HK1024881B - Method and means for microreplication in metal - Google Patents

Description

Method and apparatus for performing microreplication on metal

Technical Field

The present invention relates to a method of micro-replication on metal, to an apparatus for producing a micro-replica on metal and to a metal micro-replicated element produced according to the invention. The microreplication methods and apparatus are preferably intended to produce, with high precision and low cost, optical components of a reproducible construction, contact devices, or other precision elements suitable for aligning an optical chip with a waveguide or fiber. An optical component construction element with alignment convenience can be easily mounted on a circuit board while being connected to a waveguide or a fiber and to a laser or a photodiode.

Description of the prior art

A conventional method for aligning an optical chip with a waveguide or fiber in an optical component is to etch a desired microstructure in the form of a V-groove in which the waveguide or fiber can be assembled into the silicon. With the prior art, the optical chips are often soldered to a ceramic or silicon carrier. This approach quickly raises heat dissipation issues arising in the mounted components, which are particularly acute in the case of small-sized semiconductor lasers mounted, where the heat-generating region is concentrated in a narrow-band region of about 2 μm that extends laterally across the chip and near its surface.

Summary of The Invention

The invention aims to provide a method and a device for performing micro-replication on metal, which can overcome the defects of the prior art and perform micro-replication on metal at low cost and high precision.

A method according to the invention for realizing microreplication on metal by embossing at least one groove, for example a V-groove, on a metal surface with the aid of an embossing tool in order to be able to align at least one waveguide or at least one fibre, wherein the groove is intended to receive a waveguide or a fibre in order to align the waveguide or fibre, for example, with a laser or a photodiode mounted on the metal surface, is characterized in that an active part of the embossing tool for embossing the groove on the metal surface is manufactured by nickel plating on a silicon disc in which the structuring has been etched, wherein the manufactured metal structuring has a structuring which, during embossing, will form at least one waveguide or fibre receiving groove, for example a V-groove, on the metal surface.

Apparatus for effecting microreplication on metal to form a structure for alignment of, for example, at least one waveguide or fiber, according to the invention is an embossing tool whose active portion has a topography that will form at least one groove, for example a V-groove, on the metal surface when embossing the metal surface, wherein the groove is intended to receive a waveguide or fiber such that the waveguide or fiber is aligned with, for example, a laser or a photodiode mounted on the metal surface, characterized in that the active portion comprises a nickel-plated and planarized metal element separated from a silicon disk on which the structure has been etched, wherein the metal structure has a topography that will form at least one waveguide or fiber receiving groove, for example a V-groove, on the metal surface during embossing.

In order to prevent the chip from being damaged by its heating, or at least to limit the effects of this heating, a chip carrying waveguides or fibre connections is soldered to a metal carrier or metal lead frame, whereby its thermal resistance is much smaller than when the chip is soldered to a ceramic or silicon carrier. The invention enables microstructures to be produced at low cost and with high precision in terms of alignment of the waveguide or fiber on the metal surface by means of an embossing/embossing tool.

The embossing process may be performed on a metal carrier or directly on a metal lead frame for plastic encapsulation. The embossing process can be easily automated because the material to be embossed can be processed in the form of short strips or long strips wound on reels. An arrangement in which the optical chip is soldered to a metal carrier provided with an embossed waveguide or fibre receiving groove will improve the dissipation of heat, thereby greatly increasing the useful life and extending the mean time to failure (MFT) of the finished component.

Brief Description of Drawings

Fig. 1 shows a metal element provided with a microstructure according to the invention.

Fig. 2A and B show a bottom view and a cross-sectional view, respectively, of the inventive imprinting tool.

Fig. 3A and B are detailed side and top views of the active portion of the inventive imprinting tool.

Detailed description of the preferred embodiments

Practical tests have shown that microstructures can be imprinted on copper with repeated high measurement accuracy and with only slight wear on the imprinting tool used. The imprinted microstructure on the metal carrier makes it possible to align and mount the optical component directly on a copper leadframe or a leadframe made of some other alloy, for example, for later encapsulation as a structural element in a plastic encapsulation.

The embossing technique has two distinct advantages over the known techniques; in the prior art, the laser is mounted on a carrier, which in turn is mounted on a leadframe. First, the expense involved in purchasing and manufacturing such carriers is eliminated. Secondly, advantages are provided with respect to the dissipation of heat generated in the active area of the laser. However, the additional expense of the imprinting process and the tools required therefor is increased. Precision tools for imprinting microreplicates can be made by grinding or other methods that directly work on the tool material, or in the following ways, for example:

-applying photoresist on a silicon disc.

Mounting a photomask with the appropriate trench pattern on the silicon disk.

-exposing the photoresist present in those openings of the photomask.

Washing away the exposed resist or the unexposed resist.

-etching the desired configuration on the disc.

Washing away the photoresist residue.

This can result in a plurality of mutually identical three-dimensional silicon structures in the case of a two-dimensional photomask. The above techniques are known in the art, but are described herein to better fully illustrate the process used to manufacture imprint tools with the required accuracy. This process can be implemented in either of two alternative ways as described below.

The method A comprises the following steps:

1. a shaped silicon disc is coated with a layer of material having sufficient hardness.

2. The disc is plated with nickel or some other suitable material.

3. The plating is planarized.

4. The silicon disk is etched to separate the plated and planarized mold therefrom. Plated surface

Can be applied by sputtering or further coating the surface with a suitable material

And (4) improving.

5. The molded part is sawn into two pieces in order to separate mutually identical structural parts.

6. A structure is placed in a holder of a stamping tool, which holder is adapted to the structure.

7. The various components of the stamping tool are assembled to form a complete stamping tool.

The method B comprises the following steps:

items 1-4 following procedure A.

5. The non-planarized side is coated with a later detachable layer.

6. The disk is plated with nickel or some other metal.

7. The plating is planarized.

8. The two planarized molded parts are separated from each other.

9. The molded part is cut into two pieces in order to separate the mutually identical components.

10. The molded part is placed in a holder and spark machined in an Electrical Discharge Machine (EDM).

11. The spark-erosion is carried out directly in the material in which the microstructure is to be imprinted

On the metal/lead frame.

12. The various components of the stamping tool are assembled to form a complete stamping tool.

Fig. 1 shows an example of a microstructure imprinted on a metal element 1, having a concave or depressed surface 2, the surface 2 comprising a V-groove 3 for aligning an optical fibre or a waveguide. To facilitate mounting of a chip, the metal surface may also be provided with a chip mounting surface 4. The surface 4 comprises chip locating marks in the form of grooves 5. The stamped metal surface enables a chip to be aligned with a waveguide or a fiber with high precision.

As shown in fig. 2A and B, the imprint tool 6 may have the form of a stamp, with a protective holder 8 disposed around the active portion 7 of the tool. The active tool portion will suitably have a configuration for embossing grooves, such as V-grooves, into the metal surface. The protective holder will bear resiliently against, for example, a polyurethane rubber (Adiprene) plate 9 to expose the active tool part during the embossing process.

Fig. 3A and B show that the active portion 7 may be formed with a stamping surface. The surface comprises in this case a flat surface 10 and a ridge portion 11 to form a flat surface or a concave surface and a V-groove when stamping a metal surface. To enable the optical fibre to fit within the V-groove, the active tool portion may have a width of, for example, 1.20mm, and the ridge may be 0.16mm wide, 3.20mm long and at an angle α of 45 °.

Such microreplication on metal, carriers such as those in the form of lead frames and tape, can be automatically formed with V-grooves during manufacture and attached to a chip such as a laser or photodiode. So that the waveguide or fibre can be automatically aligned by means of the embossed grooves in order to achieve correct alignment of the waveguide or fibre with the carrier on which the laser or photodiode is mounted. The imprint technique of the present invention enables microscopic replication in an automated manufacturing process with high reliability and low cost, high accuracy.

It will be understood that the invention is not limited to the exemplary embodiments thereof described above and shown, and that many modifications are possible within the scope of the following claims.

Claims (4)

1. A method of achieving microreplication on metal by means of an embossing tool to form a structure on a metal surface by embossing at least one groove, such as a V-groove, on the metal surface to enable alignment of at least one waveguide or at least one fiber, wherein the groove is intended to receive a waveguide or a fiber to align the waveguide or fiber with, for example, a laser or a photodiode mounted on the metal surface, characterized in that an active part of the embossing tool used to emboss the groove on the metal surface is manufactured by nickel plating on a silicon disc in which the structure has been etched, wherein the metal structure produced has a structure which, during embossing, will form at least one waveguide or fiber receiving groove, such as a V-groove, on the metal surface.

2. Device for effecting microreplication on metal to form a structure for alignment of, for example, at least one waveguide or fibre, which device is an embossing tool the active part of which has a topography which, when embossing a metal surface, will form at least one groove, for example a V-groove, in the metal surface, wherein the groove is intended to receive a waveguide or fibre in order to align the waveguide or fibre with, for example, a laser or a photodiode mounted on the metal surface, characterized in that the active part (7) comprises a nickel-plated and planarized metal element separated from a silicon disc on which the structure has been etched, wherein the metal structure has a topography (11) which topography (11), during embossing, will form at least one waveguide or fibre receiving groove, for example a V-groove, in the metal surface.

3. The device according to claim 2, characterized in that the nickel-plated surface of the active part (7) is sputtered or further coated with a suitable metal to increase the hardness of the active part.

4. Device according to claim 2, characterized in that a protective elastic holder (8) is arranged around said active portion (7) in order to expose it during embossing.