Development of technology for obtaining electrodes based on copper wire using in the manufacture of solar modules Chimica Techno Acta LETTER published by Ural Federal University 2022, vol. 9(2), No. 202292S1 eISSN 2411-1414; chimicatechnoacta.ru DOI: 10.15826/chimtech.2022.9.2.S1 1 of 4 Development of technology for obtaining electrodes based on copper wire used in the manufacture of solar modules M.S. Illarionova * , K.Yu. Ivanova , M.V. Kuzmin , A.O. Patianova , V.L. Semenov Chuvash State University named after I. N. Ulyanov, 428015 Cheboksary, Russia * Corresponding authors: illarionovamarina1995@mail.ru This paper belongs to the MOSM2021 Special Issue. © 2021, The Authors. This article is published in open access form under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Abstract To optimize the technological process of manufacturing copper wire coated with solder of the POIN-52 brand, the optimal modes for the tinning temperature, linear velocity, diameter of the diamond die and flux were identified. It was found that the best wire tinning pro- cess is achieved when cleaning the surface of a copper wire by the method of electrochemical degreasing. The results of the tests showed that, in terms of mechanical and electrical parameters wire meets the requirements for electrodes in the manufacture of solar modules. The results of climatic tests of solar modules showed a high degree of reliability with a power loss of 0.86% and thermal cycling tests with a power loss of 0.4%, which is within tolerance. Keywords smart wire connection technology POIN-52 brand tin-indium alloy copper wire mechanical and electrical parameters solar module Received: 09.11.2021 Revised: 01.12.2021 Accepted: 28.03.2022 Available online: 31.03.2022 1. Introduction In modern conditions of the Russian economy develop- ment, one of the most important tasks is implementing the import substitution for reducing the cost of manu- factured products. This issue is also relevant in the field of alternative energy sources, i.e. in the transition from non-renewable to renewable energy sources [1, 2]. It is known that photovoltaic solar modules are manufac- tured using Smart Wire Connection Technology (SWCT). On both surfaces of the photovoltaic cells, a film-wire electrode is glued, which consists of a wire and a film for the electrode. Using a film-wire electrode, photovol- taic cells are connected in series [3]. One of the important tasks of increasing the effi- ciency of photovoltaic solar modules is the search and development of new electrodes that provide high relia- bility of contact with crystalline silicon, as well as charge transfer in the cell [4]. Tinned copper wire, which is currently one of the main materials in electri- cal engineering, is widely used as conductive elec- trodes. The use of tinned copper wire ensures the relia- bility and protection of solar modules from any external influences and, as a result, increases the durability of the product itself [5]. The use of low-melting solder on the surface of the copper wire makes it possible to ob- tain reliable electrical contact with the siver-containing contact grid, which helps to reduce the ohmic resistance between the photovoltaic cells [6]. 2. Experimental As a rule, tinning in the manufacture of wire is per- formed by the galvanic method. However, practice has shown that the necessary qualities of electrodes are achieved via hot tinning [7]. The continuity of the elec- trode contact with monocrystalline silicon directly de- pends on the surface quality of the tinned wire and the thickness of the solder based on the POIN-52 alloy, which ultimately affects the efficiency of transferring the con- verted light energy into electricity [8]. In accordance with the requirements of the normative and technical documentation, hot tinning on the coating of copper wire of MT 0.25 brand with POIN-52 brand solder was carried out on a hot tinning unit. At the first stage, we prepared the surface of the cop- per wire in order to remove oxides from the surface. We used the electrochemical degreasing to prepare the sur- face of the wire. The initial parameters of the wire were as follows: diameter – 0.25±0.001 mm; elongation – http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.S1 mailto:illarionovamarina1995@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-4893-7746 https://orcid.org/0000-0001-5982-0570 https://orcid.org/0000-0003-3880-9510 https://orcid.org/0000-0002-9785-4058 https://orcid.org/0000-0002-9869-6602 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.S1&domain=pdf&date_stamp=2022-3-31 Chimica Techno Acta 2022, vol. 9(2), No. 202292S1 LETTER 2 of 4 25%; specific electrical resistance – 0.016710–6 Ohmm2. Wire degreasing parameters are shown in Table 1. Hot tinning was carried out using flux deposition technology. A composition developed by a team of au- thors in work [9, 10] was used as a flux. The technologi- cal modes of hot tinning are given in Table 2. During the coating process, it was found that the wire stretches slightly. The coating of the wire is even, smooth, shiny, the quality of adhesion is satisfactory. 3. Results and Discussion We experimentally studied the possibility of using wire as electrodes using SWCT technology in the manufac- ture of solar modules. Reliability tests of soldering joints were carried out by testing for exposure to high humidity at high temperature and by thermal cycling. The results of the tests showed that, according to me- chanical and electrical parameters, the wire coated with solder of the POINT-52 brand meets the requirements for electrodes in the manufacture of solar modules. The results of climatic tests of solar modules for exposure to high humidity at high temperature showed a high de- gree of reliability with a power loss of 0.86% and thermal cycling tests with a power loss of 0.4%, which is within tolerance. Mechanical and electrical parameters of tinned wire are presented in Table 3. The data in Table 3 show that the mechanical parame- ters (mechanical strength and relative elongation) and electrical parameters (electrical resistance to direct cur- rent and specific electrical resistance) are within the spec- ified tolerance ranges or within the normal range. The design parameters of the copper wire coated with POIN-52 alloy is presented in Table 4. The thickness of the coating was determined by metallographic method according to clause 3.14 of G OST 9.302-88 Unified system of protection against corrosion and aging (ESZKS). Metallic and non-metallic inorganic coatings. Control methods (as amended). Data analysis Table 3 and 4 indicates that the most optimal character- istics are obtained with technological mode No. 2. The obtained sample of tinned wire is recommended as a current conducting electrode in the manufacture of solar modules using SWCT technology. At the next stage we carried out climatic tests of so- lar modules in order to determine the possibility of us- ing tinned wire coated with POIN-52 alloy according to IEC 61215-1: 2016 “Photovoltaic modules. Assessment of compliance with technical requirements. Test require- ments". Two different climatic tests were performed. The first test method involves exposure to high humidi- ty at high temperatures. The test conditions are pre- sented in Table 5. The results of the tests are presented in Table 6. Table 6 shows that the power loss was 2.71 watts or 0.86%. The photo of the electroluminescence of the module at the end of the tests is shown in Fig. 1. Fig. 1 Photo of the electroluminescence of the module at the end of the tests The second method of climate testing involves thermal cycling. The test conditions are presented in Table 7. The results of the tests are presented in Table 8. Ta- ble 8 shows that the power loss was 1.29 W, or 0.4%. The photo of the electroluminescence of the module at the end of the tests is shown in Fig. 2. Table 1 Technological mode of electrochemical degreasing Brand and nominal diame- ter of copper wire, mm Degreasing solution Тemperature, °С Electric current, А Speed, m/min Wire diameter after degreasing, mm ММ 0.25±0.001 TG-19 38 20 50 0.25±0.001 Table 2 Technological mode of wire coating with POIN-52 solder Mode Copper wire diameter according to tech- nical specifications Copper wire brand and ac- tual diameter, mm Melt temperature, °С Linear Velocity, m/min Diamond die diameter, mm 1 1.0 1.025.0 + − МТ 003.0 001.025.0 + − 130 130 0.265 2 1.0 1.025.0 + − МТ 003.0 001.025.0 + − 150 100 0.265 3 1.0 1.025.0 + − МТ 003.0 001.025.0 + − 175 105 0.278 Chimica Techno Acta 2022, vol. 9(2), No. 202292S1 LETTER 3 of 4 Table 3 Mechanical and electrical parameters of copper wire coated with POIN-52 solder Tensile strength, Н/ mm 2 Relative extension, % Specific electrical resistance to direct current at tempera- ture 20 °С, Ohm× mm 2/m Electrical resistance to di- rect current at temperature 20 °С, Ohm/m standard 1 2 3 standard 1 2 3 standard 1 2 3 standard 1 2 3 2 0 0 -2 9 0 2 4 3 2 2 0 2 4 0 2 5 ± 1 5 2 5 2 1 2 1 0 ,0 1 7 ± 0 .0 0 2 0 .0 1 8 0 .0 1 9 0 .0 1 7 0 .3 5 ± 0 .0 3 0 .3 5 0 .3 5 0 .3 5 Table 4 Design parameters of copper wire coated with POIN-52 solder Wire diameter, mm Wire coating thickness, micron standard 1 2 3 standard 1 2 3 0.25±0.010 0.257 0.257 0.250 5.1 0.15.3 + − 3.8 4.5 ˂1.0 (≈0.8) Table 5 High humidity / high temperature test conditions Exposure in the climate chamber Exposure time, hours Temperature, °С Relative humidity, % Frequency of unloading for testing, days Exposure conditions 1000 85±2 85±5 7 Table 6 Test results of volt-ampere characteristics before and after the tests WEEK Pmax, Watt Vpmax, V Ipmax, А Voc, V Isc, А Rs, Ohm Rsh, Ohm FF, % Eta, % 0 (loading) 317.354 36.33 8.74 43.87 9.25 0.46 687.7 78.20 19.00 6 (discharge) 314.64 36.21 8.69 43.80 9.21 0.46 666.8 77.97 18.84 Table 7 Test conditions by thermal cycling Exposure in the climate chamber Number of cycles Cycle duration, hours Frequency of unloading for tests, cycles 200 6 40 Exposure conditions Temperature, °С Relative humidity, % at the top point at the bottom point at the top point at the bottom point 85±2 –40±1 – – Table 8 Test results of volt-ampere characteristics before and after the tests Series Pmax, Watt Vpmax, V Ipmax, А Voc, V Isc, А Rs, Ohm Rsh, Ohm FF, % Eta, % 0 (loading) 316.76 36.26 8.74 43.88 9.26 0.461 537.7 77.97 18.97 200 (discharge) 315.47 36.19 8.72 43.89 9.24 0.473 546.2 77.83 18.89 Fig. 2 Photo of the electroluminescence of the module at the end of the thermal cycling tests 4. Conclusions The technological modes of hot tinning of copper wire with the POIN-52 alloy considered in this work with the identification of optimal conditions for the tinning tem- perature, linear velocity and diameter of the diamond drawing allow us to confirm the reliability of the contact electrode with the connecting busbar of solar modules. It is confirmed by the successfully conducted climatic tests of the solar modules by the thermal cycling methods and the method of exposure to high humidity at high tempera- ture. The results of the climatic tests of solar modules comply with the requirements of regulatory and technical documentation and vary within the tolerance ranges. Supplementary materials No supplementary data are available. Chimica Techno Acta 2022, vol. 9(2), No. 202292S1 LETTER 4 of 4 Funding The research was carried out by Chuvash state University within the implementation of a comprehensive project under the contract No. 2019/0837/1202–19 dated Septem- ber 19, 2019 with the financial support of the Ministry of Edu- cation and Science of Russia under the Agreement No. 075-11- 2019-047 dated November 25, 2019 and Russian Foundation for Basic Research (RFBR, https://www.rfbr.ru/rffi/eng), pro- ject No. 20-33-90269. Acknowledgments None. Author contributions Conceptualization: M.S. I., K.Yu.I., A.O.P., M.V.K. Data curation: M.V.K. Formal Analysis: K.Yu.I., A.O.P. Funding acquisition: M.V.K., V.L.S. Investigation: M.S. I., K.Yu.I., A.O.P. Methodology: M.V.K., V.L.S. Project administration: M.V.K., V.L.S. Resources: M.S. I., K.Yu.I., A.O.P. Software: M.V.K., V.L.S. Supervision: M.V.K., V.L.S. Validation: M.V.K., V.L.S. Visualization: K.Yu.I., A.O.P. Writing – original draft: M.S. I., K.Yu.I., A.O.P. Writing – review & editing: M.V.K., V.L.S. Conflict of interest The authors declare no conflict of interest. Additional information Authors’ Ids: Illarionova, Marina S., Scopus ID 57203511906; Ivanova, Kristina Yu., Scopus ID 57222369362; Kuzmin, Mikhail V., Scopus ID 55758896300. Patianova Alice O., Scopus ID 57202283653 Semenov Vladislav L., Scopus ID 57190025583 Website of Chuvash State University named after I.N. Ulyanova https://www.chuvsu.ru. References 1. Maronchuk II, Sanikovich DD, Mironchuk VI. Solnechnye ele- menty: sovremennoe sostoyanie i perspektivy razvitiya. Energeti- ka [Solar cells: current state and development prospects. Energy] Izvestiya vysshih uchebnyh zavedenij i energeticheskih ob"edinenij SNG. 2019;62(2):105–123. Russian. doi:10.21122/1029-7448-2019-62-2-105-123 2. Prospects for Energy Technologies 2008. Scenarios and Strat- egies until 2050 [Internet]. International Energy Agency. OECD / IEA, 2008. p. 10–15 [cited 29.07.2021]. 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