JPH06102426A - Flexible optical waveguide circuit - Google Patents

Abstract

PURPOSE:To provide a packaging method capable of connecting optically to optional multipoints and with high precision and with high density, in an optical integrated circuit connecting among plural electronic elements optically. CONSTITUTION:Plural electronic elements 6 are loaded on an electronic circuit sustrate 9, and further, a light emitting or a light receiving elements is bonded adjacent to them. The light emitting element is a laser diode 3 in junction up, and is joined to a substrate wiring pattern 8 through a sub mount 4. Further, the light receiving element 5 is Joined to the substrate wiring pattern 8 by flip chip bonding. A flexible optical waveguide circuit substrate 1 and an optical waveguide 2 are joined to the laser diode 3 or the light receiving element 5 on a surface opposing to the electronic circuit substrate 9. Thus, the optical connection to optional multipoints is enabled without attenuating and interfering a signal. Further, regardless of the positional deviation of bonding of the optical/ electronical elements to the substrate, the highly precise optical connection is attained.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical interconnection between chips, for example, an optical parallel connection basic interface between microprocessor chips in a massively parallel computer, or an optical / electronic switching part of an optical subscriber system and an optical network. The present invention relates to a flexible optical waveguide circuit used for an interface and other general printed wiring boards.

2. Description of the Related Art Connecting a plurality of electronic elements by electric wiring causes mutual interference and attenuation of signals in high-speed / high-density mounting. Therefore, an optical connection integrated technology for connecting electronic elements with an optical element is considered. Has been done. Previously, for example, Uchida et al. 1992 IEICE Spring Conference C-27
0, PP4-312; glass substrate for optical surface mounting; and by forming an optical waveguide on the same substrate on which an electronic element is mounted and performing surface micromachining, an optical signal is transmitted vertically and horizontally. There is a proposal to use the substrate like an optical printed circuit board by reflecting / refracting the light. In addition, by forming the optical waveguide on a wafer different from the wafer on which the electronic circuit is formed, as proposed in Japanese Patent Laid-Open No. 4-119667 by Hayashi, high speed and mutual connection can be achieved between any two points of the electronic circuit. Methods have also been proposed for making interference-free signal connections.

In the conventional surface mounting method by Uchida et al., It is necessary to form two kinds of electronic circuits / optical waveguides on the same substrate, and it is difficult to form the substrate, which is disadvantageous for high-density mounting. Also, in the optical connection method of integrated circuits by Mr. Hayashi,
Since the electronic circuit board and the optical waveguide board are separate bodies, it is difficult to assemble a plurality of optical junctions. In view of the above problems, an object of the present invention is to connect a plurality of electronic elements to each other in order to suppress mutual interference and attenuation due to electric wiring in a circuit in which electronic elements are integrated. It is to provide a connection mounting method. Also provided is a method for easily and densely mounting a plurality of optical connection points having a function of branching / demultiplexing / multiplexing even in a composite circuit such as an optical waveguide / optical element / electronic element.

In order to achieve the above-mentioned object, the present invention connects the electronic element to a light emitting or light receiving element in a circuit in which a plurality of electronic elements are integrated, and further connects between the light emitting / light receiving element. A single-layer or multilayer flexible optical waveguide circuit is used for optical connection to enable high-density mounting. Further, the present invention is a composite circuit of an optical fiber / optical waveguide / optical element / electronic element, etc., in which each or each of them is optically connected by a single-layer or multilayer flexible optical waveguide circuit to enable high-density mounting. Is.
In the above optical integrated circuit, the end face of the flexible optical waveguide circuit is processed into a slanted or spherical shape to form a coating film, or by forming a Mahachender interference type waveguide in the flexible optical waveguide circuit, a single layer or Branching between multilayer flexible optical waveguide circuits
It has a demultiplexing / multiplexing function. The flexible optical waveguide circuit is composed of a core and a clad waveguide having different refractive indexes, is deformable by heat or pressure, and at least the substrate near the end face of the waveguide connected to the light emitting / receiving element is made of a transparent or semitransparent material. By being formed by (3), the optical connecting portion can be directly assembled and can be assembled. Further, by applying metallization to the front surface or the back surface of the above flexible optical waveguide circuit, and by functioning as a ground surface in joining to an electronic circuit board, the aerial direction electric force lines of high frequency signals generated from the electronic circuit board are absorbed, This is to suppress mutual interference of electric signals.

If the optical waveguide is formed separately from the substrate on which the electronic element and the optical element are mounted, the electronic element can be mounted at a higher density. If this optical waveguide is a flexible film type, optical wiring can be performed not only at two adjacent points but also at a plurality of optical connection points, and multilayer wiring can be easily realized by utilizing the characteristics of the thin film. That is, since light does not receive mutual interference, not only electronic elements can be mounted at high density, but also their signals can be transmitted at high speed through a network. It is obvious that this method can be similarly applied to a composite circuit such as an optical fiber / optical waveguide / optical element / electronic element. This flexible waveguide circuit can be easily formed and has high productivity by using, for example, a transparent plastic material, and thin film formation and multilayer wiring are possible. Furthermore, by making the end face of the optical waveguide oblique / spherical, it is possible to branch to an optical waveguide between multiple layers or adjacent to each other by utilizing the light reflected or refracted from the end face. Further low pass /
By coating a high-pass filter, functions such as demultiplexing / combining can be provided. In addition, if the front or back surface of this flexible waveguide circuit is metallized and mounted close to and facing the electronic circuit board, electric lines of high-frequency signals generated from the electronic circuit board are absorbed, and electrical signals to the adjacent wiring pattern are absorbed. Mutual interference of signals can be suppressed because leakage is suppressed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is shown in FIGS. FIG. 1 is a sectional view showing an optical connection between a flexible optical waveguide circuit and an electronic circuit. A plurality of electronic elements 6 are mounted on an electronic circuit board 9, and light emitting or light receiving elements are further bonded adjacent to each other as shown in the figure. At least one light emitting or light receiving element corresponds to one electronic element, and the electronic element 6 is bonded to the light emitting or light receiving element via the substrate wiring pattern 8 by the flip chip bonding method with Au / Sn solder. In the present invention, the light emitting element uses the junction-up laser diode 3 and is bonded to the substrate wiring pattern 8 via the submount 4. The light receiving element 5 is a back illuminated PIN photodiode, and is joined to the board wiring pattern 8 by Au / Sn solder by a flip chip bonding method. The flexible optical waveguide substrate 1 and the optical waveguide 2 are joined to the light emitting or light receiving element on the surface facing the electronic circuit substrate 9.
On the flexible optical waveguide substrate 1, Ti / Pt / Au is removed except for a positioning window for connecting with a laser and a light receiving element.
Is metalized and connected to ground. The metallized portion 10 is joined to the N-side electrode of the P-type substrate laser diode, and at the same time absorbs the lines of electric force of the high frequency signal generated from the substrate wiring pattern 8 and suppresses the interference of the electric signal. FIG. 2 is a diagram showing an optical connection cross section of the flexible optical waveguide circuit and the junction up laser diode. The laser diode 3 is formed of a P-type InP substrate, and the N-side electrode Ti / Pt / Au is Pb / Sn.
By the metallized portion 10 of the flexible optical waveguide substrate 1
Is joined to. The total thickness of the N-side electrode, the Pb / Sn solder, and the metallization on the waveguide substrate is 4.5 ± 0.5 μm. The laser diode active layer 11 is located 5.5 ± 0.3 μm below the lower surface of the N electrode. On the other hand, the optical waveguide 2 is formed of a gradient index plastic core having a radius of 10 ± 1 μm, and is fixed so that the center of the core is located 10 μm from the waveguide substrate 1. The tip of the optical waveguide core is lens-processed to R = 30 μm.
Therefore, when the flexible optical waveguide circuit board 1 is bonded to the laser diode 3, the positional deviation ΔY between the laser diode active layer 11 and the optical waveguide core center (Y in the direction perpendicular to the film type optical waveguide board) is ± 1.
It can be set within 8 μm. If the optical axis direction is Z and the direction perpendicular to the Y and Z axes is the X axis (the light emitting portion at the end face of the laser diode active layer is the origin), then the X axis and the Z axis.
The positional deviations ΔX and ΔZ in the axial direction can be aligned directly from the top surface of the substrate by using the alignment window of the transparent film waveguide substrate 1. The alignment accuracy could be ± 1 μm. For a laser having a full width at half maximum of FFP of about 35 × 35 degrees, ΔZ = 40 μm gives the best optical coupling efficiency of about 7
Obtained 5%. The fluctuation of the coupling efficiency within the positional deviation is 1
It was within dB. The optical waveguide has a refractive index distribution (G
It is of type I) and obtains a band of 30 GHz in the transmission of a bandwidth of 300 MHz · Km, 10 m. FIG. 3 shows an optical connection method between the film type optical waveguide and the flip-chip bonded back illuminated light receiving element. Optical waveguide 2
Has an oblique groove formed right above the light receiving element PN junction, and the guided light 20 can be branched into reflected light 21 and refracted light 22 on this oblique surface. This end surface oblique processing part 13
Can have a condensing property of reflected light or refracted light by making it spherical. The coupling efficiency to the light receiving element in the oblique waveguide with R = 300 μm was about 20%. Next, as a second embodiment, an example in which the present film type optical waveguide is applied to an optical coupling system is shown in FIGS. FIG. 4 shows an example in which the flexible optical waveguides are multi-layered and the connection points are made high in density. However, even when the waveguides are wired in the directions orthogonal to each other, there is no need to directly cross, and therefore no loss occurs. Flexible optical waveguide circuit is 2
Since it is a thin film with a thickness of about 00 μm, it is possible to form multiple layers of three layers or more, and it is possible to implement mounting in other directions and multiple connections. Further, since this optical waveguide circuit is flexible, it is possible to absorb a deviation (± 20 μm) in height / position etc. of the electronic element / optical element after bonding, thereby enabling highly accurate optical connection. FIG. 5 shows an example in which a signal is transmitted between the multilayer wirings of the flexible optical waveguide circuit. By aligning the optical waveguides of two layers next to each other and obliquely processing the end faces of the optical waveguide by about 45 degrees,
The light of the guided light 20 is reflected in a direction perpendicular to the waveguide direction. At this time, by applying the first and second end face coating films 17 and 18 to the oblique end faces, the reflectance is increased from 10% to 8%.
I was able to improve to 0%. As a result, it was possible to perform signal transmission between two adjacent waveguides with a loss of about 2 dB. FIG. 6 shows an example of demultiplexing by a flexible optical waveguide circuit. The end face obliquely processed portion 13 is coated with end face coating films 17 and 18 having the characteristics shown in FIG. The guided light 20 is a combined light of 1.3 μm / 1.5 μm.
The 1.5 μm light is reflected by the end face coating film 17 of
Further, the light is reflected by the second end face coating film 18
Of the optical waveguide 33. On the other hand, the 1.3 μm light that has passed through the first end-face coating film is guided to the first guided light 32 as refracted light 22 as it is. This 1.3 μm /
The isolation amount of 1.5 μm was as good as 60 dB.

EFFECTS OF THE INVENTION It is possible to connect signals of many electronic elements such as a processor and a memory to an arbitrary point without attenuation or interference. Also, by making the film type optical waveguide transparent, it is possible to perform highly accurate alignment in direct view, and use the flexibility of the film to achieve highly accurate optical connection regardless of misalignment of the optical / electronic element to the substrate. Can be done.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of optical connection between a flexible optical waveguide circuit and an electronic circuit.

FIG. 2 is a view showing a cross section of optical connection between a flexible optical waveguide circuit and a laser diode.

FIG. 3 is a view showing an optical connection cross section of a flexible optical waveguide circuit and a light receiving element.

FIG. 4 is a diagram showing a multilayer cross wiring of a flexible optical waveguide circuit.

FIG. 5 is a diagram showing a method of connecting layers of a flexible optical waveguide circuit.

FIG. 6 is a diagram showing demultiplexing / multiplexing wiring of a flexible optical waveguide circuit.

FIG. 7 is a diagram showing a reflection characteristic of an end face coating film.

[Explanation of symbols]

1 ... Flexible optical waveguide circuit board, 2 ... Optical waveguide,
3 ... Laser diode (J-up), 4 ... Submount, 5 ... Light receiving element (back surface incident type), 6 ... Electronic element, 7 ... Solder joint part, 8 ... Board wiring pattern, 9
... electronic circuit board, 10 ... metallized portion, 11 ... laser diode active layer, 12 ... laser solder joint portion, 13
... end surface oblique processing part, 14 ... light receiving element N electrode, 15 ...
Light receiving element P electrode, 16 ... Light receiving element P-N junction part, 1
7 ... 1st end surface coating film, 18 ... 2nd end surface coating film, 20 ... Guided light, 21 ... Reflected light, 22
Refraction light, 31, 32 ... First optical waveguide, 33 ... Second optical waveguide.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Miyazaki 1-280 Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Keiko Matsuoka 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Center

Claims (11)

[Claims] 1. A flexible optical waveguide circuit comprising a flexible thin film substrate and one or more flexible optical waveguides. 2. The flexible optical waveguide circuit according to claim 1 has a property of being deformed by heat or pressure while maintaining the property of the waveguide, and the length of the waveguide can be easily deformed to an arbitrary length. A flexible optical waveguide circuit characterized by: 3. The substrate of the flexible optical waveguide circuit according to claim 1 or 2, wherein at least a portion near the end face of the waveguide or an optical element connecting portion is transparent, and the waveguide and the optical element or another optical waveguide are connected. A flexible optical waveguide circuit characterized in that optical axes can be aligned when viewed directly from the substrate side in optical connection. 4. A light emitting element or a light receiving element is connected to one or both sides of a waveguide end face of the flexible optical waveguide circuit according to claim 1, 2 or 3, and the optical element is further an electronic circuit pattern or an input / output of the electronic element. A flexible optical waveguide circuit characterized by being connected to terminals and the like. 5. The flexible optical waveguide circuit according to claim 4, wherein the optical element is connected to the optical waveguide substrate side in advance, and thereafter the electronic circuit pattern or the input / output terminal of the electronic element can be connected. A flexible optical waveguide circuit having a solder layer. 6. The flexible optical waveguide circuit according to claim 1, 2, 3, 4 or 5, wherein the light-emitting 1 × light-receiving N is connected in parallel or cascade, and the light-emitting N × light-receiving M is connected in parallel or cascade. Alternatively, a multi-channel flexible optical waveguide circuit in which optical elements are connected to each other. 7. The flexible optical waveguide circuit according to claim 1, 2, 3, 4, 5 or 6, wherein a low-pass, high-pass filter or the like has an end face of the waveguide or an oblique or spherical processed portion in the waveguide. It is characterized by having a multiplexing / demultiplexing function by means of, or by having a demultiplexing function by the Maha-Zehnder interferometry method, etc., in which light-emitting elements of different wavelengths are connected in parallel or in cascade, and wavelength multiplexing is enabled. Flexible optical waveguide circuit. 8. A flexible optical waveguide circuit for an electronic circuit board or the like, wherein one side or both sides of the flexible optical waveguide circuit board according to claim 1, 2, 3, 4, 5, 6 or 7 is metalized. A flexible optical waveguide circuit, which functions as a ground plane in the connection of, and absorbs the lines of electric force generated from an electronic circuit to suppress the interference and attenuation of electric signals. 9. The light emitting / receiving element joined to the waveguide of the flexible optical waveguide circuit according to claim 4, 5, 6 or 7 is as small as or smaller than the electrode bonding area of the electronic element. A flexible optical waveguide circuit, which can be directly connected to an electrode of an electronic device or a pattern of an electronic circuit board. 10. The flexible optical waveguide circuit according to claim 7, 8 or 9, wherein transmission and multiplexing between layers are caused by reflection by a slanted or spherically processed portion and a filter coating which are laminated in multiple layers and formed in the waveguide. A flexible optical waveguide circuit capable of demultiplexing and performing three-dimensional transmission and wavelength division multiplexing transmission. 11. Claims 1, 2, 3, 4, 5, 6, 7,
The flexible optical waveguide circuit board described in 8, 9, or 10 has a ground surface on one side and a high-frequency signal circuit surface such as a coplanar wave guide on the other side. A flexible optical waveguide circuit which is optically connected and bonded on a circuit board, and which suppresses interference, attenuation, and delay of a high-frequency signal to or from an optical element.