Electrooptical unit.

p0001The invention relates to an electro-optical assembly according to the preamble of claim 1.

p0002The development of electro-optics, in particular the development of signal transmission via optical waveguides leads to modules in which optical components and electrical components such as film circuits are combined. In the manufacture of such assemblies there is the problem that the optical components must be protected before the least pollution because of the low light amplitudes. Conventional methods for the attachment of film circuits are in a housing by means of the soldering flux or adhesive bonding with a solvent containing, as a rule glue, so that these methods are not applicable in connection with optical components.

p0003From EP-A2-0118677, for example, a method of setting a light receiving end of a light guide at the focal point of a lens and a device suitable therefor is described. Here, the light guide element by means of adhesive is fixed to a lens support member. Unless there are exposed optically effective surfaces, there is a risk of contamination by components of an epoxy resin adhesive or solvent for the adhesive.

p0004In addition, there is the problem that in the manufacture of the electro-optical assembly - must be made a very accurate assembly of the optical and opto-electrical components - because of the small dimensions of the optical waveguide and thus of the transmitted light beam. In particular, in the assembly of multilayer circuits, which comprise optoelectronic devices, besides, the problem arises that neither the conventional assembly methods of the optics and the methods of attachment of the film circuit technology can be used.

p0005The object of the invention is thus to allow high-precision position-correct installation of an opto-electrical component containing layer circuit in one, optical devices containing metal housing with waiver of gluing and soldering.

p0006According to the invention the object is achieved by an electro-optical assembly formed in accordance with the characterizing part of patent claim 1. Expedient developments of the electro-optical assembly according to the invention are in the claims 2-5 and a production method is described in patent claim sixth The inventive electro-optical assembly is in an advantageous manner without a subsequent purification of, can continue in the film circuit they are produced by one of the conventional manufacturing process prior to the onset of the opto-electrical device in an advantageous manner so that the structure described is suitable for a variety of film circuits , by the metallic intermediate carrier also results in a good thermal contact between layer circuit and caseback.

p0007The invention will be explained in more detail below with reference to an embodiment shown in the drawing.

p0008In which:<ul><li>Fig. 1 shows a section through an inventive electro-optical assembly and</li><li>Fig. 2 shows the top view of the assembly of Fig. 1 with removed screening.</li></ul>

p0009In FIG. 1, the metallic housing bottom GB denotes that is part of a metal housing in which a receiver module for optical signal transmission over optical fibers as well as a mirror and an optical filter are installed. The integrated circuit IC with the opto-electrical component OB is attached as part of the circuit layer SS on the ceramic substrate KS, which is secured over a large area to an intermediate carrier made of comparatively thin sheet metal, which in turn is mounted on the housing base GB. The mounting of the substrate is carried out by Löten-, bonding and alloying on the intermediate carrier ZT are also possible. The intermediate carrier ZT has a larger area than the ceramic substrate KS, so that protrude on two opposite sides of the edge strip over the ceramic substrate KS, which serve for fastening on the housing bottom.

p0010The integrated circuit IS contains the opto electrical component and an electrical amplifier arrangement. For this reason, the entire circuit layer is protected from electrical interference by a metallic shield AK, via the opto-electrical device of the circuit layer SS an optical window FO is in the screening AK used in the form of a translucent glass sheet. The intermediate carrier ZT is made of Vacon 10, this material has a thermal expansion coefficient which is between that of the ceramic substrate and the KS of the housing base GB. The connection of the intermediate carrier ZT and the screening AK with the housing bottom is done through welding spots, which were generated by means of laser welding. The heat flow from the circuit layer on the ceramic substrate and the intermediate support to the housing bottom has proved to be good.

p0011In the plan view shown in Fig. 2 on the electro-optical assembly according to the invention can be seen that three capacitor chip CHP, CVC, CM are arranged on the substrate as part of the layer circuit, which are connected via contact strips and bond wires to the integrated circuit IS in electrical communication , The intermediate carrier protrudes out from under the circuit layer and is formed on two opposite sides of edge strips ZTR, which are connected at the edge by means of weld points SP with the housing bottom.

p0012In the following, the manufacturing method of the electro-optical assembly according to Figures 1 and 2 will be explained. In a first method step, the contact pads for the capacitors CHP, CVC, and CM, and a metallized support surface for the integrated circuit IC are produced on the ceramic substrate KS. Thereafter, the assembly of the circuit layer with the individual components, the fastening of these components, for example by thermal bonding as well as the attachment of the circuit layer on the intermediate carrier takes place ZT. Thereafter, the film circuit is in the correct position aligned with the intermediate support on the caseback with a maximum error of about ± 25 microns and is welded by laser welding the edge strips of the intermediate support to the housing base. The intermediate carrier is thereby pressed to the ceramic substrate KS on the housing bottom in order to ensure the heat flow from the ceramic substrate to the housing base. Instead of laser welding can also be a resistance welding process to produce the welds SP or a weld may be used. Finally, the screening cap AK is adjusted with the optical window FO over the layer circuit SS so that the optical window is above the opto electrical component if the integrated circuit IC and the shield AK also connected by means of laser welding or resistance welding with the housing bottom. In view of the welding method used, the intermediate carrier is plated over the entire area and partially gold-plated, and the screening cap is nickel-plated.