Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-07-23
2003-01-07
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C257S081000, C257S099000, C385S075000, C385S092000, C438S025000, C438S027000, C438S064000, C438S065000
Reexamination Certificate
active
06504107
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an assembly unit which consists of a printed circuit board with an electro-optical component and of an optical component. The invention further relates to a method of producing such an assembly unit.
In the field of integrated optics there are known assembly units in which electro-optical components such as laser diodes, LEDs and photodetectors are coupled with an optical component, for instance an optical fiber or a waveguide. For this purpose, the electro-optical components are arranged on a substrate on which the optical component is arranged, too. An example of such an assembly unit is known from the German Laid-open Document 44 10 740 in which a photodetector is coupled with an optical fiber. The photodetector and the optical fiber are received in a two-piece substrate, with a waveguide trench being provided in one substrate part, which trench is filled up by the optically transparent adhesive substance used upon bonding the two substrate parts with each other, so that a waveguide is formed which couples the photodetector and the waveguide with each other.
On producing such an assembly group there occur in particular two problems. Firstly, a precise positioning of the electro-optical component relative to the optical component can be done only with a large expenditure, for instance by using guiding slopes which are intended to provide for the optimum alignment. Examples of such configurations are known from the German Laid-open Documents 44 01 219 and 42 32 608. Secondly, there results a comparably high reject rate, because the optical member which is coupled with the electro-optical component, i.e. the waveguide in the cited example, is formed only with the final step of bonding the two substrate parts to each other. If the waveguide is defective, this will mean that also the photodetector has to be rejected, as it is inseparably linked with the assembly unit. The problem of the high reject rate is the larger, the more components have to be combined with each other. If, for example, a process consisting of 200 individual steps leads to a yield of 80%, this will mean that each individual step has to be performed with a yield of 99.9%. It is for this reason that the monolithic integration—in discussion as an alternative production method and theoretically promising a very good coupling of the components used—i.e. the production of electronics, opto-electronics and optics including waveguides in a single material system such as InP, for instance, will still not be utilizable for some time.
An additional problem consists in the need of achieving the required electrical terminals of the electro-optical component. When the electro-optical component is embedded in a substrate, conductors or the like have to be provided for a supply line.
From prior art it is further known to arrange electro-optical components, in particular electro-optical semiconductors, on printed circuit boards. For this, preferably the Lead Frame technology is used by means of which an electro-optical chip can be arranged on the printed circuit board with an accuracy of approximately 50 &mgr;m. This accuracy, however, is not sufficient for the adjustment relative to an optical waveguide which may have dimensions in the range of down to 1 &mgr;m.
SUMMARY OF THE INVENTION
The invention provides an assembly unit in which an optical component is arranged relative to an electro-optical component with the desired accuracy. The invention further provides a method for the production of such an assembly unit, which is distinguished by a high yield.
The assembly unit according to the invention consists of a printed circuit board and an optical component, the printed circuit board being provided with at least one electro-optical component, at least one conducting track for the connection of the electro-optical component, as well as a three-dimensional, microstructured adjustment formation, the electro-optical component being precisely arranged relative to the latter, and a three-dimensional positioning formation being provided on the optical component and cooperating with the adjustment formation of the printed circuit board in such a way that the optical component is precisely coupled with the electro-optical component of the printed circuit board. The assembly unit according to the invention thus consists of two subassembly units, namely first the printed circuit board with the electro-optical component and, secondly, the optical component itself. These are each operative for themselves, so that they can be checked separately from each other. So there is the possibility of checking, with regard to the printed circuit board, whether the conducting tracks for the connection of the electro-optical component, the connection of the electro-optical component with the conducting tracks and, finally, the electro-optical component itself are fully operative. With regard to the optical component, for instance a waveguide or an optical fiber, there is the possibility to check whether its function is in order. It is only upon assembly of the printed circuit board and the optical component that the electro-optical component is coupled with the optical component, namely in a passive way via the adjustment and positioning formations.
According to a preferred embodiment it is provided that the printed circuit board is an injection-molded part which is partially provided with a metallization. In this way there results an efficient manufacturing of the printed circuit board, as all formations which are required for precisely positioning the electro-optical component, for instance a microstructured depression, as well as the adjustment formation, for instance a raised adjustment cross, are able to be formed in a simple way from a suitably configured mold. The increased expenditure for the precise manufacturing has to be spent in this method only once, namely for producing the injection mold; the structures formed there with the required precision are then simply copied to the injection-molded part with the same accuracy.
According to a preferred embodiment it is provided that a cooling body is arranged at the bottom of the depression, the latter accommodating the electro-optical component. This cooling body serves the purpose to carry off the dissipated heat, in particular the heat from electro-optical transmission elements. The cooling body can consist of a metal layer, for example, which is simultaneously formed with the metallization of the printed circuit board. In this case the cooling body may be used as one of the terminals for the electro-optical component, if this terminal is connected with the cooling body in an electrically conductive way, for instance by conductive bonding.
According to the preferred embodiment it is further provided that a press fit is present between the electro-optical component and the depression of the printed circuit board. The press fit ensures the precise arrangement of the electro-optical component in the depression, without additional measures for securing the electro-optical component being necessary.
According to a preferred embodiment it is provided that the electro-optical component has a rectangular base and the depression is formed by a circular milled receiving hole, the dimensions of which are smaller than the diagonals of the base, and that four adjustment holes are provided which are assigned to the corners of the electro-optical component and whose lines of intersection with the wall of the milled receiving hole serve for precisely aligning the electro-optical component. It is by means of the milled receiving hole that the depression of the electro-optical component can be formed in a very precise way with an even base. The adjustment holes make it possible to hold the electro-optical component in the milled receiving hole so as to be precisely aligned therein.
According to a preferred embodiment it is provided that the electro-optical component is a component which emits light without preferred direction perpendicular to its surfac
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Cuneo Kamand
Harting Elektro-optische Bauteile GmbH & Co. KG
Vigushin John B.
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