JP2000040834A - Production of multichip module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix an optical semiconductor chip and a light receiving chip, with high accuracy, at specified positions on a heat sink previously secured with an optical fiber. SOLUTION: An optical semiconductor chip 2 is temporarily fixed at the optical semiconductor chip position 2c on a heat sink 2 by means of a temporary fixing member 3 and a light receiving chip is fixed temporarily at the light receiving chip position on the heat sink 2 by means of a temporary fixing member. The temporarily fixed optical semiconductor chip position 2c and the light receiving chip are then secured simultaneously by fusion solder material 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing a multi-chip module utilizing passive alignment.

[0002]

2. Description of the Related Art A laser chip module, which is a type of a multi-chip module, guides a laser beam output from a semiconductor laser chip to the outside of a heat sink via an optical fiber, and transmits a monitor laser output from the laser chip to a monitor chip. Designed to guide. Therefore, in order to align the optical fiber with the laser beam, it is necessary to align the laser chip and the optical fiber with excellent accuracy. Conventionally, alignment of an optical fiber is performed by outputting a laser beam from a laser chip fixed to a heat sink, adjusting the position of the optical fiber on the heat sink, and fixing the optical fiber at a position where the optical power guided to the optical fiber is maximized. . This method, called active alignment, can precisely align the optical fiber with the laser chip, but it takes a long time to perform alignment, resulting in poor productivity and the disadvantage of producing laser chip modules at low cost. there were.

[0003] In recent years, a method called passive alignment has been proposed to address the above-mentioned problems. In this method, a V-shaped groove is formed in advance on a silicon substrate serving as a heat sink, an optical fiber is dropped into the V-shaped groove and fixed, and then an alignment mark formed on the laser chip and the heat sink is image-recognized. The light emitting section for outputting the laser beam of the laser chip fixes the laser chip to a reference point on the heat sink immediately before the cross section of the core of the optical fiber.

More specifically, as shown in FIG. 5A, a heat sink 13 having a heat sink metal film 10 and further having a solder material 11 formed thereon is set in a bonding apparatus (not shown). I do. On the other hand, a light emitting portion 6 for outputting a laser beam is provided inside, and a metal layer 1 for a solder material is provided on the surface.
The laser chip 1 provided with the heat sink 13
Installed above At this time, the light emitting section 6 is located above the reference point 6 which is the center of the core of the optical fiber (not shown) into which the laser beam is input. Next, as shown in FIG. 5B, the laser chip 1 is
The solder material 11 is heated and cooled while pressing the solder material 11 against the heat sink 13 and applying a predetermined load. Thus, the laser chip 1 is fixed with the solder material 11 at a position where the light emitting point 6 coincides with the reference point 7, that is, at a position where a laser beam can be sufficiently supplied to the optical fiber.

After fixing the laser chip to the heat sink, the monitor chip is fixed with a solder material at a position on the heat sink where a laser beam can be sufficiently input. That is, when the laser chip and the monitor chip are fixed by passive alignment, solder melting is performed twice on the same heat sink.

[0006]

However, passive alignment has the following problems. Since the heat sink is heated when fixing the monitor chip, the solder material already fixing the laser chip is re-melted and re-condensed. At this time, since the capillary holds down the monitor chip and does not apply an appropriate load to the laser chip, the surface tension of the remelted solder material causes
The laser chip is fixed while floating from the solder material.

Further, depending on the state of the heat sink metal film and the oxidation state of the metal film, the re-melted and re-solidified solder material partially penetrates into the heat sink, and the heat sink partially repels the solder material. At this time, the surface tension of the solder material becomes uneven, the surface of the solder material is inclined, and the laser chip 1 is fixed to be inclined as shown in FIG.

In the state described above, the light emitting point 6 of the laser chip is fixed in a state shifted from the reference point 7.
In such a state, the laser beam cannot be properly guided to the optical fiber.

Further, when a solder material having a characteristic of reducing its volume by melting and solidifying is used, a non-uniform void may be generated between the metal film for the solder material and the solder material.
Such a gap hinders the heat generated in the laser chip from being dissipated to the heat sink. In particular, if such a gap is generated immediately below the light emitting portion, which is the largest heat source of the laser chip module, it adversely affects the high-temperature operation of the laser chip module.

[0010] The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide:
(1) A method for manufacturing a multi-chip module in which an optical semiconductor chip and a light-receiving chip are fixed at predetermined positions with excellent accuracy on a heat sink to which an optical fiber is fixed in advance, and (2) a fusion-bonded solder part having excellent heat dissipation. To provide a method for manufacturing a multi-chip module having the following.

[0011]

In order to solve the above-mentioned problems, a method of manufacturing a multi-chip module according to the present invention comprises the steps of temporarily fixing a laser chip and a monitor chip on the same heat sink and then connecting the chips to a solder material. And fix simultaneously. Specifically, the method for manufacturing a laser chip module according to the present invention includes an optical semiconductor chip that oscillates and outputs a laser beam or amplifies and outputs an input laser beam, and receives the output laser beam. One or more light-receiving chips and an optical fiber connected to the optical semiconductor chip are fixed on the same heat sink in a predetermined positional relationship, and the optical fiber is fixed to the predetermined position on the heat sink and A method of manufacturing a multi-chip module for fixing an optical semiconductor chip and the light-receiving chip at the predetermined position on the heat sink, wherein the intensity of the laser beam input from the optical fiber or output to the optical fiber is substantially reduced. Temporarily fix the optical semiconductor chip on the optical semiconductor chip position on the heat sink An optical semiconductor chip temporary fixing step of temporarily fixing the light receiving chip with a temporary fixing material at a position of the light receiving chip on the heat sink where the intensity of the laser beam input to the light receiving chip is substantially maximized. A light receiving chip temporary fixing step, and a chip fixing step of fixing the temporarily fixed optical semiconductor chip and the temporarily fixed light receiving chip with a solder material, wherein the optical semiconductor chip and By simultaneously fixing the light receiving chip with a solder material, displacement on the heat sink is prevented.

In the method of manufacturing a multi-chip module, it is preferable that the temporary fixing is performed with a pressure-bonded metal or resin adhesive in order to temporarily fix the chip with sufficient strength.

Further, in the method for manufacturing a multi-chip module, the laser chip has a metal film for a solder material on a fixed side surface thereof and a metal film for a temporary fixing material separated from the metal film for a solder material. On the other hand, the heat sink has, on its fixed side surface, a metal film for solder material corresponding to the metal film for solder material on the laser chip side and a metal for temporary fixing material corresponding to the metal film for temporary fixing material on the laser chip side. It preferably has a membrane.

Further, in the method of manufacturing a multi-chip module, the metal film for the solder material may be provided on the fixed side of the laser chip in order to reduce a void generated in the solder material and improve the heat radiation efficiency of the laser chip module. On the surface, the laser chip is formed at a portion where the temperature rises by outputting the laser beam, while a solder material is provided on the heat sink side so as to cover the metal film for the solder material. The solder material is melted and solidified, and the volume of the solder is smaller than that of the solder material between the metal film for the solder material on the laser chip side and the metal film for the solder material on the heat sink side. It is preferable to form a soldering portion.

Further, in the method of manufacturing a multi-chip module, the heat sink metal film for the solder material on the heat sink and the temporary fixing material are provided to prevent the molten excessive solder material from melting the temporary fixing portion. It is preferable that a solder material pool groove into which the excess melted solder material flows is formed between the heat sink metal film and the heat sink metal film.

Further, in the method of manufacturing a multi-chip module, in order to reduce voids generated in the solder material, the pressure-bonded metal is formed on at least a surface thereof with a gold or gold alloy layer. It is preferable that the solder material is PbSn or InPb whose volume does not change before and after melting.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 First, referring to FIG.
The laser chip module 20 according to the first embodiment of the present invention will be described. The laser chip module 20 shown in FIG. 1 is a laser chip 1 which is an optical semiconductor chip with respect to the optical fiber 16 by passive alignment.
Is performed. Specifically, the laser chip module 20 is provided with the V
After fixing the optical fiber 16 in the groove 17, the laser chip 1 provided with the light emitting section 6 for outputting a laser beam is temporarily fixed with the crimp metal 3, the monitor chip 15 is temporarily fixed with the crimp metal 3, The chips 1 and 15 are fixed with a fusion solder material 4. Laser chip 1 is optical fiber 16
In order to supply the laser beam to the monitor chip 15 as much as possible, as shown in FIG.
The optical fiber 16, the laser chip 1, and the monitor chip 15 are arranged such that the front light emitting unit 6b of the optical fiber 16 and the center of the core of the optical fiber 16 face each other, and the rear light emitting unit 6b of the laser chip 1 faces the light receiving unit 15a of the monitor chip 15. Is arranged. In this embodiment, a laser chip is used as an optical semiconductor chip. However, the present invention is not limited to this, and other optical semiconductor amplifier chips such as an optical semiconductor amplifier chip for amplifying and outputting an input laser beam are provided. An optical semiconductor chip may be used.

Laser chip position 2c on heat sink 2
FIG. 2 shows a state in which the laser chip 1 is fixed to the optical fiber 16 and the light emitting section 6 is aligned with the reference point 7, which is the center of the core of the optical fiber 16. As shown in FIG. 2, the laser chip 1 includes a metal film 1a for a solder material that covers the surface immediately below the light emitting portion 6 of the laser chip 1 and a metal film 1b for a compression metal that covers both end surfaces of the laser chip 1. On the other hand, at the laser chip position 2c on the heat sink 2, a solder material metal 2a corresponding to the solder material metal film 1a and a compression metal film 2b corresponding to the compression metal film 1b are formed. Have been. Further, the fusion-bonded solder material 4 is a metal film for a solder material 1a, 2a.
And the press-bonded metal 3 is sandwiched between the press-bonded metals 1b and 2b. The metal film 2 for the solder material on the heat sink 2
The solder material pool groove 9 is provided in a region between the metal film 2a and the metal film 2b.

Next, a method of fixing the laser chip 1 and the monitor chip to the heat sink 2 will be described. As shown in FIG. 3 (a), on the fixed side surface of the laser chip 1 having the light emitting portion 6 inside, the metal film 1a for the solder material covering the lower portion of the light emitting portion 6 and the metal film 1a for the solder material are separated. And a metal film 1b formed of gold or a gold alloy on the surface of the metal film 1b.
a is provided.

On the other hand, at the laser chip position 2c on the heat sink 1, the solder metal film 2a corresponding to the solder metal film 1a, and the pressure-bonded metal film separated from the solder metal film 2a. 1b, and a solder pool groove 9 is formed between the metal film for solder 2a and the metal film 2b for metal for solder. Next, a compression metal 3b made of gold or a gold alloy is provided on the metal film 2b for a compression metal, and a solder material that is gold tin (AuSn) solder is provided on a portion of the metal film 2a for a solder material sandwiched between the solder pool grooves 9. 4a is placed.

Next, as shown in FIG.
Is positioned directly above the reference point 7, and the laser chip 1 is positioned on the heat sink 2 such that the metal film 1a for the solder material and the metal film 2a for the solder material and the metal 3a and the metal 3b are opposed to each other. 2c.

Subsequently, as shown in FIG. 3 (b), the capillary 1 is pressed so that the metal 3a and the metal 3b are in contact with each other.
2, the laser chip 1 is pressed against the heat sink 2 by applying a predetermined load, and the heat sink 2 is heated to a temperature equal to or lower than the melting point of the solder material 4 so that the pressure-bonded metal 3a and the pressure-bonded metal 3
b and the laser chip 1 by heat-pressing.
Temporarily fixed with sufficient strength to the upper laser chip position 2c.

Further, the monitor chip is similarly temporarily fixed to the monitor chip position (not shown) on the heat sink at which the laser beam can be supplied to the monitor chip with a sufficient strength by a pressure bonding metal.

The laser chip 1 and the monitor chip may be temporarily fixed to the heat sink 2 by using a resin adhesive instead of the above-mentioned press-bonded metal.

After the laser chip and the monitor chip are temporarily fixed to the same heat sink, the heat sink is heated to a temperature equal to or higher than the melting point of the solder material, so that the solder material interposed between the laser chip and the heat sink, and the monitor chip and the heat sink are heated. The solder material interposed therebetween is melted at the same time, the solder material is cooled and solidified, and both chips are fused and fixed to a heat sink. At this time, the surplus molten solder flows into the solder material accumulation groove 9. Thus, the step of fixing the monitor chip and the laser chip on the same heat sink is completed. The receiving photodiode chip can be fixed at a position where the intensity of the laser beam supplied from the optical fiber is maximized by using the same method as described above.

Since the laser chip 1 and the monitor chip are temporarily fixed to the heat sink with sufficient strength, even if the heat sink is heated when the solder material is melted, the two chips will not be heated by the heat stress. There is no deviation from a predetermined position.

The heat sink 2 has a groove 9 for collecting the solder material.
Are provided, and the melted AuSn solder 4
The molten AuSn solder 4 is prevented from melting the compression metal made of gold or gold alloy.

As the solder material, PbSn solder or InPb solder may be used instead of the AuSn solder described above. When such a material is used for the solder material, the fused metal of PbSn or InPb does not dissolve the crimped metal made of gold or a gold alloy, so that it is not necessary to form the solder material pool groove 9. Further, since the volume of the PbSn solder or InPb solder does not decrease before and after melting, no gap is generated between the solder material metal film and the molten solder portion.

Embodiment 2 FIG. Next, a laser chip module according to a second embodiment of the present invention will be described.
Except for fixing the laser chip to the heat sink,
The laser chip module according to the second embodiment is the same as the laser chip module according to the first embodiment.
Hereinafter, a method for fixing a laser chip according to the second embodiment will be described with reference to FIGS.

First, as shown in FIG. 4 (a), a light emitting section 6 whose temperature rises by outputting a laser beam is provided on the surface of a laser chip 1 having a light emitting section 6 for outputting a laser beam. A metal film for a solder material 1c covering only the lower portion and a metal film for a compression metal 1b covering both ends of the laser chip 1 separated from the metal film for a solder material 1c are formed. A compression metal 3a made of gold or gold plating is provided on the film 1b.

On the other hand, at the laser chip position 2c of the heat sink 2, a solder metal film 2d corresponding to the solder metal film 1c, and the pressure-bonded metal film separated from the solder metal film 2d. A metal film for solder material 2b corresponding to 1b is formed, and a solder pool groove 8 is provided between the metal film for solder material 2d and the metal film for press-bonded metal 2b. Subsequently, a solder material 4a, which is gold tin (AuSn) solder, is placed on a portion of the heat sink 2 sandwiched by the solder pool grooves 8,
While the solder material 4a completely covers the solder metal film 2d,
A heat sink side compression metal 3b made of gold or gold plating is provided on the metal film 2b for the compression metal.

Next, as shown in FIG.
Is directly above the reference point 7, the metal film for solder material 1c and the metal film for solder material 2d face each other, and the crimp metal 3a and the crimp metal 3b
After the laser chip 1 is installed above the laser chip position 2c of the heat sink 2 so that the laser chip 1 faces the laser chip 1, the laser chip 1 is temporarily fixed to the heat sink 2 with sufficient strength as in the first embodiment. Temporarily fix the monitor chip to the heat sink.

After the monitor chip and the laser chip are temporarily fixed to the heat sink, the solder material interposed between the laser chip and the heat sink and the solder material interposed between the monitor chip and the heat sink are melted and solidified.
At this time, since the solder material has a property of being compatible with the metal material, the dissolved solder material is concentrated between the solder material and the metal films 1c and 2d for the solder material. Therefore, as shown in FIG. 4B, the fusion solder portion 4b is formed only immediately below the light emitting portion 6.

With the structure as in the second embodiment,
After the solder material is melted, the volume of the solder material 4 decreases according to the area of the heat sink metal film 2d and the laser chip metal film 1c. No voids are generated.

In this way, by providing the solder material without a gap immediately below the light emitting portion of the laser chip, heat generated from the light emitting portion of the laser chip can be efficiently radiated.

In the first and second embodiments described above, the method of precisely fixing two semiconductor chips, ie, a laser chip and a monitor chip, on the same heat sink has been described. It is also possible to fix three or more semiconductor chips.
Therefore, it is also possible to fix the receiving semiconductor chip at a position on the heat sink where the laser beam supplied from the optical fiber is maximized.

[0038]

According to the method of manufacturing a multi-chip module of the present invention, after an optical semiconductor chip and a monitor chip are temporarily fixed at predetermined positions on a heat sink, the two chips are simultaneously fused to the predetermined positions with a solder material. Since they are fixed, both chips can be accurately fixed to the same heat sink.

In the method of manufacturing a multi-chip module according to the present invention, the laser chip and the monitor chip can be temporarily fixed with a sufficient strength by using the pressure-fixed metal or the resin adhesive for the temporary fixing portion.

According to the method of manufacturing a multi-chip module of the present invention, a metal film for a solder portion and a metal film for a temporary fixing material are provided on the surface of a laser chip, while a metal film for a solder portion and a metal film for a temporary fixing material are provided on the heat sink side. Is provided, the fixing of the laser chip to the heat sink becomes more accurate.

According to the method of manufacturing a multi-chip module of the present invention, the heat dissipation of the multi-chip module can be improved by providing a solder material without voids directly below the light-emitting portion of the laser chip. Improve operating characteristics.

According to the method of manufacturing a multi-chip module of the present invention, by providing a solder pool groove on a heat sink, it is possible to prevent the melted excess solder material from being collected by the solder pool groove and to melt the press-bonded metal portion. In addition, the positioning accuracy of the laser chip on the heat sink is improved.

According to the method for manufacturing a laser chip module of the present invention, the solder material is made of PbSn or InPb whose volume does not change before and after melting, thereby preventing the generation of voids in the solder material and allowing the laser chip module to operate at a high temperature. Improve characteristics.

[Brief description of the drawings]

FIG. 1 shows a laser chip module according to the present invention.

2 shows a cross-sectional view of the laser chip module of FIG. 1 along the line II-II.

FIG. 3 shows a method of fixing a laser chip to a heat sink in the method of manufacturing a laser chip module according to the first embodiment of the present invention, wherein (a) places the laser chip at a predetermined position on the heat sink; FIG. 4B shows a step of temporarily fixing the laser chip to the heat sink.

FIG. 4 shows a method of fixing a laser chip to a heat sink in a method of manufacturing a laser chip module according to a second embodiment of the present invention, wherein (a) places the laser chip at a predetermined position on the heat sink; FIG. 4B shows a step of temporarily fixing the laser chip to the heat sink.

FIG. 5 shows a method of fixing a laser chip to a heat sink in a method of manufacturing a laser chip module according to the related art, wherein (a) shows a step of installing the laser chip at a predetermined position on the heat sink; b) shows a step of temporarily fixing the laser chip to the heat sink.

FIG. 6 shows a laser chip module according to the prior art, showing a laser chip shifted from a predetermined position on a heat sink.

[Explanation of symbols]

Reference Signs List 1 laser chip, 1a metal film for solder material, 1b
Metal film for pressure-bonded metal, 1c Metal film for solder material, 2 heat sink, 2a Metal film for solder material, 2b Metal film for pressure-bonded metal, 2c Laser chip position, 2d Heat sink metal film for solder material, 4 Fused solder part, 4a Solder material, 4b fused solder part, 6 light emitting part, 7 reference point, 20 laser chip module.

Claims (6)

[Claims] An optical semiconductor chip for oscillating and outputting a laser beam or amplifying and outputting an input laser beam, one or more light receiving chips for receiving the output laser beam, and the optical semiconductor chip An optical fiber connected to the chip is fixed on the same heat sink in a predetermined positional relationship, and the optical fiber is fixed to the predetermined position on the heat sink, and the optical semiconductor chip and the light receiving chip are connected to the heat sink. A method of manufacturing a multi-chip module to be fixed at a predetermined position, wherein an optical semiconductor chip position on the heat sink at which the intensity of the laser beam input from the optical fiber or output to the optical fiber is substantially maximum. An optical semiconductor chip temporary fixing step of temporarily fixing the optical semiconductor chip with a temporary fixing material, A light receiving chip temporary fixing step of temporarily fixing the light receiving chip with a temporary fixing material at a light receiving chip position on the heat sink at which the intensity of the laser beam input to the light receiving chip is substantially maximized; A chip fixing step of fixing the optical semiconductor chip and the temporarily fixed light receiving chip with a solder material. 2. The method for manufacturing a multi-chip module according to claim 1, wherein said temporary fixing is performed with a metal or resin adhesive which is pressed. 3. The laser chip has a metal film for a solder material on a fixed surface thereof and a metal film for a temporary fixing material separated from the metal film for solder material, while the heat sink is provided on the fixed surface of the laser chip. A metal film for a solder material corresponding to the metal film for a solder material on the laser chip side and a metal film for a temporary fixing material corresponding to the metal film for a temporary fixing material on the laser chip side. 3. The method for manufacturing a multichip module according to 1 or 2. 4. The metal film for a solder material is formed on a portion of the fixed surface of the laser chip where the temperature rises when the laser chip outputs the laser beam, and the solder material is formed on a heat sink side. A solder material is provided so as to cover the metal film for soldering, and in the chip fixing step, the solder material is melted and solidified to form a gap between the metal film for solder material on the laser chip side and the metal film for solder material on the heat sink side. 4. The method for manufacturing a multi-chip module according to claim 3, further comprising forming a fused solder portion having a smaller volume than the solder material and being in close contact with the two metal films. 5. A solder material pool groove into which excess molten solder material flows is formed between the solder material metal film and the temporary fixing material metal film on the heat sink. The method for manufacturing a multi-chip module according to claim 3 or 4, wherein: 6. The method according to claim 1, wherein the pressed metal has at least a surface formed of a gold or gold alloy layer, and the solder material is PbSn or InPb. A method for manufacturing a multichip module according to one of the above.