• Journal of the Korean Solar Energy Society
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• v.37 no.2
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• pp.77-85
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• 2017

Thin crystalline silicon (C-Si) solar cell is expected to be a low price energy source by decreasing the consumption of Si. However, thin c-Si solar cell entails the bowing and crack issues in high temperature manufacturing process. Thus, the conventional tabbing process, based on high temperature soldering (> $250^{\circ}C$), has difficulties for applying to thin c-Si solar cell modules. In this paper, a conductive paste (CP) based interconnection process has been proposed to fabricate thin c-Si solar cell modules with high production yield, instead of existing soldering materials. To optimize the process condition for CP based interconnection, we compared the performance and stability of modules fabricated under various lamination temperature (120, 150, and $175^{\circ}C$). The power from CP based module is similar to that with conventional tabbing process, as modules are fabricated. However, the output of CP based module laminated at $120^{\circ}C$ decreases significantly (14.1% for Damp heat and 6.1% for thermal cycle) in harsh condition, while the output drops only in 3% in the samples process at $150^{\circ}C$, $175^{\circ}C$. The peel test indicates that the unstable performance of sample laminated at $120^{\circ}C$ is attributed to weak adhesion strength (1.7 N) between cell and ribbon compared to other cases (2.7 N). As a result, optimized lamination temperature for CP based module process is $150^{\circ}C$, considering stability and energy consumption during the fabrication.

• Journal of the Korean Solar Energy Society
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• v.38 no.1
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• pp.45-55
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• 2018

Environmentally benign lead-free solder coated ribbon (e. g. SnCu, SnZn, SnBi${\cdots}$) has been intensively studied to interconnect cells without lead mixed ribbon (e. g. SnPb) in the crystalline silicon(c-Si) photovoltaic modules. However, high melting point (> $200^{\circ}C$) of non-lead based solder provokes increased thermo-mechanical stress during its soldering process, which causes early degradation of PV module with it. Hence, we proposed low-temperature conductive paste (CP) based tabbing method for lead-free ribbon. Modules, interconnected by the lead-free solder (SnCu) employing CP approach, exhibits similar output without increased resistivity losses at initial condition, in comparison with traditional high temperature soldering method. Moreover, 400 cycles (2,000 hour) of thermal cycle test reveals that the module integrated by CP approach withstands thermo-mechanical stress. Furthermore, this approach guarantees strong mechanical adhesion (peel strength of ~ 2 N) between cell and lead-free ribbons. Therefore, the CP based tabbing process for lead free ribbons enables to interconnect cells in c-Si PV module, without deteriorating its performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.18-21
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• 2002

As the mask design rules get smaller, the probability of the process failure becomes higher due to the narrow overlay margin between the contact and metal interconnect layers. To obtain the minimum process margin, a tabbing and cutting method is applied with the rule based optical proximity correction to the metal layer, so that the protection to bridge problems caused by the insufficient space margin between the metal layers can be accomplished. The side-lobe phenomenon from the attenuated phase shift mask with the tight design nile is analyzed through the aerial image simulation for test patterns with variation of the process parameters such as numerical aperture, transmission rate, and partial coherence. The corrected patterns are finally generated by the rules extracted from the side-lobe simulation.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.209-212
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• 2002

As the mask design rules get smaller, the probability of the process failure becomes higher doc to the narrow overlay margin between the contact and metal interconnect layers. To obtain the minimum process margin, a tabbing and cutting method Is applied with the rule based optical\ulcorner proximity correction to the metal layer, so that the protection to bridge problems caused by the insufficient space margin between the metal layers can be accomplished. The side-lobe phenomenon from the attenuated phase shift mask with the tight design rule is analyzed through the aerial image simulation for test patterns with variation of the process parameters such as numerical aperture, transmission rate, and partial coherence. The corrected patterns are finally generated by the rules extracted from the side-lobe simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.72-72
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• 2010

The PV module company use variable process step and type. Especially soldering process is important, because crystalline cell can be bow by beating temperature. Most PV module company use hot air soldering type in the tabbing & string process. Although hot air type is used widely but this type is bound to influence on cell damage. So recently new way is introducing like a high current way. In this paper, we compare with characteristics of each soldering type and then conform a method to minimize solar cell deformation. Actually solar cell deformation show many difference by fix position and cooling time after soldering step.

• Current Photovoltaic Research
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• v.4 no.2
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• pp.59-63
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• 2016

A key point of a soldering process for photovoltaic (PV) modules is to increase an adhesive strength leading a low resistivity between ribbon and cell. In this study, we intended to optimize a heating condition for the soldering process and characterize the soldered joint via physical and chemical analysis methods. For the purpose, the heating conditions were adjusted by IR lamp power, heating time and hot plate temperature for preheating a cell. Since then the peel test for the ribbon and cell was conducted, consequently the peel strength data shows that there is some optimum soldering condition. In here, we observed that the peel strength was modified by increasing the heating condition. Such a soldering property is affected by a various factors of which the soldered joint, flux and bus bar of the cell are changed on the heating condition. Therefore, we tried to reveal causes determining the soldering property through analyzing the soldered interface.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.387-389
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• 2009

PV module is manufactured by several steps such as cell sort, tabbing & string, lay-up, lamination processes. In oder to manufacture PV module, solar cell must be placed in high temperature. Soldering Process in high temperature is important because it directly influences electric output performance changes of solar cell in solar cell module. We consider applying momentary high temperature, while soldering solar cell, and expect change electric characteristics of PV module. In this paper, we measure electric output characteristics of solar cells after those are applied with high temperature changes for two seconds. From these results, we confirm with application of high temperature, $I_{sc}$ increase and $V_{oc}$ slightly decreases.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.246-250
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• 2009

String & tabbing step in the crystalline PV module manufacturing process for the temperature directly affects solar cells. In fact, in the manufacture of PV modules tend to be temperature factor and the corresponding changes n the output shows the same characteristics. In this journal, it will be considered about thermal characteristics, especially changes of characteristic in high temperature of the solar cell through experiment that we measure electric output characteristics of solar cells after those are applied with high temperature changes for two seconds. And we can think about the possibility of efficiency improvements over looks in PV module manufacturing processes.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.58.1-58.1
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• 2010

In solar cell module manufacturing, single solar cells has to be joined electrically to strings. Copper stripes coated with tin-silver-copper alloy are joined on screen printed silver of solar cells which is called busbar. The bus bar collects the electrons generated in solar cell and it is connected to the next cell in the conventional module manufacturing by a metal stringer using conventional hot air or infrared lamp soldering systems. For thin solar cells, both soldering methods have disadvantages, which heats up the whole cell to high temperatures. Because of the different thermal expansion coefficient, mechanical stresses are induced in the solar cell. Recently, the trend of solar cell is toward thinner thickness below 180um and thus the risk of breakage of solar cells is increasing. This has led to the demand for new joining processes with high productivity and reduced error rates. In our project, we have developed a new method to solder solar cells with a laser heating source. The soldering process using diode laser with wavelength of 980nm was examined. The diode laser used has a maximum power of 60W and a scanner system is used to solder dimension of 6" solar cell and the beam travel speed is optimized. For clamping copper stripe to solar cell, zirconia(ZrO)coated iron pin-spring system is used to clamp both joining parts during a scanner system is traveled. The hot plate temperature that solar cell is positioned during lasersoldering process is optimized. Also, conventional solder joints after $180^{\circ}C$ peel tests are compared to the laser soldering methods. Microstructures in welded zone shows that the diffusion zone between solar cell and metal stripes is better formed than inIR soldering method. It is analyzed that the laser solder joints show no damages to the silicon wafer and no cracks beneath the contact. Peel strength between 4N and 5N are measured, with much shorter joining time than IR solder joints and it is shown that the use of laser soldering reduced the degree of bending of solar cell much less than IR soldering.