JP5146267B2 - Manufacturing method of wiring board and printed wiring board - Google Patents

Description

  The present invention relates to a wiring board applied as a flexible cable such as a printed wiring board (Flexible Printed Circuit: FPC) or FFC (Flexible Flat Cable), and a method for manufacturing the printed wiring board.

  In order to connect between modules mounted on recent electronic devices, an FPC that is a flat flexible cable or the like is used. A wiring board applied as such a flexible cable is required to have functions such as characteristic impedance matching, improvement of high-speed and high-frequency characteristics, and reduction of unnecessary radiation as the transmission signal speed increases. In addition, the wiring board has a stripline or microstripline structure, and the increase in the number of signal lines has led to the development of multilayer boards.

  For example, in order to improve high-speed and high-frequency characteristics and reduce unnecessary radiation, Patent Document 1 forms guard traces that sandwich each high-speed transmission path on a common shared plane on which a plurality of high-speed transmission paths are arranged. A printed circuit board is described in which the first and second ground layers connected to the guard traces through the through holes are covered with a plurality of high-speed transmission lines so that each high-speed transmission line is three-dimensionally shielded.

JP 2007-234500 A

  In a microstrip line structure wiring board with guard traces, in order to prevent the transmission mode of each signal line from interfering with the potential difference between the guard trace and the ground layer, the plated metal or conductive material usually formed in the through hole Connect both with paste. These through holes are provided at a sufficiently small interval with respect to the wavelength of the signal to be transmitted. For example, when signal transmission is performed in the GHz band, many through holes are formed in the guard trace along the transmission direction of the signal line. Therefore, the layout design of the wiring is restricted, and the number of process steps for manufacturing the substrate is increased.

  The present invention has been proposed in view of such circumstances, and can reduce the number of process steps in layout design and substrate fabrication, and can transmit signals without sacrificing electromagnetic transmission characteristics. It is an object of the present invention to provide a possible wiring board and a method for manufacturing a printed wiring board.

As means for solving the above-described problems, a wiring board according to the present invention includes a plurality of signal lines for transmitting signals and a conductor formed in the transmission direction between the signal lines, and is transmitted by the signal lines. A guard trace that suppresses interference of each signal, a dielectric on which one of a plurality of signal lines and a guard trace is stacked, and a dielectric that sandwiches the dielectric, and is disposed at a position facing the plurality of signal lines, A ground layer for signals transmitted through a plurality of signal lines, and an insulating cover layer that covers the plurality of signal lines and guard traces stacked on the surface of the dielectric so that the film thickness satisfies the following formula: With.
(Ε2 / (ε1-1)) × t2 <t1 <(ε2 / (ε1-1)) × t2 × 2
t1 is the thickness of the coverlay, t2 is the thickness of the dielectric, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the dielectric, and satisfies ε2−ε1 ≦ 0.3.

The wiring board according to the present invention includes a plurality of signal lines that differentially transmit signals through a pair of transmission lines, and a conductor formed in a transmission direction between the signal lines, and each signal transmitted through the signal lines. A guard trace that suppresses interference, a dielectric that stacks a plurality of signal lines and guard traces on one surface, and a plurality of signals that are disposed at positions facing the plurality of signal lines across the dielectric. A ground layer for a signal transmitted by the line, and an insulating coverlay covering the plurality of signal lines and the guard traces stacked on the surface of the dielectric so that the film thickness satisfies the following formula: .
(Ε2 / ε1) × t2 <t1 <(ε2 / ε1) × t2 × 3
t1 is the thickness of the coverlay, t2 is the thickness of the dielectric, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the dielectric, and satisfies ε2−ε1 ≦ 0.3.

The printed wiring board manufacturing method according to the present invention includes a guard trace that forms a plurality of signal lines for transmitting signals on one surface of a base film and suppresses interference of signals transmitted by the signal lines. Is formed in the transmission direction between the signal lines, on the other surface of the base film is formed a ground layer for signals transmitted by the plurality of signal lines, and the insulation satisfies the following formula: Covering a plurality of signal lines and guard traces formed on the surface of the base film with the coverlay.
(Ε2 / (ε1-1)) × t2 <t1 <(ε2 / (ε1-1)) × t2 × 2
t1 is the thickness of the coverlay, t2 is the thickness of the base film, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the base film, and satisfies ε2−ε1 ≦ 0.3.

The printed wiring board manufacturing method according to the present invention includes forming a plurality of signal lines for differential transmission of signals through a pair of transmission paths on one surface of the base film, and transmitting each of the signal lines. Forming a guard trace for suppressing signal interference in the transmission direction between the signal lines, forming a ground layer for signals transmitted by the plurality of signal lines on the other surface of the base film, and film thickness; Covering a plurality of signal lines and guard traces formed on the surface of the base film with an insulating coverlay satisfying the following formula.
(Ε2 / ε1) × t2 <t1 <(ε2 / ε1) × t2 × 3
t1 is the thickness of the coverlay, t2 is the thickness of the base film, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the base film, and satisfies ε2−ε1 ≦ 0.3.

  In the present invention, the guard trace and the ground layer are connected by adjusting the film thickness of the cover lay, the film thickness of the dielectric, and the dielectric constant so that the dielectric constant around the signal line is uniform. Since no through-hole is provided, it is possible to transmit a signal without sacrificing electromagnetic transmission characteristics by suppressing restrictions on layout design and process man-hours in substrate fabrication.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention.

  The present invention relates to a wiring board applied as a flexible cable such as a printed wiring board (Flexible Printed Circuit: FPC) or FFC (Flexible Flat Cable).

  First, prior to description of a configuration related to a wiring board to which the present invention is applied, a wiring board having a microstrip line structure provided with a guard trace, which has been conventionally used, will be described with reference to FIGS.

  FIG. 1 is a cross-sectional view of a wiring board 100 having a microstrip line structure conventionally used. In the wiring board 100, the signal line 101 and the ground layer 103 face each other with the dielectric 104 interposed therebetween, and electromagnetic waves are mainly transmitted between them. Usually, a coverlay 105 is overcoated to protect the signal line 101.

  FIG. 2 is a cross-sectional view of a transmission line having a structure in which guard traces 112 are provided on both sides of a signal line 111 of a wiring board 110 having a microstrip line structure. In the wiring board 110, the guard trace 112 is provided, and compared with the wiring board 100, there are effects such as reduction of crosstalk between adjacent signal lines 111 and 111 and suppression of a radiated electromagnetic field. Yes.

  In the wiring board 110, in order to avoid the transmission mode of each signal line 111 from being interfered by the potential difference between the guard trace 112 and the ground layer 113, the both are usually connected with a plated metal, a conductive paste, or the like formed in the through hole 116. Connecting. The through holes 116 are provided at a sufficiently small interval with respect to the wavelength of the transmitted signal.

  FIG. 3 shows an analysis result obtained by analyzing the electric field distribution in the cross section of the transmission line composed of the signal line 121, the guard trace 122, and the ground layer 123 using the analysis model 120 of the three-dimensional electromagnetic field simulator equivalent to the wiring board 110. is there. As shown in FIG. 3, the electric field strength is higher in the region A1 near the signal line 121, and the electric field strength decreases as the distance from the signal line 121 increases according to the regions A2, A3, A4, A5, and A6.

  As is clear from the analysis result shown in FIG. 3, in the wiring board 110 shown in FIG. 2, which is equivalent to the analysis model 120, the electric field is strongly distributed in the dielectric 114 between the signal line 111 and the ground layer 113. However, it is also widely distributed in the coverlay 115 and the space above it. Due to the distribution of the electric field, there are two lines of metal that serve as a return path for the signal line 111, the ground layer 113 and the guard trace 112, and transmission between the signal line 111 and each return path is added. Become. At this time, if the effective dielectric constants of the two systems are different, the effective transmission speed is different and interference occurs between the transmission modes of the signal lines 111, and the signal lines 111 and the ground layer 113 are transmitted. Periodic disturbances occur in the frequency characteristics of the electric field strength. This periodic disturbance causes an increase in electromagnetic radiation. In order to suppress such interference between the transmission modes of the signal lines 111, the wiring board 110 is electrically connected between the ground layer 113 and the guard trace 112 through the through holes 116 at regular intervals. The potential between 113 and the guard trace 112 is made equal.

  On the other hand, the wiring board to which the present invention is applied has substantially the same effective dielectric constant in the two systems described above without performing electrical connection through a through hole, and the transmission mode of each signal line. Specifically, the following configuration is used in order to suppress interfering interference.

<First Embodiment>
FIG. 4 is a diagram showing the wiring board 1 according to the first embodiment to which the present invention is applied. That is, the wiring board 1 includes a plurality of signal lines 11 for transmitting signals and a guard trace 12 made of a conductor formed in the transmission direction between the signal lines 11 as shown in FIG. Further, the wiring substrate 1 has a dielectric layer 14 in which the signal line 11 and the guard trace 12 are stacked on one surface 14a, and a ground layer disposed at a position facing the signal line 11 with the dielectric layer 14 interposed therebetween. 13 and an insulating coverlay 15 that covers the signal line 11 and the guard trace 12 stacked on the surface 14 a of the dielectric 14.

  Further, in the wiring board 1, in order to make the dielectric constant around the signal line 11 uniform without providing a through hole, the cover lay 15 and the dielectric 14 are adjusted and formed so as to satisfy the following expression (1). Has been.

  (Ε2 / (ε1-1)) × t2 <t1 <(ε2 / (ε1-1)) × t2 × 2 (1)

  Here, t1 is the film thickness of the cover lay 15, t2 is the film thickness of the dielectric 14, ε1 is the dielectric constant of the cover lay 15, ε2 is the dielectric constant of the dielectric 14, and ε2−ε1. ≦ 0.3 is satisfied.

  The dielectric 14 preferably has a small dielectric constant and dielectric loss tangent from the viewpoint of transmission characteristics. For example, a film-shaped polyimide, a liquid crystal polymer, or the like is used.

  On the other hand, the coverlay 15 is an insulating substance used to protect the signal line 11 and the like, and preferably has a low dielectric loss tangent from the viewpoint of transmission characteristics, and is a film-like, curable ink, or solder resistor. A photosensitive solder register is used. In general, since the material used for the coverlay has a large dielectric loss, it is better to use a material as thin as possible in order to suppress the loss of the transmission line. Also, it is better to be thin from the viewpoint of not hindering flexibility. The upper limit of the film thickness of the cover lay adjusted according to the above equation (1) is set in consideration of these effects.

  The dielectric 14 and the cover lay 15 may be adjusted so as to satisfy the above expression (1). However, in the wiring board 1, the dielectric constant of the dielectric 14 is usually adjusted according to the condition of ε2−ε1 ≦ 0.3. It is assumed that the cover lay 15 has a high dielectric constant. In this case, the wiring board 1 is formed according to the above equation (1), so that the film thickness of the coverlay 15 is adjusted to be smaller than the film thickness of the dielectric 14.

  The wiring board 1 having the above configuration is formed, for example, according to the following process. First, one of the copper foil surfaces of the substrate in which a good conductor such as copper foil is coated on both surfaces of the base film used as the dielectric 14 is etched to form the signal lines 11 and the guard traces 12. Subsequently, a coverlay 15 having a predetermined film thickness according to the above equation (1) is attached to the base film (dielectric 14) on the side where the signal line 11 is formed, and thermocompression bonded.

  The signal line 11 and the guard trace 12 are formed on one surface of the base film and the ground layer 13 is formed on the other surface by a patterning process using a good conductor such as copper, without being limited to the etching process described above. May be formed.

  In this way, the wiring board 1 has almost the same layer structure as the wiring board 110 shown in FIG. 2 described above, but is not provided with a through hole for electrically connecting the guard trace 12 and the ground layer 13. Therefore, it is possible to improve the degree of freedom in wiring design and to omit process steps.

  Next, the transmission characteristics of the wiring board 1 are analyzed using a three-dimensional electromagnetic field simulator. In this simulation, the width and film thickness of the signal line 11 are 42 μm and 10 μm, respectively, and the pitch interval between the signal lines 11 and 11 is 500 μm. The guard traces 12 are provided between the signal lines 11 with an interval of 60 μm. The dielectric 24 has a dielectric constant and a film thickness of 3.2 and 25 μm, respectively. In the analysis model, the length of the wiring board 1 is 20 mm.

  FIG. 5 is a diagram showing the transmission characteristics S21 when the cover layer 15 has a dielectric constant of 5 and the cover layer 15 has a thickness of 15 μm, 25 μm, and 37 μm. Here, “S21” means a ratio of output to input with a transmission coefficient expressed using an S matrix used for expressing characteristics of a multi-aperture circuit, and is logarithmically displayed.

  When the film thickness of the cover lay 15 is 15 μm, the above expression (1) is not satisfied, but when the film thickness of the cover lay 15 is 25 μm and 37 μm, the condition of the above expression (1) is satisfied. Here, in FIG. 5, the characteristic curve is shifted by 1 dB in the vertical direction in order to facilitate comparison of the transmission characteristics. As shown in FIG. 5, when the thickness of the cover lay 15 is 15 μm, the transmission characteristics are disturbed at a specific frequency. However, when the cover lay 15 is 25 μm thick, such transmission characteristics are not disturbed (1 ) Disturbance is reduced even at 37 μm, which is close to the upper limit of the equation. In particular, when the film thickness of the cover lay 15 is 25 μm, the effective dielectric constant of the transmission line is 3.3. Therefore, the dielectric constant is approximately the same as the dielectric constant 3.2 of the dielectric 14, The dielectric constant is made uniform, and communication characteristics can be maintained without providing a through hole.

  In addition, the wiring board 1 described above has a dielectric constant of the coverlay 15 higher than that of the dielectric 14, but when the dielectric constant of the coverlay is lower than that of the dielectric, the above ( It is difficult to make the dielectric constant uniform according to the equation (1) from the above condition of ε2−ε1 ≦ 0.3.

  FIG. 6 is a diagram showing a configuration of a wiring board 2 formed under the condition that the dielectric constant of the coverlay is lower than the dielectric constant of the dielectric as a modification of the wiring board 1. Similar to the wiring substrate 1, the wiring substrate 2 includes a plurality of signal lines 21, a guard trace 22, a dielectric 24, a ground layer 23, and a cover lay 25. Since the dielectric constant of the cover lay 25 is lower than the dielectric constant of the dielectric 24, the wiring substrate 2 is formed according to the above formula (1), so that the film thickness of the cover lay 25 becomes the film thickness of the dielectric 24. It is adjusted to be thicker than

  Next, the transmission characteristics of the wiring board 2 are analyzed using a three-dimensional electromagnetic field simulator. In this simulation, the width and film thickness of the signal line 21 are 42 μm and 10 μm, respectively, and the pitch interval between the signal lines 21 and 21 is 500 μm. The guard traces 22 are provided between the signal lines 21 with an interval of 60 μm. The dielectric 24 has a dielectric constant and a film thickness of 3.2 and 25 μm, respectively. The length of the wiring board 1 of the analysis model is 20 mm.

  FIG. 7 shows the transmission characteristics S21 when the dielectric constant of the coverlay 25 that does not satisfy the condition of ε2-ε1 ≦ 0.3 is 2.5 and the film thickness of the coverlay 25 is changed to 25 μm, 50 μm, and 150 μm. FIG. In FIG. 7, the characteristic curves are shifted by 1 dB in the vertical direction in order to facilitate comparison of the transmission characteristics. As shown in FIG. 7, as the thickness of the cover lay 25 is increased, the transmission characteristics are disturbed at a specific frequency, and an improvement trend is observed. Here, if the dielectric constant of the cover lay 25 is too smaller than the dielectric constant of the dielectric 24, the effective dielectric constant cannot be made close to the dielectric constant of the dielectric 24 even if the cover lay 25 is thick. ) Even if the equation is satisfied, the disturbance of transmission characteristics cannot be sufficiently suppressed. As is clear from the analysis result, the dielectric constant of the cover lay 25 is selected so as not to be lower than 0.3 relative to the dielectric constant of the dielectric 24, that is, to satisfy ε2−ε1 ≦ 0.3. There is a need.

  As described above, in the wiring substrate 1 according to the first embodiment, the coverlay film thickness, the dielectric film thickness, and the dielectric film thickness are determined according to the above equation (1) so that the dielectric constant around the signal line is uniform. By adjusting these dielectric constants, there are no through-holes connecting the guard trace and the ground layer, so restrictions on layout design and process man-hours in substrate fabrication are reduced, and electromagnetic transmission characteristics are sacrificed. It is possible to transmit a signal without making it.

  Further, FIG. 8 shows a comparison of the electric field strength at a distance of 3 m in order to examine the influence on the electromagnetic field radiation. The model compared is “2.5 mm pitch connection”, which is a wiring board in which the connection between the coverlay and the ground layer is made only 1.5 mm away from the terminal part, and the other parts are connected by through holes at a pitch of 2.5 mm. The other “no connection” is to adjust the cover lay and dielectric according to the equation (1), and connect the cover lay and ground layer only 1.5 mm away from the terminal part and connect the other parts. There is no wiring board. Normally, when periodic ripples in the transmission characteristic S21 as shown in FIGS. 5 and 7 occur due to signal interference, the electric field strength at that frequency becomes strong. However, as shown in FIG. In the wiring board of 3mm, there is no difference in the radiated electric field strength at a distance of 3m, and the electromagnetic interference noise that increases due to the disturbance of the equivalent characteristics at a specific frequency is reduced by the "2.5mm pitch connection" with through holes. It can be reduced to the same extent as the wiring board.

  It should be noted that the connection between the coverlay and the ground layer is made only 1.5 mm away from the terminal part, but the electrical connection between a plurality of ground traces can be omitted completely. This is because it is desirable to use a system that does not allow long open stubs.

  As is apparent from the results of FIG. 8, in the wiring board 1 according to the first embodiment, similar to the microstrip line structure wiring board provided with the through hole, the equivalent characteristic is disturbed at a specific frequency. The electromagnetic field radiation that increases due to this can be suppressed.

<Second Embodiment>
FIG. 9 is a diagram showing a wiring board 3 according to the second embodiment to which the present invention is applied. That is, as shown in FIG. 9, the wiring substrate 3 includes a plurality of signal lines 31 that differentially transmit signals through a pair of transmission paths, and a guard trace 32 that is formed of a conductor formed in the transmission direction between the signal lines 31. With. In addition, the wiring board 3 has a dielectric 34 on which the signal line 31 and the guard trace 32 are stacked on one surface 34a, and a ground layer disposed at a position facing the signal line 31 with the dielectric 34 interposed therebetween. 33 and an insulating coverlay 35 that covers the signal line 31 and the guard trace 32 stacked on the surface 34 a of the dielectric 34.

  Further, in the wiring board 3, the electromagnetic coupling between the adjacent signal lines 31, 31 is stronger than that of the wiring board 1 according to the first embodiment described above. Therefore, in the wiring substrate 3, in consideration of such electromagnetic coupling, in order to make the dielectric constant around the signal line 31 uniform without providing a through hole, the cover layer is satisfied so as to satisfy the following expression (2). 35 and the dielectric 34 are adjusted.

  (Ε2 / ε1) × t2 <t1 <(ε2 / ε1) × t2 × 3 (2)

  Here, t1 is the thickness of the cover lay, t2 is the thickness of the dielectric, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the dielectric, and ε2−ε1 ≦ 0.3. Meet.

  In general, the material used for the coverlay has a large dielectric loss, so it is better to use a material that is as thin as possible in order to suppress the loss of the transmission line. Also, it is better to be thin from the viewpoint of not hindering flexibility.

  The dielectric 34 preferably has a low dielectric constant and dielectric loss tangent from the viewpoint of transmission characteristics. For example, polyimide or liquid crystal polymer is used.

  On the other hand, the coverlay 35 is an insulating material used for protecting the signal line 31 and the like, and preferably has a low dielectric loss tangent from the viewpoint of transmission characteristics, and is a film-like, curable ink, solder resistor. A photosensitive solder register is used. In general, since the material used for the coverlay has a large dielectric loss, it is better to use a material as thin as possible in order to suppress the loss of the transmission line. Also, it is better to be thin from the viewpoint of not hindering flexibility. The upper limit of the film thickness of the cover lay adjusted according to the above equation (2) can be set in consideration of these effects.

  The dielectric 34 and the coverlay 35 may be adjusted so as to satisfy the above expression (2). However, the wiring board 3 covers the dielectric constant of the dielectric 34 according to the condition of ε2−ε1 ≦ 0.3. It is assumed that the dielectric constant of the ray 35 is high. In this case, the wiring board 3 is formed according to the above equation (2), so that the film thickness of the cover lay 35 is adjusted to be smaller than the film thickness of the dielectric 34.

  The wiring board 3 configured as described above has a signal line 31 and a guard trace 32 formed on one surface of the base film by patterning using a good conductor such as copper, like the wiring board 1. The ground layer 33 is formed on the other surface.

  Thus, since the wiring board 3 is not provided with a through hole for electrically connecting the guard trace and the ground layer like the wiring board 1 described above, the degree of freedom in wiring design is improved and the process steps are omitted. Can be achieved.

  Next, the transmission characteristics of the wiring board 3 are analyzed using a three-dimensional electromagnetic field simulator. In this simulation, the width and thickness of each transmission line of the signal line 31 are 42 μm and 10 μm, respectively, and the width and thickness of the guard trace 32 are 440 μm and 10 μm, respectively. Further, the interval between the transmission lines constituting the signal line 31 and the interval between the signal line 31 and the guard trace 32 are 80 μm and 60 μm, respectively. The dielectric constant and thickness of the dielectric 34 are 3.2 and 25 μm, respectively, and the length of the wiring board 3 of the analysis model is 20 mm.

  FIG. 10 is a diagram showing the differential transmission characteristics S21 when the dielectric constant of the coverlay 35 is 3.3 and the thickness thereof is changed to 12 μm, 37 μm, and 100 μm. When the film thickness of the cover lay 35 is 12 μm and 100 μm, the above expression (2) is not satisfied, but when the film thickness of the cover lay 35 is 37 μm, the condition of the above expression (2) is satisfied. In FIG. 10, the characteristic curve is shifted by 1 dB in the vertical direction for easy comparison. As shown in FIG. 10, when the thickness of the coverlay 35 is 12 μm and 100 μm, the transmission characteristics are disturbed at a specific frequency, and there is a concern about the influence of electromagnetic field radiation. On the other hand, such a phenomenon is not observed when the thickness of the cover lay is 37 μm appropriately adjusted in accordance with the above equation (2).

  As described above, the wiring board 3 according to the second embodiment has the coverlay film thickness, the dielectric film thickness, and the dielectric film thickness according to the above equation (2) so that the dielectric constant around the signal line is uniform. By adjusting these dielectric constants, the dielectric constant around the signal line 31 can be made uniform, and communication characteristics can be maintained without providing a through hole. Therefore, since the wiring board 3 does not have a through hole for connecting the guard trace and the ground layer, it is possible to suppress restrictions related to layout design and process man-hours in board production without sacrificing electromagnetic transmission characteristics. A signal can be transmitted.

It is sectional drawing of the wiring board of the microstrip line structure conventionally used. It is a transmission line sectional view of a structure in which guard traces are provided on both sides of a signal line of a wiring board having a microstrip line structure. It is the analysis result which analyzed the electric field distribution in the transmission line cross section of FIG. 2 with the three-dimensional electromagnetic field simulator. It is a figure which shows the wiring board which concerns on 1st Embodiment to which this invention was applied. It is a figure which shows the permeation | transmission characteristic S21 according to the change of the film thickness of a coverlay. As a modification of the first embodiment, it is a diagram showing a configuration of a wiring board formed under the condition that the dielectric constant of the coverlay is lower than the dielectric constant of the dielectric. It is a figure which shows the permeation | transmission characteristic S21 according to the change of the film thickness of a coverlay. It is a figure which shows the comparison of the electric field strength in the distance of 3 m by "2.5 mm pitch connection" and "no connection". It is a figure which shows the wiring board which concerns on 2nd Embodiment to which this invention was applied. It is a figure which shows the differential transmission characteristic S21 according to the change of the film thickness of a coverlay.

Explanation of symbols

  1, 2, 3, 100, 110 Wiring board, 11, 21, 31, 101, 111, 121 Signal line, 12, 22, 32, 112, 122 Guard trace, 13, 23, 33, 103, 113, 123 Ground Layer, 14, 24, 34, 104, 114 Dielectric, 14a, 24a, 34a Surface, 15, 25, 35, 105, 115 Coverlay, 116 Through hole

Claims (4)

A plurality of signal lines for transmitting signals;
A guard trace made of a conductor formed in the transmission direction between the signal lines, and suppressing interference of each signal transmitted by the signal lines;
On one surface, a dielectric that laminates the plurality of signal lines and the guard traces,
A ground layer for signals transmitted by the plurality of signal lines, disposed at a position facing the plurality of signal lines with the dielectric interposed therebetween,
A wiring board comprising an insulating coverlay that covers the plurality of signal lines and the guard traces stacked on the surface of the dielectric so that the film thickness satisfies the following formula.
(Ε2 / (ε1-1)) × t2 <t1 <(ε2 / (ε1-1)) × t2 × 2
t1 is the film thickness of the coverlay, t2 is the film thickness of the dielectric, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the dielectric, and ε2−ε1 ≦ 0. Satisfy 3 A plurality of signal lines for differential transmission of signals through a pair of transmission paths;
A guard trace made of a conductor formed in the transmission direction between the signal lines, and suppressing interference of each signal transmitted by the signal lines;
On one surface, a dielectric that laminates the plurality of signal lines and the guard traces,
A ground layer for signals transmitted by the plurality of signal lines, disposed at a position facing the plurality of signal lines with the dielectric interposed therebetween,
A wiring board comprising an insulating coverlay that covers the plurality of signal lines and the guard traces stacked on the surface of the dielectric so that the film thickness satisfies the following formula.
(Ε2 / ε1) × t2 <t1 <(ε2 / ε1) × t2 × 3
t1 is the film thickness of the coverlay, t2 is the film thickness of the dielectric, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the dielectric, and ε2−ε1 ≦ 0. Satisfy 3 A plurality of signal lines for transmitting signals are formed on one surface of the base film, and guard traces for suppressing interference of signals transmitted by the signal lines are formed in the transmission direction between the signal lines. Steps,
Forming a ground layer for signals transmitted by the plurality of signal lines on the other surface of the base film;
A method of manufacturing a printed wiring board, comprising: covering the plurality of signal lines and the guard traces formed on the surface of the base film with an insulating cover lay having a film thickness satisfying the following formula.
(Ε2 / (ε1-1)) × t2 <t1 <(ε2 / (ε1-1)) × t2 × 2
t1 is the thickness of the coverlay, t2 is the thickness of the base film, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the base film, and ε2−ε1 ≦ 0. Satisfy 3 On one surface of the base film, a plurality of signal lines for differentially transmitting signals by a pair of transmission lines are formed, and guard traces that suppress interference of each signal transmitted by the signal lines are provided between the signal lines. Forming in the above transmission direction;
Forming a ground layer for signals transmitted by the plurality of signal lines on the other surface of the base film;
A method of manufacturing a printed wiring board, comprising: covering the plurality of signal lines and the guard traces formed on the surface of the base film with an insulating cover lay having a film thickness satisfying the following formula.
(Ε2 / ε1) × t2 <t1 <(ε2 / ε1) × t2 × 3
t1 is the thickness of the coverlay, t2 is the thickness of the base film, ε1 is the dielectric constant of the coverlay, ε2 is the dielectric constant of the base film, and ε2−ε1 ≦ 0. Satisfy 3

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