JPH03264179A - Welded structure - Google Patents

Abstract

PURPOSE:To prevent the generation of cracking by welding a substrate consisting of a copper metal subjected to gold plating and a package consisting of a ferrous metal together with a sheet consisting of a copper metal. CONSTITUTION:The substrate 26 is made of phosphor bronze essentially consisting of copper and is subjected to the gold plating 34 after nickel plating 32. The package 28 is made of an iron/nickel alloy and is subjected to nickel plating 36. The sheet 38 consisting of the copper is inserted between the substrate 26 and the package 28. An X-Y moving device 18 supports these members and moves the parts to be welded when applied with a laser beam 12 in such a manner that the angle part formed of the substrate 26 to be welded and the package 28 is applied with the laser beam 12. The welded structure free from cracking is obtd. and the need for peeling the gold plating film of a welding member which is heretofore required is eliminated. This structure is optimum for working of precision parts.

Description

[Detailed Description of the Invention] [Summary] It is an object of the present invention to provide a welding structure that can be welded without cracking, regarding a welding structure between a substrate made of a gold-plated copper-based metal and a package made of an iron-based metal. The purpose of the invention is to consist of a board made of copper-based metal plated with gold, a package made of iron-based metal, and a sheet of copper-based metal inserted between the board and the package. is welded together with the copper-based metal sheet.

[Industrial application field]

The present invention relates to a welded structure in which a first member made of gold-plated copper-based metal and a second member made of iron-based metal are fixed by welding.

In optical transmission system packages using optical fibers, which have been becoming smaller in size in recent years, optical semiconductor elements are mounted on a substrate, and this substrate is fixed to the package. Such substrates are made of a copper-based alloy with high thermal conductivity, assuming that the temperature of the mounted optical semiconductor elements will rise. Further, an optical semiconductor element is usually fixed to a substrate by a bonding process, and a copper-based alloy substrate is plated with gold to facilitate the bonding process. The package, on the other hand, was made of iron-based alloy. In addition, iron-based alloy packages were often plated with gold as a surface treatment to improve soldering properties.

[Conventional technology]

Conventionally, soldering has been used to fix such a copper-based alloy substrate to a ferrous metal package. However, in the case of soldering, creep occurs during the process of use, and there is a possibility that the position of the board may shift.

In particular, in optical transmission system packages using optical fibers, the diameter of the optical fiber is small, on the order of several micrometers, so it is necessary to ensure that the position of the optical semiconductor element relative to the optical fiber does not deviate by more than a few micrometers. Yes, but
In soldering, there is a possibility that the positional deviation of the board due to the above-mentioned creep becomes large, which poses a problem in terms of long-term reliability. From this point of view, it was considered to use highly reliable laser welding instead of soldering.

[Problem to be solved by the invention]

Welding improves the bonding strength and solves the problem of substrate misalignment. However, while the package material usually uses an iron-based alloy, the package and substrate are plated with gold, so in the usual welding method, a large amount of gold gets mixed into the welded part, and the iron is removed during cooling. and gold alloys are produced.

The alloy of iron and gold is a peritectic alloy, and the solidification temperature range of the weld is extremely large. That is, in peritectic alloys, there is a large range between the temperature at which the weld zone begins to solidify after welding and the temperature at which solidification ends. Therefore, a problem occurred in that cracks were generated in the welded portion. Conventionally, methods to prevent this cracking include grinding the gold plating at the welded area by mechanical processing or chemically peeling it off to prevent the gold that causes cracks from entering the welded area. Alternatively, treatments such as partial plating were performed and welding was performed.

Such conventional welded structures require an extra process to remove the gold plating, and if etching or grinding is performed to remove the gold plating, the parts may be damaged due to corrosion due to etching solution residue on the board or increased stress. This resulted in drawbacks such as a decrease in dimensional accuracy.

Therefore, an object of the present invention is to provide a welding structure that can weld a first member made of gold-plated copper-based metal and a second member made of iron-based metal without generating cracks. It is.

[Means to solve the problem]

The welded structure according to the present invention includes a first member made of gold-plated copper-based metal, a second member made of iron-based metal,
A sheet of copper-based metal is inserted between the first member and the second member, and the first member and the second member are welded together with the sheet of copper-based metal. It is characterized by the presence of

[For production]

In the above structure, in the welded part after welding, gold and copper form a solid solution alloy, and this alloy and iron coexist. As a result, the entire weld zone becomes a solid solution type alloy, the solidification temperature range becomes small, and the transformation from liquid to solid occurs instantaneously, so solidification ends before cracks grow. Therefore, generation of cracks is prevented.

〔Example〕

FIG. 1 shows a laser welding device and a welding member used in accordance with the present invention, and is equipped with a laser light source 10. In FIG. The laser light source 10 generates a laser beam 12 and includes a condensing lens 14 that focuses the laser beam 12, and a laser protection tube and shielding gas nozzle 16. An X-Y moving device 18 is disposed below the laser light source 10, and the X-Y moving device 18 is configured to support the welding member 2°.

The welding member 20 of FIG. 1 is shown in simplified form as part of an optical transmission system package 22, such as that shown in FIG. 4, for example. The optical transmission system package 22 shown in FIG. 4 has an optical semiconductor element 24 mounted on a substrate 26, and this substrate 26 fixed to a package 28. An optical fiber 30 is placed close to the optical semiconductor element 24 and
4 converts the optical signal of the optical fiber 30 into an electrical signal and processes it. Among these parts, the optical semiconductor element 24 is fixed to the substrate 26 by bonding, and the substrate 26 is welded to the package 28 using the welding apparatus shown in FIG.

As shown in FIG. 1, the substrate 26 is made of phosphor bronze containing copper as a main component, and is plated with gold 34 after being plated with nickel 32. As shown in FIG. Moreover, the package 28 is made of iron.
Made of 42% nickel alloy (42 alloy),
Nickel plating 36 is applied. Each plating was 2 μm thick. Additionally, a sheet of copper 38 is inserted between the substrates 26 and the package 28.

The copper sheet 38 had the same area as the bottom surface of the substrate 26 and had a thickness of about 0.1 to 0.5 mm.

In FIG. 1, the X-Y moving device 18 applies a laser beam 1 to the corner of the package 28 and the substrate 26 to be welded.
These members are supported so that they are hit by the laser beam 12, and the parts to be welded are moved when the laser beam 12 hits them. In this way, welding can be performed along the entire circumference of the substrate 26.

Alternatively, spot welding can also be performed.

FIG. 2 shows a welded structure in which the substrate 26 and the package 28 are joined by a weld 40. As shown in FIG. The welded part 40 after welding is formed by the gold of the gold plating 34 of the board 26 and the copper of the copper sheet 38 inserted in the middle forming a solid solution alloy, and this alloy and the iron of the package 28 coexisting. It is a solid solution type alloy. The solidification temperature range of this all-solid solution type alloy is small, and the transformation from liquid to solid occurs instantaneously, so no cracks occur in the welded portion 40.

FIG. 5 is a generally accepted phase diagram of an alloy of gold and copper, showing that a solid solution type alloy is formed with a narrow solidification temperature range.

FIG. 3 shows a conventional example in which a copper sheet 38 is not inserted between the board 26 and the package 28, and the board 26 and the package 28 are directly welded.

In this case, the substrate 26 and the package 28 are joined by a weld 42, but the weld 42 is a peritectic alloy of iron and gold, and the solidification temperature range of the weld 42 is very large. Cracks 44 may occur. In the present invention, the occurrence of cracks 44 could be prevented by inserting the copper sheet 38.

The laser used for welding was a Nd-YAG laser, and the welding conditions were a pulse width of 2 ms, a defocus amount of Omm, an average output of 200 W, a pulse rate of 6 opp, S1, and a welding speed of 500 m.
m/min, lens focal length 10・Qmm, shielding gas is argon, gas pressure 1.5kg/cm2, gas flow rate 3
It was 01/min.

FIG. 6 shows the results of an experiment to determine the copper content of the weld and whether or not cracks would occur in the weld 40 by varying the thickness of the inserted copper sheet 38 under these laser conditions. It is a diagram. Under this condition, the copper content of the weld 40 is approximately proportional to the thickness of the copper sheet 38, and cranking does not occur until the thickness of the copper sheet 38 is Q, 5 mm, which is good. However, when the thickness becomes 0.6 mm, it becomes impossible to perform good welding. The reason why good welding cannot be achieved when the thickness of the copper sheet 38 becomes large is that the laser beam 1
This is thought to be due to the fact that 2 hit only the copper sheet 38 and the copper, which has high thermal conductivity, did not melt. Note that since copper has a high thermal conductivity, inserting the copper sheet 38 requires relatively large welding energy. Therefore, if an alloy of copper and nickel, such as cupronickel, is used instead of the copper sheet 38, the welding energy can be reduced since the thermal conductivity is low.

〔Effect of the invention〕

As explained above, according to the present invention, the first member made of gold-plated copper-based metal and the second member made of iron-based metal are welded with a sheet of copper-based metal interposed therebetween. As a result, a welded structure without cracks can be obtained, there is no need to peel off the gold plating film of the welded parts as in the past, and there is no dimensional change in the parts because the grinding required to remove the gold plating is not performed. Ideal for processing precision parts.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a laser welding device and a welded member used according to the present invention, FIG. 2 is a diagram showing a welded structure obtained by the present invention, FIG. 3 is a diagram showing a welded structure according to the prior art, and FIG.
The figure shows the components of the optical transmission system package to be welded according to the present invention, Figure 5 is a state diagram of the gold-copper alloy, and Figure 6 shows the copper of the welded part when the thickness of the copper sheet is changed. FIG. 2 is a diagram showing the content and occurrence of cracks. DESCRIPTION OF SYMBOLS 10... Laser light source, 12... Laser beam, 18... x-y moving device, 24... Optical semiconductor element, 26... Substrate, 28... Package, 30... Optical fiber , 32, 36... Nickel plating, 34... Gold plating, 38... Copper sheet, 40... Welded part. A diagram showing a laser welding device and a welding member used according to the present invention. Figure 1. Figure 40: A diagram showing the components of the optical transmission system package to be welded according to the present invention. Figure 4 A diagram showing a welded structure obtained according to the present invention. Diagram showing the welding structure of conventional technology Au atomic %→ Kan 3 Diagram Au-Cu system m diagram Fig. 5

Claims (1)

[Claims] A first member (26) made of copper-based metal plated with gold
, a second member (28) made of iron-based metal, and a sheet (38) of copper-based metal inserted between the first member and the second member; A welded structure characterized in that the member and the second member are welded together with the sheet of copper-based metal.