TRANSISTOR OUTLINE PACKAGE AND METHOD FOR PRODUCING A TRANSISTOR OUTLINE PACKAGE

Abstract

A transistor outline (TO) package including a header with at least one optoelectronic device and a pot-shaped metal cap bonded to the header such that a hermetically sealed interior is formed for arranging the at least one optoelectronic device therein. The metal cap includes a window, which is transmissive to electromagnetic radiation, a lateral wall, and an end wall. A portion of the lateral wall and a portion of the end wall are formed with an increased thickness towards the interior compared to a portion of the lateral wall adjacent to the header. The thickened lateral wall portion and the thickened end wall portion have an identical wall thickness.

Claims

1. A transistor outline package, comprising: a header with at least one optoelectronic device; and a pot-shaped metal cap bonded to the header such that a hermetically sealed interior is formed for arranging the at least one optoelectronic device therein, the metal cap including a window being transmissive to electromagnetic radiation, a lateral wall, and an end wall, wherein a portion of the lateral wall and a portion of the end wall are formed with an increased thickness towards the interior compared to a portion of the lateral wall adjacent to the header, the thickened lateral wall portion and the thickened end wall portion having an identical wall thickness.

2. The transistor outline package of claim 1, wherein the thickened lateral wall portion and the thickened end wall portion have a wall thickness which is at least 1.2 times that of the portion of the lateral wall adjacent to the header.

3. The transistor outline package of claim 1, wherein the thickened lateral wall portion and thickened end wall portion have a wall thickness which is less than 5 times that of the portion of the lateral wall adjacent to the header.

4. The transistor outline package of claim 1, wherein the portion of the lateral wall adjacent to the header has a wall thickness of 0.10-0.25 mm,

5. The transistor outline package of claim 4, wherein the thickened lateral wall portion and the thickened end wall portion have a wall thickness of 0.3-1.0 mm.

6. The transistor outline package of claim 1, wherein the metal cap includes a transition area of the lateral wall of the metal cap, at which a wall thickness of the wall changes, and an upper surface of the header is spaced from the transition area of the lateral wall of the metal cap.

7. The transistor outline package of claim 6, wherein the at least one optoelectronic device disposed on the header protrudes below the transition area.

8. The transistor outline package of claim 1, wherein the metal cap is in the form of a deep-drawn cap and the window is in the form of a soldered lens.

9. The transistor outline package of claim 1, wherein the metal cap has an outer diameter of at least one of at least 2 mm and at most 10 mm.

10. The transistor outline package of claim 1, further comprising an optical subassembly with a housing that is bonded to the transistor outline package for connection of a single-mode fiber.

11. The transistor outline package of claim 10, wherein at least one of the metal cap and the housing of the optical sub-assembly is made of a material having a coefficient of linear thermal expansion, averaged between 20 and 300 C., of less than 14 ppm/K, and wherein the metal cap is made of an iron-nickel or nickel-cobalt alloy or of a ferritic stainless steel.

12. The transistor outline package of claim 10, wherein the metal cap and the housing of the optical sub-assembly are bonded to each other through a plurality of weld spots that are distributed irregularly around a circumference of the housing of the optical sub-assembly.

13. The transistor outline package of claim 1, wherein the transistor outline package is one of a TO-41, TO-46, TO-38, and TO-56 type package.

14. The transistor outline package of claim 1, wherein the thickened lateral wall portion at least one of extends over at least 30% and over less than 90% of a height of the lateral wall.

15. The transistor outline package of claim 1, wherein the window is arranged centrally in the end wall, and wherein the lateral wall includes a lower portion which has a smaller wall thickness compared to at least one of a portion of the lateral wall adjacent to the lower portion and the end wall.

16. An assembly, comprising: a transistor outline package including a header with at least one optoelectronic device and a pot-shaped metal cap bonded to the header such that a hermetically sealed interior is formed for arranging the at least one optoelectronic device therein, the metal cap including a window being transmissive to electromagnetic radiation, a lateral wall, and an end wall, a portion of the lateral wall and a portion of the end wall being formed with an increased thickness towards the interior compared to a portion of the lateral wall adjacent to the header, the thickened lateral wall portion and the thickened end wall portion having an identical wall thickness; and an optical sub-assembly for connecting a light-conducting fiber, the optical sub-assembly including a housing that is welded to the metal cap at a location of at least one of the thickened portion of the lateral wall and the thickened portion of the end wall.

17. The assembly of claim 16, wherein the metal cap and the housing of the optical sub-assembly are bonded to each other through a plurality of weld spots that are distributed irregularly around a circumference of the housing of the optical sub-assembly.

18. The assembly of claim 16, wherein the thickened lateral wall portion and the thickened end wall portion have a wall thickness which is at least 1.2 times that of the portion of the lateral wall adjacent to the header.

19. The assembly of claim 16, wherein the metal cap includes a transition area of the lateral wall of the metal cap, at which a wall thickness of the wall changes, and an upper surface of the header is spaced from the transition area of the lateral wall of the metal cap.

20. The assembly of claim 16, wherein the metal cap is in the form of a deep-drawn cap and the window is in the form of a soldered lens.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0064] FIG. 1 shows a sectional view of an embodiment of a TO package according to the invention;

[0065] FIG. 2 illustrates how the TO package of FIG. 1 is connected to an optical sub-assembly. Here, the optical sub-assembly is bonded to the end wall of the metal cap of the TO package;

[0066] FIG. 3 shows an alternative embodiment to FIG. 2, in which the window of the TO package is in the form of a disc;

[0067] FIG. 4 is a plan view of the end face of the TO package according to FIG. 2 or FIG. 3 bonded to the optical sub-assembly;

[0068] FIG. 5 is a sectional view of an alternative embodiment in which an optical sub-assembly is bonded to the lateral wall of the TO package; and

[0069] FIG. 6 is a flowchart of an exemplary embodiment illustrating the method steps for producing an assembly comprising a TO package and an optical sub-assembly.

[0070] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0071] Referring now to the drawings, and more particularly to FIG. 1, there is shown a sectional view of an exemplary embodiment of a TO package 1 according to the present invention.

[0072] TO package 1 includes a header 2 with at least one optoelectronic device disposed on the upper surface 26 thereof.

[0073] In this exemplary embodiment, an emitter 7 is disposed on the header 2, which serves to convert an electrical signal into a light signal. Furthermore, a monitor diode 8 is disposed next to the emitter 7, which is used to control the output power of the emitter 7. The emitter 7 may in particular be implemented as an edge emitter with a mirror (not shown) rotated through 45 relative thereto.

[0074] Header 2 comprises a plurality of electrical feedthroughs, via which the emitter 7 and the monitor diode 8 are electrically connected. These feedthroughs extend out of the lower surface 16 of header 2 in the form of connection pins 4.

[0075] Connection pins 4 may be connected to a printed circuit board, in particular a flexible printed circuit board 5.

[0076] The header 2 may be equipped with an optoelectronic device, which is known per se from the prior art.

[0077] The header 2 is bonded to a metal cap 3 such that a hermetically sealed TO package 1 is formed, with the electronic devices arranged in the interior 6 thereof.

[0078] In particular, the header 2 may be soldered or welded to the lateral wall 11 of the metal cap in a bonding area 17, and/or with a flange 29 to a flange 14 of the metal cap 3.

[0079] The metal cap 3 has a pot-like shape and comprises an end wall 27 from which the lateral wall 11 extends.

[0080] Opposite end wall 27, the metal cap 3 has a laterally protruding flange 14 which serves for improved connection to the header 2 and improved mechanical stability.

[0081] The metal cap 3 has a substantially circular cylindrical shape and comprises a central opening 10 in which a window is arranged, in the present exemplary embodiment in the form of a lens 9. Lens 9 is in particular installed in an opening 10 of the end wall 27 by a solder glass.

[0082] In contrast to the prior art, metal cap 3 has a portion 12 of the lateral wall 11 at least partially adjacent to the header 2, compared to which a portion 13a of the lateral wall closer to the end wall 27 and the adjoining portion 13b of the end wall are formed with an increased thickness.

[0083] In this exemplary embodiment, a transition area 15 is located above the upper surface 26 of the header 2, in particular in the form of a step, where the wall thickness of the deep-drawn metal cap 3 increases. The outer dimensions of the metal cap 3 can correspond to a design type known from the prior art. Due to the increased wall thickness in portions 13a and 13b, mechanical stability is enhanced in these portions and an optical sub-assembly 20 can easily be bonded there by welding. At the same time, due to the thinner portion 12 of lateral wall 11 adjacent to the header 2, heat transfer toward the end wall 27 of the metal cap 3 is reduced.

[0084] Since the transition area 15 is spaced from the upper surface 26 of the header 2, an electronic device may be disposed in the area 28 below transition area 15. Therefore, the surface area on which electronic devices can be mounted on the upper surface 26 of header 2 is advantageously not reduced according to an embodiment of the invention. Furthermore, no modification of the header 2 is required, in particular in terms of its diameter, compared to the prior art.

[0085] FIG. 2 is a schematic sectional view illustrating how the TO package 1 of FIG. 1 is bonded to an optical sub-assembly 20. Optical sub-assembly 20 comprises a housing 18 made of metal, which in this exemplary embodiment includes a light guide 21, preferably in the form of a single-mode fiber. More particularly, the light guide 21 is a single-mode fiber having an outer diameter from 50 to 250 which is inserted in a ferrule, in particular a ceramic ferrule, and which serves for coupling purposes.

[0086] Optical sub-assembly 20 includes a flange 22 where the housing 18 is welded to the end wall 27 of TO package 1, which has the increased thickness. There is no need for a hermetic seal between TO package 1 and optical sub-assembly 20, rather, weld spots are sufficient to join these components.

[0087] In this exemplary embodiment of the invention, the lens 9 focuses the light emitted by the emitter 7 directly onto the end of the light-conducting core of light guide 21. Furthermore, in this exemplary embodiment, the optical sub-assembly 20 comprises a coupling portion 19 which serves to couple a light guide. Coupling portion 19 may in particular be in the form of a plug-in connector.

[0088] FIG. 3 shows an alternative embodiment of the invention, compared to FIG. 2. In contrast to the exemplary embodiment shown in FIG. 2, the cap 3 of TO package 1 is provided with a window not in the form of a lens, but in the form of a disc 23. Instead, the optical sub-assembly 20 includes a lens 24, which, in turn, focuses light onto the end of the core of light guide 21. Optical sub-assembly 20 also comprises a coupling portion 19.

[0089] FIG. 4 is a plan view of the end face of the assembly consisting of TO package 1 and optical sub-assembly shown in FIG. 2 or FIG. 3. It can be seen that the flange 22 of optical sub-assembly 20 is bonded to the end wall 27 of metal cap 3 by a plurality of weld spots 25a to 25g. Weld spots 25a to 25g are set during a test mode, while the monitor diode (8 in FIG. 1) verifies the efficiency of injection into the light guide 21.

[0090] Since stresses are introduced into the material by the weld spots 25a to 25g, due to thermal expansion and due to microstructural changes in the material, the weld spots 25a to 25g can be positioned so as to achieve fine alignment such that the spot projected onto the core of the fiber end through the lens 9, 24 is aligned axially to the core. Weld spots 25a to 25g are therefore distributed in an irregular manner, i.e. they enclose different angles to each other with respect to the central axis.

[0091] FIG. 5 is a schematic sectional view of an alternative embodiment of the invention. According to this embodiment, an optical sub-assembly 20 is connected to a TO package 1, and here the optical sub-assembly is not bonded to the end wall 27 but to the lateral wall 11 of metal cap 3. The corresponding weld spots bonding the housing 18 to the cap 3 (not shown) are arranged in a thickened portion 13a of lateral wall 11.

[0092] The exemplary embodiment of an optical sub-assembly illustrated in FIG. 5 again comprises a light-conducting fiber 21 and a coupling portion 19 for connection to an optical transmission system. Preferably, coupling portion 19 comprises a ferrule with the light-conducting fiber inserted therein.

[0093] Referring to the flowchart of FIG. 6, it will be explained how the TO packages 1 illustrated above can be manufactured. Initially, an annular blank for the metal cap 3 is stamped out of a metal sheet, in particular of a metal sheet made of a low expansion alloy, and is embossed such that an edge portion has a thinner wall thickness than the remaining area of the blank.

[0094] Subsequently, the blank is deep-drawn into a metal cap 3. The deep-drawing is preferably performed in the same tool as the stamping and embossing.

[0095] A window, which can be in the form of a lens 9, is installed in a central opening 10 of the cap and is secured therein, for example using a glass solder.

[0096] Then, the metal cap 3 is welded or soldered to the header 2, which header has already been equipped with an optoelectronic device. The welding is performed under protective gas and produces a gas-tight connection.

[0097] In order to connect the optical sub-assembly 20 to the TO package 1, the latter is first put into a test mode and connected to a measuring device for measuring the output power, via a light guide (not shown) coupled to the optical sub-assembly.

[0098] Optical sub-assembly 10 is placed and adjusted relative to the TO package 1 such that the output power emitted from the TO package 1 becomes maximal, which is continuously monitored by the measuring device. Then, weld spots are initially set to connect the optical sub-assembly 20 and the metal cap 3 to each other (e.g. the three weld spots 25a, 25c, and 25e which are regularly distributed around the circumference).

[0099] Subsequently, further weld spots 25b, 25d, 25f, 25g may be set in order to achieve fine adjustment of the components so as to optimize the signal.

[0100] The invention permits to provide a TO package which is used in particular for a transmitting diode in an optical data transmission network. The TO package allows for simplified attachment of an optical sub-assembly by welding, while the dimensions of known design types and the design of the header are retained.

[0101] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE NUMERALS

[0102] 1 TO package [0103] 2 Header [0104] 3 Metal cap [0105] 4 Connection pin [0106] 5 Printed circuit board [0107] 6 Interior [0108] 7 Emitter [0109] 8 Monitor diode [0110] 9 Lens [0111] 10 Opening [0112] 11 Lateral wall [0113] 12 Portion of lateral wall adjacent to header [0114] 13a Thickened portion of lateral wall [0115] 13b Thickened portion of end wall [0116] 14 Flange [0117] 15 Transition area [0118] 16 Lower surface [0119] 17 Bonding area [0120] 18 Housing [0121] 19 Coupling portion [0122] 20 Optical sub-assembly [0123] 21 Light guide [0124] 22 Flange [0125] 23 Disc [0126] 24 Lens [0127] 25a-25g Weld spots [0128] 26 Upper surface [0129] 27 End wall [0130] 28 Area below transition area [0131] 29 Flange