WO2011114704A1

WO2011114704A1 - Circuit board

Info

Publication number: WO2011114704A1
Application number: PCT/JP2011/001494
Authority: WO
Inventors: 柴田健
Original assignee: シャープ株式会社
Priority date: 2010-03-16
Filing date: 2011-03-15
Publication date: 2011-09-22

Abstract

Disclosed is a technique for producing a high-speed digital transmission line capable of transmitting a signal in a steady manner using a substrate having an inexpensive structure. As illustrated in Fig. 2, a circuit board (10) is composed of two substrates, i.e., a lower substrate (20) and an upper substrate (40) both of which are one-side substrates, wherein the upper substrate (40) is so adapted as to cover a high-speed digital line (30) in the lower substrate (20). In the installation of the lower substrate (20) and the upper substrate (40), a metal sheet (60) is arranged adjacent to both ends of the upper substrate (40) so that ground planes of the lower substrate (20) and the upper substrate (40) are connected to each other.

Description

Circuit board

The present invention relates to a circuit board, and more particularly to a circuit board on which a high-speed transmission path is formed.

In recent years, home appliances in which high-speed transmission paths such as HDMI (High-Definition Multimedia Interface) and LVDS (Low Voltage differential signaling) are configured are increasing. In general, a high-speed transmission line is realized by using a multilayer substrate on which a microstrip line can be easily configured, thereby realizing a stable transmission line. FIG. 1A shows a circuit board (cross section) 100 having a two-layer structure, which is a basic structure of a microstrip line. A ground plane 130 which is a conductive layer is formed on the lower side of the insulating substrate 120, and a signal layer 110 is formed on the upper side. FIG. 1B shows a circuit board (cross section) 200 of a microstrip line having a four-layer structure used for realizing good characteristics. The circuit board 200 has first to third insulating layers 220a to 220c. A ground plane 231 that is a conductive layer is formed below the third insulating layer 220c, and a signal layer 210 is formed above the first insulating layer 220a.

Conductive layers

232 and 233 are formed between the first and second

insulating layers

220a and 220b and between the second and third

insulating layers

220b and 220c, respectively.

In addition, various techniques have been proposed for reducing the cost and improving the transmission quality during high-speed transmission in a circuit board provided with a microstrip line. For example, the following circuit board is disclosed. That is, the circuit board includes a first insulating layer disposed on a conductive layer having a ground potential or the like, a first wiring and a second wiring disposed on the first insulating layer, a first wiring, and the first wiring. A second insulating layer covering the second wiring, an electrode terminal provided on the second insulating layer and electrically connected to the first wiring or the second wiring, the second insulating layer and the first wiring And a conductive pattern provided above the second wiring and including the same layer structure as the electrode terminal (see, for example, Patent Document 1). This circuit board suppresses low cost and crosstalk (noise) between wires.

JP 2010-21468 A

Incidentally, it has become common for input / output terminals such as HDMI to be mounted even on low-cost TVs. As a result, a low-cost configuration that cannot be assumed in the past has been demanded. In general, a substrate having a layer configuration of four or more layers is ideal for forming a stable high-speed digital transmission line. However, in the circuit premised on the multilayer substrate as described above, there has been a limit to cost reduction. Therefore, there has been a strong demand for adopting a low-cost substrate using a paper phenol resin or the like which is very inexpensive as compared with a multilayer substrate. However, as shown in FIG. 1 (a), a high-speed digital transmission line is configured with a two-layer substrate, and in this case, the ground plane 130 is separated from the signal layer 110 by about 1.6 mm. However, it is almost a parallel differential line. For this reason, it is necessary to manufacture the substrate with extremely high variations in the pattern width of the copper foil, resulting in unstable characteristics. As a result, there are cases where it cannot be used for a high-speed digital transmission line for high-resolution signals. Therefore, new technology has been demanded.

In view of the above problems, an object of the present invention is to provide a technique for realizing a high-speed digital transmission line capable of stable signal transmission using an inexpensive substrate.

The apparatus according to the present invention relates to a circuit board. The circuit board includes a wiring unit, a conductive member having a conductive layer and grounded to ground, and a ground connection means for connecting the wiring unit and a ground region of the conductive member. A circuit wiring for high-speed digital transmission patterned on one surface of a base substrate, and a dielectric layer having an insulating property formed on the circuit wiring, and the conductive member includes the wiring The unit is fixed so as to face the dielectric layer so as to cover a region where the circuit wiring is formed in the unit.
The base substrate of the wiring unit may be a paper phenol resin or a paper polyethylene resin.
Further, the conductive member may be a wiring board in which a conductive layer is formed on a base substrate made of paper phenol resin or paper polyethylene resin.
Further, the conductive member may have a flexible sheet shape.
The conductive member may have a metal plate.
The conductive member may be a board shield case.
The conductive member may have a chassis structure.
The conductive member may be fixed to the wiring unit by an adhesive means.
Moreover, the said wiring unit does not need to have a conductive layer in the surface opposite to the surface where the said circuit wiring of the said base base material of the said wiring unit was formed.
The total of the thickness of the dielectric layer of the wiring unit and the thickness of the dielectric layer formed on the conductive member may be in the range of 50 to 300 μm.
The ground connection means may include a metal plate-like body that connects the ground region of the wiring unit and the conductive layer of the conductive member.
Moreover, you may provide the fixing means which fixes the said wiring unit and the said electroconductive member in the outer side vicinity of the area | region in which the said circuit wiring is formed.
The wiring unit and the conductive member may be provided with a fixing means for fixing the wiring unit and the conductive member in the vicinity of the outside of the region where the circuit wiring is formed and in the region where the metal plate is provided.

According to the present invention, it is possible to provide a technique for realizing a high-speed digital transmission line capable of stable signal transmission using an inexpensive substrate.

It is the figure which showed the circuit which comprises the micro split line based on a prior art. It is a perspective view of a circuit board concerning this embodiment. It is the figure which showed typically the area | region where the high-speed digital line is mainly formed about the attachment structure of the lower board | substrate based on this embodiment, and an upper board | substrate. It is sectional drawing which showed the attachment structure of the lower board | substrate and upper board | substrate regarding the area | region of A1 of FIG. 3 based on this embodiment. It is sectional drawing which showed the attachment structure of the lower board | substrate, metal plate, and upper board | substrate regarding the area | region of A2 of FIG. 3 based on this embodiment. It is a figure which shows the verification result of an impedance characteristic based on this embodiment.

Next, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
As described above, a high-speed digital transmission line such as HDMI needs to have an appropriate characteristic impedance secured by a stable multilayer substrate. For this reason, it has been impossible to use a single-sided substrate made of a paper phenolic resin base substrate that has been widely used in low-priced models of liquid crystal televisions and the like. In the present embodiment, an electronic device having a high-speed digital transmission line (or “high-speed digital line”) such as an HDMI, LVDS, or DDR (Double-Data-Rate) data line is assumed.

FIG. 2 is a perspective view of the circuit board 10 according to the present embodiment. Further, FIG. 3 shows mainly the high-speed digital line 30 for the mounting structure (side surface) of the lower substrate 20 which is a wiring unit (first substrate) and the upper substrate 40 which is a conductive member (second substrate). It is the figure which showed the area | region currently formed typically. For convenience, the direction in which the high-speed digital line 30 extends in a straight line will be referred to as the front-rear direction, and the direction perpendicular to the straight direction of the high-speed digital line 30 will be described as the left-right direction.

As shown in FIG. 2, an HDMI receiver 90 which is a kind of IC circuit is attached to the surface 20 a of the circuit board 10, and the IC pin 91 is connected to the high-speed digital line 30.

In this embodiment, the circuit board 10 is composed of two substrates, a lower substrate 20 and an upper substrate 40, and the upper substrate 40 is attached so as to cover the high-speed digital line 30 of the lower substrate 20. In FIG. 2, screws 80 that are fixing means for the lower substrate 20 and the upper substrate 40 are omitted. In addition, a metal plate 60 is interposed in the vicinity of the left and right end portions of the upper substrate 40 during the attachment, and the ground planes of the lower substrate 20 and the upper substrate 40 are connected. Detailed structures of the lower substrate 20 and the upper substrate 40 will be described later.

As shown in FIG. 2, eight copper foil high-speed digital lines 30 are formed on the lower substrate 20 in a straight line with a predetermined length in the front-rear direction (upper left to lower right in the figure) by a patterning method or the like. Yes. Here, only the two high-speed digital lines 30 on both sides are denoted by reference numerals. Further, in the following description of the constituent elements, a plurality of the same constituent elements are appropriately denoted by reference numerals and partly omitted.

And, the upper left end portion (HDMI receiver 90 side) end 31 of the high-speed digital line 30 is connected to eight IC pins 91 extending from the HDMI receiver 90, respectively. 2B, in the high-speed digital line 30, the upper substrate 40 is attached to the lower substrate 20 so as to cover a linear portion between the upper left end portion 31 and the lower right end portion 32. It is fixed.

As described above, between the lower substrate 20 and the upper substrate 40, the metal plate 60 is interposed in a predetermined region of the upper substrate 40, and the ground connection portion 50 (see FIG. 3) is formed. Specifically, a rectangular copper plate as the metal plate 60 is disposed on both sides of the upper substrate 40 so as to be sandwiched between the lower substrate 20 and the upper substrate 40. The ground connection unit 50 functions to connect the ground planes of the lower substrate 20 and the upper substrate 40. From this viewpoint, the metal plate 60 can be replaced with any material having good conductivity other than the copper plate, and an anisotropic conductive material, a conductive adhesive, or the like can be used.

As shown in FIG. 3, the lower substrate 20 and the upper substrate 40 are brought into close contact with each other by fixing screw holes 70 (71, 72, 73) penetrating the lower substrate 20 and the upper substrate 40 with screws 80. Specifically, the upper substrate 40 is provided with eight upper substrate screw holes 72. The lower substrate 20 is also provided with eight lower substrate screw holes 71 at positions corresponding to the upper substrate screw holes 72. Here, the four lower substrate screw holes 71 and the upper substrate screw hole 72 in the center in the left-right direction are formed just outside in the vicinity where the high-speed digital line 30 is formed. Further, the four lower board screw holes 71 and the upper board screw holes 72 on both the left and right sides coincide with the screw holes 73 provided in the metal plate 60 disposed therebetween. In addition to screw fixing, various means may be adopted as fixing means as long as an appropriate fixing state such as fixing with an adhesive can be secured.

In this manner, the screw holes 70 (71, 72, 73) are formed and fixed with the screws 80, so that the upper substrate 40 is fixed with the screws 80 in the vicinity of the outer side of the high-speed digital line 30 as much as possible. It has become. As a result, the lower substrate 20 and the upper substrate 40 are in close contact with each other, and the ground plane between the lower substrate 20 and the upper substrate 40 is maintained at a predetermined interval.

FIG. 4 is a cross-sectional view of the mounting structure of the lower substrate 20 and the upper substrate 40 in the area A1 in FIG. 4 shows a state before the lower substrate 20 and the upper substrate 40 are fixed, and FIG. 4B shows a state where the lower substrate 20 and the upper substrate 40 are fixed. Further, FIG. 5 shows a cross-sectional structure of a region A2 in FIG. 3, that is, a portion to which the metal plate 60 is attached.

First, a description will be given with reference to FIG. The paper phenol substrate 21 and the paper phenol substrate 41 which are base materials of the lower substrate 20 and the upper substrate 40 are formed by impregnating a paper base material with a phenol resin.

The lower substrate 20 will be described. On the upper surface of the paper phenol substrate 21 of the lower substrate 20, a wiring structure in which the lower substrate copper foil 22 is patterned in a predetermined region, that is, a high-speed digital line 30 is formed. The pattern width and pattern interval of the high-speed digital line 30 need to be managed appropriately. Specifically, appropriate pattern widths and pattern intervals are set in accordance with the thickness and dielectric constant of a lower substrate resist 23 and an upper substrate resist 43 which will be disposed on the upper side of the high-speed digital line 30. The In particular, it is preferable to consider the thickness and dielectric constant of the lower substrate resist 23 formed immediately above the high-speed digital line 30.

A lower substrate resist 23 is further formed with a predetermined thickness on the high-speed digital line 30. The lower substrate resist 23 is an insulating material having a predetermined stable dielectric constant. A material having a predetermined dielectric constant in the range of about 1 to 5 is preferable. As an alternative to a general resist, polyethylene terephthalate (PET; dielectric constant 2.9 to 3.0) having similar characteristics (insulating properties, dielectric constant, etc.) can also be used.

The thickness of the lower substrate resist 23 is preferably set to 50 to 300 μm when the thickness of the upper substrate resist 43 of the upper substrate 40 described later is added up. The thickness as a single unit is more preferably 25 μm or more. Further, the surface of the lower substrate resist 23 is formed to be a flat surface. However, the portion covering the region where the lower substrate copper foil 22 is removed for patterning the high-speed digital line 30 is formed with a recess.

Next, the upper substrate 40 will be described. The upper substrate 40 has an upper substrate copper foil 42 formed on the lower surface of the paper phenol substrate 41. The upper substrate copper foil 42 functions as a conductive layer for the ground plane. An upper substrate resist 43 is formed in a desired thickness on the surface layer of the upper substrate copper foil 42, that is, below the upper substrate copper foil 42 in the drawing. As described above, the thickness of the upper substrate resist 43 is managed and set together with the thickness of the lower substrate resist 23.

The material of the upper substrate resist 43 is an insulating material having a predetermined stable dielectric constant, like the lower substrate resist 23. Polyethylene terephthalate can also be used. The upper substrate resist 43 may be the same material as the lower substrate resist 23 or may be a different material.

Next, the structure of the portion where the metal plate 60 is provided will be described with reference to FIG. The screw holes 70 (71 to 73) are omitted. As shown, the lower substrate resist 43 of the right end portion of the upper substrate 40 is partially removed, and the upper substrate copper foil 42 is exposed. Similarly, at the position of the lower substrate 20 facing the portion where the upper substrate copper foil 42 is exposed, the lower substrate resist 23 is removed and the lower substrate copper foil 22 is exposed. The exposed lower substrate copper foil 22 is a ground plane of the lower substrate 20. A metal plate 60 is disposed between the exposed portion of the lower substrate copper foil 22 and the exposed portion of the upper substrate copper foil 42, and is fixed with screws 80 as shown in FIG. In order to adopt such a configuration, the thickness of the metal plate 60 is set to be substantially the same as the thickness of the lower substrate resist 23 and the upper substrate resist 43. Thereby, the metal plate 60 is connected and fixed to both the lower substrate copper foil 22 and the upper substrate copper foil 42.

FIG. 6 shows a simulation result of whether or not the HDMI high-speed digital line 30 can be formed. It is shown in comparison with a general two-layer paper phenolic resin substrate (the circuit board 100 in FIG. 1A) and the circuit board 10 of the present embodiment. Since the characteristic impedance of the HDMI high-speed digital line 30 is 100Ω, the pattern width W of the high-speed digital line 30 required to realize the characteristic impedance was calculated. In the present embodiment, as shown in the figure, when the thickness H of the paper phenol substrate 21 having a dielectric constant of 3.8 is 0.08 mm and the resist thickness is 40 μm, the high-speed digital line 30 having a thickness of 0.08 mm When the calculation was performed with the interval S being 0.23 and the impedance being 100Ω, the pattern width W was 0.11 mm, which was a designable range, and it was confirmed that good characteristics were obtained. On the other hand, in the two-layer paper phenolic resin substrate, the pattern width W is 0.9 mm and the HDMI connector pitch is 0.5 mm in the example of the condition shown in the figure, so the calculated value is far from the actual value. ing.

With the above configuration, a microstrip line can be formed by stacking two inexpensive paper phenol substrates, and an appropriate characteristic impedance can be ensured, and a stable high-speed digital line 30 can be provided. Further, the high-speed digital line 30 (high-speed transmission line) can be formed on the same substrate as the circuit conventionally provided on the paper phenol substrate such as a power supply circuit. For this reason, it is possible to mount all circuits conventionally provided on different substrates on the same substrate. As a result, the product cost can be greatly reduced. In addition, management man-hours can be reduced. Moreover, it is easy to change the setting of the upper substrate 40 according to the pattern of the high-speed digital line 30 and the signal to be transmitted, and the replacement is easy. Therefore, the present invention can be applied to various circuits. When the HDMI receiver 90 or the like is changed, it is possible to deal with only the upper substrate 40 without changing the entire circuit substrate 10.

The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of these components, and such modifications are also within the scope of the present invention.

For example, in the above embodiment, a single-sided single layer is used as the lower substrate 20. However, it is also possible to apply to the two-layer substrate shown in FIG. As described above, when a high-speed digital line is formed with a two-layer substrate, it may become unstable. Therefore, by attaching a substrate having the same structure as the upper substrate 40 on the high-speed digital line, stability is improved. be able to. Further, from the viewpoint of using an inexpensive substrate material, a paper polyethylene resin that may be used for a single-sided substrate may be used as a base substrate material instead of the

paper phenol substrates

21 and 41. Further, various materials may be employed for the base substrate. From the viewpoint of the cost of the material itself, paper phenolic resin or paper ethylene resin glass plate is preferable, but from the viewpoint of total procurement cost including the manufacturing process, naturally glass epoxy resin or glass plate may be used. .

Furthermore, in the above-described embodiment, the rigid substrate is exemplified as the lower substrate 20 that is the first substrate and the upper substrate 40 that is the second substrate. However, the present invention is not limited to this. A flexible wiring substrate may be used as the lower substrate 20 and the upper substrate 40. In particular, as the upper substrate 40, a flexible wiring substrate configured in a card shape (sheet shape) may be employed. In that case, the upper substrate 40 may have a seal-like configuration in which an adhesive is applied to a fixed surface with the lower substrate 20 and the coated surface is covered with a protective sheet that can be easily peeled off in the pre-production stage. It is. And at the time of an assembly, the simple manufacturing process of peeling the said protection sheet of the upper board | substrate 40 and making it adhere | attach on the lower board | substrate 20 is realizable.

Further, the lower substrate resist 23 and the upper substrate resist 43 may be a single layer or a plurality of layers made of different materials. Further, the lower substrate resist 23 and the upper substrate resist 43 may be fixed by a predetermined adhesive.

Furthermore, the upper substrate 40 may be integrated with a part of a cabinet or the like of a display device to be mounted. Further, if a microstrip line can be formed and a stable high-speed digital line 30 with an appropriate characteristic impedance can be realized, a substrate using a so-called plate-like substrate such as the lower substrate 20 and the upper substrate 40 can be realized. Need not be. For example, a conductive member using a highly flexible / flexible member such as cloth or paper may be used. In particular, there is room for selection of various materials for the upper substrate 40 in the case of the above-described sealing configuration.

Further, the conductive member is not an independent configuration like the upper substrate 40, and can also be used as a shield plate for various substrates. For example, the function of the shield plate and the function of generating the microstrip line can be realized by forming a shape such that a part of the shield plate is in close contact with the portion where the microstrip line (high-speed digital line 30) is to be generated. At that time, as the shape of the shield plate, a shape in which the shield plate is dented only at a portion where the microstrip line is generated can be considered. The shield plate is usually fixed with screws or the like at the four corners of the substrate, and the ground and shield of the substrate can also be conducted at this portion. Further, since the shield plate and the wiring are more preferably equally spaced, it is necessary to continue applying a certain amount of force to the substrate from the shield plate side. In such a case, it is possible to continue to apply such a force by making the shield plate a springy member.

In addition, the conductive member may have a chassis structure. This is because the chassis structure is normally grounded and can function as a member for generating a micro split line. For example, when fixing a board | substrate to a chassis, the part which produces | generates a micro split may be closely_contact | adhered with a chassis. If there are no parts on the side fixed to the chassis, microsplit can be realized relatively easily. When there is a part, it is possible to deal with it by adding a step to a part of the chassis.

DESCRIPTION OF SYMBOLS 10 Circuit board 20 Lower board 21 Paper phenol board 22 Lower board copper foil 23 Lower board resist 30 High-speed digital line 40 Upper board 41 Paper phenol board 42 Upper board copper foil 43 Upper board resist 60

Metal plate

70, 73 Screw hole 71 Lower board Screw hole 72 Upper substrate screw hole 80 Screw

Claims

A wiring unit, a conductive member having a conductive layer and grounded to ground, and a ground connection means for connecting a ground region of the wiring unit and the conductive member,
The wiring unit is
Circuit wiring for high-speed digital transmission patterned on one side of the base substrate,
A dielectric layer having insulating properties formed on the circuit wiring;
Have
The circuit board, wherein the conductive member is fixed to face the dielectric layer so as to cover a region where the circuit wiring is formed in the wiring unit.
The circuit board according to claim 1, wherein the base substrate of the wiring unit is paper phenol resin or paper polyethylene resin.
The circuit board according to claim 1, wherein the conductive member is a wiring board in which a conductive layer is formed on a base base material made of paper phenol resin or paper polyethylene resin.
The circuit board according to claim 1, wherein the conductive member has a sheet shape having flexibility.
The circuit board according to claim 1, wherein the conductive member includes a metal plate.
The circuit board according to claim 1, wherein the conductive member is a board shielding case.
The circuit board according to claim 1, wherein the conductive member has a chassis structure of a casing.
The circuit board according to claim 1, wherein the conductive member is fixed to the wiring unit by an adhesive unit.
9. The wiring unit according to claim 1, wherein the wiring unit does not have a conductive layer on a surface opposite to the surface on which the circuit wiring of the base substrate of the wiring unit is formed. Circuit board as described.
10. The total thickness of the dielectric layer of the wiring unit and the thickness of the dielectric layer formed on the conductive member is in the range of 50 to 300 μm. Circuit board.
The said ground connection means has a metal plate-shaped body which connects the grounding area | region of the said wiring unit, and the said conductive layer of the said electroconductive member, It is any one of Claim 1 to 10 characterized by the above-mentioned. Circuit board.
The circuit board according to claim 1, further comprising a fixing unit that fixes the wiring unit and the conductive member in the vicinity of an outside of a region where the circuit wiring is formed.
The circuit board according to claim 12, wherein the fixing means fixes the wiring unit and the conductive member in a region where a metal plate-like body is provided.