KR20070069069A - Lead-free solder, solder joint product and electronic component - Google Patents

Abstract

A lead-free solder, which has excellent oxidation resistance, mechanical properties, and plastic workability, can be molded into a ribbon or a filament, and can secure satisfactory solder bonding strength and reliability, and a highly reliable solder joint product formed by jointing with the lead-free solder, and an electronic component are provided. A lead-free solder comprises a tin (Sn)-based alloy having a tantalum(Ta) content of 0.005 to 2.0 wt.%. A lead-free solder comprises a tin(Sn)-based alloy comprising 0.005 to 2.0 wt.% of tantalum(Ta) and 0.1 to 10.0 wt.% of zinc(Zn) with the balance of tin(Sn) and unavoidable impurities. A lead-free solder comprises a tin(Sn)-based alloy comprising 0.005 to 2.0 wt.% of tantalum(Ta) and 0.1 to 60.0 wt.% of bismuth(Bi) with the balance of tin(Sn) and unavoidable impurities. A lead-free solder comprises a tin(Sn)-based alloy comprising 0.005 to 2.0 wt.% of tantalum(Ta) and 0.1 to 10.0 wt.% of indium(In) with the balance of tin(Sn) and unavoidable impurities. A lead-free solder comprises a tin(Sn)-based alloy comprising 0.005 to 2.0 wt.% of tantalum(Ta) and 0.01 to 7.5 wt.% of copper(Cu) with the balance of tin(Sn) and unavoidable impurities. A lead-free solder comprises a tin(Sn)-based alloy comprising 0.005 to 2.0 wt.% of tantalum(Ta) and 0.01 to 5.0 wt.% of silver(Ag) with the balance of tin(Sn) and unavoidable impurities. A lead-free solder comprises a tin(Sn)-based alloy comprising 0.005 to 2.0 wt.% of tantalum(Ta), 0.01 to 5.0 wt.% of silver(Ag) and 0.01 to 7.5 wt.% of copper(Cu) with the balance of tin(Sn) and unavoidable impurities.

Description

Lead-free solders, solder joints and electronic components {LEAD-FREE SOLDER, SOLDER JOINT PRODUCT AND ELECTRONIC COMPONENT}

1 is a photograph showing a thin film state of a melt of tin-3silver-0.5copper-4indium-0.05 tantalum solder formed on a substrate;

Fig. 2 is a photograph showing a thin film state of tin-3silver-0.5copper solder formed on a substrate.

3 is a photograph showing a thin film state of tin-3silver-0.5copper-4indium solder formed on a substrate.

Figure 4 is a tin-3 silver-0.5 copper-4 indium-0.05 tantalum solder according to the present invention formed when the surface tension of tin-3 silver-0.5 copper-4indium-0.05 tantalum solder was evaluated by a dropping method. Showing the shape of the droplets.

Fig. 5 is a diagram showing the shape of droplets of tin-3 silver-0.5 copper solder formed when the surface tension of tin-3 silver-0.5 copper solder is evaluated by the dropping method.

Fig. 6 is a diagram showing the shape of droplets of tin-3silver-0.5copper-4indium solder formed when the surface tension of the tin-3silver-0.5copper-4indium solder was evaluated by a dropping method.

FIG. 7 is a simplified illustration of the thermal cycle test performed in Examples 1 and 2. FIG.

Explanation of symbols for the main parts of the drawings

100... copper

101. Copper plated silicon nitride substrate

102. Ribbon solder

The present invention relates to a lead-free solder having excellent antioxidant power, mechanical properties and wettability, which can be easily calcined, and a solder joint product formed by joining with a lead-free solder.

In recent years, there has been a growing interest in environmental issues from the viewpoint of extensive environmental protection. Under these circumstances, an increase in the amount of abandoned industrial waste is a serious problem. Solders are used, for example, in substrates in power control computers, home appliances, and personal computers included in industrial waste. Harmful heavy metals such as lead sometimes leak from this solder. For example, when lead is leaked, lead can cause acid rain and form lead-containing aqueous solutions, which often soak into groundwater.

In Japan, the Household Appliances Recycling Act was enacted in 1998, and the recycling of consumed household appliances was required for household appliances in 2001. In Europe, the use of lead as a specific substrate has been banned since 2004 by orders of the European Parliament and the Commission on Waste of Electrical and Electronic Equipment. In this way, laws regarding the use of lead have been strictly regulated, ultimately requiring lead-free solders (see, for example, Non-Patent Document 1).

Solders play an important role in the mechanical and electrical connection of multiple device components used under some circumstances, including thermal cycling, mechanical shock, mechanical vibration, and the like. Also, in lead-free solders, lead-free solders having melting points similar to those of conventional tin (Sn) -lead (Pb) solders have good mechanical and wet properties and are sufficiently advantageous to be cast in the form of ribbons or fine fibers. There has been a need for lead-free solders with good plasticity.

However, in conventional lead-free solders, tin (Sn) -zinc (Zn) or tin (Sn)-to provide a melting point similar to that of tin (Sn) -37 wt% lead (Pb) solder (melting point 183 ° C). A large amount of indium (In) or bismuth (Bi), for example tin (Sn) -copper (Cu), tin (Sn)- Ag) or tin (Sn) -copper (Cu) -silver (Ag) solder was added. For example, tin (Sn) -9.0 weight% zinc (Zn) (melting point 199 degreeC), tin (Sn) -58 weight% bismuth (Bi) (melting point 138 degreeC), tin (Sn) -0.5 weight% copper ( Cu) -4.0 wt% Silver (Ag) -8 wt% Indium (In) (melting point 208 ° C.) is referred to as this solder. However, these solders contain a large amount of components that cause embrittlement, so that, for example, the mechanical properties and the plasticization capability are degraded, and it is difficult to ensure satisfactory solder bond strength and reliability. In addition, these lead-free solders cause brittle failures and the like in the firing process, so that these lead-free solders are very difficult to successfully withstand ejection, rotation, wiring drawing, and the like. Thus, the molded product in the form of a ribbon or fine fiber is substantially not formed. For this reason, the application of lead-free solders has been considerably limited.

[Non-Patent Document 1] Proposal for the Directive of the European Parliament and the Commission on Waste Electrical and Electronic Equipment, Authority of the European Union, Brussels, 13. 6. 2000.

As described above, the conventional lead-free solder contains a large amount of components that cause embrittlement, so that, for example, the mechanical properties and the plasticization capability are degraded, and it is difficult to ensure satisfactory solder bond strength and reliability. In addition, since these lead-free solders cause brittle defects and the like on the firing process, it is very difficult for these lead-free solders to withstand ejection, rotation, and wiring design successfully. Thus, a molten product of solder in the form of a ribbon or fine fibers cannot be substantially formed. For the reasons mentioned above, the application of lead-free solders has been considerably limited.

The present invention has been made in view of solving the above problems of the prior art, and an object of the present invention is to obtain a lead-free solder that can be cast into ribbons or fine fibers with excellent antioxidant power, mechanical properties, and plasticity. To provide a solder joint product having high reliability, and an electronic component formed by joining with a lead-free solder.

The above object can be achieved by a lead-free solder comprising a tin-based alloy having a tantalum (Ta) content of at least 0.005% by weight and at most 2.0% by weight.

According to the present invention, tin comprises at least 0.005% by weight and at most 2.0% by weight of tantalum (Ta) and at least 0.1% by weight and 10.0% by weight of zinc (Zn), the remainder being composed of tin (Sn) and unavoidable impurities. A lead-free solder comprising a (Sn) based alloy is also provided.

According to the present invention, tin comprises at least 0.005% by weight and at most 2.0% by weight of tantalum (Ta) and at least 0.1% by weight and 60.0% by weight of bismuth (Bi), the remainder being composed of tin (Sn) and unavoidable impurities. A lead-free solder comprising a (Sn) based alloy is also provided.

According to the present invention, tin comprises at least 0.005% by weight and at most 2.0% by weight of tantalum (Ta) and at least 0.1% by weight and 10.0% by weight of indium (In), the remainder being composed of tin (Sn) and unavoidable impurities. A lead-free solder comprising a (Sn) based alloy is also provided.

According to the invention, tin comprises at least 0.005% by weight and at most 2.0% by weight of tantalum (Ta) and at least 0.01% by weight and 7.5% by weight of copper (Cu), the remainder being composed of tin (Sn) and unavoidable impurities A lead-free solder comprising a (Sn) based alloy is also provided.

According to the invention, tin comprises at least 0.005% by weight and at most 2.0% by weight of tantalum (Ta) and at least 0.01% by weight and 5.0% by weight of silver (Ag), the remainder being composed of tin (Sn) and unavoidable impurities A lead-free solder comprising a (Sn) based alloy is also provided.

According to the present invention, it comprises at least 0.005% by weight and at most 2.0% by weight of tantalum (Ta), at least 0.01% by weight and at most 5.0% by weight of silver (Ag) and at least 0.01% by weight and 7.5% by weight of copper (Cu), A lead-free solder is also provided that includes a tin (Sn) based alloy composed of tin (Sn) and unavoidable impurities.

In a preferred embodiment of the lead-free solder according to the invention, the tin-based alloy further comprises at least one additive component (Y) selected from the group consisting of indium and non-smooth.

In a more preferred embodiment of the lead-free solder according to the present invention, in the tin-based alloy, the content of the additive component (Y) selected from the group consisting of indium and bismuth is 10 wt% or less of indium and 60 wt% or less of bismuth.

In a preferred embodiment of the lead-free solder according to the invention, the tin-based alloy is from the group consisting of cobalt (Co), titanium (Ti), nickel (Ni), palladium (Pd), antimony (Sb), and germanium (Ge). It further comprises at least one additional component (X) selected.

In a more preferred embodiment of the lead-free solder according to the present invention, in the tin-based alloy, the content of the additive component (X) selected from the group consisting of cobalt, titanium, lead, antimony, and germanium is determined by the addition of the additive component (X). It is 0.5 weight% or less with respect to each, and when a some additional component (X) is contained, the total content of several additional component (X) will be 1.0 weight% or less.

Other lead-free solders in the present invention may be present in the form of creams, ribbons, fine fibers or rods.

According to the present invention, there is also provided a solder joint product formed by joining with any of the lead-free solders.

According to the present invention, an electronic component formed by contacting with any of the lead-free solders is provided.

The lead-free solder according to the present invention has excellent antioxidant power and can very easily and easily realize plasticization processes such as ejection, rotation, and wiring design. In addition, the lead-free solder according to the present invention, when used as a solder, is excellent in various properties required for the solder, for example, mechanical properties and wet properties. Thus, the present invention can provide a lead-free solder having excellent antioxidant power, mechanical properties, and plasticity treatment capability, ensure satisfactory solder bond strength and reliability, and can be plasticized with ribbons or fine fibers.

The lead-free solder according to the present invention has improved wettability even without substantially increasing the melting point, so that a significant improvement in solder bonding strength and reliability can be realized, while effectively preventing deterioration in the purpose of thermal bonding. can do. Accordingly, the present invention provides excellent bond strength and reliability, preferably a variety of electronic devices, such as LED light emitting devices, surface-condition electron-emitter displays (SEDs), or mounted substrates bonded thereto. It is possible to provide a solder joint product having a.

The lead-free solder according to the present invention comprises a tin-based alloy of tantalum containing not less than 0.005% and not more than 2.0% by weight of tantalum. The term "lead-free solder" as used herein generally refers to an alloy having a lead content of 1000 ppm or less.

The lead-free solder containing a predetermined amount of tantalum according to the present invention includes (i) tin-tantalum alloys, (ii) tin-zinc-tantalum alloys, (iii) tin-bismuth-tantalum alloys, and (iii) tin-copper-tantalum Alloys, (iii) tin-silver-tantalum alloys, and (iii) tin-copper-silver-tantalum alloys.

In the present invention, even if the lead-free solder belongs to any one of (i) to (iii), tantalum in an amount of 0.005% by weight to 2.0% by weight should be contained as an essential component.

Tantalum is an important component mainly to improve the wettability of solder and the mechanical properties of solder joints. Tantalum as an additional component reduces the surface tension of the melt of tin or tin-based alloys to improve the solder's ability to wet the soldered member. In addition, tantalum causes nucleation of the tin-tantalum intermetallic compound upon condensation treatment of tin or tin-based alloys, thereby contributing to the miniaturization of the crystal structure. When the tantalum content is more than 0.005% by weight, a satisfactory effect of miniaturization of the condensation structure can be achieved, but the effect of improving the wet properties derived from the reduction of the surface tension cannot be achieved. That is, when the tantalum content is 2.0% by weight or more, in some cases, excellent wettability can be realized, but unrefined tin-tantalum intermetallic compounds are formed under some cooling conditions, resulting in lower solder strength. The tantalum content in the lead-free solder according to the present invention is preferably from 0.05% to 1.0% by weight, and from 0.1% by weight to so that an optimum balance between wet and mechanical properties can be achieved and optimum solder properties can be realized. 0.5% by weight is particularly preferred.

The tin-tantalum lead free solder according to the present invention comprises tin, a predetermined amount of tantalum, various optional additional components (to be described in detail below) and unavoidable impurities. Since the tin-tantalum lead-free solder according to the present invention contains a small amount of tantalum, in the melting point region, the lead-free solder has excellent wet and mechanical properties simultaneously without changing the melting point of pure tantalum at 232 ° C.

The eutectic compound of tin-9% by weight zinc has the lowest melting point (melting point 198 ° C.) and is commonly used as a low melting lead-free solder. However, due to the high zinc content, this solder has the problem that an unrefined process structure will be formed, and as a result, satisfactory solder strength and reliability cannot be provided. The tin-zinc-tantalum lead free solder (ii) according to the present invention is particularly effective in solving the above problem. Specifically, tantalum contained in the solder reduces surface tension and significantly refines the tin-zinc process structure to realize a fine and uniform tin-zinc process structure. This improves the mechanical properties. In particular, the brittleness is significantly improved, and the occurrence of cracks can be suppressed when condensation occurs. This mechanism is also very effective in, but not particularly limited to, tin-zinc hypereutectic compounds having a zinc content of at least 9% by weight and hyperprocess compounds having a zinc content of at most 9% by weight.

The tin-bismuth-tantalum lead-free solder according to the present invention is similar to the tin-zinc-tantalum lead-free solder (ii) according to the present invention and the tin-57 wt% bismuth process compound (melting point 139 ° C.) is typically low Used as melting point lead-free solder. Although a portion of bismuth is dissolved in tin to prepare a solid solution, most of the bismuth is a simple substance that forms an unrefined process structure under some cooling conditions. The presence of this unrefined process structure is a major cause of brittle fracture in the solder sector. If solder strength and reliability are assured, the bismuth content should be below 5% by weight. The bismuth content is particularly preferably 0.1% to 1.0% by weight.

Tin-copper-tantalum lead-free solders, tin-silver-tantalum lead-free solders, and tin-copper-silver-tantalum lead-free solders according to the present invention are also known as tin-zinc-tantalum It has tantalum bonding effects common to lead-free solders and tin-bismuth-tantalum lead-free solders. Generally, compounds close to tin-0.5 to 0.75% by weight copper process compound and tin-0.5 to 0.75% by weight copper-3.0 to 3.5% by weight silver are close to the three-atomic process compound. In order to raise the melting point (liquid line temperature) of the solder, an overprocess compound having a copper content of 7.5% by weight, which is much higher than the copper content of the tin-0.7% by weight copper process compound, or a tin-0.7% by weight copper process compound Hyperprocessed compounds having a copper content of up to 0.5% by weight, much lower than the copper content, are also used. In all compounds of the tin-copper lead-free solder, tantalum bonding effects can be achieved. The same is true for tin-silver lead-free solders and tin-copper-silver lead-free solders.

In the lead-free solders (i) to (iii) according to the present invention, as described above, various additional components may be used if necessary. At least one additional component (X) selected from the group consisting of cobalt (Co), titanium (Ti), nickel (Ni), lead (Pd), antimony (Sb), and germanium (Ge) may be obtained. As a preferred example, this can be demonstrated. The use of additional component (X) can reduce the surface tension of the melt lead-free solder and improve the wettability. For example, Japanese Patent Application No. 6658/2004 describes that the surface tension is reduced by adding cobalt (Co), nickel (Ni), and lead (Pb).

With respect to all of cobalt, titanium, nickel, lead, antimony and germanium as additional components in the lead-free solder according to the present invention, the addition amount is preferably 0.005% by weight or more and 0.5% by weight or less. When the addition amount is 0.005% by weight or less, satisfactory surface tension reduction cannot be ensured. That is, when the added amount exceeds 0.5% by weight, the unrefined intermetallic compound will be formed under some cooling conditions, so that the mechanical properties sometimes deteriorate. When a some additive component (X) is contained in a lead-free solder, 1.0 weight% or less is preferable and, as for the total content of addition component (X), 0.7 weight% or less is especially preferable.

When the lead-free solder according to the present invention is tin-copper-tantalum lead-free solder, tin-silver-tantalum lead-free solder, or tin-copper-silver-tantalum lead-free solder, In addition to X), other additives may optionally be used. At least one additive component (Y) selected from the group consisting of indium (In) and bismuth (Bi) can be demonstrated as a specific preferred example of other additive components. When the additive component (Y) is used in the lead-free solder according to the present invention, the additive component (X) may be present or absent. In addition, in the lead-free solder according to the present invention, as long as the effect of the present invention is achieved, additional additive components may be present in addition to the additive component (X) and the additive component (Y).

Indium (In) is a useful component primarily for lowering the melting point of lead-free solders and is properly specified by balancing material costs with the acceptable temperature range of the electronic components applied. Generally, the addition amount of indium is preferably 10.0% by weight or less, and particularly preferably 50% by weight or less from the viewpoint of the antioxidant power.

Bismuth (Bi) is a useful component primarily for lowering the melting point of lead-free solders, and is not particularly limited to bismuth compounds. However, as described above, when solder strength and reliability are ensured, the bismuth content should be 5% by weight or less, with 0.1% by weight to 1.0% by weight being particularly preferred. When bismuth is contained together with indium, 0.1 weight%-1.0 weight% are especially preferable as a bismuth content.

Lead-free solders (i) to (i) according to the present invention and lead-free solders optionally containing an additive component (X) and an additive component (Y) according to the present invention are, for example, such as ejection, rotation, and wiring design. The firing process is very easy and well tolerated. In addition, the lead-free solders (i) to (vii) according to the present invention and lead-free solders optionally containing the additive component (X) and the additive component (Y) according to the present invention have various characteristics, such as bond strength and mechanical properties. It is particularly good in solders that require wet and wet properties.

Accordingly, the present invention can provide a solder joint product, preferably an electronic component having a variety of electronic devices, for example LED light emitting devices, surface-conduction electron-emitter displays (SEDs), or mounting substrates bonded thereto. , Excellent bonding strength and reliability.

The lead-free solder according to the present invention can be formed by any desired method, without particular limitation. For example, lead-free solders according to the present invention may comprise, for example, tin (Sn) and tantalum (Ta), and essential constructions such as zinc (Zn), bismuth (Bi), copper (Cu), or silver (Ag). Optional components, such as urea, additive component (X) or additive component (Y), and, if necessary, other, to form a lead-free solder having a thorough composition at temperatures at or below each melting point of the component. It may be formed by melt knead the components and then cooling the mixture. One or more of the essential and / or optional components described above is first alloyed with tin in an amount smaller than required or in an amount required to construct a mature lead-free solder. The lead-free solder according to the present invention is particularly preferably formed by alloying the remaining amount and the remaining amount of the necessary components and / or optional components with the alloyed product (first alloyed product) to provide a mature lead-free solder. As such, a solder comprising homogeneous and closely dispersed tin and the metal component can be readily formed. In order to prevent degradation in properties due to oxidation of the lead-free solder, the lead-free solder and its constituent components are preferably handled in inert air, such as nitrogen, argon, or helium gas air.

The lead-free solder according to the invention is in the form of a solid or paste at room temperature depending on, for example, the composition of the lead-free solder, the specific product state, and other states.

In this way, the lead-free solder according to the present invention is very easy and well tolerates firing processes, for example ejection, rotation, and wiring drawing. In addition, the lead-free solder according to the present invention, when used as a solder, is excellent in various properties required for solder, such as bond strength, mechanical properties, and wet properties.

The wet properties of lead-free solders according to the present invention include (i) the percent wet spread (%) specified in JIS Z 3198-3 for tin-tantalum lead-free solders, and (ii) tin-zinc-tantalum lead-free solders. 60 to 70% for (v) tin-bismuth-tantalum lead-free solder, 80 to 90% for (v) tin-copper-tantalum lead-free solder, 70-85% for (v) tin-tantalum-silver lead-free solder 75 to 85% for (iii) and 75 to 85% for tin-copper-silver-tantalum lead-free solder. For each of these lead-free solders, an improvement of 15% or more in the wet properties (percent spread) can be realized on the same solder as described above except that tantalum is not contained.

The wet properties of lead-free solders also allow for the visual observation of the state of the solder film formed from the molten solder, by placing a layer of solder having a predetermined thickness on the substrate and heating the gathered in air to a temperature at or above the melting point of the solder. Can be evaluated.

1 is a solder according to the present invention, which provides a ribbon solder of tin-3 silver-0.5copper-4indium-0.05 tantalum having a size of 25 mm in length x 25 mm in width x 150 μm, and as a flux The state of the ribbon solder 2 provided by placing the ribbon solder on a coated oxygen-free copper plate 1, heat-treating the assembly at a temperature of 250 ° C. to melt the solder, and then solidifying the solder. This diagram shows FIG. 2 is a diagram showing the same ribbon solder as in FIG. 1 except that Tin-3silver-0.5copper is used instead of the solder according to the present invention. FIG. 3 is a diagram showing the same ribbon solder as in FIG. 1 except that Tin-3silver-0.5copper-4indium is used instead of the solder according to the present invention.

As shown in these figures, the lead-free solder according to the present invention has excellent wettability and can form a solder film having a substantially uniform thickness on a substrate. That is, since the wet characteristics are unsatisfactory with respect to other solders, a part of the solder is subjected to the repulsive force in the molten state by the substrate. As a result, a uniform solder film cannot be formed, and a portion 3 in which the solder film is not attached or an excessively protruding portion 4 is formed. In addition, the outline of the solder film becomes unclear. In solders with poor wettability, satisfactory solder bond strength cannot be realized, and there is a high possibility that the solder flows out into unintended areas. In addition, such solders are particularly unsuitable in applications where high precision solder joint quality is required, for example as soldering or wiring of high accuracy electronic devices.

In addition, the wet properties of the solder can also be evaluated by measuring the surface tension of the solder in the molten state by the dropping method. The dropping method is a method of measuring surface tension using the property that a solder drop falls as a result of the solder drop exceeding the surface tension of the drop when the liquid falls through the annular tube opening.

FIG. 4 shows the shape of the solder droplets just before falling off when the melt of tin-3silver-0.5copper-4indium-0.05 tantalum in accordance with the present invention slowly flows through an annular tube opening with a diameter of 0.7 mm. FIG. 5 shows the same shape as the solder droplet in FIG. 4 except that Tin-3silver-0.5copper is used instead of the solder in FIG. FIG. 6 shows the same shape as the solder droplets in FIG. 4 except that Tin-3silver-0.5copper-4indium is used instead of the solder in FIG. In each of the figures, the surface tension γ of the molten solder is horizontal at the position of the maximum diameter d _{e of the} solder droplet and the distance d _e from the front end of the solder droplet in the horizontal direction immediately before the solder droplet falls. It is calculated from the relationship between the diameter d _s of solder droplets in the direction.

γ = g · ρ · (d _e ) ² / H

Here, γ represents surface tension, g represents gravity constant, d _e represents maximum diameter, and H represents correction factor (H = d _s / d _e ).

As derived from the above equation, the larger the d _s value, the smaller the surface tension. The smaller the surface tension of the solder, the better the wettability.

The surface tension of the tin-3 silver-0.5 copper-4 indium-0.1 tantalum solder according to the present invention shown in FIG. 4 is 0.40 to 0.42 N / m, and the surface of the conventional tin-3 silver-0.5 copper solder shown in FIG. The tension is 0.38 to 0.40 N / m, and the conventional tin-3 silver-0.5 copper-4 indium solder shown in Fig. 6 is 0.43 to 0.46 N / m.

From the above results, the incorporation of 4 indium in the conventional tin-3 silver-0.5 copper solder increases the surface tension, and incorporating 0.1 tantalum into the solder reduces the surface tension, thereby realizing excellent wet characteristics.

The lead-free solder according to the present invention has excellent antioxidant power, so that deterioration in various properties based on oxidation is greatly suppressed, and also it is possible to form much less so-called "dross" products mainly composed of oxides of solder. will be. For example, in the lead-free solder according to the present invention, the amount of dross formed is reduced to about one fifth of that in the case of tantalum lead-free solder.

Process of forming lead-free solder molten product

The process for forming a lead-free solder molten product according to the present invention includes an ingot casting step of melting and casting a lead-free solder according to the present invention to form an ingot, and a firing treatment step of firing the ingot to prepare a molten product. Characterized in that.

In general, conventional lead-free solders cannot be calcined without difficulty, and even if the calcining process can be performed successfully, there are difficulties in realizing mechanical properties, wet properties, and other properties satisfactory as the solder. That is, the lead-free solder according to the present invention can be very easily and well calcined, and even after the calcining treatment, may have excellent mechanical properties, wet properties, solder bond strength and other properties desirable as solders.

According to the process for forming a lead-free solder molten product according to the present invention, a solder molten product having a desired shape and size having desirable properties as a solder can be easily formed. In the present invention, lead-free solder molten products can be formed in a form that has not been realized so far by, for example, the use of conventional general lead-free solder in the form of ribbons, fine fibers or rods.

Specific examples of preferred ribbon-shaped lead-free solder molten articles according to the present invention include lead-free solder molten articles having a thickness of 50 to 500 μm, particularly preferably 100 to 150 μm. Specific examples of the preferred fine fiber-shaped lead-free solder melt products according to the present invention include lead-free solder melt products having a fine fiber diameter of 0.1 mm to 1 mm, particularly preferably a fine fiber diameter of 0.2 mm to 0.5 mm. The shape and dimensions of the rod-shaped lead-free solder according to the present invention are not particularly limited. However, in order to minimize the separation of chemical components in the cast rod-shaped lead-free solder melt product, a cooling rate of 1 ° C./sec or more is preferred. Further, examples of rod-shaped lead-free solder melt products include the direct rotation of rod-shaped lead-free solder molten products, or molten lead-free solder, with homogeneous structures formed by molding cast ingots and extruding them by firing such as rotation. It includes a rod-shaped lead-free solder produced by.

The lead-free solder molten product according to the present invention is particularly suitable as a solder molten product for solder bonding of electronic devices such as, for example, LED light emitting devices, and electronic components having surface-condition electron-emitter displays (SEDs) and mounting substrates. Do.

The lead-free solder and lead-free solder molten articles according to the present invention have substantially the same melting point as conventional lead-containing tin solder, and are of equal or superior quality solder joint strength and reliability than conventional lead-free solder and lead-free solder molten products.

Yes

<Example 1>

A lead-free solder consisting of tin-9.0 wt% zinc-0.1 wt% tantalum was melted and the melt was placed in a billet having a diameter of 100 mm and a length of 300 mm. Next, the billet was ejected into a rod material having a thickness of 10 mm and a width of 70 mm. After that, the rod material is rotated to prepare a ribbon having a thickness of 100 μm and a width of 70 mm.

Next, as shown in FIG. 7, after the flux was coated on the surface of the copper plate 100 having a thickness of 3 mm, a width of 50 mm, and a length of 60 mm, a thickness of 100 μm, a width of 40 mm, and Ribbon solder 102 having a length of 50 mm was placed on the coated copper plate 100. Next, a copper plated silicon nitride (SiN) substrate 101 having a thickness of 0.5 mm, a width of 30 mm, and a length of 40 mm was placed on top of the ribbon solder 102. The assembly was heated in nitrogen gas air to a temperature of 230 ° C. for 45 seconds to reflow. The bonded article thus obtained undergoes a thermal cycle test under the condition of -25 ° C to 125 ° C. After a 2000 cycle heat cycle test, the bonded product was inspected by an ultrasonic flaw inspection test. As a result, neither crack nor separation was found.

<Example 2>

Lead-free solder consisting of tin-0.5% by weight copper-2.5% by weight silver-4.0% by weight indium-0.1% by weight tantalum-0.1% by weight cobalt was melted and the melt was transferred to a billet having a diameter of 100 mm and a length of 300 mm. Put in. Next, the billet was ejected into a rod material having a thickness of 10 mm and a width of 70 mm. Thereafter, the rod material was rotated to prepare a ribbon having a thickness of 100 μm and a width of 70 mm.

Next, as shown in FIG. 7, after the flux is coated on the surface of the copper plate 100 having a thickness of 3 mm, a width of 50 mm, and a length of 60 mm, a thickness of 100 μm, a width of 40 mm, Ribbon solder 102 having a length of 50 mm was placed on copper plate 100. Next, a copper plating silicon nitride (SiN) substrate 101 having a thickness of 0.5 mm, a width of 30 mm, and a length of 40 mm was placed on top of the ribbon solder 102. The assembly was heated in nitrogen gas air to a temperature of 250 ° C. for 45 seconds to reflow. Thus, the bonded product was subjected to a thermal cycle test under the condition of -25 ° C to 125 ° C. After 4000 cycles of thermal cycle testing, the bonded product was inspected by ultrasonic flaw test. As a result, neither cracking nor separation was observed.

Comparative Example 1

A lead-free solder composed of tin-9.0 wt.% Zinc was melted and the melt was placed in a billet having a diameter of 100 mm and a length of 300 mm. The billet was then ejected into compartments having a thickness of 10 mm and a width of 70 mm. As a result, it has been found that numerous cracks occur in the sections within the edge portion in the direction perpendicular to the ejection direction. The ejected material was rotated to prepare a ribbon solder having a thickness of 100 μm, a width of 40 mm, and a length of 50 mm, and then the ribbon solder was cut and used as a sample.

Next, in the same manner as in Example 1, after the flux was coated on the surface of the copper plate 100 having a thickness of 3 mm, a width of 50 mm, and a length of 60 mm, a thickness of 100 μm and a width of 40 mm And a ribbon solder 102 having a length of 50 mm was placed on the coated copper plate 100. Next, a copper plated silicon nitride substrate 101 having a thickness of 0.5 mm, a width of 30 mm, and a length of 40 mm was placed on top of the ribbon solder 102. The assembly was heated in nitrogen gas air to a temperature of 230 ° C. for 45 seconds to reflow. The bonded article thus obtained was subjected to a thermal cycle test under the condition of -25 ° C to 125 ° C. After a 750 cycle heat cycle test, the bonded article was inspected by ultrasonic flaw test. As a result, many cracks were observed at the four corners of the bonded article.

According to the present invention, there is provided a lead-free solder which has excellent antioxidant power, mechanical properties, and plasticity processing ability and can be cast into a ribbon or fine fiber, and has a high reliability solder joint product formed by joining with a lead-free solder. , And electronic components are provided.

Claims (14)

A lead-free solder comprising a tin (Sn) -based alloy having a tantalum (Ta) content of 0.005% by weight to 2.0% by weight. Tin (Sn) -based alloy comprising 0.005% by weight to 2.0% by weight of tantalum (Ta) and 0.1% by weight to 10.0% by weight of zinc (Zn), the remainder being composed of tin (Sn) and unavoidable impurities Lead-free solder containing. A tin-based alloy comprising 0.005% by weight to 2.0% by weight of tantalum (Ta) and 0.1% by weight to 60.0% by weight of bismuth (Bi), the remainder consisting of tin (Sn) and unavoidable impurities Lead-free solder containing. Tin (Sn) -based alloy comprising 0.005% by weight to 2.0% by weight of tantalum (Ta) and 0.1% by weight to 10.0% by weight of indium (In), the remainder consisting of tin (Sn) and unavoidable impurities Lead-free solder containing. Tin (Sn) based alloy comprising 0.005% by weight to 2.0% by weight of tantalum (Ta) and 0.01% to 7.5% by weight of copper (Cu), the remainder being composed of tin (Sn) and unavoidable impurities Lead-free solder containing. Tin (Sn) based alloy comprising 0.005% by weight to 2.0% by weight of tantalum (Ta) and 0.01% to 5.0% by weight of silver (Ag), the remainder being composed of tin (Sn) and unavoidable impurities Lead-free solder containing. 0.005% by weight to 2.0% by weight of tantalum (Ta), 0.01% to 5.0% by weight of silver (Ag) and 0.01% to 7.5% by weight of copper (Cu), the remainder being tin (Sn) ) And tin (Sn) based alloys composed of unavoidable impurities. The method according to any one of claims 1 to 7, The tin-based alloy is lead-free solder further comprises at least one additive (Y) selected from the group consisting of indium and bismuth. The method of claim 8, In the tin-based alloy, the content of the additive component (Y) selected from the group consisting of indium and bismuth is indium 10 wt% or less and bismuth is 60 wt% or less. The method according to any one of claims 1 to 7, The tin-based alloy includes at least one additive component (X) selected from the group consisting of cobalt (Co), titanium (Ti), nickel (Ni), palladium (Pd), antimony (Sb), and germanium (Ge). It contains more lead-free solder. The method of claim 10, In the tin-based alloy, the content of the additional component (X) selected from the group consisting of cobalt, titanium, nickel, palladium, antimony, and germanium is 0.5% by weight or less with respect to each of the additional component (X), The lead-free solder in which the total content of the plurality of additional components (X) is 1.0% by weight or less when a plurality of additional components (X) are contained. The method according to any one of claims 1 to 7, Lead-free solder in the form of creams, ribbons, filaments or rods. A solder joint product formed by joining with a lead-free solder according to any one of claims 1 to 7. An electronic component formed by joining with a lead-free solder according to any one of claims 1 to 7.

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