JP3291887B2 - Method for forming gold-tin solder plating layer and method for bonding the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a gold-tin solder plating layer in which gold-tin solder is formed by lamination plating and joined.

[0002]

2. Description of the Related Art Conventionally, in gold-tin solder bonding, a gold-tin alloy foil is formed and inserted into a bonding portion, or gold and tin are separately plated on a bonding surface facing each other as a single layer by plating or vapor deposition. Formed and joined.

[0003]

In the case of a member to be joined having a fine two-dimensional pattern, the method of inserting a gold-tin alloy foil into the joint portion is that the gold-tin alloy is extremely brittle and fine processing is not easy. Therefore it is not practical. In addition, a technique for forming a gold-tin alloy as a single alloy layer on a bonding surface has not been established. In particular, it is extremely difficult and impractical to precisely control the solder composition.

On the other hand, in the method of forming a gold plating on one of the bonding surfaces and a tin plating on the other, and bonding, the tin plating film is easily oxidized, so that the bonding strength varies, and a non-bonded portion occurs. Causes poor bonding. Therefore, a step of removing the oxide film by Ar atom sputtering or the like before bonding is required. In addition, it is conceivable to form gold plating as an antioxidant layer on tin plating. Usually, gold plating is performed at a plating bath temperature of 50 to 70 ° C. In this case, there is a problem that a sufficient effect as an antioxidant layer cannot be obtained because gold and tin are formed by interdiffusion in the plating film.

An object of the present invention is to provide a method for forming a gold-tin solder plating layer having excellent oxidation resistance and a bonding method therefor.

[0006]

The gist of the present invention for solving the above problems is as follows.

A method of forming a gold-tin solder plating layer in which gold and tin layers are formed and laminated on a gold-tin solder joint of a workpiece by wet plating, respectively, and a gold plating layer is formed on the outermost surface Wherein the gold plating on the outermost surface has a plating bath temperature of 0
A method for forming a gold-tin solder plating layer, characterized in that the layer is formed at a temperature of about 40 ° C.

[0008] The above-mentioned method for forming a gold-tin solder plating layer, wherein the thickness of the gold plating layer formed on the outermost surface is 0.3 µm or more and the total thickness of the gold and tin laminated plating layer is 3 µm or more. It is in.

[0009] Further, a gold and tin layers are formed on the joints of the objects to be joined by wet plating and laminated to form gold-tin plating solder layers, and a gold plating layer is plated on the outermost surface with a plating bath. After forming at a temperature of 0 to 40 ° C. and aligning the joints on which the plated solder layer is formed on the article to be joined, heating is performed at a temperature at which the plating layer is melted in a vacuum or an inert gas. In the joining method. The above can be easily joined.

[0010]

[Action] The plating bath temperature of the outermost gold plating is 0 to 40.
By setting the temperature to ° C., diffusion of gold and tin during plating can be prevented. This prevents tin from diffusing to the outermost surface and prevents oxidation of the outermost surface of the solder layer. Therefore, an operation such as sputtering for removing an oxide film before joining is not required.

[0011] The plating bath temperature of the outermost gold plating is 40
When the temperature exceeds ℃, tin diffuses, and the effect of preventing oxidation of the outermost surface is reduced. On the other hand, if the temperature is lower than 0 ° C., the plating becomes coarse in a granular form, and it becomes easy to peel off.

[0012] The thickness of the gold plating layer on the outermost surface is 0.1 mm.
The thickness is desirably 3 μm or more, and if it is less than 0.3 μm, the tin plating layer cannot sufficiently prevent oxidation.

The gold-tin laminated solder layer is heated to 280 at the time of joining and heating.
By heating to a temperature of not less than ° C., tin dissolves and interdiffuses with gold to form a gold-tin alloy melt layer. At this time, tin diffuses also to the base material side to form a compound, and the tin concentration in the solder layer is reduced to change the melting point of the solder layer. When the tin content is 20% by weight or less or the total solder layer thickness is 3 μm or less, the tin concentration in the solder layer is reduced due to the formation of the compound during the heat bonding, and the melting point of the solder layer is significantly increased. As a result, the bonding is incomplete because the solder layer solidifies before a sufficient melt is generated at the bonding portion.

In the present invention, the tin content is 20% by weight.
And less than 40% by weight and a total thickness of the gold-tin solder layer of 3 μm or more, it is possible to prevent a decrease in the solder melting point due to a decrease in the tin concentration in the solder layer during the heat bonding. .

[0015]

The present invention will be specifically described below with reference to examples.

Embodiment 1 FIG. 1 is a schematic view showing a cross-sectional structure of a thin plate of a print head for an ink jet printer to which the present invention is applied. FIG. 2 is a configuration perspective view showing the configuration of the thin plate constituting the print head. Also, FIG.
FIG. 4 is a schematic cross-sectional view of a joined portion of a printhead thin plate after joining.

As shown in FIG. 2, a diaphragm 6 (SUS304, plate thickness 20 μm) constituting a part of the print head is provided.
m), restrictor 7 (SUS304, plate thickness 50 μm)
And three filters 8 (SUS304, plate thickness 20 μm).

The restrictor 7 has a structure as shown in FIG.
Then, a gold plating 3 is formed at a current density of 2 A / dm ² in a cyan gold plating bath at 65 ° C. at a current density of 2 A / dm ² , a tin plating 4 is formed thereon, and a gold plating 5 is formed on the outermost surface.
Current density 10A / dm ² in cyan gold plating bath
0.5 μm.

The diaphragm 6 and the filter 8 are arranged as shown in FIG.
In the structure shown in FIG. 2B, Ni plating 2 is 1 μm as a base plating on the stainless steel plate 1, and then gold plating 3 is applied with a current density of 2 A / dm ^{2 in} a cyan gold plating bath at 65 ° C.
With a thickness of 0.5 μm.

Next, the three thin plates were aligned from the top in the order of diaphragm 6, restrictor 7, and filter 8, and joined by heating at 300 ° C. in vacuum. After cooling, the inside of the joining chamber was returned to the atmosphere, and the object to be joined was taken out. A joined body having a sectional structure as shown in FIG. 3 was obtained. In this embodiment, the bonding is performed in a vacuum as an atmosphere, but the bonding may be performed in an inert gas atmosphere.

[Embodiment 2] In the restrictor 7 shown in Embodiment 1, N was applied as a base plating on the stainless steel plate 1.
i plating 2 was 1 μm, and then gold plating 3 was ² μm at a current density of 2 A / dm ² in a cyan gold plating bath at 65 ° C.
A tin plating 4 was applied thereon at 3 μm, and a gold plating 5 at the outermost surface was applied at a current density of 10 A / dm ² in a cyan gold plating bath at 20, 30, 40, and 50 ° C. at 1.0 μm.

FIG. 4 shows the result of XMA analysis of the above surface structure. It can be seen that if the plating bath temperature is 40 ° C. or less, diffusion of tin to the surface (joining surface) can be prevented.

[Embodiment 3] In the restrictor 7 shown in Embodiments 1 and 2, Ni plating 2 is 1 μm as a base plating on the stainless steel plate 1 and then gold plating 3 is a cyan gold plating bath of 65 ° C. in the middle, 2.mu. at a current density of 2A / dm ²
m, and tin plating 4 thereon, 3 μm, and gold plating 5 on the outermost surface in a cyan gold plating bath at −5, 0, 10, and 20 ° C. at a current density of 10 A / dm ² and 1.0 μm. gave.

Table 1 shows the results of a tape peeling test of the plating layer. It was found that when the temperature of the gold plating bath on the tin plating was lower than 0 ° C., the gold plating on the surface was peeled off.

[0025]

[Table 1]

[0026]

According to the gold-tin solder laminate plating of the present invention, diffusion of gold and tin can be prevented, and the outermost surface of the solder laminate is covered with the gold plating layer. Oxidation can be prevented and strong bonding can be achieved.

Further, unlike the conventional gold-tin solder laminated plating layer, there is no need for an operation step such as sputtering for removing an oxide film immediately before joining, such as sputtering.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross-sectional structure of a thin plate of a print head for an inkjet printer to which the present invention is applied.

FIG. 2 is a configuration perspective view showing a configuration of a thin plate constituting a print head for an inkjet printer.

FIG. 3 is a schematic cross-sectional view of a bonding portion of a printhead thin plate after bonding by the solder plating method of the present invention.

FIG. 4 is a graph showing the results of XMA analysis of the surface texture of a printhead thin plate to which the solder plating method of the present invention has been applied.

[Explanation of symbols]

1 is a stainless steel plate, 2 is Ni plating, 3 is gold plating, 4
Is a tin plating, 5 is an outermost surface gold plating, 6 is a diaphragm, 7 is a restrictor, 8 is a filter, 9 is an ink flow path, and 10 is a joint.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C25D 5/10 C25D 3/48

Claims (4)

(57) [Claims] 1. A gold-tin solder plating layer in which gold and tin layers are formed and laminated on a gold-tin solder joint portion of an object by wet plating, respectively, and a gold plating layer is formed on the outermost surface. The method of forming a gold-tin solder plating layer, wherein the gold plating on the outermost surface is formed at a plating bath temperature of 0 to 40 ° C. 2. The gold-tin solder according to claim 1, wherein the thickness of the gold plating layer formed on the outermost surface is 0.3 μm or more, and the total thickness of the gold and tin laminated plating layer is 3 μm or more. A method for forming a plating layer. 3. The method for forming a gold-tin solder plating layer according to claim 1, wherein the tin content of the gold-tin laminated plating layer is controlled to be more than 20% by weight and less than 40% by weight. . 4. A gold-tin plating solder layer is formed by laminating and laminating gold and tin layers on a joint portion of an object by wet plating, and a gold plating layer is formed on the outermost surface by a plating bath. After forming at a temperature of 0 to 40 ° C. and aligning the bonding portion of the article to which the plating solder layer is formed, heating is performed at a temperature at which the plating layer melts in a vacuum or an inert gas. And the joining method.