terminal of connection 4, including a support portion 9 is integral with the belt 5, on the copper or aluminum layer 3 of a substrate DBC, AMB or DBA.
Un revêtement de métal, de préférence de nickel, est déposé sur le terminal de raccordement 4 en cuivre pour assurer un bon couplage initial entre une surface de la partie de soudage 8 du terminal de raccordement 4 et le faisceau laser 7, car le cuivre à température ambiante réfléchit le faisceau laser 7 incident à plus de 99%. Ce revêtement de nickel n'est pas nécessaire dans le cas d'un terminal de raccordement 4 en aluminium.  A coating of metal, preferably nickel, is deposited on the copper connection terminal 4 to ensure good initial coupling between a surface of the welding portion 8 of the connection terminal 4 and the laser beam 7, since the copper to ambient temperature reflects the incident laser beam 7 more than 99%. This nickel coating is not necessary in the case of an aluminum connection terminal 4.
Comme le montre bien la Figure 2, un masque de plaquage 10 permet d'assurer un maintien en contact de la partie de soudage 8 reliée par un pli 1 1 à la partie de support 9 du terminal de raccordement 4 et de la piste conductrice 3 du substrat 2, 3, et permet de protéger pendant l'opération de soudure les composants électroniques déjà assemblés sur le substrat 2, 3 de la réflexion diffuse du faisceau laser 7 incident par la surface ainsi que d'éventuelles projections de métal.  As is clearly shown in FIG. 2, a plating mask 10 makes it possible to keep the welding part 8 connected by a fold 1 1 in contact with the support part 9 of the connection terminal 4 and the conductive track 3 of the substrate 2, 3, and protects during the welding operation the electronic components already assembled on the substrate 2, 3 of the diffuse reflection of the incident laser beam 7 by the surface as well as possible projections of metal.
Les paramètres de soudure sont ajustés pour assurer une bonne qualité de soudure. La très grande stabilité des lasers à solide (en puissance, et en durée d'irradiation) de type Nd:YAG (à grenat d'yttrium- aluminium dopé au néodyme) permet un excellent contrôle de la profondeur de pénétration d'un joint soudé 12 dans la couche de cuivre ou d'aluminium 3 du substrat 2, 3, et garantit l'intégrité de la couche de céramique 2 sous-jacente. De plus la grande rapidité de réalisation des soudures (quelques ms) limite l'étendue de la zone affectée thermiquement autour de la soudure à quelques dizaines de μηη, ce qui contribue à respecter l'intégrité de la structure du substrat 2, 3.  The welding parameters are adjusted to ensure a good quality of welding. The very high stability of Nd: YAG type (yttrium-aluminum-doped neodymium-garnet) solid state lasers allows excellent control of the penetration depth of a welded joint 12 in the copper or aluminum layer 3 of the substrate 2, 3, and guarantees the integrity of the underlying ceramic layer 2. In addition, the high speed of realization of the welds (a few ms) limits the extent of the heat affected zone around the weld to a few tens of μηη, which contributes to respect the integrity of the structure of the substrate 2, 3.
Des têtes de soudures laser utilisant des miroirs galvanométriques rapides permettent de faire les soudures à travers des ouvertures 13 du masque 10 selon différents motifs 14, 15 prédéterminés comme le montrent les Figures 3a et 3b.  Laser welding heads using fast galvanometric mirrors make it possible to weld through openings 13 of the mask 10 according to different predetermined patterns 14, 15 as shown in FIGS. 3a and 3b.
Un motif d'un cordon de soudure continu, ou d'une succession de points de soudure 14, 15, est exécuté sans bouger de pièces à souder 3, 4. Il peut être adapté facilement à la géométrie de chacun des assemblages 3, 4 à réaliser ainsi qu'à la surface du joint soudé 12 désirée. Un faible diamètre du faisceau laser 7 (typiquement 400 pm) au point focal 12 permet une grande finesse dans la résolution des motifs de soudure. Les points de soudure 14, 15 sont réalisés par des impulsions laser, de profil temporel carré, pour une puissance crête de plusieurs kW et une durée d'irradiation de plusieurs ms. A pattern of a continuous weld seam, or a succession of weld points 14, 15, is executed without moving parts to be welded 3, 4. It can be easily adapted to the geometry of each of the assemblies 3, 4 to achieve and the surface of the welded joint 12 desired. A small diameter of the laser beam 7 (typically 400 μm) at the focal point 12 allows great fineness in the resolution of the solder patterns. The welding points 14, 15 are made by laser pulses, of square temporal profile, for a peak power of several kW and an irradiation duration of several ms.
Le joint soudé 12 produit traverse l'épaisseur de la partie de soudage 8 des terminaux de raccordement 4 et pénètre dans la couche de cuivre 3 du substrat 2, 3, sans atteindre la couche de céramique 2.  The welded joint 12 produced passes through the thickness of the welding part 8 of the connection terminals 4 and penetrates into the copper layer 3 of the substrate 2, 3, without reaching the ceramic layer 2.
Deux miroirs galvanométriques (non représentés) déplacent la position du faisceau laser 7 latéralement et longitudinalement avant qu'il ne soit focalisé par une optique de sortie, ce qui permet la réalisation du cordon de soudure avec une très grande précision sans mouvement des pièces 3, 4 à assembler.  Two galvanometric mirrors (not shown) move the position of the laser beam 7 laterally and longitudinally before it is focused by an output optic, which allows the realization of the weld bead with a very high precision without movement of the parts 3, 4 to assemble.
La Figure 3a montre une succession de points de soudure 14 répartis selon deux lignes parallèles 14 dans une largeur du terminal de raccordement 4.  FIG. 3a shows a succession of soldering points 14 distributed along two parallel lines 14 in a width of the connection terminal 4.
Sur la Figure 3b, les points de soudure 15 forment un motif en zigzag 15. In Figure 3b, the solder points 15 form a zigzag pattern 15.
Les interconnexions ainsi réalisées peuvent avoir la capacité de véhiculer des courants élevés. Elles résistent à de fortes contraintes thermomécaniques et elles permettent d'éviter l'endommagement des constituants du module de puissance 1 . The interconnections thus made can have the capacity to convey high currents. They resist strong thermomechanical stresses and they make it possible to avoid damage to the constituents of the power module 1.
En particulier, la formation d'un joint cuivre- cuivre 12 permet de résister considérablement à la contrainte thermomécanique en fonctionnement, ce à l'initial et après un vieillissement prolongé.  In particular, the formation of a copper-copper seal 12 makes it possible to withstand considerably the thermomechanical stress during operation, initially and after prolonged aging.
Le procédé de soudure sans apport de matière selon l'invention permet d'envisager un concept compact et simple de module de puissance 1 , et procure par conséquent un avantage certain dans le domaine très concurrentiel de l'automobile pour la réalisation d'onduleurs ou de convertisseurs embarqués dans des véhicules électriques (EV) ou hybrides (HEV).  The soldering process without the addition of material according to the invention makes it possible to envisage a compact and simple concept of power module 1, and consequently provides a definite advantage in the highly competitive field of the automobile for the production of inverters or converters embedded in electric vehicles (EV) or hybrids (HEV).
Comme il va de soi, l'invention ne se limite pas aux seuls modes d'exécution préférentiels décrits ci-dessus.  It goes without saying that the invention is not limited to the only preferred embodiments described above.
La description ci-dessus décrit une technologie d'interconnexion entre les pistes conductrices 3 d'un substrat 2, 3 de types DBC, AMB ou DBA et les terminaux de raccordement 4 d'un module de puissance 1 . Une description similaire pourrait porter sur la mise en œuvre du procédé selon l'invention dans des fabrications utilisant d'autres types de substrats, notamment des substrats à couches minces. L'invention embrasse donc toutes les variantes possibles de réalisation, dans la mesure où elles ne sortent pas du cadre fixé par les revendications ci- après. The above description describes an interconnection technology between the conductive tracks 3 of a substrate 2, 3 of types DBC, AMB or DBA and the connection terminals 4 of a power module 1. A similar description could relate to the implementation of the method according to the invention in manufacturing using other types of substrates, especially thin-film substrates. The invention therefore embraces all the possible variants of embodiment, insofar as they do not go beyond the scope set forth in the claims hereinafter.

Claims

REVENDICATIONS
1) Procédé de soudure sans apport de matière destiné à relier entre eux des premier et second éléments (3, 4) en matériaux métalliques du type dans lequel: - on met en contact avec ledit premier élément (3) une partie de soudage (8) dudit second élément (4) reliée par un pli (1 1 ) à une partie de support (9) dudit second élément (4); 1) A welding process without adding material for connecting together first and second elements (3, 4) of metal materials of the type in which: - a welding part (8) is brought into contact with said first element (3); ) said second member (4) connected by a fold (1 1) to a support portion (9) of said second member (4);
- on dirige sur ladite partie de soudage (8) un faisceau laser (7) de façon à provoquer localement une fusion desdits matériaux;  a laser beam (7) is directed on said welding portion (8) so as to locally cause a melting of said materials;
caractérisé en ce que: characterized in that
- ledit premier élément (3) est une piste conductrice d'un module de puissance (1 ) formée sur un substrat plan (2, 3) ;  said first element (3) is a conductive track of a power module (1) formed on a plane substrate (2, 3);
- ledit second élément (4) est un terminal de raccordement (4) dudit module de puissance (1 );  said second element (4) is a connection terminal (4) of said power module (1);
- ledit faisceau laser (7) est dirigé sur ladite partie de soudage (8) perpendiculairement audit substrat (2, 3). said laser beam (7) is directed on said welding portion (8) perpendicular to said substrate (2, 3).
2) Procédé de soudure sans apport de matière selon la revendication 1 précédente, caractérisé en ce que ledit faisceau laser (7) forme un cordon de soudure continu d'un motif prédéterminé. 2) soldering method without material supply according to claim 1, characterized in that said laser beam (7) forms a continuous weld seam of a predetermined pattern.
3) Procédé de soudure sans apport de matière selon la revendication 1 précédente, caractérisé en ce que ledit faisceau laser (7) forme une succession de points de soudure (14, 15) d'un motif prédéterminé. 3) soldering method without material supply according to claim 1, characterized in that said laser beam (7) forms a succession of solder points (14, 15) of a predetermined pattern.
4) Procédé de soudure sans apport de matière selon la revendication 2 ou 3 précédente, caractérisé en ce que ledit motif est constitué de lignes sensiblement parallèles (14) ou en zigzag (15). 5) Procédé de soudure sans apport de matière selon l'une quelconque des revendications 1 à 4 précédentes, caractérisé en ce qu'un masque de plaquage (10) maintient ledit terminal de raccordement (4) contre ladite piste (3). 6) Procédé de soudure sans apport de matière selon l'une quelconque des revendications 1 à 5 précédentes, caractérisé en ce que ledit terminal de raccordement (4) est constitué d'aluminium ou de cuivre recouvert d'un revêtement de nickel. 4) welding process without material intake according to claim 2 or 3 preceding, characterized in that said pattern consists of substantially parallel lines (14) or zigzag (15). 5) Process for welding without adding material according to any one of claims 1 to 4 above, characterized in that a plating mask (10) maintains said connecting terminal (4) against said track (3). 6) soldering process without material intake according to any one of claims 1 to 5, characterized in that said connecting terminal (4) is made of aluminum or copper coated with a nickel coating.
7) Procédé de soudure sans apport de matière selon l'une quelconque des revendications 1 à 6 précédentes, caractérisé en ce que ledit substrat (2, 3) est de type DBC, AMB ou DBA. 8) Procédé de soudure sans apport de matière selon l'une quelconque des revendications 1 à 7 précédentes, caractérisé en ce que ledit faisceau laser (7) est dirigé par des miroirs galvaniques rapides. 7) welding process without material intake according to any one of claims 1 to 6 above, characterized in that said substrate (2, 3) is of type DBC, AMB or DBA. 8) soldering process without material intake according to any one of claims 1 to 7, characterized in that said laser beam (7) is directed by fast galvanic mirrors.
9) Procédé de soudure sans apport de matière selon l'une quelconque des revendications 1 à 8 précédentes, caractérisé en ce que ledit faisceau laser (7) est généré par un laser de type Nd:YAG d'une puissance de crête de plusieurs kilowatts. 9) solderless process material according to any one of claims 1 to 8, characterized in that said laser beam (7) is generated by a Nd: YAG type laser with a peak power of several kilowatts .
10) Module électronique de puissance (1 ) du type comprenant un substrat (2, 3) et au moins un terminal de raccordement (4), caractérisé en ce que ledit terminal de raccordement (4) est soudé sur ledit substrat (2, 3) par le procédé de soudure sans apport de matière selon l'une quelconque des revendications 1 à 9 précédentes. 10) electronic power module (1) of the type comprising a substrate (2, 3) and at least one connecting terminal (4), characterized in that said connection terminal (4) is welded to said substrate (2, 3); ) by the non-material welding process according to any one of the preceding claims 1 to 9.
PCT/FR2016/051201 2015-05-21 2016-05-20 Method for welding without filler material and electronic power module produced by this method WO2016185148A1 (en)

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FR1554565A FR3036303B1 (en) 2015-05-21 2015-05-21 WELDING PROCESS WITHOUT CONTENT OF MATERIAL AND ELECTRONIC POWER MODULE MADE THEREBY
FR1554565 2015-05-21

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JP2008212977A (en) * 2007-03-05 2008-09-18 Fuji Electric Device Technology Co Ltd Laser welding member and semiconductor device using the same
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JP2008212977A (en) * 2007-03-05 2008-09-18 Fuji Electric Device Technology Co Ltd Laser welding member and semiconductor device using the same
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