Lead-Free Solder Alloy for Terminal Preliminary Plating, and Electronic Component

Abstract

Provided is a lead-free solder alloy for terminal preliminary plating, by which the separation property when pulling up the terminals from molten solder is improved. The lead-free solder alloy for terminal preliminary plating contains 4 mass % or more and 6 mass % or less of Cu, 0.1 mass % or more and 0.2 mass % or less of Ni, 0.01 mass % or more and 0.04 mass % or less of Ga, 0.004 mass % or more and 0.03 mass % or less of P, and a remainder of Sn, a total amount of Ga and P being 0.05 mass % or less. Its tension in a melted condition by heating in soldering temperature is 200 dyn/cm or less.

Claims

1. A lead-free solder alloy for terminal preliminary plating, by which preliminary plating is performed on a terminal by dipping, the alloy comprising: 4 mass % or more and 6 mass % or less of Cu; more than 0.1 mass % and 0.2 mass % or less of Ni; 01 mass % or more and 0.04 mass % or less of Ga; 004 mass % or more and 0.03 mass % or less of P; and a remainder of Sn, a total amount of Ga and P being 0.05 mass % or less, wherein surface tension of the lead-free solder alloy when pulling up a platinum ring having circumference of 4 cm from the lead-free solder alloy which is in a melted condition by heating 400 degrees C. is 200 dyn/cm or less.

2. The lead-free solder alloy for terminal preliminary plating according to claim 1, wherein the alloy is used for the terminal preliminary plating in which the temperature at the terminal preliminary plating time is 380 degrees C. or more.

3. An electronic component in which preliminary plating is performed on a terminal post using the lead-free solder alloy for terminal preliminary plating according to claim 1.

4. An electronic component in which preliminary plating is performed on a terminal post using the lead-free solder alloy for terminal preliminary plating according to claim 2.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a diagram illustrating one configuration example of an electronic component according to the embodiment.

PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION

[0024] When adding predetermined amounts of Ga and P into a solder alloy having a principle ingredient of Sn, melt viscosity of a surface of the solder is reduced, so that tension of the solder is also reduced when pulling up an object to be soldered, for example, the terminals of the coil from the molten solder. This allows the separation property of the solder to be improved when pulling up the terminals thereof from the molten solder, thereby enabling the generation of the bridge and/or the solder icicle to be inhibited.

[0025] When adding small amounts of Ga and P, tension of the solder remains high when pulling up the terminals thereof from the molten solder. This fails to get sufficient effect of improving the separation property. As described above, when removing the enamel or the polyurethane resin as the coating materials of the coil by dipping the terminals of the coil into the molten solder, it is required to heat the molten solder to temperature of around 400 degrees C. to make the soldering temperature around 400 degrees C.

[0026] The temperature in a case of clipping the object to be soldered into the molten solder and soldering it is generally 20 through 50 degrees C. over the melting point of the solder due to heat capacity of the terminals of an object to be processed or a part such as the coil having the terminals. When, however, the soldering temperature exceeds 470 degrees C., the coated materials are carbonized in a moment in clipping the terminals of the coil into the molten solder, so that they are adhered to the terminals. This prevents the metal joining of the solder. Accordingly, it is preferable that a solder alloy used for the preliminary plating of the terminals is a solder alloy having a melting point of the solder of 420 degrees C. or less so that the soldering temperature thereof is 470 degrees C. or less. Further, when the soldering temperature thereof exceeds 470 degrees C., copper leaching becomes remarkable.

[0027] On the other hand, when additive amounts of Ga and P are increased more than necessary, the melting point of the solder is also increased in height, which is unavailable for soldering at around 400 degrees C.

[0028] When adding only either Ga or P into the solder alloy having a principle ingredient of Sn, it is possible to get oxidation inhibitory effect but it is impossible to obtain a sufficient effect to improve the separation property.

[0029] By taking into consideration an additive amount of Ga in a case of adding both of Ga and P into the solder alloy having a principle ingredient of Sn, it is impossible to obtain a sufficient effect to improve the separation property when the additive amount of Ga is less than 0.01 mass %. On the other hand, when the additive amount of Ga exceeds 0.04 mass %, the melting point of the solder is increased in height, which is unavailable for soldering at around 400 degrees C.

[0030] By taking into consideration an additive amount of P in a case of adding both of Ga and P into the solder alloy having a principle ingredient of Sn, it is impossible to obtain a sufficient effect to improve the separation property when the additive amount of P is less than 0.004 mass %. On the other hand, when the additive amount of P exceeds 0.03 mass %, the melting point of the solder is increased in height, which is unavailable for soldering at around 400 degrees C.

[0031] Provided that when Ga and P are respectively added to almost their upper limit values, the melting point of the solder is also increased in height, which is unavailable for soldering at around 400 degrees C.

[0032] Therefore, within a range where a total additive amount of Ga and P is 0.05 mass % or less, 0.01 mass % or more and 0.04 mass % or less of Ga and 0.004 mass % or more and 0.03 mass % or less of P are added.

[0033] When an additive amount of Cu having copper leaching prevent effect is less than 4 mass % in the solder alloy having a principle ingredient of Sn, the copper leaching prevent effect does not appear. On the other hand, when an additive amount of Cu exceeds 6 mass %, the melting point of the solder is increased in height.

[0034] Additionally, when adding Ni to the above-mentioned solder alloy having a principle ingredient of Sn in which the additive amount of Cu is 4 through 6 mass %, the copper leaching prevent effect thereof is enhanced in the soldering at around 400 degrees C. When, however, the additive amount of Ni is less than 0.1 mass %, the copper leaching prevent effect thereof is not enhanced. On the other hand, when the additive amount of Ni exceeds 0.2 mass %, the melting point of the solder is also increased in height.

[0035] It is known that when adding Ag into the solder alloy having a principle ingredient of Sn, the wettability thereof is improved. The addition of expensive Ag causes product costs to rise, which is not preferable. According to this invention, even when no Ag is added, the separation property of the solder is improved when pulling up the terminals from the molten solder.

EXECUTED EXAMPLES

[0036] Executed examples of this invention and comparison examples will be indicated in Table 1. It is to be noted that an additive amount of each element is indicated in the Table 1 as mass %.

TABLE-US-00001 TABLE 1 EVALUATION OF DRIBBLE PROPERTY AND ICILE-LIKE FORMED SOLDER/BRIDGE NUMBER OF GENERATED TENSION ICILE-LIKE FORMED Sn Cu Ni P Ga P + Ga OF SOLDER SOLDER/BRIDGE RESULT EXECUTED EXAMPLE 1 bal. 5 0.15 0.015 0.02 0.035 127 0 ∘ EXECUTED EXAMPLE 2 bal. 5 0.15 0.03 0.02 0.05 128 0 ∘ EXECUTED EXAMPLE 3 bal. 5 0.15 0.004 0.04 0.044 127 0 ∘ EXECUTED EXAMPLE 4 bal. 5 0.15 0.004 0.02 0.024 135 0 ∘ EXECUTED EXAMPLE 5 bal. 5 0.15 0.015 0.01 0.025 128 0 ∘ EXECUTED EXAMPLE 6 bal. 5 0.15 0.004 0.01 0.014 128 0 ∘ EXECUTED EXAMPLE 7 bal. 6 0.15 0.015 0.02 0.035 130 1 ∘ EXECUTED EXAMPLE 8 bal. 4 0.15 0.015 0.02 0.035 120 0 ∘ EXECUTED EXAMPLE 9 bal. 5 0.2 0.015 0.02 0.035 138 0 ∘ EXECUTED EXAMPLE 10 bal. 5 0.1 0.015 0.02 0.035 118 0 ∘ COMPARISON EXAMPLE 1 bal. 5 0.15 — — 0 400 38 x COMPARISON EXAMPLE 2 bal. 5 0.15 0.015 — 0.015 294 15 x COMPARISON EXAMPLE 3 bal. 5 0.15 — 0.02 0.02 807 17 x COMPARISON EXAMPLE 4 bal. 5 0.15 0.05 0.02 0.07 — — — COMPARISON EXAMPLE 5 bal. 5 0.15 0.015 0.06 0.075 — — — COMPARISON EXAMPLE 6 bal. 5 0.15 0.001 0.02 0.021 805 14 x COMPARISON EXAMPLE 7 bal. 5 0.15 0.015 0.001 0.018 292 14 x COMPARISON EXAMPLE 8 bal. 5 0.15 0.001 0.008 0.009 885 29 x COMPARISON EXAMPLE 9 bal. 5 0.15 0.02 0.04 0.08 — — — COMPARISON EXAMPLE 10 bal. 7 0.15 0.015 0.02 0.035 — — — COMPARISON EXAMPLE 11 bal. 5 0.8 0.015 0.02 0.035 — — —

[0037] In evaluation of separation property of the solder shown in TABLE 1, tension when pulling up a specimen from the molten solder was evaluated. As a method of evaluating the tension, a ring method using a surface tension balance of Du Noüy was adopted. After respective solder materials having compositions shown in the executed examples and the comparison examples were melted at 400 degrees C. using a solder bath, the molten solder surface was scraped and immobile for five minutes. Then, a platinum ring (specimen) having circumference of 4 cm, fat of which had been previously removed by IPA, was clipped thereinto and tension when pulling up it was measured (unit: dyn/cm). Ten measurements were carried out for each solder composition and an average value thereof was calculated as the tension.

[0038] In the evaluation of the solder icicle and the bridge, after respective solder materials having compositions shown in the executed examples and the comparison examples were melted at 400 degrees C., the molten solder surface was scraped. The terminals of the coil to which the flux had been previously applied were clipped thereinto and number of generated solder icicle and bridge was evaluated when pulling up them. The terminals of the coil were four terminals on each side and Cu wire coil having a pitch of 2 mm was used. As the flux, rosin-based post flux (SR-209 made by Senju Metal Industrial Company) was used. A total of 20 coils was used to measure a total number of generated solder icicle and bridge. A clipping condition was set to be a clipping rate of 10 mm/sec, a clipping depth of 4 mm and a pulling-up rate of 10 mm/sec.

[0039] When the tension in the separation property of the solder was 200 dyn/cm or less and the total number of generated solder icicle and bridge was 5 or less, the evaluation result was indicated as 0. When the tension in the separation property of the solder exceeded 200 dyn/cm and the total number of generated solder icicle and bridge exceeded 5, the evaluation result was indicated as X.

[0040] As shown in each executed example shown in the Table 1, into a solder alloy having a principle ingredient of Sn and containing 4 mass % or more and 6 mass % or less of Cu and 0.1 mass % or more and 0.2 mass % or less of Ni, by adding 0.01 mass % or more and 0.04 mass % or less of Ga and 0.004 mass % or more and 0.03 mass % or less of P within a range in which a total amount of Ga and P is 0.05 mass % or less, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is improved, thereby inhibiting the solder icicle and the bridge from generating.

[0041] For example, in the executed example 1 in which 0.02 mass % of Ga that is the lower limit value or more and the upper limit value or less and 0.015 mass % of P that is the lower limit value or more and the upper limit value or less are added within a range in which a total amount of Ga and P is 0.05 mass % or less, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is improved, thereby inhibiting the solder icicle and the bridge from generating.

[0042] Further, even in the executed example 2 in which 0.03 mass % of P that is the upper limit value is added and 0.02 mass % of Ga is added to be included within a range in which a total amount of Ga and P is 0.05 mass % or less and even in the executed example 3 in which 0.04 mass % of Ga that is the upper limit value is added and 0.004 mass % of P is added to be included within a range in which a total amount of Ga and P is 0.05 mass % or less, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is improved, thereby inhibiting the solder icicle and the bridge from generating.

[0043] Additionally, in the executed example 4 in which 0.004 mass % of P that is the lower limit value is added, when adding about 0.02 mass % of Ga that is less than the upper limit value, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is improved, thereby inhibiting the solder icicle and the bridge from generating.

[0044] In the executed example 5 in which 0.01 mass % of Ga that is the lower limit value is added, when adding about 0.015 mass % of P that is less than the upper limit value, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is improved, thereby inhibiting the solder icicle and the bridge from generating.

[0045] In the executed example 6 in which 0.004 mass % of P that is the lower limit value is added and 0.01 mass % of Ga that is the lower limit value is added, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is improved, thereby inhibiting the solder icicle and the bridge from generating.

[0046] In the executed example 7 in which the same values of Ga and P as those of the executed example 1 are added and Cu of the upper limit value is added and in the executed example 8 in which Cu of the lower limit value is added, it has been found that this does not exert any influence upon the separation property by the addition of Ga and P.

[0047] In the executed example 9 in which the same values of Ga and P as those of the executed example 1 are added and Ni of the upper limit value is added and in the executed example 10 in which Cu of the lower limit value is added, it has been found that this does not exert any influence upon the separation property by the addition of Ga and P.

[0048] On the other hand, in the comparison example 1 in which a solder alloy has a principle ingredient of Sn and contains 4 mass % or more and 6 mass % or less of Cu and 0.1 mass % or more and 0.2 mass % or less of Ni but does not contain Ga and P, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is poor, so that a generation of the solder icicle and the bridge cannot be inhibited.

[0049] In the comparison examples 2 and 3 in which any one of Ga and P is added to a solder alloy having a principle ingredient of Sn, it has been also found that the separation property of the solder when pulling up the terminals from the molten solder is poor, so that a generation of the solder icicle and the bridge cannot be inhibited.

[0050] Further, in the comparison example 4 in which both of Ga and P are added to a solder alloy having a principle ingredient of Sn but P exceeding the upper limit value is added and in the comparison example 5 in which Ga exceeding the upper limit value is added, the melting point exceeds +20 degrees C. from the melting point of the executed example 1, so that the sufficient solderability at around 400 degrees C. could not be obtained. Therefore, the evaluation of the separation property of the solder and the solder icicle and the bridge has not been performed.

[0051] In the comparison example 6 in which both of Ga and P are added to a solder alloy having a principle ingredient of Sn but P less than the lower limit value is added, in the comparison example 7 in which Ga less than the lower limit value is added, and in the comparison example 8 in which Ga and P which are both less than the lower limit value are added, it has been found that the separation property of the solder when pulling up the terminals from the molten solder is poor, so that a generation of the solder icicle and the bridge cannot be inhibited.

[0052] In the comparison example 9 in which both of Ga and P are added to a solder alloy having a principle ingredient of Sn but a total amount of Ga and P exceeding the upper limit value is added, the melting point exceeds +20 degrees C. from the melting point of the executed example 1, so that the sufficient solderability at around 400 degrees C. could not be obtained. Therefore, the evaluation of the separation property of the solder and the solder icicle and the bridge has not been performed.

[0053] In the comparison example 10 in which the same values of Ga and P as those of the executed example 1 are added and Cu exceeding the upper limit value is added and in the comparison example 11 in which Ni exceeding the upper limit value is added, the melting point exceeded +20 degrees C. from the melting point of the executed example 1, so that the sufficient solderability at around 400 degrees C. could not be obtained. Therefore, the evaluation of the separation property of the solder and the solder icicle and the bridge has not been performed.

[0054] From the above results, as shown in FIG. 1, in an electronic component 12, the terminals 10 of which are preliminarily plated with the solder 11 by dipping the terminals 10 into the molten solder at around 400 degrees C. and pulling up them using the lead-free solder alloy for terminal preliminary plating according to this invention, it is possible to melt the coating materials by heat of the molten solder to remove them, and it has been found that the separation property of the solder when the soldering is carried out at around 400 degrees C. is improved, thereby inhibiting the solder icicle and the bridge from generating.

[0055] In addition, the temperature of around 400 degrees C. at the soldering is referred to as a range of temperature between 380 degrees C. and 470 degrees C. This is because the temperature of the molten solder must be 380 degrees C. or more in order to remove the coating materials but the soldering must be carried out with the temperature of the molten solder being 470 degrees C. or less to prevent the coating materials from being carbonized. Further, the solder alloy having a melting point of 420 degrees C. or less is preferable so that the soldering temperature thereof is 470 degrees C. or less.

DESCRIPTION OF CODES

[0056] 10 . . . Terminals; 11 . . . Solder; and 12 . . . Electronic Component