JPH03184384A - Optical module submount and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a thin, high reliability optical module submount by mounting on an electrode the surface of which is patterned for driving an optical semiconductor device and mounting the optical semiconductor device on an electrode on the side surface of which is patterned. CONSTITUTION:An electrode pattern of a double layer structure using an Ni film on the base of a submount substrate 1 and an Ni film on an electrode is formed on the top and the side of the submount substrate 1, and further protruded solder bumps 3 are formed on the side surface, and by fusing the solder bumps 3 are joined with Au electrodes 5 of an LED array 4. Further, beveling 9 is applied to an edge part extending perpendicularly to the electrode pattern 2 formed on the surface and the side surface of the submount substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a submount for an optical module used for transmission and reception of optical communications, etc., and a method of manufacturing the same.

[Conventional technology]

Optical communications include optical semiconductor devices such as optical fibers, semiconductor lasers (LDs), light emitting diodes (LEDs), and photodiodes (PDs), as well as active and passive devices such as optical switches, optical modulators, optical isolators, and optical waveguides. The range of applications is expanding due to improved performance and functionality. In recent years, as the demand for transmitting more information has increased, parallel transmission, which performs data transmission between computer terminals, exchanges, and large computers in parallel in real time, has been attracting attention. As a device that satisfies this function, there is a parallel optical transmission module that integrates a plurality of light emitting or light receiving elements and a plurality of optical fibers. Usually, a light emitting (light receiving) element is a plurality of LEDs, LDs, or PDs arranged monolithically on the same semiconductor substrate.
An array of optical fibers is used, and an optical fiber array in which a plurality of optical fibers are arranged in one direction is used. Among them, the LED array is made of Si or Af, which also serves as a heat sink.
It is mounted on an N submount. A parallel transmission optical module having such a configuration is described in a paper by Mr. Nagahori in the 1989 Spring National Conference Preliminary Lectures of the Institute of Electronics, Information and Communication Engineers, number B-735, pages 4-111.

FIG. 3 is a perspective view of a submount on which an LED array of a general parallel transmission optical module is mounted. On the upper surface of the submount substrate 11, electrode patterns 12 are formed alternately from left and right toward the center, and solder electrodes 23 are formed on the electrode patterns 12 in the center.

FIG. 4 shows a general coaxial type parallel transmission optical module, and the broken line in the figure is cut out so that the internal elements can be seen. The LED array 14 is mounted on the surface of the submount board 11, and the connection part with the optical fiber is fixed on the board 21 with a hollow cylindrical sleeve 26 substantially aligned with the center axis of the LED array 14. . Optical fiber array 24
The metal ferrule 25 holding the LED array 14
After adjusting the position so that the emitted light can efficiently enter the sloop 26, the sloop 26 is fixed to the sloop 26 by soldering or welding.

[Problem to be solved by the invention]

Since optical modules are usually built into printed circuit boards, there is a need to make them thinner. Further, since it is necessary for optical modules to shorten signal lines in response to higher speeds, it is desirable that a driving IC for driving the LED array be incorporated inside the optical module. However, in the above configuration, the LED array and drive IC are mounted on the surface of the same submount board, and the optical fibers are arranged so that the input end face of the optical fiber is on top of it, so the height of the optical module is high. Therefore, there was a major problem in that it was difficult to integrate it onto a printed circuit board.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a submount that can easily reduce the thickness of an optical module.

[Means to solve the problem]

The present invention is a submount for an optical module on which an optical semiconductor element such as a light emitting or light receiving element is mounted. The structure is characterized in that an electronic circuit for driving the optical semiconductor element is mounted on the electrode, and the optical semiconductor element is mounted on the patterned electrode on the side surface.

Furthermore, in the above-mentioned optical module submount in which an optical semiconductor element is mounted on a side surface and a semiconductor element for driving the optical semiconductor element is mounted on a front surface, an edge portion where the surface of the optical module submount substrate and the side surface intersect Reliability will be improved if the structure is chamfered.

The manufacturing method of the present invention for manufacturing a submount for an optical module on which an optical semiconductor element and a semiconductor element for driving the optical semiconductor element are mounted includes chamfering and polishing an edge portion where the surface and the side surface of the submount substrate intersect. a polishing step, a film forming step of forming a thin film on the surface, the side surfaces and the edge portions, and a patterning step of patterning the thin film and forming an electrode pattern on the surface, the side surfaces and the edge portions. , a coating step of forming a polymer material on the side surface, a dam forming step of forming a hole in the polymer material on the electrode pattern, and a bump forming the solder bump on the electrode pattern exposed from the dam. a forming step, a wet back step of heating the substrate to make the solder bumps into a spherical or mountain shape, and mounting an electronic circuit for driving an optical semiconductor element or signal processing on the surface of the substrate, The structure is characterized in that it includes at least the step of bonding the optical semiconductor element to the electrode on the side surface.

[Effect]

The submount of the present invention has L on the surface of the submount substrate.
Since a drive IC for driving the ED array is mounted and an LED array is mounted on the side surface, the input end surface of the optical fiber can be placed on the side surface side of the submount. Therefore, the submount and the optical fiber can be arranged on a plane, and the shape of the optical module can be made into a plane type. This facilitates making the optical module thinner. On the other hand, by chamfering the edge portion where the surface and side surface intersect, chipping of the edge portion can be prevented. Therefore, by forming electrode patterns on the front surface, side surfaces, and edge portions, the LED array and the driving IC can be easily connected without disconnection of the electrode patterns.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIGS. 1(a) and 1(b) show an embodiment of the present invention.
(a) is a perspective view of a submount equipped with an LED array and a drive IC, and (b) is a cross-sectional view taken along line A-A' in (a). For example, AI is an excellent material! A two-layer electrode pattern 2 is formed on the surface and side surfaces of the submount substrate 1 using a C film as the base layer and a Ni film as the electrode. 3, and the solder bump 3 and the Au electrode 5 of the LED array 4 are fused and bonded.The solder bump 3 is rectangular in size 150 x 600 μm and has a mountain shape with a height of 50 μm, and has a pitch. is L
The length is 250 μm, which is the same as the bit of ED array 4. A dam 6 made of, for example, photosensitive polyimide resin is provided around the solder bump 3 to serve as a mask during solder electroplating and to prevent solder from flowing out during fusion. A drive IC 7 is fixed to the surface of the submount substrate 1 by die bonding, and is connected to the electrode pattern 2 with a bonding wire 8. Although not shown, the submount substrate 1 is fixed in a module package with leads, and the leads and the electrode patterns 2 are connected with bonding wires 8.

FIG. 2 shows another embodiment of the present invention, and in FIG. 9 has been applied. The other parts are the same as the embodiment shown in FIG.

Next, the manufacturing process of the submount substrate of the present invention will be explained in detail. First, the dimensions are, for example, 50 x 9 x 6.5 openings.
A polishing process is performed in which the edges of the top surface and both side surfaces of the substrate are polished with a C chamfer of 0.5 mm, and then a base layer of, for example, Cr is applied by vacuum evaporation using approximately 1,000 vacuum evaporations over the entire top surface and both side surfaces of the substrate. A film formation process is performed to plate Ni with a thickness of 2 μm, and then a patterning process is performed to form an electrode pattern 2 on the substrate using photolithography. Similar to the patterning process, solder bumps are formed using photolithography. A dam forming step is performed in which a dam 6 is provided on the electrode forming the electrode 3 so that Ni is exposed. Next, a bump forming process is performed in which a 30 μm thick solder is formed on the electrode pattern 2 exposed in the dam 6 by electroplating.Flux is then applied to the solder bump portion and heated to approximately 200°C on a hot plate. A wet-back process is performed to heat and melt the bump to make it mountain-like.

To mount the LED array on the submount, flux is applied to the solder bumps 3 of the submount substrate 1, and the LED array 4 is placed on the solder bumps 3 in alignment with each Au electrode 5. Next, the solder bumps 3 and the Au electrodes 5 of the LED array 4 are melted by heating to about 200°C on a hot plate. At this time, the self-alignment effect due to the surface tension of the solder bumps aligns the solder bumps to within 10 μm. Accuracy is achieved.

The drive IC is mounted by bonding to the upper surface of the submount substrate 1 using conductive paste and by wire bonding to the electrode pattern 2.

〔Effect of the invention〕

As explained above, according to the present invention, the input end face of the optical fiber is arranged on the side surface side of the submount board 1 on which the LED array 4 is mounted.
and optical fibers can be provided on a flat surface. This has made it easier to make the optical module thinner. Further, by providing a chamfer 9 at the edge portion where the front surface and side surface of the submount substrate 1 intersect, chipping of the edge portion can be prevented, thereby reducing disconnection of the electrode pattern 2. As a result, a thin and highly reliable optical module submount can be realized.

In addition, in this example, the LED array was explained, but
The present invention is not limited to this, and may be, for example, an LD array or a PD array, or may be a single LED, LD, or PD.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are diagrams of a submount showing an embodiment of the present invention equipped with an LED array and a driving IC; FIG. 1(a) is a perspective view, and FIG. 1(b) is a ), Figure 2 is a perspective view of a chamfered submount showing an embodiment of the present invention, and Figure 3 is a conventional submount mounted with an LED array of a general parallel transmission optical module. A perspective view of the mount, and FIG. 4 is a perspective view of a general coaxial type parallel transmission optical module. 1.11... Submount board, 2.12... Electrode pattern, 3... Solder bump, 4, 14... LED
Array, 5... Au electrode, 6... Dam, 7... Drive ICl3... Bonding wire, 9... Chamfering, 23... Solder electrode, 24... Optical fiber array,
25... Ferrule, 26... Sleeve.

Claims (1)

[Claims] 1. A rectangular parallelepiped-shaped submount substrate is provided with patterned electrodes on the front and side surfaces thereof, and an electronic circuit for driving the optical semiconductor element is mounted on the patterned electrodes on the surface. A submount for an optical module, characterized in that the optical semiconductor element is mounted on the patterned electrode on the side surface. 2. In the submount for an optical module according to claim 1, wherein an optical semiconductor element is mounted on a side surface and a semiconductor element for driving the optical semiconductor element is mounted on a front surface, an edge portion where the front surface and the side surface of the submount substrate intersect A submount for optical modules characterized by chamfering. 3. A polishing step of chamfering and polishing the edge portion where the surface and side surface of the submount substrate intersect; a film forming step of forming a thin film on the surface, the side surface, and the edge portion; patterning the thin film; a patterning step of forming an electrode pattern on the surface, the side surfaces and edge portions; a coating step of forming a polymeric material on the side surfaces; a dam forming step of forming holes in the polymeric material on the electrode pattern;
a bump forming step of forming the solder bumps on the electrode pattern exposed from the dam; a wet back step of heating the submount substrate to make the solder bumps into a spherical or mountain shape; and a step of forming the solder bumps on the surface of the substrate. 1. A method of manufacturing a submount for an optical module, the method comprising at least the step of mounting an electronic circuit and bonding an optical semiconductor element to an electrode on a side surface of the substrate.