JPH09266373A - Electronic component its bonding method and circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make thin enough an Sn-Pd reaction layer formed by bonding and ensure a high bond strength, even if using Sn-Bi solder by covering leads to be electrically soldered to desired parts with specified thin Pd film layer. SOLUTION: Electronic components 18 having leads 14 covered with a Pd plated layer 16 are bonded to an interconnection 12 on a circuit board 10, using Sn-Bi solder 20, resulting in a reaction of the solder with the plated layer 16 at the interface between the solder 20 and leads 14 to form a Sn-Pd alloy layer 22. To improve the bond strength, the Sn-Pd reaction layer 22 must be thin, and hence a Pd film of less than 75nm thick is pref. used for covering the surface of the leads of the components. If such electronic components 18 are bonded to the circuit board 10, a good bond strength can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for joining electronic components using Sn-Bi solder, and more particularly to Sn-B.
The present invention relates to an electronic component having a structure suitable for soldering using i-based solder, a joining method thereof, and a circuit board on which the electronic component is mounted.

[0002]

2. Description of the Related Art Conventionally, as a solder, Sn (tin)-
A Pb (lead) alloy is generally known and has been used as a bonding material for various mounting methods to date. For example, in mounting by the DIP method, the QFP method, and the LCC method, a solder having a eutectic composition of 63 wt% Sn-37 wt% Pb and a melting point of 183 ° C. is used, and this is about 220
By heating at a temperature of ° C, the leads and electrodes of the electronic component are bonded onto the Cu (copper) electrodes on the printed board.

However, Sn-Pb-based solder causes a soft error due to the emission of α rays from Pb, which is the main component, and the printed circuit board after disposal is exposed to acid rain to elute Pb, Due to adverse effects such as polluting rivers and groundwater, there are active moves to regulate the use. Further, Sn-Pb-based solder has a melting point of 183 ° C even in 63Sn-37Pb, which has the lowest melting temperature, and requires a temperature of about 210 to 220 ° C for solder joining. Therefore, electronic components having low heat resistance could not be collectively joined by reflow.

From such a background, a solder alloy for low temperature bonding which does not contain Pb as a constituent element has been actively developed, and various solders have been proposed. For example, 52In-48
Sn (melting point 117 ° C.), 57Bi-43Sn (melting point 13
9 ° C.), 91Sn-9Zn (melting point 199 ° C.), 96.5
Based on an Sn-based eutectic solder alloy such as Sn-3.5Ag (melting point 221 ° C.), attempts have been made to add a small amount of third and fourth elements for adjusting the melting point and improving mechanical properties. Has been done.

The inventors of the present application have proposed that by adding a predetermined amount of Ag (silver) as a third element to a Sn-Bi alloy, the mechanical properties can be improved without raising the melting point, and Japanese Patent Application No. 7-59334. It is disclosed in the specification. On the other hand, as leads for electronic parts, Cu leads, Fe
Materials such as an alloy of (iron) -58 wt% and Ni (nickel) -42 wt% (hereinafter referred to as 42 alloy), Kovar, etc. are used. These leads are surface-coated in order to improve the corrosion resistance and obtain a good joint with the solder.

63Sn-37Pb solder occupies most of the current solders for electronics, and the pre-solder with Sn-Pb type solder occupies most of the surface coating treatment of leads. Therefore, it is desirable to promote the so-called Pb-free use of the lead surface coating material without using Pb. As a Pb-free surface coating material that does not use Pb, Pd is used as a surface coating material for the lead portion.
Electronic parts using (palladium) are already on the market. The electronic component using Pd plating has the advantage that it is compatible with Pb-free and that cost reduction can be achieved by plating the lead before assembling the electronic component.

[0007]

However, the electronic component 18 in which the surface of the lead 14 is coated with the above-mentioned 63Sn-37Pb solder 38 of the related art is replaced with 42Sn-5.
S such as 8Bi and 41.6Sn-57.4Bi-1Ag
When the n-Bi-based solder 20 is used for joining, the alloying reaction of the joining portion causes 15.5Sn-32Pb-52.5B.
A ternary eutectic reaction of i had occurred (Fig. 7). Since such a ternary eutectic alloy 40 has a low melting point of about 95 ° C., the joint part is not formed during a thermal shock test (125 ° C.) for confirming reliability or when an electronic component that generates a great amount of heat is joined. It sometimes melted.

[0008] Further, when the electronic parts whose surface coating treatment is performed on the leads by Pd plating are bonded using the same Sn-Bi solder paste, the bonding strength is higher than that when mounted using 63Sn-37Pb solder. It was falling. An object of the present invention is to provide an electronic component having a surface coating treatment suitable for Sn-Bi solder, a method for joining the electronic component, and a circuit board on which the electronic component is mounted.

[0009]

The above object is to provide an electronic component in which a lead portion for electrically soldering to a joined portion is covered with a coating layer made of a Pd film thinner than 75 nm. Achieved by As a result, the thickness of the Sn-Pd reaction layer formed by bonding can be made sufficiently thin, so that high bonding strength can be obtained even when Sn-Bi solder is used.

An electronic component to be joined to a joined portion by using Sn—Bi solder, a lead portion for joining to the joined portion, and a Cu layer or a Ni layer covering the lead portion. And a second layer covering the first layer
And a coating layer having a layer of No. 2, and when the lead portion is joined to the joined portion, the first layer and the Sn-B
It is also achieved by an electronic component characterized by joining with an i-based solder. Thereby, the high bonding strength obtained between the Sn-Bi solder and the Ni layer or the Cu layer can be sufficiently exhibited.

In the above electronic component, the second
It is desirable that the layer of (1) be composed of a material that is dispersed in the Sn-Bi solder during joining. This makes it possible to obtain high joint strength after joining between the lead portion and the Sn-Bi solder. Further, in the above electronic component, the second layer is preferably an Au layer.

Further, in the above electronic component, the second
The layer is preferably made of a metal material having a melting point close to that of the Sn-Bi solder. This makes it possible to obtain high joint strength after joining between the lead portion and the Sn-Bi solder. Further, in the above electronic component, the second layer is preferably a Sn layer or a Sn-Bi layer.

Further, in the above electronic component, the first
The layer is preferably 0.5 μm or more in thickness.
By setting the film thickness in this way, the Ni layer or Cu
The layers do not completely react during bonding, and Sn is
-A bond between the Bi-based solder and the Ni layer or the Cu layer can be formed. Further, the present invention can also be achieved by a circuit board characterized in that an electrode portion for electrically connecting electronic components is covered with the coating layer. As a result, it is possible to configure a circuit board having high bonding strength even when Sn—Bi solder is used.

Further, it is also achieved by a circuit board characterized in that the above-mentioned electronic component is joined to the electrode portion by Sn—Bi solder. As a result, the reliability of joining the electronic components can be increased, and thus the reliability of the circuit board on which the electronic components are mounted can also be increased. Further, it is also achieved by the above-described electronic component joining method, which is characterized in that the electronic component is joined to the joined portion using Sn—Bi solder. As a result, it is possible to join with the joined portion with high joining strength.

Further, in the above-described method for joining electronic components, the Sn-Bi solder has a Sn composition of 40 to 6
0 wt%, Ag composition is 0 to 2 wt%, B
It is desirable that i consist of the rest of the composition. Thus S
If n-Bi solder is selected, solder having a low melting point and high mechanical strength can be used for bonding with high bonding strength.

[0016]

1 and 2 show an electronic component and a method for joining the electronic component and a circuit board according to a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a diagram for explaining a reaction mode with a lead of an electronic component when Sn—Bi solder is used, and FIG. 2 shows a thickness and a bonding strength of a Pd plating layer when the solder is bonded using 42Sn-58Bi solder. It is a graph which shows a relationship.

The present embodiment shows an electronic component that can be joined by Sn—Bi solder without deteriorating the joining strength of the electronic component whose lead surface is coated with Pd, a joining method thereof, and a circuit board. First, Sn-
The reaction pattern with the Pd-plated lead in the case of using the Bi-based solder will be described with reference to FIG.

On the wiring 12 formed on the circuit board 10,
When the electronic component 18 in which the lead 14 is covered with the Pd plating layer 16 is joined using the Sn-Bi solder 20,
At the interface between the n-Bi solder 20 and the lead 14, S
The n-Bi solder 20 reacts with the Pd plating layer 16,
The Sn-Pd alloy layer 22 is formed. Lead 14 and Sn
Since the bonding strength with the -Bi solder 20 depends on the reaction pattern at these interfaces, the reason why the bonding strength deteriorates when the Pd-plated electronic component 18 is bonded with the Sn-Bi solder 20 is as follows. Sn-Pd reaction layer 22
It is thought that it is caused by.

The inventors of the present invention have conducted extensive studies to investigate the cause of this, and as a result, the Sn-Bi solder 2
It became clear for the first time that the thickness of the Sn-Pd reaction layer 22 formed at the interface between 0 and the lead 14 was thicker than that when joined using 63Sn-37Pb.
The Sn-Pd reaction layer 22 formed at the bonding interface has an extremely brittle property because it contains an intermetallic compound. Therefore, it is considered that the joint strength is deteriorated in the case of Sn-Bi solder in which the thickness of the reaction layer formed is thicker than in the case of using Sn-Pb solder.

Therefore, the inventors of the present invention have made Sn formed.
Since it is necessary to thin the Pd reaction layer 22 to improve the bonding strength, the Pd coating the lead 14 is considered.
The plating thickness of the plating layer 16 was further investigated. Regarding the dependency of the bonding strength on the plating thickness of the Pd plating layer 16, 14
As a result of measurement using the SOP of the pin, as shown in FIG. 2, when the plating thickness is 200 nm or more, the bonding strength is about 400.
It was found that the bonding strength was considerably low as g / pin, but the bonding strength gradually increased when the thickness was set to 200 nm or less, and the bonding strength comparable to that of Sn-Pb-based solder was obtained when the plating thickness became thinner than about 75 nm.

Therefore, when the Sn-Bi solder is used, the film thickness of 7 is used as the surface coating material for the lead of the electronic component.
It is desirable to use a Pd film thinner than 5 nm, and if such an electronic component is bonded to a circuit board or the like, good bonding strength can be obtained. As described above, according to the present embodiment, the Pd plating thickness of the lead of the electronic component is made thinner than 75 nm, so that the bonding strength between the lead and the Sn—Bi solder is about the same as when the Sn—Pb solder is used. Can be improved. As a result, the reliability of joining electronic components can be increased, and the reliability of the circuit board on which these electronic components are mounted can also be greatly improved.

In the above embodiment, the Sn-Bi solder has been described, but the present invention can be applied not only to Sn-Bi eutectic solder, but also to solders to which third and fourth elements are added. it can. For example, Ag is added as the third element, Sn is 40 to 60 wt%, Ag is
The bonding strength can be improved even when a solder having a composition of 0 to 2 wt% and Bi of the remainder is used.

The relationship between the Pd plating thickness and the bonding strength of the 41.6Sn-57.4Bi-1Ag solder was measured. As a result, when the Pd plating thickness was 500 nm, the bonding strength was about 500 g / pin. By reducing the thickness to 50 nm, the bonding strength could be improved to about 880 g / pin. Further, the Pd film can be formed by any film forming method such as plating, vapor deposition, and sputtering.

The surface coating treatment by Pd plating can also be formed on the wiring and electrodes of the circuit board. Also in this case, the bonding strength between the Sn—Bi solder and the circuit board can be improved by making the thickness of the Pd plating layer thinner than 75 nm. Further, as the circuit board referred to in the specification of the present application, all boards to which electronic components can be joined by solder, such as a circuit board such as a glass-epoxy board and a flexible board, can be applied.

Next, an electronic component, a method for joining the same, and a circuit board according to a second embodiment of the present invention will be described with reference to FIGS. 3 to 6. 3 and 4 are views showing a method used for measuring the bonding strength in the present embodiment, FIG. 5 is a view for explaining the structure of the electronic component and the bonding method thereof, and a circuit board according to the present embodiment, and FIG. It is a figure explaining the problem when the Au film to be used is thick.

In this embodiment, a structure newly found by the inventors of the present invention is shown as a surface coating capable of obtaining a sufficient bonding strength for Sn-Bi solder. Since the joint strength between the solder and the material to be joined is determined by the combination of the alloy layer formed by both of them, it is necessary to select the material by grasping the reaction mode between the solder and the material to be joined.

Therefore, the inventor of the present application first forms a joint between Sn—Bi solder and pure metal, and after the joint, Sn—
An attempt was made to select a surface coating material that can obtain a sufficiently strong joint strength by contacting with a Bi-based solder. Furthermore, by coating the surface of such a material with a material that has good solderability and does not adversely affect the interface or the solder matrix itself even after joining, we attempted to improve solderability and joint strength. .

First, the results of selecting a material that can obtain a sufficiently strong joint strength by contacting with Sn-Bi solder will be shown. The inventors of the present application prepared a sample by the following procedure and measured the bonding strength in order to measure the bonding strength when various materials were used. First, Cu, Ni, Au, Pd,
Wire 30 made of Pt (platinum) and 42 alloy
Are prepared (FIG. 3A), and the surfaces thereof are covered with the polyimide film 32 (FIG. 3B).

Next, one end of the wire 30 covered with the polyimide film 32 is polished to expose one end of the wire 30 (FIG. 3C). Then, to the exposed wire 30,
2Sn-58Bi solder, or 41.6Sn-57.4
A preliminary solder 34 made of Bi-1Ag solder is formed (FIG. 3D).

After that, the pre-solders 34 of the two wires 30 thus formed are brought into contact with each other and 170
Heat and bond at ℃ (Fig. 3 (e)). Finally, the wires 30 at both ends are pulled to measure the bonding strength (FIG. 3).
(F)). The bond strengths thus measured are summarized in Table 1. Table 1 also shows the result of similar measurement using 63Sn-37Pb solder for comparison.

[0031]

[Table 1] As shown in Table 1, when Ni and Cu are used as the wire material, 42Sn-52Bi is used as the preliminary solder 34.
Even when using solder, 41.6Sn-57.4Bi
Even when -1Ag solder is used, it is about 7-8 [kg / m
m ² ]. This value is 63Sn-
The bonding strength is comparable to the case of using 37Pb solder.

On the other hand, when other wire materials were used, the bonding strength was considerably lowered, and 63Sn-37 was used.
The value was lower than that when Pb solder was used. Therefore, it has been found that Ni or Cu is suitable for the joining using the Sn-Bi solder as the material in contact with the solder after the joining.

When Ni or Cu is used as the coating material, Sn reacts with Sn or Ni or Cu in the solder when the Sn-based solder and Ni or Cu are predominant. However, the amount of plating is required so that a pure Sn layer can exist even when alloyed with. Since the thickness of the alloy layer formed at a normal soldering temperature for both Ni and Cu is about 0.5 μm, it is desirable to set the film thickness of the Ni and Cu plating film to 0.5 μm or more. .

Next, a coating material made of Ni or Cu (first
The following shows the results of selecting a material that is a surface coating material (second layer) that covers the layer (2), has good solderability, and does not adversely affect the interface or the solder matrix itself even after joining. As such a material, it is conceivable to use a material that is dispersed in the solder when it is joined to the solder, such as Au, or a material that has a similar melting point to the solder and has a similar structure, such as Sn.

Therefore, the measurement sample shown in FIG. 4 was prepared in the same manner as the measurement method shown in FIG. The plating layer 3
No. 6 was formed by plating the wire 30 with Au or Sn before forming the preliminary solder 34. As the preliminary solder 34, 41.6Sn-57.4Bi-1Ag solder was used. The results of measuring the bonding strength using this measurement sample are shown in Table 2.

[0036]

[Table 2] As shown in Table 2, in any sample, 63Sn
It was confirmed that a bonding strength of about 7 to 9 [kg / mm ² ] obtained with -37Pb was obtained. Elemental analysis of the cross section of the joint showed 42Sn-58Bi, 41.6Sn.
For both the samples using -57.4Bi-1Ag, the structure of the joint was (Sn-Bi solder / Sn of about 500 nm thick).
And Ni or Cu alloy layer / Ni layer or Cu layer).

That is, as shown in FIG. 5, the lead 14 covered with a coating layer 24 made of a Ni layer or a Cu layer and further covered with a coating layer 26 made of an Au layer or a Sn layer.
When the electronic component 18 having the above is joined to the wiring layer 12 on the circuit board 10 by the Sn-Bi solder 20 (see FIG. 5).
(A)), the coating layer 26 in the region in contact with the Sn-Bi solder 20 diffuses into the Sn-Bi solder 20, and Sn-B
The i-based solder 20 and the coating layer 24 are in direct contact with each other (Fig. 5).
(B)). Thereby, an alloy layer of Sn and Ni or Cu is formed at the interface between the Sn-Bi solder 20 and the coating layer 24, and the above-described structure is formed.

Since such a structure is almost the same as the case of using Sn-Pb type solder, it is considered that good bonding strength is obtained by obtaining such a structure of the bonding portion. To be If Au plating is used,
If the amount of Au plating is too large, AuSn compound 28 is generated in the solder, which may deteriorate the mechanical properties of the solder itself (FIG. 6). Therefore, in consideration of the very small amount of solder used for joining such as normal QFP, which is several μg to several mg, the thickness of the Au plating film should be adjusted in order not to change the mechanical properties of the solder. It is desirable to set within 0.5 μm.

At present, it is difficult to plate the lead portion with Sn—Bi solder, so that pure Sn plating is applied to the lead or the electrode on the surface of the substrate to bond even when Sn—Bi solder is used. Bonding with high strength can be performed. However, further consideration is needed to form Sn plating. That is, whilst Sn is electroplated alone, whiskers are generated. Therefore, it is desirable to prevent whiskers by adding a trace amount of element such as Sb (antimony), Ag, Zn (zinc), Bi, Ge (germanium), or Co (cobalt) to Sn.

From the results obtained in this way, the outermost surface is coated with Sn which is a solder component or Au which is a material which has good wettability with the solder and diffuses into the solder at the time of joining, Further, it is considered that good bonding strength can be obtained by disposing a Ni film or a Cu film that can obtain high bonding strength due to the alloy layer formed with the solder.

Therefore, the surface coating according to this embodiment is
It was formed on the 42 alloy lead part of QFP having 08 pins and the bonding strength was measured. First, the lead portion of the QFP was plated with Ni having a thickness of about 2 μm, and the surface thereof was further plated with Sn having a thickness of about 2 μm or Au plating having a thickness of about 1 μm. Then, on a glass epoxy substrate having a Cu electrode formed on its surface, 41.6Sn-57.4Bi-1Ag
Bonding was performed at a temperature of 170 ° C. using solder.

As a result of measuring the bonding strength by pulling the leads bonded in this way, a bonding strength of about 700 gf / pin was obtained regardless of which of the leads was treated. This value is comparable to the case of using 37Sn-63Pb. Thus, according to the present embodiment,
Sn, which is a solder component, on the lead or the electrode on the substrate surface
Alternatively, the outermost surface is coated with Au, which is a material that has good wettability with the solder and diffuses into the solder at the time of joining. By arranging the Cu film, S
Sufficient bonding strength can be obtained using n-Bi solder.

The material for coating the outermost surface does not need to be Au or Sn as long as it is a material that diffuses into solder at the time of joining, and is, for example, Sn-Bi solder plating or hot dipping. Good. Sufficient bonding strength can be obtained also by using these. Further, the outermost surface may be covered with the Pd film shown in the first embodiment instead of the Au film or the Sn film. In this case, P to cover
Since the d film is sufficiently thin, solder and Ni film or C
Since it is in direct contact with the u film, sufficient bonding strength can be obtained.

[0044]

As described above, according to the present invention, the lead portion for electrically solder-joining to the joined portion has a thickness of 75 nm.
Since the Sn-Pd reaction layer formed by bonding can be made sufficiently thin by covering with a coating layer made of a thinner Pd film, high bonding strength can be obtained even when Sn-Bi solder is used. You can

An electronic component to be joined to a joined portion by using Sn—Bi solder, which is composed of a lead portion for joining to the joined portion and a Cu layer or a Ni layer covering the lead portion. It has a coating layer which has a 1st layer and a 2nd layer which covers a 1st layer, and when a lead part joins a to-be-joined part, a 1st layer and Sn-Bi system solder Because they will be joined
The high bonding strength obtained between the Sn—Bi solder and the Ni layer or the Cu layer can be sufficiently exhibited.

In the above electronic component, if the second layer is made of a material dispersed in Sn-Bi solder at the time of joining, the first layer and the Sn-Bi solder are joined after joining. Therefore, high bonding strength can be obtained after bonding. In the above electronic component,
An Au layer can be applied to the second layer.

In the above electronic component, if a metal material having a melting point close to that of Sn-Bi solder is used as the second layer, the first layer and the Sn-Bi solder may be joined after joining. Therefore, high bonding strength can be obtained after bonding. Further, in the above electronic component, a Sn layer or a Sn-Bi layer can be applied to the second layer.

Further, in the above electronic component, if the first layer has a thickness of 0.5 μm or more, the Ni layer or the Cu layer does not react with each other, and the Sn—Bi solder and the Ni layer do not react after joining. Alternatively, a bond with the Cu layer can be formed. Further, by covering the electrode portion for electrically connecting the electronic component with the coating layer, it is possible to configure a circuit board having high bonding strength even when Sn—Bi solder is used.

If a circuit board in which the above electronic components are joined to the electrode portion by Sn-Bi solder is formed, the joining reliability of the electronic components can be improved. Therefore, the circuit board on which the electronic components are mounted is improved. The reliability of can also be improved. Further, if the above electronic component is joined to the joined portion by using Sn—Bi solder, it can be joined to the joined portion with high joining strength.

In addition, in the above-described method for joining electronic parts, the composition of Sn is 40 to 60 wt%, the composition of Ag is 0 to 2 wt%, and Bi is the remaining composition Sn-.
If the Bi-based solder is used, the solder having a low melting point and high mechanical strength can be bonded with high bonding strength.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a reaction mode with a lead of an electronic component when Sn—Bi solder is used.

FIG. 2 is a graph showing the relationship between the thickness of the Pd plating layer and the bonding strength when bonding is performed using 42Sn-58Bi solder.

FIG. 3 is a diagram (No. 1) showing the method used for measuring the bonding strength in the present embodiment.

FIG. 4 is a diagram (part 2) showing the method used for measuring the bonding strength in the present embodiment.

FIG. 5 is a diagram illustrating a structure of an electronic component, a method for joining the electronic component, and a circuit board according to a second embodiment of the present invention.

FIG. 6 is a diagram for explaining a problem when the Au film covering the leads is thick in the second embodiment of the present invention.

FIG. 7 is a diagram illustrating a reaction mode of a joint portion in a conventional method of joining electronic components.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Circuit board 12 ... Wiring 14 ... Lead 16 ... Pd plating layer 18 ... Electronic component 20 ... Sn-Bi type | system | group solder 22 ... Sn-Pd alloy layer 24 ... Coating layer 26 ... Coating layer 28 ... Compound of Sn and Au 30 ... Wire 32 ... Polyimide film 34 ... Preliminary solder 36 ... Plating layer 38 ... 63 Sn-37Pb solder coating 40 ... Ternary eutectic alloy

Claims (11)

[Claims] 1. An electronic component in which a lead portion for electrically soldering to a joined portion is covered with a coating layer made of a Pd film thinner than 75 nm. 2. An electronic component to be joined to a joined portion using Sn—Bi solder, a lead portion for joining to the joined portion, and a Cu layer or a Ni layer covering the lead portion. A first layer composed of the first layer and a second layer covering the first layer, and the first layer and the second layer when the lead portion is joined to the joined portion. An electronic component characterized by being joined to Sn-Bi solder. 3. The electronic component according to claim 2, wherein the second layer is composed of a material dispersed in the Sn—Bi solder during joining. 4. The electronic component according to claim 3, wherein the second layer is an Au layer. 5. The electronic component according to claim 2, wherein the second layer is made of a metal material having a melting point close to that of the Sn—Bi solder. 6. The electronic component according to claim 5, wherein the second layer is a Sn layer or a Sn—Bi layer. 7. The electronic component according to claim 3, wherein the first layer has a film thickness of 0.5 μm or more. 8. A circuit board, wherein an electrode portion for electrically connecting electronic components is covered with the coating layer according to any one of claims 1 to 7. 9. A circuit board, wherein the electronic component according to any one of claims 1 to 7 is bonded to an electrode portion by Sn—Bi solder. 10. The method of joining an electronic component according to claim 1, wherein the electronic component is joined to the joined portion by using Sn—Bi solder. How to join electronic components. 11. The method for joining electronic components according to claim 10, wherein the Sn—Bi solder has a Sn composition of 40 to 60 wt%, an Ag composition of 0 to 2 wt%, and a remaining Bi content. A method of joining electronic components, characterized in that