JP2004079965A - Optical semiconductor module and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical semiconductor module which decreases the amount of Au used so as to reduce its cost. <P>SOLUTION: The optical semiconductor module is equipped with, a least, a hermetically sealed vessel provided with a ceramic terminal, leads, and optical semiconductors. Only the electrode of the ceramic terminal inside the hermetically sealed vessel and the leads are coated with Au. The parts coated with Au are shown by slashes in the figure. The electrode of the ceramic terminal and the leads are coated with Ni as an underlayer, and refractory metal, such as Pd, Pt, Mo or the like having a melting point of 1300°C or above is interposed between the Au coating and the Ni coating. The coatings of metals can be provided through electrolytic plating, electroless plating or deposition using a mask. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical semiconductor module containing an optical semiconductor element therein and a method for manufacturing the same.
[0002]
[Prior art]
In the field of information and communication, various semiconductor elements are generally used. However, in order to realize characteristics and performance required for each application, development of a mounting technique for these semiconductor elements is important. With the speeding up of information communication and the increase in the amount of information, the role played by optical communication is increasing. An optical semiconductor element used for optical communication is also usually used as an optical semiconductor module by being sealed in a sealing container suitable for the element in order to protect the element from an external environment and ensure electrical connection. With the remarkable development of the information communication field in recent years, there has been a strong demand in optical communication to secure high signal transmission reliability, to manufacture optical semiconductor modules at lower cost, and to provide them at low cost.
[0003]
By the way, conventionally, the hermetically sealed container of the optical semiconductor module has been subjected to Au plating at the end after assembling the bottom plate, the frame, the ceramic terminals and the like by silver brazing. For this reason, Au plating has been applied to portions of the surface of the container that do not substantially require Au plating. It is considered that the portions of the hermetically sealed container substantially requiring Au plating are specifically the electrode portions of the ceramic terminals and the leads. In the electrode portion of the ceramic terminal, a portion to which a lead is connected outside the container and a portion to which a wire is connected inside the container require Au plating in particular.
[0004]
The reason why the Au plating is applied to portions other than the substantially necessary portions of the above-described container is as follows. That is, the silver brazing in the final assembly step is exposed to a high temperature of about 700 ° C. in a hydrogen furnace. This is because Au sometimes reacts with the underlying Ni to form an alloy. When Au and Ni are alloyed in this way, subsequent wire bonding cannot be performed. In the case where a thermoelectric cooling element (TEC) is incorporated in the optical semiconductor module, Au plating is used for the purpose of preventing the surface of the hermetically sealed container from being oxidized at the brazing temperature when brazing the TEC. Had been given. In addition, since the window for assembling the optical fiber is usually brazed with an Au-Sn alloy, the portion of the container where the window is to be mounted also needs Au plating.
[0005]
[Problems to be solved by the invention]
For the above reasons, Au plating has been applied to the whole container after assembling the container so far, and there has been a problem that a large amount of Au is used and the cost of the optical semiconductor module is high.
[0006]
Therefore, an object of the present invention is to provide a low-cost optical semiconductor module by manufacturing an optical semiconductor module by applying an Au coating only to a minimum necessary portion of a hermetically sealed container.
[0007]
[Means for Solving the Problems]
The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have realized the following optical semiconductor module in which the Au plating position is limited. That is, the present invention is as follows.
[0008]
(1) An optical semiconductor module, comprising: a hermetically sealed container having at least a ceramic terminal; a lead; and an optical semiconductor, and only the electrode portion of the ceramic terminal in the hermetically sealed container, An optical semiconductor module, which is sequentially coated with a high melting point metal having a melting point of 1300 ° C. or higher and Au.
[0009]
(2) The optical semiconductor module according to (1), wherein the refractory metal is at least one selected from the group consisting of Pd, Pt, and Mo.
[0010]
(3) The optical semiconductor module according to (1) or (2), further comprising a thermoelectric cooling element.
[0011]
(4) A method for manufacturing an optical semiconductor module, comprising:
An electrode pattern is formed on a ceramic plate to form a ceramic terminal,
Plating Ni on the electrode,
Silver leads are soldered to the electrodes of the ceramic terminals,
The leaded ceramic terminal is sequentially coated with Ni, a high melting point metal having a melting point of 1300 ° C. or more, and Au,
The ceramic terminal with the lead, the bottom plate, and the frame are simultaneously silver-brazed to form a hermetically sealed container,
A method of manufacturing an optical semiconductor module in which at least an optical semiconductor is stored in the hermetically sealed container.
[0012]
(5) A method of manufacturing an optical semiconductor module including a thermoelectric cooling element, wherein an electrode pattern is formed on a ceramic plate to form a ceramic terminal,
Plating Ni on the electrode,
Silver leads are soldered to the electrodes of the ceramic terminals,
The leaded ceramic terminal is sequentially coated with Ni, a high melting point metal having a melting point of 1300 ° C. or more, and Au,
The ceramic terminal with the lead, the bottom plate, and the frame are simultaneously silver-brazed to form a hermetically sealed container,
Cleaning the hermetically sealed container in a hydrogen furnace,
A method for manufacturing an optical semiconductor module for storing an optical semiconductor by soldering a thermoelectric cooling element to the hermetically sealed container.
[0013]
(6) The method of manufacturing an optical semiconductor module according to (4) or (5), wherein the refractory metal is at least one selected from the group consisting of Pd, Pt, and Mo.
[0014]
(7) The method of sequentially covering Ni, the high melting point metal having a melting point of 1300 ° C. or more, and Au is any one of electrolytic plating, electroless plating, and vapor deposition using a mask (4) to (6). A method for manufacturing the optical semiconductor module according to claim 1.
[0015]
Hereinafter, the present invention will be described in detail.
In the present invention, in the hermetically sealed container of the optical semiconductor module, only the electrodes of the ceramic terminals and the leads are coated with Au. FIG. 1 is a perspective view showing an example of the optical semiconductor module of the present invention. In FIG. 1, the portion to be coated with Au is specifically indicated by hatching. FIG. 2 is a partial view of the optical semiconductor module of the present invention in which the optical semiconductor module has a built-in TEC, as viewed from above. FIG. 3 shows a cross section of FIG. Conventionally, Au of the total surface area of the hermetically sealed container × about 1.5 μm in thickness was required. However, as apparent from these figures, the module of the present invention can greatly reduce this, Can be provided at cost. Although the hermetically sealed container has an Au coating only on the electrode portion of the ceramic terminal, the substrate and the optical semiconductor element, which are manufactured separately from the hermetically sealed container, are plated with Au as necessary. It may be applied.
[0016]
Normally, the ceramic terminal is used by applying a Ni coating as a base. In the present invention, in order to prevent alloying between the Ni coating and the Au coating mentioned in the section of the prior art, a high melting point metal having a melting point of 1300 ° C. or more is used. And Au. As the high melting point metal, it is preferable to use at least one selected from the group consisting of Pd, Pt and Mo.
[0017]
To manufacture the optical semiconductor module of the present invention, first, a ceramic terminal is manufactured. That is, a wiring pattern is printed and baked on a ceramic plate using W paste to form an electrode. Ni is plated thereon by a normal electrolytic or electroless plating method. Thereafter, a lead is soldered to the electrode portion of the ceramic terminal at 750 ° C./820° C. in a hydrogen furnace. Ni, a high-melting-point metal and Au serving as a base are metallized on the ceramic terminals with leads, respectively, to form a coating of each metal. As the metallization method, besides the use of electrolytic or electroless plating, a method of vapor deposition using a mask may be used. Next, the ceramic terminal with the lead, the outermost layer of which is coated with Au, and the bottom plate, the frame and the like are simultaneously silver-brazed at 750 ° C./800° C. in a hydrogen furnace to complete the optical semiconductor hermetically sealed container. Here, once silver is brazed, Ni or Kovar is alloyed to further increase the melting point of the brazed part, thereby strengthening it. Finally, an element such as a TEC or an optical semiconductor is housed and sealed in this container to obtain an optical semiconductor module.
[0018]
The optical semiconductor module of the present invention is particularly useful when the module has a built-in TEC. In this case, after the hermetically sealed container is assembled as described above, the inside of the container is cleaned (cleaned) in a hydrogen furnace before use. The cleaning condition is preferably at 700 ° C. for 3 minutes or more. Further, instead of cleaning with hydrogen in the furnace, cleaning may be performed with an HCl solution. After cleaning, the hermetically sealed container is taken out of the hydrogen furnace and the TEC is soldered. The lower plate of the TEC is usually made of ceramics, and the surface of the TEC to be soldered may be plated with Ni or Au. On the other hand, the surfaces of the airtightly sealed containers facing each other are preferably plated with Ni. As the solder, PbSn, SnCuNi, or the like can be used. Further, Cu is usually plated with Au and used as an electrode of the TEC. Further, the optical semiconductor module of the present invention can be used by assembling a window. In this case, the window is attached by electric welding.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the optical semiconductor module of the present invention will be specifically described with reference to Examples and Comparative Examples.
[0020]
<Example 1>
As the hermetically sealed optical semiconductor container, the bottom plate, the frame, and the ceramic terminals were made of conventional materials. First, a wiring pattern of an electrode portion was printed on a ceramic terminal by screen printing and fired. Next, Ni plating was applied, a Kovar lead was fixed on this electrode using a carbon jig, and the lead was silver brazed at 750 ° C. in a hydrogen furnace. The ceramic terminals with leads were plated by electroless plating so that Ni had a thickness of 1.5 μm, Pd had a thickness of 1.0 μm, and Au had a thickness of 1.5 μm. Then, the ceramic terminal with the lead, the bottom plate of the container, and the frame were fixed using a carbon jig, and were simultaneously subjected to silver brazing at 750 ° C. in a hydrogen furnace. The work of silver brazing also serves as cleaning with hydrogen. Thereafter, the TEC was soldered and fixed to the completed hermetically sealed container to produce an optical semiconductor module of the present invention.
[0021]
In order to examine the connection strength of each part, a wire of an Au material having a diameter of 25 μm was wire-bonded to the lead of the hermetically sealed container completed as described above. When the bonding strength was measured by a normal pull test, the wire was not broken even with a load of 2.5 gf. Also, the bonding portion did not come off. The pull test is performed according to MIL-STD 883, Method 2011, and it is assumed that there is sufficient connection strength unless the breaking strength is 3 gf or more and the load is not cut under the load of 2.5 gf under screening conditions.
[0022]
<Comparative Example 1>
For comparison with Example 1, an optical semiconductor module was manufactured in the same manner as in Example 1 except that the leaded ceramic terminals were plated with only Ni and Au, and were not plated with Pd. Then, there were places where wire bonding could not be performed. A pull test similar to that in Example 1 was performed on a portion where bonding was barely performed. As a result, the bonding portion was detached with a load of 1 gf.
[0023]
<Example 2>
Example 2 Example 2 is the same as Example 1 except that Ni, Pt, and Au were vapor-deposited using a mask instead of performing electroless plating of Ni, Pd, and Au on the ceramic terminals with leads in Example 1. Thus, an optical semiconductor module was manufactured. Ni, Pt, and Au formed vapor deposition films with thicknesses of 1.5 μm, 1.5 μm, and 1.0 μm, respectively. A wire was bonded to this optical semiconductor module in the same manner as in Example 1, and a pull test was performed. As a result, in the case of Pt, the wire was cut at 3.1 gf, and the bonding portion did not come off.
[0024]
<Example 3>
In Example 3, an optical semiconductor module was manufactured in the same manner as in Example 1, except that Ni, Pd, and Au were vapor-deposited using a mask instead of performing electroless plating on the ceramic terminals with leads in Example 1. Manufactured. Ni, Pd, and Au formed deposited films with a thickness of 1.5 μm, 1.5 μm, and 1.0 μm, respectively. A wire was bonded to this optical semiconductor module in the same manner as in Example 1, and a pull test was performed. As a result, in the case of Pd, the wire was cut at 3 gf, and the bonding portion did not come off.
[0025]
<Example 4>
Example 4 Example 4 was performed in the same manner as in Example 1 except that Ni, Pd, and Au were electrolessly plated on the ceramic terminals with leads, but Ni, Mo, and Au were deposited using a mask. Thus, an optical semiconductor module was manufactured. Ni, Mo, and Au formed vapor deposition films with thicknesses of 1.5 μm, 1.5 μm, and 1.0 μm, respectively. A wire was bonded to this optical semiconductor module in the same manner as in Example 1, and a pull test was performed. As a result, in the case of Mo, the wire was cut at 3.1 gf, and the bonding portion did not come off.
[0026]
<Example 5>
In this embodiment, an optical semiconductor hermetically sealed container was assembled in the same manner as in the first embodiment. The container was then stored in a desiccator for one month. One month later, cleaning was performed at 700 ° C. for 30 minutes in a hydrogen furnace. The container was taken out of the hydrogen furnace, and TEC was joined inside the container with solder. A substrate on which a laser diode (LD) and the like were mounted was brazed on the TEC, and predetermined wiring was provided. Further, an optical fiber window was attached by electric welding, and a lid was brazed on the frame body to complete an optical semiconductor module. A vibration test was performed on the optical semiconductor module completed as described above. As a result, there was no difference in optical communication performance before and after the test. The vibration test was performed according to MIL-STD 883, Method 2007. The vibration conditions are as follows. In each of the orthogonal X, Y, and Z directions, vibration was applied while changing the frequency within a range of 20 to 2 kHz with 4 minutes as one cycle. The maximum acceleration was set to 20 G, and four cycles were performed.
[0027]
<Comparative Example 2>
For comparison with Example 5, an optical semiconductor module was completed in the same manner as Example 5, except that the cleaning process was not performed. When a vibration test was performed on this module in the same manner as in Example 5, the optical semiconductor module stopped operating halfway. Then, when the lid was removed and the inside was confirmed, the brazing portion of the TEC was loosened and shifted in position, and further, there was a place where the wired gold wire was coming off.
[0028]
【The invention's effect】
The optical semiconductor module of the present invention is provided by applying Au coating only to substantially necessary portions of the electrodes and leads of the ceramic terminals of the hermetically sealed container. Therefore, the amount of Au used can be significantly reduced as compared with the conventional case, and it can be provided at low cost. In the optical semiconductor module of the present invention, sufficient connection strength of each component can be obtained even when the Au coating is limited to those positions. Moreover, it was confirmed that the optical semiconductor module continued to operate stably even when external vibration was applied. Further, the optical semiconductor module of the present invention is particularly useful when a TEC is incorporated.
[Brief description of the drawings]
FIG. 1 is a perspective view of an example of an optical semiconductor module of the present invention.
FIG. 2 is a top view partially showing an example in which the optical semiconductor module of the present invention has a built-in TEC.
FIG. 3 is a sectional view of FIG. 2;

Claims (7)

An optical semiconductor module, comprising: a hermetically sealed container provided with at least a ceramic terminal; a lead; and an optical semiconductor, and only the electrode portion of the ceramic terminal in the hermetically sealed container; An optical semiconductor module, which is coated with a metal having a high melting point of not less than ° C and Au in order. 2. The optical semiconductor module according to claim 1, wherein the refractory metal is at least one selected from the group consisting of Pd, Pt, and Mo. The optical semiconductor module according to claim 1, further comprising a thermoelectric cooling element. A method for manufacturing an optical semiconductor module, comprising:
An electrode pattern is formed on a ceramic plate to form a ceramic terminal,
Plating Ni on the electrode,
Silver leads are soldered to the electrodes of the ceramic terminals,
The ceramic terminal with lead is coated with Ni, a high melting point metal having a melting point of 1300 ° C. or more and Au in order,
The ceramic terminal with the lead, the bottom plate, and the frame are simultaneously silver-brazed to form a hermetically sealed container,
A method of manufacturing an optical semiconductor module in which at least an optical semiconductor is stored in the hermetically sealed container. A method for manufacturing an optical semiconductor module including a thermoelectric cooling element,
An electrode pattern is formed on a ceramic plate to form a ceramic terminal,
Plating Ni on the electrode,
Silver leads are soldered to the electrodes of the ceramic terminals,
The ceramic terminal with lead is coated with Ni, a high melting point metal having a melting point of 1300 ° C. or more and Au in order,
The ceramic terminal with the lead, the bottom plate, and the frame are simultaneously silver-brazed to form a hermetically sealed container,
Cleaning the hermetically sealed container in a hydrogen furnace,
A method for manufacturing an optical semiconductor module for storing an optical semiconductor by soldering a thermoelectric cooling element to the hermetically sealed container. The method of manufacturing an optical semiconductor module according to claim 4, wherein the refractory metal is at least one selected from the group consisting of Pd, Pt, and Mo. 7. The method according to claim 4, wherein the method of sequentially covering Ni, a high melting point metal having a melting point of 1300 ° C. or higher, and Au is any one of electrolytic plating, electroless plating, and vapor deposition using a mask. A method for manufacturing an optical semiconductor module.

Images