JPH1184180A - Packaging substrate of optical module and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the shorting between printed circuit board surface wiring and the wiring on the surface of the packaging substrate of an optical module by providing the rear surface of the packaging substrate with a stepped part. SOLUTION: A hole part (a notched part 8 after dicing) utilizing the (111) face of Si is formed by anisotropic etching on the Si substrate 1 cut out at the (100) face. A groove part (the stepped part 9 after dicing) utilizing the (111) face of the Si is formed on the rear surface 12 by the anisotropic etching. In such a case, both of the rear surface 12 and front surface 11 of the Si substrate 1 are covered with oxidized films 4 and Au electrodes 5 are formed thereon through notched parts 8. The substrate 1 is diced along the dicing line passing the groove part on the rear surface 12 thereof, by which the packaging substrate 10 of the optical module is manufactured. As a result, the direct soldering of the rear surface 12 to the printed circuit board is made possible and the distance between the cutting surface 7 and the printed circuit board is made larger by the groove part on the rear surface 12 of the packaging substrate 10, by which the shorting is substantially prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of a mounting board in an optical module and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, there is a document disclosed in “Document name: 1995, IEICE General Conference Lecture Papers, page 1 of Electronics 1”. According to this prior art, as shown in FIG. 5, a back-illuminated PD 10 is mounted on a mounting substrate 101 on which an Au electrode 102 for supplying power to a PD (light receiving element) is formed.
3. The optical fiber 104 was mounted.

[0003]

However, in the above-mentioned structure of the mounting board of the conventional optical module, when this is mounted on a printed circuit board or the like, it is mounted on a DIP type or butterfly type alumina package, and the distance between the Au electrodes is reduced. Wire bonding was required, and there were problems in terms of members and man-hours.

An object of the present invention is to provide a mounting board for an optical module and a method for manufacturing the same, which can eliminate the above problems, facilitate mounting of the optical module on a printed circuit board or the like, and perform reliable connection. And

[0005]

In order to achieve the above object, the present invention provides: [1] a mounting board for an optical module on which an optical semiconductor element is mounted and which performs optical communication via an optical fiber; In this case, a step is provided which is separated from the rear surface.

[2] A mounting board of an optical module on which an optical semiconductor element is mounted and which performs optical communication via an optical fiber, is provided with cutouts having inclined surfaces extending from the front surface to the back surface at both ends. An electrode is provided for conducting between the front surface and the back surface via the inclined surface. [3] In a mounting board of an optical module on which an optical semiconductor element is mounted and which performs optical communication through an optical fiber, a stepped portion separated from the back surface in a peripheral portion, and a cutout portion having an inclined surface extending from the front surface to the back surface at both ends. And an electrode for conducting between the front surface and the back surface through the inclined surface of the notch.

[4] In a method of manufacturing a mounting board of an optical module on which an optical semiconductor element is mounted and performing optical communication via an optical fiber, a groove is formed around the mounting board before dicing, and the groove is formed along the groove. A step of forming a step portion separated from the back surface by dicing, forming a hole having an inclined surface at an end of the mounting substrate before dicing, forming a cutout having an inclined surface by dicing to divide the hole into two,
Forming an electrode that connects the front surface and the back surface through the inclined surface of the notch.

[5] In the method for manufacturing an optical module mounting board according to the above [4], the groove portion may be made of silicon (1).
11) It is manufactured by anisotropic etching using a surface. [6] The method for manufacturing a mounting board for an optical module according to [4], wherein the hole having the inclined surface is manufactured by anisotropic etching using a silicon (111) plane.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view of a mounting substrate of an optical module according to a first embodiment of the present invention before dicing, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG.
FIG. 7 is a sectional view taken along line BB of FIG. As shown in these figures,
On the Si substrate 1 cut out from the (100) plane, (1)
11) Hole 2 using surface [notch 8 after dicing
(See FIG. 2)] is formed by anisotropic etching. Here, although not particularly shown, the side on which the PD and the optical fiber are mounted is referred to as a front surface 11, and the other side is referred to as a back surface 12. On the back surface 12, a groove 3 using the (111) plane of Si [step 9 after dicing (see FIG. 2)]
Are formed by anisotropic etching.

The back surface 12 and the front surface 11 of the Si substrate 1 are both covered with an oxide film 4, on which an Au electrode 5 is formed via a hole 2 [notch 8]. Then, a dicing is performed along a dicing line 6 passing through the groove 3 on the back surface 12 of the Si substrate 1 to manufacture a mounting substrate 10 (hereinafter simply referred to as a mounting substrate) of the optical module.

Back surface 1 of mounting substrate 10 of this optical module
By forming the Au electrode 5 on the second substrate 2, the back surface 12 can be directly soldered to a printed board (not shown).
The distance between the printed board and the cut surface 7 is increased, and short-circuiting is difficult. That is, a short circuit between the wiring on the printed circuit board and the wiring on the surface of the mounting substrate 10 of the optical module can be prevented.

As described above, according to the first embodiment, since the electrodes are provided on the back surface of the mounting board of the optical module, the back surface can be directly soldered to the printed circuit board, which has been conventionally required. , Mounted on a DIP type or butterfly type alumina package, eliminating the need for wire bonding between electrodes, simplifying both members and man-hours,
The price can be reduced.

Further, by providing a step (groove) on the back surface of the mounting substrate of the optical module, the step (groove) is formed.
If there is no printed circuit board, the distance between the printed circuit board and the cut surface, which is only a distance corresponding to the thickness of the oxide film having a thickness of several microns, becomes large, and short-circuiting becomes difficult. In this case, by setting the depth of the step (groove) on the rear surface of the mounting substrate to several hundred microns, the distance between the printed substrate and the cut surface 7 can be made several hundred microns.

Means for providing an oxide film on the cut surface to prevent a short circuit can be considered.
After the cutting by dicing, further processing is required, whereas the processing of the step (groove) is (11) of silicon.
1) Since the etching using the surface is used, it can be formed simultaneously with the optical fiber alignment V-groove and the like.
Mass production by batch processing is also possible, and cost reduction can be achieved.

Further, since the notch (hole) formed using the (111) plane of Si is formed by anisotropic etching, the side surface of the notch (hole) is not vertical,
Since it has an inclined surface of about 55 degrees, it is possible to form an Au electrode that conducts between the front and back surfaces by vapor deposition or the like. Next, a second embodiment of the present invention will be described.

FIG. 4 is a cross-sectional view (a cross-sectional view corresponding to line AA in FIG. 1) of a mounting substrate of an optical module according to a second embodiment of the present invention. In this embodiment, the front surface and the back surface of the first embodiment are formed in a reversed shape. As shown in this figure, a notch 28 (a hole before dicing) using the (111) plane of Si is formed on the mounting substrate 21 from the back surface 12 by anisotropic etching. Also, back 1
In No. 2, a step portion 29 (a groove portion before dicing) using the (111) plane of Si is formed by anisotropic etching.

The back surface 12 and the front surface 11 of the mounting substrate 21 are both covered with an oxide film 24, and an Au electrode 25
Are formed. Further, the Au electrode 25 allows the back surface 12 to be directly soldered to a printed board (not shown), and the stepped portion 2 of the back surface 12 of the mounting board 21 is formed.
9 (grooves) increases the distance between the printed circuit board and the cut surface 27, making short-circuiting difficult.

As described above, according to the second embodiment, since the Au electrode is provided on the back surface of the mounting substrate, the back surface can be directly soldered to the printed circuit board. Since it is mounted on a mold or butterfly type alumina package and there is no need to wire bond between electrodes, it is possible to simplify both members and man-hours, and to reduce the cost.

Further, by providing a step (groove) on the back surface of the mounting substrate of the optical module, when there is no step (groove), the distance corresponding to the thickness of the oxide film having a thickness of several microns is provided. The distance between the printed circuit board and the cut surface, which are only separated from each other, increases, and it is difficult to cause a short circuit. By setting the depth of the step (groove) to several hundred microns, the distance between the printed board and the cut surface can be made several hundred microns.

In order to prevent a short circuit, a means of providing an oxide film on a cut surface is conceivable.
Generally, further processing is required after cutting by dicing. On the other hand, in this embodiment, the step portion (groove portion) is processed by etching using the (111) plane of silicon. Enables mass production and lower prices.

Further, since the notch (hole) using the (111) plane of Si is formed by anisotropic etching, the side surface of the notch (hole) is not vertical but has a slope of about 55 degrees. Therefore, it is possible to form an Au electrode that conducts between the front and back surfaces by vapor deposition or the like. Further, Si (111)
Since the notch (hole) and step (groove) using the surface are etched from the back surface, the area of the surface on which the PD and the optical fiber are mounted can be made large, so that there is an advantage that the chip size can be small. is there.

Needless to say, it can be used as a mounting substrate for an LD (semiconductor laser). In addition,
In the above embodiment, the step portion (groove portion) using the (111) plane of Si is formed in the mounting substrate. However, the groove portion may be formed in the mounting substrate by cutting with a dicing saw.

Further, the present invention is not limited to the above-described embodiment, and various modifications are possible based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0024]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first aspect of the present invention, the step (groove) is provided on the back surface of the mounting substrate of the optical module. The distance between the printed circuit board and the cut surface, which is separated only by a distance corresponding to the thickness of the oxide film, is increased, so that a short circuit between the wiring on the printed circuit board and the wiring on the surface of the mounting substrate of the optical module can be prevented.

(2) According to the second aspect of the present invention, since the electrodes are provided on the back surface of the mounting substrate of the optical module,
The back surface can be directly soldered to the printed circuit board, and it is mounted on a DIP type or butterfly type alumina package, which was required in the past, eliminating the need for wire bonding between electrodes. And
The price can be reduced.

(3) According to the third aspect of the present invention, a short circuit between the wiring on the printed circuit board and the wiring on the surface of the mounting board of the optical module is prevented, and both the members and the man-hours are simplified, thereby reducing the cost. Can be achieved. (4) According to the fourth aspect of the present invention, the short circuit between the wiring on the printed circuit board and the wiring on the surface of the mounting board of the optical module is prevented by a simple manufacturing method, and both the members and the man-hours are simplified. Thus, the cost can be reduced.

(5) According to the fifth aspect of the present invention, since the step (groove) is processed by anisotropic etching utilizing the (111) plane of silicon, the V-groove for aligning the optical fiber and the like are formed. At the same time, formation is possible, mass production by batch processing becomes possible, and cost reduction can be achieved. (6) According to the invention as set forth in claim 6, the notch (hole) is formed by anisotropic etching using the (111) plane of Si, so that the side surface of the notch (hole) is formed. Is not vertical but has an inclined surface of about 55 degrees, so that it is possible to form an Au electrode that conducts between the front and back surfaces by vapor deposition or the like.

[Brief description of the drawings]

FIG. 1 is a plan view of a mounting substrate of an optical module according to a first embodiment of the present invention before dicing.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a cross-sectional view (a cross-sectional view corresponding to line AA of FIG. 1) of a mounting substrate of an optical module according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a conventional PD module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 Hole part 3 Groove part 4,24 Oxide film 5,25 Au electrode 6 Dicing line 7,27 Cut surface 8,28 Notch part 9,29 Step part 10,21 Optical module mounting substrate 11 Front surface 12 Back surface

Claims (6)

[Claims] 1. A mounting board for an optical module, on which an optical semiconductor element is mounted and which performs optical communication via an optical fiber, comprising a stepped portion separated from a back surface in a peripheral portion. 2. A mounting board for an optical module on which an optical semiconductor element is mounted and which performs optical communication via an optical fiber, comprising: a notch having inclined surfaces extending from a front surface to a rear surface at both ends; A mounting board for an optical module, comprising: an electrode that conducts between a front surface and a back surface via a surface. 3. A mounting board for an optical module on which an optical semiconductor element is mounted and performs optical communication via an optical fiber,
(A) a stepped portion that is separated from the back surface in the peripheral portion, and (b) a cutout portion having an inclined surface extending from the front surface to the back surface at both ends,
A mounting board for an optical module, comprising: an electrode that conducts between a front surface and a back surface through an inclined surface of the notch. 4. A method of manufacturing a mounting board for an optical module on which an optical semiconductor element is mounted and performing optical communication via an optical fiber, comprising: (a) forming a groove around the mounting board before dicing; (B) forming a hole having an inclined surface at the end of the mounting substrate before dicing, and dicing the hole into two notches having an inclined surface; Forming an electrode, and forming an electrode that connects the front surface and the back surface through the inclined surface of the cutout portion. 5. The method according to claim 4, wherein the groove is formed of (111) silicon.
A method of manufacturing a mounting board for an optical module, wherein the mounting board is manufactured by anisotropic etching using a surface. 6. The method for manufacturing a mounting board for an optical module according to claim 4, wherein the hole having the inclined surface is manufactured by anisotropic etching using a (111) plane of silicon. Manufacturing method of module mounting board.