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

Abstract

PURPOSE: To provide a low-temperature solder, a method of manufacturing the low-temperature solder, and a low-temperature solder-coated lead wire, and in particular to provide an inexpensive low-temperature solder applicable to an electrode (aluminum, copper, etc.) on a resin film, the solder being made such that a low-temperature solder comprising an alloy of Sn and Bi, an alloy of Sn, Bi and In, or the like is mixed, melted and alloyed with one or more of Al, P, Sb, In and the like.CONSTITUTION: A low-temperature solder with enhanced adhesion is made such that a base material obtained by alloying Sn with Bi and / or In is mixed, melted and alloyed with a main material comprising one or more of Al, P, Sb, In (excluded if the base material contains In) and Ba in a total amount from 0.01 wt.% to 1.0-1.5 wt.% inclusive.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to metals such as aluminum and copper, resin films used for solar cell substrates and liquid crystal substrates, etc., low-temperature solder used for alumina and glass, a method for manufacturing low-temperature solder, and a low-temperature solder-coated lead wire.

Background Art

[0002] Conventionally, for soldering lead wires to electrodes of metals such as copper, solar cell substrates, liquid crystal substrates, etc., tin-lead solder has been widely used because of its high strength and low price.

[0003] Also, in the case of electrodes such as aluminum, since sufficient soldering strength cannot be obtained, a silver paste is applied and sintered, and a lead wire is soldered thereon with tin-lead solder.

[0004] Recently, there has been a strong demand for lead-free solder from the perspective of environmental pollution and the like.

[0005] Furthermore, there is a demand for forming a solar cell on a flexible resin film such as PET and soldering a lead wire to an electrode (aluminum electrode, copper electrode, etc.) thereof at a low temperature.

[0006] There is also a demand for forming or soldering an electrode on alumina, glass, etc.

[0007] There is also a demand for forming an electrode on a sheet-like material made of conductive fibers such as carbon fiber or soldering a lead wire.

[0008] There has also been a demand for forming an electrode on paper such as Japanese paper or soldering a lead wire at a low temperature.

Disclosure of the Invention

Problems to be Solved by the Invention

[0009] Conventional lead-free solders have problems such as being slightly weaker than tin-lead solder in terms of strength, and being too expensive to be a viable alternative.

[0010] Furthermore, with solar cells formed on resin films, a problem arose where the soldering temperature was too high.

[0011] Furthermore, there were problems such as the inability to form electrodes on alumina or glass, and the inability to perform low-temperature soldering.

[0012] Furthermore, there was the problem that it was not possible to form electrodes or solder lead wires at low temperatures onto sheets of conductive carbon fiber or similar materials.

[0013] Furthermore, there were problems such as the inability to form electrodes on paper like Japanese washi paper or to solder lead wires at low temperatures. [Means for solving the problem]

[0014] The inventors have discovered that low-temperature solder made from Sn, a type of lead-free solder, and an alloy of Bi, In, or Bi and In, can be melted and alloyed with one or more of the following: Al, P, Sb, In (except when the base material contains In), Ba, etc., in a total amount of 1 wt% to 1.5 wt% or less, and a trace amount of 0.01 wt% or more, and then bonded to metals such as aluminum, resin films, alumina, etc., with extreme strength at low temperatures.

[0015] Therefore, in a low-temperature solder made of an alloy of Sn and Bi, or In, or Bi and In, the present inventors have mixed a main material consisting of one or more of Al, P, Sb, In (except when the base material contains In), and Ba in a total amount of 1.0 to 1.5 wt% or less and 0.01 wt% or more into a base material which is an alloy of Sn and Bi, or In, or Bi and In with a purity of 4N or higher, and melted and alloyed it to enhance adhesion.

[0016] In this case, one or more of the following materials are used instead of Ba, or together with Ba, to enhance adhesion.

[0017] Furthermore, 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.

[0018] Furthermore, auxiliary materials consisting of alloys containing one or more of Al, P, Sb, In, and Ba are mixed into the base material as needed and then melted and alloyed.

[0019] Furthermore, the auxiliary alloy is made of a copper-polyester alloy.

[0020] Furthermore, the base material, main material, and auxiliary material are mixed together or in multiple parts before being melted and alloyed.

[0021] Furthermore, it is used for soldering electrodes on solar cell substrates and liquid crystal substrates, or for soldering lead wires.

[0022] Furthermore, by melting and alloying the materials to enhance adhesion, the materials to be soldered are alloyed for metals, sintered for inorganic materials formed by firing oxides, and solidified and fixed by filling gaps in the surface irregularities for cellulose / resin materials, thereby enhancing one or more of the adhesion forces.

[0023] Furthermore, the metals are at least aluminum, copper, iron, stainless steel, and silicon; the inorganic materials are at least glass and ceramic; and the cellulose / resins are at least paper, wood, resin film, resin fiber, and carbon fiber.

[0024] Furthermore, to enhance adhesion through melting and alloying, soldering is performed at temperatures at least 10°C higher than the melting point of 90°C for Sn-Bi alloys (139°C), 120°C for Sn-In alloys, and 90°C for Sn-In-Bi alloys to increase adhesion.

[0025] Also, soldering is performed by ultrasonic soldering.

[0026] Also, low-temperature solder is melt-coated on the surfaces of wire materials and ribbons.

[0027] Also, melt coating is performed with ultrasonic waves applied.

[0028] Also, ammonium bromide powder is mixed into BiSn solder at 3 wt% or less and 0.05 wt% or more to improve the solder adhesion strength.

Advantages of the Invention

[0029] As described above, for the low-temperature solder composed of Sn and an alloy of Bi, In, or Bi and In, a low-temperature solder obtained by melting and alloying by mixing one or more of Al, P, Sb, In (excluding when the base material contains In), Ba, etc. in a total amount of 1 wt% to 1.5 wt% or less and 0.01 wt% or more can be soldered extremely firmly to metals such as aluminum, resin films, etc., alumina, paper, etc. In particular, a low-temperature solder of Sn and Bi containing only a very small amount of In can be manufactured very cheaply.

[0030] Also, by regulating the total amount of the mixture, the melting temperature of the low-temperature solder after melting and alloying becomes the same as or lower than the melting temperature of the base material, and an increase in the melting temperature due to the mixture can be eliminated.

[0031] [[ID=二十九]]Also, by mixing one or more of Al, P, Sb, In (excluding when the base material contains In), Ba, etc. and melting and alloying to produce a low-temperature solder, the adhesion strength to the soldering target can be significantly enhanced.

[0032] Furthermore, low-temperature soldering has become possible not only for metals but also for resin films, alumina, glass, and Japanese paper. Here, it is presumed that low-temperature soldering achieves adhesion by alloying metals, sintering (low-temperature sintering) for inorganic materials formed by firing oxides (alumina, glass, etc.), and solidifying and fixing into the gaps of surface irregularities for cellulose / resin materials. For materials other than metals, it is preferable to apply ultrasound for low-temperature soldering, but even for metals, ultrasonic soldering results in a stronger solder bond. [Example 1]

[0033] Figure 1 shows an explanatory diagram of the low-temperature solder manufacturing process according to the present invention.

[0034] Figure 1(a) shows a flowchart, and Figure 1(b) shows examples of materials.

[0035] In Figure 1(a), S1 prepares the base material and main material. This involves preparing the following materials, as shown in the material example in Figure 1(b).

[0036] ·Base material: Sn42 Bi58 ·Main material: Al, GuP, In Here, the base material is the basic material (base material) that forms the alloy for the low-temperature solder of the present invention. For example, one alloy was used with 42 wt% Sn and 58 wt% Bi (melting temperature 139°C, eutectic alloy). The weight ratio of Sn and Bi can be arbitrary within the range in which the alloy can be created; for example, Bi can be 3 to 58 wt%, with the remainder being Sn. The appropriate ratio can be selected by experimenting with the melting temperature (the higher the amount of Bi, the lower the temperature; at 58 wt%, the melting temperature is 139°C) to obtain the desired value. Similarly, for other low-temperature solders, such as Sn-In and Sn-Bi-In systems, the appropriate ratio can be selected as shown in Figure 5 and its explanation.

[0037] Furthermore, the main material is a material that affects soldering during soldering, such as the removal of oxide film from the surface of the object to be soldered, adhesion, wettability, fluidity, and viscosity. In this invention, the total amount of the main material is 1 to 1.5 wt% or less, and 0.01 wt% or more. Here, it is a material that is mixed and melted / alloyed with one or more of the following: Al (adhesion to the object to be soldered), P (or CuP, oxide film removal and adhesion to the object to be soldered), In (wettability, fluidity), Sb (adhesion), and Ba (adhesion, see Figures 8 and 9). Also, the total amount of the main material is a trace amount of 1 to 1.5 wt% or less, and 0.01 wt% or more, so that the melting temperature of the low-temperature solder after mixing the main material with the base material and melting / alloying it is equal to or slightly lower (for example, about 1 to 3°C lower) than the melting temperature of the base material. This is presumed to be because the total amount of the main material is a trace amount, at most 1 to 1.5 wt% or less of the base material, and therefore enters the framework of the base material and re-forms the framework.

[0038] S2 involves mixing the main material with the base material. This means mixing the main material with the base material prepared in S1.

[0039] In step S3, the base material and main material melt and form an alloy. This is done by mixing the main material with the base material in step S2, heating and melting it, and stirring thoroughly to form an alloy. In cases where alloying is difficult due to oxidation of the main material by oxygen in the air, an inert gas (such as nitrogen gas) may be blown into the crucible as needed, or a melting furnace or vacuum melting furnace filled with inert gas may be used.

[0040] S4 is when the low-temperature solder material is completed.

[0041] As described above, by preparing the base material and main material, mixing them, and then melting and alloying them, it becomes possible to manufacture the low-temperature solder according to the present invention (Sn-Bi-based, Sn-In-based, and Sn-Bi-In-based low-temperature solder). The details will be explained below.

[0042] Figure 2 shows an explanatory diagram of the low-temperature solder material manufacturing apparatus of the present invention.

[0043] In Figure 2, solder material 1 is the base material and main material prepared in S1 of Figure 1 as described above, and in this case, it is metal fragments (coarsely ground).

[0044] The solder material input tray 2 is used to place the solder material 1 and then to put it into the melting furnace 3.

[0045] The melting furnace 3 is heated by a heater 4 or the like, into which solder material 1 is introduced, melting the base material and main material, and stirring to form an alloy. Normally, the melting furnace 3 melts the base material and main material introduced into it in the atmosphere and stirs to form an alloy. At this time, if necessary, an inert gas (such as nitrogen gas) is blown in to reduce oxidation by oxygen in the air, and if necessary, it is sealed and filled with inert gas (or evacuated under vacuum).

[0046] As described above, the base material and main material prepared in S1 of Figure 1 are mixed, melted in the melting furnace 3, stirred, and alloyed to produce the low-temperature solder of the present invention (Sn-Bi, Sn-In, and Sn-Bi-In low-temperature solder).

[0047] Figure 3 shows an explanatory diagram of low-temperature soldering of the lead wire according to the present invention.

[0048] Figure 3(a) shows a flowchart, and Figure 3(b) shows an example of a circuit board / lead wire.

[0049] In Figure 3(a), S11 is the process of pre-soldering the substrate pattern with low-temperature solder using ultrasound. For example, on a solar cell substrate (such as a 0.1mm thick PET board), the low-temperature solder of the present invention (the low-temperature solder produced in S4 in Figure 1) is supplied to the tip of an ultrasonic soldering iron to melt the portion (pattern) that is to be soldered, and ultrasound is applied to pre-solder the pattern portion on the substrate (referred to as ultrasonic pre-soldering).

[0050] S12 involves soldering the lead wires with or without ultrasound. This involves placing the lead wires along the areas (patterns) that were pre-soldered with ultrasound in S11, for example, on the electrodes (e.g., aluminum foil) of a solar cell substrate (PET board), and then melting the low-temperature solder of the present invention to solder the lead wires with or without ultrasound. Note that if the low-temperature solder has already been pre-soldered to the lead wires, no additional solder supply is necessary.

[0051] As described above, by performing pre-soldering of 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) using ultrasound (S11), and then ultrasonically soldering or non-ultrasonically soldering lead wires onto the pre-soldered part (pattern) using the low-temperature solder of the present invention (S12), it is possible to perform ultrasonically pre-soldering on the electrode part (aluminum foil part) of a solar cell substrate, etc., which is conventionally unsolderable, and then ultrasonically solder or non-ultrasonically solder lead wires onto it.

[0052] Furthermore, ultrasonic soldering is performed at a power level of 10W or less, typically between 0.5 and 3W. High power levels are avoided because they can damage the film (e.g., nitride film) formed on the solar cell substrate or the crystals on the substrate surface.

[0053] Figure 3(b) shows an example of a circuit board / lead wire.

[0054] In Figure 3(b), the substrate is a heat-resistant resin substrate such as PET (for example, a flexible resin substrate about 0.1 mm thick), which is an example of a substrate that is extremely difficult to solder using conventional soldering methods. The parts (patterns) that will become electrodes (aluminum electrodes, copper electrodes, etc.) on these substrates are pre-soldered using ultrasonic soldering with the low-temperature solder that provides adhesion according to the present invention. Then, by ultrasonically soldering or non-ultrasonic soldering the lead wires to these pre-soldered parts (patterns), it becomes possible to solder the lead wires to the substrate (aluminum electrodes, copper electrodes).

[0055] Furthermore, the lead wires are soldered to the electrode portion (pattern) on the substrate using the low-temperature solder that provides adhesion according to the present invention, and include wires (wires made by solder-plating (ultrasonic solder-plating) a circular copper wire with the low-temperature solder of the present invention; slightly flattening them into an oval shape makes soldering easier), ribbons (ribbons made by cutting a thin copper plate to a width of about 1 mm and pre-solder-plating (ultrasonic solder-plating) the low-temperature solder of the present invention), etc.

[0056] Figure 4 shows an explanatory diagram of the low-temperature soldering method according to the present invention.

[0057] Figure 4(a) shows an example of pre-soldering, and Figure 4(b) shows an example of soldering ribbon or wire.

[0058] In Figure 4(a), the substrate (e.g., PET board 0.1 mm thick) 11 is an example of a substrate for a solar cell, in which an aluminum film (foil) 12 is formed on the entire surface of the back surface of the substrate 11.

[0059] The aluminum film (foil) 12 is an electrode (aluminum electrode) formed by creating an aluminum foil (film) on the entire back surface of the illustrated substrate (PET plate) 11, which is the substrate of the solar cell (by bonding, vapor deposition, etc.).

[0060] 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).

[0061] The low-temperature solder 14 is the low-temperature solder of the present invention (the low-temperature solder manufactured in S4 in Figure 1).

[0062] Next, I will explain the soldering process.

[0063] (1) The substrate 11 is transported onto a preheating stand, fixed in place by vacuum suction, and preheated (for example, to about 130°C).

[0064] (2) Low-temperature solder 14 is automatically supplied to the tip 13 of the ultrasonic soldering iron shown in the figure, from the starting point to the ending point of the electrode pattern (strip-shaped pattern) to be formed on the aluminum film (foil) 12, and while melting, ultrasonic waves are applied and the tip is moved at a constant speed while keeping it close to the aluminum film (foil) 12 without rubbing, thereby forming a strip-shaped pre-solder pattern on the aluminum film (foil) 12.

[0065] As described above, it is possible to apply the low-temperature solder 14 of the present invention to an aluminum film (foil) 12 in a predetermined pattern of pre-soldering.

[0066] Figure 4(b) shows an example of low-temperature soldering of a ribbon or wire.

[0067] In Figure 4(b), the ultrasonic soldering iron tip 13-1 is a soldering iron tip that is heated with or without ultrasonic waves applied from an ultrasonic generator (not shown).

[0068] The low-temperature solder-coated ribbon or wire 15 is a ribbon or wire that has been pre-soldered with the low-temperature solder of the present invention. Note that the solderability is improved if the wire 15 is slightly deformed into an oval shape.

[0069] Next, we will explain the soldering process to the pre-soldered pattern portion of the ribbon or wire.

[0070] (1) Preheat the substrate 11 in the same manner as in Figure 4(a).

[0071] (2) The low-temperature solder-coated ribbon or wire 15 is positioned along the pre-solder pattern formed on the aluminum film (foil) 12 on the upper (back) side of the substrate 11. The tip of a soldering iron 13-1, with or without ultrasonic waves, is used to lightly press down on the ribbon or wire 14 from above and move it at a constant speed to the right as shown in the figure, melting the solder on the low-temperature solder-coated ribbon or wire 15 and soldering it to the pre-solder pattern.

[0072] As described above, it becomes possible to solder a ribbon or wire 15 that has been pre-soldered with the low-temperature solder 14 of the present invention to the pre-soldered pattern on the aluminum film (foil) 12.

[0073] Furthermore, the quality of the ultrasonic soldering and non-ultrasonic soldering according to the present invention is determined by applying ultrasonic soldering or non-ultrasonic soldering to the target area of ​​the ribbon or wire, pulling the ribbon or wire with a force slightly weaker than the force that would cause the substrate to break (bending force, approximately 0.5 to 2 kg), and determining that it is good if it does not peel off the substrate, and bad if it peels off.

[0074] Figure 5 shows an example of the composition of the low-temperature solder of the present invention.

[0075] In Figure 5, the base material and main material are the same as the distinction between base material and main material explained in Figure 1.

[0076] The composition examples show the composition of the base material and main material.

[0077] The wt% examples are examples of the wt% composition of the base material and main material.

[0078] The wt% range is an example of the wt% range of the composition of the base material and main material.

[0079] The composition, wt% example, and wt% range are as shown in Figure 5 below.

[0080] Base material Main material Remarks (Example of melting point) Composition example: Sn-Bi alloy Al P Sb In Melting point: e.g. 139℃ (Except when In is included 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 3 wt%, preferably 1.0-1.5 wt% or less. Here, as an example composition, the base material used in the prototype was Sn 42wt% and Bi 58wt% as shown in the figure. Furthermore, the composition range only needs to be stable within the range in which low-temperature solder alloys (Sn-Bi, Sn-In, and Sn-Bi-In solder alloys) can be fabricated. For example, a Sn-Bi solder alloy can consist of Bi 3wt% to 58wt% and the remainder being Sn, and the appropriate range should be selected experimentally by measuring the melting temperature of the fabricated low-temperature solder alloy (base material).

[0081] The main materials include Al.P (or CuP8), In, Bi, and Sb, but in the prototypes, P (red phosphorus) and CuP8 alloy (an alloy with 8 wt% P and the remainder being Cu, where the wt% of P is 8% of that of CuP8, resulting in copper phosphide) were used. In the case of P, saturation occurs at approximately 0.1 wt% (or approximately 0.16 wt% in the case of CuP8), and further addition significantly increases viscosity. Therefore, for normal use where fluidity and wettability are ensured, it is desirable to add P below saturation (the amount of P added should be about one-tenth of that of other materials (preferably around 0.1 wt% to 0.01 wt%)). Similarly, the same tendency exists for other main materials, so the optimal amount to add should be determined experimentally as needed. Furthermore, as will be explained later, if the purity of the base material (Bi,Sn) is 4N (impurities of 99.99 wt% or less), the lower limit of the main material may be even lower than 0.1 wt%, which is 0.04 wt%.

[0082] Furthermore, the total amount of the main material should be a maximum of 3 wt%, preferably 1 to 1.5 wt%, and ideally 0.1 wt% or more. Adding the main material within this range results in a melting temperature that is approximately the same as or only slightly lower than that of the base material.

[0083] Figure 6 shows a prototype example of the low-temperature solder of the present invention. The illustration shows examples of solders that can be used for soldering as described in Figure 4, out of many prototypes. Those that cannot be used have been omitted.

[0084] In Figure 6, the base material of the low-temperature solder of the present invention (low-temperature solder manufactured in S4 of Figure 1) is • Sn52 / In48 (Melting point: 120℃) • Sn42 / Bi58 (Melting point: 139℃) • Sn48 / Bi52 (Melting point: ) Sn40 / In40 / Bi20 (Melting point: 90°C) These four types were used.

[0085] The main materials used were metallic materials consisting of Al, CuP8, and In (0.5 wt% each). For CuP8, copper phosphide was used, with 8 wt% P and the remainder being Cu.

[0086] The sample number is the number of the prototype sample.

[0087] For the prototype samples described above, ultrasonic soldering with and without ultrasonic soldering were performed as shown in Figure 5, and only those that were successful are listed. Samples that could not be soldered have been omitted. The results are shown in Figure 7.

[0088] Figure 7 shows an example of soldering using the low-temperature solder of the present invention. Here, in Figure 7 • Ultrasonic soldering is a distinction between soldering with and without ultrasonic soldering.

[0089] The objects to be soldered are materials to be soldered using the low-temperature solder sample shown in Figure 7 of the present invention, and are distinguished as follows: Ai plate (0.1 mmt), Cu plate (0.1 mmt), Cu wire (0.3 to 0.4 mmφ) / ribbon (100 μmt, 50 μmt, 30 μmt), and Si wafer (0.2 mmt).

[0090] • ◎ indicates excellent adhesion of the low-temperature solder of the present invention to the object to be soldered (a force slightly weaker than the force required to break a Si wafer when a 0.4 mmφ tin-plated copper wire is soldered to it and pulled (tensile strength of approximately 0.5 to 2 kg)).

[0091] •△ indicates weak adhesion of the low-temperature solder of the present invention to the soldering target (a state in which a 0.4mmφ tin-plated copper wire soldered to it peels off when a little force is applied and pulled).

[0092] From the experiments shown in Figure 7, it was found that sufficient soldering strength can be obtained for Al plates, Cu plates, Cu wires / ribbons, and Si wafers when "ultrasound is used".

[0093] Furthermore, without ultrasound, the solder would peel off when pulled. Cleaning the surface of the object to be soldered sometimes resulted in very strong adhesion, but not always, making the results inconsistent.

[0094] Figure 8 shows an example of improved adhesion strength according to the present invention. Figure 8 shows the measured adhesion strength when the main material Ba is replaced with Co, V, Ba, Mg, Ge, Si, and also with none (no Ba, etc.). A detailed explanation follows below.

[0095] In Figure 8, Sample No. is the number of the low-temperature solder that was fabricated.

[0096] Base material: Bi58Sn42 indicates that the base material of the low-temperature solder contains 58 wt% Bi and 42 wt% Sn. It is desirable that both Bi and Sn in the base material have a purity of 4N or higher. A purity of 4N or higher means that it contains 99.99 wt% or less of impurities, and that the impurities are 0.01 wt% or less. In this invention, it is essential that the purity of Bi, Sn, and (In) in the base material is 4N or higher, the total amount of main materials is 1.5 to 1.0 wt% or less, and 0.01 wt% or more, with impurities being below the lower limit of 0.01 wt%. This is because a large amount of impurities reduces adhesion and other properties. In other words, if there are many impurities, the amount of those impurities is added to the total amount, exceeding 1.5 to 1.0 wt%, resulting in a decrease in adhesion, an increase in viscosity, and other deterioration of properties.

[0097] Main materials: Al, CuP, In, Sb, Ba, 0.1 wt% each indicates that the main materials of the low-temperature solder, such as Al, CuP, In, Sb, and Ba, each make up 0.1 wt% (0.1 wt% of the total base material when the total base material is considered to be 100 wt%).

[0098] 0.1 wt% of additives means that the amount of additives (additives such as Ba (which is also the main material) and V shown below) added to the low-temperature solder is 0.1 wt% (0.1 wt% is the percentage when the total base material is considered to be 100 wt%).

[0099] "Al plate 0.1mmt," etc., indicates a material suitable for low-temperature soldering.

[0100] In the table, double white circles indicate excellent adhesion.

[0101] White circles in the table indicate good adhesion.

[0102] The triangles in the table indicate weak contact.

[0103] The black circles in the table indicate that soldering was successful without the use of ultrasound.

[0104] Furthermore, good adhesion was defined as the amount of force required to break the 0.1mm thick silicon plate when a 0.4mm diameter tin-plated copper wire was soldered at low temperature using ultrasonic waves.

[0105] For example, the first sample number, "B196", • Base material: Bi 58 wt%, Sn 42 wt% ·Main material: Al, CuP, In, Sb each 0.1wt% ·Additive 0.1wt%:Co • 0.1mm thick aluminum plate: Excellent adhesion; soldering was possible without ultrasonic soldering.

[0106] • Cu board 0.1mm thick: Good adhesion • SUS plate 0.1mm thick: Good adhesion, soldering was possible without ultrasonic soldering.

[0107] • Silicone sheet 0.1mm thick: Good adhesion • Alumina plate 0.6mm thick: Good adhesion • 1mm thick glass plate: Good adhesion, soldering was possible without ultrasonic soldering.

[0108] Similarly, the result "B202" was obtained from sample No. "B197". Note that "B202" contains no additives.

[0109] From the above results, it was found that the adhesion strength of the additives (main materials) Ba to the Al plate, V to the glass plate, and Ge to the Al plate was improved. However, the adhesion strength of Al plates, Cu plates, SUS plates, silicon plates, etc., varies depending on the surface condition, so it is necessary to take appropriate measures according to the condition. In particular, for materials that could be soldered without ultrasound, if the surface was dirty or a lot of oxides had formed, low-temperature soldering was not possible, so it was necessary to apply ultrasound and perform low-temperature soldering.

[0110] Furthermore, improvements in adhesion were observed with other materials as well (e.g., Te, Mo, Ga compared to Ai boards), so it is necessary to determine the additives according to the target material for low-temperature soldering.

[0111] Figure 9 shows an example of ultrasonic (rubbing) / paste application according to the present invention. Figure 9 shows the adhesion strength measured for low-temperature soldering on Si plate, Al plate, Cu plate, stainless steel plate, alumina plate, and glass plate with and without ultrasonic waves, and with paste (ammonium bromide), paste (ammonium chloride hydrate), and paste (resin (rosin)) for B196 in Figure 8 described above.

[0112] In Figure 9, paste / ultrasonic / rubbing indicates one of the following when performing low-temperature soldering: with ultrasound, without ultrasound, without paste, with ammonium bromide paste, with ammonium chloride hydrate paste, or with resin paste (rosin).

[0113] The object to be soldered is the material to be soldered at low temperature, and represents one of the following: Si (wafer), Al plate, Cu plate, stainless steel plate, alumina plate, or glass plate.

[0114] For example, the first line, "Ultrasound applied (circle)" (no paste, ultrasound applied (circle), rubbed (-)), indicates that low-temperature soldering was performed using ultrasound, and the adhesion to all materials was excellent.

[0115] The second line, "rubbing," refers to a method of low-temperature soldering where the soldering iron tip is rubbed against the material without paste or ultrasonic waves, resulting in good adhesion between the metal Si, Al, and Cu plates.

[0116] The third line, "ammonium bromide," refers to a paste made of "ammonium bromide," without ultrasound or rubbing, and only the Cu plate showed excellent adhesion.

[0117] The fourth line, "Ammonium chloride hydrate," refers to a paste made of "Ammonium chloride hydrate," without ultrasonic testing or rubbing, and only the Cu plate showed excellent adhesion.

[0118] The fifth line, "resin (rosin)," refers to a paste that is "resin (rosin)," without ultrasound or rubbing, and only the Cu plate showed good adhesion.

[0119] From these results, it was found that when low-temperature soldering is performed using ultrasonic waves, excellent adhesion is achieved for all types of plates: Si, Ai, Cu, stainless steel, alumina, and glass.

[0120] Furthermore, without ultrasound, when using pastes (ammonium bromide, ammonium chloride hydrate) and resins (rosin), adhesion was excellent on Cu plates, but not on other materials. The b-bond paste (ammonium bromide) also adhered well to Al plates. For materials that did not adhere, a separate, special paste (flux) was required (excellent adhesion was obtained with ultrasound, and low-temperature soldering was possible after dissolving and removing surface oxides, etc.).

[0121] Figure 10 shows photographic examples of low-temperature soldering using the low-temperature solder of the present invention. Figure 10 shows photographic examples of low-temperature soldering using the low-temperature solder of the present invention, B196 in Figure 8, described above, on the following materials (a) to (n). Similar results (with differences in adhesion strength) have been obtained with other low-temperature solders of the present invention.

[0122] The materials for low-temperature soldering shown in (a) through (n) in Figure 10 are as follows:

[0123] (a) is an aluminum plate, 0.1 mm thick.

[0124] (b) is a copper plate, 0.1 mm thick.

[0125] (c) is a stainless steel plate, 0.1 mm thick.

[0126] (d) is a Si (wafer), 0.1 mm thick.

[0127] (e) is an alumina plate, 0.6 mm thick.

[0128] (f) is a glass plate, 1 mm thick.

[0129] (g) is a PET sheet, 0.5 mm thick.

[0130] (h) is a Teflon® sheet, 0.5 mm thick.

[0131] (i) is a mica sheet, approximately 0.5 mm thick.

[0132] (j) is a carbon fiber cloth, approximately 0.5 mm thick.

[0133] (k) is a glass fiber cloth, approximately 0.5 mm thick.

[0134] (l) is Japanese paper, approximately 0.02 mm thick.

[0135] (m) is Western paper (copy paper), approximately 0.02 mm thick.

[0136] (n) is a cardboard sheet, approximately 1 mm thick.

[0137] Furthermore, the lead wire on the left side of each low-temperature soldering material is a 0.4mm diameter tin-plated copper wire, while the one on the right side is a 1mm diameter alumina wire.

[0138] Next, we will explain the low-temperature soldering procedure.

[0139] In Figure 10, (a) shows that low-temperature solder was placed on a 0.1 mm thick aluminum plate and heated until melted. A 0.4 mm diameter tin-plated copper wire on the left and a 1 mm diameter aluminum wire on the right were placed on the plate as shown in the figure. Ultrasound was then applied to solder the low-temperature solder to the aluminum plate, tin-plated copper wire, and aluminum wire, respectively, and then the plate was cooled. The low-temperature solder can be heated by supplying heat from the soldering iron tip to melt it, or by placing it on a preheating device and supplying heat (for example, if the melting point of the low-temperature solder is 139°C, an appropriate temperature in the range of 144°C to 169°C, from +5°C to +30°C). Ultrasound should be supplied when the low-temperature solder is molten, and about 1W is sufficient. 10W is too strong, as the molten low-temperature solder will fly off as droplets, so it is necessary to select the optimal strength (for example, an appropriate value of about 0.1 to 3W) in the experiment.

[0140] Following the above procedure, tin-plated copper wire and aluminum wire were strongly soldered to an Al plate using low-temperature solder (the strength is greater than the force required to break a 0.4mmφ tin-plated copper wire soldered to a 0.1mmφ silicon plate as described later in (d) (approximately 0.4 to 2 kg) when pulled).

[0141] Similarly, (b), (c), and (d) were also strongly soldered at low temperatures. These demonstrated that strong low-temperature soldering was possible to copper plates, stainless steel plates, and silicon plates (wafers). From (a) to (d), it can be inferred that the low-temperature solder and the materials alloyed, resulting in a strong low-temperature solder bond.

[0142] Next, in Figure 10, (e) shows that low-temperature solder was placed on a 0.6 mm thick alumina plate and heated to melt it. A 0.4 mm diameter tin-plated copper wire on the left and a 1 mm diameter aluminum wire on the right were placed on the plate as shown in the figure. Ultrasound was then applied to solder the low-temperature solder to the aluminum plate, tin-plated copper wire, and aluminum wire, respectively, and then it was cooled. The low-temperature solder can be heated by supplying heat from the soldering iron tip to melt it, or by placing it on a preheating device and supplying heat (for example, if the melting point of the low-temperature solder is 139°C, an appropriate temperature in the range of 144°C to 169°C, from +5°C to +30°C). Ultrasound should be supplied when the low-temperature solder is molten, and about 1W is sufficient. 10W is too strong, as the molten low-temperature solder will fly off as droplets, so it is necessary to select the optimal strength (for example, an appropriate value of about 0.2 to 3W) in the experiment.

[0143] Following the above procedure, tin-plated copper wire and aluminum wire were successfully soldered to an alumina plate using low-temperature solder.

[0144] Similarly, (f) was also strongly soldered at low temperature. As a result, strong low-temperature soldering was possible on the alumina plate and the glass plate. From these (d) results, it can be inferred that (f) is an oxide (alumina is an oxide sintered body, and glass is an oxide molten body), and that the low-temperature solder was strongly fixed to the surface by ultrasonic waves (low-temperature sintering), resulting in a strong low-temperature soldering.

[0145] Next, in Figure 10, (g) shows that low-temperature solder was placed on a 0.6mm thick PET plate and heated to melt it. A 0.4mm diameter tin-plated copper wire on the left and a 1mm diameter aluminum wire on the right were placed on the plate as shown in the figure. Ultrasonic waves were then applied to solder the low-temperature solder to the aluminum plate, tin-plated copper wire, and aluminum wire, respectively, and then the plate was cooled. The low-temperature solder can be heated by supplying heat from the soldering iron tip to melt the solder, or by placing it on a preheating device and supplying heat (for example, if the melting point of the low-temperature solder is 139°C, an appropriate temperature in the range of 144°C to 169°C, from +5°C to +30°C). However, the former method resulted in better low-temperature soldering without excessive heating of the PET. The ultrasound should be supplied in a molten state with low-temperature solder, and a power level of around 1W is sufficient. 10W is too strong, as it will cause the molten low-temperature solder to fly off as droplets. Therefore, it is necessary to select the optimal power level (for example, an appropriate value of around 0.2 to 3W) through experimentation.

[0146] Following the above procedure, tin-plated copper wire and aluminum wire were successfully soldered to a PET board using low-temperature solder.

[0147] Similarly, (h) and (i) were also strongly soldered at low temperatures. These demonstrated that strong low-temperature soldering was possible on PET plates, Teflon plates, and mica plates. From these (g) results, it can be inferred that (i) is a plastic / inorganic material (PET and Teflon are plastics, while mica is inorganic and has a flat surface), and that the low-temperature solder adhered strongly to the surface by ultrasound, resulting in a solid low-temperature solder bond.

[0148] Next, in Figure 10, (j) shows that low-temperature solder was placed on a 0.5mm thick carbon fiber cloth and heated to melt it. A 0.4mm diameter tin-plated copper wire on the left and a 1mm diameter aluminum wire on the right were placed on top as shown in the figure. Ultrasonic waves were then applied to solder the low-temperature solder to the aluminum plate, tin-plated copper wire, and aluminum wire, respectively, and then the cloth was cooled. The low-temperature solder can be heated by supplying heat from the soldering iron tip to melt the solder, or by placing it on a preheating device and supplying heat (for example, if the melting point of the low-temperature solder is 139°C, an appropriate temperature in the range of 144°C to 169°C, from +5°C to +30°C). However, the latter method ensures that the opposite side of the carbon fiber cloth is also sufficiently heated, and combined with the application of ultrasonic waves described later, the low-temperature solder penetrates both the front and back surfaces, resulting in a strong bond. The ultrasound should be supplied in a molten state with low-temperature solder, and a power level of around 1W is sufficient. 10W is too strong, as it will cause the molten low-temperature solder to fly off as droplets. Therefore, it is necessary to select the optimal power level (for example, an appropriate value of around 0.2 to 3W) through experimentation.

[0149] Following the above procedure, tin-plated copper wire and aluminum wire were successfully soldered to carbon fiber cloth using low-temperature solder.

[0150] Similarly, (k) was also strongly soldered at low temperatures. These results demonstrate that carbon fiber cloth and glass fiber cloth can be strongly soldered at low temperatures. From these (j) results, it can be inferred that (k) is an inorganic cloth, and that the low-temperature solder penetrated around the fibers of the cloth using ultrasound, causing it to adhere strongly and resulting in a solid low-temperature solder bond.

[0151] Next, in Figure 10, (l) shows that low-temperature solder was placed on 0.5 mm thick Japanese paper and heated to melt it. A 0.4 mm diameter tin-plated copper wire on the left and a 1 mm diameter aluminum wire on the right were placed on top as shown in the figure. In this state, ultrasonic waves were applied to solder the low-temperature solder to the Japanese paper, tin-plated copper wire, and aluminum wire, respectively, and then it was cooled. The low-temperature solder can be heated by supplying heat from the soldering iron tip to melt the low-temperature solder, or by placing it on a preheating device and supplying heat (for example, if the melting point of the low-temperature solder is 139°C, an appropriate temperature in the range of 144°C to 169°C, from +5°C to +30°C). However, the former is convenient for fixing only the surface, while the latter is convenient for fixing by penetrating to both the surface and the back, so the appropriate method should be selected. The ultrasound should be supplied in a molten state with low-temperature solder, and a power level of around 1W is sufficient. 10W is too strong, as it will cause the molten low-temperature solder to fly off as droplets. Therefore, it is necessary to select the optimal power level (for example, an appropriate value of around 0.2 to 3W) through experimentation.

[0152] Following the above procedure, tin-plated copper wire and aluminum wire were successfully soldered to Japanese paper using low-temperature solder.

[0153] Similarly, (m) and (n) were also strongly soldered at low temperatures. As a result, strong low-temperature soldering was possible on Japanese paper, Western paper (copy paper), and corrugated cardboard. From these (l) and (n), it is presumed that they are made of pulp fibers, and that the low-temperature solder penetrated around the pulp fibers by ultrasound, strongly fixing and resulting in a strong low-temperature soldering. [Brief explanation of the drawing]

[0154] [Figure 1] This is an explanatory diagram for low-temperature solder manufacturing according to the present invention. [Figure 2] This is an explanatory diagram of the low-temperature solder material manufacturing apparatus of the present invention. [Figure 3] This is an explanatory diagram for low-temperature soldering of the lead wires of the present invention. [Figure 4] This is an explanatory diagram of the low-temperature soldering method of the present invention. [Figure 5] This is an example of the composition of the low-temperature solder of the present invention. [Figure 6] This is a prototype example of the low-temperature solder of the present invention. [Figure 7] This is an example of soldering using the low-temperature solder of the present invention. [Figure 8] This is an example of improved adhesion according to the present invention. [Figure 9] This is an example of ultrasonic (rubbing) / paste application according to the present invention. [Figure 10] This is a photographic example of low-temperature soldering using the low-temperature solder of the present invention. [Explanation of Symbols]

[0155] 1: Soldering materials 2: Solder material input 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 solder 15: Low-temperature soldered ribbon or wire

Claims

1. In a low-temperature solder made of Sn and Bi, or In, or an alloy of Bi and In, A low-temperature solder characterized by enhanced adhesion during soldering, comprising a base material which is an alloy of Sn with a purity of 4N or higher, Bi or In with a purity of 4N or higher, or Bi and In with a purity of 4N or higher, and a main material consisting of an alloy of Al, Cu and P as a minimum, and optionally one or more of Sb, In (except when In is included in the base material), and Ba, in a total amount of 1.5 wt% or less and 0.01 wt% or more.

2. The low-temperature solder according to claim 1, characterized in that it contains one or more of V, Co, Cr, Ni, Ge, and Si within the content range of the main material, thereby enhancing adhesion during soldering.

3. The low-temperature solder according to claim 1 or 2, characterized in that the melting temperature of the low-temperature solder after melting and alloying is the same as or lower than the melting temperature of the base material.

4. The low-temperature solder according to any one of claims 1 to 3, characterized in that a secondary material made of an alloy containing one or more of Al, Sb, In, and Ba is mixed into the base material within the range of the content of the main material.

5. The low-temperature solder according to any one of claims 1 to 4, characterized in that the base material, main material, and auxiliary material are mixed together.

6. The low-temperature solder according to any one of claims 1 to 5, characterized in that it is used for soldering electrodes of solar cell substrates, liquid crystal substrates, or lead wires.

7. The low-temperature solder according to any one of Claims 1 to 6, characterized in that, when soldering, it enhances one or more of the following: alloying in the case of metal or silicon, sintering in the case of inorganic materials formed by firing oxides, and solidifying and fixing by entering into gaps in surface irregularities in the case of cellulose / resin materials.

8. The low-temperature solder according to claim 7, characterized in that the metal is aluminum, copper, iron, or stainless steel, the inorganic material is glass or ceramic, and the cellulose / resin is paper, wood, resin film, resin fiber, or carbon fiber.

9. The low-temperature solder according to any one of claims 7 to 8, characterized in that the adhesion during soldering is enhanced by soldering at a high temperature of at least 10°C above the melting point of Sn-Bi alloy (139°C), at least 120°C above the melting point of Sn-In alloy, and at least 90°C above the melting point of Sn-In-Bi alloy.

10. The low-temperature solder according to any one of claims 6 to 9, characterized in that the soldering is ultrasonic soldering.

11. A low-temperature solder-coated lead wire characterized by having the low-temperature solder described in claims 1 to 10 melt-applied to the surface of a wire or ribbon.

12. The melt coating is characterized in that the melt coating is performed while ultrasonic waves are applied. Low-temperature solder-coated lead wires as described.

13. A low-temperature solder characterized by having the low-temperature solder content set to 100 wt% and ammonium bromide powder added in an amount ranging from 3 wt% to 0.05 wt% or more, as described in any one of claims 1 to 12, thereby improving solder adhesion.

14. In a method for manufacturing low-temperature solder made of Sn and Bi, or In, or an alloy of Bi and In, The process involves mixing a base material, which is an alloy of Sn with a purity of 4N or higher, and Bi or In with a purity of 4N or higher, or Bi and In with a purity of 4N or higher, with a main material consisting of an alloy of Al, Cu and P (essential), and optionally one or more of Sb, In (except when In is included in the base material), and Ba, in a total amount of 1.5 wt% or less and 0.01 wt% or more. The steps include melting the mixed materials to form an alloy, A method for manufacturing low-temperature solder, characterized by having a feature that enhances adhesion during soldering.

15. A method for producing low-temperature solder according to claim 14, characterized in that it contains one or more of V, Co, Cr, Ni, Ge, and Si within the range of the content of the main material, thereby enhancing the degree of adhesion during soldering.

16. The method for manufacturing low-temperature solder according to claim 14 or 15, characterized in that the melting temperature of the low-temperature solder after melting and alloying is the same as or lower than the melting temperature of the base material.

17. A method for producing low-temperature solder according to any one of claims 14 to 16, characterized in that a secondary material made of an alloy containing one or more of Al, Sb, In, and Ba is mixed into the base material within the range of the content of the main material, and then melted and alloyed.

18. A method for manufacturing low-temperature solder according to any one of claims 14 to 17, characterized in that the base material, main material, and auxiliary material are mixed together.

19. A method for manufacturing low-temperature solder according to any one of claims 14 to 18, characterized in that it is used for soldering electrodes of solar cell substrates, liquid crystal substrates, or lead wires.

20. A method for producing low-temperature solder, characterized in that the low-temperature solder according to any one of claims 14 to 19 is mixed with ammonium bromide powder in an amount of 3 wt% or less to 0.05 wt% or more, with the low-temperature solder content being 100 wt%, thereby improving the solder adhesion.

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