JP3840861B2 - Metal joining method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal bonding method, and more particularly to a method for connecting wirings on two circuit boards.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 8-330726 discloses a method of connecting metal wirings of two circuit boards, and destroys an oxide film formed on the surface of solder by the volume expansion energy due to boiling of a hydrocarbon compound. Thus, the substrate electrodes are joined via the solder.
[0003]
However, when the volume expansion energy of the hydrocarbon compound is used, the base metal constituting the substrate electrode is not melted even if the oxide film on the metal surface that is melted at the time of joining such as solder can be destroyed. The oxide film on the surface of the base metal cannot be removed. Therefore, when solder is applied only to one of the substrate electrodes, sufficient bonding strength may not be obtained.
[0004]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a metal bonding method capable of obtaining sufficient bonding strength.
[0005]
[Means for Solving the Problems]
According to invention of Claims 1-8, between the connection part of the wiring in the 1st and 2nd circuit board, C—H bond dissociation energy is 950 kJ / mol or less , and alicyclic A hydrocarbon compound is heated by interposing a hydrocarbon compound containing carbon of secondary, linear tertiary, benzylic tertiary, alicyclic allylic tertiary, and bilateral benzylic secondary , Bonding is performed while reducing the oxide film formed on the surface of the metal by the hydrocarbon compound in a radical state in which hydrogen is separated from the hydrocarbon compound by thermal decomposition.
[0006]
Here, as shown in FIG. 6, the C—H bond dissociation energy ΔH is the energy required for the hydrocarbon compound to dissociate into an alkyl group and hydrogen while holding the electrons, It is calculated from molecular orbital calculation. In other words, the C—H bond dissociation energy ΔH of each substance indicates the ease of dissociation of the hydrocarbon compound into an alkyl group and hydrogen. Easily dissociates.
[0007]
Then, in FIG. 6, when each of them has an electron and dissociates into an alkyl group and hydrogen, the alkyl group becomes a radical state, deprives oxygen from copper oxide or the like, that is, reduces copper oxide, and self-oxidizes alkane. Stabilizes as a thing.
[0008]
Thus, sufficient bonding strength can be obtained by using a hydrocarbon compound that exhibits a reducing action by thermal decomposition.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0010]
FIG. 5 shows a state in which the second circuit board 20 is mounted on the first circuit board 10 and the wirings are connected to each other, that is, a state after the connection.
In the present embodiment, a printed wiring board (PWB) is used for the first circuit board 10. In this circuit board 10, a connection part C1 of metal wiring is formed on the surface of the insulating substrate 11, and this connection part C1 is constituted by a metal electrode 12 made of copper (Cu). On the other hand, a flexible wiring board (FPC) is used for the second circuit board 20. In the circuit board 20, a metal wiring connection portion C <b> 2 is formed on the surface of the insulating substrate 21. The connection portion C <b> 2 includes a metal electrode 22 made of copper (Cu) and solder 23 attached to the metal electrode 22.
[0011]
As described above, in the present embodiment, the connection portions C1 and C2 of the wirings in the first and second circuit boards 10 and 20 are placed on the metal electrodes 12 and 22 and at least one of the metal electrodes 12 and 22, respectively. It is comprised by the solder 23 made.
[0012]
And the connection part C1 by the side of the 1st circuit board 10 and the connection part C2 by the side of the 2nd circuit board 20 are joined by soldering (a copper terminal and a solder covering copper terminal are joined). In this way, the connection part C1 of the metal wiring on the first circuit board 10 and the connection part C2 of the metal wiring on the second circuit board 20 are connected.
[0013]
Next, a manufacturing method is demonstrated using FIGS.
First, as shown in FIG. 1, a first circuit board (PWB) 10 and a second circuit board (FPC) 20 are prepared. At this time, an oxide film 12a is formed on the surface of the connection portion (Cu wiring) C1 of the metal wiring in the first circuit board 10 by air oxidation. Further, in the second circuit board 20, an oxide film 23a is formed on the surface of the solder 23 at the connection portion C2 of the metal wiring by air oxidation.
[0014]
Then, as shown in FIG. 2, a hydrocarbon compound 30 having a C—H bond dissociation energy of 950 kJ / mol or less is applied on the connection portion (Cu wiring) C <b> 1 of the first circuit board 10. Examples of the hydrocarbon compound 30 include those having at least one of cyclooctane, tetramethylpentadecane, triphenylmethane, dicyclopentadiene, and dihydroanthracene.
[0015]
Subsequently, as shown in FIG. 3, the second circuit board 20 is stacked on the first circuit board 10 so that the connection portions C1 and C2 of the metal wiring face each other. As a result, C—H bond dissociation energy is generated between the metal constituting the wiring connection portion C1 on the first circuit board 10 and the metal constituting the wiring connection portion C2 on the second circuit board 20. In a state where a hydrocarbon compound 30 of 950 kJ / mol or less is interposed, the connecting portions C1 and C2 of both the substrates are arranged to face each other.
[0016]
And it heats more than melting | fusing point of the solder 23 in the state which pressurized between the connection parts C1 and C2 of the metal wiring in both the boards 10 and 20. FIG. The pressurization at this time is, for example, 0.3 to 2.0 MPa. The pressurizing / heating time is 1 to 10 seconds.
[0017]
At this time, as shown in FIGS. 4 and 6, by heating the hydrocarbon compound 30, the hydrocarbon compound 30 is thermally decomposed into a radical state in which hydrogen is separated from the hydrocarbon compound 30. While the oxide films 12a and 23a formed on the surface of the metal are reduced by the hydrocarbon compound in the state, the metals constituting the connection portions C1 and C2 of the two substrates are joined by melting the metal (solder). In other words, the oxide films 12a and 23a are broken by the reduction of the oxide films 12a and 23a to expose a clean metal surface, and the wettability is good, and the surface of the Cu film 12 on the substrate 10 side and the solder 23 on the substrate 20 side are exposed. As shown in FIG. 5, the solder 23 on the substrate 20 side and the Cu film 12 on the substrate 10 side are bonded together as the surface comes into contact and the solder 23 dissolves.
[0018]
As described above, in this embodiment, the hydrocarbon compound 30 is heated to a temperature equal to or higher than the melting temperature of the solder 23, thereby reducing the oxide films 12 a and 23 a on the surface of the solder 23 or the metal electrode 12 with the hydrocarbon compound 30. The metal electrodes 12 and 22 are joined by melting the solder 23.
[0019]
In this way, the base material (Cu film 12 in this example) and the oxide films 12a and 23a on the surface of the solder 23 are removed and connected, and component mounting with high connection reliability (connection between wirings) is possible. It becomes. That is, by using a hydrocarbon compound (hydrocarbon compound having a C—H bond dissociation energy of 950 kJ / mol or less) 30 as a reducing agent for the oxide films 12a and 23a on the metal surface, clean metal surfaces are brought into contact with each other. Soldering can be performed, and a reliable and good connection can be obtained.
[0020]
Thus, in this embodiment, sufficient bonding strength can be obtained by using a hydrocarbon compound 30 that exhibits a reducing action by thermal decomposition. That is, by using a specific hydrocarbon compound having a C—H bond dissociation energy of 950 kJ / mol or less as the hydrocarbon compound 30, the hydrocarbon compound can exhibit a reducing action.
[0021]
The inventors have conducted various experiments on the bonding principle, which will be described below.
(I). The amount of hydrogen and water generated when copper oxide was immersed in various hydrocarbon compound solutions and heated was detected. As a result, generation of hydrogen was confirmed, but water was not detected. For this reason, it was confirmed that reduction of copper oxide was not performed by hydrogen.
[0022]
(Ii). Reaction products when copper oxide was immersed in various hydrocarbon compound solutions and heated were analyzed. As a result, the presence of an oxidized hydrocarbon compound was confirmed (for example, in the case of cyclooctane, the presence of cyclooctanone and cyclooctanol was confirmed). Thereby, it was considered that the hydrocarbon compound itself may be reducing copper oxide.
[0023]
(Iii). In order to confirm the truth of the inference of (ii), the relationship between the C—H bond dissociation energy and the reduction rate constant of various hydrocarbon compounds was determined. The result is shown in FIG. In FIG. 7, the horizontal axis represents C—H bond dissociation energy ΔH, the vertical axis represents the reduction rate constant, and dicyclopentadiene, triphenylmethane, cyclooctane, tetramethylpentadecane, and eicosane were used as samples. Here, as shown in FIG. 8, the reduction rate constant is a wavelength dispersive X-ray spectroscopy of oxygen on the copper surface when a substrate (with the copper terminal oxidized) is placed in a sample and held at 300 ° C. for a predetermined time. Quantification (reduction state quantification) is performed by an analytical method, and is obtained by the following formula.
[0024]
Reduction rate constant k = (1−X / X1) / (t · X)
However, X1; X-ray count number X in the initial oxidation state; X-ray count number t after time; heating time (seconds)
As a result, as shown in FIG. 7, it was confirmed that there is a relationship in which the reduction rate increases as the C—H bond dissociation energy decreases. For this reason, it was confirmed that the copper oxide etc. were reduced with the hydrocarbon compound which became the radical state.
[0025]
(Iv). When a copper terminal and a solder-coated terminal were joined using various substances having a relatively small C—H bond dissociation energy, as shown in FIG. 9, carbonization having a C—H bond dissociation energy of 950 kJ / mol or less. About a hydrogen compound, the connection area ratio equivalent to the conventional flux was obtained, and sufficient connection strength was ensured (The connection characteristic is so favorable that CH bond dissociation energy is small). Specifically, in FIG. 9, the horizontal axis represents C—H bond dissociation energy ΔH, the vertical axis represents the connection area ratio, and dihydroanthracene, dicyclopentadiene, cyclooctane, tetramethylpentadecane, and eicosane were used as samples. Here, the connection area ratio refers to the above-mentioned observation in the region where the rectangular junction part has the poorest junction at the rectangular junction part (assuming that a square observation window is created). Taking the window, the ratio of the area where bonding was actually performed to the total area inside the window was obtained. As a result, it was found that a substance having a C—H bond dissociation energy of about 950 kJ / mol or less may be used in order to obtain a connection area ratio of “0.7” or more when using a flack.
[0026]
In addition, regarding soldering without using flux, conventionally, soldering has been performed after connection using flux, but cleaning is difficult due to environmental problems, and flux residue causes a decrease in insulation. Since a problem has arisen, when soldering without using flux, the connection area cannot be secured sufficiently due to the influence of the oxide film, and the connection reliability is poor. Therefore, it is useful to ensure good connectivity by destroying the oxide film without using flux. Further, in this method, the metal is not dissolved unlike the flux, and the metal ion is not generated, so that the insulating property is not lowered. That is, the reduction reaction of this method proceeds in the form of extracting oxygen from the metal oxide, so that metal ions are not generated.
(Second Embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment.
[0027]
In the first embodiment, the present invention is applied to the case where the copper terminal and the solder-coated copper terminal are joined (soldered), but in this embodiment, the present invention is applied to the case where the terminals constituting the terminals are joined by mutual diffusion. .
[0028]
FIG. 14 shows a state in which the second circuit board 20 is mounted on the first circuit board 10 in this embodiment and the wirings are connected to each other, that is, a state after the connection.
[0029]
In the first circuit board (PWB) 10, a metal wiring connection portion C <b> 1 is formed on the surface of the insulating substrate 11. The connection portion C1 is composed of a metal electrode 12 made of copper (Cu), a nickel film 13 deposited thereon, and a gold plating film 14 formed thereon.
[0030]
On the other hand, in the second circuit board (FPC) 20, a metal wiring connection portion C <b> 2 is formed on the surface of the insulating substrate 21. The connecting part C2 is composed of a metal electrode made of copper (Cu) and a tin film 23 deposited on the surface thereof.
[0031]
The gold plating film 14 on the first circuit board 10 side and the tin film 23 on the second circuit board 20 side are joined by mutual diffusion of both metals. In this way, the connection part C1 of the metal wiring on the first circuit board 10 and the connection part C2 of the metal wiring on the second circuit board 20 are connected.
[0032]
Next, a manufacturing method is demonstrated using FIGS.
First, as shown in FIG. 10, a first circuit board (PWB) 10 and a second circuit board (FPC) 20 are prepared. At this time, an oxide film 14a is formed on the surface of the gold plating film 14 at the metal wiring connection portion C1 in the first circuit board 10 by air oxidation. Further, in the second circuit board 20, an oxide film 23a is formed on the surface of the tin film 23 at the metal wiring connection portion C2 by air oxidation.
[0033]
Then, as shown in FIG. 11, a hydrocarbon compound 30 having a C—H bond dissociation energy of 950 kJ / mol or less is applied on the gold plating film 14 of the first circuit board 10.
[0034]
Subsequently, as shown in FIG. 12, the second circuit board 20 is overlaid on the first circuit board 10 so that the connection portions C1 and C2 of the metal wiring face each other. Thus, in the state where the hydrocarbon compound 30 is interposed between the metal (14) on the first circuit board 10 side and the metal (23) on the second circuit board 20 side, The metal wiring connection portions C1 and C2 are arranged to face each other. That is, the C—H bond dissociation energy is 950 kJ between the metal constituting the wiring connection portion C1 on the first circuit board 10 and the metal constituting the wiring connection portion C2 on the second circuit board 20. With the hydrocarbon compound 30 of / mol or less interposed, the connecting portions C1 and C2 of both the substrates are arranged facing each other.
[0035]
The metal (Au) 14 on the first circuit board 10 side and the metal (Sn) on the second circuit board 20 side in a state in which the space between the metal wiring connection portions C1 and C2 on both the boards 10 and 20 is pressurized. ) 23 is heated below the melting point of the metal (Sn) having a lower melting point. The pressurization at this time is, for example, 0.3 to 2.0 MPa. Moreover, regarding heating temperature, it is 180-200 degreeC below melting | fusing point (232 degreeC) of tin. Furthermore, pressurization / heating time is 1 to 10 seconds.
[0036]
At this time, as shown in FIG. 13, by heating the hydrocarbon compound 30, the hydrocarbon compound 30 is thermally decomposed into a radical state in which hydrogen is separated from the hydrocarbon compound 30, and this radical state is obtained. While the oxide films 14a and 23a formed on the metal surface by the hydrocarbon compound are reduced, the metals constituting the connection portions C1 and C2 of the two substrates are joined by metal diffusion.
[0037]
That is, the oxidation of the oxide film 14a on the surface of the gold plating film 14 and the oxide film 23a on the surface of the tin film 23 by the hydrocarbon compound 30, that is, the oxidation of the surfaces of the metals 14 and 23 on the first and second circuit boards 10 and 20 side. The films 14a and 23a are reduced. The oxide films 14a and 23a are broken by the reduction of the oxide films 14a and 23a, and a clean metal surface is exposed. As a result, the surface of the gold plating film 14 on the substrate 10 side and the surface of the tin film 23 on the substrate 20 side are in contact with each other with good wettability. Then, mutual diffusion of gold and tin occurs, and as shown in FIG. 14, the tin film 23 on the substrate 20 side and the gold plating film 14 on the substrate 10 side are joined.
[0038]
As described above, in this embodiment, the wiring connection portion C1 in the first circuit board 10 includes gold, and the wiring connection portion C2 in the second circuit board 20 includes tin. Both metals are joined by diffusion by heating below the melting point of tin with the hydrocarbon compound 30 interposed between them and tin.
[0039]
In this way, the oxide films 14a and 23a on the surface of the base material (in this example, the Au film 14 and the tin film 23) are removed and connected, and component mounting (connection between wirings) having high connection reliability is achieved. It becomes possible. That is, by using the hydrocarbon compound 30 as a reducing agent for the oxide films 14a and 23a on the metal surface, clean metal surfaces can be brought into contact with each other for mutual diffusion, and a reliable and good connection can be achieved. can get.
[0040]
Moreover, since there is no soldering process as a joining means, it is inexpensive. Furthermore, in the case of soldering, an electrode pitch of 0.3 mm was the limit, but if this method is used, bonding can be performed even if the electrode pitch is 0.3 mm or less. In other words, the mounting method by soldering is not suitable for fine connection, and the brazing method is not suitable for fine connection because of the protrusion of the brazing material. Can also be applied. More specifically, in recent years, in mounting electronic products, there is an increasing demand for component mounting and connection technology with a fine pitch, but the mounting method by soldering is unsuitable for fine connection. .3 mm is the limit, and similarly, the brazing method is not suitable for fine connection due to the protrusion of the brazing material, but in this embodiment, it can be applied to products having a fine pitch. it can.
[0041]
As described above, component mounting (connection between wirings) having high connection reliability can be performed even when the electrode interval is narrow.
(Third embodiment)
Next, the third embodiment will be described with a focus on differences from the second embodiment.
[0042]
FIG. 19 shows a state where the second circuit board 60 is mounted on the first circuit board 50 and the wirings are connected to each other, that is, a state after the connection.
In the first circuit board 50, a connection portion C1 of metal wiring is formed on the surface of the insulating substrate 51, and the connection portion C1 is constituted by a metal electrode 52 made of copper (Cu). The insulating substrate 51 is an alumina substrate. On the other hand, in the second circuit board 60, a connection portion C2 of metal wiring is formed on the surface of the insulating substrate 61, and the connection portion C2 is constituted by a metal electrode 62 made of copper (Cu). The insulating substrate 61 is an alumina substrate.
[0043]
Then, the connection part (Cu wiring) C1 of the metal wiring on the first circuit board 50 side and the connection part (Cu wiring) C2 of the metal wiring on the second circuit board 60 side are joined by mutual diffusion of both metals. ing. In this way, the connection part C1 of the metal wiring on the first circuit board 50 and the connection part C2 of the metal wiring on the second circuit board 60 are connected.
[0044]
Next, a manufacturing method is demonstrated using FIGS.
First, as shown in FIG. 15, a first circuit board 50 and a second circuit board 60 are prepared. At this time, an oxide film 52a is formed on the surface of the connection portion (Cu wiring) C1 of the metal wiring in the first circuit board 50 by air oxidation. Similarly, an oxide film 62a is formed on the surface of the connection portion (Cu wiring) C2 of the metal wiring in the second circuit board 60 by air oxidation.
[0045]
Then, as shown in FIG. 16, a hydrocarbon compound 70 having a C—H bond dissociation energy of 950 kJ / mol or less is applied onto the metal wiring connection portion (Cu wiring) C <b> 1 of the first circuit board 50. Examples of the hydrocarbon compound 70 include those having at least one of cyclooctane, tetramethylpentadecane, triphenylmethane, dicyclopentadiene, and dihydroanthracene.
[0046]
Subsequently, as shown in FIG. 17, the second circuit board 60 is stacked on the first circuit board 50 so that the connection portions C1 and C2 of the metal wiring face each other. As a result, both substrates 50 in a state where the hydrocarbon compound 70 is interposed between the metal wiring connection portion C1 in the first circuit board 50 and the metal wiring connection portion C2 in the second circuit board 60. 60, the metal wiring connection portions C1 and C2 are arranged facing each other. That is, the C—H bond dissociation energy is 950 kJ between the metal constituting the wiring connection portion C1 on the first circuit board 50 and the metal constituting the wiring connection portion C2 on the second circuit board 60. The connecting portions C1 and C2 of the two substrates are arranged facing each other with a hydrocarbon compound 70 of / mol or less interposed.
[0047]
And it heats below to melting | fusing point of the metal (Cu) which comprises a metal wiring in the state which pressurized between the connection parts C1 and C2 of the metal wiring in both the board | substrates 50 and 60. FIG. The pressurization at this time is, for example, 0.3 to 2.0 MPa. Moreover, regarding heating temperature, it is 700-1000 degreeC below melting | fusing point (1083 degreeC) of Cu. Furthermore, pressurization / heating time is 30 to 60 minutes.
[0048]
At this time, by heating the hydrocarbon compound 70, the hydrocarbon compound 70 is thermally decomposed into a radical state in which hydrogen is separated from the hydrocarbon compound 70, and the hydrocarbon compound in the radical state causes the metal to While reducing the oxide films 52a and 62a formed on the surface, the metals constituting the connecting portions C1 and C2 of the two substrates are joined by metal diffusion.
[0049]
That is, the hydrocarbon compound 70 reduces the oxide film 52a on the surface of the Cu film 52 and the oxide film 62a on the surface of the Cu film 62, that is, the metal oxide films 52a and 62a on the metal surface constituting the metal wiring. Due to the reduction of the oxide films 52a and 62a, the oxide films 52a and 62a are broken to expose clean surfaces. As a result, as shown in FIG. 18, the surface of the Cu film 52 on the substrate 50 side and the surface of the Cu film 62 on the substrate 60 side are in contact with each other with good wettability. Then, mutual diffusion of Cu occurs (copper mutually diffuses in solid phase), and as shown in FIG. 19, the Cu film 52 on the substrate 50 side and the Cu film 62 on the substrate 60 side are joined.
[0050]
In this way, the oxide films 52a and 62a on the surface of the base material (Cu films 52 and 62 in this example) are removed and connected, and component mounting (connection between wirings) with high connection reliability is possible. Become. That is, by using the hydrocarbon compound 70 as a reducing agent for the oxide films 52a and 62a on the metal surface, clean metal surfaces can be brought into contact with each other for mutual diffusion, and a reliable and good connection can be achieved. can get.
[0051]
As described above, similarly to the second embodiment, component mounting (connection between wirings) having high connection reliability can be performed even when the electrode interval is narrow.
In the first to third embodiments, the hydrocarbon compound is applied only to the connection portion C1 of the first circuit board. However, the hydrocarbon compound is applied only to the connection portion C2 of the second circuit board, or both. You may apply | coat to the connection part C1, C2 of a board | substrate.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view for explaining a mounting method according to a first embodiment.
FIG. 2 is a cross-sectional view for explaining the mounting method.
FIG. 3 is a cross-sectional view for explaining the mounting method.
FIG. 4 is a cross-sectional view for explaining the mounting method.
FIG. 5 is a cross-sectional view for explaining the mounting method.
FIG. 6 is a view for explaining a CuO reduction reaction by alkane.
FIG. 7 is a graph showing the relationship between C—H bond dissociation energy and reduction rate constant.
FIG. 8 is a diagram for explaining a method for measuring a CuO reduction reaction rate.
FIG. 9 is a diagram showing the relationship between C—H bond dissociation energy and connection area ratio.
FIG. 10 is a cross-sectional view for explaining a mounting method according to a second embodiment.
FIG. 11 is a cross-sectional view for explaining the mounting method.
FIG. 12 is a sectional view for explaining the mounting method.
FIG. 13 is a cross-sectional view for explaining the mounting method.
FIG. 14 is a cross-sectional view for explaining the mounting method.
FIG. 15 is a cross-sectional view for explaining a mounting method according to a third embodiment.
FIG. 16 is a cross-sectional view for explaining the mounting method.
FIG. 17 is a cross-sectional view for explaining the mounting method.
FIG. 18 is a cross-sectional view for explaining the mounting method.
FIG. 19 is a cross-sectional view for explaining the mounting method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... 1st circuit board, 12 ... Metal electrode, 12a ... Oxide film, 14 ... Gold plating film, 14a ... Oxide film, 20 ... Second circuit board, 22 ... Metal electrode, 23 ... Solder, 23a ... Oxide film, DESCRIPTION OF SYMBOLS 30 ... Hydrocarbon compound, 50 ... 1st circuit board, 52a ... Oxide film, 60 ... 2nd circuit board, 62a ... Oxide film, 70 ... Hydrocarbon compound, C1 ... Connection part of metal wiring, C2 ... Metal wiring Connection part.

Claims (8)

A method for connecting a wiring connection portion (C1) on a first circuit board and a wiring connection portion (C2) on a second circuit board,
C—H bond dissociation energy is present between the metal constituting the wiring connection portion (C1) on the first circuit board and the metal constituting the wiring connection portion (C2) on the second circuit board. Hydrocarbon compound having a carbon content of 950 kJ / mol or less and having alicyclic secondary, linear tertiary, benzylic tertiary, alicyclic allylic tertiary and bilateral benzylic secondary carbon (30, 70) A step of arranging the connecting portions (C1, C2) of both substrates facing each other with the intervening state,
By heating the hydrocarbon compound (30, 70), the hydrocarbon compound (30, 70) is thermally decomposed into a radical state in which hydrogen is separated from the hydrocarbon compound (30, 70). The step of joining the metals constituting the connecting portions (C1, C2) of both substrates by melting or diffusing the metal while reducing the oxide film formed on the surface of the metal by the hydrocarbon compound in a radical state When,
A metal joining method comprising: The wiring connection portions (C1, C2) on the first and second circuit boards are each constituted by a metal electrode and solder placed on at least one of the metal electrodes. Item 2. The metal bonding method according to Item 1. Heating the hydrocarbon compound (30) to a temperature equal to or higher than the melting temperature of the solder to melt the solder while reducing the oxide film on the surface of the solder or metal electrode with the hydrocarbon compound (30). The metal joining method according to claim 2, wherein the two metal electrodes are joined by the method. The metal bonding method according to claim 1, wherein the metal electrode is copper. The wiring connection part (C1) on the first circuit board contains gold, and the wiring connection part (C2) on the second circuit board contains tin, and between this gold and tin The metal joining method according to claim 1, wherein both metals are joined by diffusion by heating to a melting point of tin or less with the hydrocarbon compound (30) interposed. The said hydrocarbon compound (30,70) has at least one of cyclooctane, tetramethylpentadecane, triphenylmethane, dicyclopentadiene, and dihydroanthracene. Metal bonding method as described in 2. A method for connecting a metal wiring connection (C1) on a first circuit board (10) and a metal wiring connection (C2) on a second circuit board (20),
Between the metal (14) on the first circuit board side and the metal (23) on the second circuit board side, the C—H bond dissociation energy is 950 kJ / mol or less , and the alicyclic secondary class, Metal wiring joints on both substrates with a hydrocarbon compound (30) containing carbon in a straight chain tertiary, benzylic tertiary, alicyclic allylic tertiary, and both benzylic secondary secondary (30) Placing C1, C2) face to face,
Of the metal (14) on the first circuit board side and the metal (23) on the second circuit board side, in a state where the space between the metal wiring connection portions (C1, C2) on both the boards is pressurized When heating below the melting point of a metal having a lower melting point, the hydrocarbon compound (30) is thermally decomposed to form a radical state in which hydrogen is separated from the hydrocarbon compound (30). Reducing the oxide films (14a, 23a) formed on the surface of the metal (14, 23) by the hydrocarbon compound, and performing bonding by mutual diffusion of the two metals (14, 23);
A metal joining method comprising: A method for connecting a metal wiring connection (C1) on a first circuit board (50) and a metal wiring connection (C2) on a second circuit board (60),
The C—H bond dissociation energy is 950 kJ / mol or less between the connection portion (C1) of the metal wiring in the first circuit board and the connection portion (C2) of the metal wiring in the second circuit board , and In both substrates, a hydrocarbon compound (70) containing carbon of alicyclic secondary, linear tertiary, benzylic tertiary, alicyclic allylic tertiary and bilateral benzylic secondary is interposed. A step of arranging the metal wiring connecting portions (C1, C2) facing each other,
The hydrocarbon compound (70) is thermally decomposed when heated below the melting point of the metal constituting the metal wiring in a state where the connection between the metal wiring connecting portions (C1, C2) on both the substrates is pressurized. Thus, a hydrogen radical is separated from the hydrocarbon compound (70) to form a radical state, and an oxide film (52a, 62a) formed on the surface of the metal (52, 62) by the hydrocarbon compound in the radical state. A step of bonding by mutual diffusion of the two metals while reducing
A metal joining method comprising:

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