JP4401671B2 - High temperature lead-free solder alloys and electronic components - Google Patents

Description

表１におけるＮｏ１〜１５は、固相線温度が２４０℃近辺であるが、２６０℃以上での吸収熱量が５０％以上となっている。また引張試験における破断伸びも０．３％以上であり、十分にはんだとして使用できるものである。一方、比較例は２６０℃以上での吸収熱量が５０％より少なかったり、２６０℃以下で完全に液状化したりする等、２６０℃以上において耐熱性に劣っていた。
次に本実施例のＮｏ．１〜１５の高温鉛フリーはんだ合金を用いて、内部のコイル素子と外部接続端子とを接合したコイル部品を各々１００個作製し、基板に対する実装実験を行った。コイル部品は、外部接続端子と基板とをＳｎ−０．７Ｃｕ鉛フリーはんだを用いて、２６０℃の温度ではんだ付け接合した。基板に実装後、コイル部品の導通を確認したが、いずれも良好な導通を維持し、導通不良を生じることはなかった。すなわち、コイルと外部接続端子との接合が良好な耐熱性を有していることが確認された。
【００２４】
【発明の効果】
以上説明したように、本発明のはんだ合金は、固相線温度が240℃近辺であるにもかかわらず、260℃でほとんど凝固しているため、本発明のはんだ合金で電子部品内部のはんだ付けを行った場合、二度目に行う電子部品のはんだ付け温度が260℃以下であるならば、電子部品内部のはんだ付け部を確実に保持できるという信頼性に優れたはんだ付け部が得られるものである。
【図面の簡単な説明】
【図１】示差走査線熱量分析装置により測定して得られる本発明合金系の曲線モデル（DSC曲線）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-temperature solder alloy containing no lead, particularly to a high-temperature solder alloy suitable for use in soldering inside an electronic component, and an electronic component using the solder alloy.
[0002]
[Prior art]
Some electronic components mounted on a printed circuit board of electronic devices have their insides soldered with a solder alloy. Since a solder alloy is also used when mounting this electronic component on a printed circuit board, the solder alloy inside the electronic component must be a high-temperature solder alloy that has a higher melting point and higher heat resistance than the solder alloy used for mounting. There is. That is, when soldering to a printed circuit board, the high-temperature solder alloy must securely hold the soldered portion inside the electronic component. Here, the high temperature solder alloy refers to an alloy having a solidus temperature of 183 ° C. or higher.
[0003]
Conventional high-temperature solder alloys are Pb-Sn based on Pb, such as Pb-5Sn, Pb-10Sn, etc., and solder alloys for mounting are solder alloys with low melting point near Sn-Pb eutectic (63Sn-Pb) Was used.
[0004]
In recent years, in general, electronic devices such as AV devices and computers have been disposed of without being repaired or upgraded in the case of failure or reduced functionality. In particular, printed circuit boards are made by bonding copper foil to resin, and solder is attached to the copper foil and cannot be separated, so incineration is not possible and disposal is landfill disposal. It was. When acid rain with high acidity comes into contact with the printed circuit board disposed of in landfill, Pb in the solder is eluted and mixed into groundwater. And if humans or livestock drink groundwater containing Pb component, there is a concern that Pb component will accumulate in the body and cause lead poisoning for many years. Therefore, so-called lead-free solder containing no Pb has been required from the electronic equipment industry.
[0005]
At present, lead-free solder alloys are mainly composed of Sn and added with metal elements such as Cu, Ag, Bi, Zn, In, Sb, Sn-0.7Cu (melting point: 227 ° C), In addition to binary alloys such as Sn-3.5Ag (melting point: 221 ° C), Sn-58Bi (melting point: 139 ° C), Sn-9Zn (melting point: 199 ° C), metal elements are added to these depending on the application. And there is something that is more than three yuan.
[0006]
Since lead-free solder alloys are mainly used when soldering electronic components to a printed circuit board, it is desirable that all of them have a melting point close to that of a conventional Sn—Pb eutectic alloy. The composition of lead-free solder close to the melting point of this Sn—Pb eutectic solder is Sn-9Zn alloy, but the lead-free solder alloy has extremely poor wettability during soldering. Furthermore, since Zn is a very oxidizable component, the soldering operation is difficult and practical, especially considering the soldering operation in the atmosphere. The Sn-58Bi alloy has a lower melting point than the Sn-Pb eutectic alloy, but it is brittle because it contains a large amount of Bi, and the melting point is too low to have heat resistance, so there is a problem in the reliability of the joint. Therefore, lead-free solder, which is currently widely used for mounting electronic components, has a slightly higher melting point than Sn-Pb eutectic solder, but Sn-3.5Ag (melting point 221 ° C), Sn-0.7Cu (melting point: 227 ° C) ), Sn-3Ag-0.5Cu (melting point: 217 ° C.) and the like.
[0007]
In addition, high temperature solder alloys are used in electronic components having functional elements such as coils and semiconductors. For example, in a part having a coil using a winding, a conductor wire is wound around a support such as a magnetic material, and the end of the conductor wire is connected to an external connection terminal using a high-temperature solder alloy. The coil component is connected and fixed to the substrate by soldering the external connection terminal and the substrate. Therefore, it is necessary to maintain the bonding against the temperature at which the terminals of the electronic component and the substrate are soldered.
There is also a demand for lead-free soldering for high-temperature solder alloys used inside such electronic components. Conventionally, as a high-temperature lead-free solder alloy, Au-20Sn high-temperature lead-free solder alloy containing 20% by mass of Sn containing Au as a main component, or Sn- containing 25 to 44% by weight of Sb as a main component of Sn. There is Sb high-temperature lead-free solder (Patent Document 1).
A solder material for die bonding is disclosed, in which Sb is 11.0 to 20.0 mass%, P is 0.01 to 0.2 mass%, and the balance is Sn and inevitable impurities. Furthermore, a soldering material for die bonding is disclosed in which Sb is 11.0 to 20.0 mass%, P is 0.01 to 0.2 mass%, at least one of Cu and Ni is 0.005 to 5.0 mass%, and the balance is Sn and inevitable impurities. (Patent Document 2).
[0008]
[Patent Document 1]
JP 11-151591 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-284792
[Problems to be solved by the invention]
By the way, the Au-20Sn high-temperature lead-free solder alloy is composed of expensive Au as a main component, and thus is not economically preferable for use in soldering low-cost electronic components and electronic devices. In addition, the conventional Sn-Sb high-temperature lead-free solder alloy can obtain good heat resistance by adding Sb in a large amount of 10% by mass or more, but because Sb was added in such a large amount, It was so fragile that it could easily be destroyed just by dropping it from a high place. Furthermore, since this Sn-Sb high-temperature lead-free solder alloy has a large gap between the solidus temperature and the liquidus temperature, it takes time for the molten solder to solidify after soldering. When an impact is applied to the soldered portion, cracks or cracks may be generated in the soldered portion. The present invention is a high-temperature lead-free solder that is inexpensive and not only less brittle than conventional Sn-Sb high-temperature lead-free solder alloys, but also relatively narrow between the solidus and liquidus temperatures. The object is to provide an alloy.
[0010]
[Means for Solving the Problems]
The above problems are solved by any one of the following (1) to (9).
(1) A high-temperature lead-free solder alloy comprising 10 to 40% by mass of Sb, 0.5 to 10% by mass of Cu, and the balance Sn.
(2) A high-temperature lead-free solder alloy further containing a mechanical strength improving element in addition to the high-temperature lead-free solder alloy described in (1).
(3) The element contains one or more elements of Ni, Co, Fe, Mo, Cr, and Mn as the mechanical strength improving element in a total amount of 0.5% by mass or less (2) High temperature lead-free solder alloy described in 1.
(4) The high-temperature lead-free solder alloy according to (2) or (3), wherein the mechanical strength improving element contains at least 1% by mass of any one of Ag and Bi.
(5) A high-temperature lead-free solder alloy characterized by further containing an oxidation inhibiting element in the high-temperature lead-free solder alloy according to any one of (1) to (4).
(6) The lead-free solder alloy according to (5), wherein the oxidation-suppressing element contains one or more of P, Ge, and Ga in total of 1% by mass or less.
(7) An electronic component in which a functional element and an external connection terminal are joined by soldering using a high-temperature solder alloy, and the high-temperature solder alloy has Sb of 10 to 40 mass% and Cu of 0.5 to 10 mass %, And an electronic component having a composition consisting of the remaining Sn.
(8) The electronic component according to (7), wherein the high temperature solder alloy contains a mechanical strength improving element and / or an oxidation inhibiting element.
(9) The electronic component according to (7) or (8), wherein the functional element is a coil element.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The Sn-based lead-free solder alloy generally used has a liquidus temperature of 210 to 220 ° C and a soldering temperature of 240 to 260 ° C. Therefore, when these lead-free solder alloys are used for soldering electronic components and printed circuit boards, the solidus temperature is 260 ° C or higher as a high-temperature solder alloy that does not melt at the soldering temperature of the solder alloy. However, with a lead-free solder alloy containing Sn as a main component and a common metal element added thereto, the solidus temperature cannot be made 260 ° C. or higher. However, even if the solidus temperature is 260 ° C. or lower, if the solder in the soldered portion is almost solidified at 260 ° C., the bonded state can be maintained and used. In other words, if the bonding state can be maintained at 260 ° C., it will have heat resistance when soldering electronic components with the following Sn-based lead-free solder alloy.
[0012]
The inventors of the present invention have found that an alloy in which a large amount of Sb is added to Sn has a solidus temperature of around 240, but is almost solidified at 260 ° C., which is the soldering temperature of the lead-free solder alloy for Sn-based mounting. The present invention has been completed by finding out that it is in a state and that the addition of Cu to the Sn-Sb alloy can improve the brittleness of the Sn-Sb alloy and can narrow the gap between the solidus temperature and the liquidus temperature. It was.
[0013]
The high-temperature lead-free alloy of the present invention is a high-temperature lead-free solder alloy characterized by consisting of 10 to 40% by mass of Sb, 0.5 to 10% by mass of Cu, and the balance Sn.
[0014]
In the Sn-Sb high-temperature lead-free solder alloy, if the Sb content is less than 10% by mass, the required heat resistance cannot be obtained, and if it exceeds 40% by mass, the solderability becomes poor.
[0015]
Cu has the effect of improving the brittleness of the Sn—Sb alloy and lowering the liquidus temperature. Cu also has the effect of increasing the heat of absorption of the alloy in the high temperature region in the DSC curve. That is, when Cu is added to the Sn—Sb alloy, more heat is required for melting the solder, and the heat resistance is further improved. If the amount of Cu added to the Sn-Sb alloy is less than 0.5% by mass, the effects of lowering the liquidus temperature, improving brittleness, and improving heat resistance cannot be obtained. If the amount is larger than this, the liquidus temperature becomes 400 ° C. or more, which affects the soldering operation.
[0016]
FIG. 1 is a curve model (DSC curve) of Sn-30Sb-3Cu alloy obtained by a differential thermal scanning calorimeter. The area surrounded by the baseline (dotted line) and the DSC curve is the amount of heat required for the solder to melt completely. In order for the alloy to have good heat resistance, it is necessary that the solid component exceeds the amount of the liquid component or the flow of the liquid component is suppressed. For this reason, when 260 ° C (A) is used as the boundary line, the heat quantity per unit weight at the time of melting of the solder in this thermal analysis is a heat quantity of 260 ° C or higher (right side of A in the figure) of the total heat quantity. If it is an alloy that draws a curve that is at least%, its heat resistance effect is expected. The liquidus temperature must be 400 ° C or less in consideration of workability. In the differential thermal analysis of Sn-30Sb-3Cu in FIG. 1, it can be seen that the heat quantity at 260 ° C. or higher is 80% or more of the total heat quantity, and the heat resistance is sufficiently high at 260 ° C. or higher.
[0017]
The high-temperature lead-free alloy of the present invention can also contain an element for improving mechanical strength. By adding such an element for improving mechanical strength, sufficient reliability can be obtained even when soldering a portion where mechanical strength is required. Such a mechanical strength improving element is preferably one or more of metals such as Ag, Bi, Ni, Co, Fe, Mo, Cr, and Mn. Any of these elements improves the mechanical strength by forming a solid solution in Sn or forming an intermetallic compound. However, if Ni, Co, Fe, Mo, Cr, and Mn are added in large amounts, the fluidity of the solder is hindered. For this reason, it is preferable that the total amount of Ni, Co, Fe, Mo, Cr, and Mn is 0.5% by mass or less of the total amount of solder. When Ag and Bi are added in large amounts, the solidus line is lowered. As for Ag and Bi, the total amount is preferably 1% by mass or less of the total amount of solder.
[0018]
And the high temperature lead-free solder alloy of this invention can also contain an oxidation inhibitory element. By adding an oxidation inhibiting element, the oxidation of the solder alloy can be suppressed during the manufacture of the electronic component. In particular, a solder alloy having a liquidus temperature of 350 ° C. or higher may be oxidized during the soldering operation, and it is preferable to add an oxidation inhibiting element. The oxidation inhibiting element is preferably one or more of P, Ga, and Ge. If P, Ga, and Ge are large, solderability is hindered. For this reason, it is preferable that the addition amount of P, Ga, and Ge is 0.5 mass% or less with respect to the total amount of solder.
The mechanical strength improving element and the oxidation inhibiting element may not be added depending on the use, but only one or both may be added as necessary.
[0019]
The high-temperature lead-free solder alloy of the present invention can be used for electronic components having functional elements such as coils and semiconductors. That is, it can be suitably used as a high-temperature solder alloy for joining the functional element and the external connection terminal inside such an electronic component.
The electronic component of the present invention is an electronic component in which a functional element and an external connection terminal are joined by soldering using a high-temperature solder alloy, and the high-temperature solder alloy includes 10 to 40% by mass of Sb and Cu. It has the composition which consists of 0.5-10 mass% and remainder Sn.
By using a high-temperature lead-free solder alloy having such a composition, the functional element and the external connection terminal are joined by soldering, so that the external joint terminal and the substrate are generally used as a lead-free solder mainly composed of Sn. Even when soldering is performed at a temperature of 240 to 260 ° C., the bonding state between the functional element and the external connection terminal can be maintained. That is, by using the high-temperature solder alloy having such a composition, sufficient heat resistance can be obtained when the electronic component is soldered to the substrate.
[0020]
The electronic component of the present invention may contain a mechanical strength improving element as a high temperature solder alloy used inside. By adding such an element for improving mechanical strength, sufficient reliability can be obtained even when soldering a portion where mechanical strength is required.
Moreover, the electronic component of this invention may contain an oxidation suppression element as a high temperature solder alloy used inside. By containing such an oxidation-inhibiting element, oxidation of the solder alloy can be suppressed during the manufacture of the electronic component.
[0021]
The electronic component of the present invention is a coil component using a coil as a functional element, for example. Moreover, it is good also as an electronic component which used the functional component as the semiconductor element.
[0022]
【Example】
Table 1 shows examples and comparative examples of the present invention.
[0023]
[Table 1]

In Nos. 1 to 15 in Table 1, the solidus temperature is around 240 ° C, but the heat of absorption at 260 ° C or higher is 50% or higher. In addition, the elongation at break in the tensile test is 0.3% or more, and it can be sufficiently used as solder. On the other hand, the heat of absorption at 260 ° C. or higher was inferior in heat resistance at 260 ° C. or higher.
Next, No. of this example. Using 1 to 15 high-temperature lead-free solder alloys, 100 coil parts each having an internal coil element and an external connection terminal joined thereto were produced, and a mounting experiment on a substrate was performed. For the coil component, the external connection terminal and the substrate were soldered and joined at a temperature of 260 ° C. using Sn-0.7Cu lead-free solder. After mounting on the substrate, the continuity of the coil components was confirmed, but all maintained good continuity and did not cause poor continuity. That is, it was confirmed that the bonding between the coil and the external connection terminal has good heat resistance.
[0024]
【The invention's effect】
As described above, the solder alloy of the present invention is almost solidified at 260 ° C. even though the solidus temperature is around 240 ° C. If the soldering temperature of the electronic component to be performed for the second time is 260 ° C or lower, a highly reliable soldering part that can securely hold the soldering part inside the electronic component can be obtained. is there.
[Brief description of the drawings]
FIG. 1 is a curve model (DSC curve) of an alloy system of the present invention obtained by measurement with a differential scanning line calorimeter.

Claims (9)

A high-temperature lead-free solder material, excluding powder and solder paste, characterized by comprising 10 to 40% by mass of Sb, 0.5 to 10% by mass of Cu, and the balance of Sn. 2. The high-temperature lead-free solder material further comprising one or more elements of Ni , Fe , Mo, Cr, and Mn added in a total amount of 0.5% by mass or less. High-temperature lead-free solder material excluding powder and solder paste. The shape according to claim 1 or 2, wherein one or more of Ag and Bi is further added to the high-temperature lead-free solder material in a total amount of 1% by mass or less. Except high temperature lead-free solder material. The shape according to any one of claims 1 to 3 , wherein one or more of Ge and Ga are further added to the high-temperature lead-free solder material in a total amount of 1% by mass or less. High temperature lead-free solder materials excluding powder and solder paste. An electronic component in which a functional element and an external connection terminal are joined by soldering using a high-temperature lead-free solder material excluding powder and solder paste, and the high-temperature lead-free solder material has an Sb of 10 to An electronic component having a composition comprising 40% by mass, Cu of 0.5 to 10% by mass, and the remaining Sn. One or more elements of Ni , Fe , Mo, Cr, and Mn are further added to the high-temperature lead-free solder material excluding the powder and solder paste, and a total of 0.5% by mass or less is added. The electronic component according to claim 5 , wherein a high temperature lead-free solder material is used. The high-temperature lead-free solder material, wherein one or more of either Ag or Bi is added in total to 1% by mass or less to the high-temperature lead-free solder material excluding the powder and solder paste. The electronic component according to claim 5 or 6 . The high-temperature lead-free solder material, wherein one or more of Ge and Ga are further added in a total amount of 1% by mass or less to the high-temperature lead-free solder material excluding the powder and the solder paste. The electronic component according to any one of claims 5 to 7 . Wherein, the functional device is an electronic component according to any one of claims 5 to 8 which is a coil element.

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