JP4968311B2 - Optical data link - Google Patents

Description

  The present invention relates to an optical data link used for optical communication.

  The optical data link for optical communication is equipped with an optical module that incorporates a photoelectric conversion element such as a laser diode (LD), and a rigid circuit board that is connected to an external circuit board and has an LD drive function and the like. It consists of Currently, there is an increasing demand for efficient use of optical fibers and miniaturization of optical data links, and the following are attracting attention as optical modules used for optical data links.

That is, bidirectional communication is possible with a single-core optical fiber, and single-core bidirectional (BiD: Bi) in which semiconductor components such as an LD, a photodiode (PD), and a transimpedance amplifier are housed in the same package. -Directional) optical module (see, for example, Patent Documents 2 and 3). As disclosed in Patent Documents 2 and 3, having a lead pins of both for reception in the same side, is smaller coaxial single fiber BiD optical module of attention has been paid and for transmission.

  In the case of such a coaxial type module, since a large number of lead pins are drawn out from the same side surface, the interval between the lead pins is narrow. Therefore, crosstalk is likely to occur between transmission / reception signals, and reception sensitivity may be reduced. Further, in the above-mentioned optical module, it is difficult to control the impedance of the lead pin, and the optical output waveform may be deteriorated at a high speed operation of 2.5 Gbps or more.

In order to prevent such characteristic deterioration, the lead pin is shortened as much as possible, and a flexible printed circuit board (FPC: Flexible Printed) is used for electrical connection between the rigid circuit board and the lead pin as disclosed in Patent Document 1. Circuits) is considered as an effective measure. The electrical connection between the FPC and the lead pin is performed by soldering the land provided around the through hole and the lead pin with the lead pin passing through the through hole provided in the FPC. .

JP 2007-48822 A JP 2008-90019 A JP 2008-90093 A

  However, when the FPC is used, if the lead pins are arranged at a narrow interval as in the single-core BiD optical module disclosed in Patent Documents 2 and 3, the lead pin through-holes 101 in the FPC 100 are connected to the above-mentioned optical pins as shown in FIG. Since the lands 102 come into contact with each other when they are provided at the same interval as the lead pins in the module, it is not possible to form the lands 102 having a sufficiently large size. For this reason, the reliability of solder connection may be impaired. For example, it is not possible to guarantee a good connection when the environmental temperature changes abruptly because, for example, a solder fillet cannot be formed.

  In view of the above situation, the present invention connects a small coaxial BiD optical module having both transmission and reception lead pins on the same surface and a rigid circuit board by FPC. An object of the present invention is to provide an optical data link with high reliability of connection between a lead pin of a BiD optical module and an FPC.

In order to solve the above-described problems, an optical data link of the present invention includes a first lead pin group and a light receiving element that are equipped with a light emitting element that transmits signal light and a light receiving element that receives other signal light, and is electrically connected to the light emitting element. A bi-directional optical module having a second lead pin group electrically connected to the element; a rigid circuit board on which a transmission circuit and a reception circuit are mounted; a first flexible board connecting the first lead pin group and the transmission circuit; The second lead pin group and the second flexible substrate for connecting the receiving circuit, wherein the first lead pin group and the second lead pin group are respectively the first flexible substrate and the second flexible substrate. through both, electrically connected to the first flexible substrate through without first lead pin group are electrically connected to the second flexible substrate Second lead pin group wherein the penetrating be electrically connected to the second flexible board without electrically connecting to the first flexible substrate.

  It is preferable that an insulating spacer through which at least one lead pin belonging to the first lead pin group or the second lead pin group passes is disposed between the first flexible circuit board and the second flexible circuit board. In addition, the first lead pin group or the second lead pin group is positioned between the first flexible circuit board and the second flexible circuit board on the lead pin of either the first lead pin group or the second lead pin group. It is preferable that a stopper is provided so as not to come into contact with the second flexible circuit board.

  It is preferable that at least one of the first flexible circuit board and the second flexible circuit board has a ground pattern formed on the surfaces facing each other, and the first flexible circuit board and the second flexible circuit board are respectively It is also preferable that the first lead pin group and the second lead pin group overlap with each other in an electrically connected portion, and other portions extend in different directions.

  According to the optical data link of the present invention, since a land having a sufficiently large size can be formed on the FPC, a solder fillet can be formed. Therefore, the reliability of the connection between the lead pin of the BiD optical module and the FPC can be improved. it can.

It is a figure explaining an example of the optical data link of this invention. It is a figure explaining the single core BiD optical module of FIG. It is a figure which shows the mode of the edge part by the side of the 1-core BiD optical module of 1st FPC and 2nd FPC of FIG. It is a figure explaining the other example of the optical data link of this invention. It is a figure explaining the other example of the optical data link of this invention. It is a figure explaining the other example of the optical data link of this invention. It is a figure explaining 1st FPC used for the optical data link of the example of FIG. It is a figure explaining the subject of this invention.

The outline of the optical data link of the present invention will be described with reference to FIGS. In the following, only the parts related to the main part of the present invention will be shown and described.
For example, as shown in FIG. 1, the optical data link of the present invention is configured such that a coaxial single-core BiD optical module (hereinafter abbreviated as an optical module) 1 and a rigid circuit board 2 are electrically connected by an FPC 3 in a housing not shown. As described later, the configuration of the FPC 3 is characteristic. The electrical connection between the optical module 1 and the rigid circuit board 2 is performed by soldering a lead pin 12 of the optical module 1 and a land (described later) provided at one end of the FPC 3 to the other end of the rigid circuit board 2 and the FPC 3. Is performed by soldering.

FIG. 2 is a diagram illustrating the optical module 1 of FIG. 1, and FIGS. 2A and 2B are a side view and a bottom view of the optical module, respectively.
As shown in FIG. 2A, the optical module 1 includes a semiconductor component such as an LD and a PD for transmitting and receiving optical signals in a package 11 in which an optical receptacle 11a into which an optical connector is inserted is formed at one end. It is what was stored. Further, from the side surface (bottom surface) 11b opposite to the optical receptacle 11a side of the package 11, as shown in FIG. 2B, as a lead pin 12, a receiving lead pin (first lead pin group) 12a and a transmitting lead pin (second lead) Both lead pins) 12b are drawn out.

Returning to the description of FIG. The rigid circuit board 2 is connected to an external circuit, and is equipped with a transmission circuit and a reception circuit including an LD driver IC that drives an LD in the optical module 1, and is electrically connected to the optical module 1 by the FPC 3. Connected to.
The FPC 3 according to the present invention includes a first FPC 31 that electrically connects a reception lead pin 12a (see FIG. 2) of the optical module 1 and the rigid circuit board 2, a transmission lead pin 12b of the optical module 1, and a rigid circuit board. And a second FPC 32 that electrically connects the two.

  A reception lead pin 12a is electrically connected to the first FPC 31, and the transmission lead pin 12b penetrates without being electrically connected. In order to enable this, one end 31a of the first FPC 31 on the optical module 1 side has a hole diameter that is substantially equal to (or slightly larger than) the diameter of the lead pins 12a and 12b, as shown in FIG. A through hole 31b is provided. A land 31c for connection to the lead pin 12a is formed around the through hole 31b at a position corresponding to the reception lead pin 12a of the optical module 1 in the through hole 31b.

Further, the transmission lead pin 12b that is not electrically connected to the first FPC 31 is electrically connected to the second FPC 32 to penetrate therethrough. Further, in this embodiment, merely through without receiving Ridobin 12 a are electrically connected. In order to enable these, one end portion 32a of the second FPC 32 on the optical module 1 side has a hole diameter substantially equal to (or slightly larger than) the diameter of the lead pins 12a and 12b, as shown in FIG. Through-holes 32b are provided. A land 32c for connection to the lead pin 12b is formed around the through hole 32b at a position corresponding to the transmission lead pin 12b of the optical module 1 in the through hole 32b.

  The receiving lead pin 12a of the optical module 1 is connected to the land 31c of the first FPC 31 while being passed through both the through hole 31b of the first FPC 31 and the through hole 32b of the second FPC 32. On the other hand, the transmission lead pin 12b of the optical module 1 is connected to the land 32c of the second FPC 32 while being passed through both the through hole 31b of the first FPC 31 and the through hole 32b of the second FPC 32. . Such a connection is made, and further, pads (not shown) formed on the other end portions 31d and 32d (see FIG. 1) of the first and second FPCs 31 and 32 and the pads on the rigid substrate 2 are electrically connected. Thus, both the element related to the transmission function and the element related to the reception function in the optical module 1 can be electrically connected to the rigid circuit board 2.

  As described above, the land to be connected to the transmission lead pin and the land to be connected to the reception lead pin are provided on different FPCs, so that the interval for providing the land is wide even if the interval for providing the lead pin is the same. Can do. Therefore, even if the diameter of the stem constituting the bottom of the optical module package is 5.6 mm (in this case, the diameter of the effective mounting area of the stem is about 3 mm), the size of the land is reduced. The diameter can be 1.0 mm (through hole diameter 0.60 mm, lead pin diameter 0.45 mm) or more.

  When the optical module and the rigid circuit board are electrically connected using the conventional technique, that is, using one FPC, it is sufficient to make the land interval wider than the lead pin interval. A land having a size can be formed. In this case, however, it is necessary to bend the lead pin (lead forming) in order to pass through the through hole of the FPC. This is not preferable because it may cause deterioration of characteristics. Further, in the lead forming, a force is easily applied to the root of the lead pin during the operation of changing the shape of the lead pin, and a load is applied to the glass sealing portion of the lead pins arranged at a narrow interval, which may cause abnormal product performance.

  In the above embodiment, the reception lead pin 12 a is electrically connected only to the first FPC 31, and the transmission lead pin 12 b is electrically connected only to the second FPC 32. However, the present invention is not limited to this form. For example, the reception lead pin 12a, the ground lead pin, the power supply lead pin, etc. belonging to the transmission lead pin 12b can be electrically connected to both FPCs in common. This is to stabilize the ground potential and the power supply potential.

Next, another example of the optical data link of the present invention will be described with reference to FIG. However, the description will be omitted by giving the same reference numerals to the parts described so far.
The number of FPCs used in the optical data link of the present invention is not limited to the two in the above example, but may be three or more, or may be one as shown in FIG.

  In the FPC 31 ′ used for the optical data link in the figure, the reception lead pin 12a (see FIG. 2) penetrates after being electrically connected, and the transmission lead pin 12b simply penetrates without being electrically connected. is doing. In order to enable this, the FPC 31 'has a hole diameter substantially equal to (or slightly larger than) the diameter of the lead pins 12a and 12b (see FIG. 2) at one end 31a, like the first FPC 31 of FIG. A through hole is provided. A solder connection land for connecting to the lead pin 12a is formed around the through hole at a position corresponding to the reception lead pin 12a of the optical module 1 in the through hole.

  In the optical data link of this example, the receiving lead pin 12a of the optical module 1 is passed through the through hole of the FPC 31 'and connected to the land. By making such a connection and further connecting the land formed on the other end 31d of the FPC 31 'and the pad on the rigid board 2, the element related to the receiving function in the optical module 1 and the rigid circuit board are connected. 2 can be electrically connected. On the other hand, the transmission lead pin 12 b of the optical module 1 is passed through the through hole of the FPC 31 ′ and directly connected to the pad on the rigid substrate 2. Thereby, the element related to the transmission function in the optical module 1 and the rigid circuit board 2 can be electrically connected.

As described above, only the land to be connected to the reception lead pin is provided in one FPC, and the transmission lead pin is directly connected to the rigid circuit board, so that the interval for providing the land is the same as the interval for providing the lead pin. But it can be widened. As a result, the land can be formed large, and the connection reliability is good. Instead of the above example, the reception lead pin may be directly connected to the rigid circuit board, and the transmission lead pin and the rigid circuit board may be connected using the same FPC as described above.
In the case of the example of FIG. 4, in order to electrically insulate the lead pin and the signal line on the FPC, the signal line of the FPC 31 ′ is provided on the surface 31f opposite to the land side for solder connection, A ground pattern (GND pattern) 31g may be provided on the surface.

Next, examples of other optical data links will be described with reference to FIGS. However, the description will be omitted by giving the same reference numerals to the portions described so far.
In the optical data link described with reference to FIG. 1, a ground pattern 32e may be formed on the surface of the second FPC 32 facing the first FPC 31, as shown in FIG. Thereby, crosstalk between transmission / reception can be reduced. The ground pattern for reducing crosstalk may be formed on the surface of the first FPC 31 facing the second FPC 32, or may be formed on the surfaces facing both the first and second FPCs 31 and 32. Good.

  Further, as shown in FIG. 1, the first FPC 31 and the second FPC 32 are overlapped at a portion where they are electrically connected to the lead pin 12, and the other portions extend in different directions (for example, directions opposite to each other). It is preferable to be attached to the optical module 1. Thereby, since the physical distance of the wiring formed on the surface of each of the first FPC 31 and the second FPC 32 can be increased, the crosstalk can be reduced. In this case as well, it is preferable to form a ground pattern for reducing crosstalk on the surface of one or both of the first and second FPCs facing the other.

  When the optical data link of this example is assembled, the second FPC 32 and the transmission lead pin 12b are connected after the first FPC 31 and the reception lead pin 12a are connected. In order to improve the workability of the connection of the second FPC 32, as shown in FIG. 5, after connecting the first FPC 31 and the reception lead pin 12a, an insulating spacer S thicker than the fillet F is passed through the transmission lead pin 12b. It is good to attach in the form to make.

  Thereby, the following can be suppressed. That is, when the second FPC 32 is connected, the fillet F around the reception lead pin 12a previously connected to the first FPC 31 is obstructed, and the flatness of the second FPC 32 is not obtained and the solder connection portion is not obtained. When the soldering iron is pressed, distortion of the second FPC 32 can be suppressed. Further, contact between the first FPC 31 and the second FPC 32 is avoided, for example, contact between the fillet F and the ground pattern 32e is avoided, and a short of the land 31c is eliminated.

Further, instead of using the spacer S, as shown in FIG. 6, a part of the transmission lead pin 12b 'is crushed and the second FPC 32 is locked so that the fillet F and the ground pattern 32e do not contact each other. The stopper 12c may be formed on the lead pin 12b.
The stopper 12c is formed in advance (before being attached to the package (stem) of the optical module 1) by partially changing the shape of the lead pin by an easy and mass-productive method such as press molding. It is preferable.
However, in this case, as shown in FIG. 7, the first FPC 31 ″ passes through the through hole 31b ′ through which the transmission lead pin 12b ′ passes, so that the portion where the locking portion 12c is formed also passes through the through hole 31b ′. Is preferably formed in an elliptical shape, for example.

DESCRIPTION OF SYMBOLS 1 ... Optical module, 2 ... Rigid circuit board, 3 ... FPC, 11 ... Package, 12 ... Lead pin, 12a ... Reception lead pin, 12b ... Transmission lead pin, 12c ... Locking part, 31 ... 1st FPC, 32 ... Second FPC, 31b ... through hole, 31c ... connection land, 32 ... FPC, 32b ... through hole, 32c ... connection land, 32e ... ground pattern.

Claims (5)

A first lead pin group that includes a light emitting element that transmits signal light and a light receiving element that receives other signal light and is electrically connected to the light emitting element, and a second lead pin group that is electrically connected to the light receiving element. A bidirectional optical module having
A rigid circuit board on which a transmission circuit and a reception circuit are mounted;
A first flexible board that connects the first lead pin group and the transmission circuit; a second flexible board that connects the second lead pin group and the reception circuit;
In an optical data link comprising
Each of the first lead pin group and the second lead pin group penetrates both the first flexible substrate and the second flexible substrate ,
The first lead pin group penetrates without being electrically connected to the second flexible substrate and is electrically connected to the first flexible substrate,
The optical data link characterized in that the second lead pin group penetrates and is electrically connected to the second flexible substrate without being electrically connected to the first flexible substrate . An insulating spacer through which at least one lead pin belonging to the first lead pin group or the second lead pin group passes is disposed between the first flexible circuit board and the second flexible circuit board. the optical data link of claim 1, wherein the. The first flexible circuit board is located between the first flexible circuit board and the second flexible circuit board on a lead pin of either the first lead pin group or the second lead pin group. 2. The optical data link according to claim 1 , further comprising a stopper that prevents the second flexible circuit board from coming into contact with the second flexible circuit board. Wherein at least one of the first flexible circuit board and the second flexible circuit board, the light according to any one of claims 1 to 4, characterized in that it is grounded pattern formed on a surface facing each other Data link. The first flexible circuit board and the second flexible circuit board are overlapped at portions that are electrically connected to the first lead pin group and the second lead pin group, respectively, and other portions are in different directions. The optical data link according to any one of claims 1 to 4 , wherein the optical data link extends in an optical path.

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