JP2010200234A - Substrate, and system and method for connecting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve excellent electrical connection using a microstrip line, in inter-substrate connection of high-speed signal transmission of, for instance, tens of G bps or more. <P>SOLUTION: This substrate includes: a dielectric layer; a microstrip signal line conductor arranged on a first surface of the dielectric layer; and a ground conductor layer arranged on a second surface of the dielectric layer and constituting a microstrip line along with the microstrip signal line conductor. The length of the microstrip signal line conductor is larger or smaller than that of the ground conductor layer immediately below the microstrip signal line conductor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmission line connection technique, and more particularly to a substrate provided with a transmission line for high-speed signals, a substrate connection method, and a substrate connection method, for example.

  Conventionally, in the connection of a high frequency transmission line, in order to realize good electrical connection characteristics even at a high frequency of about 40 GHz, there is known a method of connecting substrates constituting a coplanar transmission line in which a signal line is sandwiched between grounds ( For example, Patent Document 1).

JP 2007-158856 A

  In the conventional board | substrate currently disclosed by patent document 1, since a coplanar transmission line is used, when forming a transmission line in a flexible printed circuit board, for example, generally from the restrictions on the manufacture precision of a line conductor, a microstrip line is used. Compared with this, there are problems in that the characteristic impedance varies greatly and the wiring layout on the substrate becomes complicated. In addition, in the case of a substrate using a microstrip line, there is a problem in that a ground conductor layer is provided directly below the signal line conductor, so that it cannot be connected as it is.

  The present invention has been made to solve the above-described problems. For example, in a high-speed signal transmission inter-board connection of several tens of Gbps or more, for example, in a flexible printed board, variation in characteristic impedance is small, and on the board. The purpose is to realize a good electrical connection by using a microstrip line with a simple wiring layout.

  The substrate according to the present invention includes a dielectric layer, a microstrip signal line conductor provided on the first surface of the dielectric layer, and a microstrip signal line provided on the second surface of the dielectric layer. And a ground conductor layer that forms a microstrip line with the conductor, and the length of the microstrip signal line conductor is longer or shorter than the length of the ground conductor layer immediately below the microstrip signal line conductor. Is.

  In the present invention, the microstrip signal line conductors can be connected to each other while avoiding the ground conductor layer on the substrate, and a good electrical connection can be realized in high-speed signal transmission of, for example, several tens of Gbps or more using the microstrip line. be able to.

Configuration diagram showing a substrate according to a first embodiment of the present invention. The block diagram which shows the connection system of the board | substrate by Embodiment 1 of this invention Explanatory drawing for demonstrating the board | substrate connection system by Embodiment 1 of this invention. The block diagram which shows the connection system of the board | substrate by Embodiment 2 of this invention Explanatory drawing for demonstrating the board | substrate connection system by Embodiment 2 of this invention. Explanatory drawing for demonstrating the board | substrate connection system by Embodiment 2 of this invention. The block diagram which shows the connection method of the board | substrate by Embodiment 3 of this invention The block diagram which shows the connection system of the board | substrate by Embodiment 4 of this invention The block diagram which shows the connection system of the board | substrate by Embodiment 4 of this invention The block diagram which shows the connection system of the board | substrate by Embodiment 4 of this invention

Embodiment 1 FIG.
1A and 1B are configuration diagrams showing a substrate according to Embodiment 1 of the present invention. FIG. 1A is a plan view showing a first substrate, and FIG. 1B is a plan view showing a second substrate. is there. 2 is a block diagram showing a substrate connection method according to Embodiment 1 of the present invention. FIG. 2 (a) is a plan view, and FIG. 2 (b) is an AA shown in FIG. 2 (a). FIG. 2C is a cross-sectional view taken along the line BB ′ shown in FIG. In each figure, the same numerals indicate the same or corresponding parts. Moreover, in each figure, a broken line shows the part hidden in the shadow of the front part.

  1 and 2, 1 is a dielectric layer of a first substrate which is a flexible printed circuit board, 2 is a microstrip signal line conductor formed on the first surface of the dielectric layer 1, and 3 is a dielectric layer 1. On the other hand, the ground conductor layer 4 is formed on the second surface opposite to the microstrip signal line conductor 2 and forms a microstrip line as a pair with the microstrip signal line conductor 2. Signal conductor pads 4a formed on the surface and used for connection to the second substrate are formed through the dielectric layer 1, and the microstrip signal line conductor 2 is connected to the microstrip described later via the conductor pads 4. Through-hole vias for soldering for electrical connection with the signal line conductor 12, 5 is a conductor pad for ground formed on the first surface of the dielectric layer 1, and 5 a penetrates the dielectric layer 1. Formed Te, a through-hole vias for solder joint used for connection with the second substrate. Note that the dielectric material of the flexible printed circuit board generally has poor thermal conductivity, and solder melting is possible by heat transfer through the conductor pads 4 and 5 and the through-hole vias 4a and 5a.

  1 and 2, 11 is a dielectric layer of a second substrate which is a rigid printed board, 12 is a microstrip signal line conductor formed on the first surface of the dielectric layer 11, and 13 is a dielectric layer. 11 is formed on the second surface opposite to the microstrip signal line conductor 12 and is a ground conductor layer constituting a microstrip line as a pair with the microstrip signal line conductor 12, and 15 is a dielectric layer 11. A ground conductor pad 15a formed on the first surface and used for connection to the first substrate is formed through the dielectric layer 11, and the ground conductor layer 3 is connected to the ground conductor layer via the conductor pad 15. 13 is a through-hole via for electrical connection with the connector 13.

  In FIG. 2, the second surface of the first substrate and the first surface of the second substrate are arranged to face each other, and is a portion near the ends of the conductor pad 4 and the microstrip signal line conductor 12. The end portions are soldered, the positions of the through-hole vias 5a and 15a are aligned, and the end portions near the ends of the ground conductor layer 3 and the conductor pads 15 are solder-joined. The via 4a, the conductor pad 15, and the through-hole via 15a constitute a connection portion.

  Here, the microstrip line is configured as a 50Ω system, the dielectric layer 1 of the flexible printed board is made of polyimide having a thickness of about 50 μm, the microstrip signal line conductor 2 is made about 100 μm in width, and the dielectric of the rigid printed board is used. The body layer 11 is FR-4 having a thickness of about 250 μm, the microstrip signal line conductor 12 has a width of about 400 μm, and the conductor pads 5 and 15 are separated from the conductor pad 4 by about 0.8 mm from the pad center. However, the material and dimensions of the substrate are not limited to this, and are not limited to the 50Ω system.

  Next, the operation will be described. In FIG. 2, in the first substrate, the length of the microstrip signal line conductor 2 is longer than the ground conductor 3 on the back surface directly below the connection end direction with the second substrate. The inter-substrate connection configuration is such that the length of the microstrip signal line conductor 12 is shorter than the ground conductor 13 on the back surface immediately below the connection end direction with the substrate. That is, by forming the ground conductor 3 in a pattern in which the ground conductor 3 is omitted, as shown by the broken line in FIG. 2A, immediately below the end that is the vicinity of the end of the microstrip signal line conductor 2. 3, the end of the microstrip signal line conductor 2 can be connected to the end of the microstrip signal line conductor 12.

  As a result, in the second substrate, the microstrip signal line conductor 12 can be formed without discontinuity after the connection portion between the conductor pad 4 and the first substrate through the through-hole via 4a, and signal transmission without reflection is possible. Thus, the discontinuous portion causing the reflection is only the portion where the ground conductor layer 3 is separated to the left and right in the vicinity of the conductor pad 4 on the first substrate side. At this time, a capacitor is formed by a gap G between the end of the ground conductor 3 immediately below the microstrip signal line conductor 2 on the first substrate and the end of the signal pad 4 and the microstrip signal line conductor 12 on the second substrate. The By this capacitor component, it is possible to compensate for an inductance component that is increased by detouring the return current path to each conductor pad 5 by eliminating the ground conductor 3 immediately below the microstrip signal line conductor 2 in the first substrate, Impedance mismatching at the line discontinuity can be reduced to reduce reflection.

  FIG. 3 shows a simulation result of the electrical reflection characteristics when the horizontal distance of the gap G between the end of the ground conductor 3 immediately below the microstrip signal line conductor 2 on the first substrate and the conductor pad 4 is changed. Here, the horizontal position of the end of the microstrip signal line conductor 12 on the second substrate is the same as the end of the conductor pad 4, the line width (pad lateral width) at the conductor pad 4 on the first substrate is 0.4 mm, and the conductor The vertical width of the pad 4 is 1 mm, and the connection of the microstrip signal line conductor 2 to the conductor pad 4 is assumed to be a taper with a distance of 1.2 mm. In FIG. 3, 21 is a graph when G = 0.2 mm, 22 is G = 0.3 mm, 23 is G = 0.4 mm, and 24 is a graph when G = 0.5 mm.

  In FIG. 3, it is understood that the gap G = 0.3 to 0.4 mm is effective particularly when the object is to reduce the reflection to a high frequency of 20 GHz. If it is up to 15 GHz, it is also effective to widen the gap G to 0.5 mm. On the other hand, if the gap G is made too small, a short circuit at the time of solder mounting becomes a problem. However, as shown in FIG. It is effective to prescribe at 3 mm or more.

  As described above, in the substrate connection method according to the first embodiment of the present invention, the first substrate is connected to the second substrate in the direction of the connection end, and the length of the microstrip signal line conductor 2 is the ground directly below. The length of the microstrip signal line conductor 12 is shorter than that of the ground conductor 13 directly below the second substrate with respect to the direction of the connection end with the first substrate. As a result, the microstrip signal line conductors can be connected to each other while avoiding the ground conductor layer, the characteristic impedance variation is small even in the flexible printed circuit board, and the wiring layout on the board is simple, and the microstrip line is used for 20 GHz. A good electrical connection over a high frequency can be realized. In particular, the high frequency characteristics can be improved by canceling the inductance component with the capacitance component at the connection portion.

Embodiment 2. FIG.
As described above, the substrate connection method according to the first embodiment of the present invention is such that the high frequency characteristics can be improved by canceling out the inductance component by the capacitance component, but the second embodiment of the present invention. The substrate connection method is for reducing the effective inductance value itself in order to achieve low reflection over a wider band.

  FIGS. 4A and 4B are configuration diagrams showing a board connection method according to Embodiment 2 of the present invention. FIG. 4A is a plan view, and FIG. 4B is AA ′ shown in FIG. FIG. In each figure, the same numerals indicate the same or corresponding parts. Moreover, in each figure, a broken line shows the part hidden in the shadow of the front part. In FIG. 4, reference numeral 6 denotes a ground conductor pad formed on the first surface of the dielectric layer 1 adjacent to the microstrip signal line conductor 2, and reference numeral 6 a denotes a dielectric layer adjacent to the microstrip signal line conductor 2. 1 is formed on the first surface of the dielectric layer 11, and is formed in the first surface of the dielectric layer 11. A ground conductor pad 16 a used for connection to the substrate is formed through the dielectric layer 11 and is a through hole for electrically connecting the ground conductor layer 3 to the ground conductor layer 13 via the conductor pad 16. Beer. The configuration is the same as that of the substrate connection system according to the first embodiment of the present invention except that the conductor pads 6 and 16 and the through-hole vias 6a and 16a are added. Note that the dielectric material of the flexible printed circuit board generally has poor thermal conductivity, and solder melting is possible by heat transfer through the conductor pads 4, 5, 6 and the through-hole vias 4a, 5a, 6a.

  In FIG. 4, the second surface of the first substrate and the first surface of the second substrate are arranged to face each other, and the conductor pad 4 and the end portion of the microstrip signal line conductor 12 are soldered together. Then, the positions of the through-hole vias 5a and 15a are aligned and the end portions of the ground conductor layer 3 and the conductor pads 15 are soldered together, and the positions of the through-hole vias 6a and 16a are aligned and the vicinity of the end of the ground conductor layer 3 The conductor pad 16, the through-hole via 4a, the conductor pad 15, the through-hole via 15a, the conductor pad 16, and the through-hole via 16a constitute a connecting portion.

  Next, the operation will be described. In FIG. 4, the return current path is shortened by ground connection between the first substrate and the second substrate by the conductor pads 6 and 16 formed close to the microstrip signal line conductor 2 and the through-hole vias 6a and 16a. It is effective to do. FIG. 5 shows an example of simulation results compared with and without ground connection by the conductor pads 6 and the like. The two conductor pads 6 each have a center-to-center distance of 0.5 mm from the microstrip signal line conductor 2 and a horizontal distance from the end of the signal pad 4 of 0.7 mm.

  In FIG. 5 (a), 31a and 32a are the ground connection by the conductor pads 6 etc., respectively, and are reflection characteristics in the case where there is, and in FIG. 5 (b), 31b and 32b are ground connections by the conductor pads 6 etc. It is a Smith chart when there is no. From FIG. 5, the addition of the ground connection by the conductor pad 6 or the like reduces the reflection over the wide band from DC to 50 GHz, and the circle diameter of the Smith chart also circulates inward, reducing the inductance component. I understand that.

  Here, as a reference comparison, the ground connection by the conductor pad 6 or the like is not added, and the conductor pad 5 of the first substrate is simply brought close to the microstrip signal line conductor 2 by 0.3 mm, and similarly the second substrate FIG. 6 shows a simulation result when the conductor pad 15 and the through-hole via 15a are also brought close to the microstrip signal line conductor 12 by 0.3 mm. At this time, the reflection characteristic shown in FIG. 6 is deteriorated as compared with the reflection characteristic shown in FIG. This is presumably because the gap between the pads is small and the coupling between the signal conductor pad and the ground conductor pad becomes too large.

  That is, first, as in the case of FIG. 5 (a), when the ground connection by the conductor pad 6 or the like is used, the flexible printed circuit board considered as the first substrate has the dielectric layer 1 made of film-like polyimide. Since the thickness is as thin as about 50 μm, the electric field is strongly coupled to the ground conductor 3, and the coupling is relatively very weak even when the conductor pad 6 is close to the microstrip signal line conductor 2. On the other hand, when the ground conductor pad 15 is brought close to the microstrip signal line conductor 12 as in the case of FIG. 6, the rigid printed circuit board considered as the second board has the dielectric layer 11 of FR. -4, the thickness is about 250 μm, which is thicker than the first substrate, and the coupling to the relatively adjacent ground conductor pads is increased, so that the characteristics are significantly affected and deteriorated. As described above, in the substrate connection method according to the second embodiment of the present invention, the second substrate has the ground conductor 13 in which the length of the microstrip signal line conductor 12 is directly below the connection end direction with the first substrate. Since the inter-substrate connection configuration is shorter than that, the ground connection by the conductor pad 6 or the like can be employed in the region where the microstrip signal line conductor 12 is eliminated without being affected by the coupling with the microstrip signal line conductor 12. It is.

  As described above, in the substrate connection system according to the second embodiment of the present invention, the ground connection between the first substrate and the second substrate by the through-hole via formed close to the microstrip signal line conductor 2 is performed. As a result, the return current path is shortened. Thereby, in addition to the effect similar to Embodiment 1 of this invention, the favorable electrical connection over a high frequency of 50 GHz is realizable using a microstrip line. In particular, it is possible to further improve the high-frequency characteristics by reducing the effective inductance in the connection portion.

  In the connection method of the substrate according to the second embodiment of the present invention, the conductor pad is used for the purpose of comparison of the operation effect with the connection method of the substrate according to the first embodiment of the present invention and to obtain a mechanical joint strength equal to or higher than that. 5 is used in combination with the ground connection by the conductor pad 6 or the like, but the ground connection by the conductor pad 5 or the like, that is, the conductor pads 5 and 15 and the through-hole vias 5a and 15a may be omitted. is there.

Embodiment 3 FIG.
As described above, the substrate connection method according to the second embodiment of the present invention is based on the ground connection between the first substrate and the second substrate by the through-hole via formed close to the microstrip signal line conductor 2. Although solder bonding using the conductor pads 6 and the through-hole vias 6a is used, the substrate connection system according to the third embodiment of the present invention uses a conductive adhesive.

  FIG. 7 is a plan view as a configuration diagram showing a substrate connection method according to the third embodiment of the present invention. In each figure, the same numerals indicate the same or corresponding parts. Moreover, in each figure, a broken line shows the part hidden in the shadow of the front part. In FIG. 7, instead of the solder bonding by the conductor pad 6 and the through-hole via 6a shown in FIG. 4, the ground conductor 3 and the conductor pad 16 are bonded using the conductive adhesive 17, thereby the first substrate. The ground conductor 3 is connected to the ground conductor 13 of the second substrate. The configuration is the same as that of the substrate connection method according to the second embodiment of the present invention except that the conductive adhesive 17 is used instead.

  In FIG. 7, the second surface of the first substrate and the first surface of the second substrate are arranged to face each other, and the conductor pad 4 and the end portion of the microstrip signal line conductor 12 are soldered together. Then, the end portions of the ground conductor layer 3 and the conductor pads 15 are soldered together by aligning the positions of the through-hole vias 5 a and 15 a, and the end portions of the ground conductor layer 3 and the conductor pads 16 are bonded with the conductive adhesive 17. The conductive pad 4, the through-hole via 4a, the conductive pad 15, the through-hole via 15a, the conductive pad 16, the through-hole via 16a, and the conductive adhesive 17 constitute a connecting portion.

  Next, the operation will be described. The effect of the substrate connection method according to the third embodiment of the present invention is the same as that of the substrate connection method according to the second embodiment of the present invention, and is formed close to the microstrip signal line conductor 2. It is effective to shorten the return current path by ground connection between the first substrate and the second substrate by the through-hole via 16a, the conductor pad 16, and the conductive adhesive 17.

  As described above, in the substrate connection system according to the third embodiment of the present invention, the first through the through-hole via 16a, the conductor pad 16, and the conductive adhesive 17 formed in the vicinity of the microstrip signal line conductor 2. The return current path is shortened by ground connection between the first substrate and the second substrate. Thereby, in addition to the effect similar to Embodiment 1 of this invention, the favorable electrical connection over a high frequency of 50 GHz is realizable using a microstrip line. In particular, the high frequency characteristics can be improved by reducing the effective inductance in the connection portion.

  In the substrate connection system according to the third embodiment of the present invention, it is possible to omit the conductor pads 5 and 15 and the through-hole vias 5a and 15a as in the second embodiment of the present invention. It is.

Embodiment 4 FIG.
As described above, the board connection method according to the first to third embodiments of the present invention is applied to a pair of microstrip signal line conductors on the first board and the second board. The substrate connection method according to the third embodiment of the present invention is such that the microstrip signal line conductors of the first substrate and the second substrate are applied to two pairs, that is, differential lines.

  8 to 10 are plan views as configuration diagrams showing a substrate connection method according to the fourth embodiment of the present invention. In each figure, the same numerals indicate the same or corresponding parts. Moreover, in each figure, a broken line shows the part hidden in the shadow of the front part. 8 to 10, in place of the pair of microstrip signal line conductors 1 and 12 shown in FIGS. 2, 4, and 7, two pairs of microstrip signal line conductors 2-1 and 2- 2, 12-1, and 12-2 are provided. The configuration is the same as that of the substrate connection method according to the first to third embodiments of the present invention except that the differential line is used instead.

  Next, the operation will be described. The effect of the substrate connection method according to the fourth embodiment of the present invention is the same as that of the substrate connection method according to the first to third embodiments of the present invention, and can be applied to a microstrip line as a differential line. It is.

  As described above, in the substrate connection method according to the fourth embodiment of the present invention, a microstrip line as a differential line having a small variation in characteristic impedance even on a flexible printed board and a simple wiring layout on the substrate is provided. By using it, it is possible to realize a good electrical connection over a high frequency of several tens of GHz, and the same effects as in the first to third embodiments of the present invention can be achieved.

  Of the substrate connection methods according to the fourth embodiment of the present invention, the one shown in FIGS. 9 and 10 is similar to the second embodiment of the present invention in that the conductor pads 5 and 15 and the through-hole vias 5a. , 15a can be omitted.

1, 11 Dielectric layers 2, 12, 2-1, 2-2, 12-1, 12-2 Microstrip signal line conductors 3, 13 Ground conductor layers 4, 5, 6, 15, 16 Conductor pads 4a, 5a 6a, 15a, 16a Through-hole via 17 Conductive adhesive

Claims (9)

A dielectric layer;
A microstrip signal line conductor provided on the first surface of the dielectric layer;
A ground conductor layer provided on the second surface of the dielectric layer and forming a microstrip line with the microstrip signal line conductor;
A substrate characterized in that the length of the microstrip signal line conductor is longer or shorter than the length of the ground conductor layer immediately below the microstrip signal line conductor. The first substrate as the substrate according to claim 1, wherein a length of the microstrip signal line conductor is shorter than a length of the ground conductor layer immediately below the microstrip signal line conductor;
The second substrate as the substrate according to claim 1, wherein the length of the microstrip signal line conductor is shorter than the length of the ground conductor layer immediately below the microstrip signal line conductor;
The second surface of the first substrate and the first surface of the second substrate are arranged to face each other, and the end of the microstrip signal line conductor of the first substrate and the second substrate Electrically connecting the end of the microstrip signal line conductor, and connecting the end of the ground conductor layer of the first substrate and the ground conductor layer of the second substrate;
A board connection method characterized by comprising:   The distance between the end of the ground conductor layer immediately below the microstrip signal line conductor of the first substrate and the end of the microstrip signal line conductor of the second substrate is 0.3 mm or more and 0.4 mm or less. The board connection system according to claim 2, wherein:   The connection portion is a solder pad joined to an end portion of the microstrip signal line conductor of the second substrate by solder and a dielectric layer of the first substrate provided on the second surface of the first substrate An end portion of the microstrip signal line conductor of the first substrate and an end portion of the microstrip signal line conductor of the second substrate are electrically connected through a through-hole via provided through the first substrate. The board connection method according to claim 2 or 3,   The connection portion is joined to an end portion of the ground conductor layer of the first substrate by solder and penetrates a conductor pad provided on the first surface of the second substrate and a dielectric layer of the second substrate. The end portion of the ground conductor layer of the first substrate and the ground conductor layer of the second substrate are electrically connected through a through-hole via provided as described above. The board | substrate connection system in any one of Claim 4.   The connection portion includes a conductive pad attached to an end portion of the ground conductor layer of the first substrate with a conductive adhesive and provided on the first surface of the second substrate, and a dielectric of the second substrate. The end portion of the ground conductor layer of the first substrate and the ground conductor layer of the second substrate are electrically connected to each other through a through-hole via provided through the layer. The board | substrate connection system in any one of Claims 2-4.   7. The substrate connection system according to claim 2, wherein the microstrip signal line conductors of the first and second substrates are differential lines.   The board connection method according to claim 2, wherein the first board is a flexible printed board. 2. The first substrate as the substrate according to claim 1, wherein a length of the microstrip signal line conductor is longer than a length of the ground conductor layer immediately below the microstrip signal line conductor, and the microstrip signal line. 2. The substrate connection method for connecting a second substrate as a substrate according to claim 1, wherein the length of the microstrip signal line conductor is shorter than the length of the ground conductor layer immediately below the conductor. And
The second surface of the first substrate and the first surface of the second substrate are arranged to face each other, and the end of the microstrip signal line conductor of the first substrate and the second substrate An end of the microstrip signal line conductor is electrically connected, and an end of the ground conductor layer of the first substrate is electrically connected to a ground conductor layer of the second substrate. Board connection method.

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