Structure of impedance signal line of TO-can type semiconductor package

Abstract

Disclosed is a structure of an impedance signal line for a TO-can-type semiconductor package according to an embodiment. The transistor outline (TO)-can-type semiconductor package includes a header including a semiconductor laser diode disposed on one side of the header; a signal line extending through the header and including one end protruding from the side of the header; and an edge-coupled microstrip (ECM) portion connected to the signal line. The ECM portion includes a dielectric and ECM lines. The ECM lines are formed as conductive patterns having a predetermined width and a predetermined spacing on a first side of the dielectric, and are respectively connected to the signal lines.

Description

Technical Field

[0001] Embodiments relate to a structure of an impedance signal line of a transistor outline (TO)-can type semiconductor package. Background Art

[0002] With the recent expansion of demand and widespread use of optical devices, the demand for data transmission using optical fibers in various networks such as local area networks (LANs) has rapidly increased. In particular, research related to high-speed data transmission has been actively conducted, and as a result, various packaged semiconductor laser diodes have been released.

[0003] Figures 1A to 1C is a diagram showing a signal line structure of a conventional TO-can type module package, and Figure 2A and 2B is a diagram showing the results of simulating RF characteristics of a conventional signal line structure.

[0004] refer to Figures 1A to 1C , the structure includes a head 10 with a specific impedance and a signal line 20 passing through the feedthrough. The passing signal line 20 includes a single line or a double line, which are not connected to each other and are used to process differential signals. If necessary, a plurality of signal lines that are not connected to each other may pass through the head 10 together. In this case, the penetration portion is filled with a dielectric 11, which is usually made of a glass material, so that the passing signal line may not be connected to the head portion but isolated from the head portion. By adjusting the dielectric constant of the glass material, the size of the feedthrough hole, the thickness of the passing signal line 20, and the distance between two or more passing signal lines 20, the desired characteristic impedance can be designed. In order to more easily mount a semiconductor laser or similar component to the head, the signal line 20 has been lengthened for use, such as Figure 1B shown.

[0005] When the semiconductor component 40 is actually mounted on a TO-can, a semiconductor laser diode 43 or the like is attached to a ceramic plate 42, and then this ceramic plate 42 is mounted to the head 10. Furthermore, when it is necessary to control the temperature of the semiconductor laser diode 43 by a thermoelectric cooler (TEC) 41, the TEC 41 is attached to the head 10, and then the ceramic plate 42 is attached thereto. In this case, as shown in FIG. Figure 1B and 1C As shown, the signal line 20 penetrating the head 10 is extended above the head 10 and connected to a component such as a laser diode or a signal line of a ceramic board through a bonding wire.

[0006] With this structure, the impedance of the signal line part and the head part are different. Figure 1B and 1CAs shown, the signal line 20 is exposed to the air, and there is no other material around the signal line 20. Therefore, the signal line 20 generally acts as an inductor and increases in inductance as the frequency becomes higher, thus causing a problem: the signal from the head portion cannot be well transmitted to the semiconductor laser or other components on the ceramic board.

[0007] Figure 2A and 2B The S parameters of a header with and without an attached signal line are shown. The S11 of the header without an attached signal line shows a characteristic of -20 dB or even lower at 30 GHz, but the S11 of the header with an attached signal line (i.e., a header with a signal line extended by 1 mm) shows rapidly degraded characteristics.

[0008] Furthermore, S21 of the header without the additional signal line shows a characteristic that is almost flat at 30 GHz or higher, but S21 of the header with the additional signal line shows a characteristic that the bandwidth of -3 dB is limited to approximately 25 GHz.

[0009] Figure 3A and 3B is a diagram showing another structure of a signal line of a conventional TO-can type module package, and Figure 4A and 4B is a diagram showing the results of simulating RF characteristics of another signal line structure.

[0010] refer to Figure 3A and 3B , a dielectric 30 is inserted between the two differential signal lines 20a and 20b to solve Figures 1A to 1C Problem with the structure shown.

[0011] A dielectric 30 is inserted between the two differential signal lines 20a and 20b, and the dielectric constant and thickness of the dielectric 30 are appropriately selected. The two differential signal lines 20a and 20b are attached to the dielectric 30 with solder 31 therebetween. In this way, the portion of the signal line 20 is designed to have the same impedance as the portion of the header 10, so that the entire structure including the header 10 and the signal line 20 can have a desired impedance.

[0012] refer to Figure 4A and 4B Compared to a header without additional signal lines, S11 is slightly improved. The -3dB bandwidth appears at 30 GHz and above, but decreases by 2dB until 20 GHz. Therefore, when the ceramic board, semiconductor devices, and bonding wires are added, the overall bandwidth hardly meets 20 GHz.

[0013] In addition, S21 Figure 2BThe bandwidth of a head-only device without additional signal lines is further deteriorated.

[0014] In a structure with a dielectric insert, when the header is designed to have a desired impedance, the signal line diameter, the distance between the two signal lines, and the dielectric constant of the dielectric are determined. Therefore, the spacing between the signal lines is determined and fixed based on the designed impedance of the header, and the impedance of the signal line section varies depending on the dielectric material inserted between the signal lines. While the impedance is improved by filling the signal lines with dielectric and solder, the improvement is not significant. Furthermore, the bandwidth is more degraded than with only the header without the additional signal lines.

[0015] Therefore, it is necessary to improve RF characteristics while maintaining the structure between the header and the signal line. Summary of the Invention

[0016] The embodiment provides a structure of an impedance signal line of a TO-can type semiconductor package.

[0017] The purpose of the present embodiment is not limited thereto, and may include purposes or effects that, although not explicitly mentioned, may be recognized from the problems described herein or the technical solutions of the embodiments.

[0018] According to one embodiment, a transistor outline (TO)-can type semiconductor package includes: a header including a semiconductor laser diode disposed on one side thereof; a signal line extending through the header and including one end protruding from one side of the header; and an edge-coupled microstrip (ECM) portion connected to the signal line, the ECM portion including a dielectric and ECM lines formed as conductive patterns having a predetermined width and a predetermined spacing therebetween on a first side of the dielectric and respectively connected to the signal lines.

[0019] The ECM wire may include two ECM wires formed to be spaced apart from each other at a predetermined interval, and the dielectric may have a predetermined thickness.

[0020] The ECM portion may also include a ground plane formed at least partially on the second side of the dielectric.

[0021] The signal lines include differential signal lines whose characteristic impedance varies depending on at least one of a width of the ECM lines, a spacing between the ECM lines, a thickness of the dielectric, a type of the dielectric, and a dielectric constant of the dielectric.

[0022] The ECM wires can be soldered to the differential signal wires.

[0023] The ECM wires may be formed to have the same length and the same width.

[0024] The total impedance including the ECM lines and the signal lines can be determined by adjusting the width of the ECM lines, the spacing between the ECM lines, the thickness of the dielectric, the type of the dielectric, and the dielectric constant of the dielectric. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figures 1A to 1C is a diagram showing a signal line structure of a conventional TO-can type module package.

[0026] Figure 2A and 2B is a graph showing the results of simulating RF characteristics of a conventional signal line structure.

[0027] Figure 3A and 3B is a diagram showing another structure of a signal line of a conventional TO-can type module package.

[0028] Figure 4A and 4B : is a graph showing simulation results of RF characteristics of another signal line structure.

[0029] Figure 5A and 5B is a diagram showing a signal line structure of a TO-can type semiconductor package according to an embodiment.

[0030] Figures 6A to 6D 5 is a diagram showing the structure of the edge-coupled microstrip (ECM) portion shown in FIG. 5 .

[0031] Figure 7A and 7B is the first diagram showing the result of simulating the RF characteristics of the proposed signal line structure.

[0032] Figures 8A to 8C is a second diagram showing simulation results of RF characteristics of the proposed signal line structure. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0034] However, the technical ideas of the present disclosure are not limited to some embodiments set forth herein, but may be embodied in various forms, and one or more of the elements may be selectively combined and replaced between the embodiments without departing from the scope of the present disclosure.

[0035] In addition, unless otherwise explicitly defined and described, the terms (including technical and scientific terms) used in the embodiments of the present disclosure may be interpreted as meanings that are generally understood by ordinary technicians in the field to which the present disclosure belongs, and commonly used terms, such as terms defined in dictionaries, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0036] In addition, the terms used in the embodiments of the present disclosure are only used for the purpose of describing the embodiments and are not intended to limit the present disclosure.

[0037] In this specification, the singular form may also include the plural form unless otherwise specifically mentioned, and the description of "at least one (or one or more) of A, B and C" may include one or more of all possible combinations of A, B and C.

[0038] Furthermore, when describing elements in the embodiments of the present disclosure, the terms first, second, A, B, (a), (b), etc. may be used.

[0039] These terms are only used to distinguish one element from another, and do not limit the nature, order, sequence, etc. of the elements.

[0040] When it is described that one element is “connected to,” “coupled to,” or “accesses” another element, these elements may be “connected,” “coupled,” or “accessed” not only directly but also through another element disposed therebetween.

[0041] Furthermore, when it is described that an element is formed or arranged “on (above) or below (under)” another element, these elements may be formed or arranged not only in direct contact with each other but also in contact with one or more other elements therebetween. In addition, the expression “on (above) or below (under)” may include not only an upward direction relative to an element but also a downward direction.

[0042] According to one embodiment, a new structure is proposed in which an edge-coupled microstrip (ECM) line is arranged side by side on one side of two signal lines running through a TO-can header, and the ECM line is attached to each signal line.

[0043] Recent optical communication technologies have achieved transmission speeds exceeding tens of gigabits per second. Consequently, transistor outline (TO)-can-type semiconductor packages including signal lines are required to have bandwidths of tens of gigahertz or higher in order to manufacture transmitter optical subassemblies (TOSAs) and similar optical components required for these transmission speeds. Therefore, the present disclosure proposes a structure that makes the impedance of the signal line as similar as possible to that of the header.

[0044] Figure 5A and 5Bis a diagram showing a structure of a signal line of a TO-can type semiconductor package according to an embodiment, and Figures 6A to 6D 5 is a diagram showing the structure of the ECM portion shown in FIG. 5 .

[0045] refer to Figure 5A and 5B , a TO-can type semiconductor package according to an embodiment of the present disclosure may include a header 100 , a plurality of signal lines 200 , and an ECM portion 300 .

[0046] The head 100 may include semiconductor components 400, namely, a thermoelectric cooler (TEC) 410, a ceramic substrate 420, and a semiconductor laser diode 430, which are sequentially arranged on one side. The head 100 includes a through hole formed to penetrate both sides, and the signal line 200 is connected via the through hole.

[0047] The plurality of signal lines 200 may be connected to the semiconductor laser by a wire bonding method. Here, the wire bonding method is used, but is not limited thereto. For example, the plurality of signal lines 200 may include two differential signal lines 200a and 200b that are not connected to each other to process differential signals.

[0048] In this case, the plurality of signal lines 200 pass through the through-holes such that first ends may protrude from one side of the head 100 and second ends may pass through the through-holes and extend toward the other side of the head 100. The plurality of signal lines 200 may be fixed to the head 100 by a glass material filled in the through-holes.

[0049] For example, a glass material in a powder form may be filled in the through-holes through which the plurality of signal lines 200 pass, and melted at a preset temperature, thereby sealing the through-holes.

[0050] The ECM portion 300 may be arranged side by side on one side of the plurality of signal lines 200 and adhered to the signal lines 200. In other words, the ECM lines made of metal and formed in the ECM portion 300 may be connected to the signal lines 200a and 200b, respectively. Here, the metal material may be a conductive material, for example, copper (Cu), silver (Ag), etc.

[0051] The ECM portion 300 may be disposed on a side opposite to the semiconductor component 400 with respect to the signal line 200 .

[0052] In this case, the ECM wire, whose impedance has been previously calculated, may be soldered to the signal wire 200 by, for example, solder balls (but not limited thereto). Alternatively, the ECM wire may be adhered to the signal wire 200 by laser-based spot welding.

[0053] refer to Figure 6A and 6B, the ECM portion 300 according to the first embodiment of the present disclosure may include a ceramic substrate or dielectric 310 and an ECM wire 320 , and the ECM wire 320 may include two ECM wires 320 a and 320 b .

[0054] On one side of dielectric 310, conductive patterns, namely two ECM lines 320a and 320b, may be formed side by side. Dielectric 310 may be formed to a predetermined thickness, for example, 200 μm, but this thickness may be varied as needed. The shape of dielectric 310 may be, for example, a hexahedron, but is not limited thereto. Alternatively, dielectric 319 may have various shapes.

[0055] The two ECM lines 320a and 320b are formed to have a preset width W at the center of one side of the dielectric 310 and may have the same width. The two ECM lines 320a and 320b are separated by a predetermined distance S (eg, 10 μm from each other), but the distance S may be changed as needed.

[0056] The two ECM lines 320a and 320b may have the same width W and the same length L. The length L of the two ECM lines 320a and 320b may be shorter than or equal to the protruding length of the signal line. Here, the protruding length may refer to the length of the signal line protruding from one side of the head.

[0057] refer to Figure 6C and 6D The ECM portion 300 according to the second embodiment of the present disclosure may include a ceramic substrate or dielectric 310 and an ECM line 320 , and may further include a metal ground plane 330 .

[0058] Two ECM lines 320 a and 320 b may be formed side by side on one side of the dielectric 310 , and a ground plane 330 may be formed in at least a portion, ie, a partial area or an entire area on the other side of the dielectric 310 .

[0059] The ECM portion 300 according to the embodiment can be used with or without a ground plane added to the other side of the dielectric. ECM lines with or without a ground plane are manufactured and attached to the signal lines of a header, adding the header's signal lines to the signal line pattern portion of the ECM, effectively forming an ECM that changes the metal thickness of the ECM lines. In this case, the overall characteristic impedance of an ECM line designed to have a specific impedance may differ slightly from the originally designed impedance due to the addition of the header's signal lines.

[0060] Furthermore, the ECM according to the embodiment is configured to transmit differential signals, and the characteristic impedance of the overall structure including the header is further improved compared to conventional structures. Alternatively, the characteristic impedance of the structure including the two signal lines and the ECM is adjusted to a desired impedance by adjusting the width of the ECM or adjusting the spacing between the ECMs. More specifically, in order to optimize the impedance value to the desired impedance value, a structure in which the signal lines are added to the ECM is simulated when calculating or simulating the impedance of the ECM lines.

[0061] Here, the ECM transmission line is described as an example, but is not limited thereto. Alternatively, other transmission lines can be considered. For example, the transmission line can be designed in the form of a differential coplanar waveguide type.

[0062] When a hermetic seal is required, such as with a TOSA, it is important to select a material that does not emit gases, etc., from the ceramic plate. Furthermore, component manufacturing is performed at frequencies of tens of gigahertz, and therefore, when using ceramic or other dielectric materials, dielectric materials with low radio frequency losses (i.e., low loss tangent) are selected. Any type of dielectric can be used as long as it meets these conditions up to the desired frequency of use. Here, loss tangent may refer to an index representing the loss characteristics of a dielectric.

[0063] By connecting the ECM lines 320 according to the embodiment to the signal lines 200, the combined impedance of the header and signal lines can be improved. In other words, the width of the ECM lines, the distance between the ECM lines, the thickness of the dielectric, the type of dielectric, and the dielectric constant can be controlled to adjust the characteristic impedance of the signal lines to be similar to the impedance of the header. Consequently, the RF characteristics of the TO-can semiconductor package can be improved.

[0064] Figure 7A and 7B is the first diagram showing the result of simulating the RF characteristics of the proposed signal line structure.

[0065] refer to Figure 7A and 7B In the case where a header has a differential characteristic impedance of 34 [Ohm] as an example and a differential signal line protrudes from the top of the header, the differential signal line has a differential characteristic impedance significantly different from the 34 [Ohm] characteristic impedance of the header as described above. As proposed in the present disclosure, by adding an ECM to the differential signal line and adjusting the width of the ECM line, the S parameters of the entire structure including the header and the differential signal line are simulated and compared with the simulated S parameters. Figure 1B and 3AThe results of the proposed structure are compared with those of the structure shown in Figure 1. In this case, the signal line protruding from the top of the header is designed to have a length of 1.1 mm, the ceramic substrate is designed to have a thickness of 200 μm and a dielectric constant of 8.8, and the ECM is designed to have a width of 575 μm and a distance between ECM lines of 10 μm. In addition, the proposed structure 1 does not include a ground plane on the back of the ceramic board, but the proposed structure 2 does.

[0066] As with Figure 1B The structure and Figure 3A Compared with the structure of the proposed structure 1, it can be understood that the proposed structure 2 has significant improvements in RF characteristics. In the case of the proposed structure 1 and the proposed structure 2, it can be understood that S11 is approximately maintained at -10 dB or less up to 30 GHz, and S21 has a bandwidth of -1 dB at 30 GHz or higher.

[0067] It should be understood that compared with the conventional method, S11, S21 and characteristic impedance are all significantly improved.

[0068] Figures 8A to 8C is a second diagram showing the results of simulating RF characteristics of the proposed signal line structure.

[0069] refer to Figures 8A to 8C In another example, in the case where the header has a differential characteristic impedance of 50 [Ohm] and the differential signal line protrudes from the top of the header, the differential signal line has a differential characteristic impedance significantly different from the 50 [Ohm] characteristic impedance of the header. As proposed in the present disclosure, by adding an ECM to the differential signal line and adjusting the width of the ECM line, the S parameters of the overall structure including the header and the differential signal line are simulated and compared with the simulated S parameters. Figure 1B and 3A The results of the proposed structure are compared. In this case, the signal line protruding from the top of the header is designed to have a length of 1 mm, the ceramic substrate is designed to have a thickness of 250 μm and a dielectric constant of 8.8, and the ECM is designed to have a width of 500 μm and a distance between ECM lines of 60 μm. In addition, the proposed structure 1 does not include a ground plane on the back side of the ceramic board, but the proposed structure 2 does.

[0070] As with Figure 1B The structure and Figure 3ACompared to the proposed structure, it can be seen that the proposed structures 1 and 2 have significantly improved RF characteristics. In the case of the proposed structures 1 and 2, it can be seen that S11 is approximately maintained at or below -10 dB up to 30 GHz, and S21 has a bandwidth of -1 dB at 30 GHz or higher. In addition, the characteristic impedance simulation results based on time domain reflectometry (TDR) show that the amount of change is very small compared to the results of conventional methods and other companies.

[0071] It should be understood that S11, S21, characteristic impedance and TDR characteristics are all significantly improved.

[0072] According to one embodiment, ECM wires are arranged side by side on one side of two signal wires passing through a TO-can header, and the ECM wires are attached to the signal wires, respectively, thereby significantly improving RF characteristics while maintaining the structure between the header and the signal wires.

[0073] According to one embodiment, the characteristic impedance value of the signal line is adjusted by changing the width of the ECM line, the distance between the ECM lines, the thickness, type and dielectric constant of the dielectric, etc., thereby reducing the impedance difference between the header and the signal line.

[0074] Various advantages and effects of the present disclosure are not limited to the above description, but will become apparent when the embodiments of the present disclosure are described.

[0075] While several embodiments of the present disclosure have been described, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the disclosure as defined in the following claims.

[0076] Description of Reference Numerals

[0077] 100: Head

[0078] 200: Signal line

[0079] 300: ECM part

[0080] 310: Dielectric

[0081] 320: ECM line

[0082] 330: Ground plane

Claims

1. A transistor outline TO-can type semiconductor package comprising: a head portion including a semiconductor laser diode disposed on one side of the head portion; a signal line, the signal line passing through the head and including an end protruding from one side of the head; as well as an edge-coupled microstrip (ECM) section, the ECM section is connected to the signal line, The ECM part includes: dielectrics; and ECM lines are formed as conductive patterns having a predetermined width on a first side of the dielectric with predetermined spaces therebetween, and are connected to the signal lines, respectively, wherein: The dielectric has a predetermined thickness of 200 μm, The ECM lines are spaced apart from each other by a predetermined distance of 10 μm; and The length of the ECM line is shorter than or equal to a protruding length of the signal line protruding from one side of the head.

2. The TO-can type semiconductor package according to claim 1, wherein The ECM wire includes two ECM wires formed to be spaced a predetermined distance apart from each other, and the dielectric has a predetermined thickness.

3. The TO-can type semiconductor package according to claim 1, wherein The ECM portion also includes a ground plane formed at least partially on the second side of the dielectric.

4. The TO-can type semiconductor package according to claim 2, wherein The signal line includes a differential signal line whose characteristic impedance varies depending on at least one of the width of the ECM line, the spacing between the ECM lines, the thickness of the dielectric, the type of the dielectric, and the dielectric constant of the dielectric.

5. The TO-can type semiconductor package according to claim 4, wherein The ECM wires are soldered to the differential signal wires.

6. The TO-can type semiconductor package according to claim 1, wherein The ECM lines are formed to have the same length and the same width.

7. The TO-can type semiconductor package according to claim 1, wherein The total impedance including the ECM lines and the signal lines is determined by adjusting the width of the ECM lines, the spacing between the ECM lines, the thickness of the dielectric, the type of the dielectric, and the dielectric constant of the dielectric.

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