Method for producing a solar module

Abstract

To provide a method of manufacturing a solar module, a method of connecting a metal interconnector to a solar cell, a metal interconnector for a solar cell, solder flux, a solar module, and a method of manufacturing a metal interconnector, which provide commercially acceptable alternatives to problems associated with the prior art.SOLUTION: A method of manufacturing a solar module includes connecting a metal interconnector to two or more solar cells and applying a transparent cover sheet to the two or more solar cells, wherein connecting the metal interconnector to each solar cell of the two or more solar cells includes providing a solar cell having a bus bar on a surface, providing a metal interconnector having a solder flux on a contact surface, providing solder between the bus bar and the contact surface, and reflowing the solder to connect the metal interconnector to the bus bar, wherein the solder flux includes a reflective additive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a solar module, a method for connecting a metallic interconnector to a solar cell, a metallic interconnector for a solar cell, a solder flux, a solar module, and a method for manufacturing a metallic interconnector. [Background technology]

[0002] In the assembly of photovoltaic (PV) modules, interconnection of crystalline silicon (c-Si) solar cells is typically achieved using automated combined tabbing and stringing equipment that employs soldering. Soldering utilizes a flux, which reacts with and thereby removes the oxide surface layers of both the solder and the substrate. This ensures that clean metal is provided during reflow so that wetting and associated bond formation can proceed. Fluxes are typically liquid and consist of a chemical activator package, additives, a solvent system, and optionally, rosin or synthetic resin. Historically, the solar industry has used alcohol-based flux formulations.

[0003] To interconnect industrial solar cells with the front grid pattern, flat solder-coated copper wires are typically soldered to 2-20 bus bars on the front and back surfaces. These wires are thin and wide to minimize resistive power losses in the wires and minimize stresses within the cells. However, shading of the cells by these wires represents a significant power loss in the encapsulated module, the so-called "shading loss."

[0004] To eliminate this shading loss, researchers have previously explored cell designs in which all contacts are located or routed to the rear of the cell, but such cell designs are undesirably complex and expensive.

[0005] An alternative approach, presented by Sachs et al. at the 24th European PVSEC Conference, Hamburg, Germany, on September 23, 2009, entitled "Light-Capturing Interconnect Wire for 2% Module Power Gain," involves forming triangular grooves on the top surface of the ribbon and coating the surface with a reflective layer, such as silver. The grooves are designed so that incident light is reflected upward toward the module's glass cover sheet at an angle shallow enough to undergo total internal reflection at the glass-air interface and downward onto the solar cells. It is claimed that as much as 80% of the light striking the busbar can potentially be recaptured, and experiments with industrial solar cells show a 2% relative gain in encapsulated cell current and power using this light-capturing interconnect wire compared to a control using standard wire. However, such an approach is expensive and only works well for normally incident radiation. Summary of the Invention

[0006] The present invention seeks to address at least some of the problems associated with the prior art, or at least provide a commercially acceptable alternative thereto.

[0007] The present invention provides a method for manufacturing a solar module, the method comprising: connecting the metallic interconnector to two or more solar cells; applying a transparent cover sheet to the two or more solar cells; Connecting the metallic interconnect to each solar cell of the two or more solar cells providing a solar cell having a bus bar on a surface thereof; providing a metallic interconnect having solder flux on a contact surface; providing solder between the busbar and the contact surface; reflowing the solder to connect the metallic interconnector to the bus bar; The solder flux includes a reflective additive.

[0008] Each aspect or embodiment defined in this specification may be combined with any other aspect or embodiment unless expressly indicated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0009] The inventors have surprisingly found that the resulting solar modules exhibit reduced shading losses compared to conventional solar modules.

[0010] Due to the presence of a reflective coating in the flux, following solder reflow, the metallic interconnect has a reflective coating on its surface. Such a reflective coating can have a reflectivity of at least 10%, more typically at least 20%, even more typically at least 30%, even more typically at least 35%, and even more typically about 40%. During use, such a reflective coating increases light scattering. Without being bound by theory, it is believed that approximately 53% of scattered photons statistically strike the solar cell and induce current after striking the transparent cover sheet / air boundary at an angle greater than the total internal reflection angle (ΦTIR = 42°). This can result in an increase in quantum efficiency of up to 45%. This higher quantum efficiency leads to an increase in short-circuit current density, thus reducing the optically inactive width of the ribbon.

[0011] Advantageously, compared to conventional solar modules, such reduced shading losses can be provided regardless of the angle of incident radiation. Furthermore, compared to conventional methods of manufacturing solar modules, the method of the present invention is simple and low cost.

[0012] As used herein, the term "solar cell" or "photovoltaic cell" may encompass an electrical device that converts light energy directly into electricity through the photovoltaic effect, a physical and chemical phenomenon. As used herein, the term "solar module" or "photovoltaic panel" may encompass multiple solar cells in an integrated group, all oriented in a single plane. Photovoltaic modules often have a glass sheet on the side facing the sun that allows light to pass through while protecting the semiconductor wafer.

[0013] The method includes connecting a metallic interconnect to two or more solar cells. As used herein, the term "metallic interconnector" can encompass a conductive wire or ribbon. "Metallic" means that the interconnector is formed from or includes a metal or alloy. Such a connection is an electrical connection. Two or more solar cells are connected to each other via a metallic interconnector. Typically, the metallic interconnector has a first end and a second end, with one solar cell connected to the first end and another solar cell connected to the second end. Typically, the metallic interconnector connects the top (i.e., light-facing) surface of one solar cell to the bottom (i.e., surface not facing the light) of another solar cell, i.e., the metallic interconnector can connect the positive surface of one solar cell to the negative surface of another solar cell.

[0014] The method includes applying a transparent cover sheet to two or more solar cells. Specifically, the transparent cover sheet is applied to the outer surfaces of the two or more solar cells, more specifically, to the surfaces that receive incident light during use, i.e., the surfaces that face the sun. The transparent cover sheet can physically protect the solar cells while allowing light to pass through to the underlying solar cells.

[0015] Connecting the metallic interconnect to each solar cell of the two or more solar cells includes providing a solar cell with a bus bar on a surface thereof. The term "bus bar" is a term used in the art and, as used herein, can encompass a metal strip or bar.

[0016] Connecting the metallic interconnect to each solar cell of the two or more solar cells includes providing the metallic interconnect with solder flux on its contact surface. The term "solder flux" is a term used in the art and, as used herein, may include a chemical cleaner, fluidizer, or purifier. Solder flux can improve the wetting characteristics of the liquid solder by removing oxidized metals from the surfaces to be soldered, excluding air to prevent further oxidation, and / or facilitating amalgamation. The term "contact surface" as used herein may include the surface that is connected to the solar cells as well as the surface that faces incident light (the "light-receiving" surface) in the final solar cell module. When the metallic interconnect is in the form of a ribbon, the contact surface includes both the top and bottom surfaces of the ribbon. Typically, the contact surface encompasses substantially the entire outer surface of the interconnect.

[0017] Applying solder between the busbar and the contact surface typically involves sandwiching the solder between the busbar and the contact surface. The solder is typically provided so as to contact both the busbar and the contact surface. As used herein, the term "solder" may encompass a fusible metal alloy used to create a permanent bond between metal workpieces. The solder is melted to adhere and connect the components after cooling, but alloys suitable for use as solder must have a lower melting point than the components being joined.

[0018] The solder may be pre-applied to the contact surfaces. In other words, the steps of "providing a metallic interconnect having solder flux on the contact surfaces" and "providing solder between the bus bar and the contact surfaces" may constitute a process of providing a metallic interconnect having solder flux and solder on its contact surfaces, and a process of orienting the solar cell and the metallic interconnect such that the solder is located between the contact surfaces and the bus bar.

[0019] The solder flux includes a reflective additive. As used herein, the term "reflective additive" may include species that can reflect light, particularly sunlight. The reflective additive is typically a solid species suspended in the liquid component of the solder flux.

[0020] The reflective additive preferably comprises a dye and / or a pigment. Such species can provide a high level of reflectivity to the reflective coating, thereby reducing the optically inactive width of the interconnect.

[0021] The reflective additive preferably comprises a pigment. Compared to dyes, pigments exhibit increased color fastness, thereby reducing degradation of the solar module's performance over time. Furthermore, compared to dyes, pigments tend to be less flammable, thereby reducing the risk of fire.

[0022] Compared to dyes, pigments tend to be less soluble in conventional fluxing solutions and may exhibit lower levels of dispersion. As a result, the pigments are preferably coated with one or more of polyols, silanes, amines, and amine salts. Such species can improve compatibility with the coating, increase dispersion, and / or reduce agglomeration during flux storage.

[0023] The reflective additive preferably comprises a pigment comprising one or more of iron oxide, zinc oxide, aluminum oxide, titanium dioxide (e.g., infoliated TiO foam), chromium oxide, perylene, ferric ammonium ferrocyanide, silver (e.g., silver nanoparticles), and aluminum (e.g., aluminum paste). Such species can provide high levels of reflectivity.

[0024] The reflective additive preferably comprises a pigment comprising titanium dioxide, more preferably the titanium dioxide is in the form of flakes, and even more preferably the titanium oxide flakes are coated with alumina and / or zirconia. Such species are particularly suitable for use in the present invention and can provide particularly high levels of reflectivity. Preferably, these species are coated with one or more of polyols, silanes, and amines and amine salts for the reasons discussed above.

[0025] The pigment is preferably in the form of particles (e.g., powder), more preferably flakes. Such a form can provide a high level of reflectance and light scattering. The particles or flakes preferably have a longest dimension of 0.5 to 5 μm, more preferably 1 to 2 μm. Such a size can allow the pigment to be more easily incorporated into the flux.

[0026] The dye preferably comprises a fluorescent dye (also known as a "laser" dye). The presence of the fluorescent dye can increase the quantum efficiency of the solar module. Examples of such dyes include, but are not limited to, rhodamine-based dyes such as rhodamine b, acid-52, fluorescent green, fluorescein, ATTo series dyes, Cy2, tamra, Cal fluor red 590, and perylene dyes.

[0027] The solder flux may further include an optical brightener. As used herein, the term "optical brightener" refers to a compound that absorbs light in the ultraviolet and violet regions of the electromagnetic spectrum (typically 340-370 nm) and re-emits light in the blue region (typically 420-470 nm) by fluorescence. This can cause a "whitening" effect and thus increase reflectance. Suitable optical brighteners include, for example, OB, OB-1, KCB, KSN, FP-127, KB, 4BK, DBH, ER-1, ER-2, ER-3, CXT, VBL, BBU, and CBS-X.

[0028] The reflective additive is preferably white or yellow, more preferably white, as such colors provide a high level of reflectivity.

[0029] The flux contains 0.1 to 15 wt. % of the reflective additive, preferably 0.3 to 2 wt. % of the reflective additive, based on the total weight of the flux. Such an amount can provide a high level of reflectivity without compromising other functions of the solder flux, such as removing oxidized metals from the surfaces to be soldered, locking out air to prevent further oxidation, and / or improving the wetting characteristics of the liquid solder.

[0030] The solder flux preferably further comprises an acrylic resin binder, preferably a methacrylic resin binder. The presence of such an elastomeric binder can provide flexibility to the flux and, therefore, the resulting reflective coating. This results in reduced performance degradation of the solar module, for example, due to power-induced degradation (PID). In addition, chipping or flaking during handling or feeding in automated combined tubing and stringing (CTS) equipment can be reduced. Flexibility can allow solar modules to assume arbitrary shapes, such as being wrapped around automobiles, airplane wings, buildings, robots, and three-dimensional (3-D) displays. Furthermore, the presence of such a binder can make the solder flux substantially "tack-free," even at high operating temperatures. If the flux were tacky, ribbon alignment would be impaired. Sticky flux can cause alignment issues, which in turn can cause peel strength problems. Additionally, sticky or powdery residues can adhere to pulleys, grippers, and other machine parts, causing frequent downtime and aesthetic issues. Sticky flux can also cause cell failure. If the flux is sticky or if the residue remains sticky after processing, the robotic arm cannot properly pick up the string. This can lead to microcracks in the assembled string. Furthermore, the presence of such binders makes the flux particularly compatible with traditional ethyl vinyl acetate (EVA) lamination materials.

[0031] The solder flux preferably contains 1-10 wt. % acrylic resin binder, preferably 2-6 wt. % acrylic resin binder. Below this range, the flux may not provide a sufficient level of flexibility and non-stickiness. Above this range, other functions of the solder flux, such as removing oxidized metals from the surface being soldered, locking out air to prevent further oxidation, and / or improving the wetting characteristics of the liquid solder, may be impaired.

[0032] The acrylic resin binder is preferably an acrylic polymer having a carboxyl group, a hydroxyl group, or an amide group, or a mixture thereof, preferably having a weight-average molecular weight of 5,000 to 500,000 and a glass transition temperature of -20°C to +125°C. Typical useful acrylic polymers include alkyl methacrylates, alkyl acrylates, hydroxyalkyl acrylates, and hydroxyalkyl methacrylates, and may contain styrene, acrylic acid, or methacrylic acid. Amide monomers such as methacrylamide and acrylamide can be used. Glycidyl monomers such as glycidyl acrylate or glycidyl methacrylate can also be used. Isoprene-based liquid rubbers and the like can also be used. Preferred acrylic polymers are alkyl methacrylates having 1 to 18 carbon atoms in the alkyl group, alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, and hydroxyalkyl acrylates or hydroxyalkyl methacrylates having 2 to 4 carbon atoms in each hydroxyalkyl group.

[0033] The solder flux preferably further contains a vinyl resin binder. The presence of such an elastomeric binder can provide flexibility to the flux and, therefore, the resulting reflective coating. As a result, degradation of solar module performance, for example, as a result of bending, is reduced. In addition, chipping or flaking during handling or feeding in automated composite tabbing and stringing (CTS) equipment can be reduced. Flexibility can enable solar modules to assume arbitrary shapes, such as being wrapped around automobiles, airplane wings, buildings, robots, and three-dimensional (3-D) displays. Furthermore, the presence of such a binder can make the solder flux substantially "tack-free," even at high operating temperatures. If the flux is sticky, ribbon alignment will be impaired. Sticky flux can cause alignment issues, which in turn cause peel strength problems. Sticky or powdery residue can also adhere to pulleys, grippers, and other machine parts, resulting in frequent downtime and aesthetic problems. Sticky flux can also cause cell failure. If the flux is sticky or if the residue remains sticky after processing, the robotic arm will not be able to properly pick up the string, which can lead to microcracks in the assembled string. Additionally, the presence of such binders makes the flux particularly compatible with traditional polyolefin (POE) and EVA laminate materials.

[0034] The solder flux preferably contains 0.1 to 5 weight percent vinyl resin binder, preferably 0.5 to 2 weight percent vinyl resin binder. Below this range, the flux may not provide a sufficient level of flexibility and non-stickiness. Above this range, other functions of the solder flux, such as removing oxidized metal from the surface to be soldered, locking out air to prevent further oxidation, and / or improving the wetting characteristics of the liquid solder, may be impaired.

[0035] The solder flux preferably contains both an acrylic resin (preferably a methacrylic resin) binder and a vinyl resin binder.

[0036] The solder flux is preferably substantially halogen-free, more preferably halogen-free. Compared to halogen-containing solder fluxes, this can reduce the aggressiveness of the solder flux to the materials forming the metal interconnects and solar cells. This can improve the reliability of the solar module and enable the solar module to pass the accelerated aging test IEC61215. Furthermore, halogen ions can remain on the cell and migrate, potentially causing a current short circuit.

[0037] The solder flux preferably further comprises an activator, more preferably an activator comprising a dicarboxylic acid, and even more preferably the dicarboxylic acid is selected from one or more of adipic acid, glutaric acid, and succinic acid. Such species may be particularly suitable for removing oxidized metals from surfaces to be soldered, forcing out air to prevent further oxidation, and / or for improving the wetting properties of the liquid solder.

[0038] The solder flux preferably contains 1 to 5% by weight of an activator.

[0039] The solder flux preferably further comprises one or more of a resin, a rosin, a wetting agent, an antifoaming agent, a plasticizer, and a dispersant.

[0040] The solder flux preferably contains an agent for wetting and dispersing the reflective additive (e.g., titanium dioxide). This agent can aid in the wetting and dispersing of pigments and / or dyes in the flux composition. For example, nonionic, cationic, and / or amphoteric wetting and dispersing agents can be used. Exemplary dispersing agents include, but are not limited to, polyethylene glycol and its derivatives (e.g., PEG100, PPG), low molecular weight polyacrylates and methacrylates, block copolymers with pigment-affinity groups such as BYK2023, BYK2117, and BYK180, structured copolymers, Zonyl FSN fluorosurfactants (described as perfluoroalkyl ethoxylates) available from EI DuPont de Nemours & Co., Inc., Fluorad FC-430 (described as a fluoroaliphatic polymer ester) available from 3M Chemical Products Division, and ATSURF fluorosurfactants available from Imperial Chemical Industries. Other exemplary dispersing agents include, but are not limited to, alkoxysilanes (polyalkylene oxide-modified heptamethyltrisiloxane), ethers (allyloxypolyethylene glycol methyl ether, polyoxyethylene cetyl ether), polydimethylsiloxane, polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, hexadimethylsilane, hexadimethyldisilazane, polyoxyethylene sorbitan monooleate, water-soluble ethylene oxide adducts based on ethylene glycol, water-soluble ethylene oxide-propylene oxide adducts based on propylene glycol, polycarboxylic acids (dicarboxylic acids having at least 3 carbon atoms), dimerized carboxylic acids, polymerized carboxylic acids, etc. A particularly suitable agent is BYK 2117.

[0041] Preferably, the busbars include copper, tin, or silver connection pads, and reflowing the solder connects the metallic interconnects to the copper, tin, or silver connection pads. Solder flux may enable particularly favorable wetting of the solder to copper, tin, and silver.

[0042] The metallic interconnect preferably comprises copper or copper alloy ribbon, which can exhibit a desirable level of electrical conductivity and can be soldered using conventional solders.

[0043] The transparent cover sheet preferably comprises glass, which is particularly suited to protecting the solar cells while allowing incident light to pass through the solar cells, and the glass is preferably textured.

[0044] Preferably, the method further comprises laminating the solar cells. Lamination can ensure complete sealing of the delicate, moisture-sensitive interconnected solar cells. Lamination is preferably carried out using a laminating material selected from ethyl vinyl acetate (EVA) and polyolefin (POE). The solder flux of the present invention is compatible with such materials. Lamination preferably involves applying a transparent cover sheet to the side that will be exposed to radiation (the "front sheet") and a polymeric or composite layer to the opposite side (the "back sheet").

[0045] The solder flux may further include a black or blue pigment. The presence of the black or blue pigment can provide a desirable aesthetic effect to the metal interconnect in which the solder flux is used. Thus, the interconnect can exhibit both aesthetic appeal and high reflectivity.

[0046] Suitable black and / or blue pigments include, for example, ferric oxide black, carbon black, graphite, Pigment Black No. 7, iron oxide and chromium(III) oxide pigments (e.g., Sicopal® Black L0095), and Solvent Black 9, 37, 32, 42, 48 and 49, preferably iron oxide and chromium(III) oxide pigments (e.g., Sicopal® Black L0095), Microlith® Black 0066 A and carbon black.

[0047] The solder flux preferably includes an agent for wetting and dispersing the black and / or blue pigment. The agent may be the same as the agent described above for dispersing the reflective additive. Such an agent may be particularly useful when the black and / or blue pigment includes carbon black. When the black and / or blue pigment includes carbon black, a particularly suitable agent is BYK 2117.

[0048] In a further aspect, the present invention provides a method for manufacturing a solar module, the method comprising: providing a first solar cell having a bus bar on a surface thereof; providing a second solar cell having a bus bar on a surface thereof; providing a metallic interconnect having a first end and a second end; providing solder between the bus bar and the first end of the first solar cell; reflowing the solder to connect the first end to the bus bar of the first solar cell; providing solder between the bus bar and the second end of the second solar cell; reflowing the solder to connect the second end to the bus bar of the second solar cell; applying a transparent cover sheet to the solar cell; The first end and the second end are coated with a solder flux, the solder flux including a reflective additive.

[0049] The advantages and preferred features of the first aspect of the invention apply equally to this aspect.

[0050] The two steps of applying solder and / or the two steps of reflowing solder may be performed sequentially or simultaneously.

[0051] In a further aspect, the present invention provides a method of connecting a metallic interconnect to a solar cell, the method comprising: providing a solar cell having a bus bar on a surface thereof; providing a metallic interconnect having solder flux on a contact surface; providing solder between the busbar and the contact surface; and reflowing the solder to connect the metallic interconnect to the bus bar, wherein the solder flux includes a reflective additive.

[0052] The advantages and preferred features of the first aspect of the invention apply equally to this aspect.

[0053] In a further aspect, the present invention provides a metallic interconnect for a solar cell, the metallic interconnect having a solder flux on a surface thereof, the solder flux including a reflective additive and being substantially solvent-free.

[0054] The advantages and preferred features of the first aspect of the invention apply equally to this aspect.

[0055] In automated tabbing and stringing machines, flux is typically applied to ribbons or cells immediately before soldering. Typically, the flux is sprayed onto the cells / ribbons or the ribbons are immersed in a flux tank. The fluxing operation generates a lot of residue and can contaminate machine components. This, in turn, can increase machine downtime, making contamination on the components / cells almost unavoidable. Furthermore, operations such as dip coating can result in uneven flux application, and flux spreading can be observed on the fingers and cell areas. Yellowing and cold solder joints are also common problems associated with standard PV fluxing. Compatibility between conventional EVA (ethylene vinyl acetate) encapsulants and flux residue has also been reported in the literature. Such issues can be avoided by using the metallic interconnect of the present invention. The use of a solvent-free "pre-applied" flux reduces residue formation and associated problems. Furthermore, the cost and safety impact of handling and storing large amounts of flammable (typically alcohol-based) solvents is avoided.

[0056] The metallic interconnect has solder flux on its surface, which may be a contact surface as described above, i.e. the surface that is connected to the solar cell.

[0057] The flux is substantially solvent-free, typically completely solvent-free. The flux may contain less than 2% by weight of solvent, typically less than 1% by weight of solvent, and even more typically less than 0.1% by weight of solvent.

[0058] In a further aspect, the present invention provides a solder flux comprising a solid component and optionally a solvent, wherein the solid component comprises a reflective additive.

[0059] The advantages and preferred features of the first aspect of the invention apply equally to this aspect.

[0060] In a preferred embodiment, the solder flux contains 85 to 95% by weight of solvent.

[0061] The solvent preferably comprises isopropyl alcohol, which is particularly suitable for use in the flux because it evaporates at typical soldering temperatures, thereby leaving little organic residue on the solder joint that can adversely affect the electrical and mechanical performance of the joint.

[0062] In a preferred embodiment, the solder flux comprises, based on the total weight of the solder flux: 85 to 95% by weight of isopropyl alcohol solvent; 0.5 to 10% by weight of a methacrylic resin binder; 0.1 to 5% by weight of a vinyl resin binder; 1 to 5 wt. % of an activator; 0.3 to 2 wt. % of a reflective additive, preferably the reflective additive comprises titanium dioxide, more preferably in powder (e.g., flake) form; Optionally, 0.1 to 2 wt. % of a wetting agent.

[0063] Such solder fluxes exhibit a particularly favorable combination of high reflectivity, flexibility, non-stickiness, non-aggressiveness and excellent wetting properties.

[0064] In a preferred embodiment, the solder flux is substantially solvent-free, thereby avoiding the drawbacks associated with solvents discussed above. Such a "solvent-free" solder flux can be applied, for example, using a "hot melt" process.

[0065] In a further aspect, the present invention provides a solder flux comprising a solid component and optionally a solvent, wherein the solid component comprises a black and / or blue pigment.

[0066] The advantages and preferred features of the first aspect of the invention apply equally to this aspect.

[0067] The presence of a black or blue pigment can provide a desirable aesthetic effect to the metallic interconnect in which the solder flux is used.

[0068] Suitable black and / or blue pigments include, for example, ferric oxide black, carbon black, graphite, Pigment Black No. 7, iron oxide and chromium (III) oxide pigments (e.g., Sicopal® Black L0095), and Solvent Black 9, 37, 32, 42, 48, and 49, preferably carbon black and iron oxide and chromium (III) oxide pigments (e.g., Sicopal® Black L0095). Iron oxide and chromium (III) oxide pigments (e.g., Sicopal® Black L0095) are particularly advantageous because they are black but also reflect light, thereby providing a favorable combination of high reflectance and pleasing aesthetics.

[0069] In a preferred embodiment of this aspect, the solder flux comprises, based on the total weight of the solder flux: 85 to 95% by weight of isopropyl alcohol solvent; 0.5 to 10% by weight of a methacrylic resin binder; 0.1 to 5 weight percent of a vinyl resin binder; 1 to 5 wt. % of an activator; 0.5 to 2 wt. % of a black pigment, the black pigment comprising carbon black and / or iron oxide and chromium (III) oxide pigment; Optionally, 0.1 to 2 wt. % of a wetting agent.

[0070] In another preferred embodiment of this aspect, the solder flux is substantially solvent-free, thereby avoiding the drawbacks associated with solvents discussed above. Such a "solvent-free" solder flux may be applied, for example, using a "hot melt" process.

[0071] In a further aspect, the present invention provides a solar module manufactured according to the methods described herein.

[0072] The advantages and preferred features of the first aspect of the invention apply equally to this aspect.

[0073] In a further aspect, the present invention provides a method of making a metallic interconnect as described herein, the method comprising: Providing a metallic interconnector; providing a solvent-containing solder flux as described herein; applying a solder flux to the metal interconnect; and removing the solvent from the solder flux by evaporation.

[0074] The solder flux may be applied, for example, by one or more of brushing, coating, spraying, spray coating, dipping, and rolling. Evaporation may occur by heating the solder flux, preferably to a temperature above the boiling point of the solvent.

[0075] In a further aspect, the present invention provides a method of making a metallic interconnect as described herein, the method comprising: Providing a metallic interconnector; providing a "solvent-free" solder flux as described herein; melting a solder flux; and applying molten solder flux to the metallic interconnect.

[0076] The molten solder flux may be applied to the metallic interconnect using, for example, a "hot melt" process. [Brief explanation of the drawings]

[0077] The invention will now be described with reference to the following non-limiting drawings. [Figure 1] FIG. 1 is a schematic diagram showing the path of light entering and exiting a conventional solar module. [Figure 2] 1 is a schematic diagram showing the paths of light entering and exiting a solar module according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0078] Referring to Figure 1, a conventional solar module (generally designated 1) is shown. Solar cells 2 have bus bars 3 on their surfaces. To protect the solar cells 2 from air 5, the light-receiving side of the module is covered with a sheet 4 made of glass with an EVA film. Interconnectors (flat metal ribbons) 6 act like mirrors and reflect incoming radiation (indicated by arrows) from the module. The area covered by the ribbons (approximately 3.5%) is primarily lost to photoelectric conversion.

[0079] Referring to Figure 2, a solar module A according to the present invention is shown in which ribbon 6 is coated with a reflective layer 7. After striking a glass-air surface 8 at an angle greater than the angle of total internal reflection, some of the scattered photons strike the solar cell and induce an electric current.

[0080] The invention will now be discussed with reference to the following non-limiting examples. [Example]

[0081] A flexible, non-stick coating and reflective flux was prepared by blending different types of coating and binding resins, plasticizers, and organic acids such as adipic acid and succinic acid. This flux coating imparts color and is inherently reflective when applied to metal ribbon. Inorganic pigments were dispersed in the flux. This flux was manufactured as follows: The resin was precisely measured to the amount of flux required and added to a clean, dry mixing vessel equipped with a heating jacket. The mixture was stirred with the solvent, maintaining the temperature at approximately 60-70°C until the resin dissolved. The mixture was maintained near the above temperature to avoid overheating and evaporation. The required number of organic acids were added to the mixture and dissolved until the mixture was observed to be clear and all solids were dissolved. The required amount of plasticizer was then weighed and added to the mixture, and the mixture was mixed for 10 minutes while maintaining the temperature at 60-70°C. The vessel was covered with a lid during this entire process. The entire mixture was allowed to cool to room temperature. For quality control studies, the required amount of flux was removed from this mixture. The required amount of colorant for this formulation was weighed and added to the flux formulation. When a solvent was used, this mixture was sheared on a high-shear mixer at 7000-8000 rpm for approximately 60-70 minutes until the colorant was completely dispersed. For the hot-melt process, the colorant was added after the solid mixture became fluid. Intermediate breaks were given to maintain the temperature of the mixture during the high-shear mixing process, and the temperature was maintained below 50°C. The resulting mixture was transferred to a container for further use or to coat metal ribbons. Any sedimentation observed must be redispersed before use. The dispersed flux was precoated onto metal ribbons for further applications.

[0082] The flux in this example contains 5% by weight of binder resin, 2% by weight of organic acid, 1% by weight of plasticizer, and 1.5% by weight of inorganic pigment. This flux was coated onto ribbon, and the ribbon was subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of the solar panel by 2.5%. If the pigment is black, it improves the aesthetic appearance of the panel.

[0083] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux-coated ribbon was subjected to reflectance analysis and had a reflectance of 34-36%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0084] As described in Example 1, flexible, reflective fluxes were prepared by combining different types of coating and binder resins, partially dimerized rosin (Poly-Pale), plasticizers, and organic acids such as adipic acid and succinic acid. The fluxes are inherently reflective, and inorganic pigments are dispersed throughout the flux. The flux in this example contains 1 wt. % Ke604 and Polypal rosin, 2 wt. % binder resin (vinyl polymer), 2 wt. % organic acid, 0.5 wt. % plasticizer, and 1 wt. % inorganic pigment. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes resulted in a 2.5% increase in solar panel power output.

[0085] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 27-30%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0086] A flexible, reflective flux was prepared as described in Example 1 by combining different types of binder resins, partially dimerized rosin (Polypal), plasticizers, rosin, and organic acids such as adipic acid and succinic acid. The flux is inherently reflective, with pigment dispersed throughout. This example contains 1% Ke604 and Polypal rosin, 2% by weight of binder resin, 2% by weight of organic acid, and 0.5% by weight of BYK-2023 and 1.1% by weight of pigment. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes resulted in a 2.5% increase in solar panel power output.

[0087] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 30-32%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0088] As described in Example 1, flexible, reflective fluxes were prepared by combining different types of binder resins, plasticizers, and organic acids such as adipic acid and succinic acid. The fluxes are inherently reflective, and inorganic pigments such as zinc oxide are dispersed in the flux. The flux in this example contains 5 wt. % binder resin, 2.2 wt. % organic acid, 0.8 wt. % plasticizer, and 1.2 wt. % inorganic acid. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels by 2.5%.

[0089] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 33-35%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0090] As described in Example 1, a flexible, reflective flux was prepared by combining different types of binder resins, plasticizers, and organic acids such as adipic acid and methylsuccinic acid. The flux is inherently reflective, and an inorganic pigment, titanium dioxide, is dispersed in the flux. The flux in this example contains 5 wt.% binder resin, 1.8 wt.% adipic acid, 0.4 wt.% methylsuccinic acid, 0.8 wt.% plasticizer, and 1.2 wt.% inorganic pigment. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels by 2.5%.

[0091] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 33-36%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0092] As described in Example 1, a flexible, reflective flux was prepared by combining different types of binder resins, plasticizers, and organic acids such as adipic acid and succinic acid. The flux is inherently reflective, with pigments dispersed throughout the flux. The flux in this example contains 5% by weight binder resin, 1.8% by weight adipic acid, and 0.4% by weight succinic acid; 0.8% by weight plasticizer; and 1.2% by weight aluminum paste (100 microns). This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes resulted in a 0.5% increase in solar panel power output.

[0093] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 24-26%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0094] Example 1 was repeated, except that a fluorescent dye (Acid Red-52) was added to the composition. Fluorescent dyes absorb light at shorter wavelengths and emit at longer wavelengths, thus improving the quantum efficiency and reflectivity of the coating; they produce wide-angle scattering and achieve maximum total internal reflection. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis; the high reflectivity of these fluxes increased the power output of the solar panel by 2.5%.

[0095] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 35-38%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized according to IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0096] A reflective hot melt adhesive formulation was prepared as described in Example 1 by combining rosin Ke604, Versamid, organic acids such as adipic acid and palmitic acid, ceresin wax, and pigment. The flux in this example contains 22% by weight Ke604, 9% by weight Versamid, 20% by weight adipic acid, 27% by weight palmitic acid, 15% by weight ceresin wax, and 9% by weight pigment. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis, which showed that the high reflectivity of these fluxes increased the power output of the solar panel by 2.5%.

[0097] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 38-42%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0098] A reflective hot melt adhesive formulation was prepared as described in Example 1 by combining rosin Ke604, Versamid, organic acids such as adipic acid and palmitic acid, ceresin wax, and pigment. The flux in this example contains 25% by weight Ke604, 10% by weight Versamid, 23% by weight adipic acid, 15% by weight palmitic acid, 20% by weight ceresin wax, and 8% by weight pigment. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis, which showed that the high reflectivity of these fluxes increased the power output of the solar panel by 2.5%.

[0099] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 40-50%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized according to IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0100] The reflective hot melt adhesive formulation was prepared as described in Example 1. A flux was prepared by combining polymerized rosin Dymerex, Unirez-2940, an organic acid such as adipic acid or palmitic acid, benzotriazole, and a pigment. The flux in this example contains 18% by weight Dymerex, 26% by weight Unirez-2940, 30% by weight adipic acid, 24% by weight palmitic acid, 1% by weight benzotriazole, and 1% by weight pigment. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels by 2.5%.

[0101] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 40-50%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized according to IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0102] A reflective hot melt adhesive formulation was prepared by combining polymerized rosin Dymerex, Unirez-2940, organic acids such as adipic acid and palmitic acid, benzotriazole, and pigment as described in Example 1. The flux in this example contains 20% by weight Dymerex, 24% by weight Unirez-2940, 25% by weight adipic acid, 27.8% by weight palmitic acid, 0.8% by weight benzotriazole, and 1.4% by weight pigment. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis, showing that the high reflectivity of these fluxes increased the power output of solar panels by 2.5%.

[0103] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 40-50%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized according to IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0104] A flexible, reflective flux was prepared as described in Example 1 by combining different types of binder resins, rosin (Unirez-2940), plasticizers, and organic acids such as adipic acid and suberic acid. The flux was inherently reflective, and laboratory-synthesized porous nanocrystalline TiO leaf-like foam was dispersed in the flux. The flux in this example contained 5 wt% binder resin, 1.2 wt% Unirez-2940, 1.8 wt% adipic acid, 0.5 wt% succinic acid, 0.8 wt% plasticizer, and 1.2 wt% dispersed leaf-like TiO foam. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels by 2.5%.

[0105] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 14-16%. The flux was partially tacky when applied and allowed to dry for 5-6 seconds, and tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0106] As described in Example 1, flexible, reflective fluxes were prepared by combining different types of binder resins, plasticizers, and organic acids such as adipic acid and succinic acid. The fluxes are inherently reflective, and pigments are dispersed throughout the flux. The flux in this example contains 5 wt. % binder resin, 1.8 wt. % adipic acid, and 0.4 wt. % succinic acid; 0.8 wt. % plasticizer; and 2 wt. % pigment (silver nanoparticles). This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels.

[0107] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 30-34%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0108] A flexible, reflective flux was prepared as described in Example 1 by combining different types of binder resins, KE604, partially dimerized rosin (Poly-Pale), plasticizers, and organic acids such as adipic acid. The flux is inherently reflective, and pigment spacers such as Polygloss 90 and aluminum paste 100 are dispersed throughout the flux. The flux in this example contains 1.6 wt.% binder resin, 0.6 wt.% Ke604, 0.4 wt.% Polypale rosin, 2.2 wt.% adipic acid, 0.6 wt.% plasticizer, 1.2 wt.% pigment polygloss 90, and aluminum paste. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels.

[0109] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 14-16%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0110] A flexible, reflective flux was prepared as described in Example 1 by combining different types of binder resins and polymers (polyvinylpyrrolidine K30), plasticizers, and organic acids such as adipic acid and succinic acid. The flux is inherently reflective, and pigments and pigment spacers such as Polygloss 90 and aluminum paste 100 are dispersed throughout the flux. The flux in this example contains 5 wt.% binder resin and polyvinylpyrrolidine K30, 1.8 wt.% adipic acid, 0.2 wt.% succinic acid, 0.8 wt.% plasticizer, 1.2 wt.% pigment Polygloss 90, and aluminum paste. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels by 2.5%.

[0111] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 30-35%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0112] A flexible, reflective, UV-curable flux was prepared by combining moderately activated rosin anhydride adduct, polypropylene glycol diglycidyl ether, Irgacure 184 (or Ciba Darocur® 1173), adipic acid, and succinic acid, as described in Example 1. The flux is inherently reflective, and a pigment, such as Aluminum Paste-100, is dispersed in the flux. In this example, the flux contains 3 wt. % rosin anhydride adduct, 4 wt. % polypropylene glycol diglycidyl ether, 1 wt. % Ciba Darocur® 1173, 1.8 wt. % adipic acid, 0.4 wt. % succinic acid, and 1.2 wt. % inorganic dye, Aluminum Paste-100.

[0113] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 14-16%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0114] A flexible, reflective, UV-curable flux was prepared by combining moderately activated rosin anhydride adduct, polypropylene glycol diglycidyl ether, Irgacure 184 (or Ciba Darocur® 1173), adipic acid, and succinic acid, as described in Example 1. The flux is inherently reflective, and a pigment, such as Aluminum Paste-100, is dispersed in the flux. In this example, the flux contains 6 wt. % rosin anhydride adduct, 5 wt. % polypropylene glycol diglycidyl ether, 2 wt. % Ciba Darocur® 1173, 2 wt. % adipic acid, 0.6 wt. % succinic acid, and 1 wt. % inorganic pigment, Aluminum Paste-100.

[0115] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 13-15%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0116] A flexible, reflective flux was prepared as described in Example 1 by combining different types of binder resins, KE604, partially dimerized rosin (Poly-Pale), plasticizers, and organic acids such as adipic acid. The flux was inherently reflective, and pigment carbon black was dispersed in the flux. The flux in this example contained 1.6 wt.% binder resin, 0.6 wt.% KE604, 0.4 wt.% Polypale rosin, 2.2 wt.% adipic acid, 0.6 wt.% plasticizer, and 1 wt.% pigment carbon black. This flux was coated onto ribbons, resulting in a black coating for aesthetic solar panel applications.

[0117] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 method 2.4.44, dated March 1998. [Example]

[0118] As described in Example 1, flexible, reflective fluxes were prepared by combining different types of binder resins, plasticizers, organic acids such as adipic acid and succinic acid, and dispersants. The fluxes are inherently reflective, and inorganic pigments such as Polygloss 90 and aluminum paste 100 are dispersed in the flux. The flux in this example contains 5 wt.% binder resin, 2.2 wt.% adipic acid and succinic acid, 0.6 wt.% Disperse-BYK-180, and 1.2 wt.% pigments, Polygloss 90 and aluminum paste. This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis. The high reflectivity of these fluxes increased the power output of solar panels by 2.5%.

[0119] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux was subjected to reflectance analysis and had a reflectance of 15-16%. This flux was completely tack-free when applied and allowed to dry immediately. Tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0120] The flux in this example, which is a repeat of Example 1, contains equal amounts of 2.5 wt.% of two binder resins, 2.2 wt.% of organic acids such as adipic acid and succinic acid, 0.8 wt.% of plasticizer, and 1.1 wt.% of pigment. When this flux was coated onto ribbons and the ribbons were subjected to reflectance analysis, the high reflectivity of these fluxes increased the power output of the solar panel by 2.5%.

[0121] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux-coated ribbon was subjected to reflectance analysis and had a reflectance of 34-38%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0122] The flux in this example, which was a repeat of Example 1, contained 4 wt. % binder resin, 2.2 wt. % organic acids such as adipic acid and succinic acid, 1 wt. % plasticizer, and 1.1 wt. % pigment spacers such as polygloss-90 and BLR-698 (TiO submicron particles). This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis, which showed that the high reflectivity of these fluxes increased the power output of the solar panel by 2.5%.

[0123] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux-coated ribbon was subjected to reflectance analysis and had a reflectance of 33-36%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized by IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0124] The flux in this example, which was a repeat of Example 1, contained 3.8 wt.% binder resin, 2.2 wt.% organic acids such as adipic acid and succinic acid, 0.8 wt.% plasticizer, and 0.6% Ke604, 0.4% Polypal rosin, and 1.1 wt.% pigment spacers Polygloss-90 and BLR-698 (TiO submicron particles). This flux was coated onto ribbons, and the ribbons were subjected to reflectance analysis, which showed that the high reflectivity of these fluxes increased the power output of the solar panel by 2.5%.

[0125] The resilience of this flux was tested by twisting a flux-coated ribbon through 360° and bending the ribbon through an angle of 360° and inspecting for cracks and adhesion of the coating on the ribbon. The flux-coated ribbon was subjected to reflectance analysis and found to have a reflectance of 31-35%. The flux was completely tack-free when applied and allowed to dry for 5-6 seconds, and tack was characterized according to IPC-TM-650 Method 2.4.44, dated March 1998. [Example]

[0126] Example 21 was repeated except that carbon black was added in addition to the inorganic white pigment (TiO2). [Example]

[0127] Example 21 was repeated, except that carbon black was added to the composition instead of the inorganic white pigment (TiO) and a pigment spacer such as polygloss-90, which is a non-reflective flux used to improve the aesthetics of solar panels. [Example]

[0128] Example 21 was repeated except that in addition to the inorganic white pigment (TiO2), Solvent Black 27 was added. This gave the ribbon a black coating that was ideal for aesthetic purposes and slightly improved reflectivity.

[0129] A summary of the results of these examples follows.

[0130] [Table 1]

[0131] The foregoing detailed description has been provided by way of illustration and description and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments set forth herein will be apparent to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. 1. A method of manufacturing a solar module, comprising: connecting the metallic interconnector to two or more solar cells; applying a transparent cover sheet to the two or more solar cells; connecting the metallic interconnector to each solar cell of the two or more solar cells providing a solar cell having a bus bar on a surface thereof; providing a metallic interconnect having solder flux on a contact surface; providing solder between the busbar and the contact surface; reflowing the solder to connect the metallic interconnect to the bus bar; The method wherein the solder flux includes a reflective additive.

2. The method of claim 1 , wherein the reflective additive comprises a dye and / or a pigment.

3. 3. The method of claim 1 or 2, wherein the reflective additive comprises a pigment comprising one or more of iron oxide, zinc oxide, aluminum oxide, titanium dioxide, chromium oxide, and ferric ammonium ferrocyanide.

4. 10. The method of any one of the preceding claims, wherein the reflective additive comprises a pigment comprising titanium dioxide, preferably the titanium dioxide is in the form of flakes, more preferably the titanium oxide flakes are coated with alumina and / or zirconia.

5. 10. The method of any one of the preceding claims, wherein the dye comprises a fluorescent dye.

6. 10. The method of any one of the preceding claims, wherein the solder flux further comprises an optical brightener.

7. 10. The method of any one of the preceding claims, wherein the reflective additive is white or yellow.

8. 10. The method according to any one of the preceding claims, wherein the flux comprises 0.1 to 15 wt. % of a reflective additive, preferably 0.3 to 2 wt. % of a reflective additive, based on the total weight of the solder flux.

9. 10. The method according to any one of the preceding claims, wherein the solder flux further comprises an acrylic resin binder, preferably a methacrylic resin binder.

10. 10. The method of claim 9, wherein the solder flux comprises 1 to 10 wt % of an acrylic resin binder, preferably 2 to 6 wt % of an acrylic resin binder, based on the total weight of the solder flux.

11. 10. The method of any one of the preceding claims, wherein the solder flux further comprises a vinyl resin binder.

12. 12. The method of claim 11, wherein the solder flux comprises 0.1 to 5 wt % vinyl resin binder, preferably 0.5 to 2 wt % vinyl resin binder, based on the total weight of the solder flux.

13. 10. The method of any one of the preceding claims, wherein the solder flux comprises an acrylic resin binder and a vinyl resin binder.

14. 10. The method of any one of the preceding claims, wherein the solder flux further comprises an activator, preferably an activator comprising a dicarboxylic acid, preferably the dicarboxylic acid being selected from one or more of adipic acid, glutaric acid and succinic acid.

15. 15. The method of claim 14, wherein the solder flux comprises 1 to 5 weight percent activator, based on the total weight of the solder flux.

16. 10. The method of any one of the preceding claims, wherein the solder flux further comprises one or more of a resin, a rosin, a wetting agent, an antifoaming agent, a plasticizer, and a dispersant.

17. 10. The method of any one of the preceding claims, wherein the bus bars comprise copper, tin or silver connection pads, and wherein reflowing the solder connects the metallic interconnects to the copper, tin or silver connection pads.

18. 10. The method of any one of the preceding claims, wherein the metallic interconnect comprises a copper or copper alloy ribbon.

19. 10. A method according to any one of the preceding claims, wherein the transparent cover sheet comprises glass, preferably textured glass.

20. 1. A method for connecting a metallic interconnect to a solar cell, comprising: providing a solar cell having a bus bar on a surface thereof; providing a metallic interconnect having solder flux on a contact surface; providing solder between the busbar and the contact surface; reflowing the solder to connect the metallic interconnect to the bus bar; The method wherein the solder flux includes a reflective additive.

21. A metallic interconnect for a solar cell, the metallic interconnect having a solder flux on a surface thereof, the solder flux including a reflective additive and being substantially solvent-free.

22. A solder flux comprising a solid component and optionally a solvent, said solid component comprising a reflective additive.

23. 23. The solder flux of claim 22, wherein the solder flux comprises 85 to 95% by weight of a solvent.

24. 24. The solder flux of claim 22 or 23, wherein the solvent comprises isopropyl alcohol.

25. Based on the total weight of the solder flux, 85 to 95% by weight of isopropyl alcohol solvent; 0.5 to 10% by weight of a methacrylic resin binder; 0.1 to 5% by weight of a vinyl resin binder; 1 to 5 wt. % of an activator; 0.3 to 2% by weight of a reflective additive, preferably said reflective additive comprising titanium dioxide, more preferably in powder form; 25. The solder flux of claim 22, optionally comprising 0.1 to 2 wt. % of a wetting agent.

26. 23. The solder flux of claim 22, wherein the solder flux is substantially solvent-free.

27. A solder flux comprising a solid component and optionally a solvent, wherein the solid component comprises a black and / or blue pigment.

28. 28. The solder flux of claim 27, wherein the black and / or blue pigments are selected from iron oxide and chromium(III) oxide pigments and carbon black.

29. Based on the total weight of the solder flux, 85 to 95% by weight of isopropyl alcohol solvent; 0.5 to 10% by weight of a methacrylic resin binder; 0.1 to 5% by weight of a vinyl resin binder; 1 to 5 wt. % of an activator; 0.5 to 2 wt. % of a black pigment selected from iron oxide and chromium (III) oxide pigments and carbon black; 29. The solder flux of claim 27 or 28, optionally comprising 0.1 to 2 wt. % of a wetting agent.

30. 30. The solder flux of claim 27, wherein the solder flux is substantially solvent-free.

31. A solar module manufactured according to the method of any one of claims 1 to 19.

32. 22. A method for manufacturing the metallic interconnect of claim 21, comprising: Providing a metallic interconnector; Supplying a solder flux according to any one of claims 22 to 25; applying the solder flux to the metallic interconnect; and removing the solvent from the solder flux by evaporation.

33. 22. A method for manufacturing the metallic interconnect of claim 21, comprising: Providing a metallic interconnector; providing the solder flux of claim 26; melting the solder flux; applying the molten solder flux to the metallic interconnect.

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