JP7614672B2 - Flux and Soldering Methods - Google Patents

Description

The present invention relates to fluxes and other materials used in soldering, and in particular to a flux and soldering method that can solder enamel-coated aluminum wire without stripping the enamel, as well as electrical and electronic components soldered using the flux.

Enamel-coated coil wire (hereafter referred to as "enameled wire") is a conductor wire that is coated with a resin such as polyurethane so that the wires do not conduct electricity even if they touch each other. The coating is very thin, so there is no short circuit even if the wires touch each other when winding the coil, and the volume of the wire when wound is not large. Therefore, enameled wire is also called magnet wire.

Enamelled wire is basically joined by removing the enamel from the surface and then soldering in the usual way. The flux used in this process is the usual flux, which mainly consists of rosin made of abietic acid, and isopropyl alcohol as a solvent to dissolve the rosin, as well as activators and other additives.

Enameled wires come in two types: those with a conductor made of copper (hereafter referred to as "enameled copper wire") and those with a conductor made of aluminum (hereafter referred to as "enameled aluminum wire"). When the conductor is made of aluminum, its specific gravity is lighter than that of copper, so it is possible to make the coils lighter even when they are wound many times, and by using inexpensive aluminum, it is possible to reduce the product price.

Patent document 1 discloses a method of removing enamel using ultrasonic vibrations and then soldering.

Patent Document 2 also discloses a flux for aluminum soldering that is a mixture of 3.0 to 5.0 mass% fluorinated metal salts, 10.0 to 30.0 mass% metal salts of organic acids, and the remainder being hydrofluorides of amino alcohols.

Patent No. 6177383 JP 2002-059293 A

Enamelled copper wire has extremely high solder wettability to copper, so the copper wire can be wetted with molten solder and regular flux alone. In other words, soldering is possible without having to strip the enamel. However, in the case of enamelled aluminum wire, even if the molten solder dissolves the enamel on the surface, it is not possible to sufficiently wet the solder and aluminum conductor wire. Also, flux for aluminum conductor wire cannot strip the enamel, so the enamelled aluminum wire and solder cannot be wetted with molten solder and regular flux alone.

The present invention was conceived in consideration of the above problems, and provides a flux that can wet solder and enameled aluminum wire without stripping the enamel.

More specifically, the flux according to the present invention comprises 25 to 75 mass % of N-methyl-2-pyrrolidone as a solvent based on the total amount of the flux,
1.2 to 5.0 mass % of cyclohexylamine hydrofluoride as an activator based on the total amount of the flux;
The flux is characterized in that it is used when soldering an enameled wire containing rosin in an amount of 20 to 50 mass % of the total amount of the flux.

The flux of the present invention allows soldering using only the heat of the solder without stripping off the enamel on the conductor wire, because the solvent melts the enamel and the activator melts the surface layer of the conductor wire. In particular, it allows soldering even when the conductor wire is an aluminum wire, and even lightweight enamel-coated aluminum wire (enameled aluminum wire) can be soldered effectively.

FIG. 2 is a diagram showing the appearance of objects to be joined used in the experiment. FIG. 1 is a diagram illustrating the steps of an experiment.

The flux according to the present invention will be described below with reference to drawings and examples. Note that the following description illustrates one embodiment of the present invention and one example, and the present invention is not limited to the following description. The following description can be modified without departing from the spirit of the present invention.

The flux according to the present invention is composed of rosin, a solvent, and an activator. The rosin may be a conventional rosin made of abietic acid, hydrogenated rosin, ester rosin, acrylic modified rosin, etc. The rosin content is preferably 20 to 50% by mass based on the total amount of the flux.

The solvent should have a boiling point below 400°C and be a good solvent for resin. Here, 400°C is the general soldering temperature for lead-free solder. In other words, it can be said to be a good solvent for resin with a boiling point below the melting point of lead-free solder. If the solvent has a boiling point below 400°C, it can be evaporated and removed during the soldering process.

Specifically, 2-pyrrolidone, N-methyl-2-pyrrolidone, 3-methylphenol, trichloromethane, hexafluoro-2-propanol, 2-chlorophenol, and other good solvents for polyurethane are suitable. 2-pyrrolidone and N-methyl-2-pyrrolidone are particularly suitable. These may be used alone or in combination.

The solvent should be 25-75% by mass of the total flux. If it is less than this, the enamel will not dissolve, and if it is more than this, the content of rosin and activator will be too low to wet the aluminum wire and solder. The solvent dissolves the enamel to expose the conductor.

The activator dissolves the enamel, removes the metal oxide film from the exposed surface of the conductor, and makes it easier for the solder to wet. In particular, when the conductor is made of aluminum, it is preferable to use an activator that can remove the strong oxide film and that only works at the high temperatures used during soldering and not at room temperature. Among these, organic hydrofluorates are preferably used.

Specifically, amine hydrofluorides are suitable. Specifically, hydrofluorides of cyclohexylamine, 1,3-diphenylguanidine, N,N'-diethylaniline, diethylamine, etc. can be used.

If amine hydrochloride or hydrobromide is used instead of amine hydrofluoride, the oxide film removal ability is weak, and the activator cannot complete the removal of the oxide film on the aluminum surface and soldering.

In addition, when hydrofluoric acid, an inorganic acid, or sodium fluoride, a non-amine salt, is used, they exhibit the ability to remove oxide films not only at the high temperatures used during soldering, but also at room temperature after soldering is completed, causing corrosion and subsequent destruction at the soldered points.

Amine hydrofluoric acid salts may be used alone or in combination. Activators are added in an amount of 1.2 to 5.0 mass% based on the total amount of flux. If the amount is less than 1.2 mass%, solderability will be poor, and if the amount added exceeds this amount, a large amount of fluorine will remain in the flux residue, which may cause problems such as corrosion at the soldered points and reduced electrical reliability.

In addition, the flux of the present invention can be suitably used as a coactivator with organic bromides that generate hydrobromic acid at soldering temperatures, such as 2,3-dibromo-1-propanol, 1,2,5,6,9,10-hexabromocyclododecane, tris(2,3-dibromopropyl)isocyanurate, and 2,2-bis(4-bromomethyl)-1,3-propanediol.

These auxiliary activators continue to provide a gentle oxide removal effect even after the oxide film on the surface of the aluminum wire has been removed with amine hydrofluoride, preventing the re-oxidation of the aluminum and ensuring good solderability.

The auxiliary activator is preferably added in an amount of 0.5 to 5 mass% based on the total amount of flux. If the amount added is less than this amount, the oxide removal effect will not be obtained, and if the amount added is more than this amount, a large amount of halogen will remain in the flux residue, which may cause problems with corrosivity and electrical reliability.

Next, we will explain the soldering method using the flux according to the present invention. The flux according to the present invention has an appropriate viscosity because it contains rosin. Therefore, soldering can be performed by immersing the contact parts in the flux while the enameled wire and the objects to be joined are in contact with each other, and then immersing them in molten solder. After these steps, a step of cleaning the soldered objects may be performed.

The object to be joined here is a conductive metal. Usually, it is a material that is usually used as a conductor or terminal material in electric circuits or electronic circuits, such as copper, iron, aluminum, gold, silver, or alloys of these. The enameled wire can be enameled copper wire or enameled aluminum wire. Bringing the enameled wire into contact with the object to be joined means that there is at least some contact between the enameled wire and the object to be joined. Also, as long as the object to be joined and the enameled wire are very close to each other, they do not have to be in contact.

The flux according to the present invention can wet even enameled aluminum wire with solder. Therefore, if the object to be joined and the enameled wire are very close to each other, they can be electrically joined by solder. The distance is about 0.1 mm. In other words, in this invention, when the enameled wire and the object to be joined are brought into contact and fixed, this includes not only cases where they are actually in contact, but also cases where the enameled wire and the object to be joined are placed in close proximity. The enameled wire and the object to be joined that are brought into contact and fixed are called the "object to be joined".

Next, the objects to be joined are immersed in the flux according to the present invention. Here, it is sufficient to immerse the part of the objects to be joined where the objects to be joined and the enamel wire are in contact and fixed in the flux. In other words, the part where you want to solder the enamel wire and the objects to be joined is immersed in the flux.

Next, the objects to be joined, with the flux attached, are immersed in molten solder. The flux does not need to be dry when immersing in the molten solder. In other words, the objects to be joined can be immersed in flux and then immediately immersed in molten solder.

During the process of immersing in molten solder, the items to be joined that have flux attached to them do not need to be held in the molten solder, and can be pulled out immediately after the entire part that has flux attached to it is immersed in the molten solder.

The immersion in the flux and the immersion in the molten solder may be done not just once, but multiple times. In other words, the items to be joined are immersed in the flux and then immersed in the molten solder. This counts as one set, and this set may be done multiple times. By repeating the immersion in the flux and the molten solder, the wettability of the solder to the enameled wire can be improved.

After immersion in the molten solder, the objects to be joined may be washed. The flux according to the present invention is composed of components with a boiling point of 400°C or less, so it will all evaporate when immersed in the molten solder. However, in the unlikely event that any remains, this is to avoid corrosion of the objects to be joined.

The joining method using the flux according to the present invention can be suitably used for joining enameled wire to electrical or electronic components. In other words, the objects to be joined can be electrical or electronic components that use enameled wire. In particular, it can be suitably used for joining enameled wire to terminals of components such as electromagnets, motor rotors and stators, and inductors, which are made by winding enameled wire.

In order to confirm the effect of the flux according to the present invention, the following experiment was carried out.
<Solderability test>
An enamel-coated aluminum coil wire was wound around a wiring terminal (0.64 x 0.64 x 20 mm, tin-plated over nickel), after which the test flux was applied and the terminal was immersed in molten solder in a solder bath (solder temperature: 400°C, solder composition: 96.1 tin, 3.5 silver, 0.4 mass % nickel).

Figure 1 shows the appearance of the sample used. Figure 1(a) is a motor rotor 10. The rotor 10 is configured with two wiring terminals 10b (10ba and 10bb) attached to a main body 10a formed of a cylindrical insulating material. Referring to Figure 1(b), an enameled aluminum wire 12 was wound around one of the wiring terminals 10ba. The enameled aluminum wire 12 was also wound around the main body 10a, and was wound up to the other wiring terminal 10bb. Here, the wiring terminal 10b is the object to be joined 14, and the wiring terminal 10b around which the enameled aluminum wire 12 is wound is the object to be joined 16.

Refer to FIG. 2. First, the objects to be joined 16 are immersed in the above-mentioned flux 18 (P100). After that, the objects to be joined 16 are immersed in molten solder 20 prepared in a solder bath 20a (P102). The objects to be joined 16 are pulled out of the molten solder 20 (P104). At this time, there are cases where the solder does not wet the parts of the objects to be joined 16, which are the wiring terminals 10b to which the enameled aluminum wires 12 are fixed.

The object to be joined 16 was again immersed in the flux 18 (P106), again immersed in the molten solder 20 (P108), and then pulled out (P110). In other words, immersion in the flux 18 and the molten solder 20 was performed twice in succession.

The completed soldering was visually evaluated, and a "◎" (meaning an excellent pass) was given if the solder had sufficiently wetted the wiring terminal 10b and the enameled aluminum wire 12 to form an integrated unit; a "◯" (meaning pass) was given if the wettability was slightly poor but still good enough to be used as a product; and an "×" (meaning fail) was given if the wettability was insufficient and it was predicted that there would be poor conductivity or a high possibility of poor conductivity occurring, making it unusable as a product.

At the same time, an experiment was also conducted in which an aluminum plate without enamel was coated with flux and then immersed in molten solder.

The composition of the flux according to the present invention is shown below.
Example 1
Hydrogenated rosin (rosin) 46.8% by mass,
2-pyrrolidone (2-P) as a solvent: 50.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Example 1.

Example 2
Hydrogenated rosin (rosin) 46.8% by mass,
Solvent: N-methyl-2-pyrrolidone (NM2-P) 50.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Example 2.

Example 3
Hydrogenated rosin (rosin) 46.8% by mass,
Solvent: Isopropyl alcohol (IPA) 20.0% by mass
and 2-pyrrolidone (2-P) 30.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Example 3.

Example 4
Hydrogenated rosin (rosin) 46.8% by mass,
Solvent: Isopropyl alcohol (IPA) 20.0% by mass
and N-methyl-2-pyrrolidone (NM2-P) 30.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Example 4.

Example 5
Hydrogenated rosin (rosin) 47.7% by mass,
Solvent: Isopropyl alcohol (IPA) 20.0% by weight
and N-methyl-2-pyrrolidone (NM2-P) 30.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
No auxiliary activator The above materials were mixed to prepare the flux of Example 5.

Example 6
Hydrogenated rosin (rosin) 21.8% by mass,
2-pyrrolidone (2-P) as a solvent: 75.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Example 6.

(Example 7)
Hydrogenated rosin (rosin) 21.8% by mass,
Solvent: Isopropyl alcohol (IPA) 20.0% by weight
and 2-pyrrolidone (2-P) 55.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Example 7.

(Example 8)
Hydrogenated rosin (rosin) 47.9% by mass,
2-pyrrolidone (2-P) as a solvent: 50.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 1.2% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Example 8.

(Comparative Example 1)
Hydrogenated rosin (rosin) 46.8% by mass,
Solvent: Isopropyl alcohol (IPA) 50.0% by weight
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Comparative Example 1.

(Comparative Example 2)
Hydrogenated rosin (rosin) 47.0% by mass,
2-pyrrolidone (2-P) as a solvent: 50.0% by mass
Diethylamine hydrochloride (DAHC) 2.1% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Comparative Example 2.

(Comparative Example 3)
Hydrogenated rosin (rosin) 47.0% by mass,
Solvent: N-methyl-2-pyrrolidone (NM2-P) 50.0% by mass
Diethylamine hydrochloride (DAHC) 2.1% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Comparative Example 3.

(Comparative Example 4)
Hydrogenated rosin (rosin) 11.8% by mass,
2-pyrrolidone (2-P) as a solvent: 85.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 2.3% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Comparative Example 3.

(Comparative Example 5)
Hydrogenated rosin (rosin) 48.5% by mass,
2-pyrrolidone (2-P) as a solvent: 50.0% by mass
Cyclohexylamine hydrofluoride (CHAH) 0.6% by mass as an activator
0.9% by weight of 2,3-dibromo-1-propanol (DBH) as a coactivator
The above materials were mixed to prepare the flux of Comparative Example 3.
Table 1 shows the composition and evaluation of each sample.

With reference to Comparative Example 1, the solder wetted well to the uncoated aluminum plate, but barely wetted the enameled aluminum wire (referred to as "enamel-coated aluminum wire" in the table). In other words, the activator cyclohexylamine hydrofluoride (CHAH) and the co-activator 2,3-dibromo-1-propanol (DBH) were able to wet the solder well to the aluminum, but isopropyl alcohol (IPA) was unable to strip the enamel.

On the other hand, looking at Examples 1 and 2, it was found that the solder was able to wet not only the uncoated aluminum plate but also the enameled aluminum wire well. In other words, solvents such as 2-pyrrolidone (2-P) and N-methyl-2-pyrrolidone (NM2-P) were able to strip the enamel.

Also, referring to Examples 3 to 5, as long as there is a certain amount of organic hydrofluoric acid salt, it may contain a solvent that could not strip enamel, such as isopropyl alcohol (IPA).

In addition, in Example 5, the enameled aluminum wire was able to be wetted even without the auxiliary activator. In other words, the auxiliary activator is not an essential component for the flux of the present invention.

In addition, all examples were rated "◎" (meaning excellent pass) for enameled copper wire as well.

As described above, the flux according to the present invention can be suitably used for soldering enamel-coated conductor wires without stripping off the enamel. In this case, the conductor wire may be either copper or aluminum.

REFERENCE SIGNS LIST 10 rotor 10a main body 10b wiring terminal 12 enameled aluminum wire 14 workpiece 16 workpiece to be joined 18 flux 20 molten solder 20a solder bath 22 part not wetted with solder

Claims (4)

N-methyl-2-pyrrolidone as a solvent in an amount of 25 to 75% by mass of the total amount of the flux;
1.2 to 5.0 mass % of cyclohexylamine hydrofluoride as an activator based on the total amount of the flux;
A flux used for soldering an enameled wire, the flux containing 20 to 50 mass % of rosin based on the total amount of the flux. The flux described in claim 1 further contains 0.5 to 5.0 mass % of 2,3-dibromo-1-propanol as a coactivator based on the total amount of the flux. a step of contacting and fixing an enameled wire and an object to be joined to form an object to be joined;
A step of immersing the objects to be joined in the flux according to claim 1 or 2;
a step of immersing the objects to be joined in molten solder to form a joined object in which the enameled wire and the objects to be joined are welded together. The method for soldering an enamel wire according to claim 3, further comprising a step of cleaning the joint.