JPH08164496A - Sn-zn solder, sn-zn-bi solder, method for surface treatment of same, and mounted substrate using it - Google Patents

Abstract

PURPOSE: To easily achieve the soldering of the printed circuit board even with the normal flux for the electronic equipment by incorporating the prescribed contents in Sn-Zn solder or Sn-Zn-Bi solder to prevent the oxidation of the molten Zn, and to improve the wettability. CONSTITUTION: The solder ball 3 consists of the Sn-Zn eutectic solder 1 at the center and the Au covered layer 2 on the surface. The solder ball 3 is made by preliminarily preparing the Sn-Zn eutectic solder ball 1, heating the solution where sodium metasilicate, sodium orthosilicate, and the interface active agent are solved in water, and dipping the Sn-Zn eutectic solder ball 1 therein to perform alkaline degreasing. Then, the ball is water rinsed, and dipped in sulfuric acid to remove the oxide film on the surface, water rinsed, and dipped in the solution where PdCl2 and HCl are solved in water to perform PD activation. Then, the ball is dipped in the solution for semi-bright Ni-plating to perform Ni-plating. After the water rinsing, the ball is dipped in sulfuric acid, dipped in the Au-plating solution to perform Au-plating to obtain the solder ball 3.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a television, a video,
Substrates or parts of electronic equipment such as personal computers, workstations, etc. are generally made of Sn, Zn or S.
The present invention relates to a connection using a solder alloy composed of n, Zn and Bi. These can be used, for example, for solder balls in a solder paste, BGA (ball grid array) solder balls, various electronic components, and coating of the terminal surface of a substrate, and do not contain Pb harmful to the human body. This can contribute to higher reliability in soldering of electronic circuit boards using solder.

[0002]

2. Description of the Related Art A conventional solder used for connecting a wiring board of an electronic device is composed of Sn and Pb (hereinafter referred to as Sn-Pb type solder). However, Pb contained in this has a problem that it is highly toxic to the human body. One of the solder materials that does not contain Pb and has no adverse effect on the environment is Sn and Zn or Sn.
There is a solder containing Zn and Bi (hereinafter referred to as Sn—Zn based solder, Sn—Zn—Bi based solder). Sn-Zn
The melting point of the eutectic solder is 199 ° C., which is close to the melting point (183 ° C.) of the Sn—Pb eutectic solder most commonly used for the conventional soldering connection.
It is a strong candidate for an alternative material for n-Pb based solder. Furthermore, the melting point of Sn-Zn-Bi solder is lower than that of Sn-Zn eutectic solder, and it is the most promising candidate as a substitute material for Sn-Pb eutectic solder. However, J. M., Jurai (1993), Item 36 (JOM, July 1993, p.
As described in 36), Sn-Zn based solder is
Since n is easily oxidized, there is a drawback that the wettability is remarkably poor as compared with the conventional Sn-Pb solder. Similarly,
Sn-Zn-Bi solder also has poor wettability as compared with Sn-Pb eutectic. In addition, by adding another element, the Sn--Zn
Attempts have been made to improve the wettability of solders or Sn-Zn-Bi solders, but it is difficult to obtain wettability equivalent to that of the Sn-Pb solders, and it has not yet been put to practical use. Therefore, the Sn-Zn-based solder and the Sn-Zn-Bi-based solder could not be used for soldering a wiring board or the like under the same conditions as the Sn-Pb-based solder. It is possible to use a highly active flux for soldering to improve the wettability, but there are cleaning problems after soldering and corrosion due to flux residue, which may cause problems in reliability after connection. is there.

[0003]

Problems to be Solved by the Invention Sn-Zn system, Sn-
The wettability of Zn-Bi solder onto Cu or solder plating is due to the strong oxide film of Zn, and therefore the conventional S
Extremely bad unlike n-Pb type solder. The present invention is S
In soldering using n-Zn-based or Sn-Zn-Bi-based solder, Zn contained in the solder when melted
The Sn-Zn-based or S-based Zn-Sn system or S
The present invention provides a surface treatment of an n-Zn-Bi solder and a mounted product.

[0004]

In order to achieve the above object, the present invention provides a metal having strong oxidation resistance on the surface of a Sn—Zn system or Sn—Zn—Bi system solder, or a normal electron even if oxidized. It coats another metal that is easily reduced by equipment flux. As the solder, Sn-Zn,
Sn-Zn-Bi or these, In, Ag, S
Sn containing one or more of b and Cu
-Zn-based and Sn-Zn-Bi-based solders are considered.

Regarding the surface treatment, Sn--Zn system, Sn
-Zn-Bi solder 1) Au 0.01 μm or more, 2) Sn or Sn alloy 2 μm or more, 3) Ni or Cu 0.01 μm or more, 4) Pd 0.01 μm or more, 5) Ag 0.01 μm or more, or Ni or C of the above 3) to 5)
The coating layer of u, Pd, or Ag is further coated with Sn or Sn alloy by 2 μm or more. The coating is performed by a method such as vapor deposition, plating and dipping.

Sn-Zn, Sn-Zn-Bi, or Sn-Zn-based or Sn-Zn-containing one or more of In, Ag, Sb, and Cu.
By coating the Bi-based solder surface with the above metal,
When the Sn-Zn-based solder or the Sn-Zn-Bi-based solder is melted, the solder does not come into direct contact with the atmosphere, and thus Zn oxidation, which is particularly problematic in wettability, does not occur unlike the conventional case. In addition, since the metal coating layer on the surface is thin, the coating layer easily cracks due to the volume expansion of the Sn—Zn-based and Sn—Zn—Bi-based solders at the time of melting, and the surface of the clean Sn is not oxidized. The -Zn-based and Sn-Zn-Bi-based solders come into contact with the base metal to cause wetting. Also, since the coating layer is thin, the amount of metal in the coating layer is small, and the molten S
The metal of the coating layer completely dissolves in the n-Zn-based or Sn-Zn-Bi-based solder, and the coating with these metals does not cause a problem in connection strength of soldering. In this way, by coating the surface with another metal, Sn--Zn
System, Sn-Zn-Bi-based solder can also secure sufficient wettability, and soldering can be performed with a normal electronic device flux without using a strong flux.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a view showing a solder ball according to an embodiment of the present invention. The solder ball 3 is composed of a central Sn—Zn eutectic solder 1 and an Au coating layer 2 on the surface thereof. The thickness of this Au layer is 0.5
μm.

A method of forming the solder ball 3 having such a structure will be described below. FIG. 2 shows a process flow of making the solder balls 3.

Sn-Zn eutectic solder balls 1 are prepared in advance. Next, a solution prepared by dissolving 30 g of sodium metasilicate, 20 g of sodium orthosilicate and 1 g of a surfactant in 1 l of water was heated to 70 ° C., and the Sn solution was added to the solution.
-Zn eutectic solder ball 1 was immersed for 10 minutes to perform alkaline degreasing. Then, it was washed with water and immersed in 5% sulfuric acid for 1 minute to remove the oxide layer on the surface. After that, wash with water, Pd
Pd activation treatment was carried out by immersing in a solution of 0.2 g of Cl ₂ and 100 ml of HCl in 1 l of water for 1 minute.
Then wash in water and apply 3 to the semi-bright Ni plating solution warmed to 65 ° C.
It was immersed for a minute and plated with Ni. Then, it was washed with water, immersed in 5% sulfuric acid for 1 minute, washed with water, immersed in an Au plating solution warmed to 90 ° C. for 5 minutes, and plated with Au. After washing with water and drying, the solder balls 3 shown in FIG. 1 were obtained. According to this method, a thin Ni layer remains between the Sn—Zn eutectic solder 1 and the Au layer 2, but since this Ni layer is thin, it does not interfere with the role of the Au layer on the surface and is not a problem. Also, this time, the Sn-Zn eutectic solder was used as an example to prepare the solder ball 3 of FIG. 1 by the electroless plating method as described above, but it is also applicable to the Sn-Zn-Bi solder and the method is not limited to this method. Not a thing.

When the solder ball having such a structure is heated and its temperature rises to reach the melting point of the Sn--Zn eutectic solder and melted, Au is present on the surface in a thickness of 0.5 .mu.m. The Zn contained in the solder does not oxidize because it does not come into direct contact with the atmosphere containing. Also, A
Since the surface coating layer of u is as thin as 0.5 μm, Sn-Z
Due to the volume expansion of the n-eutectic solder during melting, cracks easily occur, and a clean Sn—Zn eutectic solder whose surface is not oxidized and the underlying metal come into contact with each other for wetting. Also, Au
Because of the small amount of Au, Au dissolves into the Sn—Zn eutectic solder, and the surface coating layer does not deteriorate mechanical properties such as soldering strength. Thus, by coating the surface of the Sn—Zn eutectic solder with Au at 0.5 μm, it is possible to obtain a solder ball with improved wettability, which is a drawback of the Sn—Zn solder.

In this example, an example is shown in which Au is coated to a thickness of 0.5 μm, but the thickness of Au is not limited to this thickness, and may be 0.01 μm or more. Also,
In addition to Au, Sn or Sn alloy, Ni or C
It is also possible to improve the wettability by coating with u, Pd or Ag or by further coating Sn or Sn alloy on these Ni, Cu, Pd or Ag.

The material of the center solder is Sn in the above example.
-Zn eutectic solder, Sn-Zn-Bi or Sn-Zn, Sn-Zn-Bi solder In, Ag,
Sn containing one or more of Sb and Cu
Even with a -Zn-based or Sn-Zn-Bi-based solder, the wettability can be improved by the surface treatment having the above configuration.

Regarding Sn-Zn-Bi solder, Pb
A possible composition range as a substitute for -Sn eutectic solder was examined, and Table 1 shows the solder composition and melting point.

[0015]

[Table 1]

This composition range is 4 mass% ≦ Zn ≦ 6 mass%, 1
2 mass% ≦ Bi ≦ 19 mass%, which can be expressed by the remaining Sn. The Sn—Zn—Bi solder having the above composition has a liquidus temperature of 200 ° C. or lower and a solid phase temperature of 160 ° C. or higher as shown in Table 1, and thus is close to the melting point of the Sn—Pb eutectic solder. Therefore, 220 to 230, which is lower than the heat resistant temperature of the glass epoxy substrate.
The reflow is possible at a temperature of ℃, and the reliability at a high temperature of about 125 ℃ can be guaranteed. Other Pb-free solders that do not contain Pb include solders near the Sn-Ag eutectic and Sn-Ag-Bi solders in which Bi is added to Sn-Ag, but solders near the Sn-Ag eutectic are The solidus line is around 220 ° C, and in the Sn-Ag-Bi solder, when the liquidus temperature is lowered to 200 ° C or lower, the solidus temperature is lowered to 140 ° C or lower, and conversely, when the solidus temperature is raised to 150 ° C or higher. Since the liquidus temperature rises to 200 ° C. or higher, it is difficult to satisfy both conditions of reflowing to a glass epoxy substrate at 220 to 230 ° C. and guaranteeing reliability at high temperature. Therefore, the Sn-Zn-Bi solder having the above composition is suitable as a substitute material for the Sn-Pb eutectic solder. However, the Sn—Zn—Bi solder having the above composition has poor wettability as compared with the Sn—Pb eutectic. Therefore, for solder of this composition,
It is effective to perform a surface treatment to improve the wettability.

(Embodiment 2) Embodiment 2 shows an example in which a BGA (ball grid array) is prepared by using the solder balls 3 having the same structure as the solder balls shown in Embodiment 1.
FIG. 3 shows a process flow of BGA preparation. First, as shown in FIG. 3A, a chip is mounted on an internal substrate, Cu terminals 5 are present on the BGA body 4, and solder resists 6 are present between the Cu terminals 5. The BGA body 4 was prepared. Next, the flux 7 was printed on the Cu terminal 5 of the BGA body 4 as shown in FIG. On this flux 7, a solder ball 3 in which the surface of the Sn—Zn eutectic solder 1 is coated with Au 2 is mounted as shown in FIG.
Reflowed and then washed. Through the steps described above, the components in the Sn—Zn eutectic solder 1 react with Cu of the Cu terminal 5 to cause connection, and the bumps 8 are formed, as shown in FIG. I was able to create a simple BGA9.

In this BGA9, toxic P
Since Sn-Zn eutectic solder not containing b is used,
It does not affect the human body. Moreover, since the surface of the Sn—Zn eutectic solder 1 is covered with Au 2, the connection with the Cu terminal 5 is easy.

Here, an example of BGA using the solder balls 3 coated with Au is shown, but in addition to Au, a Sn-Sn alloy, a coating layer of Ni, Cu, Pd, or Ag, Sn-. Similar results can be obtained with Zn-based or Sn-Zn-Bi-based solder balls.

(Example 3) In Example 3, an example of a solder paste using a solder ball coated with Sn is shown. FIG. 4 shows an enlarged view of the solder paste of the present invention. Sn-
On the surface of the Zn eutectic solder ball 10, S with a thickness of 3 μm is formed.
The n-layer 11 is coated, and the flux components 13 containing an organic solvent, an activator, etc. are present between the solder balls 12. In this solder paste 14, when the Sn—Zn eutectic solder ball 10 in the paste is melted, the presence of the Sn layer 11 prevents the oxidation of Zn. Therefore, only the Sn—Zn based solder ball without the Sn layer 11 is used. It has better wettability than if it had been present. Therefore, it is possible to contribute to high reliability of soldering of a printed wiring board or the like.
The above-mentioned solder paste is used as a solder having a composition of 80 mass% Sn-15mass% Bi-5mass% Zn (hereinafter abbreviated as Sn-15Bi-5Zn), which is close to the Sn-Pb eutectic solder in terms of melting point.
It was similarly prepared by using a solder ball in which n was coated with 3 μm. A flux component exists between the solder balls. The flux component used was different from that used for the Sn-Zn eutectic solder. This solder paste also
When heated, Sn-15Bi-5Zn solder is 190 ℃
When melted in the vicinity, since the surface of the solder is coated with Sn, there is no problem of Zn oxidation and the wettability is excellent. Sn of the coating layer is molten Sn-15Bi-5Zn.
The solder that melts into the solder and has a clean surface without an oxide film is easily wetted and connected to the electrodes of the component or the substrate, and the solder balls are also easily aggregated,
Less solder balls are generated. Therefore, it is suitable for soldering a printed circuit board or the like.

(Embodiment 4) FIG. 5 shows an example of a connection terminal using the surface treatment of the present invention. The surface of the Cu lead 15 is covered with a Sn—Zn solder layer 16 with a thickness of about 10 μm, and the surface of the Cu lead 15 is covered with an Ag layer 17 of 1 μm. By using the connection terminal 18 having such a configuration, it is possible to prevent the Zn in the Sn—Zn solder layer 16 from being oxidized in the surface mounting using the solder paste or the flow soldering, and the wiring board is excellent. You can get a connection.

(Fifth Embodiment) In the fifth embodiment, Au, Sn,
Sn whose surface is coated with Ni, Cu, Pd, Ag
-Zn eutectic solder balls exhibit improved wettability as compared to uncoated solder balls.

Seven kinds of solder balls No. 1 to No. 7 in which the materials and thicknesses shown in Table 2 were coated on the surface of the Sn-Zn eutectic solder ball were prepared, and the wettability of the solder was evaluated. .

[0024]

[Table 2]

The wettability of the solder was evaluated by the following procedure. 1 each solder ball shown in Table 2 on the Cu plate
Each of them was placed one by one, and a fixed amount of weakly activated rosin flux was applied thereon. This Cu plate was placed on a hot plate set at 230 ° C. and heated, and 10 seconds after the solder balls were melted, the Cu plate was removed from the hot plate.
The heating was performed in the atmosphere. After the solder was solidified and washed with an organic solvent, the area where each solder ball wet and spread on the Cu plate (hereinafter referred to as a spread area) was measured. The above solder wettability evaluation is No. 1 to No. Each of the 7 types of solder balls up to 7 was performed 5 times, and the average thereof was calculated and shown in Table 3.

[0026]

[Table 3]

From these results, the Sn-Zn eutectic solder balls having no surface coating did not spread on the Cu plate, but No. 1 to No. It was found that all the solder balls up to 6 spread wet on the Cu plate and the wetness is improved. No. 1 to No. Among the solder balls up to 6, the solder ball having the most improved wettability was the solder ball having a surface coated with Sn of 3 μm. As described above, N of Table 1 was formed on the surface of the Sn-Zn eutectic solder ball.
o. 1 to No. It was found that the wettability can be improved by applying the coating shown in No. 6.

The above-mentioned experimental results are the results of an experiment using a solder ball having a surface coated with Sn-Zn eutectic solder. Sn-Zn-Bi, Sn-Zn, S
Even in the case of Sn-Zn based solder containing any one or more of In, Ag, Sb, and Cu in n-Zn-Bi, the same experiment shows that the wettability can be improved by performing the above-mentioned coating. I understood from.

An example of Sn-Zn-Bi solder is shown below. As can be seen from Table 1, 76 mass% S
Solder having a composition of n-5mass% Zn-19mass% Bi (hereinafter abbreviated as Sn-5Zn-19Bi) has a liquidus temperature of 186 ° C.
Since the solid phase temperature is 165 ° C. and the liquidus temperature is close to that of the Pb—Sn eutectic solder, reflow can be performed in the same furnace, ordinary electronic device flux can be used, and connections can be made in almost the same process. Although the solid phase temperature is as low as 165 ° C, the high temperature strength at 125 ° C can be guaranteed. 3 μm on the surface of this solder ball
Even if Sn is coated, the amount of Sn increases slightly after melting, but the melting point does not change much. With respect to this solder ball coated with Sn, Sn-5Zn-19Bi without coating was applied.
The solder balls and solder wettability were compared. In this experiment, the hot plate temperature was 220 ° C. As a result,
The Sn-5Zn-19Bi solder ball coated with Sn is the Sn-5Zn-19Bi solder ball not coated.
It was found that the wettability was improved by spreading the Cu plate on the Cu plate more greatly than that on the Cu plate. Similarly, 82 mass% Sn-5 mass% Zn-
Solder having a composition of 13 mass% Bi (hereinafter Sn-5Zn-1
3Bi) was also coated with Sn to 3 μm, and the wettability was measured, but Sn-5Zn-13B that was not coated was used.
It was found that the coated Sn-5Zn-13Bi solder had a larger spread area than i and the wettability could be improved.

[0030]

[Effect of the invention] Sn-Zn system or Sn-Zn-Bi
Au, Sn or Sn alloy, Ni on the surface of the system solder
Alternatively, by using the present invention for coating any of Cu, Pd, and Ag, the disadvantage of Sn—Zn-based solder that Zn is oxidized at the time of melting and wettability is improved,
It can be easily soldered with a flux for ordinary electronic equipment with weak activity. These technologies are applied to solder balls for solder paste for normal soldering, BGA
It can be used as a solder ball for coating, coating on the surface of the connection terminal, etc., and can contribute to high reliability of soldering of a printed wiring board using a solder containing no Pb which is toxic to the human body.

[Brief description of drawings]

FIG. 1 shows a solder ball according to an embodiment of the present invention.

FIG. 2 shows a process flow for making solder balls of the present invention.

FIG. 3 shows a method for producing a BGA using the solder balls of the present invention.

FIG. 4 shows a solder paste using a solder ball having a surface coating according to the present invention.

FIG. 5 shows a Cu-based conductor connection terminal provided with a surface coating of the present invention.

[Explanation of symbols]

1 ... Sn-Zn eutectic solder, 2 ... Au layer 3 ... Solder ball, 4 ... BGA body 5 ... Cu terminal, 6 ... Solder resist 7 ... Flux, 8 ... Bump 9 ... BGA, 10 ... Sn-Z
n eutectic solder 11 ... Sn layer, 12 ... Solder ball 13 ... Flux component, 14 ... Solder paste 15 ... Cu lead, 16 ... Sn-
Zn solder layer 17 ... Ag layer, 18 ... Connection terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiharu Ishida, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd., Institute of Industrial Science, Hitachi, Ltd. No. 1 stock company Hitachi Ltd. semiconductor division

Claims (19)

[Claims] 1. Sn-Zn or Sn-Zn-Bi,
Alternatively, a Sn—Zn-based or Sn—Zn— characterized by having a metal layer on the surface of a solder containing any one or more of In, Ag, Sb, and Cu in these.
Bi solder. 2. Sn-Zn or Sn-Zn-Bi,
Alternatively, it is possible to reduce the amount of Au of 0..A on the surface of the solder containing any one or more of In, Ag, Sb and Cu.
Sn- characterized by having a coating layer of 01 μm or more
Zn-based or Sn-Zn-Bi-based solder. 3. Sn-Zn or Sn-Zn-Bi,
Alternatively, the surface of the solder containing any one or more of In, Ag, Sb, and Cu may have a coating layer of 2 μm or more of Sn or an Sn alloy such as Sn—Bi. Zn-based or Sn-Zn-
Bi solder. 4. Sn-Zn or Sn-Zn-Bi,
Alternatively, a Sn-Zn system or Sn characterized by having a coating layer of 0.01 μm or more of Ni or Cu on the surface of a solder containing any one or more of In, Ag, Sb and Cu. -Zn-Bi based solder. 5. Sn-Zn or Sn-Zn-Bi,
Alternatively, Pd of 0..Pd on the surface of the solder containing any one or more of In, Ag, Sb, and Cu in these.
Sn- characterized by having a coating layer of 01 μm or more
Zn-based or Sn-Zn-Bi-based solder. 6. Sn-Zn or Sn-Zn-Bi,
Alternatively, it is possible to reduce the Ag content of 0..A on the surface of the solder containing any one or more of In, Ag, Sb, and Cu.
Sn- characterized by having a coating layer of 01 μm or more
Zn-based or Sn-Zn-Bi-based solder. 7. Sn-Zn or Sn-Zn-Bi,
Alternatively, the surface of the solder containing any one or two or more of In, Ag, Sb and Cu has a metal coating step, Sn—Zn system or Sn.
-Zn-Bi solder surface treatment method. 8. Sn-Zn or Sn-Zn-Bi,
Alternatively, Au on the surface of the solder containing any one or more of In, Ag, Sb, and Cu may be added to 0.
S characterized by having a step of covering at least 01 μm
Surface treatment method for n-Zn-based or Sn-Zn-Bi-based solder. 9. Sn-Zn or Sn-Zn-Bi,
Alternatively, there is provided a step of coating the surface of a solder containing any one or more of In, Ag, Sb, and Cu with Sn or Sn alloy such as Sn-Bi in an amount of 2 μm or more. Zn-based or Sn-Z
Surface treatment method for n-Bi solder. 10. Sn-Zn or Sn-Zn-B
i, or a Sn—Zn system characterized by having a step of coating the surface of a solder containing any one or more of In, Ag, Sb, and Cu with 0.01 μm or more of Ni or Cu. Or Sn-Zn-Bi
Surface soldering method. 11. Sn-Zn or Sn-Zn-B
i, or a Sn—Zn-based or Sn-based solder having a step of coating Pd on the surface of a solder containing any one or more of In, Ag, Sb, and Cu in 0.01 μm or more. -Zn-Bi solder surface treatment method. 12. Sn-Zn or Sn-Zn-B
i, or a Sn-Zn-based or Sn-based solder having a step of coating Ag on a surface of a solder containing any one or more of In, Ag, Sb, and Cu with 0.01 μm or more. -Zn-Bi solder surface treatment method. 13. A Sn-Zn-based or Sn-Zn-Bi-based solder wire, and a mount using the same, wherein the solder according to any one of claims 1 to 6 is a solder wire. 14. A Sn—Zn based or Sn—Zn—Bi based solder ball, wherein the solder according to any one of claims 1 to 6 is spherical. 15. A solder paste comprising the Sn—Zn-based or Sn—Zn—Bi-based solder ball according to claim 14, and a packaged product using the same. 16. A BGA (ball grid array) using the Sn—Zn-based or Sn—Zn—Bi-based solder ball according to claim 14 as an electrical connecting member. 17. The Sn-Zn-based or Sn-Zn-Bi-based solder ball according to claim 14 is arranged in an electronic component,
Mounted product characterized by connecting this to a circuit board. 18. An Sn-Zn system or Sn-Z is formed on the surface of a conductor such as Cu or Ni of a connection terminal portion of an electronic component or a substrate.
An n-Bi solder is coated, and the surface is coated with the solder.
A mounting method using the electronic component or substrate that has been subjected to the surface treatment as described above. 19. Sn-Zn-B according to any one of claims 1 to 18.
In i-based solder, the composition is 4 mass% ≦ Zn ≦ 6 mass%,
A Sn-Zn-Bi solder characterized by 12 mass% ≤ Bi ≤ 19 mass% and the remaining Sn, a surface treatment method thereof, and a mounted product using the same.