TRANSISTOR OUTLINE HOUSING WITH HIGH RETURN LOSS

Abstract

A transistor outline housing is provided that includes a header for an optoelectronic component. The header has electrical feedthroughs in the form of connection pins embedded in a potting compound. The header has a recess in which at least one of the connection pins in one of the feedthroughs extends out of the lower surface of the header.

Claims

1. A transistor outline housing, comprising: a header for an optoelectronic component, the header having at least one electrical feedthrough in the form of connection pins embedded in a potting compound, the header having a recess, at least one of the connection pins in one of the feedthroughs extends out of a lower surface of the header.

2. The transistor outline housing of claim 1, wherein the potting compound is glass.

3. The transistor outline housing of claim 1, wherein the recess is in the lower surface of the header.

4. The transistor outline housing of claim 1, wherein two of the connection pins extend out of the lower surface in the recess.

5. The transistor outline housing of claim 1, wherein the recess is filled with a material having a lower dielectric constant than the potting compound.

6. The transistor outline of claim 1, wherein the recess has a cross-sectional shape that is circular or an elongated hole.

7. The transistor outline housing of claim 1, wherein the recess has a length from 1 to 5 mm, a width or diameter from 0.3 to 3 mm, and a depth from 0.1 to 1.5 mm.

8. The transistor outline housing of claim 1, wherein the feedthrough has a width or a diameter from 0.7 to 1.4 mm or a length from 1.45 to 2.35 mm.

9. The transistor outline housing of claim 1, wherein two connection pins are arranged in a feedthrough have a spacing between 0.5 and 0.95 mm.

10. The transistor outline housing of claim 1, wherein the at least one connection pin in the feedthrough has a diameter from 0.2 to 0.5 mm.

11. The transistor outline housing of claim 1, wherein the recess has a width or diameter from 1.2 to 5 times that of the feedthrough.

12. The transistor outline housing of claim 1, wherein the recess occupies 20 to 50% of a height of the header at least in an area adjacent to the recess.

13. The transistor outline housing of claim 1, further comprising a conductor trace section in the recess, the conductor trace section in the recess having an impedance that is higher by 1.2 to 4 times than that of a conductor trace section in the electrical feedthrough.

14. The transistor outline housing of claim 1, further comprising an optoelectronic component connected to a conductor trace, a signal path extending between a connection point on the conductor trace and a connection point on the optoelectronic component having an impedance of in a range selected from a group consisting of between 40 and 60 , between 20 and 30 , and between 90 and 110 .

15. The transistor outline housing of claim 1, wherein the connection pins are connected to a printed circuit board, wherein at least one connection point between the printed circuit board and the connection pin is located at a level of the lower surface of the header.

16. The transistor outline housing of claim 15, wherein the printed circuit board is a flexible printed circuit board.

17. The transistor outline housing of claim 1, wherein the recess has a width or a diameter that is from 1.0 to 4.0 times a diameter of the electrical feedthrough.

18. The transistor outline housing of claim 1, wherein the recess has a width or a diameter that is from 1.5 to 5.0 times a diameter of a portion of the connection pin located within the electrical feedthrough.

19. The transistor outline housing of claim 1, wherein the header consists of a single layer.

20. The transistor outline housing of claim 1, further comprising a signal path that exhibits a return loss, wherein the return loss either forms a plateau in a range from 10 to 20 GHz, within which the return loss is between 10 and 35 dB, or ranges between plus/minus 2.5 dB in a range from 10 to 20 GHz.

21. A method for producing a transistor outline housing, comprising: stamping a header for an optoelectronic component, the header having at least one electrical feedthrough in the form of connection pins embedded in a potting compound; and embossing a recess in a lower surface of the header, at least one of the connection pins in one of the feedthroughs extends out of the lower surface of the header.

22. The method of claim 21, wherein the recess is embossed during the stamping.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The subject-matter of the invention will now be explained in more detail by way of exemplary embodiments with reference to the drawings of FIGS. 1 to 9.

[0049] FIG. 1 is a plan view of the upper side of the header of an exemplary embodiment of a TO housing according to the invention, which is already equipped with an optoelectronic component.

[0050] FIG. 2 is a perspective view of the lower surface of the TO housing illustrated in FIG. 1.

[0051] FIG. 3 shows, also in a perspective view, the lower surface of an alternative embodiment of a TO housing, in which two separate connection pins are arranged each in a respective feedthrough.

[0052] FIG. 4 is a detailed view of a recess together with a feedthrough with at least one connection pin, which serves to explained in greater detail the dimensioning of the feedthrough and of the recess.

[0053] FIG. 5 is a schematic side view of a TO housing according to the invention.

[0054] FIG. 6 shows how the TO housing illustrated in FIG. 5 is connected to a PCB.

[0055] FIG. 7 is a graph showing the return loss.

[0056] FIG. 8 is a graph showing the insertion loss of a TO housing according to the invention, plotted as a function of frequency in each case.

[0057] FIG. 9 is a schematic sectional view of a further embodiment of a TO housing, in which a recess is also provided in the upper surface.

DETAILED DESCRIPTION

[0058] FIG. 1 shows a plan view of the upper side of the header 2 of a TO housing 1 according to the invention. The complete TO housing 1 may comprise a cap with a window (not shown) fitted to this header 2.

[0059] Header 2 has a circular cylindrical shape in this exemplary embodiment and may in particular consist of a stamped metal part.

[0060] More particularly, the header 2 may consist of steel. Furthermore, the header may have a coating, in particular a gold-containing coating.

[0061] The header 2 provides a mounting area for an optoelectronic component 6.

[0062] The optoelectronic component 6 of this exemplary embodiment comprises a photodiode 7 which is mounted on an amplifier 8.

[0063] In this exemplary embodiment, the TO housing 1 comprises connection pins 3a and 3b in the form of signal conducting connection pins for the input and output signals.

[0064] Connection pins 3a and 3b are embedded in a potting compound 5, in particular a potting compound 5 made of glass, thereby defining an electrical feedthrough.

[0065] Bonding wires 9a, 9b are used to connect the connection pins 3a and 3b to the optoelectronic component 6 within the TO housing.

[0066] It will be understood that such a TO housing 1 usually comprises further connection pins 4 which may also be embedded in a potting compound, in particular a glass potting compound.

[0067] In contrast to connection pins 3a and 3b, however, connection pins 4 do not serve for transmitting input or output signals, but are used for power supply or as a control line for the optoelectronic component 6. Therefore, less stringent requirements on the impedance characteristics are usually imposed on the signal paths through connection pins 4.

[0068] FIG. 2 shows the TO housing 1 illustrated in FIG. 1 in a perspective view of the lower surface 11. It can be seen that the feedthrough with connection pins 3a and 3b, which comprises the potting compound 5 and the connection pins 3a, 3b is arranged in a recess 10. In this exemplary embodiment, two connection pins 3a, 3b are arranged in a single feedthrough.

[0069] Recess 10 has the shape of an elongated hole, and as a result thereof the connection pins 3a, 3b exit from the header 2 not at the level of lower surface 11 but spaced therefrom, namely approximately at the level of the bottom of recess 10.

[0070] The further connection pins that do not serve as a signal line (4 in FIG. 1) are not shown in this view, for the sake of clarity.

[0071] The header 2 is preferably formed in one piece, and the recess 10 is in particular embossed.

[0072] FIG. 3 shows an alternative embodiment of a TO housing 1 as compared to FIGS. 1 and 2. In this embodiment, a respective single connection pin 3a, 3b is arranged in a respective feedthrough. Thus, each feedthrough consists of a single connection pin 3a, 3b and a potting compound 5 in which the connection pin 3a, 3b is embedded.

[0073] In this exemplary embodiment, two separate recesses 10 are provided so that the feedthrough of each connection pin 3a, 3b is arranged in a separate recess 10.

[0074] The respective recess 10 therefore has a circular cylindrical shape in this embodiment.

[0075] In the exemplary embodiment as illustrated here, the header 2 consists of two layers. However, it will be appreciated that the embodiment with two separate feedthroughs as illustrated in FIG. 3 may as well consist of one layer.

[0076] Otherwise, the exemplary embodiment illustrated in FIG. 3 may be similar to the exemplary embodiment illustrated above in FIGS. 1 and 2.

[0077] Referring to FIG. 4, the preferred dimensioning of the recess and the feedthrough will be explained in more detail by way of an exemplary embodiment which, however, applies to all embodiments of the invention and not just to the embodiments illustrated in the preceding drawings.

[0078] In the case that two connection pins 3a, 3b are arranged in a feedthrough 14, as shown herein, the recess 10 has a length L.sub.c from 1 to 5 mm, preferably from 1.2 to 2.75 mm. Furthermore, the recess preferably has a width d.sub.c from 0.3 to 3 mm, more preferably from 0.7 to 1.8 mm.

[0079] In the case of a circular cylindrical recess 10 for a feedthrough with a single connection pin (not shown here), the recess has a diameter d.sub.c from 0.3 to 3 mm, preferably from 0.7 to 1.8 mm.

[0080] The recess 10 preferably has a depth from 0.1 to 1.5 mm, more preferably from 0.4 to 0.8 mm.

[0081] The potting compound 5 may have a width, or in the case of a circular cylindrical configuration for a single connection pin a diameter, d.sub.g, from 0.7 to 1.4 mm, and/or a length l.sub.g from 1.45 to 2.35 mm.

[0082] In the case of a feedthrough 14 with two spaced apart connection pins 3a, 3b, the spacing p may range between 0.5 and 0.95 mm.

[0083] The diameter of an individual connection pin 3a, 3b in the feedthrough 14 is preferably from 0.2 to 0.5 mm.

[0084] The connection pins 3a, 3b may have a thickened head or may be formed so as to extend along an angle inside the housing, which may in particular serve to reduce the length of the bonding wires (9a, 9b in FIG. 1).

[0085] Preferably, the recess has a width that is from 1.2 to 1.5 times, preferably from 1.5 to 2 times the size of the feedthrough 14, or a diameter that is from 1.2 to 5 times, preferably from 1.5 to 2 times the size of the feedthrough 14.

[0086] FIG. 5 shows a schematic sectional view of the TO housing 1 illustrated in FIGS. 1 and 2.

[0087] It can be seen that the feedthrough 14 defined by the potting compound 5 and the portion of the connection pin 3a arranged in the potting compound 5 extends through the header 2.

[0088] In this exemplary embodiment, the connection pin 3a (preferably also the connection pin 3b) has a thickened head 12. This allows to reduce the length of the bonding wire 9a which is used to connect the connection pin 3a to the optoelectronic component 6.

[0089] Below the feedthrough, the recess 10 is provided, which causes the potting compound 5 and thus the feedthrough to end above the lower surface 11 of header 2, in particular approximately at the level of the bottom of the recess 10.

[0090] FIG. 6 shows how a printed circuit board 13, in particular a flexible printed circuit board 13, is now connected to the TO housing 1. Printed circuit board 13 is applied to the lower surface (11 in FIG. 5) of the header 2, that means at least its upper surface lies at the level of the lower surface of header 2.

[0091] Due to the recess 10, the connection area 15 between printed circuit board 13 and connection pin 3a is spaced apart from the feedthrough 14.

[0092] The spacing between the connection area 15 and the feedthrough 14 corresponds substantially to the depth t of the recess 10.

[0093] As the recess 10 is either provided as a cavity or is filled with a material having a lower dielectric constant than the potting compound 5, an inductance is resulting.

[0094] Connection of the printed circuit board 13 and ensuring a predefined spacing between the connection area 15 and the feedthrough 14 is easily feasible.

[0095] For connection, the contact trace of the printed circuit board 13 can be perforated. Then, connection pins 3a, 3b are inserted into the respective hole until the printed circuit board 13 abuts on the lower surface of the header 2, and the connection area 15 can be easily connected by soldering.

[0096] The other connection pins 4 can be contacted in the same manner, but without there being a recess below the feedthrough of connection pins 4, so that the printed circuit board 13 will directly adjoin the respective feedthrough of one of these connection pins 4.

[0097] It can also be seen that in the exit area 16 of the feedthrough 14, the potting compound 5 may pull up on the connection pin 3a during melting. In this case, the connection pin 3a will be wrapped by a portion of potting compound 5 above the bottom of the recess 10 as well. This can optionally be compensated for by a correspondingly deeper recess 10.

[0098] The graph in the view of FIG. 7 shows the return loss, in dB, of an exemplary embodiment of a TO housing according to the invention (solid line) in comparison to a TO housing without a recess (dashed line).

[0099] The frequency in GHz is represented on the x-axis, and the return loss in dB on the y-axis.

[0100] Return loss is the logarithmic ratio between the reflected signal and the input signal. The greater the return loss, the better the impedance matching of the components. For example, if the return loss is 3 dB, only 50% of the signal will be transmitted, while at 10 dB still 90%.

[0101] As can be seen, a plateau is formed in a frequency range from 10 to 20 GHz, and at 10 GHz the return loss is already about 5 dB higher.

[0102] In the TO housing without recess, the return loss continuously increases, also in the range from 10 to 20 GHz preferably intended for applications.

[0103] At 20 GHz, it was possible with the inventive design of the TO housing to achieve a return loss that was higher by more than 5 dB.

[0104] In particular, it was possible to provide a TO housing in which the return loss is between 15 and 20 dB within the entire range between 10 and 20 GHz.

[0105] Above 20 GHz, the return loss decreases continuously also in the TO housing of the invention, and above 30 GHz it is even lower than in the TO housing without a recess. Therefore, the TO housing of the invention is particularly suitable for applications above 10 GHz but below 20 GHz.

[0106] FIG. 8 shows, in a similar view, the insertion loss of a TO housing according to the invention (solid line) in comparison with a TO housing without recess (dashed line).

[0107] It can be seen that the TO housing of the invention also exhibits improved insertion loss. Insertion loss is lower within the entire frequency range between 10 and 20 GHz.

[0108] It goes without saying that a highest possible return loss and a low insertion loss is desired to be achieved in the frequency range used for the respective application.

[0109] It is of particular advantage that a nearly constant return loss is achieved by the invention in a wide frequency range.

[0110] FIG. 9 is a schematic sectional view of a further embodiment of a TO housing 1 in which the header 2 has a respective recess 10a, 10b both on the upper side and on the lower side.

[0111] The connection pin 3a extends through the header 2 in the feedthrough 14 within recesses 10a, 10b.

[0112] Otherwise, the TO housing may correspond to the previously described TO housing.

[0113] In another embodiment, not shown, a recess may as well only be provided on an upper side.

List of Reference Numerals

[0114] 1 TO housing [0115] 2 Header [0116] 3a, 3b Connection pin [0117] 4 Connection pin [0118] 5 Potting compound [0119] 6 Optoelectronic component [0120] 7 Photodiode [0121] 8 Amplifier [0122] 9a, 9b Bonding wire [0123] 10, 10a, 10 Recess [0124] 11 Lower surface [0125] 12 Head [0126] 13 Printed circuit board [0127] 14 Feedthrough [0128] 15 Connection area [0129] 16 Exit area