JP2024042392A - solder wire - Google Patents

Abstract

To provide a solder wire that coats a resin on a coated flux in consideration of prevention of adhesiveness of a flux layer coated on the surface of a solder part, sanitation and fitness, in which the coated resin is not infiltrated and fused to a flux of a lower layer at normal temperature, has no adhesiveness and has such a structure not as to prevent the effect of the flux at the time of soldering.SOLUTION: A solder wire includes a solder part 2 composed of a solder alloy, a flux layer 3 coated on the surface of the solder part 2, and a resin layer 4 coated on the surface of the flux layer 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a solder wire compounded with flux for mounting various electronic components on printed wiring boards, and particularly to a solder wire suitable for preventing flux scattering and achieving stable soldering. be.

Conventionally, solder has been used to mount various electronic components on printed wiring boards. These solders are used by melting and alloying tin with the addition of various metals. Among them, haze-cored solder contains a resin composition called flux. Flux is used to remove oxide films at soldering points, to prevent oxidation of soldering points and molten solder, and to improve solder wettability.

Such flux-containing solder wire is generally a flux cored solder in which the flux is incorporated in the center of the solder portion made of a solder alloy. During soldering, when a soldering iron is brought into contact with a solder part, the flux in the center part softens before the solder alloy melts.

Next, bubbles and gas are generated in the flux that begins to soften. As a result, the pressure in the central part, which is sealed around by the solder part, increases due to the generated bubbles and gas.

Further, the heat from the soldering iron melts the solder part made of the solder alloy, but at this time, the pressure of the flux sealed in the center part is released all at once, causing the flux and solder to scatter.

Especially these days, when soldering must be completed in a very short period of time, the temperature of the soldering iron is often raised, but this causes the flux sealed in the center to expand rapidly, causing the flux and , scattering of solder particles becomes noticeable. A problem arises in that the scattered solder particles and flux induce malfunctions and defects in electronic components. Furthermore, when soldering parts by hand, there is a risk of burns if such flux or the like scatters, and there is also the problem that work safety is impaired.

In addition, in order to control the amount of metal in the solder part that makes up the outer shell of the central part that contains flux, it is complicated to manage two points, the inner diameter and the outer diameter, of the solder wire that contains flux. There was also the problem that the solder alloy that was directly exposed would oxidize in advance, reducing performance.

As a means to solve the above-mentioned difficulties, a flux that can be coated on the solder portion has been proposed (see, for example, Patent Documents 1 and 2).

However, according to the techniques disclosed in Patent Documents 1 and 2 mentioned above, if flux is applied to the surface and gripped by hand, the hands become sticky, which impedes workability, hygiene, and health. , there are safety issues, etc. In addition to this, there are also problems such as problems with bobbin winding and unwinding due to the stickiness of the flux.

Japanese Unexamined Patent Publication No. 55-54298 Japanese Unexamined Patent Publication No. 56-6798

Therefore, the present invention has been devised in view of the above-mentioned problems, and its purpose is to prevent the surface of the flux layer from directly touching the flux layer coated on the surface of the solder part. A resin layer is coated on the surface. The resin layer has the property of not infiltrating or fusing with the underlying flux at room temperature, and has the function of preventing surface stickiness. In addition, the resin layer must also have characteristics that allow it to easily fuse with the flux without interfering with the characteristics of the flux during soldering. The present invention provides a solder wire comprising a solder portion, a flux portion coated on the surface thereof, and a resin portion having the above-mentioned characteristics on the surface.

The solder wire according to the first invention is characterized by having a solder part made of a solder alloy, a flux layer coated on the surface of the solder part, and a resin layer coated on the surface of the flux layer.

A solder wire according to a second invention is characterized in that, in the first invention, the resin layer is made of acrylic resin.

In the solder wire according to a third invention, in the second invention, the resin layer contains 67% by mass or less of a structural unit derived from a methacrylic acid ester represented by the following general formula (1) as an optional component, and the following as an essential component: The structural unit derived from the (meth)acrylic ester represented by the general formula (2) is 5% by mass or more and 50% by mass or less, and the (meth)acrylic ester represented by the general formula (3) is used as an essential component. It is characterized by containing 5% by mass or more and 80% by mass or less of structural units derived from the above.

（式中、Ｒ¹は、水素又は炭素数１～３の直鎖状又は分岐状アルキル基である。）

(In the formula, R ¹ is hydrogen or a linear or branched alkyl group having 1 to 3 carbon atoms.)

（式中、Ｒ²は水素又はメチル基であり、Ｒ³は炭素数４～１６の直鎖状又は分岐状アルキル基である。）

(In the formula, R ² is hydrogen or a methyl group, and R ³ is a linear or branched alkyl group having 4 to 16 carbon atoms.)

（式中、Ｒ⁴は水素又はメチル基であり、Ｒ⁵は炭素及び水素からなる環状部分を有する官能基である。）

(In the formula, R ⁴ is hydrogen or a methyl group, and R ⁵ is a functional group having a cyclic portion consisting of carbon and hydrogen.)

According to the present invention having the above-described configuration, the resin layer is coated on the surface of the flux layer so as not to directly touch the flux layer coated on the surface of the solder part. The resin layer has the property of not infiltrating or fusing with the underlying flux at room temperature, and has the function of preventing surface stickiness. In addition, the resin layer must also have properties that allow it to be easily fused with the flux without interfering with the properties of the flux during soldering. The present invention provides a solder wire comprising a solder portion, a flux portion coated on the surface thereof, and a resin portion having the above-mentioned characteristics on the surface.

FIG. 1 is a sectional view of a solder wire to which the present invention is applied.

Hereinafter, a solder wire to which the present invention is applied will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a solder wire 1 to which the present invention is applied. The solder wire 1 includes a solder portion 2 made of a solder alloy, a flux layer 3 coated on the surface of the solder portion 2, and a resin layer 4 coated on the surface of the flux layer 3.

The solder alloy constituting the solder portion 2 is an alloy containing at least tin, and any solder alloy can be used, such as the lead-containing solder alloy shown in "4. Alloy system", "Type" and "Symbol" and the solder alloy shown in Table 1 of JIS Z 3282:2017, or the lead-free solder alloy shown in Table 2. In addition to tin, this solder alloy contains chemical components such as Sb, Bi, Cu, Au, In, Ag, Al, Cd, Fe, Ni, and Zn, each at their respective contents. The solder alloy is not limited to the range of chemical components shown in 4. Alloy system, type and symbol Table 1 and Table 2 of JIS Z 3282:2017, and may be composed of any other well-known range of chemical components.

The flux constituting the flux layer 3 is applied to the surface of the solder portion 2, and is a solid that has both flexibility and adhesiveness, and contains, for example, pine resin as a main component, a resin, an activator, a solvent, etc.

The resin layer 4 is laminated on the surface of the flux layer 3, and is made of, for example, acrylic resin, but is not limited thereto, and may be made of any resin material. This resin layer 4 contains 67% by mass or less of a structural unit derived from a methacrylic acid ester represented by the following general formula (1) as an optional component, and (meth)acrylic acid represented by the following general formula (2) as an essential component. 5% by mass or more and 50% by mass or less of structural units derived from acid esters, and 5% by mass or more and 80% by mass or less of structural units derived from (meth)acrylic acid esters represented by general formula (3) as an essential component. ,contains.

The resin layer 4 coated on the surface of the flux layer 3 does not interfere with the action of flux during soldering, and after coating the resin layer 4, the surface of the solder wire 1 becomes sticky. The premise is that it does not.

It is conceivable to copolymerize a fluorine-based monomer and a silicon-based monomer in this resin layer 4 as a coating that does not have a sticky surface. Fluorine is dangerous and unsuitable because it can generate hydrofluoric acid when heated with a soldering iron. Silicon is unsuitable because siloxane may scatter due to heat and cause contact failure in electronic components.

The fluorine-free acrylic polymer or silicone-free acrylic polymer is coated by any method. An easy coating method is to coat an acrylic polymer dissolved in a solvent. By using a fluorine-based solvent as the solvent, it is possible to prevent the flux from seeping into the resin layer 4.

（式中、Ｒ¹は、水素又は炭素数１～３の直鎖状又は分岐状アルキル基である。）

(In the formula, R ¹ is hydrogen or a linear or branched alkyl group having 1 to 3 carbon atoms.)

（式中、Ｒ²は、水素又はメチル基であり、Ｒ³は炭素数４～１６の直鎖状又は分岐状アルキル基である。）

(In the formula, R ² is hydrogen or a methyl group, and R ³ is a linear or branched alkyl group having 4 to 16 carbon atoms.)

（式中、Ｒ⁴は、水素又はメチル基であり、Ｒ⁵は炭素及び水素からなる環状部分を有する官能基である。）

(In the formula, R ⁴ is hydrogen or a methyl group, and R ⁵ is a functional group having a cyclic portion consisting of carbon and hydrogen.)

Below, we will explain examples of solder wire to which the present invention is applied. Note that the present invention is not limited to the following examples.

<Synthesis of acrylic polymer>
Methyl methacrylate (MMA) 22.5 g, methacrylic acid (MA) 1 g, cyclohexyl methacrylate (CHMA) 45 g, 2-ethylhexyl methacrylate (2EHMA) 31.5 g, butyl acetate 70 g (polymerization solvent), 2,2-azobisiso 0.3 g of butyronitrile (AIBN) (polymerization initiator) was placed in a glass round-bottomed flask having an internal capacity of 1 liter. Stirring blades were set in the center of the four palates and set in a three-one motor. Further, a cooling pipe, a thermometer, and a nitrogen pipe were set to this round-bottomed flask.

The round bottom flask was then placed into a water bath. The rotation speed was set to 100 rpm at room temperature, and the space inside the flask was replaced with nitrogen using a flow meter so that the flow rate was 250 to 350 ml/min, and the flask was left for 20 minutes.

After that, hot water of 40 to 50°C was poured into the water bath, and the temperature of the water bath was set to 85°C, and the temperature of the water was raised to 85°C.

The temperature inside the round-bottomed flask gradually increased, and based on the heat of reaction, reached the maximum temperature (88°C) about 1 hour after the hot water was added, and then slowly decreased to 83°C, and maintained a constant temperature. . Nitrogen was continuously supplied while keeping the temperature of the water bath constant for 6 hours from the time the hot water was added.

Six hours after the hot water was added, the inside of the round-bottomed flask had changed to a viscous liquid, so the nitrogen supply was stopped, and 100 g of butyl acetate was gradually diluted from the opening of the nitrogen pipe using a dropping funnel. .

Next, the liquid in this round bottom flask was extracted and used as a stock solution. An acrylic polymer was obtained by weighing 0.2 to 0.5 g of the stock solution into an aluminum cup using a precision balance and drying it in a drying oven at 150° C. for 40 minutes to remove the solvent component. The solid content of the acrylic polymer stock solution was measured from the weight after drying and was found to be 36.1% (reaction rate: 97.4%).

<Solution preparation>
2.8 g of the acrylic polymer stock solution, 5.2 g of butyl acetate, and 92 g of 1,3-bistrifluoromethylbenzene were stirred uniformly with a magnetic stirrer to prepare a solution.

<Preparation of solder wire>
A flux having the composition shown in Table 1 below was applied to the solder part with components consisting of Sn: 96.5% by mass, Ag: 3% by mass, and Cu: 0.5% by mass by immersion in a flux liquid. I let it happen. Thereafter, a resin layer made of an acrylic polymer was laminated by dipping the solder part coated with flux in an acrylic polymer solution and drying it. Table 2 shows the mass % of short chains corresponding to structural units derived from methacrylic ester represented by general formula (1) in the resin layer, and the mass % of short chains corresponding to structural units derived from methacrylic ester represented by general formula (2). The data are classified into % by mass of long chains corresponding to the structural units represented by the formula (3) and % by mass of cyclic structures corresponding to the structural units derived from the (meth)acrylate ester represented by the general formula (3).

なお、表２に示すモノマーの成分の表記は、以下である。ＭＭＡ：メチルメタクリレート、ＭＡ：メタクリル酸、ＩＢＸＭＡ：イソボルニルメタクリレート、ＩＢＸＡ：イソボルニルアクリレート、ＣＨＭＡ：シクロヘキシルメタクリレート、２ＥＨＭＡ：２－エチルヘキシルメタクリレート、２ＥＨＡ：２－エチルヘキシルアクリレート、ＢＭＡ：ｎ－ブチルメタクリレート、ＳＭＡ：ステアリルメタクリレート（炭素数１８）、Ｍ－９０Ｇ：メトキシポリエチレングリコールメタクリレート（新中村化学製）。

In addition, the notation of the components of the monomer shown in Table 2 is as follows. MMA: methyl methacrylate, MA: methacrylic acid, IBXMA: isobornyl methacrylate, IBXA: isobornyl acrylate, CHMA: cyclohexyl methacrylate, 2EHMA: 2-ethylhexyl methacrylate, 2EHA: 2-ethylhexyl acrylate, BMA: n-butyl methacrylate, SMA: stearyl methacrylate (carbon number 18), M-90G: methoxypolyethylene glycol methacrylate (manufactured by Shin Nakamura Chemical).

Next, each of the produced solder wires was subjected to a stickiness evaluation test based on JIS Z 3197:2021 Soldering Flux Test Method 8.5.1 Dryness Test described below.

In this test, powdered talc is liberally sprinkled on the surface of the flux residue on the specimen. The regulation requires that powdered talc be sprinkled on the surface with a soft bristle brush and then lightly brushed off twice in the same direction, and the extent of the dusting is visually inspected. Since it is suitable for the evaluation method of the solder wire surface of the present invention, it was carried out in accordance with this regulation to confirm the adhesiveness of the solder wire surface of the present invention.

The tools to be prepared are a soft bristle brush (camel hair or something similar) with a diameter of about 8 mm, and powdered talc with a maximum particle size of 0.01 mm.

As for the evaluation method, if the powdered talc can be easily removed by brushing, the flux is considered to be non-tacky, and this is considered to be a pass. If the powdered talc could not be removed by brushing, the flux was considered sticky and was rejected.

The solder wettability was evaluated based on JIS Z 3197:2021 Soldering Flux Test Method 8.3.1.1 Solder Spreading Test, and 65% or more was considered to be a pass.

In all of the invention examples 1 to 7, the components of the resin layer are within the ranges specified in the present invention. As a result, both the stickiness and wettability were good. In particular, invention example 5 is an example in which the resin layer does not contain short chains and is composed only of cyclic and long chains, and in this case too, the stickiness and wettability were excellent.

On the other hand, in Comparative Example 1, the annular shape was below the lower limit, so the wettability was poor. In addition, in Comparative Example 2, the long chain, short chain, and cyclic structure are all within the range specified in the present invention, but since the number of carbon atoms in the SMA constituting the long chain exceeds 16, both stickiness and wettability are good. It was getting worse. In Comparative Example 3, the long chain exceeded the upper limit, and the number of carbon atoms in the SMA that constituted the long chain exceeded 16, so both stickiness and wettability were deteriorated. In Comparative Example 4, the long chains exceeded the upper limit, resulting in poor stickiness and wettability. In Comparative Example 5, since the long chain was below the lower limit, the resin layer peeled off, and both stickiness and wettability could not be evaluated. In addition, in Comparative Example 6, since the annular shape exceeded the upper limit, both stickiness and wettability could not be evaluated. In Comparative Example 7, the wettability was deteriorated because the short chains exceeded the upper limit.

1 solder wire 2 solder portion 3 flux layer 4 resin layer

A solder wire according to a first invention includes a solder portion made of a solder alloy, a flux layer coated on the surface of the solder portion, and a resin layer coated on the surface of the flux layer , the resin layer is characterized by being an acrylic resin .

（式中、Ｒ¹は、水素又は炭素数１～３の直鎖状又は分岐状アルキル基である。）

（式中、Ｒ²は水素又はメチル基であり、Ｒ³は炭素数４～１６の直鎖状又は分岐状アルキル基である。）

（式中、Ｒ⁴は水素又はメチル基であり、Ｒ⁵は炭素及び水素からなる環状部分を有する官能基である。） In the solder wire according to the second invention, in the first invention, the resin layer contains 67% by mass or less of a structural unit derived from a methacrylic acid ester represented by the following general formula (1) as an optional component, and the following as an essential component: The structural unit derived from the (meth)acrylic ester represented by the general formula (2) is 5% by mass or more and 50% by mass or less, and the (meth)acrylic ester represented by the general formula (3) is used as an essential component. It is characterized by containing 5% by mass or more and 80% by mass or less of structural units derived from the above.

(In the formula, R ¹ is hydrogen or a linear or branched alkyl group having 1 to 3 carbon atoms.)

(In the formula, R ² is hydrogen or a methyl group, and R ³ is a linear or branched alkyl group having 4 to 16 carbon atoms.)

(In the formula, R ⁴ is hydrogen or a methyl group, and R ⁵ is a functional group having a cyclic portion consisting of carbon and hydrogen.)

Claims (3)

A solder part made of a solder alloy;
A flux layer coated on the surface of the solder part,
A solder wire comprising a resin layer coated on the surface of the flux layer. The solder wire according to claim 1, wherein the resin layer is an acrylic resin. The resin layer contains 67% by mass or less of a structural unit derived from a methacrylic acid ester represented by the following general formula (1) as an optional component, and (meth)acrylic acid represented by the following general formula (2) as an essential component. 5% by mass to 50% by mass of structural units derived from esters, and 5% by mass to 80% by mass of structural units derived from (meth)acrylic acid ester represented by general formula (3) as an essential component, The solder wire according to claim 2, characterized in that it contains:

(In the formula, R ¹ is hydrogen or a linear or branched alkyl group having 1 to 3 carbon atoms.)

(In the formula, R ² is hydrogen or a methyl group, and R ³ is a linear or branched alkyl group having 4 to 16 carbon atoms.)

(In the formula, R ⁴ is hydrogen or a methyl group, and R ⁵ is a functional group having a cyclic portion consisting of carbon and hydrogen.)

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