JP4318449B2 - Lead-free solder alloy - Google Patents

Description

【００２４】
表１の説明
酸化物発生量：はんだ槽の中ではんだを440℃の温度で溶融状態にしておく。次に、３０秒毎にはんだ表面に形成された酸化被膜を7回掻き取りその重量の合計を測定する。
【００２５】
実験結果からも明らかなように、本発明の鉛フリーはんだ合金は、従来のP、Ge、Gaを単独に添加したSn-Cu系鉛フリーはんだ合金よりも４００℃近傍での酸化物の発生量が少なく酸化が抑制されていることが分かる。
【００２６】
【発明の効果】
以上説明したように、本発明の鉛フリーはんだ合金は酸化が容易に進行するSn主成分であるにもかかわらず、酸化の進行が抑制され、メッキ表面への酸化屑のの付着を防ぎ、さらに廃棄処分される酸化屑を減少できるばかりでなく、生産コストを抑制できるという従来のSn-Cu系鉛フリーはんだ合金にない優れた効果を奏するものである。[0001]
[Technical field to which the invention belongs]
The present invention relates to a lead-free solder alloy, particularly a Sn-based lead-free solder alloy suitable for soldering or pre-plating the end of a coil.
[0002]
[Prior art]
Electronic devices use coil parts with copper wires wound around the lead like transformers, and motors such as computer disk drives and cooling fans also use coiled parts. Since these coils are conductive, their ends are soldered to the terminals of electronic devices and motors.
[0003]
In general, the copper wire of the coil component is coated with enamel on the surface and further coated with polyurethane resin. Therefore, the coil ends and the terminals cannot be soldered as they are. Therefore, when soldering, enamel and polyurethane resin (hereinafter referred to as a coating material) at the coil end must be removed. The removal of the covering material may be mechanically peeled off with a blade, but the mechanical removal takes time and is inferior in productivity. Therefore, the method of removing the coating material at the coil end is performed by melting the coating material with heat. The method of removing the coating material with heat is to dissolve the coating material with the heat of the molten solder and remove it by immersing the end of the coil in the molten solder.
[0004]
By the way, when the coil end is soldered to the terminal, the coil end is preliminarily plated in order to obtain a good soldered portion. In general, pre-plating of the coil end is performed by immersing the coil end in the molten solder. However, since the coil end is immersed in the molten solder even when the above-described coating material is removed, the coil end to the molten solder is removed. The immersion of the part enables a rational operation of performing preliminary plating simultaneously with the removal of the covering material.
[0005]
For removing the coil end covering material and pre-plating, a flux is applied to the coil end, and then the end is immersed in molten solder. Then, the coating material is melted by the heat of the molten solder, and the flux applied to the coil end part floats around the immersed coil end part. Accordingly, the coating material is removed, and the flux acts where the copper wire is exposed, so that the molten solder is metallically joined to the copper wire.
[0006]
Previously, Pb-Sn solder was used as a pre-plating for coil ends. However, Pb-Sn solder has been restricted due to Pb pollution, so recently it does not contain Pb. Lead-free solder has been used. When soldering coil ends, the temperature of the molten solder must be around 400 ° C in order to dissolve and remove the coating material. When the temperature of the molten solder is increased in the lead-free solder, oxidation of the molten solder proceeds and a large amount of oxide is generated. The generation of a large amount of the oxide is not economically preferable because the amount attached to the soldering portion is increased to deteriorate the appearance characteristics of the product and expensive lead-free solder is oxidized and discarded.
[0007]
It has been reported that the addition of P and Ge is effective in the vicinity of 250 ° C. as an oxide suppression measure for lead-free alloys (see, for example, Reference 1). There are also Sn-Cu-based lead-free solder alloys that contain Ge as an oxide suppression measure (for example, Reference 2) and those that contain Ga (for example, Reference 3).
[0008]
[Patent Document 1]
JP 11-77366 A (Page 2 0009)
[Patent Document 2]
JP 11-77367 A (page 3 0023)
[Patent Document 3]
JP 10-291087 A (Page 3 0006)
[0009]
[Problems to be solved by the invention]
By the way, the cause of the progress of oxidation on the surface of the molten solder is considered to be that the main component of the oxide formed on the solder surface is Sn, which is easily oxidized by oxygen in the atmosphere and proceeds. It is done. In the conventional oxidation-suppressed lead-free solder to which P, Ge, and Ga are added alone, oxidation is suppressed at around 250 ° C., but the effect of suppressing oxidation cannot be obtained at around 400 ° C. It is an object of the present invention to provide a lead-free solder alloy that exhibits an oxidation inhibiting effect near 400 ° C.
[0010]
[Means for Solving the Problems]
The inventor has an effect of suppressing oxidation by adding P, Ge, Ga alone in the vicinity of 250 ° C. with respect to the Sn main component, but when adding P and / or Ge to those added with Ga, As a result of the synergistic action with Ga, it was found that there was an oxidation resistance suppressing effect even at around 400 ° C., and the present invention was completed.
[0011]
In claim 1, the main component is Sn, Cu is 3 to 8% by mass, Ga is 0.005 to 0.1% by mass, and at least one of P and Ge is added in an amount of 0.001 to 0.2% by mass. A lead-free solder alloy having a liquidus temperature of 420 ° C. or lower.
[0012]
The lead-free solder alloy according to claim 1, wherein a copper erosion suppressing element is added.
[0013]
The lead-free solder alloy according to claim 2, wherein at least one of Co and Ni is added in an amount of 0.01 to 3% by mass as the copper erosion suppressing element.
[0014]
A fourth aspect of the present invention is the lead-free solder alloy according to any one of the first to third aspects, to which a wettability improving element is added.
[0015]
A lead-free solder alloy according to claim 4, wherein 0.005 to 2% by mass of Ag is added as the wettability improving element.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
When removing the enamel or polyurethane resin coating material that is the coil coating material, it must be heated to around 400 ° C. The temperature at which the article is immersed in the molten solder for soldering is generally at a liquidus temperature of +20 to 50 ° C., although it depends on the heat capacity of the component. However, when the soldering temperature is 470 ° C. or higher, the coating material instantly carbonizes and adheres to the coil end when the coil end is immersed in the molten solder, which hinders the metallic bonding of the solder. Therefore, the solder alloy used for the pre-plating of the coil end is preferably a solder alloy having a solder liquidus temperature of 420 ° C. or lower so that the soldering temperature is 470 ° C. or lower. In addition, when the soldering temperature is 470 ° C. or higher, copper erosion becomes severe.
[0017]
In the lead-free solder alloy of the present invention, if the Cu content that prevents copper erosion is less than 3% by mass, the effect of preventing copper erosion does not appear. However, if more than 8% by mass of Cu is added, the liquidus The temperature becomes 420 ° C. or higher, and the copper erosion becomes intense and the solderability is deteriorated.
[0018]
The lead-free solder alloy of the present invention has improved oxidation resistance compared to conventional Sn-Cu solder alloys by adding Ga and Sn and Cu to Sn-Cu alloys. When Ga is added in an amount of less than 0.005% by mass, the effect of suppressing oxidation does not appear. On the other hand, if Ga is added in an amount of more than 0.1% by mass, solderability is inhibited.
[0019]
When one or more of P and Ge are added simultaneously to a Sn—Cu alloy containing Ga, an oxidation inhibition effect at high temperatures appears. The addition amount of P and Ge here is independent or simultaneous addition, if the addition amount is less than 0.001% by mass, the effect of suppressing oxidation at high temperature does not appear, and if added over 0.2% by mass, it is the same as Ga Inhibits solderability [0020]
Since Sn-Cu-based alloys are severely eroded by copper in the vicinity of 400 ° C., it is possible to add one or more kinds of Co and Ni having an effect of preventing copper erosion. When Ni and Co are added in amounts less than 0.01% by mass, the effect does not appear. However, when the added amounts of Ni and Co exceed 3% by mass, the liquidus temperature is the object of the present invention. It will exceed 420 ℃.
[0021]
When the coil end is immersed in the molten solder, the molten solder must be sufficiently wetted up to the immersed part of the coil end. In some cases, the portion immersed in the molten solder may not be wetted or unsolder may occur. In such a case, a wettability improving element may be added. Ag is a wettability improving element. If the amount of Ag added is less than 0.05% by mass, the effect of improving wettability will not appear. However, if more than 2% by mass is added, not only the effect can be expected, but the addition of a large amount of expensive Ag is economical. This is not preferable.
[0022]
【Example】
Examples and comparative examples of the present invention are shown in Table 1.
[0023]
[Table 1]

[0024]
Description of Table 1 Oxide generation amount: Solder is melted at a temperature of 440 ° C. in a solder bath. Next, the oxide film formed on the solder surface is scraped 7 times every 30 seconds and the total weight is measured.
[0025]
As is clear from the experimental results, the lead-free solder alloy of the present invention generates more oxide at around 400 ° C than the conventional Sn-Cu-based lead-free solder alloy to which P, Ge, and Ga are added alone. It can be seen that there is little oxidation and oxidation is suppressed.
[0026]
【The invention's effect】
As explained above, despite the fact that the lead-free solder alloy of the present invention is a Sn main component that easily oxidizes, the progress of the oxidation is suppressed, preventing the deposition of oxide debris on the plating surface, This not only reduces the amount of oxide waste that is discarded, but also has an excellent effect not found in conventional Sn-Cu-based lead-free solder alloys that can reduce production costs.

Claims (2)

In a solder alloy for pre-plating the end of a copper wire, Cu is 3 to 8% by mass, Ni is 0.01 to 3% by mass, Co is 0.01 to 3% by mass, Ga is 0.005 to 0.1% by mass, and P or Ge A solder alloy for pre-plating, characterized in that at least one of these is 0.001 to 0.2% by mass and the balance is Sn. The solder alloy for pre-plating according to claim 1, wherein 0.005 to 2 mass% of Ag is further added to the solder alloy for pre-plating.