WO2003038491A1

WO2003038491A1 - Conductor arrangement

Info

Publication number: WO2003038491A1
Application number: PCT/SE2002/002009
Authority: WO
Inventors: Leif Bergstedt; Björn LÖFVING
Original assignee: Imego Ab
Priority date: 2001-11-02
Filing date: 2002-11-04
Publication date: 2003-05-08
Also published as: EP1440337B1; JP2005507506A; EP1440337A1

Abstract

The present invention relates to a conductor-carrier arrangement (10) for conducting one or several types of signals, one of said being an optical signal. The arrangement comprises: a substrate (13), and at least one optical conductor guide (11) for said optical signal arranged on said substrate. The optical guide is provided with a covering layer (12) consisting of a material having different characteristics than said optical guide material and on an optical guide is provided on said substrate (13) during a production stage of the said substrate (13).

Description

Title

CONDUCTOR ARRANGEMENT

TECHNICAL AREA

The present invention relates to a waveguide arrangement for guiding a signal, specially an optical signal, comprising at least one optical waveguide arranged on a substrate, preferably a ceramic substrate.

DESCRIPTION OF STATE OF THE ART

Optical communication is being utilized in more applications today than ever before. These optical systems provide benefits not previously available in electrical systems. Optical fibers have been established as the transmission device of choice for telecommunications, supporting very high bandwidth and low losses over long distances, providing a capability that far exceeds the copper-wire technology it replaces. Research is now looking at a possibility of applying optical wiring for shorter distances, for example in between electro- optic components on circuits, inter circuit communication, inside computers, medical applications and so on.

In optical telecommunication, optical signals are traditionally guided using fiber optical technology, optical waveguides, connectors, components and other types of circuitry or transmitted in free space propagation. However, the prior art does not disclose any technology wherein the optical waveguides for telecommunication are arranged onto a (especially) ceramic carrier.

In US 5,937,125, US 5,574,814 and US 5,452,390, applications including LTCC (Low Temperature Cofired Ceramic) -technology in the optical area are disclosed. The documents show different optical contacts wherein LTCC-technology has been used to a type of bedding or a base plate in the conducts. None of these documents show a conductor being applied directly on a LTCC-carrier.

Shuenemann et al. in Sensors and Actuators 73 (1999) p. 153-168, Elsevier Science S.A. shows a module using LTCC-technology. The module is adjusted for managing signals of a micro flow, electronics and optics. The aim of Korean patent document No. 9,711,521 is to reduce the manufacturing cost and the loss of a propagation horn. Thus, a method for manufacturing an optic propagation horn is disclosed, comprising a first through fourth steps. The first step is to manufacture a paste, which is used for manufacturing glass by using silica powder. The second step is to coat the paste on a substrate by a screen-printing method and to thermally process and to form a buffer layer. The third process is to coat the paste on the buffer layer and to form a core layer by thermal processing with lower temperature than the thermal processing temperature of the buffer layer. The fourth step is to coat the paste on the core layer and form a clad layer by thermally processing with lower temperature than that of the core layer.

This document does not concern using different glass types having different characteristics as same paste is used to make all guiding parts.

An optical waveguide is disclosed in US 5,261,022, which waveguide comprises a substrate of A1203 and a silica glass film of Si02 applied thereon. The glass film has between 35-90 mol % Si02. The device may be used in conjunction with electronics on the same substrate to form opto-electronic interconnections. The invention may also be used to apply a thin film glass glaze to a ceramic substrate. Also, in this document same guiding material having same characteristics are used.

BRIEF DESCRIPTION OF THE INVENTION

The main object of the invention is to arrange a guide for an optical signal, e.g. electromagnetic radiation in the wavelength band between ultra violet and sub millimeter band, on a (ceramic) carrier arrangement. The waveguide can specially be an optical waveguide arrangement but also a combined conducting arrangement, thus it is suitable for conducting both electrical and optical signals.

Yet, another very essential object of the invention is to provide guiding of an optical signal in the different directions, i.e. in the plane of the substrate in the waveguide arrangement.

For these reasons the invention comprises a conductor-carrier arrangement for conducting one or several types of signals, one of said signals being an optical signal. The arrangement comprises: a substrate and at least one optical conductor guide for said optical signal arranged on said substrate. The optical guide is provided with a covering layer consisting of a material having different characteristics than said optical guide material and on an optical guide is provided on said substrate during a production stage of the said substrate. In the preferred embodiment, the substrate can be a ceramic substrate. The optical guide can be made of one of a ceramic material such as a glass composite material, a glass, a polymer or the like, substantially transparent material in the wavelength band used in a particular application. A cross section of the optical guide is substantially rectangular or semi-circular or resemble of a circle segment. The optical guide is fixedly arranged on the substrate by means of a paste. The covering layer can be a cladding layer. The substrate is initially provided with an intermediate support, on which the optical guide is provided. A refractive index (n2) of the covering layer differs from a refractive index (nl) of the optical guide for enclosing the signal. Preferably, the substrate consists of one of a LTCC (Low Temperature Cofired Ceramic) or a HTCC (High Temperature Cofired Ceramic) material. Most preferably, the guide is provided on the substrate through offset printing.

The invention also relates to a method for manufacturing a conductor-carrier arrangement for conducting a signal, specially an optical signal. The conductor arrangement comprising at least one optical guide arranged on a ceramic substrate by providing the ceramic substrate with at least one paste, and fixing at least one optical guide by pressing on said ceramic substrate by means of said paste and providing said optical guide with a covering layer having different characteristics than said optical guide. The method further comprises the step of providing the optical guide with at least one covering layer before or after arranging said optical guide on said substrate. The method further comprises the step of initially providing the ceramic substrate with an intermediate support, and providing the intermediate support with a second optical guide. The method further comprising the step of providing the optical guide on said substrate through offset printing.

The invention also relates to a method for manufacturing a conductor-carrier arrangement for conducting a signal, especially an optical signal. The conductor-carrier arrangement comprises at least one optical guide arranged on a ceramic substrate by: providing the ceramic substrate with at least one glass-paste through printing, as a supporting member, performing a first co-firing of said printed glass-paste and the substrate, printing a second glass-paste on said support as the optical guide, and performing a second co-firing of said optical guide. The printing method is screen-printing. The first glass-paste has different characteristics the second glass-paste. The first co-firing is performed in a higher temperature than the second co-firing.

BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described with reference to the embodiments according to enclosed drawings, in which:

Fig. 1 is a side-view of a first embodiment of a guiding arrangement according to the invention, Fig. 2 is a side-view of a second embodiment of a guiding arrangement according to the invention, and Fig. 3 is a flow diagram illustrating some of the manufacturing steps.

DESCRIPTION OF PREFERRED EMBODIMENTS

A carrier arrangement 10 provided with a waveguide arrangement is schematically shown in Fig 1, and consists of at least one core section 11, provided on substrate 13. Preferably, the core section is manufactured of a ceramic material such as a glass composite material, a glass, a polymer or the like, substantially transparent material in the wavelength band used in a particular application. The cross section of the core can be arbitrary chosen but can be rectangular shaped, semi circular or resembles a segment of a circle. The width of the cross- section is preferably 1 - 1000 μm.

In the preferred embodiment, the core 11 is provided with at least one coating in form of a cladding layer 12 or the like. The cladding layer 12 is also consists of a ceramic material such as a glass material, a polymer or the like. Preferably, the cladding layer 12 is substantially transparent as well, but can also be a reflecting material such as a metal. Additionally, different glass types having different reflective indexes can be used.

However, the refractive index r>2 of the cladding 12 preferably differs from the refractive index nl of the core 11. Due to the difference in refractive index, in the case that both core and cladding are transparent, or due to reflection in the cladding, the inner surface in the case the cladding is reflecting, an optical signal is guided in the arrangement.

Furthermore, it is also possible to arrange the optical waveguide to constitute a core layer 11 only, i.e. without any cladding layer 12, see Fig. 2. For example, in another embodiment of the invention, the core 11 can be doped to introduce reflecting properties in the core near the surface, or the core can have a varying profile of index of refraction through its cross section.

The cladding layer 12, as seen in Fig. 1, can completely surround the core 11 and when the complete optical waveguide 11, 12 and 14 is subsequently arranged on a carrier such as a ceramic substrate 13 the part 14 of the cladding constitute a "foot" in form of an intermediate support, whereupon the optical core 11 can be provided. In this way, both the transmission characteristics and manufacturing technology are improved. The intermediate support 14 consists of a metal or a ceramic material such as a glass transparent for the actual optical wavelength as the cladding layer, as description above.

Preferably, the ceramic substrate 13 is manufactured of a LTCC (Low Temperature Cofired Ceramic) material. However, a HTCC (High Temperature Cofired Ceramic) material can be possible as well. The optical waveguide core 11 can be provided on the ceramic substrate 13 with or without the covering cladding layer 12 according to above. Moreover, the cladding layer 12 can also be provided on the core 11 in different stages of the manufacturing process. The core 11 can be provided on the ceramic substrate 13 by means of a paste applied on the ceramic substrate 13, whereby the optical conductor 11 is applied, e.g. by pressing it onto the substrate 13. In this way, the optical waveguide can obtain a flattened cross-section arranged on the ceramic substrate 13. Then the organic matter of the paste can be fired. Consequently, the waveguide 11 is fixedly arranged on the substrate 13.

The carrier arrangement 10 according to the invention can be employed in applications for guiding a signal such as an electro-magnetic radiation, e.g. light.

Further, the invention also embodies a method for manufacturing such a waveguides-and the use of such an arrangement for different applications, e.g. single mode lOμm/Multimode lOOμm. Different steps are illustrated in fig. 3 and described below.

When manufacturing for single mode applications, for example, a paste is applied onto the carrier through offset printing. The paste is then re-melted. Offset printing allows fine and accurate waveguides.

According to another manufacturing method, a standard LTCC, e.g. provided with electrical conductors etc., is pre-produced. Then a glass-paste is printed (preferably, screen-printed) on one face of the substrate, as a support. The printed glass-paste and the substrate are cofired (e.g. at 800 °C). When the support is dried (hardened) a second glass-paste, i.e. the optical waveguide, is printed (screen printed) on the support structure. Preferably, the optical waveguide paste has other characteristics than the first paste, such as melting and curing temperatures. The optical waveguide paste is then co-fired, preferably at a lower temperature than the first co-firing. The reason for the lower temperature is that: The first glass should float out more to obtain a very flat surface, and the second glass has a more controlled viscosity to maintain a certain shape of the waveguide.

The invention is not limited to the shown embodiments but can be varied in a number of ways, e.g. through combination of two or more embodiments shown, without departing from the scope of the appended claims and the arrangement and the method can be implemented in various ways depending on application, functional units, needs and requirements

Claims

1. A conductor-carrier arrangement (10) for conducting one or several types of signals, one of said signals being an optical signal, said arrangement comprising:

• a substrate (13)

• at least one optical conductor guide (11) for said optical signal arranged on said substrate, characterized in that said optical guide is provided with a covering layer (12) consisting of a material having different characteristics than said optical guide material and on an optical guide is provided on said substrate (13) during a production stage of the said substrate (13).

2. The arrangement as claimed in claim 1, wherein said substrate is a ceramic substrate.

3. The arrangement as claimed in claim 1, wherein said optical guide is made of one of a ceramic material such as a glass composite material, a glass, a polymer or the like, substantially transparent material in the wavelength band used in a particular application.

4. The arrangement as claimed in claim 1, wherein a cross section of the optical guide is substantially rectangular or semi-circular or resemble of a circle segment.

5. The arrangement as claimed in any of the preceding claims, wherein the optical guide (11) is fixedly arranged on the substrate (13) by means of a paste.

6. The arrangement as claimed in claim 71, wherein said covering layer is a cladding layer.

7. The arrangement as claimed in any of the preceding claims, wherein the substrate (13) is initially provided with an intermediate support (14), on which the optical guide (11) is provided.

8. An arrangement as claimed in claim 6, wherein a refractive index (n2) of the covering layer (12) differs from a refractive index (nl) of the optical guide (11) for enclosing the signal.

9. An arrangement as claimed in claim 3, wherein the substrate (13) consists of one of a LTCC (Low Temperature Cofired Ceramic) or a HTCC (High Temperature Cofired Ceramic) material.

10. An arrangement as claimed in any one of claims 1 to 9, wherein the guide is provided on the substrate through offset printing.

11. A method for manufacturing a conductor-carrier arrangement (10) for conducting a signal, specially an optical signal, said conductor arrangement (10) comprising at least one optical guide (11) arranged on a ceramic substrate (13) by providing the ceramic substrate (13) with at least one paste, and fixing at least one optical guide (121) by pressing on said ceramic substrate (13) by means of said paste and providing said optical guide with a covering layer (12) having different characteristics than said optical guide.

12. A method as claimed in claim 11, further comprising the step of providing the optical guide (11) with at least one covering layer (12) before or after arranging said optical guide (11) on said substrate (13).

13. A method as claimed in one of claims 11 or 12, further comprising the step of initially providing the ceramic substrate (13) with an intermediate support (14), and providing the intermediate support (14) with a second optical guide (11).

14. A method as claimed in any one of the claims 11 to 13, further comprising the step of providing the optical guide on said substrate through offset printing.

15. A method for manufacturing a conductor-carrier arrangement (10) for conducting a signal, especially an optical signal, said conductor-carrier arrangement (10) comprising at least one optical guide (11) arranged on a ceramic substrate (13) by: providing the ceramic substrate (13) with at least one glass-paste through printing, as a supporting (14) member, performing a first co-firing of said printed glass-paste and the substrate, printing a second glass-paste on said support (14) as the optical guide (11), and performing a second co-firing of said optical guide.

16. A method as claimed in claim 15, wherein said printing method is screen-printing.

17. A method as claimed in claim 15, wherein the first glass-paste has different characteristics the second glass-paste.

18. A method as claimed in claim 15, wherein the first co-firing is performed in a higher temperature than the second co-firing.