JPH0464242A - Packaging construction of optical semiconductor device - Google Patents

Abstract

PURPOSE:To improve the ability of welding and cooling without surface treatment by constructing a two-layer carrier for an optical semiconductor device and by using a material having an advantage of weldability with the package. CONSTITUTION:A laminated carrier includes a Cu layer 9t on the device side and a Ni layer 9p on the package side. This carrier 9 is die-bonded with an optical semiconductor device 3 and placed on a package. With this treatment, part 9p of the carrier 9 facing the package 1 is securely and easily welded because the temperature of the part adeuately rises with little heat liberation due to low thermal conductivity of Ni. The surface bonded with the semiconductor device 3 is cooled down effectively due to high thermal conductivity of Cu. Conveniently enough, surface treatment such as plating by Au is not required for these materials because both Cu and Ni have high weldability with other materials.

Description

[Detailed Description of the Invention] (Summary) The present invention relates to a mounting structure for an optical semiconductor element, particularly a mounting structure suitable for mounting an optical semiconductor element in an optical transmission system package using optical fibers, which has been miniaturized in recent years. This is a carrier for mounting optical semiconductor elements and attaching them to a package, with the aim of realizing an inexpensive mounting structure for optical semiconductor elements that does not require surface treatment such as surface treatment, has excellent weldability and cooling performance, and is suitable for mounting optical semiconductor elements and attaching them to packages. The carrier has a two-layer structure on the package side and the optical semiconductor element side, the layer on the package side is made of a material that has excellent weldability with the package, and the layer on the optical semiconductor element side is It is made of a material with excellent thermal conductivity.

[Industrial application field]

The present invention relates to a mounting structure for an optical semiconductor element, and particularly to a mounting structure suitable for mounting an optical semiconductor element within an optical transmission system package using optical fibers, which has become increasingly compact in recent years.

[Conventional technology]

FIG. 4 is a sectional view showing the mounting structure of a conventional optical semiconductor element. Reference numeral 1 denotes a metal package, in which an optical semiconductor element 3 is mounted via a carrier 2. An optical fiber 4 passing through the package 1 is connected to the optical semiconductor element 3 . Further, a terminal 5 for electrical connection with the optical semiconductor element 3 is inserted. The insertion portions of the optical fiber 4 and the terminal 5 are hermetically sealed with low melting point glass or the like.

The optical semiconductor element 3 is bonded onto the carrier 2, and the carrier 2 is made of copper or a copper alloy having high thermal conductivity in consideration of the temperature rise of the optical semiconductor element 3.

Moreover, soldering is generally used to join the carrier 2 made of a Cu alloy and the package 1.

However, in soldering, since the solder is soft, the optical axis of the optical fiber 4 is easily misaligned due to creep.
There were problems with long-term reliability.

Therefore, as a fixing method instead of soldering, laser welding is used as shown in FIG. 2 is a carrier, which is covered with a gold plating layer 6. The package L side is also plated with gold if necessary. This carrier 2
and the iron-based alloy package 1 are bonded together at a high temperature of 1000° C. or higher by irradiating laser light.

[Problem to be solved by the invention]

Since there are many places to be bonded, both the carrier 2 and the package 1 are subjected to surface treatment such as Au plating, which has excellent bonding properties. Therefore, in the normal welding method, a small amount of Au is mixed into the welded part, significantly increasing the solidification temperature range of the molten metal, and as a result, a crank 8 is generated in the welded part 7 during solidification. Alternatively, since the material of the carrier 2 is Cu, which has high thermal conductivity, heat is radiated from the welding part 7 and the temperature does not rise, making it impossible to obtain a sufficient penetration depth, resulting in a decrease in welding strength. A problem arose.

Conventionally, as a method to prevent this cracking and obtain a sufficient penetration depth, the gold-plated layer at the welded area was mechanically ground to prevent the gold that would cause cracks from getting into the welded area. There are methods such as chemical stripping, methods such as partial plating and then welding, and new methods such as Cu-Ni-
Conventionally, an Au sheet was inserted and welded.

However, these methods not only require a step to remove the Au plating (but also have drawbacks such as corrosion due to etching solution residue and reduced dimensional accuracy of parts when etching or grinding is performed to remove the Au plating). was occurring.

Furthermore, the method of inserting the Au-Ni-Cu sheet also requires additional steps such as insertion and positioning, which hinders automation and lacks productivity.

The technical problem of the present invention is to address these problems and to realize an inexpensive mounting structure for optical semiconductor elements that does not require surface treatment such as gold plating, has excellent weldability and cooling ability, and is inexpensive. purpose.

(Means for Solving the Problems) (1) FIG. 1 is a side view illustrating the basic principle of the mounting structure of an optical semiconductor element according to the present invention. 9 is a carrier according to the present invention, which has a two-layer structure. That is,
A layer 9p on the package l side and a layer 9t on the optical semiconductor element 3 side
It consists of two layers.

Moreover, the layer 9p on the package l side is made of a material that has excellent weldability with the package 1, and the layer 9p on the optical semiconductor element 3 side
t is made of a material with excellent thermal conductivity.

(2) The layer 9t on the optical semiconductor element 3 side is made of copper (Cu) or a copper alloy, and the layer 9p on the package 1 side is made of nickel (Ni) or a nickel alloy.

The two-layer structure of the layer 9p made of nickel or a nickel alloy and the layer 9t made of copper or a copper alloy is integrally manufactured by a powder metallurgy method.

[Effect]

(1) The carrier 9 of the present invention is N9p on the package 1 side.
Since the carrier 9 and the package 1 are made of a material that has excellent weldability with the package 1, welding between the carrier 9 and the package 1 can be performed reliably and easily.

Further, since the layer 9t on the side of the optical semiconductor element 3 is made of a material with excellent thermal conductivity, heat from the optical semiconductor element 3 is effectively dissipated.

(2) Usually, iron-based materials such as SUS are often used for the package 1. Therefore, the layer 9p of the carrier 9 on the package 1 side is made of Ni or a Ni alloy, and the layer 9t of the three optical semiconductor devices is made of Cu or a Cu alloy. As a result, the carrier 9 and the package 1 are joined by welding the package 1 made of Ni or Ni alloy and the iron-based alloy, and the optical semiconductor element 3 and the carrier 9 are joined by welding with the package 1 made of Ni or Ni alloy and iron-based alloy.
This results in bonding between the u or Cu alloy and the optical semiconductor element 3.

Fe-based alloy package 1 and Ni or Ni alloy have excellent weldability, and since Ni has low thermal conductivity, heat does not easily escape, a sufficiently high welding temperature can be obtained, and treatments such as Au plating are not required. It can be welded reliably.

On the other hand, since the layer 9t on the side of the optical semiconductor element 3 is made of Cu, it has insufficient cooling ability for the optical semiconductor element 3.

In particular, when a two-layer carrier 9 having a layer 9p made of nickel or a nickel alloy and a layer 9t made of copper or a copper alloy is produced using a powder metallurgy method, the layer 9t on the optical semiconductor element 3 side and the package 1 The composition between the layer 9p and the side layer 9p gradually changes. Therefore, the bonding strength between the two layers 9p and 9t becomes sufficient.

[Example] Next, how the mounting structure of an optical semiconductor element according to the present invention is actually implemented will be explained using an example. A layer 9t on the optical semiconductor element 3 side and a layer 9ρ on the package 1 side shown in FIG.
From the viewpoint of bonding strength between the two, it is desirable that the composition changes gradually. In order to obtain a gradual change in composition, it is suitable to produce the material using, for example, a powder metallurgy method.

That is, Ni powder and Cu powder are filled into a mold so that the composition gradually changes, and the mold is compacted and then sintered.

Next, a method for manufacturing a carrier using a powder metallurgy method will be illustrated.

As shown in FIG. 1, when forming a carrier structure in which a layer 9t on the optical semiconductor element 3 side made of Cu is laminated on a layer 9p on the package 1 side made of Ni, the purity 99 % and -325 mesh, and Ni powder with a purity of 99% and -325 mesh were placed on the lower side, respectively, to produce a green compact of 5xlOxlOrIlIm). This green compact is sintered at a temperature of 900°C and a sintering time of 1 hour.
It was sintered in vacuum under the following conditions.

When molding is performed by powder metallurgy in this manner, the composition between the layer 9t on the optical semiconductor element 3 side and the layer 9p on the package 1 side changes sequentially, as shown in FIG. That is, the ratio of copper to nickel is gradually changing.

The optical semiconductor element 3 is placed on the carrier 9 produced in this way.
die bonding and package this carrier 9 (
42 alloy, Ni surface treatment). That is, the abutting portion of the package 1 and carrier 9 is irradiated with a laser from the end face, and the area around the carrier 9 is irradiated with a laser beam.
Spont welding was performed at about 6 locations. The laser used for welding was a Nd-YAG laser, and the welding conditions were a pulse width of 2 ms.
, defocus amount Omm, irradiation energy 5 to 20 J per pulse, lens focal length 100 mm, shielding gas is Ar, gas pressure 1.5 kg/c11N, gas flow rate 30
1/rRin.

As a result, the joint between the carrier 9 and the package 1 is melted to a deep depth on both the carrier 9 side and the package 1 side, so that it exhibits a good welded shape as shown in FIG.
No cracks were observed that occurred during the joining of the Au-plated surface-treated members as shown in the figure.

That is, the portion 9p of one example of the package of the carrier 9 is
Ni with low thermal conductivity (thermal conductivity: 0.21 cal/
g・deg), the heat can be dissipated ((temperature rises sufficiently and welding can be performed easily and reliably).

Further, the surface to be bonded to the optical semiconductor element 3 is made of Cu having high thermal conductivity (thermal conductivity: 0.94 cal/g-deg
), high cooling performance can be achieved. Moreover,
Both Cu and Ni have high bonding properties with the bonding member, so Au
No surface treatment such as plating is required.

Die bonding was performed between the optical semiconductor element 3 and the carrier 9 using an Au-based brazing material. As a brazing material for gold thread, A
uGe, AuSi, etc. are used. The surface of the carrier 9 on which the optical semiconductor element is mounted may be plated with Au.

Note that the optical semiconductor element 3 may be a light emitting element or a light receiving element.

〔Effect of the invention〕

As described above, according to the present invention, the carrier 9 on which the optical semiconductor element 3 is mounted has a two-layer structure, and the layer 9p on the package 1 side is made of a material that has excellent weldability with the package 1. Therefore, the welding between the package 1 and the carrier 9 is ensured, and cracks etc. do not occur (
, sufficient welding strength can be obtained. Furthermore, since the layer 9t on the side of the optical semiconductor element 3 is made of a material with excellent thermal conductivity, the heat generated from the optical semiconductor element-3 is effectively dissipated.

Furthermore, if the layer 9t on the optical semiconductor element 3 side is made of copper or a copper alloy, and the layer 9p on the package 1 side is made of nickel or a nickel alloy, and if they are molded by powder metallurgy, even though it has a two-layer structure, , a carrier with excellent strength can be obtained. Since no special treatment is required, it can be manufactured at low cost.

The package 1 also does not necessarily require surface treatment, and even if surface treatment is performed, Ni plating can be substituted for the conventional expensive Au plating, which is economically advantageous and enables cost reduction.

[Brief explanation of drawings]

FIG. 1 is a side view illustrating the basic principle of the mounting structure of an optical semiconductor device according to the present invention, FIG. 2 is a diagram showing compositional changes in a carrier with a two-layer structure, and FIG. 3 is a diagram showing the relationship between the carrier and package of the present invention. FIG. 4 is an enlarged sectional view showing a welded part. FIG. 4 is a sectional view showing a conventional mounting structure of an optical semiconductor element. FIG. 5 is an enlarged sectional view showing a conventional welded part between a carrier and a package. In the figure, 1 is the package, 2 is the conventional key rear, and 3 is the package.
is an optical semiconductor element, 4 is an optical fiber, 5 is a terminal, 6 is Au
A plating part, 7 a welding part, 8 a crank, 9 a carrier according to the present invention, 9t a layer on the optical semiconductor element side, and 9p a layer on the package side, respectively. Basic Principles of the Present Invention Fig. 1 Patent Applicant Fujitsu Limited Sub-Agent Patent Attorney Yasushi Fukushima Fig. 2

Claims (1)

[Claims] 1. A carrier (9) for mounting an optical semiconductor element (3) and attaching it to the package (1), wherein the carrier (9) is connected to the package (1) side and the optical semiconductor element. It has a two-layer structure with the package (1) side and the package (1) side layer (9p).
It is made of a material that has excellent weldability with optical semiconductor devices (3
) side layer (9t) is made of a material with excellent thermal conductivity. 2. In the carrier (9) according to claim 1, the layer (9p) on the package (1) side is made of nickel or a nickel alloy, and the layer (9t) on the optical semiconductor element (3) side is made of copper or a copper alloy. A mounting structure for an optical semiconductor element, wherein the two-layer structure consisting of nickel or a nickel alloy and copper or a copper alloy is integrally manufactured by a powder metallurgy method.