JP3758090B2 - SnCu-based lead-free solder alloy - Google Patents

Description

【００３３】
上記結果から明らかなように、実施例１〜2のはんだ合金のゼロクロスタイムは、０．７４〜０．８２秒であるのに対し、比較例１〜４では０．８１〜１．０４秒になっている。また、実施例１〜２のクリープ強度は、１７０〜１７４時間であるのに対し、比較例１〜４では９５〜１５８時間になっている。さらに、実施例１〜２の銅喰われ量は、０．０５〜０．１２ｇ／１０分であるのに対し、比較例１〜４では０．０６〜２．０４ｇ／１０分になっている。このことから、ＳｎＣｕＣｏ合金にＡｇ及び／またはＮｉを添加することによって、良好な銅喰われ量と濡れ性を維持し、クリープ強度が向上することがわかる。
【００３４】
【発明の効果】
以上述べた如く、所定の組成のＳｎＣｕＣｏ合金にＡｇ及び／またはＮｉを添加することによって、ＳｎＣｕ系のはんだ合金の実用化の要求特性を全てクリアーし得るはんだ合金が得られる。このようなＳｎＣｕ系のはんだ合金は、従来強く求められていたにもかかわらず得られなかったものであるから、これは極めて画期的な効果である。[0001]
[Technical field to which the invention belongs]
The present invention relates to a SnCu-based lead-free solder alloy used for metal bonding of electric / electronic devices.
[0002]
[Prior art]
Conventionally, a solder alloy containing lead such as 63 wt% Sn and 37 wt% Pb has been generally used as a solder alloy used for metal bonding of electric / electronic devices.
[0003]
It has been pointed out that lead-containing solder causes serious damage to the nervous system by drinking lead that has eluted from wastes such as soldered substrates when it penetrates groundwater. Therefore, many lead-free solder alloys that do not contain lead have been studied.
[0004]
As lead-free solder alloys not containing Pb, SnCu-based alloys, SnAgCu-based alloys, SnZn-based alloys, and alloys obtained by adding Bi, In, or the like have been studied.
[0005]
Among them, SnCu alloy is the most practical because it has a relatively high melting point compared to other lead-free solder alloys at 227 ° C, even though it is a Sn0.7Cu eutectic alloy. This is one of the promising materials.
[0006]
However, since this Sn0.7Cu eutectic alloy has a small difference between the melting point and the working temperature, poor soldering such as horning tends to occur. In addition, Sn0.7Cu eutectic alloy has a low creep strength, so it cannot be used in a portion having a large thermal stress load. Not only that, it is easy to corrode copper and iron-based alloys, and there is a problem of causing the so-called erosion phenomenon that corrodes the copper circuit of the board or corrodes the container of the solder bath. ing.
[0007]
In order to solve the problem of this SnCu alloy, an alloy in which Ag, Sb, Bi, and Ni are added to a Sn0.7Cu eutectic alloy has been proposed.
[0008]
Addition of Ag improves mechanical properties such as wettability and creep strength, but does not improve the corrosion resistance of Cu, but conversely promotes corrosion.
[0009]
By adding Bi, the wettability is remarkably improved and the creep strength is also improved, but the toughness is lowered when the elongation is lowered. Moreover, the improvement of the corrosion resistance of Cu is hardly seen.
[0010]
By adding Ni, creep characteristics are improved and Cu corrosion resistance is improved, but wettability is not improved.
[0011]
Recently, an invention in which 0.05 to 1.0% by weight of Co is added to improve the thermal fatigue characteristics of the SnCu solder alloy has been disclosed (see Patent Document 1). However, according to studies by the present inventors, although this has improved thermal fatigue properties, dross (wet oxide) tends to be formed during soldering, and soldering defects such as horning are generated. It has been found to be.
[0012]
[Patent Document 1]
JP2003-1482
[0013]
Therefore, the conventional SnCu-based solder alloy is still unsatisfactory from the viewpoint of not satisfying all the required characteristics for practical use.
[Problems to be solved by the invention]
[0014]
The present invention has been made in view of these points, has no soldering defects such as horn pulling, has excellent Cu erosion resistance, has excellent wettability and creep characteristics, and is practical. An object of the present invention is to provide a SnCu-based lead-free solder alloy that satisfies all of the required characteristics of the crystallization.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, as a result of intensive research, the present inventors have found that Cu is less than 0.1 to 1.5% by weight , Co is 0.01% by weight or more and less than 0.05% by weight, and Ag is found that 0.05 to 0.3 wt% and / or Ni is solder containing 0.01 to 0.05 wt%, may clear all properties required for practical use of the solder alloy of the SnCu-based, The present invention has been reached.
[0016]
That is, according to the present invention, Cu is 0.1 to less than 1.5 wt% , Co is 0.01 wt% or more and less than 0.05 wt%, Ag is 0.05 to 0.3 wt%, and / or Ni is contained in an amount of 0.01 to 0.05 % by weight , and the balance is Sn.
[0017]
[Action]
As described above, the Sn-based lead-free solder alloy can add Sn to the interface between Cu and solder of the substrate circuit, for example, by adding Co in an amount of 0.01% by weight or more and less than 0.05% by weight. The intermetallic compounds such as Co and Sn-Cu-Co are formed and the elution of Cu into the solder is suppressed, and the high strength intermetallic compound is formed in the solder, thereby improving the creep strength of the solder. To do. Further, by containing Co, the surface tension of the solder is lowered and the wettability of the solder is improved. However, if the Co content is increased, dross is likely to be formed. Therefore, if the Co content is reduced to such an extent that it is difficult to form dross, the creep strength becomes unsatisfactory.
[0018]
Furthermore, by containing at least one of the three elements of Ag, Ni, and Ge, the creep strength is improved, soldering defects such as horn pulling do not occur, and excellent corrosion resistance of Cu is obtained. Thus, an SnCu-based solder alloy having unprecedented properties satisfying all of the required properties for practical use excellent in wettability and creep properties can be obtained.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described.
[0020]
Range of Cu containing in the present invention is less than 0.1 to 1.5 wt%, the Cu is less than 0.1 wt%, is as erosion resistance and wettability of the Cu is poor, 1.5 If it is more than% by weight , the melting point will rise and soldering defects such as horning will occur during the soldering operation.
[0021]
By containing Co in an amount of 0.01% by weight or more and less than 0.05% by weight, copper erosion can be suppressed in the same manner as conventional Sn—Pb solder. The Sn-Cu, Sn-Co, and Sn-Cu-Co intermetallic compound layers formed at the soldering interface by containing Co are formed relatively thick in parallel to the soldering surface, suppressing copper elution. To do. When the Co content is less than 0.01% by weight, the barrier layer is thin and the effect of suppressing the elution of Cu is reduced. When the Co content is 0.05% by weight or more, dross (wet oxide) is formed during soldering. This causes soldering defects such as horn pulling.
[0022]
Addition of Ag has no effect on copper erosion resistance, but improves wettability and creep characteristics. If the amount is less than 0.05% by weight, the effect does not appear. If the amount is more than 0.3 % by weight, dross is likely to be formed during soldering, and soldering defects such as horn drawing occur.
[0023]
By adding Ni, the wettability is not improved, but the creep characteristics and the copper erosion resistance are improved. The effect is not exhibited when the amount is less than 0.01% by weight, and dross is easily formed when the amount is more than 0.05% by weight.
[0025]
EXAMPLES Next, an Example is given and this invention is demonstrated further.
[0026]
【Example】
Created a solder 4kg embodiment a composition of the following Table 1 (No1~No 2) and Comparative Example (No1~No4). Sn0.7Cu0.02Co (Comparative Example 4) means a solder alloy in which Cu is 0.7% by weight, Co is 0.02% by weight, and the balance is Sn.
[0027]
The obtained solder was measured for solid phase temperature / liquid phase temperature (° C.), creep strength (100 ° C., 4 kg), zero cross time (seconds), and copper biting amount (280 ° C., 10 minutes). The results are shown in Table 1 below. The test method was as follows.
[0028]
[ Solid phase temperature / Liquid phase temperature (℃)]
Using 500 g of solder, the melting point [ solid phase temperature / liquid phase temperature (° C.)] was measured by a cooling method.
[0029]
[Creep strength]
Insert a tin-plated copper wire of φ0.8 mm into a glass epoxy board of 30 mm × 30 mm × thickness 1.6 mm with a copper circuit of φ3.0 mm and a through hole of φ1.1 mm at the center, and soldering surface about After preheating to 100 ° C., the sample was placed in a solder bath heated to 280 ° C., when a test piece reached a predetermined temperature, a load of 4 kgf was applied, and the time until the soldered portion was broken was measured.
[0030]
[Zero cross time (seconds)]
A zero cross time (second) was measured using a wettability tester using a copper plate of 5 × 50 × 0.3 mm under conditions of an immersion depth of 2 mm, an immersion speed of 2.5 mm / second, and an immersion time of 10 seconds. The test temperature was the liquidus temperature + 35 ° C., and the flux was RMA type.
[0031]
[Copper bite amount (g / 10 min)]
2.5 kg of solder was placed in a magnetic dish and heated to melt at 280 ° C. In this solder, a copper plate having a width of 20 mm and a thickness of 1 mm was attached to the tip of a stirring blade having a diameter of 60 mm, and the tip of 20 mm was immersed in the solder. Subsequently, the stirring blade was stirred at 30 rpm for 10 minutes. In this case, the moving speed of the copper plate in the solder is about 1 m / min. The weight of the copper plate before and after the test was measured, and the amount of Cu eluted into the solder was measured.
[0032]
[Table 1]

[0033]
As is clear from the above results, the zero cross time of the solder alloys of Examples 1 and 2 is 0.74 to 0.82 seconds, whereas in Comparative Examples 1 to 4, it is 0.81 to 1.04 seconds. It has become. Further, the creep strengths of Examples 1 and 2 are 170 to 174 hours, while those of Comparative Examples 1 to 4 are 95 to 158 hours. Furthermore, the amount of copper erosion in Examples 1 and 2 is 0.05 to 0.12 g / 10 minutes, whereas in Comparative Examples 1 to 4, it is 0.06 to 2.04 g / 10 minutes. . From this, it can be seen that by adding Ag and / or Ni to the SnCuCo alloy, a good copper biting amount and wettability are maintained, and the creep strength is improved.
[0034]
【The invention's effect】
As described above, by adding Ag and / or Ni to a SnCuCo alloy having a predetermined composition, a solder alloy that can clear all the required characteristics for practical use of a SnCu-based solder alloy can be obtained. Such an SnCu-based solder alloy has been strongly demanded in the past, but has not been obtained. This is a very innovative effect.

Claims (1)

Cu is 0.1 to less than 1.5 wt% , Co is 0.01 wt% or more and less than 0.05 wt%, Ag is 0.05 to 0.3 wt%, and / or Ni is 0.01 SnCu-based lead-free solder alloy containing ~ 0.05 % by weight and the balance being Sn.