JPH0328996B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a solder made of Sn, Pb, or Sn-Pb, or a solder containing at least one of Ag, Bi, Sb, Ib, and Cd by adding germanium (Ge) to the solder. This invention relates to a solder alloy that suppresses the generation of oxides during melting and has improved solderability (wettability, sharpness, repellency, etc.). In general, solder is mostly used in a molten state when assembling electronic devices, manufacturing parts, automobile radiators, electrical components, etc. At this time, the molten solder alloy reacts with oxygen (O ₂ ) contained in the air or in the molten solder, generating a large amount of oxide (MeO). It is causing problems. This tendency is remarkable in jet-type solder baths used for soldering printed circuit boards when assembling electronic equipment, resulting in loss of solder material due to the generation of oxides and entrainment of the generated oxides into the jet part. Problems such as product defects are occurring due to this. On the other hand, due to the recent trend of electronic devices becoming lighter, thinner, shorter and smaller, products are becoming smaller and smaller, and there is also a growing demand for cost reduction from an economic standpoint. There is also increasing interest in low melting point solders that can lower the heat resistance of components. Currently, as a countermeasure against oxide formation in jet-type automatic soldering equipment, waxes containing fats and oils such as mineral oil and vegetable oil and reducing agents are generally used as antioxidants. When floating on the molten solder surface, the antioxidant cannot be expected to have a sufficient effect due to its physical properties in the drop-down part of the jet (the pressure point) where oxides are most prominently generated.
In other areas, the formation of oxides is simply prevented by blocking part of the liquid surface from the air. In addition, since many of these antioxidants are organic compounds, they change in quality due to the influence of heat in the soldering bath, causing carbonization, decomposition, smoke generation, thickening, etc., resulting in significant contamination of the soldering bath and the resulting oxidation. Combined with objects getting caught in the jet area, this causes a decrease in work efficiency. Furthermore, the use of phosphorus (P)-containing alloy materials has previously been proposed for the same purpose as the present invention (Japanese Patent Application Laid-Open Nos. 54-84817 and 1984-128459), but the added P content is Since P is selectively consumed by oxidation, the connection time for oxidation prevention is proportional to the amount of added P. Therefore, significant amounts of P must be added to maintain sufficient anti-oxidation duration. However, the addition of excessive P has an adverse effect on the properties of the solder, such as roughness, repellency, and poor wetting, so the upper limit of the P concentration must be suppressed to about 0.01 wt%. Therefore, when using a phosphorus-containing alloy, it is necessary to control the phosphorus content concentration, which leaves some problems in terms of manufacturing control. Furthermore, since the consumption rate of phosphorus is highly temperature dependent, it has the disadvantage that at high temperatures of 300°C or higher, phosphorus is consumed rapidly and the duration of oxidation prevention is extremely shortened.
Furthermore, since phosphorus is a non-metallic element, it has the disadvantage of easily causing electrical migration at the soldered portion after soldering. The present invention suppresses the generation of oxides during melting in solder made of Sn and/or Pb, or solder containing at least one of Ag, Bi, Sb, In, and Cd, and improves solderability. The purpose of the present invention is to provide a solder alloy with improved properties, and its feature is that germanium is contained in the solder in an amount of 0.0001 to 0.1 wt%, preferably 0.001 to 0.1 wt%.
This is because 0.05wt% was added. Ge used in the present invention shows a tendency opposite to that of P addition, such that as the additive concentration increases, solderability such as wettability and sharpness is improved, and the oxidation prevention duration is also extended. Therefore, it has the characteristic that changes in the content concentration have almost no effect on the product. Furthermore, since the oxidation rate does not change much even at high temperatures of 300°C or higher, it exhibits superior properties compared to phosphorus-containing alloys even when used at high temperatures.
Furthermore, since Ge is a metal similar to Sn and Pb, unlike the case of P, electrical migration at the soldered portion is small, and is rather small compared to additive-free solder. Furthermore, a major feature of the addition of Ge is that it improves the solderability of the solder alloy. The recent trend in the electronics industry is to reduce the size of products by making them lighter, thinner, and smaller, and to lower costs by using ICs and improving parts. There is a demand for the development of solder. The method usually used to develop highly reliable solders and low melting point solders is to mix metal elements such as Ag, Bi, Sb, In, and Cd with Sn, Pb, or a mixture thereof to form a multi-component alloy. Although it is
At this time, new defects may occur depending on the type, amount, etc. of the added element. For example, although the melting point of the low melting point solder mentioned in Example 3 was lowered due to the addition of Bi (135 to 165°C), the solderability such as wettability, spreadability, and scrapability was lower than that of the Sn-Pb binary alloy solder. indicates a value inferior to . However, this alloy contains Ge.
By adding , the solderability is improved and it is possible to obtain the desired low melting point, highly reliable solder alloy. Furthermore, when Ge is added to several types of Sn-Pb binary alloys, solderability is improved compared to alloys without the addition, and similar results are obtained when Ge is added to other multi-element alloys. . In other words, the addition of a small amount of germanium, which is a feature of the present invention, not only suppresses the amount of oxide produced when the solder alloy is melted, but also improves the solderability of the added alloy, that is, the wettability to the base metal compared to solder without additives. It has been shown that this method greatly contributes to higher reliability of solder, such as by improving soldering properties and sharpness, and by reducing the occurrence of icicles and bridging that cause soldering defects. Furthermore, it has been said that the solderability of these products is highly dependent on the working temperature (solder bath temperature), but the addition of germanium (Ge) proposed by the present invention improves the solderability as described in the claims. The effect of lowering the working temperature by 5 to 30°C is shown for all combinations of alloys. In other words, to use another expression, as is clear from the table of Example 1, by adding germanium, the same solderability is exhibited at a lower temperature than when using a solder alloy without additives at 250°C. This shows that. These characteristics are useful when soldering electronic devices.
It has the ability to lower the working temperature without changing the combination of solder alloys or the static properties associated with it, and it shows the possibility of eliminating the problems that occur when lowering the melting point of solder mentioned earlier. . Furthermore, the above characteristics apply not only to the tin (Sn)-lead (Pb) binary alloy solder as shown in Example 1, but also to the case of bismuth (Bi)-containing solder as shown in Example 3.
Also, bismuth (Bi), silver (Ag), antimony (Sb), indium (In), cadmium (Cd)
A similar effect is obtained when one to several types of metals are added to a Sn-Pb binary alloy to form a multi-component alloy. This is because, unlike conventional multi-component alloys, the addition of germanium improves the surface tension of the base alloy, the interfacial tension with the base material to be soldered or flux, and the fluidity of the molten solder alloy. It is. In addition, as one application example of the present invention, when used as a raw material for cream solder powder, the oxide film on the powder surface becomes thinner, thereby preventing the formation of so-called solder balls and showing the effect of increasing the reliability of soldering. . By adding Ge to the solder made of Sn and/or Pb mentioned above, or the solder containing at least one of Ag, Bi, Sb, In, and Cd, the effect of suppressing the generation of oxides and the solder In order to obtain the adhesion effect, Ge is added to these solders.
It is necessary to contain at least 0.0001wt%. In addition, if Ge is contained more than 0.1wt%, it becomes expensive.
Using a large amount of Ge increases the alloy price and makes it impractical. Preferably, Ge is contained in the solder in an amount of 0.001 to 0.05 wt%. Examples are shown below. Example 1 60% Sn-balance Pb (H60A*) solder and this
Ge0.0001wt%, 0.001wt%, 0.005wt%, 0.01wt
%, 0.05wt%, and 0.1wt% of solder were measured for the amount of oxide produced, wetting time, breaking time, and breaking tension. The results are shown in Table 1. Each measurement test method was as follows. Amount of oxide produced: Surface area 45.4cm 1.5Kg in ² solder baths
A rotary squeegee is attached to the surface of the solder, and the weight of the oxide produced is measured after one hour. Wetting time, breaking time, and breaking tension Measure using the meniscograph method under the following conditions. Solder melting temperature: 250℃ Flux: American gum rosin WW35% TPA solution Test piece: 2.0φ

[Table] Example 2 A 35% Sn-balance Pb (H35A) solder and a solder alloy to which Ge was added in the same proportion as in Example 1 were measured in the same manner as in Example 1, but at a melting temperature of 300.
I went as ℃. The results are shown in Table 2.

[Table] Example 3 A low melting point solder having a composition of 43Sn-43Pb-14Bi and a solder alloy to which Ge was added in the same proportion as in Example 1 were measured in the same manner as in Example 1, but at a melting temperature of 200. I went as ℃. The result is the third
Shown in the table.

[Table] Example 4 Using an automatic jet soldering bath with a capacity of 300 kg (model FS-300 manufactured by Nihon Denka Keiki Co., Ltd.), 63% Sn - balance Pb
Figure 1 shows a comparison (in time) of the amount of oxide produced at 250°C between the (H63A) solder and the solder alloy to which 0.05 wt% of Ge was added.

[Brief explanation of drawings]

Figure 1 shows H63A in the example and Ge added to it.
FIG. 3 is a diagram showing the relationship between time and the amount of oxide produced for an example of the present invention containing 0.005 wt%.

Claims (1)

[Claims] 1. Solder made of Sn or Pb or both;
Or 0.0001 to 0.0001 glumanium in solder containing at least one of Ag, Bi, Sb, In, and Cd.
A solder alloy characterized by the addition of 0.1wt%. 2. The solder alloy according to claim 1, to which 0.001 to 0.05 wt% of glumanium is added.