JP2000080460A - Soldered wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain soldered wire in which a thermal creep phenomenon is hard to be generated even in a high temp. environment, excellent in heat resisting strength, also free from the generation of whiskers and contg. no harmful lead by providing the outer circumference of a metallic elemental wire with a soldering layer having a compsn. in which specified amounts of silver and copper are incorporated into tin. SOLUTION: Tin-silver-copper alloy soldered wire 1 is composed of metallic elemental wire 2 such as copper wire, copper alloy wire or the like and a hot dip soldering layer 3 composed of, by weight, 0.5 to 10.0% silver, 0.01 to 2.0% copper, and the balance tin formed on the outer circumference. In the case the soldered wire 1 is joined to a through hole 15 in a printed circuit board 14 by a brazing filler metal 5, the soldered wire 1 is soldered with a copper- applied layer 16 in the substrate 14. In the case, e.g. tin-lead alloy solder is used as the brazing filler metal 5, the plating layer 3 starts to melt, silver and tin therein respectively disperse and elute into the brazing filler metal 5 in the joined part A, and on the joined part A, a layer 4 increased in the contents of silver and tin and reduced in the content of lead deteriorating its heat resisting strength is thickly formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder-plated wire, and more particularly to a lead-free solder-plated wire having improved heat resistance of a solder joint.

[0002]

2. Description of the Related Art Conventionally, a solder-plated wire provided with a tin-lead alloy solder plating layer on the outer periphery of a metal wire has been used for electrical equipment and electronic devices because of its excellent workability of solder plating and solder connection. Generally used widely for equipment members. However, recently, with the miniaturization and high performance of electric and electronic equipment, the inside of the equipment often becomes high temperature environment,
From the viewpoint of improving the reliability of equipment in a high-temperature environment, it is required to improve the heat resistance of the solder connection part, and a solder plated wire having an excellent heat resistance is also required. In addition, with the rapid increase in the production of electrical and electronic equipment, the quantity of electrical and electronic equipment that is disposed of as industrial waste has increased, and the problem of environmental pollution due to the loss of harmful substances from these disposed equipment has been increasing. It has been pointed out that solder plated wires that do not contain harmful substances have been required.

[0003]

As described above, tin-lead alloy solder-plated wires have many advantages in use, such as excellent plating workability and solder connection workability, as described above. As a problem, the solder joints are inferior in reliability in terms of heat resistance, especially when used in a high temperature environment, and tend to cause a thermal creep phenomenon at a solder joint between a tin-lead alloy solder plated wire and another member, There was a major drawback in that the solder plated wire fell off the solder connection.
Further, as an environmental problem, lead elutes from the tin-lead alloy solder plating wire disposed as industrial waste into groundwater due to acid rain and the like, polluting the environment, and furthermore, it is ingested into the human body. The danger came to be pointed out. When lead is taken into the body, it causes toxic symptoms such as anemia, abdominal colic, acute encephalopathy, peripheral neuropathy, and kidney damage. Therefore, there is an urgent need to develop a solder plated wire that does not contain lead harmful to the human body.

[0004] As a plating wire containing no harmful lead, there is a tin plating wire obtained by plating tin metal alone, and it is widely used because of its relatively high heat resistance. However, tin-plated wires have the property that tin-bearing single crystals and whiskers are generated from the tin-plated layer after plating.
This whisker tended to grow longer as it was placed in a high-temperature atmosphere and as the plating thickness increased. Therefore, when the tin-plated wire is used in an electronic device having a high-temperature atmosphere, there is a risk of causing a short circuit accident due to generation of whiskers, and there is a problem in using the tin-plated wire in an electronic device having a high-temperature atmosphere.

Accordingly, an object of the present invention is to provide a solder-plated wire which does not easily generate a thermal creep phenomenon even in a high temperature environment, has excellent heat resistance, does not generate whiskers, and does not contain harmful lead. .

[0006]

In order to achieve the above-mentioned object, the solder plating wire of the present invention has a silver content of 0.5 to 10.0.
The present invention is characterized in that a solder plating layer having a composition consisting of 0.01% to 2.0% by weight of copper, 0.01% to 2.0% by weight of copper, and the balance of tin and inevitable impurities is provided on the outer periphery of the metal wire.

[0007]

The function and effect of the tin-silver-copper alloy plating layer of the solder plated wire of the present invention will be described with reference to FIG. FIG. 3 (a)
Is a cross-sectional explanatory view showing a state in which the solder plating wire 1 of the present invention is joined to the through hole 15 of the printed board 14 with the brazing material 5, and the tin-silver-copper alloy solder plated wire 1 inserted into the through hole 15 is a printed board. The copper clad layer 16 and the brazing material 5 are soldered. FIG. 3B is an enlarged cross-sectional view of a joint A between the tin-silver-copper alloy plating layer 3 of the solder plating wire 1 and the brazing material 5. For example, an example in which a tin-lead alloy solder is used for the brazing material 5 will be described with reference to FIG. During the brazing process, the tin-silver-copper alloy plating layer 3 of the solder plating wire 1 begins to melt, and the silver in the plating layer 3 diffuses into the brazing material 5 at the joining portion A and the tin in the plating layer 3 joins the joining portion. A is eluted into the brazing material 5 of A, and a layer 4 in which the content of silver and tin for increasing the heat resistance is increased and the content of lead for decreasing the heat resistance is reduced is formed at the joint A. As a result, in the joint A between the tin-silver-copper alloy solder-plated wire 1 and the brazing material 5, a layer rich in silver and tin components having improved heat resistance is formed thickly, and heat creep resistance is also improved. Furthermore, if a tin-silver-copper alloy brazing material having the same composition as the plating layer 3 of the solder-plated wire 1 of the present invention is used as the brazing material 5, a layer containing no lead component that reduces heat resistance is formed at the joint A. Thus, the heat resistance of the joint A between the tin-silver-copper alloy solder plated wire 1 and the brazing material 5 is further increased, and the creep characteristics are further improved.

Next, in the tin-silver-copper alloy solder plating wire 1 of the invention, the reason why the silver content of the alloy solder plating layer 3 is limited to 0.5% to 10.0% is that the silver content If it is less than 0.5%, the effect of improving the heat-resistant creep characteristics is not seen, and the melting point of the alloy solder does not decrease so much and the hot-dipability is poor. When the silver content is more than 10.0%, the heat-resistant creep property is improved, but the melting point of the alloy solder becomes too high and the hot-dipability is deteriorated.
This is because there is a disadvantage that the material cost of the plated wire 1 increases. The reason why the copper component is added to the present alloy solder plating layer 3 is to improve the plating appearance characteristics such as the gloss and surface smoothness of the alloy solder plating wire 1 and to reduce the melting temperature of the alloy solder and perform the hot dip plating operation. This is to make it easier. The reason for limiting the copper content to 0.01% to 2.0% is that if the copper content is less than 0.01%, the effect of improving plating appearance characteristics is small, and the melting temperature of the alloy solder does not decrease. When the copper content exceeds 2.0%, a copper-tin alloy precipitates in the hot-dip plating bath, and this is
This is because they adhere to the surface of the metal and cause deterioration of plating appearance.

Further, in the solder plated wire 1 of the present invention, since the plating layer 3 is formed of a tin-silver-copper alloy, whiskers as seen in a tin-only plated wire are completely eliminated.

[0010] Further, since the solder plating wire 1 of the present invention does not contain lead in the plating layer 3, there is no harmful effect on health and environment.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
Note that the present invention is not limited by this. FIG. 1 is a sectional view of a solder plating wire 1 of the present invention. The solder plating wire 1 is a metal wire 2 such as a copper wire or a copper alloy wire.
And the silver formed on the outer periphery of the metal strand 2 is 0.5 to 10.0.
% By weight, 0.01 to 2.0% by weight of copper, and the balance being a molten solder plating layer 3 having a composition of tin and unavoidable impurities.

Next, an embodiment of manufacturing the solder plated wire 1 of the present invention will be described with reference to the manufacturing process diagram of FIG. The molten solder plating bath 6 includes a plating solution portion containing the molten solder plating solution 7, an inlet 11 for the metal element wire 2 provided above the liquid surface of the molten solder plating solution 7, and an inert gas inlet 10.
An outlet 12 for the solder plating wire 1 provided vertically above the molten solder plating solution 7;
Is entirely covered with an inert gas 8 atmosphere layer. Hot-dip plating bath 6 with such a configuration
Inside, a molten solder plating solution 7 having a composition of 3.5% silver, 0.5% copper, and the balance of tin is maintained at a liquid temperature of 250 ° C. A gas is introduced, and the entire upper surface of the molten solder plating solution 7 is covered with a nitrogen gas atmosphere layer. Next, a soft copper wire 2 having an outer diameter of 0.5 mm
Is introduced into the molten solder plating solution 7 from the copper wire inlet 11, the running direction is changed by the pulley 13 in the molten solder plating solution 7, and the molten solder plating solution 7 is drawn vertically upward from the liquid surface of the molten solder plating solution 7. The solder-plated wire 1 was drawn out from the wire outlet 12 and cooled in the air to obtain a solder-plated wire 1 having a plating thickness of 10 μm and a finished outer diameter of 0.52 mm. In this molten solder plating bath 6, the solder plating wire 1 is connected to the molten solder plating solution 7.
By vertically pulling out from above, it is possible to adjust to a desired plating thickness only by controlling the plating linear velocity without using a finished die.

In the above embodiment, a soft copper wire having a circular cross section is used for the metal wire 2, but the shape of the metal wire 2 may be a soft copper wire having a rectangular cross section or a square cross section depending on the application. Even if the material of the metal element wire 2 is a copper alloy, it is a matter of course that the present invention does not depart from the present invention.

The results of an evaluation test of heat-resistant creep characteristics and a whisker generation test performed on the solder-plated wire 1 of the present invention manufactured as described above are described below.

-Heat-resistant creep property test- As an example of the present invention, a solder-plated copper wire 1 having a plating thickness of 10 µm and a finished outer diameter of 10.52 mm manufactured by the above embodiment was used. In addition, as a conventional sample, a finished outer diameter of 0.1 mm was formed by hot-dip plating a 37% lead-63% tin alloy on a soft copper wire having an outer diameter of 0.5 mm to a plating thickness of 10 μm.
A 52 mm tin-lead alloy solder plated copper wire was used. Five samples were prepared for each of the example sample and the conventional example sample. The test method is as shown in FIG.
The sample W was passed through the through hole 15 having a hole diameter of 1 mm and
After soldering each sample W to the printed circuit board 14 with a 7% -63% tin alloy brazing material 17, the sample W is placed in a thermostat at a temperature of 130 ° C. with a load of 1 kg suspended from the end of the sample W. Then, the elapsed time from when the sample W was put in the thermostat to when the sample W dropped out from the through hole 15 of the printed circuit board 14 was measured. The elapsed time was used to evaluate the heat-resistant creep characteristics. Table 1 shows the test results. In addition, the measurement time of Table 1 is an average value of five samples. As is apparent from these results, the tin-silver-copper alloy solder-plated wire 1 of the present invention has excellent heat-resistant creep characteristics and improved heat-resistant strength of the solder joint.

[0016]

-Whisker generation test-As a sample of the present invention, a solder-plated copper wire 1 having a plating thickness of 10 µm and a finished outer diameter of 0.52 mm having the same structure as that used in the above-mentioned heat creep property test was used. As a comparative sample, a tin-plated copper wire having a finished outer diameter of 0.52 mm obtained by hot-dipning tin on a copper wire having an outer diameter of 0.5 mm to a plating thickness of 10 μm was used. Five samples were prepared for each of the example sample and the comparative example sample. In the whisker generation test, each sample was placed in a thermostat at a temperature of 50 ° C., and the time from when the sample was placed in the thermostat to when whiskers were generated in each sample was measured. The occurrence of whiskers was confirmed using a scanning electron microscope at a magnification of 2
Observed at 000x. Table 2 shows the test results. In addition,
The measurement time in Table 2 is an average value of five samples.

[0018] As is clear from the results in Table 2, it was confirmed that the tin-silver-copper alloy solder-plated wire 1 of the present invention did not show any whiskers which could cause a short circuit accident.

[0019]

The tin-silver-copper alloy solder-plated wire of the present invention has the following effects when used as a connection wire for electronic equipment and the like. (1) The heat resistance of the soldered part is improved, and the thermal creep phenomenon does not easily occur even when the soldered part is placed in a high-temperature atmosphere. Reliability is improved. (2) Since there is no whisker, there is no danger of a short circuit accident caused by the whisker. (3) Since it does not contain lead components that are harmful to the human body, health and environmental safety are ensured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a solder plating wire of the present invention.

FIG. 2 is an explanatory view showing one embodiment of a manufacturing process of the solder plated wire of the present invention.

FIG. 3 is an explanatory view showing a state where a solder plating wire of the present invention is soldered to a printed circuit board. FIG. 3A is a cross-sectional explanatory view showing a joined state, and FIG. 3B is a partially enlarged cross-sectional explanatory view of a joined portion.

FIG. 4 is an explanatory view showing a test method of a heat resistance creep property test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tin-silver-copper alloy solder plating wire 2 Metal wire 3 Tin-silver-copper alloy plating layer 4 Tin and silver diffusion layer 5 Brazing material 6 Solder plating bath 7 Solder plating solution 8 Inert gas 9 Inert gas atmosphere layer DESCRIPTION OF SYMBOLS 10 Inert gas conduit 11 Metal wire inlet 12 Solder plating wire outlet 13 Pulley 14 Printed circuit board 15 Through hole 16 Copper clad layer

Claims (1)

[Claims] (1) 0.5 to 10.0% by weight of silver and 0.1% by weight of copper.
A solder-plated wire characterized in that a solder-plated layer comprising from 0.01 to 2.0% by weight, the balance consisting of tin and unavoidable impurities, is provided on the outer periphery of the metal strand.