Photoelectric composite module and optical input/output device

A photoelectric composite module has an optical device, a package and a flexible printed circuit that is set along both case parts of the package, and electric wiring for the optical device is formed thereon. The package has a first case part and a second case part that is connected with the first case part by a hinge and is set on a mounted board. The optical device is joined with a surface that faces the first case part in said flexible printed circuit. The flexible printed circuit has light extraction means for transmitting an optical signal that should be exchanged between the optical device and the optical waveguide. The package has short-circuiting means for making a short circuit between the electrical wiring of the flexible printed circuit and the electrical wiring of the mounted board.

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-120597 filed on Apr. 25, 2006, the content of which is incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectric composite module mounted on a board, between boards or between backplanes of an information appliance such as a router, a server and a storage device.

2. Description of the Related Art

In recent years, the amount of information handled by an information appliance such as a router, a server and a storage device has been increasing dramatically. Accordingly, a limit on the electric transmission capacity in an interconnection, between boards or in a backplane of an information appliance has become obvious. An interconnection technique that uses an optical transmission is a common method in the industry to solve these problems.

A logic LSI configured as a low cost and compact input/output device using an optical interconnection is known in the industry as a means to perform signal processing and to use a photoelectric composite module for an input/output interface. The photoelectric composite module has an optical device, a driver IC and a circuit board for mounting the optical device and the driver IC by flip chip bonding as basic components. In addition to a layer-to-layer wiring formed on the circuit board, a wiring pattern is also formed on both sides of the circuit board.

A conventional technique using such a photoelectric composite module includes those described in the documents below, for example.

Japanese Patent Laid-Open No. 2003-185891 proposes an optical receiving device in which a photoelectric component such as photo electric device11and semiconductor device10or the like that adjusts the current amplitude of the optical device is implemented on circuit board14by a flip-chip bonding as shown inFIG. 2in the document. The device is fixed by metal bump18. Optical connectors15and16are attached to and detached from a fixed device.

Japanese Patent Laid-Open No. 2004-31508 proposes photoelectric composite module6in which optical device61and driver IC62are connected by a flip-chip bonding to electrode66on transparent plate13on which a wiring pattern is formed. Driver IC62is electrically connected to a board mounted with a module via layer-to-layer wiring69of transparent plate63and a via member. In order to adjust the height of an optical axis according to the height of the rack in which a board is housed, module4having optical axis converting device44with a mirror as shown inFIG. 4in the document is also provided.

Japanese Patent Laid-Open No. 2003-207694 proposes an optical module in which V groove6for positioning optical fiber array7is formed on connector5that is attached to package1and mirror9tilted by 45 degrees is arranged at the end of optical fiber array7. The light outputted from light emitting device2of package1is reflected on tilted mirror9via lens array4and its optical path is bent by 90 degrees and then input into optical fiber array7as shown inFIG. 2in the document.

Because optical connectors15and16are attached or detached to and from a device fixed to the board or the like according to the technique described in Japanese Patent Laid-Open No. 2003-185891, a channel for attaching and detaching them needs to be previously reserved on the board. Therefore, other electric components cannot be arranged on the channel for attaching and detaching optical connectors15and16. From the standpoint of the implement layout, it is not desirable that such a dead space be present on a board.

Because via member69intervenes in an electric connection between driver IC for input and output62and the mounted board according to the technique described in Japanese Patent Laid-Open No. 2004-31508, a high frequency property may be degraded. Since the direction to which heat is released from the optical device and the driver IC is limited toward the board on which they are mounted, the layout on the board is not simple.

The techniques described inFIG. 4of Japanese Patent Laid-Open No. 2004-31508 and Japanese Patent Laid-Open No. 2003-207694 require optical path converting means by a mirror or an optical coupling means by a lens between an optical connector to be attached or detached and a light receiving/emitting element. This leads to a problem in which the number of members and the number of processes are increased, and this raises the cost of implementation.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a photoelectric composite module that can reduce dead space in relation to attaching and detaching an optical connector to and from a board on which a photoelectric composite module is mounted.

The photoelectric composite module according to an aspect of the present invention includes an optical device for exchanging an optical signal with an optical waveguide, a package with a first case part and a second case part that is connected to the first case by a hinge and is set on a mounted board, and a flexible printed circuit that is set along both case parts of the package, and electric wiring for the optical device is formed thereon. The optical device is joined with a surface facing the first case part in the flexible printed circuit. The flexible printed circuit has light extraction means for transmitting an optical signal that should be exchanged between the optical device and the optical waveguide. The package has short-circuiting means for making a short circuit between the electrical wiring of the flexible printed circuit and the electrical wiring of the mounted board.

Attaching and detaching the optical waveguide to and from a photoelectric composite module having the above configuration can be performed when a hinge of the package is opened, i.e., the first case part is tilted to be horizontal to the second case part. Therefore, the optical waveguide can be vertically attached or detached to or from the mounted board. Therefore, since a channel for attaching and detaching optical connectors is not included in the area around the photoelectric composite module, a space for the channel needs not to be previously reserved on the mounted board. That reduces the dead space on the board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-120597 filed on Apr. 25, 2006, the content of which is incorporated by reference.

FIG. 1is a schematic oblique diagram showing a configuration of the first embodiment of the photoelectric composite module according to the present invention.FIG. 2is a schematic cross sectional diagram of the module.FIG. 3shows a procedure of mounting an optical connector that forms an optical waveguide to the module.FIG. 4is a schematic oblique diagram after the optical connector is mounted. With reference toFIG. 1toFIG. 4, photoelectric composite module10of the first embodiment will be described.

Photoelectric composite module101has package301that is mounted on module mounted board213. Package301has flat plate301bthat is attached to module mounted board213, flat plate301aconnected to flat plate301bby a hinge and flat plate301cconnected to flat plat301aand attached with fixing jigs303to be described later. Flat plate301afaces a first case part in the present invention, flat plate301bfaces a second case part, and flat plate301cfaces a third case part. The hinges of package301shown inFIG. 1are closed.

Fixing jigs303are attached to flat plat301cof package301. Hook parts of fixing jigs303in the figure are sandwiched between module mounted board213and plate301b. The shape of fixing jigs303is not limited to such a hook shape as shown in the figure and any shape may be used provided that its only function is to maintain the state shown inFIG. 1. For example, it may be fixed by pin or a latch may be formed on the package.

Flexible base plate201has light ejecting part206for transmitting light exchanged between photonic device202and optical transmission line211, alignment marker207for guiding the loading position of optical connector212, electrode208and electrode210which are electric wiring for electrically connecting photonic device202and input/output IC203to module mounted board213.

As shown inFIG. 2, photonic device202is implemented by flip chip bonding with metal bump209at a position where photonic device202is aligned with light ejecting part206. Input/output IC203is also implemented by flip chip bonding near photonic device202.

Light ejecting part206is a part of flexible printed circuit201surrounded by electrode208and electrode210, i.e., a part of the flexible printed circuit. Because part of flexible printed circuit201serves as light ejecting part206, optical coupling means such as a lens need not be provided between photonic device202and optical transmission line211. Since they are not needed, the number of members of a module and the number of processes are reduced. That reduces the implementing cost.

Flexible printed circuit201is desirably configured by using materials of silicon series, epoxy series or polyimide series that have high transparency across the wavelength range of photonic device202and such flexibility as to be able to be bent about 90 degrees. Electrode208and electrode210formed on flexible printed circuit201are formed by using a lithography technique after a film made of the electrode materials is formed on the flexible printed circuit.

Photonic device202is a conventionally known light emitting element or light receiving element that has a flat shape, with a plurality of elements being arranged on it in the array shape. If photonic device202is used as the light emitting element, input/output IC203serves as a driver IC. In such a case, driver IC203gives an electronic amplitude required for driving photonic device202to light emitting element202according to the modulation signal of a defined voltage supplied from the outside. If photonic device202is used as the light receiving element, input/output IC203serves as an electrical amplifying IC. Electrical amplifying IC203converts the light detected by photonic device202into a defined voltage and outputs it to the outside.

Electrode208connected to photonic device202and input/output IC203serves as an electrical connection mainly between photonic device202and input/output IC203and between input/output IC203and module mounted board213. Electrode208is formed for performing highly accurate alignment between photonic device202and input/output IC203when they are implemented by flip chip bonding with metal bump209. The other electrode210is formed to serve as part of an electromagnetic shield by acting as an earthed electrode. That provides shielding effect without using an expensive metal package.

Flexible printed circuit201is housed in package301along flat plate301cto flat plat301aas shown inFIG. 2and is also ejected outside package301through slit304of flat plate301b, i.e., to the side of module mounted board213. Electrode pad204for electrically connecting flexible printed circuit201and module mounted board213at the bottom of flat plate301bis provided therebetween.

When optical connector212is loaded to or removed from photoelectric composite module101, only the hinges of package301need to be opened as shown inFIG. 3. More specifically, flat plate301cand flat plate301ahorizontally open over flat plate301bas shown inFIG. 3by drawing fixing jigs303from the bottom of flat plate301bof package301closed as shown inFIG. 1and by opening each hinge. In that state, optical connector212is attached to or detached from flat plat302ain a vertical direction.

Therefore, because the direction for attaching and detaching optical connector212is vertical to module mounted board213, it is not necessary to provide a space in the direction for optical transmission line211extending near photoelectric composite module101.

After optical connector212is loaded in the state shown inFIG. 3, each hinge closes as shown inFIG. 4. Since the hook part of fixing jigs303is tucked at the bottom of package301, flat plate301acontacting with photonic device202is fixed at an almost vertical position to flat plate301b, and optical connector212is fixed in a state that optical connector212is wrapped by package301. Package301is fixed in a state that stress (shrinking stress and stretching stress) applied to flexile printed circuit201is a minimum.

Therefore, the direction of inputting and outputting light can be maintained horizontal against module mounted board213without using any optical axis converting means such as a mirror. Because it is adapted to cover optical connector212, the entire module can be downsized.

As an example of operations of photoelectric composite module101, a case where photonic device202is a light emitting element will be described. An electric logical signal of a defined voltage is supplied to driver IC203from module mounted board213through electrode pad204and electrode208. At the same time, a ground voltage is supplied to driver IC203via electrode204of the flexile printed circuit. Then, a current that has an amplitude required for driving light emitting element202and that corresponds to an external electric signal flows from driver IC203to light emitting element202. Then, an optical signal is emitted from light emitting element202according to the current, and the optical signal is coupled with light transmission line211of optical connector212via light ejecting part206.

A fiber array, a fiber sheet that is formed by a fiber array wrapped in laminate materials, or the like can be used, as light transmission line211that is optically coupled with photoelectric composite module101. The quality of material can be a polyimide series or a Si series.

As mentioned above, according to the embodiment, optical connector212can be vertically attached to or detached from module mounted board213. Since a detaching/attaching channel is not included in the area around photoelectric composite module101, space for the channel for attaching and detaching the optical connectors need not be previously reserved on module mounted board213. That can reduce the dead space on the board.

Because optical connector212loaded on photoelectric composite module101is horizontally fixed to the board, it is useful for connecting optical transmission line211and electric components on the board. Since flexible printed circuit201is adapted to be ejected from slit304onto the board as shown inFIG. 2, there will be a good connection between electrodes208and210of photonic device202and IC for input and output203with an electrode of the board. That can prevent degradation of the high frequency property.

A photoelectric composite module with a simple design for heat release of an element can also be realized. This is because it is adapted such that photonic device202and an IC for input and output203is vertically fixed to module mounted board213to cause the board to horizontally release heat.

FIG. 5shows a configuration of the second embodiment of the photoelectric composite module. Photoelectric composite module102of the embodiment has package504with flat plate504a, flat pate504band flat plate504cconnected with flat plate504aby a hinge. Fixing jigs505are attached to flat plate504c.

Flexible printed circuit506of the embodiment is housed in package504along each flat plate504a,504band504cas shown inFIG. 5. As such, via501, as a short-circuiting means between flexible printed circuit506and mounted board502, is formed on flat plate504bset on mounted board502. Via501is a conductive member fed through flat plate504band via501is arranged to be aligned with pad pattern503of the electrode of mounted board502.

A procedure of attaching or detaching the optical connector to or from photoelectric composite module102and the electrical effects are the same as those of the first embodiment, thus, they will be omitted from the description.

To enable better contact with flat plat504bof package504and mounted board502, fixing jigs505may be pins that are fixed to the side of flat plate504b. If some object in the shape of a hook such as the abovementioned fixed jig303is applied to photoelectric composite module102, it is desirable to form a groove on the bottom of flat plate504bthat is in contact with mounted board502so that the hook shaped parts can be housed in the groove. That is to say, package504may be adapted so that no convexity is created on the bottom of flat plate504bthat is connected to mounted board502.

In order to match via501of package504and pad pattern503on mounted board502, a mechanism for converting a pit of pad pattern503may be added.

As mentioned above, the embodiment shown inFIG. 5also eliminates the requirement of previously reserving space for the channel for attaching/detaching the optical connector on module mounted board502. That can reduce the dead space on the board.

Now, an embodiment of the input/output device that uses the abovementioned photoelectric composite module101(102) will be described.FIG. 6shows a configuration of the first embodiment of the light input/output device. Light input/output device111of the embodiment has photoelectric composite module101′ which is the same as photoelectric composite module101shown inFIG. 1and logic LSI601which is mounted on flexible printed circuit602extending from module101′. As photoelectric composite module101′, photoelectric composite module102as shown inFIG. 5may be used instead of that shown inFIG. 1.

Logic LSI601is a LSI for controlling an input/output signal of photoelectric composite module101′. For making an electrical connection between logic LSI601and photoelectric composite module101′, flexible printed circuit602can be used. Although photoelectric composite module101′ is described in the configuration shown inFIG. 6, there may be a plurality of module101′.

FIG. 7shows the second embodiment of the light input/output device. Light input/output device112has a plurality of photoelectric composite modules901and sub board903, on which optical waveguide902is formed. Photoelectric module901is the same as abovementioned photoelectric composite module101or photoelectric composite module102from which fixing jigs305and505have been eliminated.

Sub board903is clipped on photoelectric composite module901. Sub board903can be attached or removed by opening the hinge of each photoelectric composite module901.

Light input/output device112of the embodiment serves to rewire or arrange a channel of the optical signal in the array because each of photoelectric composite modules901that corresponds to communication channel are different from each other, and sub board basal board903exchange the optical signal.

According to the embodiment shown inFIG. 7, even if an object that is to be optically connected with an optical device is relatively big, such as sub board903, and needs to be attached to a plurality of photo electric composite modules901, the object can be easily attached to or detached from the optical device by opening and closing the hinge.

Although the package of each embodiment has three flat plates, a package may be formed with two flat plates corresponding to the first case part and the second case part according to the present invention. That is to say, in the configuration shown inFIG. 1, for example, flat plate301cwith fixing jigs303attached is omitted. In that case, for example, with jigs are provided as fixing means and positioned from both sides of flat plate301ato both sides of flat plate301b, stability of the package can be improved because the hinges are closed.

While exemplary embodiments of the present invention have been described using specific terms, such a description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.