WO2006045968A1 - Monolithic multilayer structure for the connection of semiconductor cells - Google Patents

Monolithic multilayer structure for the connection of semiconductor cells Download PDF

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Publication number
WO2006045968A1
WO2006045968A1 PCT/FR2005/050814 FR2005050814W WO2006045968A1 WO 2006045968 A1 WO2006045968 A1 WO 2006045968A1 FR 2005050814 W FR2005050814 W FR 2005050814W WO 2006045968 A1 WO2006045968 A1 WO 2006045968A1
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WO
WIPO (PCT)
Prior art keywords
cells
coplanar contacts
sheet
holes
deposition
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PCT/FR2005/050814
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French (fr)
Inventor
Christian Belouet
Claude Remy
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Solarforce
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Publication of WO2006045968A1 publication Critical patent/WO2006045968A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/05—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells
    • H01L31/0504—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module
    • H01L31/0516—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module specially adapted for interconnection of back-contact solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/0475—PV cell arrays made by cells in a planar, e.g. repetitive, configuration on a single semiconductor substrate; PV cell microarrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/048—Encapsulation of modules
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • Monolithic multilayer structure for connecting semiconductor cells for connecting semiconductor cells.
  • the present invention relates to a method for manufacturing a monolithic multilayer structure intended to interconnect semiconductor cells, in particular silicon cells, provided with coplanar contacts on their rear faces, as well as the structure obtained by the implementation of the method.
  • the invention also relates to a method for interconnecting semiconductor cells provided with backplane coplanar contacts using said monolithic multilayer structure.
  • the methods are particularly applicable to the manufacture of photovoltaic modules composed of interconnected photovoltaic cells.
  • Photovoltaic modules are optoelectronic components consisting of an assembly of photovoltaic cells, which directly convert incident solar light into electrical energy.
  • the cells are generally made from relatively thick crystalline silicon plates, from 200 to 350 ⁇ m, and generally square in shape from 10 to 15 cm on one side. These cells are encapsulated between two sheets of plastic material - a polymer - under a glass plate which constitutes the front face of the module.
  • the interconnection of cells with each other is carried out using coplanar metal contacts carried on the back of the cells, which allows a simplified interconnection on this face.
  • thin cells of large dimensions are fragile and require a reliable interconnection technique, adaptable to any structure of cells with ce-planar contacts, which minimizes the stresses induced in the silicon wafers.
  • the commercially available copper ribbons are of well-defined dimensions and do not generally correspond to the appropriate dimensions (especially in thickness) that it is desired to give the collecting buses. It is therefore necessary to cut the ribbons according to the geometry that one wants to give to the buses and to be satisfied with the thicknesses commercially available, which are often too large, not compatible with the thin photovoltaic cells.
  • the life of adhesives is not long enough for photovoltaic modules that must operate for at least twenty years.
  • the positioning of copper ribbons for large-scale industrial manufacturing is not easy.
  • the invention solves the difficulties of the prior art by proposing encapsulation of the rear face of the photovoltaic cell by a multilayer and monolithic structure which integrates the bus collectors with connection pads, intended to be connected to the coplanar contacts of the cell. photovoltaic system, and simultaneously performs the functions of encapsulation and protection against the environment.
  • the collecting buses are thus dissociated from the cells and physically (and not mechanically) integrated in a multilayer structure. polymeric material.
  • the bus collectors can be made to a thickness and a geometric pattern adaptable to the demand.
  • the monolithic multilayer structure consists of a bus support sheet, which also provides a protection function against the environment, and an upper sheet which provides the encapsulation function of the rear face of the photovoltaic cell.
  • This encapsulation sheet partially covers the bus collectors.
  • a network of holes opening on the bus collectors is made in this sheet. These holes are intended to receive the connection pads which provide the electrical connection between the collecting bus and the coplanar contacts deposited on the rear face of the photovoltaic cell.
  • the interconnection between the cells is directly carried out during the welding operation between the collecting buses and the coplanar contacts, by a so-called “collective” technique, that is to say which makes it possible to interconnect several cells simultaneously.
  • the subject of the invention is a method for manufacturing a monolithic multilayer structure intended to interconnect semiconductor cells provided with coplanar contacts on the rear face, comprising the following steps: irradiation of the surface of one or more predetermined areas of an electrically insulating substrate sheet containing on its surface photo or thermally reducible particles,
  • connection pads filling said holes with a metal to form connection pads
  • connection pads which are intended to be soldered to said coplanar contacts of said semiconductor cells.
  • Said zones are advantageously irradiated by a laser beam and said substrate sheet is preferably made of a polyethylterephthalate type material.
  • said metal is deposited on the irradiated zones firstly by spontaneous autocatalytic deposition, then by electrolytic deposition and optionally supplemented by a tinning with the wave.
  • the encapsulation sheet is made of a material preferably chosen from polymethyl methacrylate (PMMA), polyvinyl butyl (PVB), ethylene vinyl acetate (EVA) and ethylene (n-butyl acrylate) (EBA).
  • PMMA polymethyl methacrylate
  • PVB polyvinyl butyl
  • EVA ethylene vinyl acetate
  • EBA ethylene (n-butyl acrylate)
  • the holes are made in the encapsulation sheet preferably by laser ablation and their filling is performed by electrolytic deposition of a metal.
  • the metal deposited on the irradiated areas and in the holes is preferably copper.
  • the face of said substrate sheet opposite to the face supporting said collecting buses is protected from the environment by a protective sheet, which may be of a polyvinyl fluoride type material.
  • Positioning marks are advantageously deposited on the surface of the substrate sheet containing the reducible particles, as well as electrical connection terminals of the collecting buses.
  • the subject of the invention is also a monolithic multilayer structure intended to interconnect semiconductor cells provided with coplanar contacts on the rear face, the structure being obtained by implementing the method defined above.
  • the invention also relates to a method of interconnecting semiconductor cells provided with coplanar contacts on the rear face, using a monolithic multilayer structure defined above.
  • the connection pads of the multilayer structure are soldered to the coplanar contacts of the cells by means of said thermal soldering material by simultaneously heating several connection pads contained in the same zone, by scrolling said cells in front of a cell. localized thermal source, or conversely by scrolling said thermal source in front of said cells.
  • the thermal source is advantageously a microwave source or a source of thermal induction.
  • the coplanar contacts of negative and positive polarity are parallel to each other and alternately connected to the zones of the semiconductor respectively n-type and p-type. on the rear face of the cell and the bus collectors are parallel to each other, substantially perpendicular to the coplanar contacts and alternatively negative and positive polarity (designated abbreviation "negative” and “positive” thereafter), the negative and positive coplanar contacts being connected to the respectively positive and negative bus collectors, and the bus collectors of the same type (positive or negative) being interconnected at the same output terminal.
  • the positioning of the coplanar contacts with respect to said bus collectors determines the type of serial or parallel connection of the coplanar contacts, the passage from one type of connection to the other is advantageously effected by offset drilling holes or by translation of cells to timing of the coplanar contacts.
  • FIG. 1 shows schematically a photovoltaic cell positioned above a monolithic multilayer structure according to the invention
  • FIG. 8 shows the photovoltaic cell assembly - interconnected multilayer structure, the coplanar contacts of the cell being connected to the bus of the multilayer structure;
  • FIG. 9 illustrates the method of interconnecting photovoltaic cells with a multilayer structure.
  • the photovoltaic cell 10 of FIG. 1 comprises a thin silicon plate 12 provided on its rear face 14 with positive coplanar contacts 16 and with a negative coplanar contact 18.
  • the monolithic structure 20 makes it possible to interconnect several photovoltaic cells together (as illustrated in FIG. 9), to protect the cells against the external environment and to encapsulate the cells on the rear face.
  • the monolithic structure is a multilayer structure consisting of a stack of two or three sheets of polymer material of possibly different nature:
  • a flat protective sheet 22 provides the protection function against the external environment. It is made of environmentally resistant plastic materials, for example polymers of the Tedlar type (polyvinyl fluoride) or a fluoropolymer or Tefzel from DuPont.
  • a substrate sheet 24 is surface-loaded to a depth of a few micrometers with particles of one or more thermo material and / or photo reducible. These sub-micrometric particles, typically less than 0.5 ⁇ m in size, are deposited by laser impregnation technique or aerosol deposition or by extrusion or by any other known technology.
  • PET polyethyl terephthalate
  • An encapsulation sheet 26 includes the collecting buses 28 and 30 and encapsulates the photovoltaic cell on the rear face. It is perforated with a network of holes 32 filled with an electrically conductive solder material 34. The holes thus filled form interconnection pads 36, which provide the electrical connection between the contacts. coplanar 16 and 18 of the photovoltaic cell and the bus collectors 28 and 30.
  • the substrate sheet 24 is attached to the protective sheet 22 by heating or rolling. Its surface is doped to a depth of a few microns thick with submicron particles of a thermo material and / or photo reducible under ultraviolet irradiation, for example by laser beam. These particles are particles of ZnO, TiO 2 or other compounds with similar behavior. They are preferably partially "reduced" before insertion into the polymer by a high temperature heat treatment.
  • the substrate sheet is characterized by high glass transition temperatures Tg close to 70 ° C. and Tf melting close to 270 ° C. (of the polyester type, for example PET polyethylterephthalate).
  • zones 42 and 44 of the surface 40 are first irradiated by an ultraviolet laser beam 46 (FIG. 2).
  • the shapes and dimensions of these zones correspond to those desired for the bus collectors, for positioning marks (positioning of the buses relative to the coplanar contacts of the cells) as well as for the electrical connection terminals of the modules.
  • thermo or photo reducible particles exposes the reduced or reducible particles of the zones 42 and 44 and has the effect of creating free electrons, which associate with the deposited copper molecules on the irradiated zones. This results in a very strong adhesion of the copper on the zones 42 and 44, of the physical and non-mechanical type as in the devices of the prior art, greater than 0.5 kg / mm 2 .
  • Two ways to proceed are possible to expose the thermo or photo reducible particles:
  • the particles have not undergone prior reduction treatment.
  • the ablation of the zones 42 and 44 of the surface 40 is conducted with an ultraviolet laser to simultaneously expose the reducible particles and their photo reduction.
  • this operation is advantageously carried out with a pulsed excimer laser (preferably krypton fluoride at 248 nm).
  • the illumination required to obtain the exposure and the photo reduction effect on ZnO particles for example is of the order of 350 to 450 mJ / cm 2 by laser firing with a number of shots from 2 to 5 depending on the polymer type of the substrate sheet 24.
  • the reducible particles have undergone a partial reduction by a prior heat treatment (around 1500 ° C. for about one hour in a neutral atmosphere). Their surfaces have characteristics close to those of the reduced photo particles according to the first embodiment.
  • the irradiation with an ultraviolet laser beam can then be limited to the photo ablation of the polymer of the zones 42 and 44, with illumination densities much lower than 400 mJ / cm 2 by laser firing.
  • the irradiation may also be intended to complete the activation of the surface of the particles.
  • the illumination densities remain lower than that practiced in the first embodiment for an equivalent number of shots.
  • this step of the manufacturing method is about five times faster according to the second embodiment than in the first mode.
  • a thin layer (approximately 1 to 2 ⁇ m) of continuous copper is then deposited (FIG. 3) by spontaneous self-catalytic deposition on the irradiated zones 42 and 44.
  • This deposit is carried out in an aqueous solution containing copper ions.
  • metal pins serving as positioning marks may be deposited outside the buses to serve as identifiable identifiers by optical means during the placement of the cells.
  • the auto-catalytic deposition is relatively slow (approximately 5 ⁇ m / h), it is stopped when the deposited copper thickness is approximately one ⁇ m and is completed by a faster electrolytic copper deposition (approximately 25 ⁇ m / h) to the desired thickness for the collecting buses. If necessary, these deposits can be supplemented by tinning the copper track to the wave.
  • the width, the thickness and the (possibly complex) pattern of the collecting buses are easily adaptable since the width and the pattern are determined by the laser irradiation and the thickness by the duration of the copper deposition processes.
  • the thickness of the copper conductor is preferably limited to a few tens of microns to minimize the rigidity of the monolithic structure.
  • the interconnection of the photovoltaic cells is carried out, for example, with bus pairs 28 and 30 of reduced thickness in a range of 10 - 30 .mu.m, at a pitch of 1 to 5 cm and width 2 at 25mm.
  • the encapsulation sheet 26 of polymer material is then deposited (FIG. 4) over the entire surface of the substrate sheet 24 containing the collecting buses 28 and 30.
  • the selected polymer is compatible with the underlying polymer.
  • This polymer is chosen for example from the following families: polymethyl methacrylate (PMMA), polyvinyl butyl (PVB), ethylene vinyl acetate (EVA), ethylene (n-butyl acrylate) (EBA).
  • the structure thus formed in FIG. 4 undergoes a rolling step at a temperature greater than the glass transition temperature Tg of the encapsulation sheet 26. It ensures a planar upper surface and a thickness of polymer material above the surface of the bus a few micrometers only.
  • An array of holes 32 opening onto the bus collectors 28 and 30 is made by laser ablation through the encapsulation sheet 26.
  • the depth and the diameter of these holes intended to receive the connection pads are optimized to facilitate laser ablation and minimize the volume of the solder alloy of the interconnect pads.
  • Connection pads 36 are then made (FIG. 6) in the network of open holes in the preceding step, for example by electrolytic deposition of copper. The connection pads are then covered
  • FIG. 7 by a solder alloy 34, for example by rapid tinning "at the The wave deposition is carried out at a temperature of 0 to 40 ° C. above the melting point of the alloy.
  • the monolithic multilayer structure 20 shown in FIG. 7 makes it possible to connect photovoltaic cells together in a particularly advantageous manner when the thickness of the cells is small.
  • the interconnection of the cells is directly performed via the solder pads 34, which provide the electrical connection between the bus collectors and the coplanar contacts of the cell, by a thermal welding process.
  • the positive coplanar contacts 16 of the silicon wafer 12 are welded by the solder 34 to the connection pads 36 of the positive bus busses 28.
  • the interconnection method is a collective and dynamic process illustrated in FIG. 9.
  • This figure illustrates the interconnection of the coplanar contacts of a photovoltaic cell network (the latter not being represented) with bus collectors of a structure monolithic multilayer similar to the monolithic multilayer structure 20, but having a plurality of bus collectors.
  • Bus collectors 60 of the same type (negative for example), parallel to each other, are connected in parallel to a negative conductor 62, which is connected to an electrical output terminal.
  • Bus collector 64 of the other type (positive), parallel to each other and placed alternately with buses 60, are connected in parallel to a positive conductor 66, connected to the other output terminal. So we have two families of bus collectors (positive and negative).
  • Negative coplanar positive and positive contacts 72 of photovoltaic cells are connected to the bus of the same type, respectively negative 60 and positive 64, by connection pads of the same type, respectively negative 74 (represented by black circles) and positive 76 ( represented by white circles). So we have two families of coplanar contacts (negative and positive) and families of bus and coplanar contacts of the same type are connected electrically between them.
  • the coplanar contacts are arranged parallel to each other, spaced a few millimeters apart, and alternately negative and positive.
  • the connection pads are surmounted by a solder alloy (identical to the solder alloy 34 of FIG. 7).
  • connection pads 74 and 76 of the collecting buses with the coplanar contacts are soldered by means of a thermal, collective and dynamic welding process.
  • the assembly formed by the cells and the monolithic multilayer structure is moved in the direction of the arrow 80 in front of a heat source 82 which, at the same instant, irradiates a predetermined zone extending over the entire width of the assembly (the width is according to the arrow 84).
  • the solder alloy of the connection pads located in the irradiated zone melts, which has the effect of welding simultaneously all the connection pads of this zone.
  • the welding of all the connection pads is performed when the heat source has irradiated the entire surface of the cell-structure multilayer assembly.
  • the temperature profile of the thermal source 82 preferably has an exaggerated extremum and located in a direction perpendicular to the direction of movement of the assembly (displacement according to the arrow 80).
  • the extremum is obtained by means of fixed and localized thermal sources.
  • These sources are preferably sources of energy deposition by direct coupling on the solder pads: microwave or induction, capable of simultaneously processing one or more rows of connection pads over large widths.
  • the duration of the fusion of the solder bond pads is optimized according to its heat capacity and the nature of the polymer (its decomposition temperature) in order to limit the depth of the degraded surrounding polymer to the order of one micrometer. by the thermal field.
  • a typical melting time is a few ms.
  • the coplanar contacts are connected in parallel. According to another possible embodiment (not shown), the contacts are connected in series. To move from one embodiment to another, it suffices simply to shift from one row (offset noted in Figure 9) the piercing of the connection pads ( Figure 5, drilling holes 32). Alternatively, the photovoltaic cells can be moved one row, before the soldering connection pads (displacement noted B in Figure 9).
  • the photovoltaic cells comprise an upper protective sheet (not shown in the figures) situated above the silicon wafer 12 and transparent to sunlight, at least in part of the spectrum.
  • This sheet is a polymer resistant to the external environment, of the same nature as the protective sheet 22 of the monolithic multilayer structure 20.
  • the good adhesion of this upper protective sheet, as well as the protective sheet 22 of the multilayer structure is obtained by heat treatment, which can be made at the same time as the step of welding the connection pads of the multilayer structure to the coplanar contacts of the cell, or independently of this step. At this point, the cells are interconnected and pre-encapsulated.
  • the photovoltaic modules also comprise a transparent glass plate situated above the upper protective polymer sheet (a module according to the invention then being composed from the bottom to the top of the multilayer structure 20, of the silicon wafer 12 with its coplanar contacts 16 and 18, the upper protective polymer sheet and the glass plate).
  • the steps of the method of manufacturing the multilayer structure 20 and interconnecting the cells 10 may then include the setting into module, that is to say the addition in the manufacturing process of the upper polymer sheet and the glass plate.
  • the actual encapsulation is completed, immediately after the interconnection phase, by a conventional rolling process of the photovoltaic modules.
  • the invention is particularly well suited to thin and flexible silicon cells, using, for example, polycrystalline thin plates with a thickness of between 30 and 150 ⁇ m. However, it applies to any structure of semiconductor cells coplanar contacts reported back.
  • Photovoltaic cells are interconnected by a simple process to implement and collective (several cells are interconnected simultaneously).
  • the manufacture of the monolithic multilayer structure is feasible on a large scale (wide and long) with proven and low cost serial production techniques.
  • the adhesion of the copper tracks to the polymer sheet (> 0.5kg / mm 2 ) is excellent and independent of the nature of the polymer.
  • the cells are easily positioned thanks to the positioning marks.
  • the back side of the silicon wafer is well protected by the multilayer structure and the encapsulation is effective.
  • This encapsulation and the low rigidity of the bus collectors provide good resistance of the cells to handling.
  • the encapsulated and interconnected cells can be assembled into sheets or rolls. This possibility solves the delicate problem of thin cell transport.

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Abstract

The invention relates to a method for production of a monolithic multilayer structure (20), for the interconnection of semiconductor cells (10), provided with co-planar contacts (16, 18) on the rear face. The method comprises the following steps: irradiation of the surface of one or more given regions (42, 44) of a electrically-insulating substrate wafer (24), containing photo- or thermo-reducible particles at the surface thereof (40), deposition of a continuous thin metal layer on said irradiated zones such as to form collector buses (28, 30), deposition of a thin encapsulating electrically-insulating layer (26) on the surface (40) of the substrate wafer (24) provided with collector buses (28, 30), piercing holes (32) through the encapsulation layer finishing on the collector buses in given locations, filling said holes with a metal to form connector pins (36) and deposition of a thermal soldering agent (34) on the connector pins.

Description

Structure multicouche monolithique pour la connexion de cellules à semi-conducteur. Monolithic multilayer structure for connecting semiconductor cells.
La présente invention concerne un procédé de fabrication d'une structure multicouche monolithique destinée à interconnecter des cellules à semi-conducteur, notamment au silicium, munies de contacts coplanaires sur leurs faces arrières, ainsi que la structure obtenue par la mise en œuvre du procédé. L'invention concerne également un procédé d'interconnexion de cellules à semi-conducteur munies de contacts coplanaires en face arrière à l'aide de ladite structure multicouche monolithique. Les procédés s'appliquent tout particulièrement à la fabrication de modules photovoltaïques composés de cellules photovoltaïques interconnectées.The present invention relates to a method for manufacturing a monolithic multilayer structure intended to interconnect semiconductor cells, in particular silicon cells, provided with coplanar contacts on their rear faces, as well as the structure obtained by the implementation of the method. The invention also relates to a method for interconnecting semiconductor cells provided with backplane coplanar contacts using said monolithic multilayer structure. The methods are particularly applicable to the manufacture of photovoltaic modules composed of interconnected photovoltaic cells.
Les modules photovoltaïques sont des composants optoélectroniques constitués d'un assemblage de cellules photovoltaïques, qui convertissent directement la lumière solaire incidente en énergie électrique. Les cellules sont généralement réalisées à partir de plaques de silicium cristallin relativement épaisses, de 200 à 350μm, et de forme généralement carrée de 10 à 15cm de côté. Ces cellules sont encapsulées entre deux feuilles en matériau plastique -un polymère- sous une plaque de verre qui constitue la face avant du module.Photovoltaic modules are optoelectronic components consisting of an assembly of photovoltaic cells, which directly convert incident solar light into electrical energy. The cells are generally made from relatively thick crystalline silicon plates, from 200 to 350 μm, and generally square in shape from 10 to 15 cm on one side. These cells are encapsulated between two sheets of plastic material - a polymer - under a glass plate which constitutes the front face of the module.
Pour des raisons de coûts et de rendement, on développe actuellement des cellules photovoltaïques de faible épaisseur, inférieure à 200 microns. Cependant, ces cellules sont fragiles et les techniques classiques de connexion des cellules entre elles ne sont plus adaptées à ces cellules.For reasons of cost and efficiency, photovoltaic cells of small thickness, less than 200 microns, are being developed. However, these cells are fragile and conventional techniques of connecting the cells together are no longer suitable for these cells.
Selon une technologie intéressante, compatible avec les cellules photovoltaïques minces, l'interconnexion des cellules entre elles est réalisée à l'aide de contacts métalliques coplanaires reportés en face arrière des cellules, ce qui permet une interconnexion simplifiée sur cette face. Cependant, les cellules minces de grandes dimensions sont fragiles et requièrent une technique d'interconnexion fiable, adaptable à toute structure de cellules à contacts ce-planaires, qui minimise les contraintes induites dans les plaques de silicium.According to an interesting technology, compatible with thin photovoltaic cells, the interconnection of cells with each other is carried out using coplanar metal contacts carried on the back of the cells, which allows a simplified interconnection on this face. However, thin cells of large dimensions are fragile and require a reliable interconnection technique, adaptable to any structure of cells with ce-planar contacts, which minimizes the stresses induced in the silicon wafers.
Une technique d'interconnexion a été proposée dans un article publié par James M. Gee et al. 26th Photovoltaic Specialists Conférence (PVSC); (1997); Anaheim, CA (USA); 1085-1088. Selon cette technique, l'interconnexion entre cellules est directement obtenue par des ponts conducteurs entre les contacts coplanaires et bus collecteurs, lesquels sont séparés de la cellule et reportés sur une feuille support en plastique. Ces bus, constitués par des pistes de cuivre prédécoupées dans des feuilles dont l'épaisseur est imposée par les produits disponibles sur le marché, sont pré¬ positionnés sur la feuille support. Les ponts conducteurs sont réalisés au moyen de résines époxy conductrices chargées à l'argent. Cette technique présente des inconvénients importants. D'une part, les rubans de cuivre disponibles commercialement sont de dimensions bien définies et ne correspondent généralement pas aux dimensions appropriées (notamment en épaisseur) que l'on souhaite donner aux bus collecteurs. Il faut donc découper les rubans suivant la géométrie que l'on veut donner aux bus et se contenter des épaisseurs commercialement disponibles, lesquelles sont souvent trop grandes, non compatibles avec les cellules photovoltaïques minces. D'autre part, la durée de vie des adhésifs n'est pas assez longue pour des modules photovoltaïques qui doivent fonctionner au moins vingt ans. De plus, le positionnement des rubans de cuivre, pour une fabrication industrielle à grande échelle, n'est pas aisé.An interconnect technique has been proposed in an article published by James M. Gee et al. 26th Photovoltaic Specialists Conference (PVSC); (1997); Anaheim, CA (USA); 1085-1088. According to this technique, the interconnection between cells is directly obtained by conductive bridges between the coplanar contacts and bus collectors, which are separated from the cell and carried on a plastic support sheet. These buses, consisting of pre-cut copper tracks in sheets whose thickness is imposed by the products available on the market, are pre¬ positioned on the support sheet. The conductive bridges are made by means of conductive epoxy resins charged with silver. This technique has significant disadvantages. On the one hand, the commercially available copper ribbons are of well-defined dimensions and do not generally correspond to the appropriate dimensions (especially in thickness) that it is desired to give the collecting buses. It is therefore necessary to cut the ribbons according to the geometry that one wants to give to the buses and to be satisfied with the thicknesses commercially available, which are often too large, not compatible with the thin photovoltaic cells. On the other hand, the life of adhesives is not long enough for photovoltaic modules that must operate for at least twenty years. In addition, the positioning of copper ribbons for large-scale industrial manufacturing is not easy.
L'invention résout les difficultés de l'art antérieur en proposant une encapsulation de la face arrière de la cellule photovoltaïque par une structure multicouche et monolithique qui intègre les bus collecteurs avec des plots de connexion, destinés à être reliés aux contacts coplanaires de la cellule photovoltaïque, et réalise simultanément les fonctions d'encapsulation et de protection contre l'environnement.The invention solves the difficulties of the prior art by proposing encapsulation of the rear face of the photovoltaic cell by a multilayer and monolithic structure which integrates the bus collectors with connection pads, intended to be connected to the coplanar contacts of the cell. photovoltaic system, and simultaneously performs the functions of encapsulation and protection against the environment.
Les bus collecteurs sont ainsi dissociés des cellules et physiquement (et non mécaniquement) intégrés dans une structure multicouche en matériau polymère. Les bus collecteurs sont réalisables suivant une épaisseur et un motif géométrique adaptables à la demande.The collecting buses are thus dissociated from the cells and physically (and not mechanically) integrated in a multilayer structure. polymeric material. The bus collectors can be made to a thickness and a geometric pattern adaptable to the demand.
La structure multicouche monolithique est constituée d'une feuille support des bus, qui assure aussi une fonction de protection contre l'environnement, et d'une feuille supérieure qui assure la fonction d'encapsulation de la face arrière de la cellule photovoltaïque. Cette feuille d'encapsulation recouvre partiellement les bus collecteurs. Un réseau de trous débouchant sur les bus collecteurs est réalisé dans cette feuille. Ces trous sont destinés à recevoir les plots de connexion qui assurent la liaison électrique entre les bus collecteurs et les contacts coplanaires déposés sur la face arrière de la cellule photovoltaïque.The monolithic multilayer structure consists of a bus support sheet, which also provides a protection function against the environment, and an upper sheet which provides the encapsulation function of the rear face of the photovoltaic cell. This encapsulation sheet partially covers the bus collectors. A network of holes opening on the bus collectors is made in this sheet. These holes are intended to receive the connection pads which provide the electrical connection between the collecting bus and the coplanar contacts deposited on the rear face of the photovoltaic cell.
L'interconnexion entre les cellules est directement réalisée au cours de l'opération de soudure entre les bus collecteurs et les contacts coplanaires, par une technique dite "collective", c'est-à-dire qui permet d'interconnecter plusieurs cellules simultanément.The interconnection between the cells is directly carried out during the welding operation between the collecting buses and the coplanar contacts, by a so-called "collective" technique, that is to say which makes it possible to interconnect several cells simultaneously.
De façon plus précise, l'invention a pour objet un procédé de fabrication d'une structure multicouche monolithique destinée à interconnecter des cellules à semi-conducteur munies de contacts coplanaires en face arrière, comprenant les étapes suivantes : - irradiation de la surface d'une ou plusieurs zones prédéterminées d'une feuille substrat électriquement isolante contenant à sa surface des particules photo ou thermo réductibles,More specifically, the subject of the invention is a method for manufacturing a monolithic multilayer structure intended to interconnect semiconductor cells provided with coplanar contacts on the rear face, comprising the following steps: irradiation of the surface of one or more predetermined areas of an electrically insulating substrate sheet containing on its surface photo or thermally reducible particles,
- dépôt d'une couche mince continue d'un métal sur lesdites zones irradiées de façon à former des bus collecteurs, - dépôt d'une feuille mince et électriquement isolante d'encapsulation sur la surface de ladite feuille substrat munie des bus collecteurs,depositing a continuous thin layer of a metal on said irradiated zones so as to form collecting buses; depositing a thin and electrically insulating encapsulation sheet on the surface of said substrate sheet provided with collecting buses;
- percement de trous à travers ladite feuille d'encapsulation débouchant sur lesdits bus collecteurs et à des endroits prédéterminés,piercing holes through said encapsulation sheet opening onto said collecting buses and at predetermined locations,
- remplissage desdits trous par un métal pour former des plots de connexion, etfilling said holes with a metal to form connection pads, and
- dépôt d'un matériau de soudure thermique sur lesdits plots de connexion, lesquels sont destinés à être soudés auxdits contacts coplanaires desdites cellules à semi-conducteur. Lesdites zones sont avantageusement irradiées par un faisceau laser et ladite feuille substrat est de préférence en un matériau du type polyéthyltéréphtalate.depositing a heat-sealing material on said connection pads, which are intended to be soldered to said coplanar contacts of said semiconductor cells. Said zones are advantageously irradiated by a laser beam and said substrate sheet is preferably made of a polyethylterephthalate type material.
Selon un mode de réalisation, ledit métal est déposé sur les zones irradiées tout d'abord par dépôt autocatalytique spontané, puis par dépôt électrolytique et éventuellement complétés par un étamage à la vague.According to one embodiment, said metal is deposited on the irradiated zones firstly by spontaneous autocatalytic deposition, then by electrolytic deposition and optionally supplemented by a tinning with the wave.
La feuille d'encapsulation est en un matériau choisi de préférence parmi le polyméthyle méthacrylate (PMMA), le polyvinyle butyle (PVB), l'éthylène vinyle acétate (EVA) et l'éthylène (n-butyle acrylate) (EBA). Les trous sont réalisés dans la feuille d'encapsulation de préférence par ablation laser et leur remplissage est réalisé par dépôt électrolytique d'un métal.The encapsulation sheet is made of a material preferably chosen from polymethyl methacrylate (PMMA), polyvinyl butyl (PVB), ethylene vinyl acetate (EVA) and ethylene (n-butyl acrylate) (EBA). The holes are made in the encapsulation sheet preferably by laser ablation and their filling is performed by electrolytic deposition of a metal.
Le métal déposé sur les zones irradiées et dans les trous est de préférence du cuivre. Selon un mode de réalisation, la face de ladite feuille substrat opposée à la face supportant lesdits bus collecteurs est protégée de l'environnement par une feuille de protection, qui peut être en un matériau du type fluorure de polyvinyle.The metal deposited on the irradiated areas and in the holes is preferably copper. According to one embodiment, the face of said substrate sheet opposite to the face supporting said collecting buses is protected from the environment by a protective sheet, which may be of a polyvinyl fluoride type material.
Des repères de positionnement sont avantageusement déposés sur la surface de la feuille substrat contenant les particules réductibles, ainsi que des bornes de connexion électrique des bus collecteurs.Positioning marks are advantageously deposited on the surface of the substrate sheet containing the reducible particles, as well as electrical connection terminals of the collecting buses.
L'invention a également pour objet une structure multicouche monolithique destinée à interconnecter des cellules à semi-conducteur munies de contacts coplanaires en face arrière, la structure étant obtenue par la mise en œuvre du procédé défini précédemment.The subject of the invention is also a monolithic multilayer structure intended to interconnect semiconductor cells provided with coplanar contacts on the rear face, the structure being obtained by implementing the method defined above.
L'invention a aussi pour objet un procédé d'interconnexion de cellules à semi-conducteur munies de contacts coplanaires en face arrière, à l'aide d'une structure multicouche monolithique définie précédemment. Selon ce procédé d'interconnexion, les plots de connexion de la structure multicouche sont soudés aux contacts coplanaires des cellules à l'aide dudit matériau de soudure thermique en chauffant simultanément plusieurs plots de connexion contenus dans une même zone, par défilement desdites cellules devant une source thermique localisée, ou inversement par défilement de ladite source thermique devant lesdites cellules. La source thermique est avantageusement une source micro-onde ou une source d'induction thermique. Selon un mode de réalisation, les contacts coplanaires de polarités négative et positive (désignés par abréviation "négatifs" et "positifs" par la suite) sont parallèles entre eux et alternativement reliés aux zones du semi¬ conducteur respectivement de type n et de type p en face arrière de la cellule et les bus collecteurs sont parallèles entre eux, sensiblement perpendiculaires aux contacts coplanaires et alternativement de polarités négative et positive (désignés par abréviation "négatifs" et "positifs" par la suite) , les contacts coplanaires négatifs et positifs étant reliés aux bus collecteurs respectivement négatifs et positifs, et les bus collecteurs d'un même type (positifs ou négatifs) étant reliés entre eux à une même borne de sortie.The invention also relates to a method of interconnecting semiconductor cells provided with coplanar contacts on the rear face, using a monolithic multilayer structure defined above. According to this interconnection method, the connection pads of the multilayer structure are soldered to the coplanar contacts of the cells by means of said thermal soldering material by simultaneously heating several connection pads contained in the same zone, by scrolling said cells in front of a cell. localized thermal source, or conversely by scrolling said thermal source in front of said cells. The thermal source is advantageously a microwave source or a source of thermal induction. According to one embodiment, the coplanar contacts of negative and positive polarity (designated abbreviation "negative" and "positive" thereafter) are parallel to each other and alternately connected to the zones of the semiconductor respectively n-type and p-type. on the rear face of the cell and the bus collectors are parallel to each other, substantially perpendicular to the coplanar contacts and alternatively negative and positive polarity (designated abbreviation "negative" and "positive" thereafter), the negative and positive coplanar contacts being connected to the respectively positive and negative bus collectors, and the bus collectors of the same type (positive or negative) being interconnected at the same output terminal.
Le positionnement des contacts coplanaires par rapport auxdits bus collecteurs détermine le type de connexion série ou parallèle des contacts coplanaires, le passage d'un type de connexion à l'autre s'effectuant avantageusement par décalage du percement des trous ou par translation des cellules au moment du positionnement des contacts coplanaires.The positioning of the coplanar contacts with respect to said bus collectors determines the type of serial or parallel connection of the coplanar contacts, the passage from one type of connection to the other is advantageously effected by offset drilling holes or by translation of cells to timing of the coplanar contacts.
D'autres avantages et caractéristiques de l'invention apparaîtront au cours de la description qui va suivre d'un mode de réalisation, donné à titre d'exemple non limitatif, en référence aux dessins annexés et sur lesquels :Other advantages and features of the invention will become apparent from the following description of an embodiment, given by way of non-limiting example, with reference to the accompanying drawings and in which:
- la figure 1 représente de façon schématique une cellule photovoltaïque positionnée au-dessus d'une structure multicouche monolithique conforme à l'invention;- Figure 1 shows schematically a photovoltaic cell positioned above a monolithic multilayer structure according to the invention;
- les figures 2 à 7 illustrent les étapes du procédé de fabrication de la structure multicouche monolithique de la figure 1 ;- Figures 2 to 7 illustrate the steps of the method of manufacturing the monolithic multilayer structure of Figure 1;
- la figure 8 représente l'ensemble cellule photovoltaïque - structure multicouche interconnectées, les contacts coplanaires de la cellule étant connectés aux bus de la structure multicouche; et- Figure 8 shows the photovoltaic cell assembly - interconnected multilayer structure, the coplanar contacts of the cell being connected to the bus of the multilayer structure; and
- la figure 9 illustre le procédé d'interconnexion de cellules photovoltaïques avec une structure multicouche.- Figure 9 illustrates the method of interconnecting photovoltaic cells with a multilayer structure.
Les figures ne sont pas à l'échelle, les épaisseurs ayant été beaucoup agrandies pour des raisons de clarté. Les mêmes éléments sont désignés par les mêmes numéros de références sur les différentes figures. La cellule photovoltaïque 10 de la figure 1 comprend une plaque mince de silicium 12 munie sur sa face arrière 14 de contacts coplanaires positifs 16 et d'un contact coplanaire négatif 18.The figures are not to scale, the thicknesses having been greatly enlarged for the sake of clarity. The same elements are designated by the same reference numbers in the different figures. The photovoltaic cell 10 of FIG. 1 comprises a thin silicon plate 12 provided on its rear face 14 with positive coplanar contacts 16 and with a negative coplanar contact 18.
La structure monolithique 20 permet d'interconnecter entre elles plusieurs cellules photovoltaïques (comme illustré sur la figure 9), de protéger les cellules contre l'environnement extérieur et d'encapsuler les cellules en face arrière.The monolithic structure 20 makes it possible to interconnect several photovoltaic cells together (as illustrated in FIG. 9), to protect the cells against the external environment and to encapsulate the cells on the rear face.
La structure monolithique est une structure multicouche constituée d'un empilement de deux ou de trois feuilles en matériau polymère de nature éventuellement différente :The monolithic structure is a multilayer structure consisting of a stack of two or three sheets of polymer material of possibly different nature:
- Une feuille plane de protection 22 assure la fonction de protection contre l'environnement extérieur. Elle est réalisée avec des matériaux plastiques résistant à l'environnement, par exemple des polymères de type Tedlar (fluorure de polyvinyl) ou un polymère fluoré ou Tefzel de la société DuPont.- A flat protective sheet 22 provides the protection function against the external environment. It is made of environmentally resistant plastic materials, for example polymers of the Tedlar type (polyvinyl fluoride) or a fluoropolymer or Tefzel from DuPont.
- Une feuille substrat 24 est chargée en surface sur une profondeur de quelques micromètres avec des particules d'un ou de plusieurs matériaux thermo et/ou photo réductibles. Ces particules sub-micrométriques, typiquement de dimension inférieure à 0,5μm, sont déposées par une technique d'imprégnation laser ou de dépôt par aérosol ou par extrusion ou encore par toute autre technologie connue. Cette feuille substrat 24, à base de polyéthyltéréphtalate (PET) par exemple, peut être éliminée si les bus collecteurs sont réalisés directement sur la feuille de protection 22. De façon alternative et réciproque, la feuille de protection 22 peut être supprimée pour autant que l'épaisseur et le matériau de la feuille substrat 24 permettent à cette feuille substrat d'assurer la fonction de protection contre l'environnement extérieur.- A substrate sheet 24 is surface-loaded to a depth of a few micrometers with particles of one or more thermo material and / or photo reducible. These sub-micrometric particles, typically less than 0.5 μm in size, are deposited by laser impregnation technique or aerosol deposition or by extrusion or by any other known technology. This substrate sheet 24, based on polyethyl terephthalate (PET) for example, can be removed if the bus busses are made directly on the protective sheet 22. Alternatively and reciprocally, the protective sheet 22 can be removed as long as the The thickness and the material of the substrate sheet 24 allow this substrate sheet to provide the protective function against the external environment.
- Une feuille d'encapsulation 26 englobe les bus collecteurs 28 et 30 et réalise l'encapsulation de la cellule photovoltaïque en face arrière. Elle est perforée d'un réseau de trous 32 remplis d'un matériau de soudure 34 électriquement conducteur. Les trous ainsi remplis forment des plots d'interconnexion 36, qui assurent la liaison électrique entre les contacts coplanaires 16 et 18 de la cellule photovoltaïque et les bus collecteurs 28 et 30.An encapsulation sheet 26 includes the collecting buses 28 and 30 and encapsulates the photovoltaic cell on the rear face. It is perforated with a network of holes 32 filled with an electrically conductive solder material 34. The holes thus filled form interconnection pads 36, which provide the electrical connection between the contacts. coplanar 16 and 18 of the photovoltaic cell and the bus collectors 28 and 30.
Les étapes de fabrication de la structure multicouche sont illustrées sur les figures 2 à 7. Sur la figure 2, la feuille substrat 24 est fixée à la feuille de protection 22 par chauffage ou par laminage. Sa surface est dopée sur une profondeur de quelques μm d'épaisseur avec des particules sub- micrométriques d'un matériau thermo et/ou photo réductible sous irradiation ultraviolette, par faisceau laser par exemple. Ces particules sont des particules de ZnO, TiO2 ou autres composés à comportement similaire. Elles sont de préférence partiellement "réduites" avant insertion dans le polymère par un traitement thermique à haute température. La feuille substrat est caractérisée par des températures élevées de transition vitreuse Tg voisines de 7O0C et de fusion Tf voisines de 27O0C (du type polyester, par exemple polyéthyltéréphtalate PET). Afin de former des pistes métalliques, de préférence en cuivre, qui formeront les bus collecteurs, des zones 42 et 44 de la surface 40 sont tout d'abord irradiées par un faisceau laser ultraviolet 46 (figure 2). Les formes et les dimensions de ces zones correspondent à celles souhaitées pour les bus collecteurs, pour des repères de positionnement (positionnement des bus par rapport aux contacts coplanaires des cellules) ainsi que pour des bornes de raccordement électriques des modules.The manufacturing steps of the multilayer structure are illustrated in Figures 2 to 7. In Figure 2, the substrate sheet 24 is attached to the protective sheet 22 by heating or rolling. Its surface is doped to a depth of a few microns thick with submicron particles of a thermo material and / or photo reducible under ultraviolet irradiation, for example by laser beam. These particles are particles of ZnO, TiO 2 or other compounds with similar behavior. They are preferably partially "reduced" before insertion into the polymer by a high temperature heat treatment. The substrate sheet is characterized by high glass transition temperatures Tg close to 70 ° C. and Tf melting close to 270 ° C. (of the polyester type, for example PET polyethylterephthalate). In order to form metal tracks, preferably made of copper, which will form the collecting buses, zones 42 and 44 of the surface 40 are first irradiated by an ultraviolet laser beam 46 (FIG. 2). The shapes and dimensions of these zones correspond to those desired for the bus collectors, for positioning marks (positioning of the buses relative to the coplanar contacts of the cells) as well as for the electrical connection terminals of the modules.
Cette irradiation met à nu les particules réduites ou réductibles des zones 42 et 44 et a pour effet de créer des électrons libres, lesquels s'associent aux molécules de cuivre déposé sur les zones irradiées. Il en résulte une très forte adhésion du cuivre sur les zones 42 et 44, de type physique et non mécanique comme dans les dispositifs de l'art antérieur, supérieure à 0,5 kg/mm2. Deux façons de procéder sont possibles pour mettre à nu les particules thermo ou photo réductibles :This irradiation exposes the reduced or reducible particles of the zones 42 and 44 and has the effect of creating free electrons, which associate with the deposited copper molecules on the irradiated zones. This results in a very strong adhesion of the copper on the zones 42 and 44, of the physical and non-mechanical type as in the devices of the prior art, greater than 0.5 kg / mm 2 . Two ways to proceed are possible to expose the thermo or photo reducible particles:
Selon un premier mode de réalisation, les particules n'ont pas subi de traitement de réduction préalable. L'ablation des zones 42 et 44 de la surface 40 est conduite avec un laser ultraviolet pour réaliser simultanément la mise à nu des particules réductibles et leur photo réduction. Dans ce cas, cette opération est réalisée avantageusement avec un laser puisé à excimères (de préférence au fluorure de krypton à 248nm). L'éclairement nécessaire pour obtenir la mise à nu et l'effet de photo réduction sur des particules de ZnO par exemple est de l'ordre de 350 à 450mJ/cm2 par tir laser avec un nombre de tirs de 2 à 5 suivant le type de polymère de la feuille substrat 24.According to a first embodiment, the particles have not undergone prior reduction treatment. The ablation of the zones 42 and 44 of the surface 40 is conducted with an ultraviolet laser to simultaneously expose the reducible particles and their photo reduction. In that case, this operation is advantageously carried out with a pulsed excimer laser (preferably krypton fluoride at 248 nm). The illumination required to obtain the exposure and the photo reduction effect on ZnO particles for example is of the order of 350 to 450 mJ / cm 2 by laser firing with a number of shots from 2 to 5 depending on the polymer type of the substrate sheet 24.
Selon un deuxième mode de réalisation, mode préféré, les particules réductibles ont subi une réduction partielle par un traitement thermique préalable (vers 1.500 0C pendant environ une heure sous atmosphère neutre). Leurs surfaces présentent des caractéristiques proches de celles des particules photo réduites selon le premier mode de réalisation. L'irradiation par un faisceau laser ultraviolet peut alors se limiter à la photo ablation du polymère des zones 42 et 44, avec des densités d'éclairement très inférieures à 400mJ/cm2 par tir laser. L'irradiation peut aussi être destinée à compléter l'activation de la surface des particules. Dans ce cas, les densités d'éclairement restent inférieures à celle pratiquées dans le premier mode de réalisation pour un nombre de tirs équivalent. De façon générale, cette étape du procédé de fabrication est environ cinq fois plus rapide selon le deuxième mode de réalisation que selon le premier mode. Une fine couche (environ 1 à 2μm) de cuivre continue est ensuite déposée (figure 3), par dépôt auto catalytique spontané, sur les zones 42 et 44 irradiées. Ce dépôt s'effectue dans une solution aqueuse contenant des ions cuivre. Au cours de cette opération, des plots métalliques servant de repères de positionnement peuvent être déposés hors des bus pour servir de repères identifiables par voie optique lors de la mise en place des cellules.According to a second embodiment, preferred mode, the reducible particles have undergone a partial reduction by a prior heat treatment (around 1500 ° C. for about one hour in a neutral atmosphere). Their surfaces have characteristics close to those of the reduced photo particles according to the first embodiment. The irradiation with an ultraviolet laser beam can then be limited to the photo ablation of the polymer of the zones 42 and 44, with illumination densities much lower than 400 mJ / cm 2 by laser firing. The irradiation may also be intended to complete the activation of the surface of the particles. In this case, the illumination densities remain lower than that practiced in the first embodiment for an equivalent number of shots. In general, this step of the manufacturing method is about five times faster according to the second embodiment than in the first mode. A thin layer (approximately 1 to 2 μm) of continuous copper is then deposited (FIG. 3) by spontaneous self-catalytic deposition on the irradiated zones 42 and 44. This deposit is carried out in an aqueous solution containing copper ions. During this operation, metal pins serving as positioning marks may be deposited outside the buses to serve as identifiable identifiers by optical means during the placement of the cells.
Le dépôt auto catalytique étant relativement lent (environ 5 μm/h), on l'arrête lorsque l'épaisseur de cuivre déposée est d'environ un μm et on le complète par un dépôt de cuivre par voie électrolytique plus rapide (environ 25 μm/h) à l'épaisseur désirée pour les bus collecteurs. Si nécessaire, ces dépôts peuvent être complétés par un étamage de la piste de cuivre à la vague. La largeur, l'épaisseur et le motif (éventuellement complexe) des bus collecteurs sont facilement adaptables puisque la largeur et le motif sont déterminés par l'irradiation laser et l'épaisseur par la durée des processus de dépôt du cuivre. L'épaisseur du conducteur en cuivre est de préférence limitée à quelques dizaines de micromètres pour minimiser la rigidité de la structure monolithique. A titre d'exemple, pour une cellule photovoltaïque de 100x100cm2, on utilise classiquement dans l'art antérieur des rubans d'interconnexion de largeur 2 mm et d'épaisseur 100μm. Dans la présente invention, l'interconnexion des cellules photovoltaïques est réalisée, à titre d'exemple, avec des paires de bus 28 et 30 d'épaisseur réduite dans une gamme de 10 - 30μm, au pas de 1 à 5cm et de largeur 2 à 25mm.As the auto-catalytic deposition is relatively slow (approximately 5 μm / h), it is stopped when the deposited copper thickness is approximately one μm and is completed by a faster electrolytic copper deposition (approximately 25 μm / h) to the desired thickness for the collecting buses. If necessary, these deposits can be supplemented by tinning the copper track to the wave. The width, the thickness and the (possibly complex) pattern of the collecting buses are easily adaptable since the width and the pattern are determined by the laser irradiation and the thickness by the duration of the copper deposition processes. The thickness of the copper conductor is preferably limited to a few tens of microns to minimize the rigidity of the monolithic structure. For example, for a photovoltaic cell 100x100cm 2 , conventionally used in the prior art interconnect tapes of width 2 mm and thickness 100 .mu.m. In the present invention, the interconnection of the photovoltaic cells is carried out, for example, with bus pairs 28 and 30 of reduced thickness in a range of 10 - 30 .mu.m, at a pitch of 1 to 5 cm and width 2 at 25mm.
La feuille d'encapsulation 26 en matériau polymère est ensuite déposée (figure 4) sur toute la surface de la feuille substrat 24 contenant les bus collecteurs 28 et 30. Le polymère choisi est compatible avec le polymère sous-jacent. Ce polymère est choisi par exemple dans les familles suivantes : polyméthyle méthacrylate (PMMA), polyvinyle butyle (PVB), éthylène vinyle acétate (EVA), éthylène (n-butyle acrylate)(EBA).The encapsulation sheet 26 of polymer material is then deposited (FIG. 4) over the entire surface of the substrate sheet 24 containing the collecting buses 28 and 30. The selected polymer is compatible with the underlying polymer. This polymer is chosen for example from the following families: polymethyl methacrylate (PMMA), polyvinyl butyl (PVB), ethylene vinyl acetate (EVA), ethylene (n-butyl acrylate) (EBA).
La structure ainsi formée à la figure 4 subit une étape de laminage à une température supérieure à la température de transition vitreuse Tg de la feuille d'encapsulation 26. Il assure une surface supérieure plane et une épaisseur de matériau polymère au dessus de la surface des bus de quelques micromètres seulement.The structure thus formed in FIG. 4 undergoes a rolling step at a temperature greater than the glass transition temperature Tg of the encapsulation sheet 26. It ensures a planar upper surface and a thickness of polymer material above the surface of the bus a few micrometers only.
Un réseau de trous 32 (figure 5) débouchant sur les bus collecteurs 28 et 30 est réalisé par ablation laser à travers la feuille d'encapsulation 26. La profondeur et le diamètre de ces trous destinés à recevoir les plots de connexion sont optimisés pour faciliter l'ablation laser et minimiser le volume de l'alliage de soudure des plots d'interconnexion.An array of holes 32 (FIG. 5) opening onto the bus collectors 28 and 30 is made by laser ablation through the encapsulation sheet 26. The depth and the diameter of these holes intended to receive the connection pads are optimized to facilitate laser ablation and minimize the volume of the solder alloy of the interconnect pads.
Des plots de connexion 36 sont ensuite réalisés (figure 6) dans le réseau de trous ouverts dans l'étape précédente, par exemple par dépôt électrolytique de cuivre. Les plots de connexion sont ensuite recouvertsConnection pads 36 are then made (FIG. 6) in the network of open holes in the preceding step, for example by electrolytic deposition of copper. The connection pads are then covered
(figure 7) par un alliage de soudure 34, par exemple par étamage rapide "à la vague" ou une technique équivalente ou toute autre technique de dépôt localisé. Le dépôt à la vague se fait à une température de 0 à 4O0C au- dessus du point de fusion de l'alliage.(FIG. 7) by a solder alloy 34, for example by rapid tinning "at the The wave deposition is carried out at a temperature of 0 to 40 ° C. above the melting point of the alloy.
La structure multicouche monolithique 20 représentée sur la figure 7 permet de connecter des cellules photovoltaïques entre elles de façon particulièrement avantageuse lorsque l'épaisseur des cellules est faible.The monolithic multilayer structure 20 shown in FIG. 7 makes it possible to connect photovoltaic cells together in a particularly advantageous manner when the thickness of the cells is small.
L'interconnexion des cellules est directement réalisée via les plots de soudure 34, qui assurent la liaison électrique entre les bus collecteurs et les contacts coplanaires de la cellule, par un procédé de soudure thermique. Sur la figure 8, les contacts coplanaires positifs 16 de la plaque de silicium 12 sont soudés par la soudure 34 aux plots de connexion 36 des bus collecteurs positifs 28. Il en de même du contact coplanaire négatif 18 soudé au bus collecteur négatif 30.The interconnection of the cells is directly performed via the solder pads 34, which provide the electrical connection between the bus collectors and the coplanar contacts of the cell, by a thermal welding process. In FIG. 8, the positive coplanar contacts 16 of the silicon wafer 12 are welded by the solder 34 to the connection pads 36 of the positive bus busses 28. The same is true of the negative coplanar contact 18 welded to the negative bus 30.
Le procédé d'interconnexion est un procédé collectif et dynamique illustré sur la figure 9. Cette figure illustre l'interconnexion des contacts coplanaires d'un réseau de cellules photovoltaïques (ces dernières n'étant pas représentées) avec des bus collecteurs d'une structure multicouche monolithique semblable à la structure multicouche monolithique 20, mais comportant une pluralité de bus collecteurs. Des bus collecteurs 60 d'un même type (négatifs par exemple), parallèles entre eux, sont connectés en parallèle à un conducteur négatif 62, lequel est relié à une borne de sortie électrique. Des bus collecteurs 64 de l'autre type (positifs), parallèle entre eux et placés en alternance avec les bus 60, sont reliés en parallèle à un conducteur positif 66, relié à l'autre borne de sortie. On a donc deux familles de bus collecteurs (positifs et négatifs). Des contacts coplanaires négatifs 70 et positifs 72 de cellules photovoltaïques sont reliés aux bus collecteurs de même type, respectivement négatifs 60 et positifs 64, par des plots de connexion de même type, respectivement négatifs 74 (représentés par des ronds noirs) et positifs 76 (représentés par des ronds blancs). On a donc deux familles de contacts coplanaires (négatifs et positifs) et les familles de bus et de contacts coplanaires d'un même type sont connectées électriquement entre elles. Les contacts coplanaires sont disposés parallèles entre eux, espacés de quelques millimètres l'un de l'autre, et en alternance négatifs et positifs. Les plots de connexion sont surmontés d'un alliage de soudure (identique à l'alliage de soudure 34 de la figure 7).The interconnection method is a collective and dynamic process illustrated in FIG. 9. This figure illustrates the interconnection of the coplanar contacts of a photovoltaic cell network (the latter not being represented) with bus collectors of a structure monolithic multilayer similar to the monolithic multilayer structure 20, but having a plurality of bus collectors. Bus collectors 60 of the same type (negative for example), parallel to each other, are connected in parallel to a negative conductor 62, which is connected to an electrical output terminal. Bus collector 64 of the other type (positive), parallel to each other and placed alternately with buses 60, are connected in parallel to a positive conductor 66, connected to the other output terminal. So we have two families of bus collectors (positive and negative). Negative coplanar positive and positive contacts 72 of photovoltaic cells are connected to the bus of the same type, respectively negative 60 and positive 64, by connection pads of the same type, respectively negative 74 (represented by black circles) and positive 76 ( represented by white circles). So we have two families of coplanar contacts (negative and positive) and families of bus and coplanar contacts of the same type are connected electrically between them. The coplanar contacts are arranged parallel to each other, spaced a few millimeters apart, and alternately negative and positive. The connection pads are surmounted by a solder alloy (identical to the solder alloy 34 of FIG. 7).
La soudure des plots de connexion 74 et 76 des bus collecteurs avec les contacts coplanaires s'effectue par un procédé de soudure thermique, collectif et dynamique. L'ensemble formé par les cellules et la structure multicouche monolithique est déplacé dans le sens de la flèche 80 devant une source de chaleur 82 qui, à un même instant, irradie une zone prédéterminée s'étendant sur toute la largeur de l'ensemble (la largeur est selon la flèche 84). Sous l'effet de la chaleur, l'alliage de soudure des plots de connexion situés dans la zone irradiée fond, ce qui a pour effet de souder simultanément tous les plots de connexion de cette zone. La soudure de tous les plots de connexion est réalisée lorsque la source de chaleur a irradié toute la surface de l'ensemble cellules-structure multicouche. Le profil de température de la source thermique 82 présente de préférence un extremum accentué et localisé suivant une direction perpendiculaire au sens de déplacement de l'ensemble (déplacement selon la flèche 80).The connection pads 74 and 76 of the collecting buses with the coplanar contacts are soldered by means of a thermal, collective and dynamic welding process. The assembly formed by the cells and the monolithic multilayer structure is moved in the direction of the arrow 80 in front of a heat source 82 which, at the same instant, irradiates a predetermined zone extending over the entire width of the assembly ( the width is according to the arrow 84). Under the effect of heat, the solder alloy of the connection pads located in the irradiated zone melts, which has the effect of welding simultaneously all the connection pads of this zone. The welding of all the connection pads is performed when the heat source has irradiated the entire surface of the cell-structure multilayer assembly. The temperature profile of the thermal source 82 preferably has an exaggerated extremum and located in a direction perpendicular to the direction of movement of the assembly (displacement according to the arrow 80).
L'extremum est obtenu au moyen de sources thermiques fixes et localisées. Ces sources sont de préférence des sources de dépôt d'énergie par couplage direct sur les plots de soudure : micro-onde ou induction, capables de traiter simultanément une ou plusieurs rangées de plots de connexion sur de grandes largeurs. La durée de la fusion de l'alliage de soudure des plots de connexion est optimisée en fonction de sa capacité calorifique et de la nature du polymère (sa température de décomposition) afin de limiter à l'ordre du micromètre la profondeur du polymère environnant dégradée par le champ thermique. Une durée type de fusion est de quelques ms.The extremum is obtained by means of fixed and localized thermal sources. These sources are preferably sources of energy deposition by direct coupling on the solder pads: microwave or induction, capable of simultaneously processing one or more rows of connection pads over large widths. The duration of the fusion of the solder bond pads is optimized according to its heat capacity and the nature of the polymer (its decomposition temperature) in order to limit the depth of the degraded surrounding polymer to the order of one micrometer. by the thermal field. A typical melting time is a few ms.
Dans le mode de réalisation qui vient d'être décrit, les contacts coplanaires sont connectés en parallèle. Selon un autre mode de réalisation possible (non représenté), les contacts sont reliés en série. Pour passer d'un mode de réalisation à l'autre, il suffit simplement de décaler d'une rangée (décalage noté A sur la figure 9) le percement des plots de connexion (figure 5, percement des trous 32). Alternativement, les cellules photovoltaïques peuvent être déplacées d'une rangée, avant la soudure des plots de connexion (déplacement noté B sur la figure 9).In the embodiment just described, the coplanar contacts are connected in parallel. According to another possible embodiment (not shown), the contacts are connected in series. To move from one embodiment to another, it suffices simply to shift from one row (offset noted in Figure 9) the piercing of the connection pads (Figure 5, drilling holes 32). Alternatively, the photovoltaic cells can be moved one row, before the soldering connection pads (displacement noted B in Figure 9).
De façon classique, les cellules photovoltaïques comportent une feuille supérieure de protection (non représentée sur les figures) située au- dessus de la plaque de silicium 12 et transparente à la lumière solaire, au moins dans une partie du spectre. Cette feuille est un polymère résistant à l'environnement extérieur, de même nature que la feuille de protection 22 de la structure multicouche monolithique 20. La bonne adhésion de cette feuille supérieure de protection, ainsi que de la feuille de protection 22 de la structure multicouche, est obtenue par traitement thermique, lequel peut être soit réalisé en même temps que l'étape de soudure des plots de connexion de la structure multicouche aux contacts coplanaires de la cellule, soit indépendamment de cette étape. A ce stade, les cellules sont interconnectées et pré-encapsulées. Cette opération permet d'obtenir des chapelets de cellules photovoltaïques, qui peuvent être transportées sans risque, les cellules ainsi protégées étant peu ou pas fragiles. Généralement les modules photovoltaïques comportent aussi une plaque de verre transparente située au-dessus de la feuille de polymère supérieure de protection (un module selon l'invention étant alors composé de bas en haut de la structure multicouche 20, de la plaque de silicium 12 avec ses contacts coplanaires 16 et 18, de la feuille de polymère de protection supérieure et de la plaque de verre). Les étapes du procédé de fabrication de la structure multicouche 20 et d'interconnexion des cellules 10 peuvent alors inclure la mise en module, c'est-à-dire l'ajout dans le procédé de fabrication de la feuille de polymère supérieure et de la plaque de verre. L'encapsulation proprement dite est complétée, immédiatement après la phase d'interconnexion, par un procédé de laminage classique des modules photovoltaïques. L'invention est particulièrement bien adaptée aux cellules minces et flexibles de silicium, utilisant par exemple des plaques minces polycristallines d'épaisseur comprise entre 30 et 150μm. Elle s'applique cependant à toute structure de cellules à semi-conducteur à contacts coplanaires reportés en face arrière.In a conventional manner, the photovoltaic cells comprise an upper protective sheet (not shown in the figures) situated above the silicon wafer 12 and transparent to sunlight, at least in part of the spectrum. This sheet is a polymer resistant to the external environment, of the same nature as the protective sheet 22 of the monolithic multilayer structure 20. The good adhesion of this upper protective sheet, as well as the protective sheet 22 of the multilayer structure , is obtained by heat treatment, which can be made at the same time as the step of welding the connection pads of the multilayer structure to the coplanar contacts of the cell, or independently of this step. At this point, the cells are interconnected and pre-encapsulated. This operation makes it possible to obtain rosaries of photovoltaic cells, which can be transported without risk, the cells thus protected being little or not fragile. Generally, the photovoltaic modules also comprise a transparent glass plate situated above the upper protective polymer sheet (a module according to the invention then being composed from the bottom to the top of the multilayer structure 20, of the silicon wafer 12 with its coplanar contacts 16 and 18, the upper protective polymer sheet and the glass plate). The steps of the method of manufacturing the multilayer structure 20 and interconnecting the cells 10 may then include the setting into module, that is to say the addition in the manufacturing process of the upper polymer sheet and the glass plate. The actual encapsulation is completed, immediately after the interconnection phase, by a conventional rolling process of the photovoltaic modules. The invention is particularly well suited to thin and flexible silicon cells, using, for example, polycrystalline thin plates with a thickness of between 30 and 150 μm. However, it applies to any structure of semiconductor cells coplanar contacts reported back.
Les avantages procurés par l'invention sont nombreux. Les cellules photovoltaïques sont interconnectées par un procédé simple à mettre en œuvre et collectif (plusieurs cellules sont interconnectées simultanément). La fabrication de la structure multicouche monolithique est réalisable à grande échelle (grande largeur et grande longueur) avec des techniques de production en série éprouvées et à faible coût. On note une grande flexibilité sur l'ajustement de la section et de la géométrie des bus collecteurs ainsi que sur la position, la taille et la forme des plots de soudure de liaison avec les contacts coplanaires des cellules photovoltaïques. L'adhésion des pistes de cuivre sur la feuille polymère (>0,5kg/mm2) est excellente et indépendante de la nature du polymère. Les cellules sont facilement positionnées grâce aux repères de positionnement. La face arrière de la plaque de silicium est bien protégée par la structure multicouche et l'encapsulation est efficace. Cette encapsulation et la faible rigidité des bus collecteurs procurent une bonne résistance des cellules à la manipulation. Les cellules encapsulées et interconnectées peuvent être assemblées en feuilles ou en rouleaux. Cette possibilité résout le problème délicat du transport des cellules minces. The advantages provided by the invention are numerous. Photovoltaic cells are interconnected by a simple process to implement and collective (several cells are interconnected simultaneously). The manufacture of the monolithic multilayer structure is feasible on a large scale (wide and long) with proven and low cost serial production techniques. There is great flexibility in adjusting the section and geometry of the bus collectors as well as the position, size and shape of the bonding solder pads with the coplanar contacts of the photovoltaic cells. The adhesion of the copper tracks to the polymer sheet (> 0.5kg / mm 2 ) is excellent and independent of the nature of the polymer. The cells are easily positioned thanks to the positioning marks. The back side of the silicon wafer is well protected by the multilayer structure and the encapsulation is effective. This encapsulation and the low rigidity of the bus collectors provide good resistance of the cells to handling. The encapsulated and interconnected cells can be assembled into sheets or rolls. This possibility solves the delicate problem of thin cell transport.

Claims

REVENDICATIONS
1. Procédé de fabrication d'une structure multicouche monolithique (20) destinée à interconnecter des cellules à semi-conducteur (10) munies de contacts coplanaires (16, 18) en face arrière, caractérisé par les étapes suivantes :A method of manufacturing a monolithic multilayer structure (20) for interconnecting semiconductor cells (10) provided with backplane coplanar contacts (16, 18), characterized by the steps of:
- irradiation de la surface d'une ou plusieurs zones prédéterminées (42, 44) d'une feuille substrat (24) électriquement isolante contenant à sa surface (40) des particules photo ou thermo réductibles,irradiating the surface of one or more predetermined zones (42, 44) of an electrically insulating substrate sheet (24) containing on its surface (40) photo or thermo reducible particles,
- dépôt d'une couche mince continue d'un métal sur lesdites zones irradiées de façon à former des bus collecteurs (28, 30),depositing a continuous thin layer of a metal on said irradiated zones so as to form collecting buses (28, 30),
- dépôt d'une feuille (26) mince et électriquement isolante d'encapsulation sur la surface (40) de ladite feuille substrat (24) munie des bus collecteurs (28, 30),depositing a thin and electrically insulating encapsulation sheet (26) on the surface (40) of said substrate sheet (24) provided with collecting buses (28, 30),
- percement de trous (32) à travers ladite feuille d'encapsulation débouchant sur lesdits bus collecteurs et à des endroits prédéterminés,piercing holes (32) through said encapsulation sheet opening onto said collecting buses and at predetermined locations,
- remplissage desdits trous par un métal pour former des plots de connexion (36), etfilling said holes with a metal to form connection pads (36), and
- dépôt d'un matériau de soudure thermique (34) sur lesdits plots de connexion, lesquels sont destinés à être soudés auxdits contacts coplanaires (16, 18) desdites cellules à semi-conducteur.depositing a heat-sealing material (34) on said connection pads, which are intended to be soldered to said coplanar contacts (16, 18) of said semiconductor cells.
2. Procédé selon la revendication 1 caractérisé en ce que, préalablement à ladite irradiation desdites zones (42, 44), ladite feuille substrat (24) subit un traitement thermique afin de réduire au moins partiellement lesdites particules.2. Method according to claim 1 characterized in that, prior to said irradiation of said zones (42, 44), said substrate sheet (24) undergoes heat treatment to at least partially reduce said particles.
3. Procédé selon l'une des revendications précédentes caractérisé en ce que lesdites zones (42, 44) sont irradiées par un faisceau laser (46).3. Method according to one of the preceding claims characterized in that said zones (42, 44) are irradiated by a laser beam (46).
4. Procédé selon l'une des revendications précédentes caractérisé en ce que lesdites particules sont des particules de ZnO ou TiO2. 4. Method according to one of the preceding claims characterized in that said particles are particles of ZnO or TiO 2 .
5. Procédé selon l'une des revendications précédentes caractérisé en ce que ladite feuille substrat (24) est en un matériau du type polyéthyltéréphtalate.5. Method according to one of the preceding claims characterized in that said substrate sheet (24) is a polyethylterephthalate type material.
6. Procédé selon l'une des revendications précédentes caractérisé en ce que l'épaisseur de ladite couche mince métallique est comprise entre 10 et 30 microns. 6. Method according to one of the preceding claims characterized in that the thickness of said thin metal layer is between 10 and 30 microns.
7. Procédé selon l'une des revendications précédentes caractérisé en ce que ledit métal est déposé sur les zones irradiées tout d'abord par dépôt autocatalytique spontané, puis par dépôt électrolytique.7. Method according to one of the preceding claims characterized in that said metal is deposited on the irradiated areas first by spontaneous autocatalytic deposition, then by electrolytic deposition.
8. Procédé selon la revendication 7 caractérisé en ce que lesdits dépôts autocatalytique et électrolytique sont complétés par un étamage à la vague.8. The method of claim 7 characterized in that said electroless and electrolytic deposits are completed by a tinning to the wave.
9. Procédé selon l'une des revendications précédentes caractérisé en ce que ladite feuille d'encapsulation (26) est en un matériau choisi parmi le PMMA, PVB, EVA et EBA. 9. Method according to one of the preceding claims characterized in that said encapsulation sheet (26) is a material selected from PMMA, PVB, EVA and EBA.
10. Procédé selon l'une des revendications précédentes caractérisé en ce que lesdits trous (32) sont réalisés par ablation laser. 10. Method according to one of the preceding claims characterized in that said holes (32) are made by laser ablation.
1 1. Procédé selon l'une des revendications précédentes caractérisé en ce que le remplissage desdits trous (32) est réalisé par dépôt électrolytique dudit métal. 1 1. Method according to one of the preceding claims characterized in that the filling of said holes (32) is made by electrolytic deposition of said metal.
12. Procédé selon l'une des revendications précédentes caractérisé en ce que le dépôt dudit matériau de soudure thermique (34) est réalisé par étamage selon le procédé appelé "à la vague".12. Method according to one of the preceding claims characterized in that the deposition of said heat-sealing material (34) is made by tinning according to the method called "wave".
13. Procédé selon l'une des revendications précédentes caractérisé en ce que ledit métal déposé sur lesdites zones irradiées (42, 44) et dans lesdits trous (32) est du cuivre.13. Method according to one of the preceding claims characterized in that said metal deposited on said irradiated areas (42, 44) and in said holes (32) is copper.
14. Procédé selon l'une des revendications précédentes caractérisé en ce que la face de ladite feuille substrat opposée à la face supportant lesdits bus collecteurs est protégée de l'environnement par une feuille de protection (22). 14. Method according to one of the preceding claims characterized in that the face of said substrate sheet opposite the face supporting said bus collectors is protected from the environment by a protective sheet (22).
15. Procédé selon la revendication 14 caractérisé en ce que ladite feuille de protection (22) est en un matériau du type fluorure de polyvinyle. 15. The method of claim 14 characterized in that said protective sheet (22) is of a polyvinyl fluoride type material.
16. Procédé selon l'une des revendications précédentes caractérisé en ce que lesdites cellules à semi-conducteur (10) sont des cellules minces de silicium. 16. Method according to one of the preceding claims characterized in that said semiconductor cells (10) are thin silicon cells.
17. Procédé selon l'une des revendications précédentes caractérisé en ce que, lors du dépôt de ladite couche mince métallique, on forme des repères de positionnement sur la surface de ladite feuille substrat (24) contenant les particules réductibles.17. Method according to one of the preceding claims characterized in that, during the deposition of said thin metal layer, positioning marks are formed on the surface of said substrate sheet (24) containing the reducible particles.
18. Procédé selon l'une des revendications précédentes caractérisé en ce que l'on forme des conducteurs (62, 66) de sortie électrique reliés aux bus collecteurs (60, 64). 18. Method according to one of the preceding claims characterized in that one forms electrical output conductors (62, 66) connected to the bus collectors (60, 64).
19. Structure multicouche monolithique (20) destinée à interconnecter des cellules à semi-conducteur (10) munies de contacts coplanaires (16, 18) en face arrière, ladite structure étant obtenue par la mise en œuvre du procédé défini à l'une des revendications précédentes. 19. Monolithic multilayer structure (20) for interconnecting semiconductor cells (10) provided with backplane coplanar contacts (16, 18), said structure being obtained by implementing the method defined in one of the preceding claims.
20. Procédé d'interconnexion de cellules à semi-conducteur (10) munies de contacts coplanaires (70, 72) en face arrière, à l'aide d'une structure multicouche monolithique (20) définie à la revendication 19, caractérisé en ce que lesdits plots de connexion (74, 76) de la structure sont soudés auxdits contacts coplanaires desdites cellules à l'aide du matériau de soudure thermique en chauffant simultanément ledit matériau de plusieurs plots de connexion contenus dans une même zone, par défilement desdites cellules devant une source thermique localisée (82), ou inversement par défilement de ladite source thermique localisée devant lesdites cellules. A method of interconnecting semiconductor cells (10) provided with backplane coplanar contacts (70, 72), using a monolithic multilayer structure (20) defined in claim 19, characterized in that said connection pads (74, 76) of the structure are welded to said coplanar contacts of said cells with the aid of the heat-sealing material by simultaneously heating said material with a plurality of connection pads contained in the same zone, by scrolling said cells in front of said cells; a localized thermal source (82), or conversely by scrolling said thermal source located in front of said cells.
21. Procédé selon la revendication 20 caractérisé en ce que ladite source thermique (82) est une source micro-onde ou une source d'induction thermique.21. The method of claim 20 characterized in that said heat source (82) is a microwave source or a thermal induction source.
22. Procédé selon l'une des revendications 20 et 21 caractérisé en ce que lesdits contacts coplanaires sont parallèles entre eux et alternativement de polarité négative (70) et de polarité positive (72) et lesdits bus collecteurs sont parallèles entre eux, sensiblement perpendiculaires auxdits contacts coplanaires et alternativement de polarité négative (60) et de polarité positive (64), les contacts coplanaires de polarité négative et de polarité positive étant reliés aux bus collecteurs respectivement de polarité négative et de polarité positive, les bus collecteurs d'un même type (60 ou 64) étant reliés entre eux à une même borne de sortie (62 ou 64).22. Method according to one of claims 20 and 21 characterized in that said coplanar contacts are parallel to each other and alternately of negative polarity (70) and positive polarity (72) and said bus collectors are parallel to each other, substantially perpendicular to said coplanar contacts and alternatively of negative polarity (60) and positive polarity (64), the coplanar contacts of negative polarity and positive polarity being connected to the bus buses respectively of negative polarity and positive polarity, the bus collectors of the same type (60 or 64) being interconnected at the same output terminal (62 or 64).
23. Procédé selon la revendication 22 caractérisé en ce que le positionnement desdits contacts coplanaires (70, 72) par rapport auxdits bus collecteurs (60, 64) détermine le type de connexion série ou parallèle des contacts coplanaires, le passage d'un type de connexion à l'autre s'effectuant par décalage (A) du percement desdits trous ou par translation (B) desdites cellules au moment du positionnement desdits contacts coplanaires. 23. The method of claim 22 characterized in that the positioning of said coplanar contacts (70, 72) relative to said bus collector (60, 64) determines the type of serial or parallel connection coplanar contacts, the passage of a type of connection to the other being effected by offset (A) the drilling of said holes or by translation (B) of said cells at the time of positioning said coplanar contacts.
24. Application de l'invention définie à l'une des revendications précédentes à la réalisation de panneaux de cellules photovoltaïques. 24. Application of the invention defined in one of the preceding claims to the production of photovoltaic cell panels.
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