Low-temperature solder, manufacturing method of low-temperature solder, and low-temperature solder coated lead wire

Abstract

PURPOSE: To provide a low temperature solder that is obtained by being molten and alloyed by mixing Al.P (or CuP) with an alloy of Sn and Bi and can be soldered to an electrode (aluminum, copper or the like) on a resin film, and is inexpensive, a method for manufacturing such low temperature solder, and a low temperature solder-coated lead wire.CONSTITUTION: A low temperature solder contains a base material which is an alloy of Sn and Bi, and 0.01 wt.% or more and 1.5 wt.% or less of a main material which is composed of Al that is a material giving adhesin to an object to be soldered, and P or CuP that is a material for removing oxide from and giving adhesion to the object to be soldered, and has enhanced adhesive force, and contains Al and P, optionally Cu, and the balance Sn and Bi.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a low-temperature solder used in resin films used in solar cell substrates, liquid crystal substrates, etc., a method for manufacturing the low-temperature solder, and a low-temperature solder-coated lead wire. [Background technology]

[0002] Conventionally, tin-lead solder has been widely used to solder lead wires to electrodes of solar cell substrates, liquid crystal substrates, etc., due to its high strength and low cost.

[0003] Furthermore, in the case of electrodes made of aluminum or the like, sufficient soldering strength cannot be obtained, so silver paste is applied and sintered, and then lead wires are soldered onto this with tin-lead solder.

[0004] Recently, there has been a growing demand for lead-free soldering due to concerns about pollution.

[0005] Furthermore, there is a demand for forming a solar cell on a flexible resin film such as PET, and low-temperature soldering of lead wires to the electrodes (aluminum electrodes, copper electrodes, etc.). DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0006] Conventional lead-free solders have had problems compared to tin-lead solders, such as being slightly less strong than required and being expensive, preventing them from becoming an alternative.

[0007] Furthermore, in solar cells and the like formed on a resin film, the soldering temperature is too high. [Means for solving the problem]

[0008] The inventors have discovered that low-temperature solders made of Sn, a type of lead-free solder, and Bi, In, or an alloy of Bi and In, when melted and alloyed with trace amounts of one or more of Al, P, Sb, and In (except when the base material contains In) in a total amount of up to 3 wt%, preferably 1 wt% to 1.5 wt%, can be very firmly soldered to electrodes (aluminum, copper, etc.) made of resin films, etc.

[0009] Therefore, in a low-temperature solder made of Sn and Bi, In, or an alloy of Bi and In, the present inventors mix a main material made of one or more of Al, P, Sb, and In (except when the base material contains In) into a base material which is an alloy of Sn, Bi, In, or Bi and In, in a total amount of up to 3 wt% or less, preferably 1.0 to 1.5 wt% or less, and 0.01 wt% or more, and melt and alloy it to increase the adhesion strength.

[0010] In this case, the melting temperature of the low-temperature solder after melting and alloying is set to be the same as or lower than the melting temperature of the base material.

[0011] In addition, a secondary material made of an alloy containing one or more of Al, P, Sb, and In is mixed into the base material as needed, and melted and alloyed.

[0012] In addition, the alloy of the secondary material is an alloy of Cu and P.

[0013] Furthermore, the base material is mixed with Al, CuP, and if necessary In as main elements, in a total amount of up to 3 wt%, preferably 1.0 to 1.5 wt%, and more preferably 0.1 wt% or more, and melted and alloyed.

[0014] In addition, the base material, main material, and secondary material are mixed together or in multiple parts and melted and alloyed.

[0015] It is also used to solder lead wires to the electrodes of solar cell substrates and liquid crystal substrates (resin films).

[0016] The low-temperature solder is melted and applied to the surface of the wire or ribbon.

[0017] The melt coating is carried out while applying ultrasonic waves. [Effects of the Invention]

[0018] As described above, the present invention relates to low-temperature solders made of Sn and Bi, In, or alloys of Bi and In. When a small amount of one or more of Al, P, Sb, or In (except when the base material contains In) is mixed in at a maximum total of 3 wt%, preferably 1 wt% to 1.5 wt%, and melted and alloyed, the low-temperature solder can be soldered very firmly to electrodes (aluminum, copper, etc.) such as resin films, and in particular, low-temperature solders made of Sn and Bi can be produced very cheaply.

[0019] Furthermore, the melting temperature of the low-temperature solder after melting and alloying was the same as or lower than that of the base material, eliminating the rise in melting temperature due to contamination.

[0020] In addition, by mixing one or more of Al, P, Sb, In (except when the base material contains In), melting and alloying them to produce low-temperature solder, it was possible to significantly increase the adhesive strength to the soldered object. Example 1

[0021] FIG. 1 is an explanatory diagram of the low-temperature solder manufacturing method of the present invention.

[0022] FIG. 1(a) shows a flow chart, and FIG. 1(b) shows an example of materials.

[0023] In (a) of Fig. 1, S1 prepares the base material and main material. For this, the following materials are prepared as shown in the material examples in (b) of Fig. 1.

[0024] ·Base material: Sn42 Bi58 ·Main material: Al, GuP, In Here, the base material is the basic material (base material) of the alloy that forms the low-temperature solder of the present invention, and for example, 42 wt% Sn and 58 wt% Bi (melting temperature 139°C) were used. The weight ratio of Sn to Bi can be any within the range that allows for the creation of an alloy, for example, 3 to 58 wt% Bi, with the remainder being Sn. The ratio can be selected appropriately to achieve the desired value by experimenting with factors such as the melting temperature (the more Bi, the lower the temperature; at 58 wt%, the melting temperature is 139°C). Note that for other low-temperature solders, such as Sn-In and Sn-Bi-In, the ratio can be selected appropriately as shown in Figure 5 and its explanation.

[0025] The main material is a material that affects soldering, such as oxide film removal, adhesion, wettability, fluidity, and viscosity, on the surface of the soldered object. In this invention, the main material is a material whose total amount is a maximum of 3 wt%, preferably 1 to 1.5 wt%, and more than 0.01 wt%. Here, it is a material to be mixed with one or more of Al (oxide film removal and adhesion on the soldered object), P (or CuP, oxide film removal and adhesion on the soldered object), In (wettability and fluidity), and Sb (adhesion) to be melted and alloyed. The main material, combined with a total amount of a trace amount of a maximum of 3 wt%, preferably 1 to 1.5 wt%, and more than 0.01 wt%, ensures that the melting temperature of the low-temperature solder after mixing and melting the main material into the base material is equal to or slightly lower (e.g., 1 to 3°C lower) than the melting temperature of the base material. This is presumably because the total amount of the main material is a very small amount of up to 3 wt% or less, preferably 1 to 1.5 wt% or less, relative to the base material, and so the main material enters the skeleton of the base material and reconstitutes the skeleton.

[0026] In S2, the main material is mixed with the base material prepared in S1.

[0027] In S3, the base material and main material are melted and alloyed. This is done by mixing the base material with the main material in S2, heating and melting them, and stirring thoroughly to form an alloy. If the main material is oxidized by oxygen in the air and alloying becomes difficult, an inert gas (such as nitrogen gas) can be blown into the crucible as needed, or a melting furnace or vacuum melting furnace filled with an inert gas can be used.

[0028] S4: The low-temperature solder material is completed.

[0029] As described above, by preparing the base material and main material, mixing them, and melting and alloying them, it is possible to manufacture the low-temperature solders (Sn-Bi, Sn-In, and Sn-Bi-In low-temperature solders) according to the present invention. This will be explained in detail below.

[0030] FIG. 2 is an explanatory diagram of the low-temperature solder material manufacturing apparatus of the present invention.

[0031] In FIG. 2, the solder material 1 is the base material or main material prepared in S1 of FIG. 1, which is metal fragments (coarsely crushed) in this case.

[0032] The solder material input tray 2 is used to place the solder material 1 on and input it into the melting furnace 3 .

[0033] The melting furnace 3 is heated by a heater 4 or the like, and the solder material 1 is placed inside, where it melts the base material and main material, stirring them to form an alloy. The melting furnace 3 is usually operated in the atmosphere, where it melts the base material and main material placed inside, stirring them to form an alloy. During this process, an inert gas (such as nitrogen gas) is blown in as needed to reduce oxidation caused by oxygen in the air, and the furnace is further sealed and filled with an inert gas (or evacuated) as needed.

[0034] As described above, the base material and main material prepared in S1 of FIG. 1 are mixed, melted in the melting furnace 3, and stirred to form an alloy, thereby making it possible to manufacture the low-temperature solder of the present invention (Sn-Bi, Sn-In, or Sn-Bi-In low-temperature solder).

[0035] FIG. 3 is an explanatory diagram of low-temperature soldering of lead wires according to the present invention.

[0036] FIG. 3(a) shows a flow chart, and FIG. 3(b) shows an example of a substrate / lead.

[0037] In (a) of Figure 3, S11 is ultrasonic pre-soldering of a substrate pattern with low-temperature solder. For example, the low-temperature solder of the present invention (the low-temperature solder produced in S4 of Figure 1) is supplied to the tip of an ultrasonic soldering iron and melted on the portion (pattern) to be soldered on a solar cell substrate (e.g., a 0.1 mm thick PET board), and ultrasonic waves are applied to pre-solder the pattern on the substrate (this is called ultrasonic pre-soldering).

[0038] In step S12, the lead wire is soldered with or without ultrasonic waves. The lead wire is placed along the pattern that was ultrasonically pre-soldered on the electrode (e.g., aluminum foil) of a solar cell substrate (PET plate) in step S11, and the low-temperature solder of the present invention is melted and soldered to the lead wire with or without applying ultrasonic waves. Note that if the low-temperature solder has already been pre-soldered on the lead wire, there is no need to supply solder.

[0039] As described above, ultrasonic pre-soldering is performed with the low-temperature solder of the present invention on the part to be soldered (for example, the electrode part (aluminum part) of the substrate (PET plate) of a solar cell) (S11), and then the low-temperature solder of the present invention is used to ultrasonically solder or non-ultrasonically solder the lead wire onto the pre-soldered part (pattern) (S12).This makes it possible to ultrasonically pre-solder the electrode part (aluminum foil part) of a solar cell substrate, which cannot be soldered using conventional methods, and then ultrasonically solder or non-ultrasonically solder the lead wire onto that.

[0040] Furthermore, ultrasonic soldering is performed at a power of 10 W or less, usually around 1 to 3 W. If the power is too strong, it can damage the film (such as the nitride film) formed on the solar cell substrate and the crystals on the surface of the substrate, so it is not made too strong.

[0041] FIG. 3(b) shows an example of a substrate / lead wire.

[0042] In Figure 3(b), the substrate is a heat-resistant resin substrate such as PET (e.g., a flexible resin substrate about 0.1 mm thick), an example of a substrate that is extremely difficult to solder using conventional soldering. The portions (patterns) of these substrates that will become electrodes (aluminum electrodes, copper electrodes, etc.) are ultrasonically pre-soldered with the adhesive low-temperature solder of the present invention. Then, by ultrasonically soldering or non-ultrasonically soldering a lead wire to this pre-soldered portion (pattern), it becomes possible to solder the lead wire to the substrate (aluminum electrode, copper electrode).

[0043] The lead wire is soldered to the electrode portion (pattern) on the substrate using the adhesive low-temperature solder of the present invention, and may be a wire (a circular copper wire solder-plated (ultrasonic solder plating) with the low-temperature solder of the present invention; it is easier to solder if it is crushed into a slightly oval shape), a ribbon (a ribbon made by cutting a thin copper plate to a width of about 1 mm and then solder-plating (ultrasonic solder plating) with the low-temperature solder of the present invention in advance), etc.

[0044] FIG. 4 shows an explanatory diagram of low temperature soldering according to the present invention.

[0045] FIG. 4(a) shows an example of pre-soldering, and FIG. 4(b) shows an example of ribbon or wire soldering.

[0046] In FIG. 4(a), a substrate (for example, a PET plate with a thickness of 0.1 mm) 11 is an example of a substrate for a solar cell, and an aluminum film (foil) 12 is formed on the entire back surface of the substrate 11, for example.

[0047] The aluminum film (foil) 12 is an electrode (aluminum electrode) formed by forming (adhering, vapor deposition, etc.) an aluminum foil (film) on the entire back surface of the illustrated substrate (PET plate) 11, which is the substrate of the solar cell.

[0048] The ultrasonic soldering iron tip 13 is a soldering iron tip that is heated while ultrasonic waves are applied from an ultrasonic generator (not shown).

[0049] The low-temperature solder 14 is the low-temperature solder of the present invention (the low-temperature solder manufactured in S4 of FIG. 1).

[0050] Next, the soldering operation will be described.

[0051] (1) The substrate 11 is transported onto a preheating table, fixed by vacuum suction, and preheated (for example, to about 130° C.).

[0052] (2) From the start point to the end point of the electrode pattern (strip-shaped pattern) to be formed on the aluminum film (foil) 12, low-temperature solder 14 is automatically supplied to the tip 13 of the ultrasonic soldering iron shown in the figure, and while melting it, ultrasonic waves are applied and the iron is moved at a constant speed while being close enough to the aluminum film (foil) 12 so as not to rub against it, thereby forming a strip-shaped preliminary solder pattern on the aluminum film (foil) 12.

[0053] As a result of the above, it becomes possible to low-temperature solder the low-temperature solder 14 of the present invention onto the aluminum film (foil) 12 in a predetermined pattern.

[0054] FIG. 4(b) shows an example of low temperature soldering of ribbons or wires.

[0055] In FIG. 4(b), the ultrasonic soldering iron tip 13-1 is a soldering iron tip that is heated with or without applying ultrasonic waves from an ultrasonic generator (not shown).

[0056] The low-temperature soldered ribbon or wire 15 is a ribbon or wire that has been pre-soldered with the low-temperature solder of the present invention. The wire 15 has better solderability if it is slightly deformed into an oval shape.

[0057] Next, the soldering operation of the ribbon or wire to the preliminary solder pattern portion will be described.

[0058] (1) As in FIG. 4(a), the substrate 11 is preheated.

[0059] (2) The low-temperature soldered ribbon or wire 14 is placed along the preliminary solder pattern portion formed on the aluminum film (foil) 12 on the top (back) side of the substrate 11, and the low-temperature soldered ribbon or wire 15 is lightly pressed from above with the tip 13-1 of a soldering iron with or without ultrasonic waves and moved at a constant speed to the right as shown in the figure, melting the solder of the low-temperature soldered ribbon or wire 15 and soldering it to the preliminary solder pattern portion.

[0060] As a result of the above, it becomes possible to solder the ribbon or wire 15, which has been pre-soldered with the low-temperature solder 14 of the present invention, to the pre-solder pattern portion on the aluminum film (foil) 12.

[0061] The quality of the ultrasonic soldering or non-ultrasonic soldering of the present invention is determined by soldering a ribbon or wire to the part to be soldered with or without ultrasonic waves, and then pulling the ribbon or wire with a force slightly weaker than the force that would break the substrate (bending force, approximately 2 to 5 kg). If the ribbon or wire does not peel off from the substrate, it is judged as good, and if it does peel off, it is judged as bad.

[0062] FIG. 5 shows an example of the composition of the low-temperature solder of the present invention.

[0063] In FIG. 5, the base material and main material are the same as those described in FIG.

[0064] The composition examples are examples of the composition of the base material and main material.

[0065] The wt% examples are examples of the wt% of the composition of the base material and main material.

[0066] The wt% ranges are examples of the wt% ranges of the base material and main material compositions.

[0067] The composition, wt% example, and wt% range are shown in Figure 5 below.

[0068] Base material Main material Notes (melting point example) Composition example: Sn-Bi alloy Al P Sb In Melting point: e.g. 139°C (In is excluded when it is contained in the base material) Sn-In alloy Melting point: e.g. 120°C SnBi-In alloy Melting point: e.g. 90°C wt% example Sn Bi In Al CuP8 Sb In 42 58 -- 0.5 0.5 0.5 0.5 52 -- 48 0.5 0.5 0.5 0.5 AA / 2 A 0.5 0.5 0.5 0.5 wt% range 0.1 Trace amount 0.1 0.1 | |(P) | | 1.0 0.1 1.0 1.0 Total amount: Maximum 3wt%, preferably 1.0-1.5wt% or less As an example of composition, the prototype used a base material with 42 wt% Sn and 58 wt% Bi as shown in the figure. The composition range can be any as long as it is stable and within the range in which low-temperature solder alloys (Sn-Bi, Sn-In, and Sn-Bi-In solder alloys) can be made. For example, a Sn-Bi solder alloy can be made with 3 wt% to 58 wt% Bi, with the remainder being Sn. The melting temperature of the low-temperature solder alloy (base material) can be measured and the appropriate composition can be selected through experiments.

[0069] The main materials used include Al, P (or CuP8), In, Bi, and Sb. For the P prototype, we used P (red phosphorus) and CuP8 alloy (an alloy containing 8 wt% P and the remainder being Cu, resulting in a copper phosphide with a P wt% of 8% of CuP8). In the case of P, saturation occurs at approximately 0.1 wt% (or approximately 0.16 wt% in the case of CuP8), and adding more significantly increases viscosity. For this reason, for normal use to ensure fluidity and wettability, it is desirable to add P below saturation (the amount of P added should be about one-tenth of that of other materials, preferably between 0.1 wt% and 0.01 wt%). Similar trends are observed for other main materials, so the optimal amount can be determined through experimentation as needed.

[0070] The total amount of the main material should be a maximum of 3 wt% or less, preferably 1 to 1.5 wt% or less, and desirably 0.1 wt% or more. When the main material is added within this range, the melting temperature is approximately the same as or slightly lower than the base material.

[0071] Figure 6 shows a prototype example of the low-temperature solder of the present invention. The illustration shows examples of the many prototypes that can be used for the soldering of Figure 4 described above. Unusable ones are omitted.

[0072] In FIG. 6, the base material of the low-temperature solder of the present invention (the low-temperature solder produced in S4 of FIG. 1) is Sn52 / In48 (melting point: 120°C) Sn42 / Bi58 (melting point: 139°C) Sn48 / Bi52 (melting point: ) Sn40 / In40 / Bi20 (melting point: 90°C) Four types were used:

[0073] The main materials used were Al, CuP8, and In (each 0.5 wt%). CuP8 is copper phosphide with 8 wt% P and the remainder Cu.

[0074] The sample number is the number of the sample produced.

[0075] The above prototype samples were subjected to ultrasonic soldering and non-ultrasonic soldering as shown in Figure 5, and only the good ones are listed. Those that could not be soldered are omitted. The results are shown in Figure 7.

[0076] FIG. 7 shows an example of soldering using the low-temperature solder of the present invention. Ultrasonic is a distinction between soldering with ultrasonic waves and soldering without ultrasonic waves.

[0077] The soldering object is the material to be soldered using the low-temperature solder sample of Figure 7 of the present invention, and is classified into Al plate (0.1 mm thick), Cu plate (0.1 mm thick), Cu wire (0.3 to 0.4 mm diameter) / ribbon (100 μm thick, 50 μm thick, 30 μm thick), and Si wafer (0.2 mm thick).

[0078] ·◎ indicates that the low-temperature solder of the present invention has excellent adhesion to the object to be soldered (the force is slightly weaker than the force at which a Si wafer breaks when a 0.4 mm φ tin-plated wire is soldered and pulled (tensile strength of approximately 1 to 5 kg)).

[0079] ·△ indicates that the low temperature solder of the present invention has poor adhesion to the soldering object (when a 0.4 mmφ tin-plated wire is soldered and pulled, it peels off with a slight force).

[0080] From the above experiment shown in Figure 7, it was found that when ultrasonic waves were used, sufficient soldering strength was obtained for Al plate, Cu plate, Cu wire / ribbon, and Si wafer.

[0081] In addition, when there was no ultrasonic wave, the solder came off when pulled. Cleaning the surface of the soldering object sometimes resulted in a fairly strong adhesive force, but in other cases it was unstable.

[0082] FIG. 8 shows an example of soldering (metal-metal) using the low-temperature solder of the present invention. FIG. 8(a) shows an example of soldering. Here, the soldering conditions are as shown in the figure: Solder melting point: approx. 138°C Maximum process temperature: 180°C or less

[0083] The low-temperature solder used was 42 wt% Sn, 58 wt% Bi, and 0.5 wt% each of Al, CuP, and In (the following explanations of Figures 8 to 13 will use an example using this low-temperature solder). The same applies to other Sn-In alloy and Sn-Bi alloy low-temperature solders.

[0084] 8(a), a sheet of PET base film with aluminum foil bonded to it using a Co-PET adhesive is cut to the dimensions shown. Then, as shown, the aluminum foil is partially overlapped on top and bottom, and the low-temperature solder (Sn-Bi low-temperature solder) of the present invention is soldered to the overlapping portions.

[0085] The soldering method is, for example, to pre-solder the upper and lower aluminum foil parts with low-temperature solder. Note that soldering with the application of ultrasonic waves (ultrasonic soldering) can ensure reliable soldering. Then, overlap the pre-soldered portion on the upper aluminum foil with the pre-soldered portion on the lower aluminum foil as shown in the figure, press the whole thing down with the tip of the soldering iron, and melt the low-temperature solder to solder it.Using ultrasonic soldering in this case will ensure reliable soldering.

[0086] In this way, the aluminum foil adhered to the PET film surface was successfully soldered together at low temperature, as shown in Figure 8(a). Soldering without ultrasonic waves is also possible, but ultrasonic soldering is preferable for reliability.

[0087] Figure 8(b) shows a photographic example of soldering. These photographs show an example of placing a long, thin piece of aluminum foil horizontally on the surface of PET, and then using ultrasonic low-temperature soldering only on the central "soldered portion" shown in the figure. The aluminum foil was strongly soldered to the PET surface at the "soldered portion" shown in the figure.

[0088] Next, the example of laminating the PET film shown in FIG. 8 will be described in detail with reference to FIG. FIG. 9 shows an example of laminating a PET film according to the present invention. FIG. 9(a) shows a flowchart, and FIG. 9(b) shows an explanatory diagram thereof.

[0089] In (a) of Figure 9, S21 fixes a film to a sponge. As shown in (b-1) on the right, this involves fixing a film (e.g., a PET film) to a heat-resistant sponge (e.g., with a heat-resistant polyimide tape coated with an adhesive).

[0090] In S22, a large amount of solder is applied to the tip of the iron. This is shown in (b-2) on the right side, where a large amount of the low-temperature solder of the present invention is applied to the tip of the iron. S23 is soldered using ultrasonic waves so that the tip of the soldering iron does not come into contact with the film.

[0091] In S24, one of the films is turned over and the solder side of the other is placed on top of it, as shown in (b-3) on the right, so that the pre-soldered film sides are overlapping.

[0092] S25 cuts the copper plate to the size of the soldering area. The S26 presses the copper plate with the tip of the iron like an iron. S27 is completed when the melted solder has overflowed from the edges. As shown in (b-4) on the right, S26 and S27 are performed by pressing the tip of the soldering iron (with ultrasonic waves) onto a copper plate with good thermal conductivity, so that the low-temperature solder on the pre-soldered joint surface melts and overflows from the edges. This allows for beautiful ultrasonic low-temperature soldering, just like ironing, without the film melting or softening and shrinking if the tip of the iron is placed directly on the film.

[0093] Figure 9(c) shows an example of soldering conditions, which are the same as those shown in Figure 9(a) and (b) above. Here, the following conditions were set: Iron tip temperature: 175°C ± 5°C Sliding angle setting: 14 - Flooring: Poron sponge Ultrasonic output: 10W

[0094] Figure 9(d) shows a cross-sectional view of soldering. This is a schematic cross-sectional view of a case where, instead of the copper plate in Figure 9(a), aluminum foil (Al) (pre-soldered ultrasonically) is bonded to the PET surface via polyimide tape, and the two are ultrasonically low-temperature soldered together. In this case, if adhesive-coated polyimide tape is attached so that it surrounds only the areas to be soldered, it is possible to prevent low-temperature soldering from occurring in unnecessary areas.

[0095] Figure 10 shows an example of an experiment using low-temperature soldering of the present invention. This shows examples of soldering with and without ultrasonic waves under the conditions of Figures 8 and 9. With the low-temperature soldering of the present invention, the following results were obtained, for example.

[0096] No. Material Notes (Katsuragi, hardness, surface condition, etc.) 3. SUS plate: Low temperature soldering is possible if preheated. (Ultrasonic soldering, same below) 4 Cutting boards Low temperature soldering possible without preheating ·5 MDF Same as above 6 Corkboards (same as above) 7. Acrylic plate (same as above) 9. EPDM sponge rubber (same as above) 10 NR sponge rubber Same as above 11 Boron sponge (same as above) 12 NR rubber sheet: If preheated, low temperature soldering is possible

[0097] It has been found that the above-mentioned cellulose / resin materials can also be soldered using the low-temperature solder of the present invention (if necessary, ultrasonic soldering or preheating (to a temperature about 10 degrees lower than the melting temperature) can be used before soldering).

[0098] FIG. 10(b) shows a photographic example of the litter material in FIG. 10(a). 11 shows an example of the results of a bonding test using the low-temperature solder of the present invention. The experimental results are as follows: *1: Bondability: When a 0.2 mm diameter wire was bonded, an adhesion force of 300 g or more was judged as ok. *2: Those without the US marking can be adhered without ultrasound. *3:29 PET is the No. 1 candidate for propskite.

[0099] The metals shown in Figure 11 (1 silver, 2 copper, 3 aluminum, etc.) could be soldered at low temperatures with and without ultrasonic waves. Furthermore, inorganic materials (7 alumina, 8 barium titanate, 10 silicon carbide, 11 silicon nitride, 12 fluorite, 13 quartz, 14 ceramic (pottery), etc.) formed by firing the oxides shown in Figure 11 could be soldered at low temperatures with or without ultrasonic waves.

[0100] Furthermore, the cellulose / resins shown in Figure 11 (16 polyethylene, 17 polypropylene, ..., 29 PET, etc.) could be soldered at low temperatures with ultrasonic waves. In addition, the cutting board 4 and cork board 6 shown in Figure 10 could be soldered with ultrasonic waves.

[0101] FIG. 12 shows an example of an ultrasonic output bedding experiment of the present invention (without preheating). 12(a) shows an example of the experimental conditions. Here, the experiment was carried out under the following conditions. Tip temperature: 180±5℃ Variable voltage setting (V): 14 Sunbonder display temperature (℃): 180±5 - Flooring material: Boron sponge

[0102] Figure 12(b) shows an example of the experimental results for ultrasonic output. Here, the horizontal items represent the following: Ultrasonic output (W) indicates the ultrasonic power W applied to the tip of the soldering iron. Solderability indicates ease of work and how well the solder adheres. Adhesion when bent was judged by the way the film peeled off when bent. · Film impact indicates the type of damage caused when the soldering iron is applied.

[0103] When the ultrasonic output (W) was varied from 1, 2, 3, . . . 10, experiments were conducted on the other three items, and the experimental results shown in Figure 12(b) were obtained. The results of this experiment showed that good results (ultrasonic soldering results) could be obtained for the three items with an ultrasonic output of about 7 W or more (preferably about 10 W).

[0104] Figure 13 shows an example of a temperature cycle test of the low-temperature solder of the present invention. This shows the interim results after 337.8 hours of the temperature cycle test. At this point in time, no change in adhesion was observed between the start of the experiment and the interim results for either ultrasonic soldering or non-ultrasonic soldering. [Brief explanation of the drawings]

[0105] [Figure 1] 1 is an explanatory diagram of low-temperature solder manufacturing according to the present invention; [Figure 2] 1 is an explanatory diagram of a low-temperature solder material manufacturing apparatus according to the present invention. [Figure 3] FIG. 2 is an explanatory diagram of low-temperature soldering of the lead wire of the present invention. [Figure 4] FIG. 2 is an explanatory diagram of low-temperature soldering according to the present invention. [Figure 5] 1 shows an example of the composition of a low-temperature solder according to the present invention. [Figure 6] 1 is a prototype example of the low-temperature solder of the present invention. [Figure 7] 1 is an example of soldering using the low-temperature solder of the present invention. [Figure 8] 1 is an example of soldering (metal-metal) using the low-temperature solder of the present invention. [Figure 9] 1 is an example of laminating a PET film according to the present invention. [Figure 10] This is an experimental example of a low-temperature solder covering material according to the present invention. [Figure 11] 1 shows an example of the results of a bonding test using low-temperature solder according to the present invention. [Figure 12] This is an experimental example of ultrasonic output bedding material of the present invention (without preheating). [Figure 13] 10 shows an example of a temperature cycle test of the low-temperature solder of the present invention. [Explanation of symbols]

[0106] 1: Solder material 2: Solder material tray 3: Melting furnace 4: Heater 11: Substrate (e.g. PET board 0.1mm thick) 12: Aluminum film (foil) 13, 13-1: Ultrasonic soldering iron tip 14: Low temperature soldering 15: Low temperature soldered ribbon or wire

Claims

1. A low-temperature solder containing Al, P, and Cu, with the balance being Sn and Bi, A low-temperature solder containing Al, P, and Cu, with the remainder being Sn and Bi, characterized in that the base material is an alloy of Sn and Bi, Al is a material that provides adhesion to the object to be soldered, and a main material is an alloy of Cu and P that is a material that removes oxides from the object to be soldered and provides adhesion, and the main material contains 1.5 wt% or less and 0.01 wt% or more of Al, P, and Cu relative to 100 wt% of the base material, an alloy of Sn and Bi, thereby enhancing adhesion.

2. 2. The low-temperature solder according to claim 1, which is used for soldering lead wires to electrodes of a solar cell substrate or a liquid crystal substrate.

3. The low-temperature solder described in claim 1 is characterized in that the adhesion strength is increased by one or more of the following adhesion strengths: alloying for metals, sintering for inorganic materials formed by firing oxides, and solidifying and adhering by entering into gaps in the surface irregularities of cellulose / resin materials, which are the objects to be soldered.

4. 4. A low-temperature solder according to claim 3, characterized in that the metal is aluminum, copper, iron, stainless steel, or silicon, the inorganic material is glass or ceramic, and the cellulose / resin is paper, wood, resin film, resin fiber, or carbon fiber.

5. 5. The low-temperature solder according to claim 4, wherein the soldering is ultrasonic soldering.

6. A low-temperature solder-coated lead wire, characterized in that the low-temperature solder according to any one of claims 1 to 5 is melt-coated onto the surface of a wire or ribbon.

7. A method for producing a low-temperature solder containing Al, P, and Cu, with the remainder being Sn and Bi, comprising: a step of mixing a base material which is an alloy of Sn and Bi, Al which is a material that provides adhesion to an object to be soldered, and a main material which is an alloy of Cu and P which is a material that removes oxides from the object to be soldered and provides adhesion, in an amount of 1.5 wt% or less and 0.01 wt% or more relative to 100 wt% of the base material, an alloy of Sn and Bi; melting and alloying the entrained materials; A method for producing a low-temperature solder containing Al, P, and Cu, with the remainder being Sn and Bi, characterized in that it has an improved adhesion.

8. 8. The method for producing low-temperature solder according to claim 7, wherein the method is used for soldering lead wires to electrodes of a solar cell substrate or a liquid crystal substrate.

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