KR100844200B1 - Diluent Pb free solder Composition, electronic equipment and PCB with the same - Google Patents

Abstract

The present invention is to solve the problem that, when soldering by the conventional lead-free solder alloy, the molten solder is combined with oxygen to form an oxide to reduce the soldering workability, the copper erosion is increased to replace the entire solder in the solder tank , Silicon (Si) and cobalt (Co) are contained in a binary composition composed of tin (Sn) and nickel (Ni) or a ternary composition composed of tin (Sn), nickel (Ni), and phosphorus (P), More specifically, the lead-free solder composition for dilution containing 0.001% to 1.0% by weight of nickel, less than 0.001% to 0.05% of silicon, less than 0.001% to 0.01% of cobalt, 0.001% to 0.2% by weight of phosphorus, and tin, and using the same It relates to an electronic device and a printed circuit board.

Therefore, according to the present invention, the inclusion of silicon and cobalt at the same time continuously suppresses the generation of oxides generated during soldering, prevents discoloration and excellent mechanical properties, and lowers the copper content of the solder bath as it is used for dilution, so that the solder itself It is possible to obtain the effect of providing a lead-free solder composition for dilution having the effect of maintaining the melting point and the soldering properties of the resin.

Free lead, lead free solder compositions, solder alloys.

Description

Lead-free solder composition for dilution and electronic device and printed circuit board using the same {Diluent Pb free solder Composition, electronic equipment and PCB with the same}

1 is a schematic diagram showing the principle of suppression of oxide generation amount of the lead-free solder composition for dilution according to the present invention.

FIG. 2 is an element analysis result diagram and a result table of an initial state with respect to the schematic diagram of FIG.

FIG. 3 is an element analysis result diagram and a result table after a 3-hour dross experiment for the schematic diagram of FIG. 1. FIG.

FIG. 4 is an Auger Si measurement peak for the schematic diagram of FIG. 1. FIG.

FIG. 5 is a peak of Auger SiO ₂ measurement for the schematic diagram of FIG. 1. FIG.

The present invention relates to a lead-free solder composition for dilution and an electronic device and a printed circuit board using the same. More specifically, the present invention does not contain lead that is harmful to the human body, and is a binary composition composed of tin (Sn) and nickel (Ni) or a ternary composition composed of tin (Sn), nickel (Ni), and phosphorus (P). It contains silicon (Si) alone or contains silicon and cobalt at the same time, oxide generation is continuously suppressed, work efficiency of soldering is prevented and discoloration is prevented, and it is used for dilution to adjust the copper content and soldering characteristics. It relates to a lead-free solder composition for dilution having an effect that can be improved, and an electronic device and a printed circuit board using the same.

In the conventional case, lead-containing alloys have been used for a long time, and tin-lead-based flexible solders have been used as bonding materials in component mounting of printed circuit boards for a long time. More specifically, soldering is a bonding technique using soldering, and in particular, it is used as a bonding material for mounting small electronic components such as semiconductor chips and resistance chips on a printed circuit board (PCP). As a joining technique using such soldering, it is used as a bonding material for mounting small electronic components such as semiconductor chips and resistor chips, in particular on printed circuit boards.

Joining technology using such a solder is required to be more advanced because of the high density of component mounting in accordance with the recent miniaturization and high functionality of electronic products. On the other hand, as a soldering material, binary process alloys composed of tin (Sn) and lead (Pb) have been mainly used. However, when this is disposed of, lead is leaked, which causes environmental pollution. Reached. This is because lead has a fatal adverse effect on the human body following environmental pollution.

Therefore, in recent years, various environmentally friendly lead-free solder compositions have been developed and attempted by regulating or excluding lead in the manufacture of solder alloys. However, the lead-free solder composition according to the prior art has a higher melting point and lower wettability as compared to the flexible solder, and also causes severe oxidation of the molten solder during soldering, resulting in poor soldering workability, and improved quality and reliability of PCB Assey by soldering. It has a problem of deterioration.

In addition, the lead-free solder according to the prior art is used in accordance with the improvement of the soldering process, such as replacement of the reflow oven without the development of near the melting point of 183 ℃ of the conventional solder (Sn37Pb) while satisfying the soldering bonding properties such as wettability. This is because only a very limited number of low melting point metals such as Cu, Ag, Zn, Bi, In, etc. are targeted as the melting point drop addition element.

In addition, the lead-free solder according to the prior art does not satisfy the melting point of 183 ° C of the conventional solder (Sn37Pb) while satisfying the soldering bonding properties such as wettability, corrosion resistance. And most lead-free solders have a small melting point by adding a small amount of low melting point metals such as Cu, Ag, Zn, Bi, In to Sn, but the development of lead-free solders with low melting point (low melting point) is no longer possible. No progress has been made and the limit has been reached.

Therefore, the Ag system of SnAgCu and the non-Ag system alloy of SnCu of melting | fusing point 220 degreeC-230 degreeC are the mainstream now. As described above, in terms of lowering the melting point of the solder, improvement has reached a limit, and development is mainly focused on improving soldering characteristics, improving workability, and improving quality and reliability.

In addition, lead-free solder has a higher melting point, more expensive dross due to the use of expensive raw materials and soldering oxidation, resulting in higher production costs, and increased oxides in the solder solder fillet of PCB Assey. ), The main cause of the deterioration of the quality and reliability of soldering assembly.

In order to solve the above problems, as described in KR 10-0327767, JP 3622788, and JP 3296289, a solder alloy in which an anti-oxidation element such as P, Ni, Ge, and Ga is added to SnAgCu and SnCu-based mother alloy solders has been developed. It is. However, in the case of Ge, Ga, and Ni, which are additional elements, the melting point is increased, and when exposed to thermal processing and thermal fatigue due to hardening, there is a concern that the reliability may be degraded, such as cracks in the solder portion, and thus it is used in a limited manner. .

In particular, when P is added in a large amount, the adverse effect of bridging the soldering portion due to hardening of the solder alloy occurs. In addition, P melts on the soldering surface to prevent oxidation of the molten solder. However, P has a high volatility to temporarily prevent generation of oxides at soldering temperatures around 260 ° C. However, wave soldering (Wave) In the case of soldering and dip soldering, many hundreds of kilograms of solder are filled in the molten metal, followed by continuous use for several months by replenishing only a small amount of consumption. It shows only the anti-dross effect of OH and persistent oxidation has unexpected problems.

In addition, if the copper content increases by more than 1% due to copper pad erosion of the PCB, the melting point of the solder rises sharply, and the wettability deteriorates, which causes not only the problem of replacing the entire bath, but also a cause of cracking. Can be.

Accordingly, the present invention is to solve the above problems, the object of the present invention has a mechanical property and workability comparable to Sn-Pb and Sn-Ni-P solder, and does not contain tin (Pb) By containing silicon (Si) and cobalt (Co) in a binary composition composed of Sn), nickel (Ni) or a ternary composition composed of tin (Sn), nickel (Ni), and phosphorus (P), It is to provide a lead-free solder composition for dilution and the electronic device and printed circuit board using the same that the oxide utterance is continuously suppressed by the soldering work efficiency is improved.

Another object of the present invention is to include ultra-small amount of silicon (Si) and cobalt (Co) at the same time, lead-free for dilution to improve the solder bonding properties, such as preventing the occurrence of oxide, preventing discoloration after soldering, improved wettability and copper pad erosion of PCB It is to provide a solder composition and an electronic device and a printed circuit board using the same.

Still another object of the present invention is to provide a lead-free solder composition for dilution which maintains the melting point and soldering properties of the solder itself by lowering the copper content of the lead bath as it is used for dilution, and to provide electronic devices and printed circuit boards using the same.

The present invention provides a lead-free solder composition for dilution comprising 0.001% to 1.0% by weight of nickel, less than 0.001% to 0.05% of silicon, 0.001% to 0.2% by weight of phosphorus, and tin, and an electronic device and a printed circuit board using the same. In addition, the lead-free solder composition for dilution further includes 0.001 to less than 0.01% by weight of cobalt.

1 is a schematic diagram showing the principle of suppressing the amount of oxide generation of the lead-free solder composition according to the present invention.

As shown in the figure, in the case of wave soldering using a solder alloy containing P and Si elements to suppress oxide generation in the SnAgCu master alloy, first, a part of the amount of the added P and Si elements is After being consumed in the deoxidation of the molten solder master alloy, it is dissolved in some molten solder master alloy, but P and Si are hardly dissolved in the molten Sn, and most of the added P and Si elements float on the surface due to the specific gravity difference. do. In addition, the phosphate and silicon oxide film blocks oxygen and molten solder in the atmosphere to suppress oxide generation of the lead-free solder.

However, in the case of P, a portion of the surface floating on the surface forms an oxide film, but a large portion of the surface is volatilized to the atmosphere, thereby degrading the continuous suppression of oxide generation on the surface of the molten solder. On the other hand, Si does not volatilize to the atmosphere and continuously forms silicon oxide on the surface of the molten solder, thereby suppressing the oxide generation effect. Experimental data on this can be seen through FIGS. 2 and 3.

지점별 성분 데이터를 통해 확인할 수 있다. FIG. 2 is a result of Auger element analysis of a solder alloy cross section by melting and casting a predetermined ingot by melting and casting as actual measurement data of the schematic diagram of FIG. Figure 3 is an Auger element analysis result when the Ingot produced by the same method for 3 hours Dross experiment (oxidation experiment) at 260 ℃. As shown in Fig. 2, in the initial state, phosphorus is floated on the surface of the ingot, and is mostly concentrated at 1.86% by mass at the top, and Si is distributed at the lower part of P.

This can be confirmed by point-specific component data.

지점에서도 P 보다는 Si이 더 잔존하고 있음을 알 수 있다. 또한, Auger의 Peak치를 보면, 상부에는 SiO₂로 간주되는 실리콘 산화물이 형성되어 있는 반면, 하부 방향 2, 3

지점에는 도4에서 알 수 있듯이 SiO₂ Peak치가 아닌 Si Peak가 나타나고 있다. As shown in Fig. 3, in the case of the dross experiment at 260 ° C. for 3 hours, P is 0.06% by mass and Si is 0.08% by mass, and Si remains relatively higher than P.

It can be seen that Si remains more than P at the point. In addition, the peak value of Auger shows that silicon oxide, which is regarded as SiO ₂ , is formed on the upper side, while the lower directions 2 and 3

As shown in FIG. 4, the Si peak is shown, not the SiO ₂ peak value.

From the above results, after P and Si were floated in the order of P and Si from the molten solder in the order of specific gravity from the molten solder, P was substantially volatilized and only a part of the oxide film was formed by continuous contact with air. On the other hand, in the case of Si, most of the addition amount forms a silicon oxide film such as SiO ₂ to suppress oxidation of the molten solder.

Looking at the properties and uses of the composition of the lead-free solder composition according to the invention as follows.

Sn (tin) is used as the base metal as an essential component of lead-free solders.

Ni (nickel) is an additive element for preventing copper pad erosion and improving bond strength. The addition of less than 0.001% by weight is not effective. When it is added in excess of 1.0% by weight, Ni (nickel) increases from 0.001 ~. It is preferably included in 1.0% by weight.

The P (phosphorus) is to improve the work of soldering by suppressing the formation of oxide during soldering, when added in less than 0.001% by weight, the effect does not occur, when added in excess of 0.2% by weight, Melting | fusing point rises and the optimum content is 0.001-0.2 weight%.

Si (silicon) is a main additive element of the present invention, which is floating and nonvolatile, and suppresses the generation of oxides by adding a small amount to the solder master alloy of Sn-Ni-P, even though phosphorus (P) has elapsed for a long time. The effect lasts, and it is not only excellent in preventing discoloration of the soldered part after soldering, but also improves anti-corrosion effect.

Co (cobalt) is not floating, but addition with Si further suppresses the formation of oxides during soldering with a small amount of addition, and further improves soldering properties and workability such as discoloration and erosion prevention.

Hereinafter, the function and effect according to the composition range of the composition through the experimental data with respect to the preferred lead-free solder composition for dilution according to the present invention and an electronic device and a printed circuit board using the same will be described in detail.

The lead-free solder composition for dilution according to the present invention comprises nickel, silicon, phosphorus, cobalt and tin.

Hereinafter, the antioxidant effect according to the composition range of the silicon and cobalt through the graph 1 will be described in detail.

The following graph 1 is experimental data of the amount of oxidation generated, by selectively or simultaneously dissolving silicon and cobalt in a tin-nickel-phosphate master alloy according to the content of the content to form a soldering composition, the soldering composition diameter 160mm SUS Heated to 260 ° C. using a hotplate in the crucible. Then, the resultant was stirred for 1 hour, 2 hours, and 3 hours at a rotational speed of 60 rpm using a stirrer having a diameter of 140 mm, and the amount of oxidation was measured by measuring the weight of oxides by time.

In addition, Auger Electron SpectrosCopy (manufacturer: Ulvac PHI, model name: PHI700) is an equipment that measures oxides for 3 hours, cuts and solidifies solidified solder into cross sections, and analyzes elements on metal surfaces using X-ray beams. The residual content of the added element was confirmed by analyzing the element content added to the solder using the.

Graph 1.

As shown in Graph 1.Sn0.06Ni0.005P containing 0.06% by weight of Ni, P 0.005 and Sn as remainder, the oxide generation amount was 125 (g) after 1 hour, 195 (g) after 2 hours, 3 After a lapse of time, a total of 640 (g) occurred at 320 (g).

When 0.005% by weight of Si is included in Sn0.06Ni0.005P, the amount of oxide generated is 105 (g) after 1 hour, 134 (g) after 2 hours, and 155 (g) after 3 hours. g) was generated, and the amount of oxidation generated was reduced compared to Sn0.06Ni0.005P.

From the above results, when 0.005% by weight of P was added, the occurrence of dross increased rapidly in the 3 hours, while when 0.005% by weight of Si was added, the oxidation rate was similar to that of 2 hours. It can be said to have a continuous antioxidant effect. And, if it contains 0.05% by weight of Si, it can be seen that the amount of oxidation generated is further reduced.

In addition, when 0.01 wt% of Co is included in the Sn0.06Ni0.005P0.05Si, the amount of oxide generated is 81 (g) after 1 hour, 99 (g) after 2 hours, and 110 (g) after 3 hours. A total of 290 (g) was generated, it can be seen that the amount of oxidation is reduced compared to the Sn0.06Ni0.005P and Sn0.06Ni0.005P0.05Si.

In addition, when the Sn0.1Ni0.005P0.005Si contains 0.005% by weight of Co, it can be seen that the amount of oxides is reduced by the addition of a small amount of Si and Co compared to the comparative material.

Therefore, when a small amount of Si is added to the Sn-Ni-P master alloy, it can be confirmed that the amount of oxidation is continuously prevented compared to the conventional P-added soldering composition, and Si and Co are simultaneously added in small amounts. In this case, it can be confirmed that it is prevented more continuously and effectively.

Hereinafter, the wettability according to the component composition range of silicon and cobalt will be described in detail through Graph 2.

Graph 2 below is an experimental data on the wettability. In order to measure the wetting time of the soldering composition, the melting time after melting for 5 seconds was measured by melting the solder at 260 ° C. using a MalCom SP2 Wetting Tester.

Graph 2.

As shown in Graph 2., the wet time of Sn0.06Ni0.005P containing 0.06% by weight of Ni, P 0.005 and Sn as remainder is 2.15 sec.

And, in the case of including 0.005% by weight of Si in the Sn0.06Ni0.005P, the wet time is 2.05sec, when incorporating 0.05% by weight of Si, the wet time is 2.17sec compared to the wet time of Sn0.06Ni0.005P. It can be confirmed that the increase.

In addition, when 0.01 wt% of Co is included in Sn0.06Ni0.005P0.005Si, the wetting time is 2.20 sec, and when we include 0.000.00 wt% of Co in Sn0.1Ni0.005P0.005Si, the wet time is 2.17sec.

Therefore, when 0.005% by weight of Si is added to the Sn-Ni-P mother alloy, the wettability is slightly improved, but when the weight is 0.05% by weight or more, the wettability may be confirmed. The wettability is slightly improved by removing oxygen in the molten master alloy solder (SnAgCu) by adding a very small amount of Si to 0.005% by weight, but when added by 0.05% by weight or more, it is melted by excess Si with an increase in melting point. It is considered that the wettability of solder is poor. In addition, when Si and Co are added in small amounts simultaneously, the wettability is further improved, but when Co is added in a large amount, for example, 0.01 wt% or more, the wettability is lowered.

Hereinafter, the copper erosion according to the composition range of the silicon and cobalt through the graph 3 will be described in detail.

The following graph 3 is experimental data on copper erosion amount, in order to measure copper erosion amount, the solder is melted and maintained at 260 ° C., and copper wire having a diameter of 0.8 mm is immersed in a molten solder at a depth of 30 mm for 60 seconds, and then The copper wire was taken out and the weight before and after dipping was measured to obtain the erosion rate (%), and the average value of five samples was calculated.

Graph 3.

As shown in Graph 3, the copper erosion amount of Sn0.06Ni0.005P containing 0.06% by weight of Ni, 0.005% by weight of P and Sn as a balance is 48.8%.

In addition, when 0.005% by weight of Si is included in Sn0.06Ni0.005P, copper erosion is 46.5%, and when 0.05% by weight of Si is included, copper erosion is 44.5%, compared to Sn0.06Ni0.005P. It can be confirmed that the decrease.

In addition, in the case of including 0.01 wt.% Co in Sn0.06Ni0.005P0.005Si, it can be seen that the concentricity was significantly reduced to 11.9%.

Therefore, when a small amount of Si is added to the Sn-Ni-P master alloy, the copper erosion amount can be confirmed to be reduced, and when the Si and Co are added in very small amounts, it can be confirmed that the copper needle amount is significantly reduced.

Hereinafter, referring to Table 1, the amount of oxide generation, melting point, discoloration, wetting time, copper erosion rate, and bonding strength according to the composition range of silicon and cobalt are described in detail, and the silicon included in the Sn-Ni-P mother alloy is described in detail. And the optimum content of cobalt.

Table 1 is a comprehensive experimental data for each composition range of silicon and cobalt including the above-described graphs 1,2 and 3, and adding test data of melting point, discoloration and bonding strength.

Table 1.

First, as shown in the melting point data of Table 1, the melting point of Sn0.06Ni0.005P containing 0.06% by weight of Ni, P 0.005 and Sn as remainder is 236 ° C, and 0.005% by weight of Si of Sn0.06Ni0.005P. Melting point is 236 ° C when including, and melting point rises slightly to 238 ° C when 0.1 weight% of Si is included in Sn0.06Ni0.005P.

In addition, the melting point slightly increased to 237 ° C. when 0.01 wt% of Co was included in Sn0.06Ni0.005P0.05Si. From the above results, when a small amount of Si having a high melting point of 1400 ° C. or higher is added to the low melting point Sn alloy in the state of metal alloy state, the melting point increases rapidly, but the melting point rise is insignificant compared to the amount of Si added. This is probably due to the surface of the molten solder.

Next, in order to measure the discoloration of the alloy composition, the color change data of Table 1 was made by depositing an oxygen-free copper (99.99%) of 25X31X0.3mm at 420 ° C for 3 seconds to make a specimen, and then heating the specimen at 250 ° C for 10 minutes. The degree of discoloration was measured using a chromatic aberration meter of the Minolta CM3700B model.

As shown in Table 1, the discoloration degree of Sn0.06Ni0.005P containing 0.06% by weight of Ni, P 0.005 and Sn as a balance is 21.03.

And, when the 0.005% by weight of Si in the Sn0.06Ni0.005P, the degree of discoloration is 18.76, when including 0.05% by weight of Si, the degree of discoloration is significantly reduced to 12.02, compared to the discoloration degree of Sn0.06Ni0.005P It can be confirmed that it is reduced.

In addition, in the case of including Co 0.005% by weight of Sn0.06Ni0.005P0.005Si, the degree of discoloration is 9.9, and when it contains 0.01% by weight of Co, it can be seen that the discoloration is greatly reduced to 4.5.

Therefore, when a small amount of Si is added to the Sn-Ni-P master alloy, it is confirmed that the discoloration is reduced, and when a small amount of Si and Co are added at the same time, the discoloration is significantly reduced.

Next, the bond breaking load (kgf) data of Table 1 is used to measure the bond breaking load by using a tensile tester after vertically inserting a wire of 2 mm diameter plated with tin-bismuth into the hole of the PCB substrate and wave soldering it. Junction fracture load (kgf)

As shown in Table 1, the bonding fracture load of Sn0.06Ni0.005P containing 0.06% by weight of Ni, P 0.005 and Sn as a balance is 83 kgf.

When the Sn0.06Ni0.005P contains 0.005% by weight of Si, the bond breaking load is 94kgf. When the Sn0.06Ni0.005P contains 0.05% by weight of Si, the bond breaking load is 96kgf. It can be confirmed that the improvement compared to the above.

In addition, when including 0.00 0.005 wt.% Co in Sn0.06Ni0.005P0.005Si, the bonding break load was 95kgf, and when the Co 0.01 weight% was included, the bonding break load was significantly improved to 100.

Therefore, when a small amount of Si is added to the Sn-Ni-P master alloy, it can be confirmed that the bonding fracture load is improved. When Si and Co are added in small amounts at the same time, the bonding fracture steel is significantly improved.

As described above, the lead-free solder composition according to the present invention maintains the conventional lead-free soldering temperature and wettability by adding a small amount of Si to the Sn-Ni-P master alloy, the amount of oxides is continuously reduced, and copper erosion This decreases, the discoloration decreases, and the bond breaking strength increases.

In addition, when a small amount of Co is added to the Sn-Ni-P mother alloy containing a small amount of Si, the amount of oxides is continuously reduced, copper erosion is decreased, and discoloration is reduced as compared with Si alone. And the breaking load is increased.

However, in the case of containing a large amount of Si, that is, containing 0.05% by weight or more, the melting point is slightly increased, and considering the inferior wettability to the joined object, the optimum content of Si is less than 0.001 to 0.05% by weight. to be.

In addition, when Co is contained in a large amount, that is, when it is contained in 0.01 weight% or more, wettability is inferior. In addition, with a small amount of 0.05% by weight of Si, even when the addition of a very small amount shows excellent effects, the optimum content of Co is 0.001 to less than 0.01% by weight.

In addition, Cu (copper) in the Sn-Ni-P master alloy lowers the melting point slightly, improves the bonding strength of the bonded body, the addition of less than 0.1% by weight is less effective, the addition of more than 2% by weight increases the melting point Therefore, the optimum value of the optimum content of copper is 0.1 to 2% by weight, nickel is for suppressing the intermetallic compound growth on the joint surface, the optimum content is 0.001 to 1.0% by weight. This is because the melting point increases as the nickel content increases, and the wettability and spreading rate decrease. In addition, P (phosphorus) is for improving the work of soldering by suppressing generation of oxide during soldering, and has an optimum content of 0.001 to 0.2% by weight. Sn (tin) is used as the base metal as an essential component of lead-free solders.

In addition, the lead-free solder composition for dilution according to the present invention may be used in the form of bar and wire, and is implemented as an electronic device including a plurality of electronic components fixed by a lead-free solder alloy. The electronic device is applied to various products such as a computer, a digital video camcorder, a digital television, a digital camera, a mobile communication terminal, and the like.

In addition, the present invention is a printed circuit board is fixed by a lead-free solder alloy for dilution, the lead-free solder alloy for dilution is 0.001% to 1.0% by weight of nickel, less than 0.001% to 0.05% by weight of silicon, less than 0.001% to 0.01% by weight of cobalt and tin In another embodiment, the lead-free solder alloy for dilution may include 0.001% to 1.0% by weight of nickel, less than 0.001% to 0.05% of silicon, less than 0.001% to 0.01% of cobalt, and tin. It is implemented as a printed circuit board containing the remainder.

The present invention described above is not limited to the above-described embodiments, and various permutations, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be obvious to him.

As described above, the present invention has mechanical properties and workability comparable to those of Sn-Pb and Sn-Ni-P solders, and is made of tin (Sn) and nickel (Ni) without containing Pb. Silicon (Si) and cobalt (Co) are contained in the ternary composition or the ternary composition composed of tin (Sn), nickel (Ni), and phosphorus (P), and the ignition of the oxide is continuously suppressed by the silicon so that soldering is performed. It improves work efficiency, prevents discoloration, and contains very small amount of silicon (Si) and cobalt (Co) at the same time. As it is used for dilution, it has the effect of providing a lead-free solder composition for dilution that maintains the melting point and soldering characteristics of the solder itself by lowering the copper content of the lead bath and the electronic device and the printed circuit board using the same. .

Claims (10)

0.001% to 1.0% nickel, less than 0.001% to 0.05% silicon, and tin Lead-free solder composition for dilution. The method of claim 1, Containing 0.001 ~ 0.2% by weight more Lead-free solder composition for dilution. The method according to claim 1 or 2, Cobalt further comprises 0.001 to less than 0.01% by weight Lead-free solder composition for dilution. An electronic device comprising a plurality of electronic components fixed by a lead-free solder alloy for dilution, The lead-free solder alloy for dilution comprises 0.001% to 1.0% by weight of nickel, less than 0.001% to 0.05% by weight of silicon and tin. Electronics. The method of claim 4, wherein The lead-free solder alloy for dilution Containing 0.001 ~ 0.2% by weight more Electronics. The method according to claim 5 or 6, The lead-free solder alloy for dilution Cobalt further comprises 0.001 to less than 0.01% by weight Electronics. The method of claim 4, wherein The electronic device is one of a computer, a digital video camcorder, a digital television, a digital camera, and a mobile communication terminal. Electronics. A printed circuit board fixed by a lead-free solder alloy for dilution, The lead-free solder alloy for dilution includes 0.001% to 1.0% by weight of nickel, 0.001% to less than 0.05% of silicon, and tin. Printed circuit board. The method of claim 8, The lead-free solder alloy for dilution Containing 0.001 ~ 0.2% by weight more Printed circuit board. The method according to claim 8 or 9, The lead-free solder alloy for dilution Cobalt further comprises 0.001 to less than 0.01% by weight Printed circuit board.

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