BGA high-frequency module, substrate for BGA high-frequency module, and optical communication module

Abstract

Provided are a BGA high frequency module, a substrate for a BGA high frequency module, and an optical communication module that includes at least one of the above, with which it is possible to achieve size reduction of an optical communication module without a decrease in the impedance between a pad and a solder ball. The BGA high frequency module according to the present disclosure is provided with: a differential signal pair including a first signal pad and a second signal pad; a first ground pad that is disposed adjacent to the first signal pad; a second ground pad disposed adjacent to the second signal pad; at least one third ground pad disposed in a position more spaced apart from the first signal pad than the distance between the first signal pad and the first ground pad; and at least one fourth ground pad that is disposed in a position that is more spaced apart from the second signal pad than the distance between the second signal pad and the second ground pad.

Description

Technical Field

[0001] The present disclosure relates to a BGA high-frequency module, a substrate for a BGA high-frequency module, and an optical communication module including them.

Background Art

[0002] In recent years, in the optical communication industry, the practical application of small optical transceivers capable of increasing the transmission speed per module footprint has been progressing. As an example, it has already been reported that a small optical transceiver of about 18.35 mm × 58.26 mm × 8.5 mm can be realized in the form factor of a transceiver for optical communication called Quad Small Form-factor Pluggable Double Density (hereinafter referred to as QSFP-DD). In such a small optical transceiver, the application of a high-frequency module including a ball grid array (hereinafter referred to as BGA), which has been conventionally used for ICs and the like, to the optical communication module to be mounted is progressing. In addition, the technology of mounting this BGA high-frequency module on a printed circuit board (hereinafter referred to as PCB) has also been progressing (see, for example, Non-Patent Document 1). In recent years, since the need for further miniaturization of optical transceivers has been increasing, the demand for further miniaturization has been strengthening for optical communication modules in which a BGA high-frequency module is mounted on a PCB.

[0003] Figure 1 illustrates the structure of a conventional BGA high-frequency module 10. Figure 1(a) is a plan view from the back surface (the surface facing the PCB 20 in Figure 3, which will be described later), and Figure 1(b) is a cross-sectional view at the position of the Ib-Ib cross-sectional line. As shown in Figure 1, the conventional BGA high-frequency module 10 includes a module member 11 and a plurality of pads 12 arranged at equal intervals in the longitudinal direction (X direction in Figure 1) and the width direction (Y direction in Figure 1) on the back surface of the module member 11. Here, as an example, the pads 12 are shown in a 7x4 configuration with 7 pads in the X direction and 4 pads in the Y direction. Furthermore, the module member 11 may be made of resin or ceramics, and the pads 12 may be made of aluminum or copper.

[0004] Figure 2 illustrates the structure of a PCB 20 for mounting a conventional BGA high-frequency module 10. Figure 2(a) shows a plan view from the top (the side facing the BGA high-frequency module 10 in Figure 3, which will be described later), and Figure 2(b) shows a cross-sectional view at the position of the IIb-IIb cross-sectional line. As shown in Figure 2, the PCB 20 includes a laminated substrate 21 in which multiple dielectric parts 211a-c and multiple ground planes 212a-c are stacked, multiple pads 22 arranged at equal intervals in the longitudinal direction (X direction in Figure 2) and the width direction (Y direction in Figure 2) on the upper surface of the laminated substrate 21, and through-hole vias 23a-c that electrically connect some of the multiple pads 22 to the ground planes 212a-c. Similar to Figure 1, here as an example, the pads 22 are shown in a 7x4 configuration with 7 pads in the X direction and 4 pads in the Y direction. Some of the pads 22 connected to the ground planes 212a-c function as ground pads to stabilize signals. In Figure 2, these ground pads are connected to the ground plane 212c via through-hole vias 23a-c. As shown in Figure 2(a), other pads, such as signal terminals, are connected to external circuits via surface wiring 24 formed on the top surface of the PCB 20, or to and routed to inner layer wiring formed on lower layers of the substrate via through-hole vias.

[0005] By mounting the aforementioned BGA high-frequency module 10 on the PCB 20, an optical communication module 30 for mounting on a small optical transceiver is manufactured.

[0006] Figure 3 illustrates the structure of an optical communication module 30 in which a BGA high-frequency module 10 is mounted on a PCB 20. Figure 3(a) is a plan view with the BGA high-frequency module 10 on the top, and Figure 3(b) is a cross-sectional view at the position of the IIIb-IIIb cross-section line. As shown in Figure 3, the optical communication module 30 has the BGA high-frequency module 10 mounted on the PCB 20, and the two are electrically connected via solder balls 31 placed between pads 12 and 22. Typically, the optical communication module 30 can be manufactured by forming solder balls 31 on the pads 12 of the BGA high-frequency module 10 and reflowing it while it is placed on the PCB 20.

[0007] When the optical communication module 30 is applied to a transceiver for optical communication, the pads 12 of the BGA high-frequency module serve as various terminals. In addition to the ground pad mentioned above, the terminals may include DC terminals for supplying power, analog or digital control terminals, and signal terminals for inputting and outputting electrical signals. The number of DC terminals varies greatly depending on the module, but for optical communication modules for coherent optical communication, a total of eight differential signal pairs (four pairs for transmission and four for reception) are often used. Furthermore, since the signal terminals of the optical communication module input and output signals to a signal processing processor adjacent to the optical communication module or to a host device that constitutes the optical communication system, they are usually gathered at one end of the module.

[0008] One way to miniaturize such optical communication modules is to narrow the spacing between the pads 12, 22 and solder balls 31, thereby arranging the terminals more densely (increasing terminal density). However, increasing terminal density leads to an increase in capacitance between solder balls 31, which in turn increases capacitance between terminals such as ground pads and signal terminals. If the capacitance between adjacent signal terminals (differential signal pairs) or between signal terminals and ground pad terminals increases, the impedance decreases, making impedance matching impossible. As a result, high-frequency transmission characteristics (lower cutoff frequency) and high-frequency reflection characteristics deteriorate. Thus, when miniaturizing optical communication modules that mount BGA high-frequency modules on a PCB, increasing terminal density can lead to a decrease in signal quality.

[0009] To address these challenges, a conventional technique for suppressing the increase in capacitance between terminals is to reduce the size of the pads 12, 22 and the solder balls 31. However, as mentioned above, the pads 12 and 22 need to be connected to the ground plane 212c via through-hole vias 23a-c and lead wires, making it difficult to reduce the size of the pads 12, 22 and the solder balls 31 beyond a certain point. Furthermore, reducing the size of the pads 12, 22 and the solder balls 31 can lead to another problem: difficulty in mounting.

[0010] As an example, let's consider the size of the pads 12, 22 and solder balls 31 when implementing an optical communication module 30 using a small form factor QSFP-DD with dimensions of approximately 18.35 mm × 58.26 mm × 8.5 mm, as described above. When mounting the PCB 20 in an enclosure with a width (length in the Y direction in Figures 1 and 2) of 18.35 mm, the width of the PCB 20 board must be smaller than the enclosure, so it will be approximately 14-16 mm.

[0011] On the other hand, focusing on the terminal arrangement, if differential signal pairs are arranged as GSSG (Ground-Signal-Signal-Ground), and adjacent ground pads are shared, then two differential signal pairs become 7 terminals in GSSGSSG, allowing differential signals to be placed in a smaller area. Assuming such an arrangement, if the optical communication module 30 is for coherent optical communication, there are 8 differential signal pairs, resulting in a total of 25 terminals. The spacing between each solder ball 31 is generally around 0.25-0.8 mm, but here we will use 0.5 mm as an example. In this case, gathering the signal terminals at one end requires a width of about 12 mm, which fits within the 14-16 mm width of the PCB 20 mentioned above. However, for BGA, standards are set by organizations such as JEITA (Japan Electronics and Information Technology Industries Association). If the spacing between each solder ball 31 is 0.5 mm, the pad diameter is fixed at a nominal value of about φ0.3 mm. Therefore, it can be said that there are practical limits to how much the pad can be miniaturized.

[0012] Furthermore, the size of the pads and solder balls is also limited by the package side of the optical communication module mounted on the BGA. For example, as in Non-Patent Document 1, when ceramic package material is used, a ceramic coating with a width of 70 μm is required to ensure the strength of the pads. As a result, the diameter of the pads becomes effectively φ0.44 mm, and the gap between adjacent pads becomes narrow to about 60 μm. Consequently, the capacitance increases and the impedance decreases, which can degrade the high-frequency transmission characteristics (decrease in cutoff frequency) and high-frequency reflection characteristics.

[0013] Based on the above, in optical communication modules (e.g., optical communication module 30) that mount BGA high-frequency modules on a PCB, which are effective in miniaturizing optical transceivers, further miniaturization by increasing the density of terminals is desired. However, a challenge has been raised as a degradation of signal quality due to impedance reduction caused by the high density of terminals. Conventional techniques for reducing the size of terminals (pads and solder balls) have limitations in terms of constraints imposed by standards, etc., and alternative methods are needed to address this challenge. [Prior art documents] [Non-patent literature]

[0014] [Non-Patent Document 1] S. Yamanaka, et al., “Silicon Photonics Coherent Optical Subassembly with EO and OE Bandwidths of Over 50 GHz” OFC 2020. (2020) [Overview of the project]

[0015] This disclosure has been made in view of the above-mentioned problems, and its purpose is to provide a BGA high-frequency module, a substrate for a BGA high-frequency module, and an optical communication module including at least one of the above, which enable miniaturization of an optical communication module without reducing the impedance between pads and solder balls.

[0016] To address the above-mentioned problems, this disclosure provides a BGA high-frequency module comprising: a module member; a differential signal pair disposed on the back surface of the module member and including a first signal pad and a second signal pad adjacent to the first signal pad; a first ground pad disposed adjacent to the first signal pad; a second ground pad disposed adjacent to the second signal pad; at least one third ground pad disposed at a distance from the first signal pad that is greater than a first distance between the first signal pad and the first ground pad, and a second distance between the second signal pad and the second ground pad; and at least one fourth ground pad disposed at a distance from the second signal pad that is greater than the first distance and the second distance. [Brief explanation of the drawing]

[0017] [Figure 1] This figure illustrates the structure of a conventional BGA high-frequency module 10. Figure 1(a) shows a plan view from the back side, and Figure 1(b) shows a cross-sectional view at the position of the Ib-Ib cross-sectional line. [Figure 2] This figure illustrates the structure of a PCB 20 for mounting a conventional BGA high-frequency module 10. Figure 2(a) shows a plan view from the top, and Figure 2(b) shows a cross-sectional view at the position of the IIb-IIb cross-sectional line. [Figure 3] This diagram illustrates the structure of an optical communication module 30 in which a BGA high-frequency module 10 is mounted on a PCB 20. Figure 3(a) is a plan view with the BGA high-frequency module 10 on the top, and Figure 3(b) is a cross-sectional view at the position of the IIIb-IIIb cross-section line. [Figure 4] Figure 4(a) is a plan view of the BGA high-frequency module 40 used in an optical communication module according to the first embodiment of the present disclosure, where Figure 4(a) is a plan view of the BGA high-frequency module 40 as seen from the back side, Figure 4(b) is a cross-sectional view at the position of the IVb-IVb cross-sectional line, and Figure 4(c) is a plan view of a modified example. [Figure 5]Figure 5(a) shows the structure of an optical communication module 50 in which a BGA high-frequency module 40 according to the first embodiment of the present disclosure is mounted on a PCB 51. Figure 5(a) is a plan view of the PCB 51 as seen from above, and Figure 5(b) is a cross-sectional view at the position of the Vb-Vb cross-section line. [Figure 6] Figure 6(a) shows the structure of a BGA high-frequency module 60 according to a second embodiment of the present disclosure, where Figure 6(a) is a plan view of the BGA high-frequency module 60 as seen from the back side, and Figure 6(b) is a cross-sectional view at the position of the VIb-VIb cross-sectional line. [Figure 7] Figure 7(a) shows the structure of a BGA high-frequency module 70 according to a second embodiment of the present disclosure, where Figure 7(a) is a plan view of the BGA high-frequency module 70 as seen from the back side, and Figure 7(b) is a cross-sectional view at the position of the VIIb-VIIb cross-sectional line. [Figure 8] Figure 8 shows the structure of PCB80 according to a fourth embodiment of the present disclosure, where Figure 8(a) is a plan view of PCB80 as seen from the top side, and Figure 8(b) is a cross-sectional view at the position of the VIIIb-VIIIb section line. [Modes for carrying out the invention]

[0018] Various embodiments of this disclosure are described below in detail with reference to the drawings. Identical or similar reference numerals indicate identical or similar elements, and redundant descriptions may be omitted. Materials and numerical values ​​are illustrative and are not intended to limit the technical scope of this disclosure. The following description is illustrative and some configurations may be omitted or modified, or implemented with additional configurations, without departing from the gist of one embodiment of this disclosure.

[0019] In the BGA high-frequency module in the present disclosure, unlike the prior art, it has a structure in which the distance between the ground pads adjacent to the signal pads is farther than the distance between the other ground pads. Also, in the PCB, it has a structure in which at least a part of one ground plane is excluded. Due to such a structure, the distance between the signal pads and the ground pads and the distance between the signal pads and the ground plane are farther than in the prior art, so it is possible to suppress a decrease in impedance.

[0020] (First Embodiment) FIG. 4 is a diagram showing the structure of a BGA high-frequency module 40 used in an optical communication module according to the first embodiment of the present disclosure. FIG. 4(a) is a plan view seen from the back side (the surface facing the PCB 50 in FIG. 5 described later) of the BGA high-frequency module 40, FIG. 4(b) is a cross-sectional view at the position of the IVb-IVb cross-section line, and FIG. 4(c) is a plan view of a modified example. As shown in FIG. 4, the BGA high-frequency module 40 according to the first embodiment of the present disclosure includes, on the back surface of the module member 41, a differential signal pair 42 including a first signal pad 421 and a second signal pad 422 adjacent to the first signal pad 421, a first ground pad 43 arranged adjacent to the first signal pad 421, a second ground pad 44 arranged adjacent to the second signal pad 422, at least one third ground pad 45a-d arranged at a position farther than the distance between the first signal pad 421 and the first ground pad 43 and the second distance between the second signal pad and the second ground pad, and a fourth ground pad 46a-d arranged at a position farther than the distance between the second signal pad 422 and the second ground pad 44.

[0021] When considering the distance between the signal pad and the ground pad, taking the first signal pad 421 as a reference, the distance between the first signal pad 421 and the first ground pad 43 is the shortest, and the distance between the first signal pad 421 and other ground pads (for example, the third ground pad 45) is always longer than the distance between the first signal pad 421 and the first ground pad 43. Similarly, when considering the second signal pad 422 as a reference, the distance between the second signal pad 422 and the second ground pad 44 is the shortest, and the distance between the second signal pad 422 and other ground pads (for example, the fourth ground pad 46) is always longer than the distance between the second signal pad 422 and the second ground pad 44. In FIG. 4, the third ground pads 45a-d and the fourth ground pads 46a-d are shown in a form where four are arranged, but there is no limitation on the number of arrangements as long as the above distance relationship is not violated.

[0022] Also, in FIG. 4(a), each signal pad and ground pad is shown in a form arranged in a square shape on the XY plane, but the arrangement method is not limited to this. For example, as shown in FIG. 4(c), each signal pad and ground pad may be arranged in a substantially circular shape or a substantially hexagonal (honeycomb) shape.

[0023] Furthermore, each signal pad and ground pad may further include a suppression of a ceramic coat (not shown) for strength reinforcement. The width of the ceramic coat is preferably about 70 μm, but is not limited thereto.

[0024] Figure 5 shows the structure of an optical communication module 50 in which a BGA high-frequency module 40 according to the first embodiment of this disclosure is mounted on a PCB 51. Figure 5(a) is a plan view of the PCB 51 as seen from above, and Figure 5(b) is a cross-sectional view at the position of the Vb-Vb cross-sectional line. As shown in Figure 5, the optical communication module 50 according to the first embodiment of this disclosure has a structure in which the above-mentioned BGA high-frequency module 40 is mounted on a PCB 51 via a plurality of solder balls 52. Here, the signal pads and ground pads installed on the PCB 51 side are arranged facing each other so that the signal pads and ground pads of the BGA high-frequency module 40 can be connected to each other via the solder balls 52. The PCB 51 also includes a laminated substrate in which a dielectric part and a ground plane are laminated, through-hole vias that electrically connect the ground plane and the ground pads, and surface wiring electrically connected to the signal pads, similar to a PCB 20 in the prior art. The signal pads may be connected to the inner layer wiring via through-hole vias.

[0025] In the BGA high-frequency module 40 and the optical communication module 50 including it, unlike conventional technology in which pads are arranged at equal intervals, the distance between the third ground pad 45 and the fourth ground pad 46 and the first signal pad 421 and the second signal pad 422 is greater than the distance between the first ground pad 43 and the second ground pad 44. As a result, the distance between the signal pads and ground pads is greater than in conventional designs, which suppresses impedance reduction and reduces signal quality degradation.

[0026] (Second embodiment) Figure 6 shows the structure of a BGA high-frequency module 60 according to a second embodiment of the present disclosure, where Figure 6(a) is a plan view of the BGA high-frequency module 60 as seen from the back side, and Figure 6(b) is a cross-sectional view at the position of the VIb-VIb cross-sectional line. As shown in Figure 6, the BGA high-frequency module 60 according to the second embodiment of the present disclosure has a structure in which multiple BGA high-frequency modules are connected by sharing at least a portion of the signal pads and ground pads in the BGA high-frequency module 40 described above. As an example, as shown in Figure 6, the BGA high-frequency module 60 further includes a differential signal pair 61 including a first signal pad 611 and a second signal pad 612, a fifth ground pad 62 adjacent to the second signal pad 612, a sixth ground pad 63 positioned such that the distance to the first signal pad 611 is greater than the distance between the first signal pad 611 and the second ground pad 44, and a sixth ground pad 64a-d positioned such that the distance to the second signal pad 622 is greater than the distance between the second signal pad 622 and the fifth ground pad 62. Here, the second ground pad 44 and the fourth ground pads 46b and 46d are shared as ground pads for the first signal pad 611. However, the shared signal pads and ground pads are not limited to these, and any ground pads or signal pads included in the BGA high-frequency module 60 may be shared as long as the GSSGSS... arrangement described above is maintained.

[0027] In addition, as with the first embodiment, the BGA high-frequency module 60 may have additional ground pads, provided that it does not deviate from the relationship between the signal pads and ground pads described above.

[0028] Furthermore, while Figure 6 shows each signal pad and ground pad arranged in a rectangular shape on the XY plane, the arrangement is not limited to this; for example, each signal pad and ground pad may be arranged on a roughly circular circumference.

[0029] In addition, each pad may further include a ceramic coating restraint (not shown) for strength reinforcement. The width of the ceramic coating is preferably about 70 μm, but is not limited to this.

[0030] In optical communication modules manufactured by mounting such BGA high-frequency modules 60 on a PCB, similar to the first embodiment, the distance between the signal pad and the ground pad is greater than in conventional optical communication modules, thus preventing impedance degradation and suppressing signal quality deterioration.

[0031] (Third embodiment) Figure 7 shows the structure of a BGA high-frequency module 70 according to a second embodiment of the present disclosure, where Figure 7(a) is a plan view of the BGA high-frequency module 70 as seen from the back side, and Figure 7(b) is a cross-sectional view at the position of the VIIb-VIIb section line. As shown in Figure 7, the BGA high-frequency module 70 according to a third embodiment of the present disclosure is a configuration in which the first signal pad 421 in the BGA high-frequency module 40 is replaced by a first signal pad 711, and the second signal pad 422 is replaced by a second signal pad 712. The first signal pad 711 and the second signal pad 712 differ from the first and second embodiments in that they have a shape in which at least a portion in the width direction is cut off. However, the distances between the signal pads and ground pads are arranged in the same way as in the first and second embodiments, such that the distance between the first signal pad 711 and the first ground pad 43, and the distance between the second signal pad 712 and the second ground pad 44 are the shortest.

[0032] In Figure 7, the BGA high-frequency module 70 is depicted as not being connected as described in the second embodiment, but it may be connected by sharing at least some of the signal pads and ground pads, similar to the second embodiment.

[0033] Furthermore, similar to the first embodiment, in the BGA high-frequency module 60, the arrangement is not limited to a rectangle, as long as it does not deviate from the above-mentioned distance. In addition, each pad may further include a ceramic coating restraint (not shown) for strength reinforcement.

[0034] Even in optical communication modules where such BGA high-frequency modules 70 are mounted on a PCB, it is possible to suppress the decrease in impedance between pads, similar to the first and second embodiments. Therefore, it has the effect of suppressing the degradation of signal quality compared to conventional technology.

[0035] (Fourth embodiment) Figure 8 shows the structure of PCB80 according to a fourth embodiment of the present disclosure, where Figure 8(a) is a plan view of PCB80 as seen from the top side, and Figure 8(b) is a cross-sectional view at the position of the VIIIb-VIIIb section line. As shown in Figure 8, the PCB 80 according to the fourth embodiment of the present disclosure includes, on the upper surface of the substrate, a differential signal pair including a first signal pad and a second signal pad adjacent to the first signal pad, connected to the above-described BGA high-frequency modules (e.g., BGA high-frequency modules 10, 40, 60, 70) via solder balls, a first ground pad positioned adjacent to the first signal pad, a second ground pad positioned adjacent to the second signal pad, at least one third ground pad positioned at a distance from the first signal pad greater than a first distance between the first signal pad and the first ground pad, and a second distance between the second signal pad and the second ground pad, and at least one fourth ground pad positioned at a distance greater than the first and second distances from the second signal pad.

[0036] Furthermore, in the PCB 80 according to the fourth embodiment of this disclosure, the ground pads are connected to a ground plane located in the lower layer of the laminated substrate via through-hole vias, while the signal pads are electrically connected to surface wiring installed on the surface layer of the PCB and are configured to be connected to external terminals. In addition, in some of the ground planes 81a and 81b, the area directly beneath the signal pads is eliminated in a rectangular shape. Note that in Figure 8, the shape of the ground planes 81a and 81b is shown as rectangular, but the shape can be arbitrary as long as the area directly beneath the signal pads is eliminated.

[0037] In optical communication modules with BGA high-frequency modules (e.g., BGA high-frequency modules 10, 40, or 60) mounted on such a PCB80, the distance between the signal pads and the ground plane is greater than in conventional PCB20 technology. This reduces the capacitive coupling between the ground plane and the signal pads, thereby preventing impedance degradation and suppressing signal quality degradation.

[0038] Furthermore, any form of BGA high-frequency module described herein, including prior art, will achieve the same effect as long as the signal pads and ground pads are arranged facing each other on the PCB80.

[0039] Furthermore, as in the first embodiment, the arrangement in the BGA high-frequency module 60 is not limited to a rectangle, as long as the above-mentioned distance is not deviated. In addition, each pad may further include a ceramic coating restraint (not shown) for strength reinforcement. In addition, as in the second embodiment, connections may be made by sharing at least some of the signal pads and ground pads. [Industrial applicability]

[0040] As described above, the BGA high-frequency module, PCB, and optical communication module on which at least one of these is mounted according to this disclosure can suppress impedance reduction compared to the prior art. Therefore, it is expected to be applied to compact optical transceivers.

Claims

1. BGA high-frequency module, Module components and Displaced on the back surface of the module member, a differential signal pair including a first signal pad and a second signal pad adjacent to the first signal pad, A first ground pad is positioned adjacent to the first signal pad on the opposite side of the second signal pad, A second ground pad is positioned adjacent to the second signal pad on the opposite side of the first signal pad, At least one third ground pad is positioned at a distance from the first signal pad that is greater than a first distance between the first signal pad and the first ground pad, and greater than a second distance between the second signal pad and the second ground pad. At least one fourth ground pad is positioned at a distance greater than the first distance and the second distance from the second signal pad, A BGA high-frequency module comprising the following: no ground pads other than the first and second ground pads exist at the first distance from the first signal pad and the second distance from the second signal pad; and no signal pads exist at the first and second distances from the at least one third ground pad, and no signal pads exist at the first and second distances from the at least one fourth ground pad.

2. The BGA high-frequency module according to claim 1, comprising a plurality of the differential signal pairs and having a structure in which at least one of the ground pads is shared.

3. The BGA high-frequency module according to claim 1 or 2, wherein at least one of the first signal pad, the second signal pad, the first ground pad, the second ground pad, the third ground pad, and the fourth ground pad further comprises a ceramic coating for strength reinforcement.

4. The BGA high-frequency module according to any one of claims 1 to 3, wherein at least one of the first signal pad and the second signal pad has a shape in which at least a portion is cut off in the direction of an adjacent signal pad or an adjacent ground pad.

5. A substrate for a BGA high-frequency module, A differential signal pair is arranged on the back surface of the substrate, and includes a first signal pad and a second signal pad adjacent to the first signal pad. A first ground pad is positioned adjacent to the first signal pad on the opposite side of the second signal pad, A second ground pad is positioned adjacent to the second signal pad on the opposite side of the first signal pad, At least one third ground pad is positioned at a distance from the first signal pad that is greater than a first distance between the first signal pad and the first ground pad, and greater than a second distance between the second signal pad and the second ground pad. At least one fourth ground pad is positioned at a distance greater than the first distance and the second distance from the second signal pad, A substrate for a BGA high-frequency module, wherein no ground pads other than the first and second ground pads exist at the first distance from the first signal pad and the second distance from the second signal pad, and no signal pads exist at the first and second distances from the at least one third ground pad, and no signal pads exist at the first and second distances from the at least one fourth ground pad.

6. A laminated substrate having multiple dielectric parts and multiple ground planes stacked on top of each other, The system includes through-hole vias that electrically connect the ground pad and the ground plane, The substrate for a BGA high-frequency module according to claim 5, wherein at least a portion of the ground plane has a structure that eliminates the portion directly beneath the signal pad.

7. An optical communication module comprising a BGA high-frequency module according to any one of claims 1 to 4 and a substrate for a BGA high-frequency module according to claim 5 or 6.

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