JP2005084126A - Electro-optical composite substrate, optical waveguide, and optical waveguide with optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily presume a cause of failure when optical transmission becomes impossible in an electro-optical composite substrate where an optical element is mounted in an optical waveguide and electronic circuit substrates are spliced. <P>SOLUTION: In the electro-optical composite substrate where a light emitting elements 14 and a light receiving element 15 are mounted on one side of the optical waveguide 10; electronic circuit substrates 30a, 30b are laminated on the opposite side; and the light emitting element 14 and the electronic circuit substrate 30a, and the light receiving element 15 and the electronic substrate 30b are electrically connected to each other through via-wiring 22a, 22b, respectively, the optical waveguide 10 is provided with conductive layers 20a, 20b and are electrically connected to the via-wiring 22a, 22b. As a result of this, when an abnormality occurs in the optical transmission in the optical waveguide 10, it becomes possible to easily presume faulty points (separation or the like of electrically connected parts of an optical waveguide or failure of optical elements) by monitoring the signals inputted/outputted to/from each element 14, 15 via the conductive layers 20a, 20b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optoelectric composite substrate in which an electronic circuit board and an optical waveguide for optical signal transmission are integrated, an optical waveguide suitable for producing the optoelectric composite substrate, and an optical waveguide with an optical element.

  In optical communication systems including images that are becoming increasingly popular in the future, a dramatic increase in transmission capacity and a dramatic improvement in processing speed of information processing apparatuses are required. In such an environment, signal transmission over a relatively short distance, such as connections between wiring boards in electronic devices that are responsible for high-capacity high-speed communication, connections between semiconductor chips in a wiring board, or connections within a semiconductor chip With regard to the above, in place of the conventional signal transmission using a metal cable or metal wiring, optical transmission using an optical waveguide is being adopted.

As an important technique for supporting such optical transmission, there is a technique for connecting an optical waveguide to an optical element such as a vertical surface light emitting diode (VCSEL) or a photodiode (PD).
As a method of connecting an optical waveguide to an optical element, conventionally, a case in which a condensing lens is fitted on an electronic circuit board on which the optical element is mounted is covered, and a housing with a reflecting mirror is integrated with the case with a guide pin. A method for fixing the waveguide to the front surface of the reflection mirror has been proposed. (For example, refer nonpatent literature 1 etc.).

  However, in this method, since the case and the housing are fitted with the guide pins, the distance between the reflection mirror and the optical element is increased, and a condensing lens is required. In addition, since the lens is focused, the optical axis alignment between the optical element-lens-reflecting surface-optical waveguide is adjusted from the optical element so that the received light energy becomes maximum when the light receiving element is operated. It is necessary to use an active alignment method that adjusts the position of a component that matches the optical waveguide. Further, when this active alignment operation is performed, static electricity may be generated between the components, and there is a problem that the optical element is easily deteriorated due to the static electricity.

  On the other hand, as a method for solving such a problem, a method of improving the connection accuracy between the optical element and the optical waveguide by directly mounting the optical element on the optical waveguide has been proposed (see, for example, Non-Patent Document 2).

  That is, in the proposed method, the end face of the optical waveguide is cut at an angle of 45 degrees with respect to the axial direction of the core to form a reflecting surface, and the laser light from the optical element is reflected by 90 degrees by the reflecting surface, The optical element is directly mounted on the optical waveguide so as to be incident on the core portion of the optical waveguide. Further, in this method, in order to supply power or an electrical signal to the optical element, the optical circuit board on which the optical element is mounted is mounted on the electronic circuit board, and the electronic circuit board is connected via the via wiring penetrating the optical waveguide. The electronic circuit board and the optical waveguide are integrated so as to supply power or an electric signal from the wiring pattern portion to the optical element mounted on the optical waveguide.

According to this method, a case or a housing for joining the optical waveguide and the optical element becomes unnecessary, the distance between the reflecting surface and the optical element becomes small, and a condensing lens becomes unnecessary. Also. Alignment is also possible with the passive alignment method, and the problem of deteriorating the optical element due to static electricity generated between the components during the active alignment operation is solved.
Electronics Packaging Society Journal Vol. 5 No. 5 AUG. 2002 Present state and future of optical circuit packaging technology (Ichiro Hiyama et al.) H15, sponsored by the Advanced Technology Development Organization, 4th Electronic SI Research Report Meeting, Report Meeting Material 106 (Keiichi Kumai)

  By the way, in the above mounting method, in order to electrically connect the optical waveguide and the optical element or the optical waveguide and the electronic circuit board, a conductive thin film is formed on the end portion of the via wiring that penetrates the optical waveguide. It is necessary to connect the optical waveguide and the optical element or the optical waveguide and the electronic circuit board by solder reflow or flip chip bonding on the thin film.

  However, forming a thin film on an optical waveguide and bonding the optical waveguide and the optical element or the optical waveguide and the electronic circuit board by solder reflow or flop chip bonding or the like means that the optical waveguide and the optical element or the optical waveguide and the electronic circuit are joined. In some cases, adhesion to the substrate may not be obtained, and there is a problem that the joint surface is easily peeled off, and there is a risk of disconnection at the joint surface between the optical waveguide and the optical element or between the optical waveguide and the electronic circuit substrate.

  That is, the optical waveguide and the optical element, or the joint surface between the optical waveguide and the electronic circuit board is peeled off or cracked by vibration, impact, mechanical bending force, heat, or the like during optical transmission through the optical waveguide. There is a risk that the optical element may not be able to receive and emit light and light transmission cannot be performed due to disconnection at the joint surface due to the above.

In addition, optical transmission becomes impossible at the time of disconnection, but it cannot be estimated whether the cause is due to disconnection or a defect of the optical element.
Therefore, in order to use the conventional method not only in industrial use but also in apparatuses widely used in offices and homes, there are significant problems from the viewpoint of maintainability, and a solution has been desired.

  That is, when optical transmission becomes impossible, it is estimated in a short time whether the cause is a defect in the optical element or due to the disconnection of the joint surface between the optical waveguide and the optical element or between the optical waveguide and the electronic circuit board. Thus, it has been desired to reduce the time and cost required for repair.

  The present invention has been made in view of these problems. The above-described optical element is mounted on an optical waveguide, the optical waveguide is connected to an electronic circuit board, and electrons are connected via a connection wiring provided in the optical waveguide. An object of the present invention is to make it possible to easily estimate the cause of a failure when optical transmission through an optical waveguide is disabled in an opto-electric board that transmits and receives electrical signals from a circuit board.

The invention according to claim 1, which has been made to achieve the object,
An optical element for transmitting and receiving optical signals;
An optical waveguide mounted with the optical element and having an optical path for transmitting an optical signal to be emitted from or incident on the optical element;
An electronic circuit board in which an electronic circuit for transmitting or receiving an electrical signal via the optical element is incorporated, and the optical waveguide is laminated via a surface opposite to the mounting surface of the optical element;
A plurality of connection wirings provided to electrically connect the electronic circuit board and the optical element;
A photoelectric composite substrate comprising:
In order to monitor an electrical signal input to and output from the optical element via each connection wiring, a plurality of conductive layers connected to each connection wiring are formed on the mounting surface of the optical element of the optical waveguide. It is characterized by.

  In the optoelectric composite substrate of the present invention configured as described above, an electrical signal input / output between the electronic circuit board and the optical element via the connection wiring is formed on the mounting surface of the optical element in the optical waveguide. It is possible to monitor through the conductive layer, and whether the optical element is the cause of failure when an optical transmission in the optical waveguide is abnormal is the optical waveguide side (specifically, disconnection of connection wiring, connection wiring And inadequate connection between the electronic circuit board and the optical element, etc.).

  In other words, for example, when a light emitting element is mounted as an optical element in an optical waveguide, and an abnormality occurs in light transmission from the light emitting element, an electric signal input from the electronic circuit board to the light emitting element is conducted. By monitoring through the layer and determining whether the electrical signal matches the output from the electronic circuit board, whether the cause of optical transmission failure is in the optical element (light emitting element) or on the optical waveguide side It can be detected very easily. In this case, when the electrical signal monitored through the conductive layer matches the output from the electronic circuit board, it can be determined that the light emitting element has failed, and the electrical signal matches the output from the electronic circuit board. When it is not (usually not changing), it can be determined that the light-emitting element is normal and a disconnection or the like has occurred on the optical waveguide side.

  Also, for example, when a light receiving element is mounted as an optical element in the optical waveguide, and a normal light receiving signal is not input from the light receiving element to the electronic circuit board, output from the light receiving element to the electronic circuit board side via the connection wiring The optical signal (light receiving signal) is monitored through the conductive layer, and it is determined whether the electric signal is changing normally, so that the optical element (light receiving element) is the cause of the signal reception failure. Whether it is on the optical waveguide side can be detected very easily. In this case, when the electrical signal monitored through the conductive layer does not change (in other words, when no signal is output from the light receiving element), it can be determined that the light receiving element has failed, and the electrical signal changes normally. If it is, disconnection or the like occurs on the optical waveguide side, and it can be determined that the light reception signal is not transmitted from the optical element to the electronic circuit board.

  As described above, according to the optoelectric composite substrate of the present invention, the cause of failure when abnormality occurs in the optical transmission in the optical waveguide can be identified very easily. It is possible to reduce maintenance and repair costs.

  Here, the conductive layer is used to directly monitor an electric signal input / output to / from the optical element mounted on the optical waveguide via the connection wiring. However, it may be separately formed on a surface different from the mounting surface (that is, the surface laminated on the electronic circuit board).

  That is, if the conductive layers connected to the connection wiring are formed on both surfaces of the optical waveguide in this way, whether the optical element is the cause of the failure when an optical transmission in the optical waveguide is abnormal is determined on the optical waveguide side. If the cause of the defect is on the optical waveguide side, there is an abnormality in the connection part between the optical element and the connection wiring, or there is an abnormality in the connection part between the connection wiring and the electronic circuit board. It is possible to determine whether or not there is a failure, and it is possible to detect the failure location in more detail.

Further, the conductive layer does not need to be exposed on the surface of the optical waveguide, and an insulating film may be formed to protect the conductive layer except for the monitor terminal portion.
Further, as shown in claim 2, the connection wiring penetrates from the laminated surface of the optical circuit board of the optical waveguide (in other words, the surface opposite to the mounting surface of the optical element) to the mounting surface of the optical element. Via wiring formed as described above may be used.

  On the other hand, the optical waveguide may be simply laminated on one electronic circuit board. For example, the optical waveguide has a pair of light emitting / receiving units (a plurality of pairs when there are a plurality of optical paths) at both ends thereof. An optical element can be mounted, and a pair of electronic circuit boards corresponding to each optical element may be laminated on a surface opposite to the mounting surface of the optical element.

That is, two electronic circuit boards may be connected via an optical waveguide on which an optical element for optical communication is mounted, and signals may be transmitted and received between the electronic circuit boards via the optical waveguide.
In the case where one optical waveguide is arranged so as to connect a plurality of electronic circuit boards, a force such as vibration, impact or mechanical bending is easily applied to the optical waveguide from each electronic circuit board. . In this case, if the optical waveguide is made of an inorganic material such as glass, the optical waveguide becomes relatively hard, so that the force applied to the optical waveguide, such as vibration, impact, or mechanical bending, is optical. A stress is directly applied to the joint portion between the element and the optical waveguide or the joint portion between the electronic circuit board and the optical waveguide, resulting in a problem that the joint portion is easily peeled off.

Therefore, in order to prevent such a problem, as described in claim 3, it is preferable to configure the optoelectric composite substrate with the optical waveguide having flexibility.
That is, by making the optical waveguide flexible, for example, a polymer material system, a force such as vibration, impact, or mechanical bending applied to the optical waveguide may cause a joint between the optical element and the optical waveguide or an electron. It is possible to relieve the direct application of stress as a stress to the joint between the circuit board and the optical waveguide, and to prevent the joint from peeling off.

  Next, the invention according to claim 4 relates to an optical waveguide suitable for manufacturing the optoelectric composite substrate according to claim 1, claim 2, or claim 3, for transmitting and receiving optical signals. In addition, a plurality of connection wirings for inputting / outputting electric signals to / from the mounted optical element are formed from the mounting surface of the optical element to the back surface, and further on the mounting surface of the optical element. Is characterized in that a plurality of conductive layers connected to each connection wiring are formed in order to monitor an electrical signal input to and output from the optical element through each connection wiring.

  Similarly, the invention according to claim 5 relates to an optical waveguide with an optical element suitable for producing the optoelectric composite substrate according to claim 1, claim 2, or claim 3. An optical element for transmitting and receiving signals is mounted, and a plurality of connection wirings for inputting and outputting electrical signals to the mounted optical element are formed from the mounting surface to the back surface of the optical element, and the mounting of the optical element The surface is characterized in that a plurality of conductive layers connected to each connection wiring are formed in order to monitor an electrical signal input to and output from the optical element via each connection wiring.

  Therefore, if the optical waveguide according to claim 4 or the optical waveguide with an optical element according to claim 5 is used, the photoelectric composite substrate of the present invention (claims 1, 2, 3) can be easily realized. Thus, the effects of the present invention described above can be exhibited.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view of an optoelectric composite substrate according to an embodiment to which the present invention is applied, cut along the optical axis of an optical waveguide.

  As shown in FIG. 1, the optoelectric composite substrate 1 of the present embodiment includes a light emitting element 14 such as a VCSEL, a light receiving element 15 such as a PD, an optical waveguide 10 mounting these optical elements, and an IC 31a. The electronic circuit board 30a and the electronic circuit board 30b on which the IC 31b is mounted.

Here, the optical waveguide 10 is long and is formed by covering a core 11 having a high refractive index serving as an optical path with a clad having a low refractive index.
A light emitting element 14 is mounted on one end of the optical waveguide 10 in the longitudinal direction, and a light receiving element 15 is mounted on the opposite end. The electronic circuit board 30a is connected to the surface opposite to the mounting surface of the light emitting element 14, and similarly, the electronic circuit board 30b is connected to the opposite surface of the light receiving element 15 mounting surface.

  The optical waveguide 10 includes a plurality of via wirings 22a penetrating from the mounting surface of the light emitting element 14 to the mounting surface of the electronic circuit board 30a (the via wiring in front of the cut surface is shown in FIG. 1 is provided, and the light emitting element 14 and the electronic circuit board 30a are electrically connected by the via wiring 22a.

  Similarly, the light receiving element 15 is also electrically connected to the electronic circuit board 30b by a plurality of via wirings 22b penetrating the optical waveguide 10 from the mounting surface of the light receiving element 15 to the mounting surface of the electronic circuit board 30b.

  In the optical waveguide 10, an optical path conversion unit 16 a is formed on the optical axis of the mounted light emitting element 14. As described in Non-Patent Document 2, the optical path changing unit 16a is formed by cutting the optical waveguide 10 by blade machining or the like at an angle of 45 degrees with respect to the optical axis direction of the core, and is perpendicular to the optical axis of the core. The laser beam incident from the direction is reflected and incident on the core, and the laser beam propagating through the core is reflected in the direction perpendicular to the optical axis of the core.

  Then, as described in Non-Patent Document 2, the light-emitting element 14 is aligned so that the optical axes of the light-emitting element 14 and the optical path changing unit 16a coincide with each other. Bonded by bonding or the like.

An IC 31a is mounted on the electronic circuit board 30a, and further, a power supply and other electronic circuits (not shown) necessary for operating the IC 31a are mounted.
Similarly, the light receiving element 15 is also adjusted in alignment so that the optical axis of the light receiving element 15 coincides with the optical path changing unit 16 b formed in the optical waveguide 10, and is joined to the optical waveguide 10.

An IC 31b is mounted on the electronic circuit board 30b, and further, a power source and other electronic circuits (not shown) necessary for operating the IC 31b are mounted.
On the electronic circuit board 30a side, a transmission signal from the IC 31a is input to the light emitting element 14 through the via wiring 22a through the wiring pattern of the electronic circuit board 30a. The light emitting element 14 performs electro-optical conversion on the input transmission signal and emits laser light. The emitted laser light is reflected by the optical path conversion unit 16a, enters the core 11 of the optical waveguide 10, and is transmitted to the electronic circuit board 30b side.

  On the electronic circuit board 30 b side, the transmitted laser light is reflected by the optical path conversion unit 16 b and is incident on the light receiving element 15. The light receiving element 15 photoelectrically converts the incident laser light and outputs a reception signal. The reception signal is input to the IC 31b through the wiring pattern of the electronic circuit board 30b through the via wiring 22b.

In this way, signals are input / output between the IC 31a and the IC 31b.
Here, the optical waveguide 10 is formed with a conductive layer 20a for estimating the cause of failure when light transmission between the light emitting element 14 and the light receiving element 15 becomes impossible. The configuration and function of the conductive layer 20a will be described in detail with reference to FIGS.

FIG. 2 is an enlarged view of one optical element mounting portion of FIG. 1, and FIG. 3 is a cross-sectional view showing a state when FIG. 2 is cut along aa ′.
As shown in FIG. 2, a plurality (two in this embodiment) of conductive layers 20a are formed on the surface of the optical waveguide 10 on which the light emitting element 14 is mounted. The conductive layer 20a is formed, for example, by laminating a conductive metal or a conductive polymer on the optical waveguide 10 by a process suitable for each material. Further, the end portion 21 a of the conductive layer 20 a is formed so as to be electrically connected to the via wiring 22 a and to be joined to the terminal of the light emitting element 14. The end 21 a is arranged on the optical waveguide 10 in the same manner as the terminal arrangement of the light emitting element 14.

  Similarly, at the opposite end of the optical waveguide 10, a plurality of conductive layers 20b are formed on the surface on which the light receiving element 15 is mounted. The end portion 21 b of the conductive layer 20 b is formed so as to be electrically connected to the via wiring 22 b and to be joined to the terminal of the light receiving element 15. The end 21 b is arranged on the optical waveguide 10 in the same manner as the terminal arrangement of the light receiving element 15.

  In the thus formed photoelectric composite substrate, the light emitting element 14, the via wiring 22a, the conductive layer 20a, and the electronic circuit board 30a are electrically connected, and therefore, from the electronic circuit board 30a via the via wiring 22a. The transmission signal sent to the light emitting element 14 is also sent to the conductive layer 20a at the same time.

  Therefore, when an abnormality occurs in transmission / reception by light transmission performed between the light emitting element 14 and the light receiving element 15 as described above, if the cause is a defect in the light emitting element 14, a transmission signal is transmitted to the conductive layer 20a. Therefore, by connecting a measuring instrument such as an oscilloscope to the conductive layer 20a and observing the transmission signal, if the waveform or the like is normal (the same waveform as the transmission signal), the light emitting element 14 Defects can be estimated. In addition, when the cause is peeling of the joint portion between the light emitting element 14 and the optical waveguide 10, the transmission signal is not sent to the conductive layer 20 a, so the observation waveform is abnormal (the signal is not observed at all). If there is, it can be estimated that peeling or the like of the joint portion between the light emitting element 14 and the optical waveguide 10 has occurred.

  Similarly, the conductive layer 20b of the optical waveguide 10 is formed on the light receiving element 15 side, and the light receiving element 15, the conductive layer 20b, the via wiring 22b, and the electronic circuit board 30b are electrically connected.

  Therefore, as described above, the laser light that passes through the core 11 and is reflected by the optical path conversion unit 16b and incident on the light receiving element 15 is photoelectrically converted into a reception signal, and the electronic circuit board 30b via the via wiring 22b. Are simultaneously output to the conductive layer 20b.

  When an abnormality occurs in transmission / reception by light transmission performed between the light emitting element 14 and the light receiving element 15, a measuring instrument such as an oscilloscope is connected to the conductive layer 20b, and the received signal is observed to emit light. Contrary to the case of the element 14, if the light receiving element 15 is defective, no reception signal is sent to the conductive layer 20 b, so if the observation waveform or the like is abnormal (such as no signal is observed), the light reception is performed. The defect of the element 15 can be estimated. Further, when a disconnection or the like due to peeling of the joint between the light receiving element 15 and the optical waveguide 10 occurs, the received signal is sent to the conductive layer 20b, so that the observation waveform is normal (the same waveform as the received signal). ), It can be presumed that peeling of the joint between the light receiving element 15 and the optical waveguide 10 has occurred.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, A various aspect can be taken. For example, in the above embodiment, the conductive layer 20a is described as being formed on the mounting surface of the light emitting element 14. For example, the conductive layer 20a is formed on the surface opposite to the mounting surface other than the conductive layer formed on the mounting surface of the light emitting element 14. It may be formed.

FIG. 4 is a diagram showing a form of the optical waveguide 10 in which a conductive layer is also formed on the surface opposite to the light emitting element 14.
As shown in FIG. 4, the same via wiring 22a as described above is formed in the optical waveguide 10 of this embodiment. Furthermore, a conductive layer 20 c and a conductive layer 20 d are formed in the optical waveguide 10. The conductive layer 20c and the conductive layer 20d are formed, for example, by laminating a conductive metal or a conductive polymer on the optical waveguide 10 by a process suitable for each material.

  The conductive layer 20c is formed on one surface 40a of the optical waveguide 10, and the conductive layer 20b is formed on the opposite surface 40b of the optical waveguide 10, and each is electrically connected to the via wiring 22a.

  As described above, the conductive layer 20c and the conductive layer 20d are formed on both surfaces of the optical waveguide 10 and are electrically connected to the via wiring 22a. The number of locations where the transmission signal supplied from 30a is measured increases, and the failure location when optical transmission is impossible can be estimated more accurately.

It is explanatory drawing showing the whole structure of the photoelectric composite board | substrate of an Example. It is the elements on larger scale of FIG. 1 showing the structure of the optical element mounting part of the photoelectric composite board | substrate of an Example. It is explanatory drawing showing the structure of the optical waveguide of the photoelectric composite board | substrate of an Example. It is explanatory drawing which shows the structure of the optical waveguide of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photoelectric composite board | substrate, 10 ... Optical waveguide, 11 ... Core, 12 ... Cladding, 14 ... Light emitting element, 15 ... Light receiving element, 16a, 16b ... Optical path conversion Part, 20a, 20b, 20c, 20d ... conductive layer, 21a, 21b ... end, 22a, 22b ... via wiring, 23 ... bump, 30a, 30b ... electronic circuit board, 31a , 31b... IC.

Claims (5)

An optical element for transmitting and receiving optical signals;
An optical waveguide mounted with the optical element and having an optical path for transmitting an optical signal to be emitted from or incident on the optical element;
An electronic circuit board in which an electronic circuit for transmitting or receiving an electrical signal via the optical element is incorporated, and the optical waveguide is laminated via a surface opposite to the mounting surface of the optical element;
A plurality of connection wirings provided to electrically connect the electronic circuit board and the optical element;
A photoelectric composite substrate comprising:
In order to monitor an electrical signal input to and output from the optical element via each connection wiring, a plurality of conductive layers connected to each connection wiring are formed on the mounting surface of the optical element of the optical waveguide. A photoelectric composite substrate characterized by comprising:   2. The photoelectric composite substrate according to claim 1, wherein the connection wiring is a via wiring formed so as to penetrate from a laminated surface of the optical waveguide to the electronic circuit substrate to a mounting surface of the optical element. .   The photoelectric composite substrate according to claim 1, wherein the optical waveguide has flexibility. An optical waveguide capable of mounting an optical element for transmitting and receiving an optical signal, and having an optical path for transmitting an optical signal to be emitted from the mounted optical element or incident on the optical element,
From the mounting surface to the back surface of the optical element, forming a plurality of connection wiring for inputting and outputting electrical signals to the optical element,
A plurality of conductive layers connected to each connection wiring are formed on the mounting surface of the optical element in order to monitor an electrical signal input / output to / from the optical element via each connection wiring. Characteristic optical waveguide. An optical element with an optical element on which an optical element for transmitting and receiving an optical signal is mounted and having an optical path for transmitting an optical signal to be emitted from the optical element or incident on the optical element,
From the mounting surface to the back surface of the optical element, forming a plurality of connection wiring for inputting and outputting electrical signals to the optical element,
A plurality of conductive layers connected to each connection wiring are formed on the mounting surface of the optical element in order to monitor an electrical signal input / output to / from the optical element via each connection wiring. A featured optical waveguide with an optical element.

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