Optical communication module substrate

Abstract

An optical communication module substrate is formed by connecting a wiring substrate (20) and an optoelectronic hybrid substrate (30). The connection terminals (22) of the wiring substrate (20) and the connection terminals (35) of the optoelectronic hybrid substrate (30) form electrical connection points. A portion of the metal reinforcing layer (37) of the optoelectronic hybrid substrate (30), sandwiching an insulating layer (31) and facing the connection terminals (35), is removed for each terminal in a manner that surrounds the terminal, forming a frame-shaped removal portion (60). This structure sufficiently ensures the connection strength at the connection point between the wiring substrate and the optoelectronic hybrid substrate, and also possesses excellent electrical characteristics capable of handling high-speed signal transmission.

Description

Technical Field

[0001] This invention relates to an optical communication module substrate formed by connecting a wiring substrate (including a wiring circuit substrate) and an optoelectronic hybrid substrate, and more particularly to an optical communication module substrate with excellent reliability for high-frequency signals. Background Technology

[0002] In recent electronic devices, with the increase in the amount of information transmitted, optical wiring is used in addition to electrical wiring. It is recommended to use optoelectronic hybrid substrates that compactly incorporate both electrical and optical wiring. In addition, optical communication modules that further connect the aforementioned optoelectronic hybrid substrates to wiring substrates with signal transmission functions for transmitting signals to various electronic devices are also widely used for high-speed signal transmission.

[0003] An example of such an optical communication module is schematically shown in Figure 13 The optical communication module is formed by integrally connecting the optoelectronic hybrid substrate 2 and the wiring substrate 1. To explain in more detail, firstly, an electrical wiring X is provided on the surface of the wiring substrate 1, which is formed by arranging multiple pairs of wirings for differential signal transmission.

[0004] Furthermore, the aforementioned optoelectronic hybrid substrate 2 includes an insulating layer 3 (represented by a thicker diagonal line in the figure). This insulating layer 3 has a wider portion and a narrower portion. A circuit section 6 is provided on the back side of the wider portion of the insulating layer 3, that is, on the surface overlapping with the surface of the wiring substrate 1. This circuit section 6 includes an electrical wiring Y formed by arranging multiple pairs of wirings for differential signal transmission, an optical element 4, and an IC 5 for driving the optical element 4. Additionally, a metal reinforcing layer 7 for reinforcing the circuit section 6 is provided on the surface side of the insulating layer 3. Similarly, a strip-shaped optical waveguide 8 is provided on the surface side of the insulating layer 3 in a manner that partially overlaps with the metal reinforcing layer 7.

[0005] In the aforementioned optical communication module, the connection portion of the electrical connection between the wiring substrate 1 and the optoelectronic hybrid substrate 2 is shown as an enlarged and schematic representation. Figure 14 As shown, the connection terminals at the ends of the electrical wirings X and Y are arranged in an overlapping manner, and the two are connected using solder bumps or the like, thereby achieving an electrical connection between the wiring substrate 1 and the optoelectronic hybrid substrate 2. In the figure, the connection point is indicated by the reference numeral P.

[0006] In optical communication modules like the one described above, controlling the impedance at connection point P becomes a crucial issue when the substrates are electrically connected. This is because, especially in optical communication modules that transmit differential signals with fine wiring pitch or high-frequency signals, the transmitted signals are extremely delicate. Therefore, if there is an impedance mismatch at connection point P, the signal transmission efficiency may be significantly reduced.

[0007] However, in the construction of the suspension substrate and the wiring circuit substrate that connect the circuit, the following technique is proposed: the portion of the metal reinforcing layer of the wiring circuit substrate that overlaps with the terminal portion that becomes the connection point between the substrates is partially opened in advance, thereby removing the electrostatic capacitance component generated between the metal reinforcing layer and the terminal portion, and avoiding a significant reduction in the impedance of the connection point relative to the differential impedance of the differential signal wiring (see Patent Document 1).

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2004-363205 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] Therefore, based on the same idea as this technology, a similar technology has been proposed for optical communication modules: a substrate with an opening formed by removing the portion of the metal reinforcing layer located on the back side of the insulating layer of the optoelectronic hybrid substrate, which sandwiches the insulating layer and faces the connection terminal (connection point P) of the electrical wiring Y on the opposite side. For example, the following technology has been studied: Figure 15 As shown in (a), in the metal reinforcement layer 7 of the optoelectronic hybrid substrate 2, which is part of the optical communication module, the electrical wiring Y (refer to) is removed. Figure 13 The portions of the terminals facing each other at the front end of the optical element form an opening 10 with a profile larger than that of the terminal. In addition, in the figure, the through hole 50 is usually provided in the metal reinforcement layer 7 and is a through hole for optical coupling between the optical element and the optical waveguide.

[0013] In addition, based on the same idea, the following technologies were also studied: such as Figure 15 As shown in (b), in the metal reinforcement layer 7, a strip-shaped opening 11 is formed not only in the portion opposite to each terminal, but also in the portion along each wire of the electrical wiring Y.

[0014] However, in the above structure, although the electrical characteristics at the connection point P are improved, when the terminals are pressed together to connect the terminals on the optoelectronic hybrid substrate 2 side and the terminals on the other wiring substrate side, the metal reinforcing layer 7 becomes open and falls off on the optoelectronic hybrid substrate 2 side. Therefore, there is a problem that the function of the reinforcing plate is lost and the connection strength at the connection point P becomes insufficient.

[0015] Therefore, priority should be given to ensuring mechanical strength, for example, such as Figure 16 As shown in (a), the following optical communication module substrate is still used: no opening is provided in the portion of the metal reinforcement layer 7 that is opposite to the connection point P and the electrical wiring Y, or, as Figure 16 As shown in (b), an opening 11 is provided only in the part opposite to the part that becomes the connection point P, but only in the part opposite to the electrical wiring Y. As mentioned above, due to the requirements of high frequency of signals and fine spacing of wiring, there is a strong demand to develop a technology that ensures mechanical strength while improving the electrical characteristics at the connection point P.

[0016] The present invention was made in view of the following situation, and provides an optical communication module substrate that sufficiently ensures the connection strength at the connection point P and has excellent electrical characteristics that can cope with high-speed signal transmission.

[0017] Solution for solving the problem

[0018] That is, the present invention provides the following [1] to [5].

[0019] [1] An optical communication module substrate, which is an optical communication module substrate formed by connecting a wiring substrate and an optoelectronic hybrid substrate, wherein...

[0020] The wiring substrate includes electrical wiring X and terminals for connection.

[0021] The optoelectronic hybrid substrate includes: an insulating layer; a circuit section disposed on a first surface of the insulating layer, having pads for mounting optical elements, electrical wiring Y, and terminals for connection; a metal reinforcing layer disposed on a second surface of the insulating layer; and an optical waveguide, which is also disposed on the second surface of the insulating layer with a portion overlapping the metal reinforcing layer.

[0022] The connection terminals of the wiring substrate and the connection terminals of the optoelectronic hybrid substrate form electrical connection points.

[0023] The metal reinforcing layer of the optoelectronic hybrid substrate is removed in a frame-shaped removal portion at the portion that sandwiches the insulating layer and faces the connection terminal of the electrical wiring Y provided on the opposite side, in a manner that surrounds the terminal.

[0024] [2] Based on the optical communication module substrate described in [1] above,

[0025] The portion of the metal reinforcing layer surrounded by the frame-shaped removal portion is connected to the connection terminal of the electrical wiring Y.

[0026] [3] Based on the optical communication module substrate described in [1] or [2] above,

[0027] The portion of the metal reinforcing layer that sandwiches the insulating layer and is opposite to the electrical wiring Y is removed in a strip shape along the electrical wiring Y.

[0028] [4] Based on the optical communication module substrate described in any one of [1] to [3] above,

[0029] The connection terminals of the wiring substrate and the connection terminals of the optoelectronic hybrid substrate are arranged in an overlapping manner, and the overlapping connection terminals are directly connected to each other or electrically connected by means of conductive components.

[0030] [5] Based on the optical communication module substrate described in any one of [1] to [3] above,

[0031] The connection terminals of the wiring substrate and the connection terminals of the optoelectronic hybrid substrate are electrically connected by an electrical connector disposed between the wiring substrate and the optoelectronic hybrid substrate.

[0032] In other words, the inventors conducted repeated and in-depth research in order to solve the above-mentioned problems, and as a result, they discovered the following: If a frame-shaped removal portion is formed for each terminal in the portion of the metal reinforcing layer of the optoelectronic hybrid substrate constituting the optical communication module substrate that is opposite to the terminal for connection of the electrical wiring Y, then the terminal portion can ensure mechanical strength by utilizing the portion of the metal reinforcing layer remaining in the frame. Moreover, the area around the portion opposite to the terminal is disconnected from the large area of ​​the metal reinforcing layer, thereby suppressing the influence on electrical characteristics.

[0033] The effects of the invention

[0034] The optical communication module substrate according to the present invention provides an optical communication module substrate that exhibits excellent electrical characteristics, ensuring sufficient connection strength at the connection point P between the wiring substrate and the optoelectronic hybrid substrate without causing impedance reduction. Furthermore, its performance adequately accommodates the increasing frequency of signals and the finer spacing of wiring, thus providing an optical communication module for high-speed signal transmission with excellent reliability. Attached Figure Description

[0035] Figure 1 This is an explanatory diagram schematically showing a longitudinal section of the main part of the optical communication module substrate, which is an embodiment of the present invention.

[0036] Figure 2This is an explanatory diagram showing a plan view of the metal reinforcement layer as seen from the side of the optoelectronic hybrid substrate on which the aforementioned optical communication module substrate is formed.

[0037] Figure 3 (a) is a partial plan view of the main part of the metal reinforcement layer as seen from the side of the optoelectronic hybrid substrate where the circuit section is formed. Figure 3 (b) is a partial plan view showing a modified example of the connection terminal portion in the circuit section described above.

[0038] Figure 4 This is an explanatory diagram of the manufacturing process of the aforementioned optoelectronic hybrid substrate.

[0039] Figure 5 This is an explanatory diagram of the manufacturing process of the aforementioned optoelectronic hybrid substrate.

[0040] Figure 6 This is an explanatory diagram of the manufacturing process of the aforementioned optoelectronic hybrid substrate.

[0041] Figure 7 This is an explanatory diagram of the manufacturing process of the aforementioned optoelectronic hybrid substrate.

[0042] Figure 8 This is an explanatory diagram showing a plan view of a deformed example of the metal reinforcing layer as observed from the side of the aforementioned optoelectronic hybrid substrate where the metal reinforcing layer is formed.

[0043] Figure 9 This is an explanatory diagram illustrating a longitudinal cross-section of the main part of another embodiment of the optical communication module substrate of the present invention.

[0044] Figure 10 (a) is an explanatory diagram showing the samples used in the first verification test for evaluating the electrical characteristics of the embodiments and comparative examples of the present invention. Figure 10 (b) is an explanatory diagram showing the structure of the end of Example Sample 1 in the above-described samples. Figure 10 (c) is an explanatory diagram showing the structure of the end of Comparative Example 1 in the above samples.

[0045] Figure 11 (a) is a characteristic curve representing the differential impedance characteristics of Sample 1 in the above embodiment and Sample 1 in the comparative example. Figure 11 (b) is a characteristic curve representing the insertion loss in the high-frequency region of both samples.

[0046] Figure 12 This is an explanatory diagram of the evaluation method used in the second verification test to evaluate the electrical characteristics of the embodiments and comparative examples of the present invention.

[0047] Figure 13This is a schematic and partial illustration of an example of a typical optical communication module.

[0048] Figure 14 This is a schematic diagram used to illustrate the subject matter of the aforementioned optical communication module.

[0049] Figure 15 of (a), Figure 15 (b) are explanatory diagrams illustrating the shape of the metal reinforcement layer in the aforementioned optical communication module.

[0050] Figure 16 of (a), Figure 16 (b) are explanatory diagrams illustrating the shape of the metal reinforcement layer in the aforementioned optical communication module. Detailed Implementation

[0051] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following forms.

[0052] Figure 1 This is a partial longitudinal sectional view (cut along the direction of the optical waveguide extension) schematically illustrating one embodiment of the optical communication module substrate of the present invention.

[0053] The optical communication module substrate is similar to the aforementioned... Figure 13 The substrate used in the typical optical communication module shown is also an integral part of the wiring substrate 20 and the optoelectronic hybrid substrate 30, which are electrically connected.

[0054] The aforementioned wiring substrate 20 is a wiring substrate for differential signal transmission. Multiple electrical wires X, consisting of pairs of wires used for transmitting differential signals, are formed on the surface of the insulating layer 21. Furthermore, each wire of the aforementioned electrical wire X has a connection terminal 22 at its end for electrical connection to an electrical wire Y on the optoelectronic hybrid substrate 30 side. With each terminal 22 exposed, the remaining portion is covered by a cover layer 23.

[0055] Furthermore, various wiring patterns, pads, etc., for mounting or connecting appropriate electronic or electrical components can be provided on the wiring substrate 20 according to its intended use. The wiring substrate 20 can be either rigid or flexible; generally, considering the connection strength with the optoelectronic hybrid substrate 30, a rigid form is preferred.

[0056] On the other hand, the optoelectronic hybrid substrate 30 connected to the wiring substrate 20 is also an optoelectronic hybrid substrate for differential signal transmission, and its basic structure is the same as that of a general optoelectronic hybrid substrate. That is, a generally strip-shaped insulating layer 31 is used as a substrate, and a circuit section E is provided on one side (first side). The circuit section E includes electrical wiring Y formed by arranging multiple pairs of electrical wiring for transmitting differential signals, pads 34 for mounting optical elements 32, driving ICs 33 of the optical elements 32, etc. Furthermore, the leading end of each wiring of the electrical wiring Y becomes a connection terminal 35 for electrical connection with the connection terminal 22 of the wiring substrate 20. Except for these terminal portions, the parts that need insulation protection are covered by a cover layer 36. In addition, the optical elements 32 and driving ICs 33 are sometimes not installed in the optoelectronic hybrid substrate stage, and are indicated by a single-dot dashed line.

[0057] Furthermore, on the other side (second side) of the aforementioned insulating layer 31, that is, the side opposite to the side where the circuit section E is located, a metal reinforcing layer 37 is provided locally in the area requiring reinforcement to strengthen the insulating layer 31. Similarly, on the other side of the aforementioned insulating layer 31, a lower cladding layer 40, a core 41, and an upper cladding layer 42 are sequentially stacked in a configuration that partially overlaps with the metal reinforcing layer 37, and the optical waveguide W is formed by these three layers. In addition, a portion of the aforementioned optical waveguide W is cut into an inclined surface, which serves as a light reflector 43 for changing the direction of travel of the optical signal transmitted via the core 41 by 90 degrees.

[0058] like Figure 2 As shown, the metal reinforcing layer 37, which is disposed on the other side of the insulating layer 31, has through holes 50 for optical coupling, as is the case previously. Furthermore, at the portion that sandwiches the insulating layer 31 and faces the connection terminal 35 of the electrical wiring Y disposed on the opposite side, a frame-shaped removal portion 60 is formed by removing the metal reinforcing layer 37 in a frame-like manner to surround each connection terminal 35. This is the most significant feature of the present invention.

[0059] If we observe and magnify the portion of the metal reinforcing layer 37 containing the frame-shaped removal portion 60 from the side opposite to the insulating layer 31, where the circuit portion E is formed, then as... Figure 3 As shown in (a), each of the connecting terminals 35 is individually surrounded by the aforementioned frame-shaped removal portion 60.

[0060] Furthermore, the portion of the metal reinforcing layer 37 with the aforementioned frame-shaped removal portion 60 becomes a small, independent piece relative to its surroundings. Therefore, to prevent this portion from becoming electrically independent of the surrounding metal, a through hole 31a is pre-formed in the portion of the insulating layer 31 where the connecting terminal 35 is formed. During the formation of the electrical wiring, conductive material for electrical wiring is filled into this through hole 31a, making the connecting terminal 35 conductive and fixed to the aforementioned small piece portion of the metal reinforcing layer 37. This prevents electrostatic capacitance between the small piece portion and the connecting terminal 35. Additionally, the small piece portion will not peel off from the insulating layer 31, and sufficient mechanical strength can be ensured in this portion.

[0061] The aforementioned through hole 31a can also be a hole of any shape in its top view. If it is, for example, circular, its diameter is preferably 5 μm to 200 μm, and more preferably 5 μm to 100 μm. Furthermore, if the top view shape is, for example, square, one side of the square is preferably 5 μm to 200 μm, and more preferably 5 μm to 100 μm. And, as... Figure 3 As shown in (a), the aforementioned through hole 31a is not only provided in each of the connecting terminals 35, for example, as Figure 3 As shown in (b), two terminals can be provided at each end of each connecting terminal 35. Of course, more than three terminals can also be provided.

[0062] However, when the through hole 31a is provided, the manufacturing process has the following problem: the surface of the connecting terminal 35 where the through hole 31a is formed is recessed relative to the rest, and this recessed portion can easily lead to poor connection when connecting between substrates. Therefore, when the through hole 31a is formed, if the area of ​​the recessed portion of the connecting terminal 35 is set as S1 and the area of ​​the flat portion that is not recessed is set as S, it is desirable to consider the size and arrangement of the through hole 31a such that (S) / (S1) is 1 or more, more preferably 3 or more, and especially more preferably 7 or more (for S and S1, refer to...). Figure 3 (a) Of course, by considering the manufacturing conditions, if the through hole 31a can be formed in a way that does not produce such a pit, then the entire area of ​​the connecting terminal 35 will help the substrate connection, and therefore, it is the most preferred.

[0063] <Forming process of optoelectronic hybrid substrate>

[0064] Next, specific materials will be shown, and an example of the process for obtaining the aforementioned optoelectronic hybrid substrate 30 will be briefly described.

[0065] (1) Formation of the circuit section E

[0066] First, such as Figure 4As shown, a metal plate 100, which is prepared as a metal reinforcing layer 37, is coated with a photosensitive insulating resin such as polyimide to form an insulating resin layer 101 as an insulating layer 31.

[0067] Materials for the aforementioned metal plate 100 include stainless steel, copper, silver, aluminum, nickel, chromium, titanium, platinum, and gold, but stainless steel is preferred from the perspectives of strength and flexibility. Furthermore, the thickness of the aforementioned metal reinforcing layer 37 is preferably set in the range of 10 μm to 70 μm (more preferably 10 μm to 30 μm).

[0068] Furthermore, an insulating layer 31 is formed by performing photolithography (exposure, pre-baking, development, and curing) on ​​the aforementioned insulating resin layer 101. This insulating layer 31 has a predetermined pattern shape including through holes 31a for conducting between the individual small pieces of the metal reinforcing layer 37. The thickness of the aforementioned insulating layer 31 is preferably set in the range of 3 μm to 50 μm (more preferably 3 μm to 25 μm) (not shown).

[0069] Next, a conductive layer made of a conductive material such as copper is formed on the insulating layer 31 using methods such as sputtering or electroless plating. Then, conductive patterns such as electrical wiring Y, various pads 34, and connection terminals 35 are formed through necessary processes such as dry film resist lamination, exposure, and development. Then, as... Figure 5 As shown, a photosensitive insulating resin such as polyimide is applied over the conductive pattern, and a cover layer 36 is formed in the area requiring insulation protection in the same manner as the formation of the insulating layer 31.

[0070] Furthermore, in addition to copper, metals with excellent conductivity and ductility, such as chromium, aluminum, gold, and tantalum, are preferably used as the conductive material. Alloys employing at least one of these metals are also preferred. The thickness of the conductive pattern of the electrical wiring Y is preferably set in the range of 3 μm to 30 μm (more preferably 3 μm to 18 μm). Furthermore, considering the insulation, protection, and reinforcement of the electrical wiring Y, the thickness of the cover layer 36 formed thereon is preferably set in the range of 1 μm to 50 μm (more preferably 1 μm to 25 μm).

[0071] Furthermore, by forming Ni, Au, or other electroplated layers on the portions exposed from the aforementioned cover layer 36 that become various solder pads 34 and connection terminals 35, it is possible to obtain the circuit section E (see reference). Figure 5 ).

[0072] (2) Pattern formation of the metal reinforcement layer

[0073] Next, the metal reinforcing layer 37, which sandwiches the insulating layer 31 and is opposite to the circuit section E, is etched (dry film resist lamination, exposure, development, etching, dry film resist stripping, etc.) to remove unwanted portions and form a predetermined pattern shape. Thus, as... Figure 6 As shown, it is formed with optical element 32 (reference). Figure 1 The through hole 50 for optical coupling between the terminals, and the frame-shaped removal part 60 at the part opposite to the connecting terminal 35, etc.

[0074] (3) Formation of optical waveguide W

[0075] Next, the insulating layer 31, which includes the circuit section E and the metal reinforcement layer 37, is inverted so that the metal reinforcement layer 37 faces upward. Then, using a known method, the lower cladding layer 40, the core 41, and the upper cladding layer 42 are stacked and formed on the side of the insulating layer 31 where the metal reinforcement layer 37 is formed, with each layer patterned into a predetermined pattern as needed, thereby obtaining the optical waveguide W.

[0076] And, as Figure 7 As shown, the optical element 32 (refer to) disposed on the circuit section E side of the aforementioned insulating layer 31 is envisioned. Figure 1 The optical coupling between the core 41 and the optical waveguide W is achieved by using cutting, laser processing, or machining to form a predetermined portion of the optical waveguide W into an inclined surface at a 45° angle relative to the length direction of the core 41, thus creating a light-reflecting surface 43. This allows for the acquisition of an optoelectronic hybrid substrate 30 used in optical communication module substrates. Furthermore, the front end side (not shown), opposite to the side opposite the circuit section E, of the optical waveguide W can be either a structure with an optical connector mounted for connection to other optical wiring components, or a structure in which the same circuit section E' is formed on the front end side while sandwiching the optical waveguide W.

[0077] <Forming process of optical communication module substrate>

[0078] like Figure 1 As shown, the optoelectronic hybrid substrate 30 and the wiring substrate 20 are configured such that their connection terminals 35 and 22 overlap, and their joints are electrically connected using solder bumps or the like. Then, the wiring substrate 20 and the optoelectronic hybrid substrate 30 are stably assembled. Thus, the desired optical communication module substrate can be obtained.

[0079] According to the aforementioned optical communication module substrate, a frame-shaped removal portion 60 corresponding to each connection terminal 35 is individually formed on the metal reinforcing layer 37 of the optoelectronic hybrid substrate 30. Therefore, the mechanical strength of each terminal portion is ensured by the small piece portion of the metal reinforcing layer 37 remaining within the frame of the frame-shaped removal portion 60. Furthermore, the small piece portion opposite to each connection terminal 35 is insulated from the surrounding area of ​​the large-area metal reinforcing layer and is conductive to each connection terminal 35, thus significantly suppressing the impact on electrical characteristics.

[0080] Therefore, the optical communication module substrate of the present invention is an optical communication module substrate as follows: at the connection point P between the wiring substrate 20 and the optoelectronic hybrid substrate 30 (refer to...) Figure 14 At this location, the connection strength and electrical characteristics are excellent, fully capable of handling the high frequency of signals and the finer spacing of wiring. Furthermore, by using the optical communication module substrate of the present invention, an optical communication module for high-speed signal transmission with excellent reliability can be provided.

[0081] Furthermore, in the examples above, such as Figure 2 As shown, the removal portion of the metal reinforcing layer 37 is separated from the normally provided through hole 50, and only a frame-shaped removal portion 60 surrounding each connecting terminal 35 is provided. However, for example, as... Figure 8 As shown, in order to improve the insertion loss of the differential signal wiring section at high frequencies, a strip-shaped removal section 61 extending along the wiring can also be formed together with the frame-shaped removal section 60 for the portion opposite to the wiring Y (not shown).

[0082] In addition, in the example above, a through hole 31a is provided in the insulating layer 31 in advance to make the small piece portion integrated with the connecting terminal 35 and conductive, so as to avoid electrostatic capacitance between the independent small piece portion inside the metal reinforcing layer 37 surrounded by the frame-shaped removal portion 60 and the connecting terminal 35. However, depending on the situation, such a conductive structure may not be necessary.

[0083] Furthermore, in the above example, during the formation of the optical communication module substrate, the connection terminals 22 of the wiring substrate 20 and the connection terminals 35 of the optoelectronic hybrid substrate 30 are arranged to overlap each other, and the joints of the connection terminals 22 and 35 are electrically connected using solder bumps (see reference). Figure 1 The electrical connection of the aforementioned connecting terminals 22 and 35 is not limited to solder bumps; other metal bumps such as gold bumps can also be used. Furthermore, it can be achieved by introducing a conductive film such as an anisotropic conductive film (ACF). In other words, the type of conductive member used to electrically connect the overlapping connecting terminals 22 and 35 is not particularly limited. Additionally, the aforementioned structure of the connecting terminals 22 and 35 can be used to directly join them.

[0084] Furthermore, to enable the electrical connection of the aforementioned terminals 22 and 35, electrical connectors can also be used, not limited to such conductive components. For example, such as... Figure 9 As shown, an electrical connector (such as a ZIF connector) 70 is installed at one end of the optoelectronic hybrid substrate 30 where the connection terminals 35 are arranged, such that the connection terminal 71 of the electrical connector 70 is located between the connection terminal 35 on the optoelectronic hybrid substrate 30 side and the connection terminal 22 on the wiring substrate 20 side, thereby enabling the two to be electrically connected.

[0085] Thus, the optical communication module substrate in which the electrical connector 70 is installed also has a frame-shaped removal portion 60 provided in the metal reinforcing layer 37, thereby enabling the acquisition of a... Figure 1 The optical communication module substrate shown also exhibits excellent performance.

[0086] Furthermore, based on the structure of the electrical connector 70, the arrangement of the optoelectronic hybrid substrate 30 can be reversed so that the side of the optoelectronic hybrid substrate 30 with the metal reinforcing layer 37 faces the wiring substrate 20, enabling electrical connection between the two. Specifically, the first connection terminal of the electrical connector 70 is connected to the connection terminal 35 on the optoelectronic hybrid substrate 30 side, and the second connection terminal of the electrical connector 70 is connected to the connection terminal 22 on the wiring substrate 20 side, thereby enabling electrical connection (illustration omitted). In this case, a frame-shaped removal portion 60 is also provided in the metal reinforcing layer 37, thereby enabling the connection with… Figure 1 The optical communication module substrate shown exhibits excellent performance.

[0087] Furthermore, it is natural that due to the structure 70 of the electrical connector used, the arrangement of the connection terminals 35 on the optoelectronic hybrid substrate 30 side, and the arrangement of the connection terminals 22 on the wiring substrate 20 side, the terminals may not overlap vertically or may be misaligned. However, in such cases, a frame-shaped removal portion 60 is provided on the metal reinforcing layer 37 of the optoelectronic hybrid substrate 30, thereby enabling the acquisition of a connection with the desired electrical interface. Figure 1 The excellent performance of the optoelectronic hybrid substrate shown is equally excellent.

[0088] Furthermore, the above examples illustrate the application of the present invention to optical communication module substrates for differential signal transmission. The optical communication module substrate does not necessarily need to be a substrate for differential signal transmission; for example, it could also be a substrate for single-ended transmission. However, as described above, the advantages of the present invention can be flexibly utilized in high-speed signal transmission applications, such as differential signal transmission, in applications requiring higher frequency signal transmission and fine-pitch wiring. Therefore, it is preferably used for high-speed signal transmission applications such as differential signal transmission.

[0089] Next, embodiments will be described together with comparative examples. However, the present invention is not limited to the following embodiments.

[0090] Example

[0091] The following two experiments were conducted to verify the difference in the effect on electrical characteristics when a frame-shaped removal portion is formed on the portion of the metal reinforcing layer in the optoelectronic hybrid substrate constituting the optical communication module substrate that is opposite to the connection terminal on the circuit side, and when the frame-shaped removal portion is not formed.

[0092] <Verification Experiment 1>

[0093] First, it was made Figure 10 As shown in (a), there is a strip-shaped wiring substrate with a width of 10 mm and a length of 60 mm. The substrate has an insulating layer 120 sandwiched between two pairs of electrical wires Y1 for differential transmission formed on the back side and a metal reinforcing layer 121 formed on the back side. The electrical wires Y1 are provided with connection terminals 122 at both ends.

[0094] The materials and thicknesses of each layer of the aforementioned wiring substrate are as follows.

[0095] Insulation layer 120: Polyimide, 10μm thick

[0096] Metal reinforcement layer 121: Stainless steel, 20μm thick

[0097] Electrical wiring Y1: Copper, 6μm thick (connector terminal 122 is gold-plated)

[0098] [Example Sample 1]

[0099] Furthermore, in the aforementioned wiring substrate, such as Figure 10 As shown in (b), in the portion of the metal reinforcing layer 121 opposite to the aforementioned connecting terminal 122, a frame-shaped removal portion 123 is formed to individually surround each terminal 122, and a strip-shaped removal portion 124 is formed along the electrical wiring Y1, thus providing the embodiment sample 1. Furthermore, through holes are pre-formed in the insulating layer 120 at positions corresponding to the aforementioned connecting terminal 122, allowing copper, the forming material of the electrical wiring Y1, to fill these through holes to conduct the small, independent portions of the metal reinforcing layer 121 due to the frame-shaped removal portion 123 (see reference). Figure 3 ).

[0100] [Comparative Sample 1]

[0101] In addition, such as Figure 10 As shown in (c), the metal reinforcement layer 121 of the above-mentioned wiring substrate does not form a frame-shaped removal portion 123 as in the above-described embodiment sample, but only forms a strip-shaped removal portion 124 along the electrical wiring Y1, thus being designated as comparative example sample 1.

[0102] Furthermore, the electrical characteristics of both Example Sample 1 and Comparative Sample 1 were evaluated by performing the following two measurements. The measurement results are presented below. Figure 11 of (a), Figure 11 In (b).

[0103] [Evaluation of impedance matching at the connection]

[0104] The differential impedance (Ω) of each sample was measured using time-domain reflectometry (TDR) with a device consisting of a sampling oscilloscope DSA8200 and a TDR module 80E04 (manufactured by Tektronix Company).

[0105] The aforementioned TDR method involves inputting a pulse wave with a high rise time into the sample and measuring the impedance by utilizing the reflection phenomenon generated at the impedance mismatch. This allows for the evaluation of impedance matching in the connection.

[0106] [Evaluation of high-frequency signal quality based on insertion loss (Sdd21) measurement]

[0107] The insertion loss (Sdd21) of each sample with differential signal input was measured using a four-port vector network analyzer N5232A (manufactured by Keysight Technologies Japan K.K.).

[0108] The insertion loss described above is a value expressed in dB as the ratio of the transmitted signal energy to the input signal energy fed to the sample. This allows for the evaluation of high-frequency signal quality.

[0109] Based on the above results, it can be concluded that Example Sample 1 has significantly superior electrical properties compared to Comparative Example 1. That is, as... Figure 11 As shown in (a), in Comparative Example 1, the impedance decreases in its connection terminal portion, becoming a large impedance discontinuity point, while in Example 1, no such discontinuity point occurs.

[0110] In addition, such as Figure 11 As shown in (b), it can be seen that in the frequency range exceeding 1 GHz, compared with Comparative Example 1, Example 1 did not suffer from the degradation of insertion loss due to impedance discontinuity in the connection terminal portion, thus suppressing the reduction in signal quality.

[0111] Furthermore, it is believed that: in the portion of the sample 1 of the embodiment that is opposite to the terminal 122, there are also independent small pieces of the metal reinforcing layer 121 remaining, so it has mechanical strength that is not inferior to that in the case where the metal reinforcing layer 121 is not removed.

[0112] Therefore, it can be seen that when the structure of the above-described embodiment sample 1 is applied to the optical communication module substrate of the present invention, an optical communication module substrate with excellent quality, possessing both excellent electrical characteristics and mechanical strength, is obtained.

[0113] <Verification Experiment 2>

[0114] [Example Sample 2]

[0115] According to the aforementioned record, it was made Figure 9 The optical communication module substrate shown is an example sample 2. The structure of each layer follows the general structure of an optical communication module substrate, and detailed descriptions are omitted. Furthermore, in this example sample 2, the high-speed differential signal connection terminals 35 on the optoelectronic hybrid substrate 30 side are arranged in a row of eight, forming eight frame-shaped removal portions 60 (see reference). Figure 2 Furthermore, a ZIF connector (FH43B-21S-0.2SHW, manufactured by Hirose Electric Co., Ltd.) is used as the electrical connector 70 for connecting the aforementioned connection terminal 35 to the connection terminal 22 on the wiring board 20 side.

[0116] [Comparative Sample 2]

[0117] Except that the frame-shaped removal portion 60 described above is not formed, the optical communication module substrate (comparative example sample 2) was fabricated in the same manner as in Example Sample 2.

[0118] Furthermore, using a pulse waveform generator M8045A (manufactured by Keysight Technologies Japan KK), digital signals of 6Gbps, 8Gbps, and 10Gbps were input from the optoelectronic hybrid substrate 30 side of each sample (optical communication module substrate). The output signal waveforms taken from the wiring substrate 20 side were observed using a sampling oscilloscope N1000A and a module 54754A (both manufactured by Keysight Technologies Japan KK). In addition, for each sample, the observed 3000 signal waveforms were superimposed to obtain eye diagrams. In each eye diagram, the value with the largest voltage width at the eye opening was set as the "eye height" (in...). Figure 12 The eye height H of the samples was compared (denoted by H). A higher eye height H indicates better signal transmission quality. The results are as follows.

[0119] [Table 1]

[0120]

[0121] Based on the above results, it can be seen that: compared with comparative sample 2, example sample 2 suppressed the degradation of the transmission signal quality and has excellent optical communication performance.

[0122] Furthermore, while the above embodiments illustrate specific aspects of the invention, these embodiments are merely illustrative and not intended to be limiting. It is intended that various modifications, readily apparent to those skilled in the art, are all within the scope of this invention.

[0123] Industrial availability

[0124] The optical communication module substrate of the present invention fully ensures the connection strength at the connection point P between the wiring substrate and the optoelectronic hybrid substrate, and has excellent electrical characteristics that can cope with high-speed signal transmission, and can be widely used in high-speed signal transmission technologies such as differential signal transmission.

[0125] Explanation of reference numerals in the attached figures

[0126] 30. Optoelectronic hybrid substrate; 31. Insulating layer; 35. Connecting terminal; 37. Metal reinforcing layer; 60. Frame-shaped removal section.

Claims

1. An optical communication module substrate, which is an optical communication module substrate formed by connecting a wiring substrate and an optoelectronic hybrid substrate, wherein, The wiring substrate includes electrical wiring X and terminals for connection. The optoelectronic hybrid substrate includes: an insulating layer; a circuit section disposed on a first surface of the insulating layer, having pads for mounting optical elements, electrical wiring Y, and terminals for connection; a metal reinforcing layer disposed on a second surface of the insulating layer; and an optical waveguide, which is also disposed on the second surface of the insulating layer with a portion overlapping the metal reinforcing layer. The connection terminals of the wiring substrate and the connection terminals of the optoelectronic hybrid substrate form electrical connection points. The metal reinforcing layer of the optoelectronic hybrid substrate is removed in a frame-shaped removal portion at the part that sandwiches the insulating layer and faces the connection terminal of the electrical wiring Y provided on the opposite side, in a manner that surrounds the terminal. The inner side of the frame-shaped removal portion becomes a small piece that is independent of the surrounding area.

2. The optical communication module substrate according to claim 1, wherein, The portion of the metal reinforcing layer surrounded by the frame-shaped removal portion is connected to the connection terminal of the electrical wiring Y.

3. The optical communication module substrate according to claim 1 or 2, wherein, The portion of the metal reinforcing layer that sandwiches the insulating layer and is opposite to the electrical wiring Y is removed in a strip shape along the electrical wiring Y.

4. The optical communication module substrate according to claim 1 or 2, wherein, The connection terminals of the wiring substrate and the connection terminals of the optoelectronic hybrid substrate are arranged in an overlapping manner, and the overlapping connection terminals are directly connected to each other or electrically connected by means of conductive components.

5. The optical communication module substrate according to claim 1 or 2, wherein, The connection terminals of the wiring substrate and the connection terminals of the optoelectronic hybrid substrate are electrically connected by an electrical connector disposed between the wiring substrate and the optoelectronic hybrid substrate.

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