WO2014207897A1 - Solder material and solder joint - Google Patents

Abstract

　The purpose of the present invention is to provide a solder material in which the amount of radiated α-rays can be reduced. A solder ball (1A), which is a solder material, is provided with a nuclei layer (2A) having sufficient diameter to maintain distance between a bonding object and a bonded object, and a solder layer (3A) coating the nuclei layer (2A). The solder layer (3A) is configured from a metal material that: has a melting point at a temperature at which the nuclei layer (2A) does not melt, the metal material solidifying and thereby bonding the bonding object and the bonded object to each other; and has sufficient thickness to block α-rays radiated from the nuclei layer (2A).

Description

Solder material and solder joint

The present invention relates to a solder material and a solder joint formed by using a solder material capable of suppressing radiation, particularly radiation dose of α rays.

In recent years, due to miniaturization of information equipment, electronic components mounted on information equipment are also rapidly downsized. In order to meet the demand for downsizing and the reduction of the connection terminals and the reduction of the mounting area, electronic components are applied with a ball grid array (hereinafter referred to as BGA) in which electrodes are installed on the back surface.

An electronic component to which BGA is applied includes, for example, a semiconductor package. In a semiconductor package, a semiconductor chip having electrodes is sealed with a resin. Solder bumps are formed on the electrodes of the semiconductor chip. This solder bump is formed by joining a solder ball to an electrode of a semiconductor chip. A semiconductor package using BGA is placed on a printed circuit board so that each solder bump comes into contact with the conductive land of the printed circuit board. The Further, in order to meet the demand for further high-density mounting, three-dimensional high-density mounting in which semiconductor packages are stacked in the height direction has been studied.

However, when BGA is applied to a semiconductor package on which three-dimensional high-density mounting is performed, the solder balls are crushed by the weight of the semiconductor package, and a connection short circuit occurs between the electrodes. This hinders high-density mounting.

Therefore, a solder bump in which a Cu ball is bonded to an electrode of an electronic component with a paste has been studied (for example, see Patent Document 1). A solder bump having a Cu ball can support the semiconductor package with a Cu ball that does not melt at the melting point of the solder even when the weight of the semiconductor package is added to the solder bump when an electronic component is mounted on a printed circuit board. Therefore, the solder hump is not crushed by the weight of the semiconductor package.

By the way, miniaturization of electronic components enables high-density mounting, but high-density mounting of electronic components causes a problem of soft errors. The soft error is that the stored content may be rewritten when alpha rays, which are radiations, enter memory cells of a semiconductor integrated circuit (hereinafter referred to as IC). It is considered that α rays are emitted when a radioactive element such as U, Th, ²¹⁰ Po, etc. in the solder alloy undergoes α decay. Therefore, in recent years, development of low α-ray solder materials in which the content of radioactive elements is reduced has been carried out.

International Publication No. 95/24113

In solder bumps having Cu balls, the refining of Cu goes through a process of heating Cu to about 1000 ° C., so that a radioactive element such as ²¹⁰ Po that emits α rays can be volatilized, and the emitted α dose is It is thought that it can be kept low. It is also conceivable to use a Cu ball having a high purity that does not contain an element involved in the emission of α rays.

However, conventional refining of metals such as Cu does not take into consideration that elements involved in the emission of α rays can be removed by volatilization. In addition, the use of high purity metal leads to an increase in cost. Furthermore, when a material with a low emitted α dose is used, there are restrictions on the materials that can be used.

The present invention has been made to solve such a problem, and provides a solder material capable of suppressing the radiation dose of radiation, particularly alpha rays, and a solder joint formed using the solder material. With the goal.

The inventors coated the material that becomes the core layer with a material whose α dose is lower than the allowable value of the α dose radiated from the solder material. It was found that radiation of lines can be suppressed.

The present invention includes a core layer having a size that secures a gap between a bonded object and an object to be bonded, and a coating layer that covers the core layer, and the coating layer has a temperature at which the core layer is not melted. In addition to joining the object to be joined and the object to be joined by solidifying, the core layer, either the functional layer provided inside the coating layer and the core layer provided inside the functional layer, Or it is a solder material comprised with the metal material which has the thickness which shields the radiation radiated | emitted from both a nucleus layer and a functional layer. Moreover, this invention is the solder joint formed using this solder material.

In the present invention, the coating layer has a melting point that melts at a temperature at which the core layer is not melted, and solidifies Sn alone, an alloy material containing Sn, or Pb that joins the joined object and the object to be joined. It is preferably composed of any one of an alloy material containing Sn, a simple substance of In, and an alloy material containing In.

In the present invention, as an alloy material containing Sn, Sn and one or more of Cu, Ni, Ag, Bi, Pb, Al, Fe, Zn, In, Ge, Ga, Sb, and Co are contained. It is preferable that the coating layer is made of an alloy that is used.

Further, in the present invention, the core layer is Cu, Ni, Ag, Bi, Pb, Al, Sn, Fe, Zn, In, Ge, Sb, Co having a melting point that is not melted at the temperature at which the coating layer melts. Mn, Au, Si, Pt, Cr, La, Mo, Nb, Pd, Ti, Zr, and Mg are preferably composed of a single metal, a metal oxide, a metal mixed oxide, or an alloy.

The core layer is preferably composed of a resin material, a carbon material, or a ceramic that is not melted at a temperature at which the coating layer melts.

Furthermore, the coating layer shields α rays radiated from either the core layer, the core layer and the functional layer, or both the core layer and the functional layer, and the α dose transmitted through the coating layer is 0.0200 cph / cm. It is preferably made of a metal material having a thickness of ² or less and an α dose emitted from the coating layer of 0.0200 cph / cm ² or less. Further, the α dose emitted from the coating layer is preferably 0.0020 cph / cm ² or less, more preferably 0.0010 cph / cm ² or less, from the viewpoint of suppressing soft errors in further high-density mounting. Furthermore, the thickness of the coating layer is preferably 1 μm or more and 1000 μm or less.

In the present invention, the α-ray, which is the radiation emitted from the coating layer itself, is less than or equal to the allowable value of the α dose emitted from the solder material, and the coating layer is provided inside the core layer and the coating layer. And a thickness that can block α-rays radiated from either the core layer provided inside the functional layer or both the core layer and the functional layer.

Thus, in the present invention, the α dose emitted from the solder material can be suppressed to a predetermined allowable value or less, and the occurrence of soft errors due to α rays can be suppressed. In addition, materials that have previously been difficult to reduce the α dose can be used as a nucleus layer with a configuration that suppresses the occurrence of soft errors due to α rays, and the range of selection of materials that constitute the nucleus layer Can be spread.

It is sectional drawing which shows an example of the solder ball of this Embodiment. It is sectional drawing which shows an example of the solder joint which is the use condition of the solder ball of this Embodiment. It is sectional drawing which shows the modification of the solder ball of this Embodiment. It is sectional drawing which shows the other modification of the solder material of this invention.

<Configuration Example of Solder Ball of this Embodiment>
FIG. 1 is a cross-sectional view showing an example of a solder ball according to the present embodiment, and FIG. 2 is a cross-sectional view showing an example of a solder joint in a use state of the solder ball according to the present embodiment. As an embodiment, a solder ball will be described as an example.

As shown in FIG. 1, the solder ball 1A of the present embodiment includes a spherical core layer 2A having a desired diameter and a solder layer 3A covering the core layer 2A. As shown in FIG. 2, the solder joint 12 </ b> A is disposed between the electrode 10 a of the semiconductor chip 10 that is a bonded object and the conductive land 11 a of the printed circuit board 11 that is a bonded object.

In the solder ball 1A, the solder layer 3A constituting the outermost layer is melted by heating, and the molten solder layer 3A is solidified to form a solder joint 12A, thereby joining the electrode 10a and the conductive land 11a. The solder joint 12 </ b> A is a core layer 2 </ b> A covered with the solder layer 3 </ b> A, and ensures a gap between the semiconductor chip 10 and the printed board 11.

The core layer 2A is made of a metal material or a resin material having a melting point Tm2 (Tm2> Tm1) that is not melted at the melting point Tm1 of the solder layer 3A. When a metal material is selected as the core layer 2A, examples of the metal material having a melting point Tm2 higher than the melting point Tm1 of the solder layer 3A include Cu, Ni, Ag, Bi, Pb, Al, Sn, Fe, Zn, Consists of simple metals such as In, Ge, Sb, Co, Mn, Au, Si, Pt, Cr, La, Mo, Nb, Pd, Ti, Zr, Mg, metal oxides, metal mixed oxides, or alloys The Further, the core layer 2A may add P or the like as an additive element to these metal materials described above.

The core layer 2A is interposed between the electrode 10a and the conductive land 11a in a state where the core layer 2A is covered with the solder layer 3A obtained by bonding the electrode 10a of the semiconductor chip 10 and the conductive land 11a of the printed board 11. It has a diameter that secures an interval between the semiconductor chip 10 and the printed circuit board 11.

The solder layer 3A is an example of a coating layer, and is made of a metal material having a melting point Tm1 lower than the melting point Tm2 of the core layer 2A. The solder layer 3A is melted and solidified by heating at a temperature equal to or higher than the melting point Tm1 of the solder layer 3A itself and lower than the melting point Tm2 of the core layer 2A, so that the electrode 10a of the semiconductor chip 10 and the printed circuit board 11 are solidified. The conductive land 11a is joined.

Further, the solder layer 3A is made of a metal material in which the α rays emitted from the solder layer 3A itself are less than a predetermined value in order to suppress the emission of α rays that are radiation emitted from the solder ball 1A and the solder joint 12A. . Furthermore, the solder layer 3A has a thickness capable of shielding α rays emitted from the core layer 2A and suppressing the α dose emitted from the solder balls 1A and the solder joints 12A to a predetermined allowable value or less.

The solder layer 3A is composed of, for example, Sn alone, Sn-based alloy material, Sn-based alloy material not containing Pb, In-alone, or In-based alloy material as a metal material that satisfies the above-described conditions. . The solder layer 3A is made of Sn—Ag—Cu, Sn—Ag, Sn—Cu, Sn—Bi, Sn—In, Sn—Pb, or the like as an Sn-based alloy material. The solder layer 3A is made of an alloy obtained by adding other elements to the above-described alloys. The solder layer 3A is made of the desired metal material described above, and is formed by forming a layer by plating on the surface of the core layer 2A.

In the solder ball 1A and the solder joint 12A, the α dose As2 emitted from the core layer 2A and the α emitted from the solder layer 3A with respect to the allowable value As1 of the α dose emitted from the solder ball 1A and the solder joint 12A. If the dose As3 is lower than the allowable value As1, the α dose radiated from the solder ball 1A and the solder joint 12A can be suppressed to the allowable value As1 or less.

On the other hand, even if the α dose As2 emitted from the core layer 2A is larger than the allowable value As1 of the α dose emitted from the solder ball 1A and the solder joint 12A, the α rays emitted from the core layer 2A are generated by the solder layer 3A. By shielding, the α dose emitted from the solder ball 1A and the solder joint 12A can be suppressed to an allowable value As1 or less.

Therefore, the solder layer 3A is made of a metal material in which the α dose As3 emitted from the solder layer 3A itself is equal to or less than the allowable value As1 of the α dose emitted from the solder ball 1A and the solder joint 12A.

Also, the solder layer 3A is emitted from the core layer 2A even when the α dose As2 emitted from the core layer 2A is larger than the allowable value As1 of the α dose emitted from the solder ball 1A and the solder joint 12A. By shielding the α rays, the α dose emitted from the solder balls 1A and the solder joints 12A can be reduced to the allowable value As1.

Here, by melting and solidifying the solder layer 3A, the electrode 10a of the semiconductor chip 10 and the conductive land 11a of the printed circuit board 11 can be joined, and even after solidification, the core layer 2A is covered. The thickness is such that the α rays emitted from the core layer 2A can be shielded.

In addition, when the solidified solder layer 3A is thickened, the effect of shielding α rays emitted from the core layer 2A is improved, while the distance between the semiconductor chip 10 and the printed board 11 is affected. For this reason, the solder layer 3A has a thickness that can secure the space between the semiconductor chip 10 and the printed board 11 by the core layer 2A covered with the solidified solder layer 3A.

In the solder ball 1A and the solder joint 12A in which the core layer 2A is coated with the solder layer 3A, the α rays radiated from the solder layer 3A itself are below the allowable value of the α dose radiated from the solder ball 1A and the solder joint 12A. In addition, the solder layer 3A has a thickness capable of shielding α rays emitted from the core layer 2A and suppressing the α dose emitted from the solder balls 1A and the solder joints 12A to a predetermined allowable value or less. If so, it is possible to suppress the occurrence of soft errors due to α rays. Further, the range of selection of materials that can be used as the nucleus layer can be expanded.

This makes it possible to provide the solder ball 1A having desired characteristics, such as being able to suppress the emission of α-rays and ensuring the interval between the bonded object and the bonded object at low cost.

<Modified example of solder ball of this embodiment>
FIG. 3 is a cross-sectional view showing a modification of the solder ball of the present embodiment. A solder ball 1B according to a modification of the present embodiment includes a spherical core layer 2B having a desired diameter, one or more functional layers 4B covering the core layer 2B, and the core layer 2B and the functional layer 4B. The solder layer 3B is provided.

The core layer 2B is composed of a metal material or a resin material having a melting point that is not melted at the melting point of the solder layer 3B, similarly to the core layer 2A. If the core layer 2B is a metal material, for example, Cu, Ni, Ag, Bi, Pb, Al, Sn, Fe, Zn, In, Ge, Sb, Co, Mn, Au, Si, Pt, Cr, La , Mo, Nb, Pd, Ti, Zr, Mg and other simple metals, metal oxides, mixed metal oxides, or alloys, or any of these metal materials plus P as an additive element .

The functional layer 4B is made of a metal material or a resin material having a melting point that is not melted at the melting point of the solder layer 3B. The functional layer 4B is configured by providing, for example, a Ni plating layer on the surface of the core layer 2B. Note that when a resin material is selected as the core layer, a base plating layer made of Ni or the like is indispensable for forming a solder layer as usual.

The solder layer 3B is an example of a coating layer, and is composed of a metal material having a melting point lower than that of the core layer 2B and the functional layer 4B. The solder layer 3B is melted and solidified by heating at a temperature higher than the melting point of the solder layer 3B itself and lower than the melting point of the core layer 2B and the functional layer 4B. To do.

Also, the solder layer 3B is made of a metal material in which the α rays emitted from the solder layer 3B itself are less than a predetermined value in order to suppress the emission of α rays that are radiation emitted from the solder balls 1B. Further, the solder layer 3B shields the α rays emitted from the core layer 2B or the functional layer 4B, or the core layer 2B and the functional layer 4B, and the α dose emitted from the solder ball 1B is below a predetermined allowable value. It has a thickness that can be suppressed.

The solder layer 3B is, for example, Sn—Ag—Cu, Sn—Ag, Sn—Cu, Sn—Bi, Sn—In, Sn—Pb, etc. It is comprised with the alloy which added these elements.

In the solder ball 1B, by providing a plated layer of Ni as the functional layer 4B on the surface of the core layer 2B, a uniform solder layer 3B is formed on the surface of the core layer 2B in the step of forming the solder layer 3B by plating. be able to.

Here, even if the α dose emitted from the nucleus layer 2B or the functional layer 4B, or the nucleus layer 2B and the functional layer 4B is larger than the allowable value of the α dose emitted from the solder ball 1B, the nucleus layer 2B or the function By shielding α rays emitted from the layer 4B or the core layer 2B and the functional layer 4B with the solder layer 3B, the α dose emitted from the solder balls 1B can be suppressed to an allowable value or less.

Therefore, the solder layer 3B is made of a metal material in which the α dose emitted from the solder layer 3B itself is less than the allowable value of the α dose emitted from the solder ball 1B.

The solder layer 3B has a case where the α dose emitted from the core layer 2B or the functional layer 4B or the core layer 2B and the functional layer 4B is larger than the allowable value of the α dose emitted from the solder ball 1B. However, by blocking the α-rays radiated from the core layer 2B or the functional layer 4B, or from the core layer 2B and the functional layer 4B, the α dose emitted from the solder ball 1B can be suppressed to an allowable value. Consists of.

In the solder ball 1B of the modified example, in addition to the core layer 2B and the solder layer 3B, a predetermined functional layer 4B is provided inside the solder layer 3B to have a multilayer structure. In the solder ball 1B having such a multilayer structure, even when the α dose emitted from the functional layer 4B is larger than the allowable value of the α dose emitted from the solder ball 1B, the α emitted from the functional layer 4B. The wire can be shielded by the solder layer 3B, and restrictions on the material that can be used as the functional layer can be reduced.

Further, if the α dose emitted from the functional layer 4B is smaller than the allowable value of the α dose emitted from the solder ball 1B, the α rays emitted from the core layer 2B are converted into the functional layer 4B and the solder layer 3B. Can be shielded.

As described above, in the solder ball 1B having the multilayer structure, the α ray emitted from the solder layer 3B itself is less than the allowable value of the α dose emitted from the solder ball 1B, and the solder layer 3B is the core layer 2B or A structure having a thickness capable of shielding α rays emitted from the functional layer 4B or the core layer 2B and the functional layer 4B and suppressing the α dose emitted from the solder balls 1B to a predetermined allowable value or less. Then, it is possible to suppress the occurrence of soft errors due to α rays. Moreover, the range of selection of the material which can be used as a nucleus layer and a functional layer can be expanded.

This makes it possible to provide solder balls 1B having desired characteristics, such as low radiation of α-rays and ensuring a space between the object to be bonded and the object to be bonded, at a low cost.

<Other Variations of Solder Material of the Present Invention>
FIG. 4 is a cross-sectional view showing another modification of the solder material of the present invention. In each of the above-described embodiments, a spherical solder ball has been described as an example of the solder material. However, as shown in FIG. The solder material 1 </ b> C may be configured as a shape that is covered with the functional layer 4 </ b> B and the solder layer 3 </ b> B that are equal to or more than one layer. Moreover, it is good also as a structure which does not provide the functional layer 4B.

In addition, when the solder material of the present invention is used as a spherical solder ball, the diameter of the solder ball is preferably 1 to 1000 μm. Within this range, spherical solder balls can be stably manufactured, and connection short-circuiting when the terminals are at a narrow pitch can be suppressed.

Here, for example, when the diameter of the solder ball according to the present invention is about 1 to 300 μm, the assembly of “solder balls” may be referred to as “solder powder”. Here, the “solder powder” is an aggregate of a large number of solder balls, each of which has the above-mentioned characteristics. For example, it is distinguished in the form of use from a single solder ball, such as being formulated as a powder in solder paste. Similarly, when used for the formation of solder bumps, it is normally treated as an assembly, so the “solder powder” used in such a form is distinguished from a single solder ball.

Using 30 ppmAg as the core layer 2A to form a spherical shape of Ag30ppm-Bi and Sn100% as the solder layer 3A, the solder ball 1A of the example was prepared by varying the thickness of the solder layer 3A. The α dose emitted from 1A was measured. As a comparative example, the α dose emitted from the core layer 2A without the solder layer 3A was measured.

First, with respect to the method for producing the solder ball 1A used in the example, a case where an Ag30ppm-Bi ball is used as the core layer 2A according to the present invention and the solder layer 3A is formed using a barrel plating method to form the solder ball 1A. Explained as an example.

As the core layer 2A according to the present invention, a spherical Ag 30 ppm-Bi ball formed by a known atomizing method or the like was used. A case where barrel plating is used as an example of the method for forming the solder layer 3A according to the present invention on the prepared Ag30ppm-Bi ball will be described below.

The solder plating solution was prepared as follows. 1/3 of the water required for adjusting the plating solution and the total volume of 54% by weight methanesulfonic acid aqueous solution were placed in the stirring vessel as the groundwater. Next, acetylcysteine, which is an example of a mercaptan compound as a complexing agent, was added and confirmed for dissolution, and 2,2'-dithiodianiline, which was an example of an aromatic amino compound as another complexing agent, was then added. When it became a light blue gel-like liquid, stannous methanesulfonate was quickly added. Next, 2/3 of the necessary water was added to the plating solution, and finally α-naphthol polyethoxylate (EO 10 mol) 3 g / L as an example of a surfactant was added, and the preparation of the plating solution was completed. A plating solution having a methanesulfonic acid concentration of 2.64 mol / L and a tin ion concentration of 0.337 mol / L in the plating solution was prepared.

In Example 1, Example 2, and Comparative Example, the diameter of the core layer 2A was 350 μm. In Example 1, the thickness of the solder layer 3A was 10 μm. In Example 1, by setting the thickness of the solder layer 3A to 10 μm, the diameter of the solder ball 1A becomes 370 μm. In Example 2, the thickness of the solder layer 3A was 30 μm. In Example 2, the diameter of the solder ball 1A is 410 μm by setting the thickness of the solder layer 3A to 30 μm.

When an Sn solder plating film having a film thickness (one side) of 10 μm is formed on an Ag30ppm-Bi ball having a diameter of 350 μm shown in Example 1 of the present invention, an electric quantity of about 0.048 coulomb is required.

In addition, when an Sn solder plating film having a film thickness (one side) of 30 μm is formed on an Ag30ppm-Bi ball having a diameter of 350 μm shown in Example 2 of the present invention, an amount of electricity of about 0.16 coulomb is required.

The amount of electricity is calculated by the following formula (1) according to Faraday's law of electrolysis, the desired amount of solder plating is estimated, the amount of electricity is calculated, and a current is passed through the plating solution so that the calculated amount of electricity is obtained. Then, the plating process is performed while flowing the plating solution. The capacity of the plating tank can be determined according to the total amount of Ag-Bi balls and plating solution.

W (g) = (I × t × M) / (Z × F) (1)

In formula (1), w is the amount of electrolytic deposition (g), I is the current (A), t is the energization time (seconds), M is the atomic weight of the deposited element (in the case of Sn, 118.71), and Z is the valence. (Sn is bivalent), F is a Faraday constant (96500 coulombs), and the quantity of electricity Q (A · sec) is represented by (I × t).

The α ray was measured with a gas flow type apparatus based on JEDEC. The sample used was stored in PR gas for 24 hours, the sample area was 900 cm ² , and the measurement time was 72 hours. The first 10 hours are not used for measurement because of an error in the α dose in the air.

The measurement results of α dose are shown in Table 1.

As shown in the comparative example in Table 1, the α dose emitted from the core layer 2A not provided with the solder layer 3A was 0.0898 cph / cm ² . On the other hand, in Example 1 in which the thickness of the solder layer 3A covering the core layer 2A was 10 μm, the α dose emitted from the solder ball 1A was 0.0160 cph / cm ² . Further, in Example 2 in which the thickness of the solder layer 3A covering the core layer 2A was 30 μm, the α dose emitted from the solder ball 1A was 0.0107 cph / cm ² .

From the above measurement results, it was found that the α dose emitted from the solder ball 1A is reduced by covering the core layer 2A with the solder layer 3A. It was found that the α dose emitted from the solder ball 1A tends to decrease by increasing the thickness of the solder layer 3A.

When the allowable value As1 of the α dose emitted from the solder ball 1A is about 0.0200 cph / cm ² , the α dose As2 emitted from the core layer 2A is more than the allowable value As1 of the α dose emitted from the solder ball 1A. Even if it is large, the alpha dose emitted from the solder ball 1A can be suppressed to the allowable value As1 (0.0200cph / cm ² ) or less by covering the core layer 2A with the solder layer 3A having a thickness of 10 μm or more. I understood.

The present invention is applied to solder balls used for mounting electronic parts to which BGA is applied.

1A, 1B ... Solder balls, 2A, 2B ... Core layer, 3A, 3B ... Solder layer, 4B ... Functional layer

Claims (9)

A nucleus layer having a size that secures a gap between the bonded object and the bonded object;
A coating layer covering the core layer,
The covering layer has a melting point that melts at a temperature at which the core layer is not melted, and solidifies to join the joined article and the article to be joined. The α dose that has passed through the coating layer by shielding the α-rays radiated from either the functional layer provided and the core layer provided inside the functional layer, or both the core layer and the functional layer A solder material characterized by comprising a metal material having a thickness of 0.0200 cph / cm ² or less and an α dose emitted from the coating layer of 0.0200 cph / cm ² or less. The coating layer has a melting point that melts at a temperature at which the core layer is not melted, and solidifies Sn alone, an alloy material containing Sn, or Pb to solidify the bonded object and the bonded object. 2. The solder material according to claim 1, wherein the solder material is composed of any one of an alloy material containing Sn that is not contained, an In simple substance, and an alloy material containing In. The coating layer contains Sn and one or more of Sn, Cu, Ni, Ag, Bi, Pb, Al, Fe, Zn, In, Ge, Ga, Sb, and Co as an alloy material containing Sn. It is comprised with an alloy. The solder material of Claim 2 characterized by the above-mentioned. The core layer has Cu, Ni, Ag, Bi, Pb, Al, Sn, Fe, Zn, In, Ge, Sb, Co, Mn, Au having a melting point that is not melted at a temperature at which the coating layer melts. 1 to Claims, characterized in that it is composed of a single metal, a metal oxide, a mixed metal oxide, or an alloy of Si, Pt, Cr, La, Mo, Nb, Pd, Ti, Zr, and Mg. 4. The solder material according to any one of 3 above. The solder material according to any one of claims 1 to 3, wherein the core layer is made of a resin material that is not melted at a temperature at which the coating layer melts. The solder material according to any one of claims 1 to 5, wherein the coating layer has a thickness of 1 um to 1000 um. The solder material according to any one of claims 1 to 6, wherein an α dose emitted from the coating layer is 0.0020 cph / cm ² or less. The solder material according to any one of claims 1 to 6, wherein an α dose emitted from the coating layer is 0.0010 cph / cm ² or less. A solder joint formed by using the solder material according to any one of claims 1 to 8.

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