JP7199769B1 - solder wire - Google Patents

Abstract

Kind Code: A1 To prevent stickiness of a flux layer coated on the surface of a solder part, and in consideration of sanitation and health, a resin is coated on the coated flux, and the coating resin is the underlying flux. and To provide a solder wire having a structure which does not infiltrate, fuse, and stickiness at room temperature, and which does not interfere with the action of flux during soldering. A solder part (2) made 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) are provided. [Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to a solder wire in which flux is compounded for mounting various electronic components on a printed circuit board, and more particularly to a solder wire suitable for preventing scattering of flux and realizing stable soldering. be.

Conventionally, solder is used to mount various electronic components on printed wiring boards. Such solder is mainly composed of tin and various metals are added, melted and alloyed for use. Among them, flux cored solder contains a resin composition called flux. Flux is used to remove oxide films from soldering locations, prevent oxidation of soldering locations and molten solder, and improve wettability of solder.

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

Next, bubbles and gas are generated in the flux that has begun to soften. As a result, the pressure in the central portion, whose periphery is sealed with the solder portion, increases due to the generated air bubbles and gas.

Furthermore, the solder portion composed of the solder alloy is melted by the heat from the soldering iron, but at this time, the pressure of the flux sealed in the central portion is suddenly released, causing the flux and solder to scatter.

Especially recently, when soldering must be completed in a very short time, the temperature of the soldering iron is often raised. , the scattering of solder particles becomes conspicuous. A problem arises in that the scattered solder particles and flux induce malfunctions and failures of electronic components. In addition, when the soldering portion is manually soldered, there is a risk of burns if such flux or the like scatters, and there is also the problem that the safety of the work is impaired.

In addition, in order to control the amount of metal in the solder portion that forms the outer shell of the central portion that contains the flux, it is complicated to manage the inner and outer diameters of the solder wire that contains the flux. There is also the problem that the directly exposed solder alloy is oxidized in advance, degrading performance.

As a means for solving the above-described difficulties, fluxes that can be coated on solder portions have been proposed (see, for example, Patent Documents 1 and 2).

However, according to the techniques disclosed in Patent Documents 1 and 2 described above, when the flux is applied to the surface and held by the hand, the hand becomes sticky, which hinders workability, hygiene, and health. , safety issues, etc. In addition to this, problems such as bobbin winding and unwinding problems arise due to the stickiness of the flux.

JP-A-55-54298 JP-A-56-6798

SUMMARY OF THE INVENTION Accordingly, the present invention has been devised in view of the above-described problems, and its object is to prevent direct contact with the flux layer coated on the surface of the solder part. is coated with a resin layer. The resin layer has a characteristic of not infiltrating or fusing with the underlying flux at room temperature, and has a function of preventing surface tackiness. In addition, the resin layer must also have the property of being 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 its surface, and a resin portion having the above-described properties on its surface.

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

(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.)

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

（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。）

(Wherein, 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 configured as described above, the surface of the flux layer is coated with the resin layer so as not to come into direct contact with the flux layer coated on the surface of the solder portion. The resin layer has a characteristic of not infiltrating or fusing with the underlying flux at room temperature, and has a function of preventing surface tackiness. In addition, the resin layer must also have the property of being 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 its surface, and a resin portion having the above-described properties on its surface.

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

A solder wire to which the present invention is applied will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a solder wire 1 to which the present invention is applied. A 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, for example, "4. Alloy system", "type" and "symbol" described in JIS Z 3282: 2017, solder alloys described in Table 1, etc. Any solder alloy can be used, such as lead-containing solder alloys and lead-free solder alloys shown in Table 2. In addition to tin, chemical components such as Sb, Bi, Cu, Au, In, Ag, Al, Cd, Fe, Ni, and Zn are added to this solder alloy at respective contents. In addition, the solder alloy is 4. described in JIS Z 3282:2017. The alloy system, type, and symbols are not limited to the chemical composition ranges shown in Tables 1 and 2, but may be composed of any other known chemical composition range.

The flux that constitutes the flux layer 3 is applied to the surface of the solder portion 2, and is composed of, for example, rosin as a main component, and contains a resin, an activator, a solvent, and the like, and is a solid having both flexibility and adhesiveness.

The resin layer 4 is laminated on the surface of the flux layer 3, and is made of, for example, an acrylic resin, but is not limited to this, and may be made of any resin material. The 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 a (meth)acryl represented by the following general formula (2) as an essential component. 5% by mass or more and 50% by mass or less of a structural unit derived from an acid ester, and 5% by mass or more and 80% by mass or less of a structural unit derived from a (meth)acrylic acid ester represented by the 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 the flux during soldering, and after coating the resin layer 4, the surface of the solder wire 1 exhibits stickiness. It is assumed that it does not.

Copolymerization of fluorine-based monomers and silicon-based monomers in the resin layer 4 is conceivable as a non-sticky surface coating. Fluorine is dangerous and unsuitable because it may generate hydrofluoric acid when it is heated by a soldering iron. Silicon is not suitable because siloxane may scatter due to heat and cause contact failure of electronic parts.

A fluorine-free acrylic polymer or silicon-free acrylic polymer is coated by any method. As a coating method, it is easy to coat with a solution of an acrylic polymer dissolved in a solvent. Among them, 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.)

Examples of solder wires to which the present invention is applied will be described below. In addition, the present invention is not limited to the following examples.

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

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

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

The temperature in the round-bottomed flask gradually increased, and due to the heat of reaction, it reached the maximum temperature (88°C) about 1 hour after the hot water was added, and then slowly decreased to 83°C and remained constant. . Nitrogen was continuously supplied while the temperature of the water bath was kept constant for 6 hours after the hot water was added.

After 6 hours from the addition of hot water, the inside of the round-bottom flask turned into a viscous liquid, so the supply of nitrogen was stopped, and 100 g of butyl acetate was gradually diluted using a dropping funnel from the opening of the nitrogen pipe. .

Next, the liquid in the round-bottomed flask was extracted and used as a stock solution. 0.2 to 0.5 g of the undiluted solution was weighed into an aluminum cup with a precision balance and dried in a drying oven at 150° C. for 40 minutes to remove the solvent component to obtain an acrylic polymer. When the solid content of the acrylic polymer undiluted solution was measured based on the weight after drying, it was 36.1% (reaction rate: 97.4%).

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

<Preparation of solder wire>
A flux having the formulation shown in Table 1 below was applied to the solder part composed of Sn: 96.5% by mass, Ag: 3% by mass, and Cu: 0.5% by mass by immersing it in a flux liquid. let me After that, a resin layer made of an acrylic polymer was laminated by a method of immersing the solder portion coated with the flux in an acrylic polymer solution and drying it. Table 2 shows the mass% of the short chain corresponding to the structural unit derived from the methacrylic acid ester represented by the general formula (1) in the resin layer, and the (meth) derived from the (meth) acrylic acid ester represented by the general formula (2) are classified into long-chain mass % corresponding to structural units and cyclic mass % corresponding to structural units derived from the (meth)acrylic acid ester represented by 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）。

Note that the notations of the components of the monomers shown in Table 2 are 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 (18 carbon atoms), M-90G: methoxypolyethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical).

Next, each solder wire prepared 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, the surface of the flux residue on the specimen is liberally sprinkled with powdered talc. The rule is to lightly brush twice in the same direction the surface on which powdered talc has been sprinkled with a soft-bristle brush, and to visually inspect the degree. Since it is suitable for the evaluation method of the solder wire surface of the present invention, confirmation of the adhesiveness of the solder wire surface of the present invention was carried out according to this rule.

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

The evaluation method was that if the powdered talc could be easily removed by brushing, the flux was considered non-tacky and was considered a pass. If the powdered talc could not be removed by brushing, the flux was considered tacky and was rejected.

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 regarded as passing.

In Examples 1 to 7 of the present invention, the components of the resin layer are all within the range specified in the present invention. Therefore, both stickiness and wettability were good. In particular, Example 5 of the present invention is an example in which a resin layer is composed of only cyclic and long chains without short chains.

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

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

Claims (2)

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 an acrylic resin
A solder wire characterized by: The resin layer contains 67% by mass or less of structural units 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 a structural unit derived from an ester, and 5% by mass or more and 80% by mass or less of a structural unit derived from a (meth)acrylic acid ester represented by the general formula (3) as an essential component, The solder wire according to claim 1 , comprising:

(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.)

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

Images