JP2001085733A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module for shielding outside noise and any inside noise, using simple constitution. SOLUTION: Rigid substrates 20 and 23-26 can be folded by allowing flexible substrates 27, 28, 29, and 30 for connecting the hard rigid substrates 20 and 23-26 to act as hinges. Then, a transmitting and receiving circuit is wrapped by a ground layer by folding the rigid substrates 20 and 23-26 to the transmitting and receiving circuit side, so that the transmitting and receiving circuit can be shielded. Thus, any inside noise can be prevented from being leaked to the outside, or any outside noise can be prevented from affecting the transmitting and receiving circuit. Then, the transmitting circuit including light emitting elements and the receiving circuit including photodetectors are separated by the folded multi-layer print board, and the receiving circuit and the transmitting circuit are wrapped by the ground layer, so that the transmitting circuit and the receiving circuit can be individually shielded and prevented from affecting each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module equipped with an optical transmitting / receiving circuit.

[0002]

2. Description of the Related Art An optical module is one of important optical components in an optical transmission system.

[0003] Today, with the increase in the amount of information to be transmitted, there has been a demand for higher speed transmission signals. The transmission signal is usually a digital signal composed of a combination of "H level" and "L level", and is either "H level", "L level", or a fall from "H level" to "L level". Alternatively, the information is represented by whether it rises from “L level” to “H level”. When the transmission speed of the transmission signal increases, the switching time between “H level” and “L level” becomes shorter, and particularly, immediately after rising from “L level” to “H level”, “H level” changes to “H level”. The portion falling to the "L level" forms a sharp pulse-like signal waveform. This sharp pulse-like signal contains a high frequency component. That is, when the transmission signal is speeded up, the optical module must detect the presence or absence of a signal having a high frequency component.

On the other hand, the frequency components of noise due to electromagnetic waves radiated from other substrates or peripheral devices include high frequency components. For this reason, the optical module is liable to malfunction due to erroneous recognition of noise as a transmission signal as the transmission signal becomes faster. Further, the optical module itself generates electromagnetic wave noise (internal noise), which may affect other substrates and peripheral devices.

[0005] That is, the environment in which the optical module is arranged is an environment in which the influence of the interaction of electromagnetic noise generated from circuits and devices is very likely to occur.

For this reason, it is essential to take measures against noise not only in the optical module but also in other substrates and peripheral devices.

In an optical module, an optical element for mutually converting an optical signal and an electric signal, an amplifier circuit for amplifying the electric signal, and a control circuit for controlling the signal are arranged on a substrate and packaged. Things.

Normally, an optical module package is composed of two parts, a top part for fixing a circuit board, and a cover part for covering the case part for protecting the inside.

An optical module package can be obtained by fixing the circuit board to the case and attaching the cover.

FIG. 6 is an external perspective view showing a conventional optical module and a cover. FIG. 7 is a sectional view taken along line AA when a cover is provided on the optical module shown in FIG.

Reference numeral 1 denotes a multilayer printed circuit board on which an optical receiving circuit (or optical transmitting circuit) including an integrated circuit 2, passive elements (chip resistors, chip capacitors) 3 and the like is mounted, and 4 denotes a photodiode (or laser diode) or the like. An optical element, 5 is a shield cover, 6 is a through hole into which the leg 7 of the shield cover 5 is inserted, and 8 is a multilayer printed circuit board 1.
, A conductor (ground layer) 9 in the inner layer of the multilayer printed circuit board 1, external electromagnetic wave noises 10 and 11,
Reference numeral 12 denotes solder.

In order to reduce the cost of an optical module for a transmission signal at a relatively low speed, no countermeasures against electromagnetic noise have been taken unless there is a problem in characteristics or the like. When a high-sensitivity optical receiver is required, a shield cover 5 is provided as a countermeasure against noise, and an input part of an optical receiving circuit which receives a small signal from a light-receiving element, for example, a photodiode which is weak against noise, is provided by the shield cover 5. Covering was done.

When a light emitting element of an optical transmission circuit, such as a laser diode, is switched by a large current, a shield cover is also provided on the optical transmission circuit that generates noise. As the operation speed of the laser diode increases and the sensitivity of the photodiode increases, noise suppression by a shield becomes indispensable.

In general, it is expected that the operation of the optical module will be stabilized and better characteristics will be obtained by bringing the shield cover into contact with the ground to reduce the impedance and stabilize the potential of the shield cover.

[0015]

However, in the conventional optical module shown in FIGS. 6 and 7, the connection between the shield cover 5 and the inner ground layer 9 is made through hole 6 (solder 1).
Only the connection according to 2). This is shield cover 5
Since a strong electrical connection between the optical module and the ground layer 9 cannot be obtained, the characteristics of the optical module cannot be improved.

Further, as shown in FIG.
The external noise 10 from above the surface on which is mounted can be shielded by the shield cover 5, but the external noise 11 from below is unprotected. That is, the shield cover 5 of the conventional optical module does not play a sufficient role of shielding against external noise.

Furthermore, since the light receiving (transmitting) circuit covered by the shield cover 5 of the conventional optical module is only a part of the circuit on the multilayer printed circuit board 1, the other circuit mounted on the multilayer printed circuit board 1 is not used. As for the electromagnetic noise 13 emitted from the circuit components, no shielding effect is exhibited.

Further, when the shield cover 5 is mounted, there is a problem that the number of parts and man-hours used in the optical module increase, and the cost of the optical module increases.

An object of the present invention is to solve the above-mentioned problems and to provide an optical module that can shield external noise and internal noise with a simple configuration.

[0020]

In order to achieve the above object, an optical module according to the present invention is provided with a plurality of rigid portions, a flexible portion connecting the rigid portions, and a common portion for the flexible portion and the rigid portion. An optical module having a transmission / reception circuit including an optical component and an electronic component mounted on a multilayer printed circuit board having a ground layer, wherein the transmission / reception circuit is wrapped in the ground layer by folding back a rigid portion.

In addition to the above configuration, the optical module of the present invention
The rigid circuit may be folded back to separate the transmitting circuit including the light emitting element and the receiving circuit including the light receiving element, and the receiving circuit and the transmitting circuit may be wrapped in the ground layer.

In addition to the above configuration, the optical module of the present invention
The multilayer printed circuit board may form a package case by folding back the rigid portion.

According to the present invention, the flexible portion connecting the hard rigid portions serves as a hinge, so that the rigid portion can be folded back. By turning this rigid part back to the transmitting / receiving circuit side, the transmitting / receiving circuit is wrapped in the ground layer, so that the transmitting / receiving circuit is shielded. As a result, the internal noise does not leak to the outside and the external noise does not affect the transmission / reception circuit.

When the folded multilayer printed circuit board separates a transmitting circuit including a light emitting element and a receiving circuit including a light receiving element, and the receiving circuit and the transmitting circuit are wrapped in a ground layer, the transmitting circuit and the receiving circuit are connected to each other. Since they are individually shielded, they do not affect each other.

When the folded multilayer printed circuit board forms a package case, the number of parts and man-hours are reduced,
Cost reduction and size reduction can be achieved.

[0026]

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

FIG. 1 is a development view showing an embodiment of the optical module of the present invention.

Reference numeral 20 denotes a rigid substrate as a multilayer rigid portion on which electronic components such as an integrated circuit 21 and passive elements (chip resistors and chip capacitors) 22 and optical elements 18 and 19 are mounted and serve as a bottom surface. 23 to 26 are rigid substrates 2
This is a rigid substrate for enclosing 0, and is formed to have substantially the same width (length) as a side adjacent to the rigid substrate 20. That is, the rigid board 24 is on one side (left side in the figure), the rigid board 25 is on the other side (right side in the figure), the rigid board 23 is a lid, and the rigid board 26 is the optical element 18 as an optical component.
9 is formed so as to have a back-to-back surface (hereinafter referred to as a “back surface”).

The rigid substrates 24, 25, 26 adjacent to the rigid substrate 20 are connected by flexible substrates 27, 28, 29 as bendable flexible portions, and the rigid substrate 23 adjacent to the rigid substrate 24 is connected by a flexible substrate 30. Have been.

Each of the flexible substrates 27 to 30 comprises a thin plate made of a bendable insulating resin (for example, polyimide), a conductor layer (for example, copper) laminated on the thin plate, and a resist layer laminated on the conductor layer. It was done.

The rigid boards 25 and 26 have flexible boards 31 to 34 respectively connected to sides other than the side to which the rigid boards are connected via the flexible boards.

The rigid substrates 23 and 24 are folded in the direction of arrow 100, the rigid substrate 25 is folded in the direction of arrow 101, and the flexible substrate 31 is folded in the direction of the arrow 23.
Is electrically connected to the conductive portion 35 with solder. The rigid substrate 26 is raised in the direction of the arrow 102, and the flexible substrate 32 is electrically connected to the conductive portion 36 of the rigid substrate 24 by soldering. An optical module package capable of transmitting and receiving light by electrically connecting the flexible substrate 33 to the conductive portion 35 of the rigid substrate 23 with solder and electrically connecting the flexible substrate 34 to the conductive portion 37 of the rigid substrate 25 with solder. A case 38 is configured.

Here, the conductive portions 35, 36 and 37 are connected to the ground layer. Note that the rigid substrate and the flexible substrate may be connected using a conductive adhesive instead of the solder.

The rigid boards 20, 23 to 26 and the flexible boards 27 to 34 are provided with a common ground layer, and constitute a multilayer printed board. For this reason, the package case 38 encloses the electronic component in the ground layer.

The rigid boards 20, 23 to 26 and the flexible boards 27 to 34 for forming the package case 38 can be connected in several ways. Any connection method may be used.

Here, as shown in FIG.
Is separate. When the package case 38 of the optical module is formed, before, during or after assembling the multilayer printed circuit board, the optical connector 39 is moved toward the optical element side of the package case 38 by an arrow 103.
Alternatively, the fixing claws 40 may be inserted into the fixing holes 41 to be attached. FIG. 2 is an assembly diagram of the optical connector of the optical module shown in FIG.

With such a configuration, the flexible boards 27, 28, and 29 connecting the rigid boards 20, 23, and 26 function as hinges, so that the boards 23, 26, and 26 can be folded back. it can. By turning these rigid substrates 23 to 26 back to the transmitting / receiving circuit side, the transmitting / receiving circuit is wrapped in the ground layer, so that the transmitting / receiving circuit is shielded. As a result, the internal noise does not leak to the outside, and the external noise does not affect the transmission / reception circuit.

FIG. 3 is a developed view showing another embodiment of the optical module of the present invention. The same reference numerals are used for members similar to those of the embodiment shown in FIG.

The difference from the embodiment shown in FIG. 1 is that the optical elements 18 and 19 are fixed to a rigid substrate 42 serving as a surface (hereinafter referred to as "front") on the optical connector side. It is connected to a rigid substrate 44 serving as a bottom surface via a flexible substrate 43.

As shown in FIG. 3, when the rigid board 42 is folded back to the side on which the electronic components are mounted, all six surfaces of the package case are shielded by the ground layer.

FIG. 4A is a developed view showing another embodiment of the optical module of the present invention, and FIG.
FIG. 4 is a partial cross-sectional view of the vicinity of the back surface after assembling the optical module illustrated in FIG.

The difference from the embodiment shown in FIG. 3 is that the upper side of the rigid substrate 26 serving as the back is fitted into the groove 45 of the rigid substrate 23a serving as the lid.

This optical module has a rigid substrate 42 on which the optical elements 18 and 19 are mounted and serves as a front surface, a rigid substrate 44 on which electronic components are mounted and serves as a bottom surface, a rigid substrate 25 which serves as one side surface, and the other side surface. Rigid substrate 2
4, a rigid substrate 26 serving as the back surface, a groove 45 in which the upper side of the back surface is fitted, and a fixing claw 40 for the optical connector 39.
A rigid substrate 23a, which is formed with a fixing hole 41 to be fitted with the rigid substrate and serves as a lid portion, and each rigid substrate 44, 24, 25, 2
Flexible substrates 27, 2 for connecting 6, 23a to each other
8, 29, and 43.

The rigid substrates 42, 24, 25, 26 are
Arrow 100 on the mounting surface side of the rigid substrate 44 on which the electronic components are mounted.
It is folded in the directions 101 and 102, and the rigid substrate 2
3a, the upper side of the rigid board 26 is fitted into the groove 45, and the fixing claw 40 of the optical connector 39 is inserted into the fixing hole 41.
Are fitted and soldered to a flexible substrate to obtain an optical module in which the entire six surfaces are covered by the ground layer.

FIG. 5 is a sectional view showing the vicinity of an optical element showing another embodiment of the optical module of the present invention.

The difference from the embodiment shown in FIG. 4 is that the transmitting circuit including the light emitting optical element 18 and the light receiving optical element 19
And a receiving circuit including the receiving circuit and a ground circuit.

On one side (left side in the figure) of the rigid substrate 20, a rigid substrate 24 serving as one side surface, a rigid substrate 23-1 serving as one lid, and a rigid substrate 46 serving as one partition plate are provided with the flexible substrate 22, 30 and 48 are connected respectively.

On the other side (right side in the figure) of the rigid substrate 20, a rigid substrate 25 serving as the other side surface, a rigid substrate 23-2 serving as the other cover, and a rigid substrate 47 serving as the other partition plate are provided with the flexible substrate 28. 49 and 50 are connected. In addition, both rigid substrates 23-1, 23-2
Is approximately half the width of the rigid substrate 20, and the width of the rigid substrates 46 and 47 is approximately equal to the width of the rigid substrates 24 and 25.

At the center of the rigid board 20, there are formed grooves 51, 52 into which the rigid boards 46, 47 fit.

The rigid substrates 24, 23-1, and 46 are folded back toward the optical element 18, and the rigid substrates 25, 23-2, and
7 is folded back to the optical element 19 side, and both rigid substrates 46, 4
7 are fitted into the grooves 51 and 52, respectively, to form a package case, so that the optical elements 18 and 19 are rigid substrates 20, 24, 23-1, 46, 25, and 23-.
2, 47 and flexible substrates 27, 28, 30, 4
8, 49, and 50 are respectively wrapped in the ground layers.

In the optical module shown in FIG. 5, since the transmission and reception circuits are individually shielded by the ground layer, the influence of noise between transmission and reception can be further reduced.

As described above, by assembling the rigid board and the flexible board, a package case is formed, and it is not necessary to separately make the external package case easy, so that the number of parts can be reduced and the cost can be reduced.

That is, according to the present invention, by wrapping the rigid substrate with another rigid substrate, the ground layer functions as a shield cover for the entire electronic component. As a result, the shielding effect is exerted against external noise from above, and the optical component is also sufficiently shielded from external noise from below, preventing the optical module from being adversely affected by electromagnetic noise. You. In addition, it is possible to suppress electromagnetic wave noise radiated from the optical module to the outside.

As described above, according to the present invention, (1) the electrical connection between the conductor layer of the flexible board and the ground layer of the rigid board is strengthened from the conventional point connection by through-hole to the line connection, and the shield cover and As a result, the electrical connection of the conductive layer becomes sufficient, so that the operation of the optical module is stabilized.

(2) Since the ground layer of the multilayer printed circuit board encloses the entire transmission / reception circuit, external noise from the vertical, horizontal, front and rear directions of the optical module is shielded, the receiving sensitivity is improved, and the optical module has good characteristics. Is obtained.

(3) Since the ground layer of the multilayer printed circuit board covers the entire transmitting and receiving circuit, electromagnetic wave noise as internal noise is shielded, and an optical module which does not affect other circuits or devices can be obtained.

(4) Side view enclosing the entire transmitting / receiving circuit
Since components can be mounted on the rigid substrate on the lid and the rear surface, the degree of freedom in circuit design inside the package is improved.

(5) Since the multilayer printed circuit board itself enclosing the entire transmission / reception circuit constitutes the package case of the optical module, the number of parts and cost can be reduced, and the size can be reduced.

[0059]

In summary, according to the present invention, the following excellent effects are exhibited.

An optical module that can shield external noise and internal noise with a simple configuration can be provided.

[Brief description of the drawings]

FIG. 1 is a developed view showing an embodiment of an optical module according to the present invention.

FIG. 2 is an assembly diagram of an optical connector of the optical module shown in FIG. 1;

FIG. 3 is a development view showing another embodiment of the optical module of the present invention.

4 (a) is a developed view showing another embodiment of the optical module of the present invention, and FIG. 4 (b) is a partial cross-sectional view near the back surface after assembling the optical module shown in FIG. 3 (a). It is.

FIG. 5 is a cross-sectional view near an optical element showing another embodiment of the optical module of the present invention.

FIG. 6 is an external perspective view showing a conventional optical module and a cover.

FIG. 7 is a sectional view taken along line AA when a cover is provided on the optical module shown in FIG. 6;

[Explanation of symbols]

 18, 19 Optical element 20, 23 to 26 Rigid board 27, 28, 29, 30 Flexible board

Continued on front page F term (reference) 2H037 AA01 BA02 BA11 DA03 DA06 DA15 DA33 DA35 DA40 5F041 AA31 DA20 FF14 5F088 BA03 BB01 JA05 JA20 5F089 AA01 AC23 AC26 CA11 FA10

Claims (3)

[Claims] An optical component and an electronic component are mounted on a multilayer printed circuit board having a plurality of rigid portions, a flexible portion connecting the rigid portions, and a ground layer provided in common with the flexible portion and the rigid portion. An optical module having a transmitting / receiving circuit mounted thereon, wherein the transmitting / receiving circuit is wrapped in the ground layer by folding back the rigid portion. 2. A transmission circuit including a light emitting element and a reception circuit including a light receiving element by partitioning the rigid portion, and the receiving circuit and the transmission circuit are respectively wrapped by the ground layer. 2. The optical module according to 1. 3. The optical module according to claim 1, wherein the multilayer printed circuit board forms a package case by folding the rigid portion.