WO2015111587A1 - Solar-cell interconnector and solar cell module - Google Patents

Solar-cell interconnector and solar cell module Download PDF

Info

Publication number
WO2015111587A1
WO2015111587A1 PCT/JP2015/051421 JP2015051421W WO2015111587A1 WO 2015111587 A1 WO2015111587 A1 WO 2015111587A1 JP 2015051421 W JP2015051421 W JP 2015051421W WO 2015111587 A1 WO2015111587 A1 WO 2015111587A1
Authority
WO
WIPO (PCT)
Prior art keywords
based alloy
alloy solder
solar cell
intermetallic compound
interconnector
Prior art date
Application number
PCT/JP2015/051421
Other languages
French (fr)
Japanese (ja)
Inventor
寺嶋　晋一
木村　圭一
直哉 佐脇
將元 田中
中塚　淳
Original Assignee
新日鉄住金マテリアルズ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 新日鉄住金マテリアルズ株式会社 filed Critical 新日鉄住金マテリアルズ株式会社
Priority to JP2015559075A priority Critical patent/JPWO2015111587A1/en
Priority to TW104102352A priority patent/TW201535759A/en
Publication of WO2015111587A1 publication Critical patent/WO2015111587A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400 degrees C
    • B23K35/262—Sn as the principal constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C13/00—Alloys based on tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C13/00—Alloys based on tin
    • C22C13/02—Alloys based on tin with antimony or bismuth as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/08—Tin or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/38—Wires; Tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
    • 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
    • H01L31/0512—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 made of a particular material or composition of materials
    • 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

  • the present invention relates to a solar cell interconnector and a solar cell module.
  • a solar cell interconnector that connects a plurality of solar cells constituting a solar cell in series and collects electric energy generated in each solar cell. It is suitable for application to.
  • This type of solar cell includes a plurality of solar cells made of PN-connected silicon substrates, and each solar cell is electrically connected in series by a solar cell interconnector, and is generated by each solar cell. Electric energy can be collected by a solar cell interconnector.
  • a flat copper wire plated with solder as shown in Patent Document 1 is widely used.
  • such a solar cell interconnector has a surface of a rectangular copper wire covered with solder made of an Sn-based alloy (hereinafter also simply referred to as Sn-based alloy solder). While being joined to the electrode part of the battery cell, the surface of the flat copper wire is covered with Sn-based alloy solder so that surface oxidation of the flat copper wire can be prevented.
  • the temperature difference between daytime and nighttime may exceed 20 [° C.] depending on the usage environment, and in that case, a solar battery cell is configured.
  • Thermal stress is generated due to the difference between the thermal expansion coefficient of the silicon substrate and the thermal expansion coefficient of the flat copper wire constituting the solar cell interconnector.
  • copper forming a rectangular copper wire has a linear expansion coefficient near room temperature of 16.6 ⁇ 10 ⁇ 6 [K ⁇ 1 ]
  • silicon forming a silicon substrate has a linear expansion coefficient near room temperature. Is 3 ⁇ 10 -6 [K -1 ], so in a usage environment where the temperature difference between day and night is 20 [° C], the length between the silicon substrate and the rectangular copper wire is about 0.03 [%].
  • the solar battery interconnector may be detached from the solar battery cell due to thermal stress caused by the difference in thermal expansion coefficient.
  • SnPb-based alloy SnAgCu-based alloy, SnBi-based alloy, for example, is used as the Sn-based alloy solder covering the rectangular copper wire to improve the thermal fatigue characteristics of the solder. It was the target.
  • the silicon substrate used for the solar cells has been made thinner, and the current product has a mainstream thickness of 180 to 220 [ ⁇ m].
  • a very thin silicon substrate having a thickness of 160 [ ⁇ m] has been used.
  • the mechanical strength is weakened and the thick battery cell itself is more easily deformed.
  • the silicon substrate follows the deformation of the solar cell interconnector. Since deformation is likely to cause bending, this bending increases the partial burden on the solar cell interconnector, and eventually causes damage inside the solar cell interconnector. There was a problem that was not possible.
  • the thickness of the solder plated on the rectangular copper wire is also increasing, and in such thin plated products, it is necessary to ensure strength with a thin cross-sectional area. The interconnector is easily peeled off.
  • the present invention has been made in view of the above problems, and provides a solar cell interconnector and a solar cell module that can suppress peeling from solar cells caused by concentration of thermal stress and internal destruction.
  • the purpose is to do.
  • the present invention contains 50 [wt.%] Or more of Sn, 0.01 to 0.2 [wt.%] Ni, and further 30 to 45 [wt.%] Pb, 0.1 to 4 [wt. %] Ag, 0.1-3 [wt.%] Bi, 0.1-2 [wt.%] Cu, or two or more, and Sn-based alloy solder containing inevitable impurities, rectangular copper wire
  • Sn-based alloy solder containing inevitable impurities, rectangular copper wire
  • the surface of the rectangular copper wire and the Sn-base alloy solder either as an intermetallic compound phase (Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn, or both This is an interconnector for a solar cell.
  • any one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more are added to the Sn-based alloy solder.
  • the solar cell interconnector according to (1) any one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more are added to the Sn-based alloy solder.
  • the present invention is a solar cell module in which solar cells are arranged in series by the solar cell interconnector according to any one of (1) to (3).
  • the solar cell interconnector of the present invention since the thickness of the intermetallic compound phase can be reduced, variation in thickness is suppressed, and a portion where the change in thickness is severe in the conventional intermetallic compound phase is formed. Therefore, it is possible to avoid the concentration of thermal stress as compared with the conventional case, and thus, the solar cell interconnector and the solar cell module that can prevent the peeling from the solar cell and the internal destruction caused by the concentration of the thermal stress. Can provide.
  • the internal breakdown that occurs in conventional interconnectors for solar cells with a flat copper wire surface coated with Sn-based alloy solder is Cu 6 Sn 5 and Cu 3 Sn formed at the interface between the flat copper wire and Sn-based alloy solder.
  • the inventors of the present application have found that it occurs in or near the intermetallic compound phase. And in order to solve the problem of such internal destruction of the interconnector for solar cells, as in the past, simply adding Pb, Ag, Bi to Sn to improve the thermal fatigue characteristics of Sn-based alloy solder It was found that the method is insufficient, and it is important to avoid the concentration of thermal stress in the intermetallic compound phase composed of Cu 6 Sn 5 and Cu 3 Sn and its vicinity.
  • the thickness of the intermetallic compound phase consisting of Cu 6 Sn 5 and Cu 3 Sn, which is conventionally formed at the interface between the flat copper wire and the Sn-based alloy solder is 2 to 5 [ ⁇ m], and the thickness varies. This is because thermal stress concentrates on a portion where the change in thickness (unevenness difference) is severe, and as a result, cracks are likely to progress.
  • the intermetallic compound phase formed in the solar cell interconnector of the present invention contains (Cu, Ni) 6 Sn 5 and (Cu, Ni) 3 Sn, and these (Cu, Ni) 6 Sn 5 and (Cu, Ni) 3 Sn growth rate is smaller than Cu 6 Sn 5 and Cu 3 Sn growth rate, and thickness can be reduced to 1 to 3 [ ⁇ m], so variation in thickness can be suppressed Can be formed as follows. As described above, in the intermetallic compound phase formed at the interface between the flat copper wire and the Sn-based alloy solder in the present invention, the growth rate is slow and the thickness can be formed thin, and accordingly, variation in thickness is suppressed accordingly. Thus, since there is no portion where the change in thickness (unevenness difference) is as severe as in the prior art, concentration of thermal stress can be avoided as compared with the prior art.
  • the surface of a flat copper wire is coated with Sn-based alloy solder, and as the Sn-based alloy solder, 50 [wt.%] Or more of Sn and 0.01 Containing ⁇ 0.2 [wt.%] Ni, 30 ⁇ 45 [wt.%] Pb, 0.1 ⁇ 4 [wt.%] Ag, 0.1 ⁇ 3 [wt.%] Bi, 0.1 ⁇ 2 It is characterized in that it is an Sn-based alloy solder containing any one or more of [wt.%] Cu, and inevitable impurities.
  • Sn-based alloy solders having such a composition examples include Sn-Bi-Ni-based Sn-based alloy solders containing Ni of 0.01 to 0.2 [wt.%], Sn-Pb-2Ag-Ni-based Sn There are base alloy solder, Sn—Pb—Ni based Sn based alloy solder, Sn—Ag—Cu—Ni based Sn based alloy solder, and Sn—Cu—Ni based Sn based alloy solder.
  • the solar cell interconnector covers the surface of the rectangular copper wire with the Sn-based alloy solder formed with such a composition, and as an intermetallic compound phase at the interface between the rectangular copper wire and the Sn-based alloy solder ( Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn can be present, or both, and as a result, the thickness of the intermetallic compound phase can be reduced, thereby suppressing variations in thickness.
  • an intermetallic compound phase at the interface between the rectangular copper wire and the Sn-based alloy solder Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn
  • the effect of avoiding the concentration of the above-mentioned thermal stress is further improved.
  • separation from the solar battery cell can be avoided even under thin plating conditions of, for example, less than 20 [ ⁇ m].
  • the type of intermetallic compound phase is that the Sn-base alloy solder part of the interconnector for solar cells is thinned with FIB (Focused Ion Beam) or microtome, and then the electron diffraction pattern is observed with TEM (Transmission Electron Microscope) Can be identified.
  • the thickness of the intermetallic compound phase formed at the interface between the flat copper wire and the Sn-based alloy solder is such that the surface perpendicular to the axial direction of the solar cell interconnector is subjected to cross-sectional polishing, and the polished surface is subjected to an optical microscope. It can be measured by observing with SEM (Scanning Electron Microscope).
  • the solar cell interconnector avoids the concentration of thermal stress in the intermetallic compound phase by adding Ni to the Sn-based alloy solder in the range of 0.01 to 0.2 [wt.%]. It is possible to obtain an effect that it is possible to prevent deterioration of the bonding property with the electrode portion of the cell.
  • Sn based alloy solder may contain any one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more thereof.
  • Sn base alloy solder contains one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more, Sn base alloy solder The fatigue characteristics can be further improved.
  • the Sn-based alloy solder It is preferably added to the Sn-based alloy solder in a range of up to 0.005 [wt.%].
  • Ge is less than 0.0001 [wt.%]
  • the discoloration of the Sn-base alloy solder cannot be suppressed, and when it exceeds 0.005 [wt.%],
  • the oxidation of the Sn-base alloy solder surface becomes intense, so 0.0001 to 0.005 [ wt.%] is preferably added to the Sn-based alloy solder.
  • the above-mentioned discoloration suppressing effect can be obtained more reliably when Mg is added than when Ge or P is added.
  • the reason why such a phenomenon occurs is that in order to suppress discoloration, a layer mainly composed of Sn oxide microcrystals needs to be densely formed on the surface of Sn. While a microcrystalline layer is easily formed, a partially coarse crystalline layer may be formed when Ge is added. When P is added, a part of the added P is Sn. This is because the above-mentioned microcrystalline layer is not formed reliably and a partially coarse crystalline layer may be formed because it diffuses from the surface to the inside and segregates at the grain boundary of the Sn-based alloy.
  • the degree of oxidation of the Sn-based alloy solder surface can be observed with an optical microscope.
  • the surface of the Sn-based alloy solder is not oxidized
  • the surface is silver white
  • the surface of the Sn-based alloy solder is oxidized
  • the degree of oxidation can be determined based on the color of the Sn-based alloy solder surface.
  • the method for identifying the above-mentioned composition in the Sn-based alloy solder is not particularly limited.
  • energy dispersive X-ray spectroscopy EDS; Energy Dispersive Xray Spectrometry), electron probe analysis (EPMA; Electron Probe Probe Micro Analyzer), Auger Electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), secondary ion mass spectrometry (ICS), inductively coupled plasma analysis (ICP), glow discharge spectral mass spectrometry (GD-) MASS: Glow Discharge Mass Mass Spectrometry (XRF), X-ray Fluorescence Spectrometry (XRF), etc. are preferable because of their abundant results and high accuracy.
  • a portion having a severe change in thickness (unevenness difference) is formed in the intermetallic compound phase, the interior of the intermetallic compound phase, or More than 50 voids with a diameter of 0.3 [ ⁇ m] or more per 1 [mm] length of the bonding interface are formed at the interface between the intermetallic compound and the Sn-based alloy solder, or the inside of the intermetallic compound phase, or It was found that one or more voids having a diameter of 1 [ ⁇ m] or more were formed per 1 [mm] length of the bonding interface at the interface between the intermetallic compound and the Sn-based alloy solder. For this reason, in the conventional solar cell interconnector, thermal stress is concentrated in the void portion, and cracks are likely to progress in the intermetallic compound phase, and in this respect, internal breakage is likely to occur. It was.
  • the interconnector for solar cell of the present invention is to add a predetermined amount of Ni in advance before adding other elements to the Sn-based alloy solder in the manufacturing process of the Sn-based alloy solder.
  • Generation of voids can be suppressed in the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder. That is, in the interconnector for solar cell of the present invention, the diameter is 0.3 [ ⁇ m] or more per 1 [mm] length of the bonding interface inside the intermetallic compound phase or the interface between the intermetallic compound and the Sn-based alloy solder.
  • the number of voids is 50 or less, and voids with a diameter of 1 [ ⁇ m] or more are not formed per 1 [mm] length of the bonding interface inside or in the vicinity of the intermetallic compound phase.
  • the reason why void formation can be suppressed in the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder is as follows. This is because there is another effect of eliminating atomic vacancies. Atomic vacancies are formed by non-uniform diffusion between Sn and Cu in Sn-based alloy solder, but Ni has a high affinity with Cu and easily forms a (Cu, Ni) solid solution. it can. Since the diffusion coefficient in Sn of this (Cu, Ni) solid solution is close to the diffusion coefficient in Sn of Cu, non-uniform diffusion hardly occurs during mutual diffusion, and the formation of atomic vacancies can be suppressed.
  • a void formed inside the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder is a defect that is macroscopically gathered by atomic vacancies. Therefore, if Ni is added in advance to the Sn-based alloy solder, formation of voids can be suppressed inside the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder.
  • Ni contained in the Sn-based alloy solder is preferably in the range of 0.01 to 0.2 [wt.%].
  • the composition of the Sn-based alloy solder it is not sufficient to limit the composition of the Sn-based alloy solder, and it is necessary to produce it by the following process. Specifically, when preparing an Sn-based alloy solder used for covering a rectangular copper wire surface, not all the additive elements are added simultaneously to the Sn bath, but only Ni is added to the Sn bath first. It is desirable to add Sn-Ni alloy (submicron-class fine Ni 3 Sn 4 intermetallic compound in Sn matrix) and then add Bi, Cu, Ag, Pb to Sn-based alloy solder .
  • Sn-Ni alloy submicron-class fine Ni 3 Sn 4 intermetallic compound in Sn matrix
  • NiBi 3 is formed first if Ni and Bi are simultaneously added to the Sn bath.
  • Cu 3 Sn and Cu 6 Sn 5 are formed first, and (Cu, Ni) 6 Sn 5 This is because it is difficult to form (Cu, Ni) 3 Sn. This tendency is particularly noticeable when the Ni concentration in the solder is high, specifically when it is 0.10 [wt.%] Or more.
  • Ni is preferably less than 0.10 [wt.%], Particularly 0.09 [wt.%] Or less, but the following method is used when the Ni concentration range of the present invention is 0.10 [wt.%] Or more. In this case, an intermetallic compound phase composed of (Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn can be formed more reliably.
  • the solar cell interconnector contains Sn of 50 [wt.%] Or more, 0.01 to 0.2 [wt.%] Of Ni, and 30 to 45 [wt.%] Of Pb, 0.1 Sn based alloy solder containing up to 4 [wt.%] Ag, 0.1 to 3 [wt.%] Bi, 0.1 to 2 [wt.%] Cu, or two or more, and inevitable impurities
  • the surface of the rectangular copper wire is covered, and the interface between the rectangular copper wire and the Sn-based alloy solder is composed of (Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn as an intermetallic compound phase. Either one or both were present.
  • this solar cell interconnector can form an intermetallic compound phase that is thinner than the conventional one and further suppresses variations in thickness. ) Can prevent the concentration of thermal stress compared to the conventional amount, and thus can suppress the peeling from the solar battery cell caused by the concentration of thermal stress and the destruction inside the intermetallic compound phase. .
  • this solar cell interconnector 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more are added to the Sn-based alloy solder. It may be.
  • the fatigue characteristics of the Sn-based alloy solder can be further improved by including any one of In, Sb, or two or more in the Sn-based alloy solder, and Mg can be improved.
  • discoloration of the Sn-based alloy solder can be suppressed.
  • a bonding interface 1 [mm] inside the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder 50 or less voids with a diameter of 0.3 [ ⁇ m] or more per length, and a diameter of 1 [ ⁇ m] or more per 1 [mm] length of the bonding interface in or near the intermetallic compound phase.
  • the void is not formed, the thermal stress is suppressed from concentrating on the void part, it is difficult for cracks to occur in the metal compound phase, and the excellent effect of suppressing the breakage inside the intermetallic compound phase is also possible can get.
  • the solar cell interconnector of the present invention is joined to the electrode portions of a plurality of solar cells that convert light energy into electricity, and the solar cell of the present invention.
  • the solar cell can be prevented from peeling off the solar cell interconnector due to the concentration of thermal stress and breaking inside the solar cell interconnector.
  • a battery module can be realized.
  • An oxygen-free copper plate (JIS C1020 1 / 2H material) with a purity of 99.9 [%] and cold-rolled to 0.2 [mm] is slit into a width of 1.5 [mm] and a cross-section of 0.2 [mm]
  • this rectangular copper wire was passed through a hot dipping bath having various solder compositions, and a solar cell interconnector in which the basis weight was 20 [ ⁇ m] and the surface of the rectangular copper wire was coated with Sn-based alloy solder was manufactured. .
  • test was carried out on a test piece having a basis weight of 20 [ ⁇ m] on one side, but some test pieces have a basis weight of 17 [ ⁇ m] on one side for the purpose of evaluating the performance in more detail as will be described later.
  • a thin plated product was prepared in the same manner and used for evaluation. Tables 1 and 2 show the solder compositions of the plating baths used.
  • Examples 1 to 6 are Sn—Pb—Ni-based Sn-based alloy solders containing Ni of 0.01 to 0.2 [wt.%]
  • Examples 7 to 12 are Ni Sn-Ag-Ni-based Sn-base alloy solder containing 0.01 to 0.2 wt.
  • Examples 13 to 18 are Sn-Bi-Ni-based Sn-based alloy solders containing Ni in an amount of 0.01 to 0.2 [wt.%].
  • Examples 19 to 24 are Ni in an amount of 0.01 to 0.2%.
  • Examples 25 to 30 are Sn-Cu-Ni containing 0.01 to 0.2 [wt.%] Ni.
  • Examples 44 to 52 are Sn-Ag-Cu-Ni based alloys containing 0.01 to 0.2 wt.% Ni, Mg, Ge , P or Sn based alloy solder added with two or more.
  • Example 53 is a Sn—Pb—Ni system containing 0.05 [wt.%] Of Ni and Sn-based alloy solder to which Mg, Ge, and P are added.
  • Examples 54 to 57 are Sn-Pb-Ni-based or Sn-Ag-Ni-based Sn-based alloy solders containing 0.1 to 0.2 [wt.%] Of Ni. ] Is an Sn-based alloy solder to which other elements are added without being held for about 20 minutes.
  • each Sn-based alloy solder of Comparative Examples 1 to 18 was prepared by adding only Ni to the Sn bath first, and then adding other elements.
  • a rectangular copper wire drawn out from a bobbin is passed through a tubular furnace heated to 600 [° C] by aeration of N 2 -5% by volume H 2 mixed gas, without touching the outside air. After pre-heating, it was carried out by passing through the inside of the plating tank maintained at 250 [° C.].
  • a flat copper wire whose surface was coated with Sn-based alloy solder was wound around a bobbin. The basis weight of the Sn-based alloy solder was adjusted by blowing argon gas from the wiping nozzle provided above the plating bath toward the flat copper wire coming out from the surface of the plating bath and controlling the gas flow rate. .
  • the degree of oxidation of the Sn-based alloy solder surface was observed with an optical microscope. At that time, if the surface of the Sn-based alloy solder is silver white, the “oxidation” column in Tables 1 and 2 is indicated by a circle, indicating that the surface of the Sn-based alloy solder is not oxidized, yellow, red, etc. If it is discolored, it is judged that the surface of the Sn-based alloy solder has been oxidized, and the “oxidation” column in Tables 1 and 2 is indicated by x.
  • the surface of the Sn-based alloy solder was observed to be silver white, the surface of the Sn-based alloy solder was further heated for 30 hours in an atmospheric furnace maintained at 125 [° C.] as an acceleration test. Observed. As a result, if the surface discoloration of the Sn-based alloy solder stays below 50 [%] of the surface area, the “Oxidation” column is left as ⁇ , and the discoloration of the Sn-based alloy solder is 30 [%] of the surface area.
  • the "Oxidation" column is marked with ⁇ , and if the discoloration of the Sn-based alloy solder stays below 15% of the surface area, the "oxidation” column is marked with ⁇ ⁇ , and the Sn-based alloy solder If no discoloration was observed on the surface of the film, it was marked as excellent, and the “oxidation” column was marked with ⁇ Note that this accelerated heating test is an extremely extreme condition for experimentally determining the superiority or inferiority of the test piece.
  • the type of oxide film layer on the surface of the Sn-based alloy solder, the presence or absence of P segregation at the Sn grain boundaries, and the intermetallic compound phase formed at the interface between the Sn-based alloy solder and the rectangular copper wire were examined.
  • the cross section of the test piece was mechanically polished, and then the polished cross section of the Sn-based alloy solder was observed with FE-SEM.
  • the diffraction pattern of the intermetallic compound phase was obtained from the electron diffraction pattern of TEM to identify the type. If (Cu, Ni) 6 Sn 5 and / or (Cu, Ni) 3 Sn is contained in the intermetallic compound phase, “(Cu, Ni) in the column of“ type of alloy layer ”in Tables 1 and 2 ) 6 Sn 5 (Cu, Ni) 3 Sn ”, on the other hand, if Cu 6 Sn 5 is included in the intermetallic compound phase, the“ type of alloy layer ”column in Table 1 and Table 2 Cu 6 Sn 5 ".
  • the acceleration voltage during FE-SEM observation was set to 20 [kV].
  • the thin film sample to be observed by TEM was obtained by cutting and processing with FIB (Focused Ion Beam), and the acceleration voltage at the time of TEM observation was set to 100 [kV]. From Table 1, in Examples 1 to 53 containing Ni in an amount of 0.01 to 0.2 [wt.%], The intermetallic compound phase is composed of (Cu, Ni) 6 Sn 5 and / or (Cu, Ni) 3 Sn. Was confirmed. On the other hand, in Examples 54 to 57, the special manufacturing method of the present application (a manufacturing method in which a Sn bath in which only Ni was added first was held at a bath temperature of 800 [° C.] for a predetermined time and then other elements were added) was not used.
  • the film thickness of the intermetallic compound phase is 1 to 3 [ ⁇ m], confirming that the film thickness can be made thinner than before, and further suppressing variation in the thickness of the intermetallic compound phase It has been confirmed that.
  • a void with a diameter of 1 [ ⁇ m] or more Is indicated as Y if there is at least one bond per 1 mm in the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder, and both X and Y match.
  • X + Y, and A if no X or Y was observed. From Tables 1 and 2, in Examples 1 to 57 containing 0.01 to 0.2 [wt.%] Of Ni, neither X nor Y was observed for the voids, and the thermal stress was concentrated on the void part. It was confirmed that an intermetallic compound phase capable of suppressing the above could be formed.
  • each solar cell interconnector whose flat copper wire surface was coated with an Sn-based alloy solder having the composition of Examples 1 to 57 and Comparative Examples 1 to 18 was joined to the solar cells.
  • the bonding state at this time was examined.
  • an automatic wiring device manufactured by NPC Corporation was used. This automatic wiring device is a device that reflows Sn-based alloy solder to join the solar cells and the solar cell interconnector, and arranges the solar cell interconnector on the preheated cell-table solar cell.
  • the solar cell used was polycrystalline silicon with a size of 156 x 156 [mm] and a thickness of 160 [ ⁇ m], and the silver electrode width to which the solar cell interconnector provided for current collection was wired was 2 [ mm] in which two electrodes on one side are formed in parallel.
  • evaluation was also performed using a solar battery cell made of polycrystalline silicon having a thickness of 220 [ ⁇ m] (Comparative Example 5 in Table 2).
  • the joining temperature was 250 [° C.].
  • the hot air set temperature was 110 ° C. added to the temperature of the plating bath.
  • the pin holding time was 3 seconds.
  • the results of evaluating the joined state of the joined strings are shown in the “strings” column of Tables 1 and 2.
  • the bonding state was evaluated based on the machine operation stop and bonding state.
  • strings were formed, but the solar cell interconnector partially peeled off from the solar cells during handling, and the subsequent cross-sectional polishing XX indicates that the Sn-based alloy solder (plating layer) of the solar cell interconnector and the electrode on the solar cell were confirmed to be peeled.
  • the strings were formed, but the solar cell interconnector partially peeled off from the solar cells during handling.
  • a cross indicates that destruction has occurred at the intermetallic compound phase inside the interconnector for solar cells or at the interface between the intermetallic compound and the Sn-based alloy solder.
  • a fillet indicating that the Sn-based alloy solder has been wet is not partially formed or there is an unjoined portion, and a fillet is formed throughout and is joined firmly. What was done was shown by (double-circle).
  • the string test was similarly performed using a thin plating product having a basis weight of 17 [ ⁇ m] on one side as described above. . At that time, even if a thin-plated product was used, fillets were formed throughout, and those that were joined soundly were marked as excellent.
  • a thin-plated product having a basis weight of 17 [ ⁇ m] on one side was used, the evaluation of the strings was ⁇ , and it was confirmed that the evaluation of the strings was further improved in these systems.
  • Comparative Example 2 containing Ni of 0.30 [wt.%], Formation of an intermetallic compound phase composed of (Cu, Ni) 6 Sn 5 and / or (Cu, Ni) 3 Sn was confirmed. It was confirmed that the evaluation of XX became poor adhesion to the electrode part of the solar battery cell, and it was confirmed that the content of Ni contained in the Sn-based alloy solder is preferably 0.20 [wt.%] Or less .

Abstract

The purpose of the present invention is to provide a solar-cell interconnector capable of suppressing internal breakage and detachment from a solar cell caused by thermal-stress concentration; and a solar cell module. The present invention makes it possible to provide a solar-cell interconnector which: is capable of suppressing variations in thickness, because it is possible to thinly form the thickness of an intermetallic compound phase; is capable of avoiding concentrations of thermal stress in comparison to the prior art, because there are no sections in the intermetallic compound phase such as those in the prior art which exhibit severe changes in the thickness thereof; and consequently, is capable of suppressing internal breakage and detachment from the solar cell caused by thermal stress concentration. The present invention also provides a solar cell module.

Description

太陽電池用インターコネクタ及び太陽電池モジュールSolar cell interconnector and solar cell module
　本発明は、太陽電池用インターコネクタ及び太陽電池モジュールに関し、例えば太陽電池を構成する複数の太陽電池セルを直列接続させ、各太陽電池セルで生成された電気エネルギーを集電する太陽電池用インターコネクタに適用して好適なものである。 TECHNICAL FIELD The present invention relates to a solar cell interconnector and a solar cell module. For example, a solar cell interconnector that connects a plurality of solar cells constituting a solar cell in series and collects electric energy generated in each solar cell. It is suitable for application to.
　近年、環境保護の意識が高まり、太陽電池はその重要性を一段と増している。この種の太陽電池は、PN接続されたシリコン基板からなる複数の太陽電池セルを備えており、各太陽電池セルが太陽電池用インターコネクタによって電気的に直列接続され、各太陽電池セルで生成された電気エネルギーを太陽電池用インターコネクタによって集電し得るようになされている。 In recent years, the awareness of environmental protection has increased, and the importance of solar cells has further increased. This type of solar cell includes a plurality of solar cells made of PN-connected silicon substrates, and each solar cell is electrically connected in series by a solar cell interconnector, and is generated by each solar cell. Electric energy can be collected by a solar cell interconnector.
　太陽電池セル間を電気的に接続する太陽電池用インターコネクタとしては、特許文献１に示すような平角銅線に半田をめっきしたものが広く使用されている。一般的に、このような太陽電池用インターコネクタは、Sn基合金からなる半田（以下、単にSn基合金半田とも呼ぶ）により平角銅線の表面が被覆されており、当該Sn基合金半田によって太陽電池セルの電極部に接合されるとともに、平角銅線の表面をSn基合金半田で覆うことで平角銅線の表面酸化を防止し得るようになされている。 As a solar cell interconnector for electrically connecting solar cells, a flat copper wire plated with solder as shown in Patent Document 1 is widely used. In general, such a solar cell interconnector has a surface of a rectangular copper wire covered with solder made of an Sn-based alloy (hereinafter also simply referred to as Sn-based alloy solder). While being joined to the electrode part of the battery cell, the surface of the flat copper wire is covered with Sn-based alloy solder so that surface oxidation of the flat copper wire can be prevented.
　ここで、例えば寒暖の激しい屋外に太陽電池を設置した場合には、使用環境によっては昼間と夜間との温度差が20［℃］超となるときもあり、その場合、太陽電池セルを構成するシリコン基板の熱膨張係数と、太陽電池用インターコネクタを構成する平角銅線の熱膨張係数との差に起因した熱応力が発生してしまう。 Here, for example, when a solar battery is installed outdoors in a cold and warm environment, the temperature difference between daytime and nighttime may exceed 20 [° C.] depending on the usage environment, and in that case, a solar battery cell is configured. Thermal stress is generated due to the difference between the thermal expansion coefficient of the silicon substrate and the thermal expansion coefficient of the flat copper wire constituting the solar cell interconnector.
　具体的には、平角銅線を形成する銅は、室温近傍における線膨脹係数が16.6×10-6［K-1］であり、一方、シリコン基板を形成するシリコンは、室温近傍における線膨張係数が3×10-6［K-1］であることから、昼夜の温度差が20［℃］である使用環境下では、シリコン基板と平角銅線との間に約0.03［%］の長さの差が生じてしまい、場合によって熱膨張係数の差に起因した熱応力により太陽電池用インターコネクタが太陽電池セルから剥離してしまうという問題が起こり得る。このような問題点を解決するためには、平角銅線を被覆するSn基合金半田として、例えばSnPb系合金、SnAgCu系合金、SnBi系合金を用い、半田の熱疲労特性を向上させることが一般的であった。 Specifically, copper forming a rectangular copper wire has a linear expansion coefficient near room temperature of 16.6 × 10 −6 [K −1 ], whereas silicon forming a silicon substrate has a linear expansion coefficient near room temperature. Is 3 × 10 -6 [K -1 ], so in a usage environment where the temperature difference between day and night is 20 [° C], the length between the silicon substrate and the rectangular copper wire is about 0.03 [%]. In some cases, the solar battery interconnector may be detached from the solar battery cell due to thermal stress caused by the difference in thermal expansion coefficient. In order to solve such problems, for example, SnPb-based alloy, SnAgCu-based alloy, SnBi-based alloy, for example, is used as the Sn-based alloy solder covering the rectangular copper wire to improve the thermal fatigue characteristics of the solder. It was the target.
特開平１１－２１６６０号公報Japanese Patent Laid-Open No. 11-21660
　ところで、近年、太陽電池セルのコストダウンを図るために、太陽電池セルに使用されるシリコン基板の薄型化が進んでおり、現行品では180～220［μｍ］厚が主流であるのに対し、例えば厚さ160［μｍ］というように非常に薄いシリコン基板が使用されるようになってきている。このような、太陽電池セルでは、シリコン基板の厚みが薄くなっている分、機械的強度が弱まり太電池セル自身が一段と変形し易くなっている。 By the way, in recent years, in order to reduce the cost of solar cells, the silicon substrate used for the solar cells has been made thinner, and the current product has a mainstream thickness of 180 to 220 [μm]. For example, a very thin silicon substrate having a thickness of 160 [μm] has been used. In such a solar battery cell, since the thickness of the silicon substrate is reduced, the mechanical strength is weakened and the thick battery cell itself is more easily deformed.
　そのため、昼夜の温度差がある使用環境下では、上述の熱応力により太陽電池用インターコネクタがシリコン基板から剥離してしまうという問題に加え、太陽電池用インターコネクタの変形に追従してシリコン基板が変形して撓みが生じ易いことから、この撓みによって当該太陽電池用インターコネクタに対する部分的な負担が大きくなり、最終的には太陽電池用インターコネクタの内部で破壊が生じてしまうという、従来に見られなかった問題が生じている。
また、平角銅線上にめっきする半田の厚みも、薄めっき化される場合も増えており、このような薄めっき品では、薄い断面積で強度を確保する必要が生じるため、太陽電池セルからのインターコネクタの剥離も生じやすくなってしまっている。 Therefore, in a usage environment where there is a temperature difference between day and night, in addition to the problem that the solar cell interconnector peels off from the silicon substrate due to the above-described thermal stress, the silicon substrate follows the deformation of the solar cell interconnector. Since deformation is likely to cause bending, this bending increases the partial burden on the solar cell interconnector, and eventually causes damage inside the solar cell interconnector. There was a problem that was not possible.
In addition, the thickness of the solder plated on the rectangular copper wire is also increasing, and in such thin plated products, it is necessary to ensure strength with a thin cross-sectional area. The interconnector is easily peeled off.
　そこで、本発明は、上記問題点に鑑みてなされたものであり、熱応力の集中によって生じる太陽電池セルからの剥離や、内部での破壊を抑制できる太陽電池用インターコネクタ及び太陽電池モジュールを提供することを目的とする。 Accordingly, the present invention has been made in view of the above problems, and provides a solar cell interconnector and a solar cell module that can suppress peeling from solar cells caused by concentration of thermal stress and internal destruction. The purpose is to do.
　（１）本発明は、50［wt.%］以上のSn、及び0.01～0.2［wt.%］のNiを含有し、更に30～45［wt.%］のPb、0.1～4［wt.%］のAg、0.1～3［wt.%］のBi、0.1～2［wt.%］のCuのいずれか、若しくは２つ以上、並びに不可避不純物を含有するSn基合金半田で、平角銅線の表面が被覆されており、前記平角銅線と前記Sn基合金半田との界面に、金属間化合物相として(Cu,Ni)6Sn5又は(Cu,Ni)3Snのいずれか、若しくは両方が存在することを特徴とする太陽電池用インターコネクタである。 (1) The present invention contains 50 [wt.%] Or more of Sn, 0.01 to 0.2 [wt.%] Ni, and further 30 to 45 [wt.%] Pb, 0.1 to 4 [wt. %] Ag, 0.1-3 [wt.%] Bi, 0.1-2 [wt.%] Cu, or two or more, and Sn-based alloy solder containing inevitable impurities, rectangular copper wire The surface of the rectangular copper wire and the Sn-base alloy solder, either as an intermetallic compound phase (Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn, or both This is an interconnector for a solar cell.
　（２）また、本発明は、更に0.1～3［wt.%］のIn、0.1～2［wt.%］のSbのいずれか、若しくは２つ以上が、前記Sn基合金半田に添加されていることを特徴とする（１）記載の太陽電池用インターコネクタである。 (2) Further, according to the present invention, any one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more are added to the Sn-based alloy solder. (1) The solar cell interconnector according to (1).
　（３）また、更に0.0001～0.005［wt.%］のMg、0.0001～0.005［wt.%］のGe、0.001～0.1［wt.%］のPのいずれか、若しくは２つ以上が総計で0.0001～0.1［wt.%］の範囲で、前記Sn基合金半田に添加されていることを特徴とする（１）又は（２）記載の太陽電池用インターコネクタである。 (3) In addition, 0.0001 to 0.005 [wt.%] Mg, 0.0001 to 0.005 [wt.%] Ge, 0.001 to 0.1 [wt.%] P, or two or more total 0.0001 The solar cell interconnector according to (1) or (2), which is added to the Sn-based alloy solder in a range of up to 0.1 [wt.%].
　（４）また、本発明は、（１）～（３）のいずれかに記載の太陽電池用インターコネクタで太陽電池セルを直列配列したことを特徴とする太陽電池モジュールである。 (4) Further, the present invention is a solar cell module in which solar cells are arranged in series by the solar cell interconnector according to any one of (1) to (3).
　本発明の太陽電池用インターコネクタによれば、金属間化合物相の厚みを薄く形成し得ることから、厚みのばらつきが抑制され、金属間化合物相に従来のような厚みの変化が激しい部位が形成されることがないので、従来よりも熱応力の集中を回避でき、かくして、熱応力の集中によって生じる太陽電池セルからの剥離や、内部での破壊を抑制できる太陽電池用インターコネクタ及び太陽電池モジュールを提供し得る。 According to the solar cell interconnector of the present invention, since the thickness of the intermetallic compound phase can be reduced, variation in thickness is suppressed, and a portion where the change in thickness is severe in the conventional intermetallic compound phase is formed. Therefore, it is possible to avoid the concentration of thermal stress as compared with the conventional case, and thus, the solar cell interconnector and the solar cell module that can prevent the peeling from the solar cell and the internal destruction caused by the concentration of the thermal stress. Can provide.
　平角銅線表面をSn基合金半田で被覆した従来の太陽電池用インターコネクタで生じる内部での破壊は、平角銅線とSn基合金半田との界面に形成されるCu6Sn5やCu3Snからなる金属間化合物相の内部、もしくは近傍で生じることを本願発明者らは見出した。そして、このような太陽電池用インターコネクタの内部破壊という課題を解決するには、従来のように、Sn中にPbやAg、Biを単に添加してSn基合金半田の熱疲労特性を向上させる手法では不十分であり、Cu6Sn5やCu3Snからなる金属間化合物相やその近傍での熱応力の集中を回避することが重要であることを見出した。 The internal breakdown that occurs in conventional interconnectors for solar cells with a flat copper wire surface coated with Sn-based alloy solder is Cu 6 Sn 5 and Cu 3 Sn formed at the interface between the flat copper wire and Sn-based alloy solder. The inventors of the present application have found that it occurs in or near the intermetallic compound phase. And in order to solve the problem of such internal destruction of the interconnector for solar cells, as in the past, simply adding Pb, Ag, Bi to Sn to improve the thermal fatigue characteristics of Sn-based alloy solder It was found that the method is insufficient, and it is important to avoid the concentration of thermal stress in the intermetallic compound phase composed of Cu 6 Sn 5 and Cu 3 Sn and its vicinity.
　平角銅線の表面をSn基合金半田で被覆した本発明による太陽電池用インターコネクタでは、従来の太陽電池用インターコネクタにおいて平角銅線とSn基合金半田との界面に形成されるCu6Sn5やCu3Snからなる金属間化合物相の形成を抑制し、当該金属間化合物相に替わって、(Cu,Ni)6Sn5や(Cu,Ni)3Snからなる金属間化合物相を形成することで、金属間化合物相やその近傍での熱応力の集中を回避し得ることを見出した。これは、従来において平角銅線とSn基合金半田との界面に形成されるCu6Sn5やCu3Snからなる金属間化合物相では、その厚みが2～5［μm］となり、厚みにばらつきがある分、厚みの変化（凹凸差）が激しい部位に熱応力が集中してしまい、その結果、亀裂が進展し易くなるためである。 In the solar cell interconnector according to the present invention in which the surface of the flat copper wire is coated with Sn-based alloy solder, Cu 6 Sn 5 formed at the interface between the flat copper wire and the Sn-based alloy solder in the conventional solar cell interconnector. suppressing formation of intermetallic phases consisting of or Cu 3 Sn, in place of the intermetallic compound phase to form a (Cu, Ni) 6 Sn 5 and (Cu, Ni) intermetallic phase consisting of 3 Sn Thus, it has been found that the concentration of thermal stress in the intermetallic compound phase and the vicinity thereof can be avoided. This is because the thickness of the intermetallic compound phase consisting of Cu 6 Sn 5 and Cu 3 Sn, which is conventionally formed at the interface between the flat copper wire and the Sn-based alloy solder, is 2 to 5 [μm], and the thickness varies. This is because thermal stress concentrates on a portion where the change in thickness (unevenness difference) is severe, and as a result, cracks are likely to progress.
　これに対して、本発明の太陽電池用インターコネクタに形成される金属間化合物相は、(Cu,Ni)6Sn5や(Cu,Ni)3Snを含み、これら(Cu,Ni)6Sn5や(Cu,Ni)3Snの成長速度がCu6Sn5やCu3Snの成長速度よりも小さく、厚みが1～3［μm］と薄く形成し得ることから厚みのばらつきを抑制し得るように形成され得る。このように本発明における平角銅線及びSn基合金半田間の界面に形成される金属間化合物相では、成長速度が遅く、その厚さを薄く形成できるので、その分、厚みのばらつきを抑えることができ、かくして、従来のような厚みの変化（凹凸差）が激しい部位がない分、従来よりも熱応力の集中を回避させることができるという効果が得られる。 On the other hand, the intermetallic compound phase formed in the solar cell interconnector of the present invention contains (Cu, Ni) 6 Sn 5 and (Cu, Ni) 3 Sn, and these (Cu, Ni) 6 Sn 5 and (Cu, Ni) 3 Sn growth rate is smaller than Cu 6 Sn 5 and Cu 3 Sn growth rate, and thickness can be reduced to 1 to 3 [μm], so variation in thickness can be suppressed Can be formed as follows. As described above, in the intermetallic compound phase formed at the interface between the flat copper wire and the Sn-based alloy solder in the present invention, the growth rate is slow and the thickness can be formed thin, and accordingly, variation in thickness is suppressed accordingly. Thus, since there is no portion where the change in thickness (unevenness difference) is as severe as in the prior art, concentration of thermal stress can be avoided as compared with the prior art.
　実際上、このような本発明の太陽電池用インターコネクタは、平角銅線の表面がSn基合金半田で被覆されており、当該Sn基合金半田として、50［wt.%］以上のSn及び0.01～0.2［wt.%］のNiを含有し、更に30～45［wt.%］のPb、0.1～4［wt.%］のAg、0.1～3［wt.%］のBi、0.1～2［wt.%］のCuのいずれか、若しくは２つ以上、並びに不可避不純物を含有するSn基合金半田であることを特徴としている。このような組成を有するSn基合金半田としては、例えば、Niを0.01～0.2［wt.%］含有したSn-Bi-Ni系のSn基合金半田や、Sn-Pb-2Ag-Ni系のSn基合金半田、Sn-Pb-Ni系のSn基合金半田、Sn-Ag-Cu-Ni系のSn基合金半田、Sn-Cu-Ni系のSn基合金半田がある。 Actually, in such an interconnector for a solar cell of the present invention, the surface of a flat copper wire is coated with Sn-based alloy solder, and as the Sn-based alloy solder, 50 [wt.%] Or more of Sn and 0.01 Containing ~ 0.2 [wt.%] Ni, 30 ~ 45 [wt.%] Pb, 0.1 ~ 4 [wt.%] Ag, 0.1 ~ 3 [wt.%] Bi, 0.1 ~ 2 It is characterized in that it is an Sn-based alloy solder containing any one or more of [wt.%] Cu, and inevitable impurities. Examples of Sn-based alloy solders having such a composition include Sn-Bi-Ni-based Sn-based alloy solders containing Ni of 0.01 to 0.2 [wt.%], Sn-Pb-2Ag-Ni-based Sn There are base alloy solder, Sn—Pb—Ni based Sn based alloy solder, Sn—Ag—Cu—Ni based Sn based alloy solder, and Sn—Cu—Ni based Sn based alloy solder.
　太陽電池用インターコネクタは、このような組成により形成されたSn基合金半田により平角銅線の表面を被覆することで、平角銅線とSn基合金半田との界面に、金属間化合物相として(Cu,Ni)6Sn5又は(Cu,Ni)3Snのいずれか、若しくは両方が存在する構成となり得、その結果、金属間化合物相の厚みを薄く形成し得ることから厚みのばらつきが抑制され、従来よりも熱応力の集中を回避できるという効果を得られる。 The solar cell interconnector covers the surface of the rectangular copper wire with the Sn-based alloy solder formed with such a composition, and as an intermetallic compound phase at the interface between the rectangular copper wire and the Sn-based alloy solder ( Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn can be present, or both, and as a result, the thickness of the intermetallic compound phase can be reduced, thereby suppressing variations in thickness. Thus, it is possible to obtain an effect that it is possible to avoid concentration of thermal stress as compared with the conventional case.
　また、Sn-Bi-Ni系のSn基合金半田で平角銅線の表面を被覆した太陽電池用インターコネクタでは、上記の熱応力の集中を回避できる効果に加え、後述するような半田表面の酸化抑制効果を得ることができる。 In addition, in the solar cell interconnector in which the surface of the flat copper wire is coated with Sn-Bi-Ni-based Sn-based alloy solder, in addition to the effect of avoiding the concentration of the thermal stress described above, oxidation of the solder surface as described later is performed. An inhibitory effect can be obtained.
　一方、Sn-Pb-2Ag-Ni系又はSn-Cu-Ni系のSn基合金半田で平角銅線の表面を被覆した太陽電池用インターコネクタでは、上記の熱応力の集中を回避できる効果を更に一段と高めることができ、その結果、例えば20［μm］未満というような薄めっきの条件下であっても、太陽電池セルからの剥離を回避できる。 On the other hand, in the solar cell interconnector in which the surface of the flat copper wire is coated with Sn-Pb-2Ag-Ni-based or Sn-Cu-Ni-based Sn-based alloy solder, the effect of avoiding the concentration of the above-mentioned thermal stress is further improved. As a result, separation from the solar battery cell can be avoided even under thin plating conditions of, for example, less than 20 [μm].
　尚、金属間化合物相の種類は、太陽電池用インターコネクタのSn基合金半田部分をFIB(Focused Ion Beam)やミクロトームで薄膜化した後、TEM(Transmission Electron Microscope)で電子回折パターンを観察することで同定できる。また、平角銅線及びSn基合金半田間の界面に形成される金属間化合物相の厚みは、太陽電池用インターコネクタの軸方向と垂直な面を断面研磨しておき、研磨した面を光学顕微鏡やSEM(Scanning Electron Microscope)で観察することで測定できる。 The type of intermetallic compound phase is that the Sn-base alloy solder part of the interconnector for solar cells is thinned with FIB (Focused Ion Beam) or microtome, and then the electron diffraction pattern is observed with TEM (Transmission Electron Microscope) Can be identified. The thickness of the intermetallic compound phase formed at the interface between the flat copper wire and the Sn-based alloy solder is such that the surface perpendicular to the axial direction of the solar cell interconnector is subjected to cross-sectional polishing, and the polished surface is subjected to an optical microscope. It can be measured by observing with SEM (Scanning Electron Microscope).
　このような熱応力の集中を回避できる効果を得るためには、0.01［wt.%］以上のNiをSn基合金半田中に添加する必要がある。一方、Niの添加濃度が0.2［wt.%］超となると、Sn基合金半田表面の酸化が激しくなり、太陽電池セルの電極部との接合性の劣化を招く危険性がある。以上から太陽電池用インターコネクタは、0.01～0.2［wt.%］の範囲でNiをSn基合金半田に含有させることで、金属間化合物相での熱応力の集中を回避し、更には太陽電池セルの電極部との接合性の劣化をも防止し得るという効果を得ることができる。 In order to obtain the effect of avoiding such concentration of thermal stress, it is necessary to add 0.01 wt.% Or more of Ni to the Sn-based alloy solder. On the other hand, when the concentration of Ni exceeds 0.2 [wt.%], The Sn-base alloy solder surface is strongly oxidized, and there is a risk of deteriorating the bonding property with the electrode portion of the solar battery cell. From the above, the solar cell interconnector avoids the concentration of thermal stress in the intermetallic compound phase by adding Ni to the Sn-based alloy solder in the range of 0.01 to 0.2 [wt.%]. It is possible to obtain an effect that it is possible to prevent deterioration of the bonding property with the electrode portion of the cell.
　Sn基合金半田に含有させる30～45［wt.%］のPb、0.1～4［wt.%］のAg、0.1～3［wt.%］のBi、0.1～2［wt.%］のCuは、Sn基合金半田の疲労特性を向上し得る元素である。これら30～45［wt.%］のPb、0.1～4［wt.%］のAg、0.1～3［wt.%］のBi、0.1～2［wt.%］のCuのいずれか、若しくは２つ以上を、Sn基合金半田に含有させることにより、Sn基合金半田の強度を高めて、疲労特性を確保できる。 30 to 45 [wt.%] Pb, 0.1 to 4 [wt.%] Ag, 0.1 to 3 [wt.%] Bi, 0.1 to 2 [wt.%] Cu contained in the Sn-based alloy solder Is an element that can improve the fatigue characteristics of Sn-based alloy solder. 30 to 45 [wt.%] Pb, 0.1 to 4 [wt.%] Ag, 0.1 to 3 [wt.%] Bi, 0.1 to 2 [wt.%] Cu, or 2 By containing one or more of them in the Sn-based alloy solder, the strength of the Sn-based alloy solder can be increased and the fatigue characteristics can be ensured.
　これに加えて、更に、0.1～3［wt.%］のIn、0.1～2［wt.%］のSbのいずれか、若しくは２つ以上を、Sn基合金半田に含有させてもよい。例えば、0.1～3［wt.%］のIn、0.1～2［wt.%］のSbのいずれか、若しくは２つ以上を、Sn基合金半田に含有させた場合には、Sn基合金半田の疲労特性を更に向上させることができる。 In addition, Sn based alloy solder may contain any one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more thereof. For example, when Sn base alloy solder contains one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more, Sn base alloy solder The fatigue characteristics can be further improved.
　これらPb、Ag、Bi、Cu、In、Sbのいずれの元素も上記範囲未満ではSn基合金半田の強度向上効果を得ることができない。一方、Pbは、上限値である45［wt.%］を超えると、融点が上昇するので、45［wt.%］以下であることが好ましい。Agは、上限値である4［wt.%］を超えると、粗大なAg3Snが形成され、実装工程中で気泡をトラップしてしまいボイドが生じてしまうことから、4［wt.%］以下であることが好ましい。Bi、In、Sb、Cuは、上記の上限値を超えると、Sn基合金半田表面の酸化が激しくなることから、上記範囲以下であることが好ましい。 If any of these elements Pb, Ag, Bi, Cu, In, and Sb is less than the above range, the effect of improving the strength of the Sn-based alloy solder cannot be obtained. On the other hand, when Pb exceeds 45 [wt.%], Which is the upper limit, the melting point rises, so it is preferably 45 [wt.%] Or less. Ag, when exceeding an upper limit value 4 [wt.%], Is coarse Ag 3 Sn is formed, since the voids will trap air bubbles occur in the mounting process, 4 [wt.%] The following is preferable. Bi, In, Sb, and Cu are preferably within the above range because oxidation of the Sn-based alloy solder surface becomes severe when the above upper limit is exceeded.
　また、太陽電池用インターコネクタでは、0.0001～0.005［wt.%］のMg、0.0001～0.005［wt.%］のGe、0.001～0.1［wt.%］のPのうちいずれか、若しくはMg、Ge、Pのうち２つ以上を総計で0.0001～0.1［wt.%］の範囲内で、Sn基合金半田に添加することにより、Sn基合金半田の変色を抑制できる。この場合、Mgは、0.0001［wt.%］未満になるとSn基合金半田の変色を抑制し得ず、0.005［wt.%］を超えるとSn基合金半田表面の酸化が激しくなることから、0.0001～0.005［wt.%］の範囲でSn基合金半田に添加されることが好ましい。Geは、0.0001［wt.%］未満になるとSn基合金半田の変色を抑制し得ず、0.005［wt.%］を超えるとSn基合金半田表面の酸化が激しくなることから、0.0001～0.005［wt.%］の範囲でSn基合金半田に添加されることが好ましい。Pは、0.001［wt.%］未満になるとSn基合金半田の変色を抑制し得ず、0.1［wt.%］を超えるとSn基合金半田表面の酸化が激しくなることから、0.001～0.1［wt.%］の範囲でSn基合金半田に添加されることが好ましい。これらMg、Ge、Pのうち２つ以上を添加する場合は、総計で0.0001［wt.%］未満になるとSn基合金半田の変色を抑制し得ず、0.1［wt.%］を超えるとSn基合金半田表面の酸化が激しくなることから、0.0001～0.1［wt.%］の範囲でSn基合金半田に添加されることが好ましい。 In the solar cell interconnector, 0.0001 to 0.005 [wt.%] Mg, 0.0001 to 0.005 [wt.%] Ge, 0.001 to 0.1 [wt.%] P, or Mg, Ge By adding two or more of P to the Sn-base alloy solder within a total range of 0.0001 to 0.1 [wt.%], Discoloration of the Sn-base alloy solder can be suppressed. In this case, if Mg is less than 0.0001 [wt.%], Discoloration of the Sn-based alloy solder cannot be suppressed, and if it exceeds 0.005 [wt.%], The oxidation of the Sn-based alloy solder surface becomes intense. It is preferably added to the Sn-based alloy solder in a range of up to 0.005 [wt.%]. When Ge is less than 0.0001 [wt.%], The discoloration of the Sn-base alloy solder cannot be suppressed, and when it exceeds 0.005 [wt.%], The oxidation of the Sn-base alloy solder surface becomes intense, so 0.0001 to 0.005 [ wt.%] is preferably added to the Sn-based alloy solder. If P is less than 0.001 [wt.%], Discoloration of the Sn-based alloy solder cannot be suppressed, and if it exceeds 0.1 [wt.%], The oxidation of the Sn-based alloy solder surface becomes intense, so 0.001 to 0.1 [ wt.%] is preferably added to the Sn-based alloy solder. When adding two or more of these Mg, Ge, and P, if the total amount is less than 0.0001 [wt.%], Discoloration of the Sn-based alloy solder cannot be suppressed, and if it exceeds 0.1 [wt.%], Sn is exceeded. Since oxidation of the surface of the base alloy solder becomes intense, it is preferable to add to the Sn-base alloy solder in the range of 0.0001 to 0.1 [wt.%].
　尚、上記の変色抑制効果は、Mgを添加すると、GeやPを添加した場合よりも確実に得ることができる。また、Pの添加によってGeを添加した際と同程度の変色抑制効果を得るには、Pを上記のように多量に添加する必要がある。このような現象が起きる理由としては、変色の抑制にはSnの表面にSn酸化物の微結晶を主体とする層が緻密に形成される必要があるが、Mgを添加するとそのような緻密な微結晶層が容易に形成されるのに対し、Geを添加した際は部分的に粗大な結晶層が形成されることがあり、Pを添加した際は添加したPの内の一部がSnの表面から内部に拡散し、Sn基合金の粒界に偏析してしまい上述の微結晶層が確実に形成されずに一部で粗大な結晶層が生じることがあるためである。 It should be noted that the above-mentioned discoloration suppressing effect can be obtained more reliably when Mg is added than when Ge or P is added. In addition, in order to obtain the same discoloration suppressing effect as when Ge is added by adding P, it is necessary to add a large amount of P as described above. The reason why such a phenomenon occurs is that in order to suppress discoloration, a layer mainly composed of Sn oxide microcrystals needs to be densely formed on the surface of Sn. While a microcrystalline layer is easily formed, a partially coarse crystalline layer may be formed when Ge is added. When P is added, a part of the added P is Sn. This is because the above-mentioned microcrystalline layer is not formed reliably and a partially coarse crystalline layer may be formed because it diffuses from the surface to the inside and segregates at the grain boundary of the Sn-based alloy.
　因みに、Sn基合金半田表面の酸化の程度は、光学顕微鏡で観察することができる。例えば、Sn基合金半田の表面が酸化されていない場合には、光学顕微鏡によりSn基合金半田表面を観察した際、銀白色になっており、一方、Sn基合金半田の表面が酸化されている場合には、光学顕微鏡によりSn基合金半田表面を観察した際、黄色や赤色等に変色していることから、Sn基合金半田表面の色により酸化の程度を判断し得る。 Incidentally, the degree of oxidation of the Sn-based alloy solder surface can be observed with an optical microscope. For example, when the surface of the Sn-based alloy solder is not oxidized, when the surface of the Sn-based alloy solder is observed with an optical microscope, the surface is silver white, while the surface of the Sn-based alloy solder is oxidized In this case, when the surface of the Sn-based alloy solder is observed with an optical microscope, the color changes to yellow, red, or the like. Therefore, the degree of oxidation can be determined based on the color of the Sn-based alloy solder surface.
　Sn基合金半田中の上記組成を同定する手法については特に制限は無いが、例えばエネルギー分散X線分光法（EDS；Energy Dispersive Xray Spectrometry）、電子プローブ分析法（EPMA；Electron Probe Micro Analyzer）、オージェ電子分光法（AES；Auger Electron Spctroscopy）、二次イオン質量分析法（SIMS；Secondary Ion-microprobe Mass Spectrometer）、誘導結合プラズマ分析法（ICP；Inductively Coupled Plasma）、グロー放電スペクトル質量分析法（GD-MASS；Glow Discharge Mass Spectrometry）、蛍光Ｘ線分析法（XRF；X-ray Fluorescence Spectrometer）等が実績も豊富で、精度も高いことから好ましい。 The method for identifying the above-mentioned composition in the Sn-based alloy solder is not particularly limited. For example, energy dispersive X-ray spectroscopy (EDS; Energy Dispersive Xray Spectrometry), electron probe analysis (EPMA; Electron Probe Probe Micro Analyzer), Auger Electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), secondary ion mass spectrometry (ICS), inductively coupled plasma analysis (ICP), glow discharge spectral mass spectrometry (GD-) MASS: Glow Discharge Mass Mass Spectrometry (XRF), X-ray Fluorescence Spectrometry (XRF), etc. are preferable because of their abundant results and high accuracy.
　また、本願発明者らが鋭意検討した結果、従来の太陽電池用インターコネクタでは、金属間化合物相に厚みの変化（凹凸差）が激しい部位が形成される他、金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面に接合界面1［mm］長あたり、直径0.3［μm］以上の大きさのボイドが50個超形成されたり、又は、金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面に接合界面1［mm］長あたり、直径1［μm］以上の大きさのボイドが1個以上形成されることが分かった。このため、従来の太陽電池用インターコネクタでは、熱応力がボイド部分に集中してしまい、金属間化合物相にて亀裂が進展し易くなっており、この点において内部での破壊が生じ易くなっていた。 In addition, as a result of intensive studies by the inventors of the present application, in the conventional interconnector for solar cell, a portion having a severe change in thickness (unevenness difference) is formed in the intermetallic compound phase, the interior of the intermetallic compound phase, or More than 50 voids with a diameter of 0.3 [μm] or more per 1 [mm] length of the bonding interface are formed at the interface between the intermetallic compound and the Sn-based alloy solder, or the inside of the intermetallic compound phase, or It was found that one or more voids having a diameter of 1 [μm] or more were formed per 1 [mm] length of the bonding interface at the interface between the intermetallic compound and the Sn-based alloy solder. For this reason, in the conventional solar cell interconnector, thermal stress is concentrated in the void portion, and cracks are likely to progress in the intermetallic compound phase, and in this respect, internal breakage is likely to occur. It was.
　これに対して、本発明の太陽電池用インターコネクタは、Sn基合金半田の製造過程において、Sn基合金半田中に他の元素を添加する前に予め所定量のNiを添加しておくことで、金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面にてボイドの発生を抑制し得る。すなわち、本発明の太陽電池用インターコネクタでは、金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面に接合界面1［mm］長あたり、直径0.3［μm］以上の大きさのボイドが50個以下となり、かつ、金属間化合物相の内部、若しくはその近傍において接合界面1［mm］長あたり、直径1［μm］以上の大きさのボイドが形成されない構成となり、熱応力のボイド部分への集中を抑制して金属間化合物相で亀裂が発生し難く、内部での破壊を抑制し得るという優れた効果も得られる。 On the other hand, the interconnector for solar cell of the present invention is to add a predetermined amount of Ni in advance before adding other elements to the Sn-based alloy solder in the manufacturing process of the Sn-based alloy solder. Generation of voids can be suppressed in the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder. That is, in the interconnector for solar cell of the present invention, the diameter is 0.3 [μm] or more per 1 [mm] length of the bonding interface inside the intermetallic compound phase or the interface between the intermetallic compound and the Sn-based alloy solder. The number of voids is 50 or less, and voids with a diameter of 1 [μm] or more are not formed per 1 [mm] length of the bonding interface inside or in the vicinity of the intermetallic compound phase. An excellent effect is obtained in that the concentration in the void portion is suppressed, cracks are hardly generated in the intermetallic compound phase, and internal destruction can be suppressed.
　このように金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面においてボイドの形成を抑制し得る理由としては、Sn基合金半田中に添加したNiに、金属又は合金中で原子空孔(Vacancy)を消滅させるという別の効果があるためである。原子空孔は、Sn基合金半田中のSnとCuとの間で不均一拡散が生じることで形成されるが、NiはCuとの親和性が高く、容易に(Cu,Ni)固溶体を形成できる。この(Cu,Ni)固溶体のSn中の拡散係数はSnのCu中の拡散係数と近いため、相互拡散時に不均一拡散が生じ難くなり、原子空孔の形成を抑制し得る。金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面に形成されるボイドは、原子空孔が集合して巨視化した欠陥である。従って、Sn基合金半田中に予めNiを添加すれば、金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面でボイドの形成を抑制できる。 The reason why void formation can be suppressed in the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder is as follows. This is because there is another effect of eliminating atomic vacancies. Atomic vacancies are formed by non-uniform diffusion between Sn and Cu in Sn-based alloy solder, but Ni has a high affinity with Cu and easily forms a (Cu, Ni) solid solution. it can. Since the diffusion coefficient in Sn of this (Cu, Ni) solid solution is close to the diffusion coefficient in Sn of Cu, non-uniform diffusion hardly occurs during mutual diffusion, and the formation of atomic vacancies can be suppressed. A void formed inside the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder is a defect that is macroscopically gathered by atomic vacancies. Therefore, if Ni is added in advance to the Sn-based alloy solder, formation of voids can be suppressed inside the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder.
　このような効果を得るには、0.01［wt.%］以上のNiをSn基合金半田中に添加する必要がある。一方、Niの添加濃度が0.2［wt.%］超となると、NiがCuと反応して(Cu,Ni)固溶体を形成するよりも、Snと反応して半径数［μm］超という粗大なNi3Sn4でなる金属間化合物を形成する方が優勢となり、上記の原子空孔の抑制効果が得られ難くなる。従って、この観点からも、Sn基合金半田中に含有させるNiは、0.01～0.2［wt.%］の範囲とすることが好ましい。因みに、金属間化合物相中のボイドの観察は、X線透過観察装置を用いて行うことができる。 In order to obtain such an effect, it is necessary to add 0.01 [wt.%] Or more of Ni to the Sn-based alloy solder. On the other hand, when the added concentration of Ni exceeds 0.2 [wt.%], Ni reacts with Sn to form a (Cu, Ni) solid solution, and reacts with Sn to give a coarse radius of more than [μm]. Forming an intermetallic compound composed of Ni 3 Sn 4 becomes dominant, and the above-described effect of suppressing atomic vacancies becomes difficult to obtain. Therefore, also from this viewpoint, the Ni contained in the Sn-based alloy solder is preferably in the range of 0.01 to 0.2 [wt.%]. Incidentally, the observation of voids in the intermetallic compound phase can be performed using an X-ray transmission observation apparatus.
　本発明の太陽電池用インターコネクタを製造するに当たり、Sn基合金半田の組成を限定するだけでは不十分であり、下記のプロセスにより製造することが必要となる。具体的には、平角銅線表面の被覆に用いるSn基合金半田を作製する際、全ての添加元素を同時にSn浴中に添加するのではなく、Niのみを先にSn浴中に添加してSn-Ni合金（Snマトリックス中にサブミクロンクラスの微細なNi3Sn4金属間化合物が析出した状態）としておき、その後、BiやCu、Ag、PbをSn基合金半田に添加することが望ましい。 In producing the solar cell interconnector of the present invention, it is not sufficient to limit the composition of the Sn-based alloy solder, and it is necessary to produce it by the following process. Specifically, when preparing an Sn-based alloy solder used for covering a rectangular copper wire surface, not all the additive elements are added simultaneously to the Sn bath, but only Ni is added to the Sn bath first. It is desirable to add Sn-Ni alloy (submicron-class fine Ni 3 Sn 4 intermetallic compound in Sn matrix) and then add Bi, Cu, Ag, Pb to Sn-based alloy solder .
　例えば、Sn基合金半田にBiを添加する場合、NiとBiを同時にSn浴中に添加すると、NiBi3が先に形成されてしまうためである。また、Sn基合金半田のCuを添加する場合も、CuとNiを同時にSn浴中に添加すると、Cu3SnやCu6Sn5が先に形成されてしまい、(Cu,Ni)6Sn5や(Cu,Ni)3Snが形成され難くなるためである。この傾向は、半田中のNi濃度が高い場合、具体的には0.10［wt.%］以上となる場合に特に顕著であり、このNi濃度の半田を通常の製造法で製造すると、Cu3SnやCu6Sn5が先に形成されてしまい、(Cu,Ni)6Sn5や(Cu,Ni)3Snが形成され難くなってしまう。よって、Niは、0.10［wt.%］未満、特に0.09［wt.%］以下が好ましいが、本発明のNi濃度の範囲のうち0.10［wt.%］以上としたときには更に次の手法を用いることが望ましく、これにより(Cu,Ni)6Sn5や(Cu,Ni)3Snでなる金属間化合物相を一段と確実に形成し得る。 For example, when Bi is added to an Sn-based alloy solder, NiBi 3 is formed first if Ni and Bi are simultaneously added to the Sn bath. Also, when adding Cu of the Sn-based alloy solder, if Cu and Ni are simultaneously added to the Sn bath, Cu 3 Sn and Cu 6 Sn 5 are formed first, and (Cu, Ni) 6 Sn 5 This is because it is difficult to form (Cu, Ni) 3 Sn. This tendency is particularly noticeable when the Ni concentration in the solder is high, specifically when it is 0.10 [wt.%] Or more. When a solder with this Ni concentration is manufactured by a normal manufacturing method, Cu 3 Sn Cu 6 Sn 5 is formed first, and (Cu, Ni) 6 Sn 5 and (Cu, Ni) 3 Sn are hardly formed. Therefore, Ni is preferably less than 0.10 [wt.%], Particularly 0.09 [wt.%] Or less, but the following method is used when the Ni concentration range of the present invention is 0.10 [wt.%] Or more. In this case, an intermetallic compound phase composed of (Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn can be formed more reliably.
　すなわち、平角銅線及びSn基合金半田間の界面に(Cu,Ni)6Sn5や(Cu,Ni)3Snでなる金属間化合物相を一段と確実に形成させるには、上記のようにNiのみが先に添加されたSn浴において、その浴温をNi3Sn4でなる金属間化合物の融点以上（具体的には800［℃］以上）まで高め、その状態で所定時間保持（20分以上保持）することにより、Sn浴内にてNi3Sn4でなる金属間化合物を完全に溶解させ、その後に他の元素（Pb、Ag、Bi、Cu、In、Sb）を添加する工程を追加することが望ましい。 That is, in order to more reliably form an intermetallic compound phase composed of (Cu, Ni) 6 Sn 5 and (Cu, Ni) 3 Sn at the interface between the rectangular copper wire and the Sn-based alloy solder, as described above, Ni In the Sn bath to which only the first was added, the bath temperature was raised to the melting point of the intermetallic compound composed of Ni 3 Sn 4 (specifically, 800 [° C.] or higher) and held in that state for a predetermined time (20 minutes) To hold the intermetallic compound of Ni 3 Sn 4 completely in the Sn bath, and then add other elements (Pb, Ag, Bi, Cu, In, Sb). It is desirable to add.
　以上の構成において、太陽電池用インターコネクタでは、50［wt.%］以上のSn、及び0.01～0.2［wt.%］のNiを含有し、更に30～45［wt.%］のPb、0.1～4［wt.%］のAg、0.1～3［wt.%］のBi、0.1～2［wt.%］のCuのいずれか、若しくは２つ以上、並びに不可避不純物を含有するSn基合金半田で、平角銅線の表面を被覆した構成を有し、平角銅線とSn基合金半田との界面に、金属間化合物相として(Cu,Ni)6Sn5又は(Cu,Ni)3Snのいずれか、若しくは両方が存在するようにした。 In the above configuration, the solar cell interconnector contains Sn of 50 [wt.%] Or more, 0.01 to 0.2 [wt.%] Of Ni, and 30 to 45 [wt.%] Of Pb, 0.1 Sn based alloy solder containing up to 4 [wt.%] Ag, 0.1 to 3 [wt.%] Bi, 0.1 to 2 [wt.%] Cu, or two or more, and inevitable impurities The surface of the rectangular copper wire is covered, and the interface between the rectangular copper wire and the Sn-based alloy solder is composed of (Cu, Ni) 6 Sn 5 or (Cu, Ni) 3 Sn as an intermetallic compound phase. Either one or both were present.
　これにより、この太陽電池用インターコネクタでは、従来よりも厚みが薄く、更に厚みのばらつきが抑制された金属間化合物相を形成し得、金属間化合物相に従来のような厚みの変化（凹凸差）が激しい部位の形成が抑制されている分、従来よりも熱応力の集中を回避でき、かくして熱応力の集中によって生じる太陽電池セルからの剥離や、金属間化合物相内部での破壊を抑制できる。 As a result, this solar cell interconnector can form an intermetallic compound phase that is thinner than the conventional one and further suppresses variations in thickness. ) Can prevent the concentration of thermal stress compared to the conventional amount, and thus can suppress the peeling from the solar battery cell caused by the concentration of thermal stress and the destruction inside the intermetallic compound phase. .
　また、この太陽電池用インターコネクタでは、更に0.1～3［wt.%］のIn、0.1～2［wt.%］のSbのいずれか、若しくは２つ以上を、Sn基合金半田に添加するようにしてもよい。これにより、太陽電池用インターコネクタでは、In、Sbのいずれか、若しくは２つ以上を、Sn基合金半田に含有させることで、Sn基合金半田の疲労特性を更に向上させることができ、MgをSn基合金半田に含有させることにより、Sn基合金半田の変色を抑制できる。 In addition, in this solar cell interconnector, 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more are added to the Sn-based alloy solder. It may be. As a result, in the solar cell interconnector, the fatigue characteristics of the Sn-based alloy solder can be further improved by including any one of In, Sb, or two or more in the Sn-based alloy solder, and Mg can be improved. By containing the Sn-based alloy solder, discoloration of the Sn-based alloy solder can be suppressed.
　また、太陽電池用インターコネクタでは、0.0001～0.005［wt.%］のMg、0.0001～0.005［wt.%］のGe、0.001～0.1［wt.%］のPのうちいずれか、若しくはMg、Ge、Pのうち２つ以上を、総計で0.0001～0.1［wt.%］の範囲内で、Sn基合金半田に添加することにより、Sn基合金半田の変色を抑制できる。 In the solar cell interconnector, 0.0001 to 0.005 [wt.%] Mg, 0.0001 to 0.005 [wt.%] Ge, 0.001 to 0.1 [wt.%] P, or Mg, Ge By adding two or more of P to the Sn-based alloy solder within a total range of 0.0001 to 0.1 [wt.%], Discoloration of the Sn-based alloy solder can be suppressed.
　具体的に、この太陽電池用インターコネクタでは、Sn基合金半田に所定量のNiを含有させることにより、平角銅線の表面とSn基合金半田との界面に形成される金属間化合物相の厚みが1～3［μm］に形成されており、金属間化合物相の厚みを従来よりも薄く形成し得るとともに、厚みのばらつきを抑制し得、熱応力の集中を回避させることができる。 Specifically, in this solar cell interconnector, by adding a predetermined amount of Ni to the Sn-based alloy solder, the thickness of the intermetallic compound phase formed at the interface between the flat copper wire surface and the Sn-based alloy solder Is formed to be 1 to 3 [μm], and the thickness of the intermetallic compound phase can be made thinner than before, variation in thickness can be suppressed, and concentration of thermal stress can be avoided.
　また、太陽電池用インターコネクタでは、Sn基合金半田に所定量のNiを含有させることにより、金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面において接合界面1［mm］長あたり、直径0.3［μm］以上の大きさのボイドが50個以下となり、かつ、金属間化合物相の内部、若しくはその近傍において接合界面1［mm］長あたり、直径1［μm］以上の大きさのボイドが形成されていない構成となり、熱応力のボイド部分への集中を抑制して金属化合物相で亀裂が発生し難く、金属間化合物相内部での破壊を抑制し得るという優れた効果も得られる。 In addition, in a solar cell interconnector, by adding a predetermined amount of Ni to the Sn-based alloy solder, a bonding interface 1 [mm] inside the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder. 50 or less voids with a diameter of 0.3 [μm] or more per length, and a diameter of 1 [μm] or more per 1 [mm] length of the bonding interface in or near the intermetallic compound phase The void is not formed, the thermal stress is suppressed from concentrating on the void part, it is difficult for cracks to occur in the metal compound phase, and the excellent effect of suppressing the breakage inside the intermetallic compound phase is also possible can get.
　そして、このような太陽電池用インターコネクタを利用した太陽電池モジュールでは、光エネルギーを電気に変換する複数の太陽電池セルの電極部に本発明の太陽電池用インターコネクタを接合し、本発明の太陽電池用インターコネクタにより複数の太陽電池セルを直列配列することにより、熱応力の集中によって生じる太陽電池用インターコネクタの太陽電池セルからの剥離や、太陽電池用インターコネクタ内部での破壊を抑制できる太陽電池モジュールを実現し得る。 And in the solar cell module using such a solar cell interconnector, the solar cell interconnector of the present invention is joined to the electrode portions of a plurality of solar cells that convert light energy into electricity, and the solar cell of the present invention. By arranging a plurality of solar cells in series with a battery interconnector, the solar cell can be prevented from peeling off the solar cell interconnector due to the concentration of thermal stress and breaking inside the solar cell interconnector. A battery module can be realized.
　以下、実施例について説明する。純度99.9［％］で厚さ1.2［mm］の無酸素銅板(JIS C1020 1/2H材)を0.2［mm］に冷間圧延した銅板を幅1.5［mm］でスリット加工し、断面が0.2［mm］×1.5［mm］の平角銅線を作製した。次いで、この平角銅線を様々な半田組成を持つ溶融めっき浴に通し、目付量が片面20［μm］で平角銅線の表面にSn基合金半田を被覆させた太陽電池用インターコネクタを製造した。尚、試験は目付量が片面20［μm］の試験片で実施したが、一部の試験片に関しては、後述するように、更に詳細に性能を評価する目的で目付量が片面17［μm］という薄めっき品を同様に作製し、評価に使用した。用いためっき浴の半田組成を表１及び表２に示す。 Hereinafter, examples will be described. An oxygen-free copper plate (JIS C1020 1 / 2H material) with a purity of 99.9 [%] and cold-rolled to 0.2 [mm] is slit into a width of 1.5 [mm] and a cross-section of 0.2 [mm] A rectangular copper wire of [mm] × 1.5 [mm] was produced. Next, this rectangular copper wire was passed through a hot dipping bath having various solder compositions, and a solar cell interconnector in which the basis weight was 20 [μm] and the surface of the rectangular copper wire was coated with Sn-based alloy solder was manufactured. . The test was carried out on a test piece having a basis weight of 20 [μm] on one side, but some test pieces have a basis weight of 17 [μm] on one side for the purpose of evaluating the performance in more detail as will be described later. A thin plated product was prepared in the same manner and used for evaluation. Tables 1 and 2 show the solder compositions of the plating baths used.
　具体的には、実施例1～実施例6は、Niを0.01～0.2［wt.%］含有したSn-Pb-Ni系のSn基合金半田であり、実施例7～実施例12は、Niを0.01～0.2［wt.%］含有したSn-Ag-Ni系のSn基合金半田である。また、実施例13～実施例18は、Niを0.01～0.2［wt.%］含有したSn-Bi-Ni系のSn基合金半田であり、実施例19～実施例24は、Niを0.01～0.2［wt.%］含有したSn-Pb-2Ag-Ni系のSn基合金半田であり、実施例25～実施例30は、Niを0.01～0.2［wt.%］含有したSn-Cu-Ni系のSn基合金半田であり、実施例31は、Niを0.05［wt.%］含有したSn-Ag-Cu-Ni系のSn基合金半田であり、実施例32～実施例37は、Niを0.01～0.2［wt.%］含有したSn-Ag-Ni系でInを添加したSn基合金半田であり、実施例38～実施例43は、Niを0.01～0.2［wt.%］含有したSn-Ag-Ni系でSbを添加したSn基合金半田であり、実施例44～52は、Niを0.01～0.2［wt.%］含有したSn-Ag-Cu-Ni系で、Mg、Ge、Pのうちいずれか、若しくは２つ以上を添加したSn基合金半田である。実施例53は、Niを0.05［wt.%］含有したSn-Pb-Ni系で、Mg、Ge、Pを添加したSn基合金半田である。実施例54～57は、Niを0.1～0.2［wt.%］含有したSn-Pb-Ni系又はSn-Ag-Ni系のSn基合金半田であり、比較のため、特に浴温800［℃］で20分程保持することなく他の元素を添加したSn基合金半田である。 Specifically, Examples 1 to 6 are Sn—Pb—Ni-based Sn-based alloy solders containing Ni of 0.01 to 0.2 [wt.%], And Examples 7 to 12 are Ni Sn-Ag-Ni-based Sn-base alloy solder containing 0.01 to 0.2 wt. Examples 13 to 18 are Sn-Bi-Ni-based Sn-based alloy solders containing Ni in an amount of 0.01 to 0.2 [wt.%]. Examples 19 to 24 are Ni in an amount of 0.01 to 0.2%. Sn-Pb-2Ag-Ni-based Sn-based alloy solder containing 0.2 [wt.%] Examples 25 to 30 are Sn-Cu-Ni containing 0.01 to 0.2 [wt.%] Ni. Sn-Ag-Cu-Ni-based Sn-based alloy solder containing 0.05 [wt.%] Ni, and Example 32 to Example 37 are Ni-based Sn-based alloy solders. Sn-Ag-Ni based Sn-based alloy solder containing 0.01 to 0.2 [wt.%] And containing In, and Examples 38 to 43 contained 0.01 to 0.2 [wt.%] Of Ni Sn-Ag-Ni based Sn-based alloy solder with Sb added. Examples 44 to 52 are Sn-Ag-Cu-Ni based alloys containing 0.01 to 0.2 wt.% Ni, Mg, Ge , P or Sn based alloy solder added with two or more. Example 53 is a Sn—Pb—Ni system containing 0.05 [wt.%] Of Ni and Sn-based alloy solder to which Mg, Ge, and P are added. Examples 54 to 57 are Sn-Pb-Ni-based or Sn-Ag-Ni-based Sn-based alloy solders containing 0.1 to 0.2 [wt.%] Of Ni. ] Is an Sn-based alloy solder to which other elements are added without being held for about 20 minutes.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　Ni濃度が0.01～0.20［wt.%］の実施例1～実施例57の太陽電池用インターコネクタでは、Sn基合金半田となるめっき浴を作製する際、全ての添加元素を同時にSn浴中に添加するのではなく、Niのみを先にSn浴中に添加した後、他の元素（Pb,Ag,Bi,Cu,In,Sb,Mg,Ge,P）を添加した。また、Ni濃度が0.10［wt.%］及び0.20［wt.%］の実施例5,6,11,12,17,18,23,24,29,30,36,37,42,43,50,51の太陽電池用インターコネクタについては、更に、上述したNiのみが先に添加されたSn浴を、浴温800［℃］で20分程保持した後に他の元素を添加した。但し、比較のため、実施例54～57では、特に浴温800［℃］で20分程保持することなく、Sn浴に他の元素を添加した。また、比較例1～比較例18の各Sn基合金半田も、Sn浴中にNiのみを先に添加し、その後、他の元素を添加して作製した。 In the interconnector for solar cells of Examples 1 to 57 where the Ni concentration is 0.01 to 0.20 [wt.%], When preparing a plating bath to be an Sn-based alloy solder, all additive elements are simultaneously contained in the Sn bath. Instead of adding, only Ni was first added to the Sn bath, and then other elements (Pb, Ag, Bi, Cu, In, Sb, Mg, Ge, P) were added. Further, Examples 5, 6, 11, 12, 17, 18, 23, 24, 29, 30, 36, 37, 42, 43, 50 with Ni concentrations of 0.10 [wt.%] And 0.20 [wt.%] In addition, for the interconnector for solar cells of No. 51, another element was added after the Sn bath to which only Ni described above was added was held at a bath temperature of 800 ° C. for about 20 minutes. However, for comparison, in Examples 54 to 57, other elements were added to the Sn bath without particularly maintaining the bath temperature at 800 [° C.] for about 20 minutes. In addition, each Sn-based alloy solder of Comparative Examples 1 to 18 was prepared by adding only Ni to the Sn bath first, and then adding other elements.
　溶融めっきは、ボビンから繰り出した平角銅線を、N2-5体積％H2混合ガスを通気させて600［℃］に過熱した管状炉内を通線させることで、外気に触れさせることなく予備加熱した後、250［℃］に保持されためっき槽内を通線することで実施した。Sn基合金半田で表面が被覆された平角銅線はボビンに巻き取った。Sn基合金半田の目付量は、めっき浴の液面から出線する平角銅線に向けて、めっき浴上方に設けたワイピングノズルからアルゴンガスを吹き付け、そのガスの流量を制御することで調整した。 In hot dipping, a rectangular copper wire drawn out from a bobbin is passed through a tubular furnace heated to 600 [° C] by aeration of N 2 -5% by volume H 2 mixed gas, without touching the outside air. After pre-heating, it was carried out by passing through the inside of the plating tank maintained at 250 [° C.]. A flat copper wire whose surface was coated with Sn-based alloy solder was wound around a bobbin. The basis weight of the Sn-based alloy solder was adjusted by blowing argon gas from the wiping nozzle provided above the plating bath toward the flat copper wire coming out from the surface of the plating bath and controlling the gas flow rate. .
　そして、Sn基合金半田表面の酸化の程度を光学顕微鏡で観察した。その際、Sn基合金半田の表面が銀白色であれば、Sn基合金半田の表面が酸化されていないとして表１及び表２中の「酸化」の欄を○印で示し、黄色や赤色等に変色していれば、Sn基合金半田の表面が酸化されたと判断して表１及び表２中の「酸化」の欄を×印で示した。また、Sn基合金半田の表面が銀白色に観察されたものは、加速試験として更に125［℃］に保持された大気炉中で30時間の加熱を行った後に、Sn基合金半田の表面を観察した。その結果、Sn基合金半田の表面の変色が表面積の50［%］以下にとどまれば概ね良好として「酸化」の欄を○印のままとし、Sn基合金半田の変色が表面積の30［%］以下にとどまれば良好として「酸化」の欄を◎印とし、Sn基合金半田の変色が表面積の15［%］以下にとどまれば良好として「酸化」の欄を◎○印とし、Sn基合金半田の表面に変色が見られなければ極めて良好として「酸化」の欄を◎◎印とした。尚、この加速加熱試験は試験片の優劣を試験的に見極めるための極めて極端な条件である。表１及び表２中の実施例44～53の結果から、更に0.0001～0.005［wt.%］のMg、0.0001～0.005［wt.%］のGe、0.001～0.1［wt.%］のPのうちいずれか、若しくは２つ以上をSn基合金半田に添加することにより、Sn基合金半田の変色を抑制できることが確認できた。一方、比較例16～18のようにMgを0.1［wt.%］、Geを0.1［wt.%］、Pを0.2［wt.%］と過剰に添加すると、Sn基合金半田表面の酸化が激しくなってしまった。 Then, the degree of oxidation of the Sn-based alloy solder surface was observed with an optical microscope. At that time, if the surface of the Sn-based alloy solder is silver white, the “oxidation” column in Tables 1 and 2 is indicated by a circle, indicating that the surface of the Sn-based alloy solder is not oxidized, yellow, red, etc. If it is discolored, it is judged that the surface of the Sn-based alloy solder has been oxidized, and the “oxidation” column in Tables 1 and 2 is indicated by x. In addition, when the surface of the Sn-based alloy solder was observed to be silver white, the surface of the Sn-based alloy solder was further heated for 30 hours in an atmospheric furnace maintained at 125 [° C.] as an acceleration test. Observed. As a result, if the surface discoloration of the Sn-based alloy solder stays below 50 [%] of the surface area, the “Oxidation” column is left as ○, and the discoloration of the Sn-based alloy solder is 30 [%] of the surface area. If it stays below, the "Oxidation" column is marked with ◎, and if the discoloration of the Sn-based alloy solder stays below 15% of the surface area, the "oxidation" column is marked with ◎ ○, and the Sn-based alloy solder If no discoloration was observed on the surface of the film, it was marked as excellent, and the “oxidation” column was marked with ◎ Note that this accelerated heating test is an extremely extreme condition for experimentally determining the superiority or inferiority of the test piece. From the results of Examples 44 to 53 in Tables 1 and 2, 0.0001 to 0.005 [wt.%] Mg, 0.0001 to 0.005 [wt.%] Ge, 0.001 to 0.1 [wt.%] P It was confirmed that discoloration of the Sn-based alloy solder can be suppressed by adding one or more of them to the Sn-based alloy solder. On the other hand, when Mg is added in an amount of 0.1 [wt.%], Ge is 0.1 [wt.%], And P is 0.2 [wt.%] As in Comparative Examples 16 to 18, oxidation of the Sn-based alloy solder surface occurs. It has become intense.
　次に、Sn基合金半田の表面における酸化被膜層の種類と、Snの粒界におけるPの偏析の有無、並びに、Sn基合金半田と平角銅線との界面に形成される金属間化合物相の種類と、その厚みとを調べた。まず、試験片を機械研磨で断面研磨した後に、FE-SEMでSn基合金半田の研摩断面を観察した。その結果、Sn基合金半田の研摩断面を微結晶層が覆っていれば「酸化被膜」の欄に「微結晶」と示し、微結晶層と結晶層とが混在していれば「酸化被膜」の欄に「微結晶+結晶」と示し、Snの粒界にPが偏析していれば「酸化被膜」の欄に「P」と示し、Sn基合金半田の研摩断面の面積の半分を超えて結晶層が覆っていれば「酸化被膜」の欄に「結晶」と示した。同様にFE-SEMで金属間化合物相を観察して厚みを測定した後、その金属間化合物相の回折パターンをTEMの電子回折パターンから得て種類を同定した。金属間化合物相に（Cu,Ni）6Sn5及び又は（Cu,Ni）3Snが含まれていれば、表１及び表２中の「合金層の種類」の欄に「（Cu,Ni）6Sn5 （Cu,Ni）3Sn」と示し、一方、金属間化合物相にCu6Sn5が含まれていれば、表１及び表２中の「合金層の種類」の欄に「Cu6Sn5」と示した。尚、FE-SEM観察時の加速電圧を20[kV]とした。 Next, the type of oxide film layer on the surface of the Sn-based alloy solder, the presence or absence of P segregation at the Sn grain boundaries, and the intermetallic compound phase formed at the interface between the Sn-based alloy solder and the rectangular copper wire The type and its thickness were examined. First, the cross section of the test piece was mechanically polished, and then the polished cross section of the Sn-based alloy solder was observed with FE-SEM. As a result, if the microcrystalline layer covers the polished cross section of the Sn-based alloy solder, "Oxide film" is displayed in the "Oxide film" column, and if the microcrystalline layer and the crystalline layer are mixed, "Oxide film""Microcrystal + crystal" is indicated in the column, and if P is segregated at the grain boundaries of Sn, it is indicated as "P" in the "Oxide film" column, exceeding half of the area of the polished cross section of the Sn-based alloy solder. If the crystal layer is covered, “crystal” is indicated in the column of “oxide film”. Similarly, after observing the intermetallic compound phase with FE-SEM and measuring the thickness, the diffraction pattern of the intermetallic compound phase was obtained from the electron diffraction pattern of TEM to identify the type. If (Cu, Ni) 6 Sn 5 and / or (Cu, Ni) 3 Sn is contained in the intermetallic compound phase, “(Cu, Ni) in the column of“ type of alloy layer ”in Tables 1 and 2 ) 6 Sn 5 (Cu, Ni) 3 Sn ”, on the other hand, if Cu 6 Sn 5 is included in the intermetallic compound phase, the“ type of alloy layer ”column in Table 1 and Table 2 Cu 6 Sn 5 ". The acceleration voltage during FE-SEM observation was set to 20 [kV].
　TEMにより観察する薄膜試料はFIB(Focused Ion Beam)で切り出し加工を行うことで得、TEM観察時の加速電圧を100[kV]とした。表１から、Niを0.01～0.2［wt.%］含有した実施例1～実施例53では、いずれも（Cu,Ni）6Sn5及び又は（Cu,Ni）3Snでなる金属間化合物相が確認できた。一方、実施例54～57では、本願の格別な製法（Niのみを先に添加したSn浴を、浴温800［℃］で所定時間保持した後に他の元素を添加する製法）を用いなかったため、（Cu,Ni）6Sn5を含むものの、Cu6Sn5やCu3Snも一部含んでいた。また、上述したように「Niのみを先に添加したSn浴を、浴温800［℃］で所定時間保持した後に他の元素を添加する製法」を用いた実施例1～実施例53では、いずれのSn基合金半田においても、金属間化合物相の膜厚が1～3［μm］となり、従来よりも膜厚が薄く形成できることが確認でき、さらに、金属間化合物相の厚みのばらつきが抑制されていることが確認できた。 The thin film sample to be observed by TEM was obtained by cutting and processing with FIB (Focused Ion Beam), and the acceleration voltage at the time of TEM observation was set to 100 [kV]. From Table 1, in Examples 1 to 53 containing Ni in an amount of 0.01 to 0.2 [wt.%], The intermetallic compound phase is composed of (Cu, Ni) 6 Sn 5 and / or (Cu, Ni) 3 Sn. Was confirmed. On the other hand, in Examples 54 to 57, the special manufacturing method of the present application (a manufacturing method in which a Sn bath in which only Ni was added first was held at a bath temperature of 800 [° C.] for a predetermined time and then other elements were added) was not used. , (Cu, Ni) 6 Sn 5 , but some Cu 6 Sn 5 and Cu 3 Sn were also included. Further, as described above, in Examples 1 to 53 using the “production method of adding another element after holding a Sn bath to which only Ni has been added first, at a bath temperature of 800 ° C.” for a predetermined time, In any Sn-based alloy solder, the film thickness of the intermetallic compound phase is 1 to 3 [μm], confirming that the film thickness can be made thinner than before, and further suppressing variation in the thickness of the intermetallic compound phase It has been confirmed that.
　Sn基合金半田中のボイドの観察は、X線透過観察装置で1［mm］長を観察し、その観察結果を表１及び表２中の「ボイド」の欄に示した。ここで、表１及び表２中の「ボイド」の欄では、直径0.3［μm］以上の大きさのボイドが金属間化合物相の内部、若しくはその近傍（金属間化合物とSn基合金半田との界面）にて、接合界面（平角銅線の表面と接合している界面）1［mm］長あたり50個超生じていればXと示し、一方、直径1［μm］以上の大きさのボイドが金属間化合物相の内部、若しくは金属間化合物とSn基合金半田との界面にて、接合界面1［mm］長あたり1個以上生じていればYと示し、XとYの両者とも合致すればX+Yと示し、XとYのいずれも観察されなければAと示した。表１及び表２から、Niを0.01～0.2［wt.%］含有した実施例1～実施例57では、ボイドに関して、いずれも上記XとYが観察されず、熱応力のボイド部分への集中を抑制し得る金属間化合物相が形成できることが確認できた。 In the observation of voids in the Sn-based alloy solder, the length of 1 [mm] was observed with an X-ray transmission observation apparatus, and the observation results are shown in the “void” column in Tables 1 and 2. Here, in the “Void” column in Tables 1 and 2, a void having a diameter of 0.3 [μm] or more is present in the vicinity of the intermetallic compound phase or in the vicinity thereof (intermetallic compound and Sn-based alloy solder. In the case of more than 50 bonding points per 1 [mm] length, it is indicated as X. On the other hand, a void with a diameter of 1 [μm] or more Is indicated as Y if there is at least one bond per 1 mm in the intermetallic compound phase or at the interface between the intermetallic compound and the Sn-based alloy solder, and both X and Y match. X + Y, and A if no X or Y was observed. From Tables 1 and 2, in Examples 1 to 57 containing 0.01 to 0.2 [wt.%] Of Ni, neither X nor Y was observed for the voids, and the thermal stress was concentrated on the void part. It was confirmed that an intermetallic compound phase capable of suppressing the above could be formed.
　次に、実施例1～実施例57、及び比較例1～比較例18の組成からなるSn基合金半田で平角銅線の表面を被覆した各太陽電池用インターコネクタを、太陽電池セルに接合し、このときの接合状態について調べた。太陽電池セルと太陽電池用インターコネクタとを接続した、いわゆるストリングスを形成する工程は、（株）エヌ・ピー・シー社製の自動配線装置を使用した。尚、この自動配線装置は、Sn基合金半田をリフローして太陽電池セルと太陽電池用インターコネクタとを接合する装置であり、予熱したセルテーブル状の太陽電池セルに太陽電池用インターコネクタを配置し、ピンで抑えてホットエアを吹き付けて太陽電池用インターコネクタの外表のSn基合金半田を溶融させ、太陽電池セルと太陽電池用インターコネクタとを接合し、太陽電池用インターコネクタによって太陽電池セルを3枚直列接続させたストリングスを作製する装置である。 Next, each solar cell interconnector whose flat copper wire surface was coated with an Sn-based alloy solder having the composition of Examples 1 to 57 and Comparative Examples 1 to 18 was joined to the solar cells. The bonding state at this time was examined. In the process of forming so-called strings in which the solar cells and the solar cell interconnector are connected, an automatic wiring device manufactured by NPC Corporation was used. This automatic wiring device is a device that reflows Sn-based alloy solder to join the solar cells and the solar cell interconnector, and arranges the solar cell interconnector on the preheated cell-table solar cell. Then, press the pin with hot air to melt the Sn-base alloy solder on the outer surface of the solar cell interconnector, join the solar cell and the solar interconnector, and connect the solar cell with the solar interconnector. This is an apparatus for producing three strings connected in series.
　使用した太陽電池セルは、大きさ156×156［mm］、厚さ160［μm］の多結晶シリコンであり、集電用に設けた太陽電池用インターコネクタが配線される銀電極幅は2［mm］であり、平行に片面2本の電極が形成されているものを使用した。尚、比較のため、厚さ220［μm］の多結晶シリコンでなる太陽電池セルも使用して評価を行った（表２中の比較例5）。接合する温度は250［℃］とした。ホットエア設定温度はめっき浴の温度に110［℃］加えた温度で行った。ピン押さえ時間は3秒とした。 The solar cell used was polycrystalline silicon with a size of 156 x 156 [mm] and a thickness of 160 [μm], and the silver electrode width to which the solar cell interconnector provided for current collection was wired was 2 [ mm] in which two electrodes on one side are formed in parallel. For comparison, evaluation was also performed using a solar battery cell made of polycrystalline silicon having a thickness of 220 [μm] (Comparative Example 5 in Table 2). The joining temperature was 250 [° C.]. The hot air set temperature was 110 ° C. added to the temperature of the plating bath. The pin holding time was 3 seconds.
　接合されたストリングスの接合状態を評価した結果を表１及び表２の「ストリングス」の欄に示す。接合状態は、機械の動作停止、接合状態で評価した。表１及び表２中の「ストリングス」の欄では、ストリングスの形成はできたが、ハンドリング中に太陽電池用インターコネクタが太陽電池セルから部分的に剥離してしまったものの内、その後の断面研磨によって、太陽電池用インターコネクタのSn基合金半田（めっき層）と、太陽電池セル上の電極とが剥離していたことが確認できたものを××で示した。また、表１及び表２中の「ストリングス」の欄では、ストリングスの形成はできたがハンドリング中に太陽電池用インターコネクタが太陽電池セルから部分的に剥離してしまったものの内、その後の断面研磨によって太陽電池用インターコネクタ内部の金属間化合物相、若しくは金属間化合物とSn基合金半田との界面で破壊が生じていたことが確認できたものを×で示し、巨視的には健全で実使用上は問題ないものの、Sn基合金半田が濡れたことを示すフィレットが部分的に形成していないか、未接合の部分があるものを○で示し、フィレットが全体を通して形成され、健全に接合されたものを◎で示した。尚、本評価で◎であった半田組成に関しては、性能を更に詳細に評価するため、前述のように目付量が片面17［μm］という薄めっき品を用いて同様にストリングスの試験を実施した。その際、薄めっき品を用いてもフィレットが全体を通して形成され、健全に接合されたものをきわめて優秀として◎◎で示した。 The results of evaluating the joined state of the joined strings are shown in the “strings” column of Tables 1 and 2. The bonding state was evaluated based on the machine operation stop and bonding state. In the column of “Strings” in Tables 1 and 2, strings were formed, but the solar cell interconnector partially peeled off from the solar cells during handling, and the subsequent cross-sectional polishing XX indicates that the Sn-based alloy solder (plating layer) of the solar cell interconnector and the electrode on the solar cell were confirmed to be peeled. Moreover, in the column of “Strings” in Tables 1 and 2, the strings were formed, but the solar cell interconnector partially peeled off from the solar cells during handling. A cross indicates that destruction has occurred at the intermetallic compound phase inside the interconnector for solar cells or at the interface between the intermetallic compound and the Sn-based alloy solder. Although there is no problem in use, a fillet indicating that the Sn-based alloy solder has been wet is not partially formed or there is an unjoined portion, and a fillet is formed throughout and is joined firmly. What was done was shown by (double-circle). For the solder composition that was evaluated as ◎ in this evaluation, in order to evaluate the performance in more detail, the string test was similarly performed using a thin plating product having a basis weight of 17 [μm] on one side as described above. . At that time, even if a thin-plated product was used, fillets were formed throughout, and those that were joined soundly were marked as excellent.
　尚、太陽電池用インターコネクタ内部の金属間化合物相内部、若しくは金属間化合物とSn基合金半田との界面で破壊が生じているか否か、フィレットの形成有無は、光学顕微鏡並びにFE-SEMにより確認した。表１及び表２から、0.01～0.2［wt.%］の範囲でNiをSn基合金半田に含有させた実施例1～実施例57では、ストリングスの評価が○、◎又は◎◎となり、太陽電池用インターコネクタの金属間化合物相内部、若しくは金属間化合物とSn基合金半田との界面での破壊を抑制できていることが確認できた。 In addition, it is confirmed by optical microscope and FE-SEM whether or not the fracture occurs in the intermetallic compound phase inside the solar cell interconnector or at the interface between the intermetallic compound and the Sn-base alloy solder. did. From Tables 1 and 2, in Examples 1 to 57 in which Ni was contained in the Sn-based alloy solder in the range of 0.01 to 0.2 [wt.%], The string evaluation was ○, ◎, or ◎◎. It was confirmed that the breakage in the intermetallic compound phase of the battery interconnector or at the interface between the intermetallic compound and the Sn-based alloy solder could be suppressed.
　ここで、0.01［wt.%］又は0.03［wt.%］のNiを添加した実施例1,2,7,8ではストリングスの評価が○であった。一方、Sn-Pb-2Ag-Ni系、Sn-Cu-Ni系、Sn-Ag-In系やSn-Ag-Sb系である実施例19、25、32、38では、0.01［wt.%］のNiを添加した場合であってもストリングスの評価が◎となり、これらの系でストリングスの評価が良くなることが確認できた。また、Sn-Bi-Ni系である実施例13～18や、Sn-Pb-2Ag-Ni系である実施例20～24や、Sn-Cu-Ni系である実施例26～30や、Sn-Ag-Cu-Ni系である実施例31や、Sn-Ag-Ni系に更にInを添加した実施例33～37や、Sn-Ag-Ni系に更にSbを添加した実施例39～43は、目付量が片面17［μm］という薄めっき品を用いた場合であってもストリングスの評価が◎◎となり、これらの系でストリングスの評価が益々良くなることが確認できた。但し、比較のため、特に浴温800［℃］で20分程保持することなく、Sn浴に他の元素を添加した実施例54～57では、0.10［wt.%］又は0.20［wt.%］のNiを添加してもストリングスの評価が○にとどまった。これは、前記の保持プロセスを施さなかったため、添加したNiの一部が消費されてしまったためと考えられる。 Here, in Examples 1, 2, 7, and 8 to which 0.01 [wt.%] Or 0.03 [wt.%] Ni was added, the evaluation of the strings was good. On the other hand, in Examples 19, 25, 32 and 38 which are Sn-Pb-2Ag-Ni, Sn-Cu-Ni, Sn-Ag-In and Sn-Ag-Sb, 0.01 [wt.%] Even when Ni was added, the evaluation of the strings was ◎, and it was confirmed that the evaluation of the strings was improved in these systems. In addition, Examples 13 to 18 that are Sn-Bi-Ni systems, Examples 20 to 24 that are Sn-Pb-2Ag-Ni systems, Examples 26 to 30 that are Sn-Cu-Ni systems, Sn -Ag-Cu-Ni-based Example 31; Sn-Ag-Ni-based Examples 33-37; and Sn-Ag-Ni-based Example 39-43 Even when a thin-plated product having a basis weight of 17 [μm] on one side was used, the evaluation of the strings was ◎, and it was confirmed that the evaluation of the strings was further improved in these systems. However, for comparison, in Examples 54 to 57 in which other elements were added to the Sn bath without particularly maintaining the bath temperature at 800 [° C.] for about 20 minutes, 0.10 [wt.%] Or 0.20 [wt.%] The evaluation of the strings remained ○ even when Ni was added. This is presumably because a part of the added Ni was consumed because the holding process was not performed.
　また、Niを0.30［wt.%］含有させた比較例2では、（Cu,Ni）6Sn5及び又は（Cu,Ni）3Snでなる金属間化合物相の形成が確認できたが、ストリングスの評価が××となり太陽電池セルの電極部との接合性不良が生じることが確認でき、Sn基合金半田に含有させるNiの含有量として0.20［wt.%］以下が望ましいことが確認できた。

  Further, in Comparative Example 2 containing Ni of 0.30 [wt.%], Formation of an intermetallic compound phase composed of (Cu, Ni) 6 Sn 5 and / or (Cu, Ni) 3 Sn was confirmed. It was confirmed that the evaluation of XX became poor adhesion to the electrode part of the solar battery cell, and it was confirmed that the content of Ni contained in the Sn-based alloy solder is preferably 0.20 [wt.%] Or less .

Claims (4)

  1. 　50［wt.%］以上のSn、及び0.01～0.2［wt.%］のNiを含有し、更に30～45［wt.%］のPb、0.1～4［wt.%］のAg、0.1～3［wt.%］のBi、0.1～2［wt.%］のCuのいずれか、若しくは２つ以上、並びに不可避不純物を含有するSn基合金半田で、平角銅線の表面が被覆されており、
    　前記平角銅線と前記Sn基合金半田との界面に、金属間化合物相として(Cu,Ni)6Sn5又は(Cu,Ni)3Snのいずれか、若しくは両方が存在する
    　ことを特徴とする太陽電池用インターコネクタ。     Containing 50 [wt.%] Or more of Sn, 0.01 to 0.2 [wt.%] Ni, 30 to 45 [wt.%] Pb, 0.1 to 4 [wt.%] Ag, 0.1 to The surface of a rectangular copper wire is coated with Sn based alloy solder containing 3 [wt.%] Bi, 0.1 to 2 [wt.%] Cu, or two or more, and inevitable impurities. ,
    One or both of (Cu, Ni) 6 Sn 5 and (Cu, Ni) 3 Sn exist as an intermetallic compound phase at the interface between the rectangular copper wire and the Sn-based alloy solder. Solar cell interconnector.
  2. 　更に0.1～3［wt.%］のIn、0.1～2［wt.%］のSbのいずれか、若しくは２つ以上が、前記Sn基合金半田に添加されている
    　ことを特徴とする請求項１記載の太陽電池用インターコネクタ。     Further, any one or more of 0.1 to 3 [wt.%] In, 0.1 to 2 [wt.%] Sb, or two or more thereof is added to the Sn-based alloy solder. The interconnector for solar cells described.
  3. 　更に0.0001～0.005［wt.%］のMg、0.0001～0.005［wt.%］のGe、0.001～0.1［wt.%］のPのいずれか、若しくは２つ以上が総計で0.0001～0.1［wt.%］の範囲で、前記Sn基合金半田に添加されている
    　ことを特徴とする請求項１又は請求項２記載の太陽電池用インターコネクタ。     Furthermore, 0.0001 to 0.005 [wt.%] Mg, 0.0001 to 0.005 [wt.%] Ge, 0.001 to 0.1 [wt.%] P, or a total of two or more 0.0001 to 0.1 [wt.%]. %] Is added to the Sn-based alloy solder. The solar cell interconnector according to claim 1, wherein the Sn-base alloy solder is added.
  4. 　請求項１～３のいずれかに記載の太陽電池用インターコネクタで太陽電池セルを直列配列した
    　ことを特徴とする太陽電池モジュール。     4. A solar cell module comprising solar cells interconnected in series by the solar cell interconnector according to claim 1.
PCT/JP2015/051421 2014-01-24 2015-01-20 Solar-cell interconnector and solar cell module WO2015111587A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2015559075A JPWO2015111587A1 (en) 2014-01-24 2015-01-20 Solar cell interconnector and solar cell module
TW104102352A TW201535759A (en) 2014-01-24 2015-01-23 Solar-cell interconnector and solar cell module

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2014010921 2014-01-24
JP2014-010921 2014-01-24

Publications (1)

Publication Number Publication Date
WO2015111587A1 true WO2015111587A1 (en) 2015-07-30

Family

ID=53681390

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2015/051421 WO2015111587A1 (en) 2014-01-24 2015-01-20 Solar-cell interconnector and solar cell module

Country Status (3)

Country Link
JP (1) JPWO2015111587A1 (en)
TW (1) TW201535759A (en)
WO (1) WO2015111587A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017101436A1 (en) * 2015-12-18 2017-06-22 王能青 Alloy solder, and preparation method therefor and use thereof
JP2017147460A (en) * 2017-04-17 2017-08-24 三菱電機株式会社 Solar cell module
JP2018001179A (en) * 2016-06-28 2018-01-11 株式会社タムラ製作所 Lead-free solder alloy, electronic circuit board and electronic control device
JP2019195849A (en) * 2016-06-28 2019-11-14 株式会社タムラ製作所 Lead-free solder alloy, electronic circuit substrate, and electronic controller
EP3597356A4 (en) * 2017-12-31 2020-06-03 Senju Metal Industry Co., Ltd Solder alloy

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108274147A (en) * 2017-12-22 2018-07-13 占卫君 A kind of efficient cryogenic welding, preparation method and photovoltaic module
CN108555472B (en) * 2017-12-29 2020-12-01 西安泰力松新材料股份有限公司 Photovoltaic solder strip alloy solder and preparation method thereof
CN108788511A (en) * 2018-06-25 2018-11-13 深圳市博士达焊锡制品有限公司 It is a kind of to have kupper solder and preparation method thereof with high anti-oxidation ability

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003230980A (en) * 2002-02-14 2003-08-19 Nippon Steel Corp Leadless solder alloy, solder ball and electronic member having solder bump
JP2011005542A (en) * 2009-06-23 2011-01-13 Nihon Superior Co Ltd In-CONTAINING LEAD-FREE SOLDER ALLOY, AND SOLDERED JOINT USING THE SOLDER
WO2011115305A1 (en) * 2010-03-17 2011-09-22 新日本製鐵株式会社 Metal tape material, and interconnector for solar cell collector
WO2012133598A1 (en) * 2011-03-28 2012-10-04 千住金属工業株式会社 Lead-free solder ball
WO2012165348A1 (en) * 2011-05-27 2012-12-06 新日鐵住金株式会社 Interconnector for solar cells, and solar cell module
JP2013065728A (en) * 2011-09-17 2013-04-11 Nippon Joint Kk Ceramic electronic component and manufacturing method therefor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003230980A (en) * 2002-02-14 2003-08-19 Nippon Steel Corp Leadless solder alloy, solder ball and electronic member having solder bump
JP2011005542A (en) * 2009-06-23 2011-01-13 Nihon Superior Co Ltd In-CONTAINING LEAD-FREE SOLDER ALLOY, AND SOLDERED JOINT USING THE SOLDER
WO2011115305A1 (en) * 2010-03-17 2011-09-22 新日本製鐵株式会社 Metal tape material, and interconnector for solar cell collector
WO2012133598A1 (en) * 2011-03-28 2012-10-04 千住金属工業株式会社 Lead-free solder ball
WO2012165348A1 (en) * 2011-05-27 2012-12-06 新日鐵住金株式会社 Interconnector for solar cells, and solar cell module
JP2013065728A (en) * 2011-09-17 2013-04-11 Nippon Joint Kk Ceramic electronic component and manufacturing method therefor

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017101436A1 (en) * 2015-12-18 2017-06-22 王能青 Alloy solder, and preparation method therefor and use thereof
JP2018001179A (en) * 2016-06-28 2018-01-11 株式会社タムラ製作所 Lead-free solder alloy, electronic circuit board and electronic control device
JP2019195849A (en) * 2016-06-28 2019-11-14 株式会社タムラ製作所 Lead-free solder alloy, electronic circuit substrate, and electronic controller
JP2017147460A (en) * 2017-04-17 2017-08-24 三菱電機株式会社 Solar cell module
EP3597356A4 (en) * 2017-12-31 2020-06-03 Senju Metal Industry Co., Ltd Solder alloy
US11123824B2 (en) 2017-12-31 2021-09-21 Senju Metal Industry Co., Ltd. Solder alloy

Also Published As

Publication number Publication date
TW201535759A (en) 2015-09-16
JPWO2015111587A1 (en) 2017-03-23

Similar Documents

Publication Publication Date Title
WO2015111587A1 (en) Solar-cell interconnector and solar cell module
JP4516154B1 (en) Cu-Mg-P copper alloy strip and method for producing the same
JP4563508B1 (en) Cu-Mg-P-based copper alloy strip and method for producing the same
JP5054160B2 (en) Cu-Mg-P-based copper alloy strip and method for producing the same
WO2016031654A1 (en) Conductive material for connection parts which has excellent minute slide wear resistance
WO2015020054A1 (en) Electrically conductive aluminum alloy plate and method for manufacturing same
JP5073386B2 (en) ELECTRODE WIRE FOR SOLAR CELL, ITS SUBSTRATE, AND METHOD FOR PRODUCING SUBSTRATE
JP5036545B2 (en) Method for producing electrode wire for solar cell
KR20150070201A (en) Aluminium alloy foil
WO2018079507A1 (en) Copper alloy sheet and method for manufacturing same
JP5499330B2 (en) Solar cell bus bar
JP5652369B2 (en) Solar cell conductor
JP4154100B2 (en) Copper alloy for electronic materials having excellent surface characteristics and method for producing the same
JP6927844B2 (en) Copper alloy plate material and its manufacturing method
JP2008169461A (en) Solder plated wire for solar battery and method for producing the same
JP6858532B2 (en) Copper alloy plate material and its manufacturing method
CN111051546B (en) Insulating substrate and method for manufacturing same
TW202129021A (en) Copper alloy, copper alloy plastic working material, component for electronic/electrical equipment, terminal, busbar, and heat-diffusing substrate
JP2016044358A (en) Conductive material for connection part excellent in minute slide abrasion resistance
US9960289B2 (en) Solder joint material and method of manufacturing the same, soldering member and solar cell module
JP5367271B2 (en) Rolled plate
JP2014210955A (en) Copper alloy tinned material for solar cell module connector and junction box prepared using the same
JP2001131657A (en) Copper alloy for electrical and electronic parts
JP4798942B2 (en) Copper alloy for electrical and electronic parts
KR102343189B1 (en) Insulation substrate and method for manufacturing the same

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15740020

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2015559075

Country of ref document: JP

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15740020

Country of ref document: EP

Kind code of ref document: A1