JP2014216374A - Parallel optical communication module and assembly of printed board mounting parallel optical communication module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parallel optical communication module that can simplify wiring on a printed board.SOLUTION: A parallel optical communication module 100 includes a module board 1, and on an electrode surface 13 of the module board 1, a plurality of high-speed signal electrodes 6 and a plurality of high-frequency wave ground electrodes 11 are arranged such that they form a first square lattice 28. The high-speed signal electrodes 6 are not situated on lattice points 30g of the outermost periphery of the electrode surface 13, and are positive phase signal electrodes 15 or reversed phase signal electrodes 16. Both form a pair of high-speed signal electrodes 26 by being arranged on lattice points 30a, 30b next to each other in the direction inclined at 45 degrees from a lattice line 29 of the first square lattice 28. A lattice point on a straight line 34 in one side relative to a line segment 27 among a perpendicular bisector 24 of the line segment 27 connecting both is an electrode unoccupied lattice point 35. The high-frequency wave ground electrodes 11 are arranged on lattice points excluding the electrode unoccupied lattice point 35 among adjacent lattice points around the pair of high-speed signal electrodes 26.

Description

  The present invention relates to a parallel optical communication module and a printed circuit board assembly on which the parallel optical communication module is mounted.

  In recent years, computer computing speed has been dramatically improved by new technologies such as GPU (Graphics Processing Unit) computing. In particular, in a high performance computer that simultaneously operates a large number of CPUs (Central Processing Units) and GPUs, the communication speed between nodes is becoming a bottleneck rather than the calculation speed. Further, since the distance between nodes becomes longer as the number of nodes increases, the interconnection technology for connecting the nodes is 1. 1. High speed 2. a relatively long distance; There is a demand for data communication with low power consumption.

  It is difficult to meet such requirements with the related electrical interconnection technology, and attention is focused on the optical interconnection technology.

  Among optical interconnection technologies, parallel optical interconnection, which combines a parallel optical communication module in which multiple optical elements and drive circuits are mounted on a single substrate, and an array optical fiber in which multiple optical fibers are combined into one, is the mainstream. It has become.

  When paying attention to the electrical interface of the parallel optical communication module, a differential transmission method is used for wiring that performs high-speed communication by transmitting a pair of a normal phase signal and a reverse phase signal. While this method has an advantage of being resistant to external noise, two transmission lines are required for one signal, and there is a problem that wiring becomes difficult as the size and pitch of modules increase. In addition, it is important that the surrounding ground of the high-speed signal wiring is stable. In order to strengthen the ground of the high-speed signal wiring, a ground electrode is arranged around the high-speed signal electrode (FIG. 8; P, N Are the positive and negative signal electrodes, and the hatch is the ground electrode).

  An FR-4 multilayer substrate is excellent at low cost as a printed circuit board for mounting such a parallel optical communication module. Therefore, when an attempt is made to form a grounded coplanar differential wiring on an FR-4 multilayer substrate (relative permittivity˜4.7, thickness t = 0.15 mm of each layer), for example, a wiring width of 0.10 mm, a differential line A differential transmission line of 100Ω can be designed by setting the distance to 0.08 mm and the wiring-to-ground distance to 0.10 mm. In order to wire this differential transmission line, a lateral width of about 0.5 mm is required. For this reason, if the electrode pitch is up to about 1 mm, the differential transmission line can be drawn to the outside. However, as shown in FIG. 9, at a narrower interval (0.7 mm pitch in FIG. 9). If the ground electrode is not deleted at the expense of the characteristics, the wiring cannot be drawn to the outside.

  With respect to this problem, Patent Document 1 makes it easy to pull out the wiring by arranging the signal terminals on the outermost periphery of the module substrate of the parallel optical communication module.

JP 2010-177578 A

  However, in the method of Patent Document 1, as shown in FIG. 10, the signal wiring on the printed circuit board side must be complicated to avoid the ground electrode. In the case of a signal line having a complicated shape, it is difficult to make the normal-phase and reverse-phase lines symmetrical, and there is a problem that the balance of impedance is lost and skew occurs. Further, since the signal wiring has a complicated shape, a ground cannot be provided between adjacent channels, and crosstalk between channels occurs. This inter-channel crosstalk becomes particularly prominent when the number of channels is increased.

  Furthermore, naturally, a transmission line having a complicated shape has a problem that the impedance tends to deviate from a design value due to an error in manufacturing.

  An object of the present invention is to provide a parallel optical communication module capable of simplifying wiring of a printed circuit board.

  The parallel optical communication module includes an optical element, an electronic element for driving the optical element, and a module substrate on which the optical element and the electronic element are mounted on one surface, and the other of the module substrates The surface is an electrode surface, and a plurality of high-speed signal electrodes and a plurality of high-frequency ground electrodes are arranged on lattice points of the first square lattice, and the high-speed signal electrodes are on lattice points on the outermost periphery of the electrode surface. The high-speed signal electrode is a positive-phase signal electrode or a negative-phase signal electrode, and the positive-phase signal electrode and the negative-phase signal electrode are 45 degrees from the lattice line of the first square lattice. A high-speed signal electrode pair is formed by being arranged on lattice points adjacent to each other in an inclined direction, and a line segment connecting the positive-phase signal electrode and the negative-phase signal electrode constituting the high-speed signal electrode pair. One side of the vertical bisector with respect to the line Grid points on a straight line are electrode unoccupied grid points that are not occupied by either the high-speed signal electrode or the high-frequency ground electrode, and the high-frequency ground electrode is adjacent to the periphery of the high-speed signal electrode pair. The grid points are arranged at grid points excluding the electrode unoccupied grid points.

  The present invention can provide a parallel optical communication module that can simplify the wiring of a printed circuit board.

It is a top view of the component mounting surface of the parallel optical communication module which concerns on 1st Embodiment. It is a perspective view of the electrode surface of the parallel optical communication module which concerns on 1st Embodiment. It is a perspective view of the ground layer of the parallel optical communication module concerning a 1st embodiment. It is a figure which shows the high frequency wiring pattern of the printed circuit board in 1st Embodiment. It is a perspective view of the electrode surface of the parallel optical communication module which concerns on 2nd Embodiment. It is a figure which shows the high frequency wiring pattern of the printed circuit board in 2nd Embodiment. It is a figure which shows the sink of the electrode pad in a pad on via system. It is a figure which shows the electrode of a related parallel optical communication module. It is a figure which shows the wiring by the side of the board | substrate which mounts a related parallel optical communication module. It is a figure which shows the wiring by the side of the board | substrate which mounts the parallel optical communication module of patent document 1. FIG.

  1 and 2 are a top view of a component mounting surface and a perspective view of an electrode surface of the parallel optical communication module 100 according to the first embodiment of the present invention, respectively.

The module substrate 1 is a five-layer substrate made of alumina (Al ₂ O ₃ ) ceramics. The component mounting surface 5 on the first layer surface is the differential transmission line 2 and the IC control wiring. (Not shown), a power supply pattern (not shown) and the like are formed, and electrodes for electrical connection are arranged on the electrode surface 13 on the back surface of the fifth layer.

  On the component mounting surface 5, a surface type optical element 3, an optical element driving IC (electronic element) 4 for driving the optical element, and a bypass capacitor (not shown) are mounted. The planar optical element 3 is mounted on the module substrate 1 so that the light input / output surface faces upward, and is electrically connected to the wiring by wire bonding. The optical element driving IC 4 is flip-chip mounted, and is electrically connected to the wiring on the module substrate 1 by solder balls. The number of differential transmission lines 2 connected to the optical element driving IC 4 is the same as the number of channels of the surface optical element 3 (two pairs, that is, four in this embodiment) formed on the component mounting surface 5. The signal electrode 6 and the via 7 are connected.

  The second layer is a ground layer 8, and a high frequency ground 9 and a power supply ground 10 for the differential transmission line 2 are divided and formed to reduce noise as shown in FIG. These grounds are connected via a ground electrode 11 on the electrode surface 13 and a ground via 12 (only a part is shown).

  As shown in FIG. 2, in addition to the high-speed signal electrode 6, a high-frequency ground electrode 11, a power supply electrode, a control electrode, and the like are virtually formed on the fifth layer electrode surface 13. It is arranged on the lattice points of the lattice 28). The high-speed signal electrode 6 is not present at the outermost lattice point 30 g of the electrode surface 13. The high-speed signal electrode 6 is a positive-phase signal electrode 15 or a negative-phase signal electrode 16. Both are arranged on lattice points 30a and 30b adjacent to each other in a direction inclined by 45 degrees from the lattice line 29 of the first square lattice 28, thereby forming a high-speed signal electrode pair 26. Of the vertical bisectors 24 of the line segment 27 connecting the positive-phase signal electrode 15 and the negative-phase signal electrode 16 constituting the high-speed signal electrode pair 26, the line segment 27 lies on a straight line 34 on one side. The lattice point 30 c is an electrode unoccupied lattice point 35 that is not occupied by either the high-speed signal electrode 6 or the high-frequency ground electrode 11. The high-frequency ground electrode 11 is arranged at a lattice point 30 d excluding the electrode unoccupied lattice point 35 among the lattice points 30 d around the high-speed signal electrode pair 26.

  In other words, out of the lattice points 30d around the high-speed signal electrode pair 26, the lattice points 30e form a right-angled isosceles triangle in combination with the two lattice points 30a and 30b of the high-speed signal electrode pair 26, and the outer periphery thereof. The high-frequency ground electrode 11 is disposed only at the lattice point 30d excluding the lattice point 30f.

  Next, a high-frequency wiring pattern of the printed circuit board 17 (assembly) on which the parallel optical communication module 100 is mounted will be described with reference to FIG. The electrode surface 13 of the module substrate 1 of the parallel optical communication module 100 faces the printed circuit board 17. The electrodes are arranged on the virtual first square lattice 28 on the electrode surface 13 of the module substrate 1, but the second square lattice 31 exactly the same as the first square lattice is also formed on the printed circuit board 17. It is virtually formed and lands are arranged on it. High-speed signal lands 18 and high-frequency ground lands 20 are formed at positions on the printed circuit board 17 corresponding to the high-speed signal electrodes 6 and the high-frequency ground electrodes 11 on the electrode surface 13, respectively. Corresponding to the high-speed signal electrode pair 26 on the electrode surface 13, the high-speed signal land 18 arranged on the lattice points 37 a and 37 b adjacent to each other in the direction inclined 45 degrees from the lattice line 32 of the second square lattice 31. Form a land pair 36.

  On the electrode surface 13 of the module substrate 1, ground electrodes are missing at locations such as the lattice points 30 e and 30 f, but the lattice points 37 c and 37 d of the second square lattice 31 on the printed circuit board 17 corresponding thereto are also present. The high frequency ground land 20 is missing.

  That is, among the vertical bisectors 39 of the line segment 38 connecting the two high-speed signal lands 18 constituting the land pair 36, the lattice point on the straight line 40 on one side with respect to the line segment 38 indicates the high-speed signal. The land unoccupied lattice points 41 are not occupied by either the land 18 or the high frequency ground land 20.

  Therefore, a grounded coplanar line is drawn from the land pair 36 through the land unoccupied lattice point 41. For example, in the example of FIG. 4, the line is led out from the right land pair 36 through the lattice points 37c and 37d. The grounded coplanar line 19 is advantageous in that it is resistant to ambient noise and can be easily connected to an IC or the like. On the other hand, the high-frequency ground land 20 is disposed so as to surround the periphery of the line 19 as the ground of the coplanar line 19 and is connected to the ground of the inner layer of the printed circuit board 17 by vias.

  According to the configuration of the present embodiment, since the differential transmission line 2 and the high-frequency ground electrode 11 are arranged symmetrically, impedance balance and skew control can be easily performed. Since the signal wiring has a simple shape, a ground can be provided between adjacent channels, and crosstalk between channels hardly occurs. Furthermore, the transmission line having a simple shape has an advantage that the impedance is less likely to deviate from the design value due to an error in manufacturing.

  In addition, a space is secured for leading out the high-frequency wiring from the high-speed signal electrode 6 disposed on the inner periphery of the parallel optical communication module 100 to the outer periphery. That is, by arranging the signal electrode 15 having the normal phase and the signal electrode 16 having the opposite phase on the lattice points 30a and 30b adjacent to each other in the direction inclined by 45 degrees from the lattice line 29 of the square lattice 28, the lattice line 29 The wiring width can be increased by about 1.4 times as compared with the case where the wirings are arranged on lattice points adjacent to each other. As a result, fluctuations in impedance can be suppressed with respect to variations in wiring width.

  In Patent Document 1, since the signal electrode is on the outermost periphery of the electrode surface, noise resistance is low because the signal electrode and the via are directly exposed to radiation noise from the outside. On the other hand, in the present invention, since the signal electrode 6 is surrounded by the ground electrode 11, the effect of being sufficiently guarded against external noise can be obtained.

  As described above, the design of the external interface of the parallel optical communication module 100 is facilitated, and the characteristics are stabilized against variations at the time of manufacture, so that the printed circuit board can be manufactured by an inexpensive process.

  FIG. 5 is a perspective view of the electrode surface 13 (part) of the parallel optical communication module 100 according to the second embodiment of the present invention as viewed from the component mounting surface 5. As shown in FIG. 5, in addition to the high-speed signal electrodes 15 and 16, a high-frequency ground electrode 11, a power supply electrode, a control electrode, and the like are arranged on the electrode surface 13 in a square lattice pattern.

  When the number of channels of the parallel optical communication module 100 increases, the number of electrodes increases only by arranging the high-speed signal electrodes 15 and 16 along the outer periphery of the module 100, and the outer shape of the module 100 increases. Therefore, in order to keep the size of the module 100 small, the high-speed signal electrodes 15 and 16 are arranged on the inner periphery of the electrode surface 13 of the module substrate 1 (P4 and N4 in FIG. 5).

  Next, a high-frequency wiring pattern of the printed circuit board 17 (assembly) on which the parallel optical communication module 100 of the second embodiment is mounted will be described with reference to FIG. The electrode surface 13 of the module substrate 1 of the parallel optical communication module 100 faces the printed circuit board 17. The electrodes are arranged on the first square lattice 28 virtually formed on the electrode surface 13 of the module substrate 1, but the same as the first square lattice 28 on the printed circuit board 17. A third square lattice 33 is virtually formed, and lands are arranged thereon. High-speed signal lands 18 and high-frequency ground lands 20 are formed at positions on the printed circuit board 17 corresponding to the high-speed signal electrodes 6 and the high-frequency ground electrodes 11 on the electrode surface 13, respectively.

  When the lines arranged on the inner periphery of the module substrate 1 are drawn out to the outer periphery, if the number of wirings is small, wiring can be performed between the outer peripheral electrodes, but the number of wirings is large as in this embodiment. In this case, it is desirable that the high frequency wiring 25 is formed in the inner layer of the printed circuit board 17 and the high speed signal land 18 is connected to the high frequency wiring 25 through the high speed signal via 21.

  However, as shown in FIG. 7, in the pad-on-via method in which the electrode pad 23 for the high-speed signal electrode 6 immediately above the high-speed signal land 18 is disposed immediately above the via 21 for high-speed signal, sink marks 22 are formed on the electrode pad 23. Occurs and there is a problem in connection reliability with the module. In the present embodiment, the position of the via 21 of the high-speed signal is shifted from the grid point on the electrode pad 23, that is, the land 18 of the high-speed signal on the plane where the third square lattice 33 of the printed circuit board 17 is formed. The position can be set, and connection reliability problems do not occur.

  According to this embodiment, even when the number of channels of the parallel optical communication module 100 is increased, the module 100 can be downsized.

  In the present embodiment, the portion on one side of the line segment 27 of the vertical bisector 24 of the line segment 27 connecting the positive-phase signal electrode 15 and the negative-phase signal electrode 16 constituting the high-speed signal electrode pair 26. It is not necessary that the high-frequency ground electrode 11 is missing at the lattice point on the half line. The high-speed signal electrodes 15 and 16 do not need to be disposed on the inner periphery of the module substrate 1. Further, the lands need not be arranged in a square lattice pattern.

DESCRIPTION OF SYMBOLS 1 Module board | substrate 2 Differential transmission line 3 Plane type optical element 4 Optical element drive IC
5 Component mounting surface 6 High-speed signal electrode 7 Signal line via 8 Ground layer 9 High-frequency ground 10 Power supply ground 11 Ground electrode 12 Ground via 13 Electrode surface 15 Positive-phase signal electrode 16 Reverse-phase signal electrode 17 Printed circuit board 18 High-speed signal land 19 Grounded Coplanar Line 20 High Frequency Ground Land 21 High Speed Signal Via 22 Pad Sink 23 Electrode Pads 24, 39 Vertical Bisecting Line 25 Inner Layer Wiring 26 High Speed Signal Electrode Pairs 27, 38 Line Segment 28 First Square Lattice 29 32 Lattice lines 30a, 30b, 30c, 30d, 30e, 30f, 30g Lattice point 31 Second square lattice 33 Third square lattice 34, 40 Straight line 35 Electrode unoccupied lattice point 36 Land pair 37a, 37b, 37c, 37d Lattice point 41 Land unoccupied lattice point 100 Parallel optical communication module

Claims (4)

An optical element, an electronic element for driving the optical element, and a module substrate on which the optical element and the electronic element are mounted on one surface,
The other surface of the module substrate is an electrode surface, and a plurality of high-speed signal electrodes and a plurality of high-frequency ground electrodes are arranged on lattice points of the first square lattice,
The high-speed signal electrode is not on the outermost lattice point of the electrode surface,
The high-speed signal electrode is a positive-phase signal electrode or a negative-phase signal electrode, and the positive-phase signal electrode and the negative-phase signal electrode are inclined at 45 degrees from the lattice line of the first square lattice. A high-speed signal electrode pair is formed by being arranged on lattice points adjacent to each other,
Among the vertical bisectors connecting the positive-phase signal electrode and the negative-phase signal electrode constituting the high-speed signal electrode pair, lattice points on a straight line on one side with respect to the line segment are: Electrode unoccupied lattice points that are not occupied by either the high-speed signal electrode or the high-frequency ground electrode,
The high-frequency ground electrode is a parallel optical communication module arranged at lattice points excluding the electrode unoccupied lattice points among lattice points adjacent around the high-speed signal electrode pair. An assembly comprising the parallel optical communication module according to claim 1 and a printed circuit board,
The printed circuit board includes a high-speed signal land, a high-frequency ground land, and a grounded coplanar line.
The electrode surface of the parallel optical communication module faces the printed board,
The high-speed signal land and the high-frequency ground land on the printed circuit board respectively corresponding to the high-speed signal electrode and the high-frequency ground electrode on the electrode surface are second square lattices corresponding to the first square lattice. Are placed on the grid points of
The high-speed signal lands arranged on lattice points adjacent to each other in a direction inclined by 45 degrees from the lattice line of the second square lattice form a land pair,
Of the perpendicular bisectors connecting the two high-speed signal lands constituting the land pair, lattice points on a straight line on one side with respect to the line segment are opposed to the electrode unoccupied lattice points. A land unoccupied lattice point that is not occupied by either the high-speed signal land or the high-frequency ground land,
The assembly in which the coplanar line with the ground is led out from the land pair through a land unoccupied lattice point. An assembly comprising the parallel optical communication module according to claim 1 and a printed circuit board,
The printed circuit board has high-speed signal lands, high-frequency ground lands, and vias, and high-frequency wiring is formed in an inner layer of the printed circuit board.
The electrode surface of the parallel optical communication module faces the printed board,
The high-speed signal land and the high-frequency ground land on the printed circuit board corresponding to the high-speed signal electrode and the high-frequency ground electrode on the electrode surface, respectively, of a third square lattice corresponding to the first square lattice. Are placed on grid points,
The assembly of the high-speed signal is connected to the high-frequency wiring formed in the inner layer of the printed board through the via.   The assembly according to claim 3, wherein the via is located at a position shifted from a lattice point on which the land of the high-speed signal is located on a plane on which the third square lattice of the printed circuit board is formed.

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