Optomodule

This application claims priority under 35 U.S.C. §§119 and/or 365 to 9902498-6 filed in Sweden on Jun. 30, 1999; the entire content of which is hereby incorporated by reference.

The present invention relates to a plastic-encapsulated optomodule.

Optomodules intended for telecommunications application for instance are normally encapsulated in hermetic metal capsules and are provided with a pigtail for making the optical connection. In order to be able to widen the use of optical signal transmissions it must be possible to produce components and connectors at lower costs than at present, and also to reduce the cost of mounting these components. One of the primary reasons for such high component costs is because of the extremely high mechanical precision that is required in aligning an optoelectric component with a wavequide, such as an optical fibre, and in aligning a waveguide in one component with another waveguide.

Plastic encapsulation, transfer moulding, of optomodules reduces production costs. In present day technology, a plastic capsule that includes optoelectrical components can either be provided with a fibre pigtail of varying length that consists of an optical fibre which extends out from within the component, or a device that is integrated in a capsule wall.

SE 9701833 describes a plastic encapsulated optomodule which includes an integrated optical device.

One problem encountered in the manufacture of plastic encapsulated optomodules, particularly injection moulded modules, that include an optical device integrated in the capsule wall is that the device shall be aligned and fixed in the capsule moulding tool.

The object of the present invention is to eliminate or at least reduce this problem.

This object is achieved by the present invention with a plastic encapsulated optomodule as defined by the claims.

One advantage afforded by the present invention is that no sub-module is required for the optoelectrical component.

Another advantage is that the optoelectrical component can be readily constructed, manufactured and tested relatively inexpensively.

Still another advantage is that the plastic encapsulated optomodule requires little room on a circuit board.

Another advantage is that the present invention the manufacture of new and re-constructed optomodules is facilitated through the medium of a modular construction procedure

The invention will now be described in more detail with reference to preferred embodiments thereof and also with reference to the accompanying drawings.

FIG. 1 illustrates an embodiment of a leadframe included in the invention.

FIG. 2 illustrates an embodiment of electric components that include a ceramic carrier, ASIC and passive components, in accordance with the invention.

FIG. 3 illustrates an embodiment of an optohybrid that includes an optoelectrical component and an optodevice, in accordance with the invention.

FIG. 4 a illustrates from above one embodiment of a plastic encapsulated optomodule having an integrated optical interface in accordance with the invention.

FIG. 4 b is a side view of one embodiment of a plastic encapsulated optomodule having an integrated optical interface in accordance with the invention.

FIG. 5 is an overview of the placement of the leadframe, the electric components and the optohybrid in an injection moulding cavity.

FIGS. 6 and 6 a illustrates from above the alignment of the optodevice with the leadframe, in accordance with a first embodiment.

FIG. 6 b is a side view illustrating alignment of the optodevice with the leadframe in accordance with a first embodiment.

FIGS. 7 and 7 a illustrates from above alignment of the optodevice with the leadframe in accordance with a second embodiment.

FIG. 7 b is a side view illustrating alignment of the optodevice with the leadframe in accordance with a second embodiment.

FIGS. 8 and 8 a illustrates from above alignment of the optodevice with the leadframe in accordance with a third embodiment.

FIG. 8 b is a side view illustrating alignment of the optodevice with the leadframe in accordance with a third embodiment.

FIG. 9 a shows how the leadframes can be arranged relative to one another during encapsulation in accordance with a first embodiment.

FIG. 9 b shows how the leadframes can be arranged relative to one another during encapsulation in accordance with a second embodiment.

FIG. 1 illustrates an embodiment of an inventive leadframe included in a plastic encapsulated optomodule. The leadframe 1 includes a first and a second support device 10 a and 10 b, which function to fixate different parts of the leadframe 1 , for instance leads 5 , prior to encapsulation. The second support device includes alignment elements 50 for aligning the leadframe in an encapsulating mould cavity.

The leadframe includes a first part 20 which is connected to earth via at least one earth lead 5 a. The first part functions, among other things, as a support for an electric component 1 A (see FIG. 2) together with electric contact surfaces 80 at the ends of the leads 5 and 5 a.

A second part 30 functions to support an optoelectric component 2 included in an optohybrid 1 B. A third part 40 functions to support, fix and align an optodevice 3 included in said optohybrid 1 B. The electric component and the optoelectric component may be interconnected electrically via bonding wires.

The electric component 1 A is shown in FIG. 2, from which it will be seen that the electric component 1 A of this embodiment includes a ceramic carrier 9 which carries an electrically conductive pattern 6 , electrical connection surfaces 7 and an ASIC 8 (Application Specific Integrated Circuit). The connection surfaces 7 are connected to electric contact surfaces 80 at the end of the lead 5 . The electric component can be surface soldered or glued to the electric contact surfaces 80 disposed on the end of respective leads 5 and 5 a. The particular configuration of the contact surfaces 80 also has the added function of preventing the leads from being pulled out of the capsule. The ASIC may alternatively be arranged directly on said first part 20 and connected electrically to the leads with the aid of bonding wires.

FIG. 3 illustrates a so-called optohybrid 1 B. The optohybrid includes an optoelectrical component 2 and an optodevice 3 . The optoelectrical component 2 includes a laser 2 a to which one or more optical waveguides 4 are connected. The optical waveguide or waveguides 4 terminates/terminate in a connecting interface 3 b on said optodevice 3 . The optodevice 3 includes a flange 3 a.

FIGS. 4 a and 4 b illustrate the plastic encapsulated optomodule 100 . The leads 5 in the leadframe and the optodevice protrude out from the capsules 60 in the plastic encapsulated optomodule 100 .

FIG. 5 is an overview illustrating the arrangement of the leadframe, on which said optohybrid 1 B and said electric component 1 A are provided, is positioned in a mould cavity 70 for plastic encapsulation by means of transfer moulding. The mould cavity 70 terminates inwardly of the leadframe support devices, so as to enable these devices to be removed from the leads 5 and 5 a subsequent to encapsulation. The mould cavity 70 includes an opening for accommodating the optodevice 3 . A mould tool or die defining said mould cavity is adapted so that the gap between the optodevice and the optodevice-accommodating opening is restricted to some few tens of a micrometer. This prevents plastic from penetrating between the optodevice and the recess which accommodates the optodevice in the mould tool.

FIGS. 6 a and 6 b are enlarged views of the second and third leadframe parts 30 and 40 . FIG. 6 b is a sectional view taken on the line A—A in FIG. 6 a. The optodevice 3 and the optoelectric component are arranged in different planes in the leadframe 1 . This positions the waveguides 4 correctly between the optodevice 3 and the optoelectric component 2 . Tabs 45 are folded-up from the leadframe on the third part 40 of said leadframe 1 where the optodevice 3 is arranged. These tabs are arranged to partially embrace the optodevice 3 such as to fixate said device and align it in a direction orthogonal to the longitudinal direction of the waveguides 4 . The tabs 45 are also arranged to fixate and align the optodevice 3 in a direction parallel with the waveguides 4 , by virtue of said tabs being fixed against an edge of a flange 3 a on the optodevice 3 .

FIGS. 7 and 7 a illustrate another embodiment for aligning and fixating the optodevice with the aid of alignment elements provided on the leadframe. In this embodiment, the third part of the leadframe includes a recess whose position, shape and size conform to those of the flange 3 a provided on the optodevice 3 . When the flange is received in the recess, the device will be fixated in a direction parallel with an orthogonal to the waveguides 4 disposed between the optodevice 3 and the optoelectric component 2 . As with the earlier described embodiment, the third and the second leadframe parts 40 and 30 respectively are disposed in different planes such as to position the waveguides 4 correctly between the optoelectric component 2 and the optodevice 3 .

FIG. 8 illustrates another embodiment for aligning and fixating the optodevice with the aid of alignment elements provided on the leadframe 1 . In this embodiment, the optodevice 3 is arranged on the third leadframe part 40 , which is on a lower level than the remainder of the leadframe. Two tabs 47 a and 47 b are provided on a respective side of the third leadframe part 40 and function to fixate the optodevice 3 in a plane above said third leadframe part, in a direction orthogonal to the longitudinal direction of the waveguides 4 . The tabs 47 a and 47 b include recesses whose shape and size conform to the shape and size of the flange on the optodevice 3 , such as to fixate the optodevice also in a direction parallel to the longitudinal direction of the waveguides 4 .

FIGS. 9 a and 9 b illustrate respective methods of interconnecting the leadframes during manufacture. The leadframes are interconnected resiliently via V-shaped resilient elements 80 a or inclined spring elements 80 b. This enables the positioning tolerance requirement between individual leadframes to be reduced.

It will be understood that the invention is not restricted to the aforedescribed and illustrated exemplifying embodiments thereof and that modifications can be made within the scope of the following claims.