JP5091720B2 - Printed circuit board - Google Patents

Description

  The present invention relates to a printed circuit board.

  An actuator is used in a drive device such as a hard disk drive device. Such an actuator includes an arm rotatably provided on a rotating shaft, and a suspension board for a magnetic head attached to the arm. The suspension board is a printed circuit board for positioning the magnetic head on a desired track of the magnetic disk.

  FIG. 5 is a longitudinal sectional view showing an example of a conventional suspension board. In the suspension substrate 900 of FIG. 5, an insulating layer 903 is formed on a metal substrate 902. On the insulating layer 903, a pair of write conductors W1, W2 and a pair of read conductors R1, R2 are formed in order.

  One end of each of the conductors W1, W2, R1, and R2 is connected to a magnetic head (not shown). The other ends of the conductors W1, W2, R1, and R2 are electrically connected to an electric circuit for writing and reading (not shown), respectively.

  In the suspension board 900, when a write current flows through the write conductors W1 and W2, an induced electromotive force is generated in the read conductors R1 and R2 by electromagnetic induction.

  Here, the distance between the write conductors W1, W2 and the read conductor R1 is smaller than the distance between the write conductors W1, W2 and the read conductor R2. As a result, a difference occurs in the induced electromotive force generated in the reading conductors R1 and R2. As a result, a current flows through the reading conductors R1 and R2. That is, crosstalk occurs between the write conductors W1 and W2 and the read conductors R1 and R2.

  Therefore, Patent Document 1 proposes a printed circuit board shown in FIG. 6 in order to prevent the occurrence of crosstalk between the write conductors W1, W2 and the read conductors R1, R2.

  FIG. 6 is a longitudinal sectional view showing another example of a conventional suspension board. In the suspension substrate 910, a first insulating layer 904 is formed on a metal substrate 902. On the first insulating layer 904, a writing conductor W2 and a reading conductor R2 are formed so as to be separated from each other by a distance L1.

  On the first insulating layer 904, a second insulating layer 905 is formed so as to cover the writing conductor W2 and the reading conductor R2. On the second insulating layer 905, a writing conductor W1 is formed above the reading conductor R2, and a reading conductor R1 is formed above the writing conductor W2.

  The distance between the reading conductor R1 positioned above and below and the writing conductor W2 and the distance between the reading conductor R2 positioned above and below and the writing conductor W1 are both L2.

In the suspension board 910 of FIG. 6 having the above configuration, the distance between the write conductors W1, W2 and the read conductor R1 is the distance between the write conductors W1, W2 and the read conductor R2. Each is almost equal. Thereby, when a write current flows through the write conductors W1 and W2, it is considered that the magnitudes of the induced electromotive forces generated in the read conductors R1 and R2 are substantially equal.
JP 2004-133888 A

  Incidentally, in the suspension boards 900 and 910 shown in FIGS. 5 and 6, the impedances of the conductors W1, W2, R1, and R2 are the magnitudes of the coupling capacitances between the conductors W1, W2, R1, and R2 and the metal board 902. It depends on.

  Here, in the suspension board 910 of FIG. 6, the distance between the writing conductor W1 and the metal board 902 is different from the distance between the writing conductor W2 and the metal board 902. Further, the distance between the reading conductor R1 and the metal substrate 902 is different from the distance between the reading conductor R2 and the metal substrate 902.

  In this case, the coupling capacitance between the writing conductor W1 and the metal substrate 902 is different from the coupling capacitance between the writing conductor W2 and the metal substrate 902. Further, the coupling capacitance between the reading conductor R1 and the metal substrate 902 is different from the coupling capacitance between the reading conductor R2 and the metal substrate 902.

  Therefore, in the configuration of the suspension board 910, there is a difference in impedance between the writing conductor W1 and the writing conductor W2, and there is a difference in impedance between the reading conductor R1 and the reading conductor R2. This may cause a differential signal transmission error due to the write conductors W1 and W2 and a differential signal transmission error due to the read conductors R1 and R2.

  An object of the present invention is to provide a printed circuit board that can sufficiently prevent occurrence of signal transmission errors.

(1) A wired circuit board according to the present invention includes a conductive substrate, a first insulating layer formed on the conductive substrate, a first wiring pattern formed on the first insulating layer, A second insulating layer formed on the first insulating layer so as to cover one wiring pattern, a second wiring pattern formed on the second insulating layer, and a second wiring pattern so as to cover the second wiring pattern And a third insulating layer formed on the second insulating layer, wherein the first wiring pattern and the second wiring pattern are disposed so as to face each other with the second insulating layer interposed therebetween . the dielectric constant of the third insulating layer is higher than the dielectric constant of the dielectric constant of the first insulating layer and the second insulating layer, first and second wiring patterns constitute a first signal line pair The capacitance of the first wiring pattern with respect to the conductive substrate is substantially equal to the capacitance of the second wiring pattern with respect to the conductive substrate. The dielectric constant of the first to third insulating layer is intended to be set respectively for Kunar.

In this wired circuit board, a first insulating layer is formed on a conductive substrate, and a first wiring pattern is formed on the first insulating layer. In addition, a second insulating layer is formed on the first insulating layer so as to cover the first wiring pattern, and a second wiring pattern is formed on the second insulating layer. Then, a third insulating layer is formed on the second insulating layer so as to cover the second wiring pattern. The relative dielectric constant of the third insulating layer is set higher than the relative dielectric constants of the first and second insulating layers. In such a configuration, the first signal line pair is constituted by the first and second wiring patterns, and the capacitance of the first wiring pattern with respect to the conductive substrate and the second wiring pattern with respect to the conductive substrate. The relative dielectric constants of the first to third insulating layers are set so that the capacitance is substantially equal.

  In the configuration as described above, when a potential is applied to the second wiring pattern, it is between the lower surface of the second wiring pattern and the conductive substrate, between the side surface of the second wiring pattern and the conductive substrate, and An electric field is formed between the upper surface of the wiring pattern 2 and the conductive substrate.

  Therefore, the capacitance of the second wiring pattern with respect to the conductive substrate is equal to the thickness and relative dielectric constant of the first and second insulating layers existing between the lower surface of the second wiring pattern and the conductive substrate. Rather, it is given based on factors including the dielectric constant of the third insulating layer.

  On the other hand, when a potential is applied to the first wiring pattern, between the lower surface of the first wiring pattern and the conductive substrate, between the side surface of the first wiring pattern and the conductive substrate, and between the first wiring pattern and the conductive substrate. An electric field is formed between the upper surface and the conductive substrate.

  Accordingly, the capacitance of the first wiring pattern with respect to the conductive substrate is given based on factors including not only the thickness and relative dielectric constant of the first insulating layer but also the relative dielectric constant of the second insulating layer. .

  Here, the relative dielectric constant of the third insulating layer is higher than that of the first and second insulating layers 41 and 42. Therefore, even if the distance between the conductive substrate and the second wiring pattern is shorter than the distance between the conductive substrate and the first wiring pattern, the electrostatic capacitance of the second wiring pattern with respect to the conductive substrate. The capacitance can be set to a value equivalent to the capacitance of the first wiring pattern with respect to the conductive substrate.

The relative dielectric constants of the first to third insulating layers are set so that the capacitance of the first wiring pattern with respect to the conductive substrate is substantially equal to the capacitance of the second wiring pattern with respect to the conductive substrate. Is set. Thereby, when signals are transmitted by the first and second wiring patterns, the impedance of the first wiring pattern and the impedance of the second wiring pattern can be reliably set to the same value. Thereby, it is possible to sufficiently prevent a signal transmission error from occurring due to the unbalance of the first signal line pair.

(2) The first wiring pattern and the second wiring pattern have the same width and may be arranged at the same position in the width direction .

  In this case, the capacitance of the first wiring pattern for the conductive substrate and the capacitance of the second wiring pattern for the conductive substrate can be easily set to the same value. Therefore, the impedance of the first wiring pattern and the impedance of the second wiring pattern can be easily set to the same value.

( 3 ) The relative dielectric constants of the first to third insulating layers may be set so that the impedance of the first wiring pattern is substantially equal to the impedance of the second wiring pattern.

  In this case, it is possible to reliably prevent a signal transmission error from occurring due to the unbalance of the first signal line pair.

( 4 ) The third insulating layer may be formed of a resin containing a high dielectric constant material.

  In this case, the relative dielectric constant of the third insulating layer can be easily made higher than the relative dielectric constants of the first and second insulating layers by adjusting the addition amount of the high dielectric constant material. As a result, the printed circuit board can be easily manufactured.

( 5 ) The high dielectric constant material may include barium titanate. In this case, by using barium titanate, the relative dielectric constant of the third insulating layer can be easily made higher than that of the first and second insulating layers.

( 6 ) The printed circuit board includes a third wiring pattern formed on the first insulating layer spaced from the first wiring pattern, and a second insulating layer spaced from the second wiring pattern. And a fourth wiring pattern formed thereon, and the third and fourth wiring patterns may constitute a second signal line pair.

  In this case, signals indicating different information can be transmitted using the first signal line pair and the second signal line pair.

  A third wiring pattern is formed on the first insulating layer, and a fourth wiring pattern is formed on the second insulating layer. Therefore, similarly to the first and second wiring patterns, the capacitance of the fourth wiring pattern with respect to the conductive substrate can be made equal to the capacitance of the third wiring pattern with respect to the conductive substrate. . Thereby, it is possible to prevent a signal transmission error from occurring due to the unbalance of the second signal line pair.

( 7 ) The printed circuit board is further provided with a head portion provided on the conductive substrate for reading and writing signals, and the first, second, third and fourth wiring patterns are electrically connected to the head portion. It may be connected.

  In this case, the wired circuit board can be used as a suspension board for a drive device such as a hard disk drive device.

  Then, information is written to and read from the magnetic disk by the first and second wiring patterns constituting the first signal line pair and the third and fourth wiring patterns constituting the second signal line pair. be able to.

  In this case, signal transmission errors due to unbalance of the first signal line pair and signal transmission errors due to unbalance of the second signal line pair are sufficiently prevented. Occurrence is reliably prevented.

  According to the present invention, it is possible to prevent the occurrence of signal transmission errors.

  Hereinafter, a printed circuit board and a manufacturing method thereof according to embodiments of the present invention will be described with reference to the drawings. Hereinafter, as an example of a printed circuit board according to an embodiment of the present invention, a structure of a suspension board used for an actuator of a hard disk drive device and a manufacturing method thereof will be described.

(1-1) Structure of Suspension Board FIG. 1 is a top view of a suspension board according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view of the suspension board 1 of FIG.

  As shown in FIG. 1, the suspension board 1 includes a suspension main body 10 formed of a long metal substrate. On the suspension body 10, write wiring patterns W1, W2 and read wiring patterns R1, R2 are formed as indicated by thick solid lines.

  A magnetic head mounting portion (hereinafter referred to as a tongue portion) 12 is provided by forming a U-shaped opening 11 at the distal end portion of the suspension main body portion 10. The tongue portion 12 is bent at a location indicated by a broken line R so as to form a predetermined angle with respect to the suspension main body portion 10. Four electrode pads 21, 22, 23 and 24 are formed at the end of the tongue 12.

  Four electrode pads 31, 32, 33, and 34 are formed at the other end of the suspension body 10. The electrode pads 21 to 24 on the tongue 12 and the electrode pads 31 to 34 on the other end of the suspension body 10 are electrically connected by wiring patterns W1, W2, R1, and R2, respectively. A plurality of holes H are formed in the suspension body 10.

  In the suspension board 1, an insulating layer 40 composed of a plurality of layers is formed in the formation region of the plurality of wiring patterns W1, W2, R1, and R2 so as to cover the wiring patterns W1, W2, R1, and R2. .

  As shown in FIG. 2, the insulating layer 40 includes first, second, and third insulating layers 41, 42, and 43. A first insulating layer 41 having a first relative dielectric constant is formed on the suspension body 10.

  On the first insulating layer 41, there are a wiring pattern W1 for writing information on a magnetic disk (not shown) and a wiring pattern R1 for reading information on the magnetic disk. Is formed. The write wiring pattern W1 and the read wiring pattern R1 are arranged in parallel with each other at a predetermined interval.

  Further, a second insulating layer 42 having a second relative dielectric constant is formed on the first insulating layer 41 so as to cover the write wiring pattern W1 and the read wiring pattern R1.

  On the second insulating layer 42, a writing wiring pattern W2 is formed above the writing wiring pattern W1, and a reading wiring pattern R2 is formed above the reading wiring pattern R1.

  Further, a third insulating layer 43 having a third relative dielectric constant is formed on the second insulating layer 42 so as to cover the write wiring pattern W2 and the read wiring pattern R2.

  In a hard disk device (not shown) provided with the suspension board 1, current flows through the pair of write wiring patterns W1, W2 when information is written to the magnetic disk. Further, a current flows through the pair of read wiring patterns R1, R2 when reading information from the magnetic disk.

  In the present embodiment, the third relative dielectric constant is higher than the first and second relative dielectric constants.

(1-2) Manufacturing Suspension Board A method for manufacturing the suspension board 1 will be described. Below, the description about the formation process of the tongue part 12, the electrode pads 21-24, 31-34, and the hole H of FIG.

  3 and 4 are longitudinal sectional views showing the manufacturing process of the suspension board 1 according to the present embodiment. First, as shown in FIG. 3A, a long substrate made of stainless steel (SUS) is prepared as the suspension body 10. Then, a first insulating layer 41 mainly made of polyimide resin is formed on the suspension body 10.

  As the suspension body 10, a long substrate made of another metal material such as aluminum (Al) may be used instead of stainless steel. The thickness t1 of the suspension body 10 is, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 30 μm or less. The thickness t2 of the first insulating layer 41 is, for example, not less than 3 μm and not more than 20 μm, and preferably not less than 5 μm and not more than 15 μm.

  Subsequently, as shown in FIG. 3B, a write wiring pattern W1 and a read wiring pattern R1 made of copper (Cu) are formed on the first insulating layer 41. The write wiring pattern W1 and the read wiring pattern R1 are formed to be parallel to each other at a predetermined interval.

  The write wiring pattern W1 and the read wiring pattern R1 may be formed using a semi-additive method, for example, or may be formed using another method such as a subtractive method.

  The write wiring pattern W1 and the read wiring pattern R1 are not limited to copper, and can be formed using other metals such as gold (Au) and aluminum, or alloys such as a copper alloy and an aluminum alloy.

  The thickness t3 of the write wiring pattern W1 and the read wiring pattern R1 is, for example, 3 μm to 16 μm, and preferably 6 μm to 13 μm. The widths s1, s2 of the write wiring pattern W1 and the read wiring pattern R1 are, for example, 5 μm or more and 40 μm or less, and preferably 10 μm or more and 30 μm or less.

  The distance d1 between the write wiring pattern W1 and the read wiring pattern R1 is, for example, 5 μm or more and 100 μm or less, and preferably 10 μm or more and 60 μm or less.

  In the above configuration, a metal thin film may be formed between the first insulating layer 41 and the write wiring pattern W1 and between the first insulating layer 41 and the read wiring pattern R1. In this case, the adhesion between the first insulating layer 41 and the write wiring pattern W1 and the adhesion between the first insulating layer 41 and the reading wiring pattern R1 are improved.

  Thereafter, as shown in FIG. 3C, a second insulating layer 42 mainly made of polyimide resin is formed on the first insulating layer 41 so as to cover the write wiring pattern W1 and the read wiring pattern R1. .

  The thickness t4 of the second insulating layer 42 is, for example, 4 μm or more and 20 μm or less, and preferably 7 μm or more and 17 μm or less. The thickness h1 from the upper surface of the write wiring pattern W1 and the read wiring pattern R1 to the upper surface of the second insulating layer 42 is, for example, not less than 1 μm and not more than 5 μm.

  In the present embodiment, the second insulating layer 42 is formed of the same material as the first insulating layer 41. Therefore, the second dielectric constant of the second insulating layer 42 is the same as the first dielectric constant of the first insulating layer 41. Note that the first insulating layer 41 and the second insulating layer 42 may be formed of different materials. In this case, the first dielectric constant and the second dielectric constant may be different.

  Next, as shown in FIG. 4D, a write wiring pattern W2 and a read wiring pattern R2 made of copper are formed on the second insulating layer. Here, the writing wiring pattern W2 and the reading wiring pattern R2 are formed above the writing wiring pattern W1 and the reading wiring pattern R1, respectively.

  As a result, the upper surface of the write wiring pattern W1 and the lower surface of the write wiring pattern W2 face each other, and the upper surface of the read wiring pattern R1 and the lower surface of the read wiring pattern R2 face each other.

  The write wiring pattern W2 and the read wiring pattern R2 are formed in the same manner as the wiring patterns W1 and R1. The write wiring pattern W2 and the read wiring pattern R2 are not limited to copper, and can be formed using another metal such as gold (Au) or aluminum, or an alloy such as a copper alloy or an aluminum alloy.

  The thickness t5 of the write wiring pattern W2 and the read wiring pattern R2 is, for example, 3 μm or more and 16 μm or less, and preferably 6 μm or more and 13 μm or less. The widths s3 and s4 of the write wiring pattern W2 and the read wiring pattern R2 are, for example, 5 μm or more and 40 μm or less, and preferably 10 μm or more and 30 μm or less.

  The distance d2 between the write wiring pattern W2 and the read wiring pattern R2 is, for example, 5 μm or more and 100 μm or less, and preferably 10 μm or more and 60 μm or less.

  Metal thin films may be formed between the second insulating layer 42 and the write wiring pattern W2 and between the second insulating layer 42 and the read wiring pattern R2. In this case, the adhesion between the second insulating layer 42 and the write wiring pattern W2 and the adhesion between the second insulating layer 42 and the reading wiring pattern R2 are improved.

  Finally, as shown in FIG. 4E, a third insulating layer 43 mainly made of polyimide resin is formed on the third insulating layer 43 so as to cover the write wiring pattern W2 and the read wiring pattern R2. To do.

  The thickness t6 of the third insulating layer 43 is, for example, 4 μm or more and 20 μm or less, and preferably 7 μm or more and 17 μm or less. The thickness h2 from the upper surface of the write wiring pattern W2 and the read wiring pattern R2 to the upper surface of the third insulating layer 43 is not less than 1 μm and not more than 5 μm, for example.

  The third insulating layer 43 is formed, for example, by adding and dispersing a barium titanate having a high relative dielectric constant in a polyimide resin. The third relative dielectric constant of the third insulating layer 43 can be adjusted by adjusting the amount of barium titanate added to the polyimide resin. Thereby, the third dielectric constant of the third insulating layer 43 can be made higher than the first relative dielectric constant of the first insulating layer 41 and the second relative dielectric constant of the second insulating layer 42. it can.

  The third relative dielectric constant is 8 or more and 40 or less, and preferably 10 or more and 30 or less. Further, the first relative dielectric constant and the second relative dielectric constant are 2.5 or more and 3.8 or less, and preferably 2.8 or more and 3.5 or less.

  As described above, by forming the plurality of wiring patterns W1, W2, R1, R2 and the insulating layer 40 on the suspension body 10, the suspension board 1 is completed.

  In the suspension board 1, the widths s1, s3 of the write wiring patterns W1, W2 are equal to each other, and the widths s2, s4 of the read wiring patterns R1, R2 are also equal to each other.

  The widths s1 and s2 of the write wiring pattern W1 and the read wiring pattern R1 may be the same or different. The widths s3 and s4 of the write wiring pattern W2 and the read wiring pattern R2 may be equal to each other or may be different.

  For the first to third insulating layers 41 to 43, instead of polyimide resin, epoxy resin, acrylic resin, polyether nitrile resin, polyether sulfone resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyvinyl chloride resin, etc. Other resin materials may be used.

  Note that different insulating materials may be used for the first to third insulating layers 41 to 43, or the same insulating material may be used. Therefore, for example, by forming the third insulating layer 43 from an insulating material different from that of the first and second insulating layers 41 and 42, the relative dielectric constant of the third insulating layer 43 is set to the first and second insulating layers. You may set higher than the dielectric constant of the layers 41 and 42. FIG.

  Further, another insulating layer having a relative dielectric constant different from the second and third relative dielectric constants may be further formed between the second insulating layer 42 and the third insulating layer 43. Further, an insulating layer having a relative dielectric constant different from the first relative dielectric constant may be further formed between the suspension body 10 and the first insulating layer 41.

  The high dielectric constant material added to the third insulating layer 43 is not limited to barium titanate, but other titanates such as lead titanate, zirconates such as barium zirconate, and lead zirconate titanate. Other high dielectric constant materials such as (PZT) may be used.

(1-3) Effect In the suspension board 1 according to the present embodiment, the write wiring pattern W2 is formed on the second insulating layer 42 so as to be covered with the third insulating layer 43.

  In this case, when a potential is applied to the write wiring pattern W2, between the lower surface of the write wiring pattern W2 and the suspension main body 10, between the side surface of the write wiring pattern W2 and the suspension main body 10, and An electric field is formed between the upper surface of the write wiring pattern W2 and the suspension body 10.

  Accordingly, the electrostatic capacitance of the write wiring pattern W2 with respect to the suspension main body 10 is such that the first and second insulating layers 41 and 42 existing between the lower surface of the write wiring pattern W2 and the suspension main body 10 have It is given based on factors including the thickness and the third dielectric constant of the third insulating layer 43 as well as the first and second dielectric constants.

  On the other hand, the write wiring pattern W1 is formed on the first insulating layer 41 so as to be covered with the second insulating layer.

  In this case, when a potential is applied to the write wiring pattern W1, between the lower surface of the write wiring pattern W1 and the suspension main body 10, between the side surface of the write wiring pattern W1 and the suspension main body 10, and An electric field is formed between the upper surface of the write wiring pattern W1 and the suspension body 10.

  Therefore, the capacitance of the write wiring pattern W1 with respect to the suspension body 10 is not only the thickness of the first insulating layer 41 and the first relative dielectric constant, but also the second ratio of the second insulating layer 42. Given based on factors including dielectric constant.

  Here, in the present embodiment, the third relative dielectric constant is higher than the first and second relative dielectric constants. Therefore, even if the distance between the suspension body 10 and the write wiring pattern W2 is shorter than the distance between the suspension body 10 and the write wiring pattern W1, the writing for the suspension body 10 is performed. The capacitance of the wiring pattern W2 can be set to a value equivalent to the capacitance of the writing wiring pattern W1 for the suspension body 10.

  In this case, when the differential signal is transmitted by the write wiring patterns W1 and W2, the impedance of the write wiring pattern W1 and the impedance of the write wiring pattern W2 can be made equal.

  The read wiring pattern R2 is formed on the second insulating layer 42 so as to be covered with the third insulating layer 43, and the read wiring pattern R1 is formed on the first insulating layer 41 with the second insulating layer 42. It is formed to be covered with.

  In this case, like the write wiring patterns W1, W2, the distance between the suspension main body 10 and the read wiring pattern R2 is shorter than the distance between the suspension main body 10 and the read wiring pattern R1. However, the capacitance of the read wiring pattern R2 for the suspension main body 10 can be set to a value equivalent to the capacitance of the read wiring pattern R1 for the suspension main body 10.

  Thereby, when the differential signal is transmitted by the read wiring patterns R1 and R2, the impedance of the read wiring pattern R1 and the impedance of the read wiring pattern R2 can be made equal.

  As a result, it is possible to reliably prevent the occurrence of differential signal transmission errors due to unbalanced write wiring patterns W1, W2 and differential signal transmission errors due to unbalanced read wiring patterns R1, R2. Can do.

  In addition, a writing wiring pattern W2 is disposed above the writing wiring pattern W1, and a reading wiring pattern R2 is disposed above the reading wiring pattern R1. Therefore, the distance between the write wiring traces W1, W2 and the read wiring trace R1 is substantially equal to the distance between the write wiring traces W1, W2 and the read wiring trace R2, respectively. Thereby, it is considered that when the write current flows through the write wiring patterns W1, W2, the magnitudes of the induced electromotive forces generated in the read wiring patterns R1, R2 are substantially equal.

  This prevents the occurrence of crosstalk between the write wiring traces W1, W2 and the read wiring traces R1, R2.

  As a result, in the hard disk device (not shown) provided with the suspension board 1, it is reliably prevented that an error occurs when information is written to and read from the magnetic disk.

(1-4) Correspondence between each component of claim and each part of embodiment Hereinafter, an example of a correspondence between each component of the claim and each part of the embodiment will be described. It is not limited to examples.

  In the above embodiment, the suspension body 10 is an example of a conductive substrate, the writing wiring pattern W1 or the reading wiring pattern R1 is an example of the first or third wiring pattern, and the writing wiring. The pattern W2 or the read wiring pattern R2 is an example of the second or fourth wiring pattern, and the tongue portion 12 is an example of the head portion.

  As each constituent element in the claims, various other elements having configurations or functions described in the claims can be used.

  The present invention can be used for various electric devices or electronic devices.

1 is a plan view of a suspension board according to a first embodiment of the present invention. FIG. 2 is a longitudinal sectional view of the suspension board of FIG. 1 taken along the line AA. It is a figure which shows the manufacturing process of the suspension board based on 1st Embodiment. It is a figure which shows the manufacturing process of the suspension board based on 1st Embodiment. It is a longitudinal cross-sectional view which shows an example of the conventional suspension board. It is a longitudinal cross-sectional view which shows the other example of the conventional suspension board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Suspension board 10 Suspension main-body part 12 Tongue part 41 1st insulating layer 42 2nd insulating layer 43 3rd insulating layer W1, W2 Writing wiring pattern R1, R2 Reading wiring pattern

Claims (7)

A conductive substrate;
A first insulating layer formed on the conductive substrate;
A first wiring pattern formed on the first insulating layer;
A second insulating layer formed on the first insulating layer so as to cover the first wiring pattern;
A second wiring pattern formed on the second insulating layer;
A third insulating layer formed on the second insulating layer so as to cover the second wiring pattern;
The first wiring pattern and the second wiring pattern are disposed so as to face each other with the second insulating layer interposed therebetween,
The relative dielectric constant of the third insulating layer is higher than the relative dielectric constant of the first insulating layer and the relative dielectric constant of the second insulating layer,
The first and second wiring patterns constitute a first signal line pair,
The dielectric constant of the first to third insulating layers so that the capacitance of the first wiring pattern with respect to the conductive substrate is substantially equal to the capacitance of the second wiring pattern with respect to the conductive substrate. A printed circuit board, wherein rates are set respectively . 2. The printed circuit board according to claim 1, wherein the first wiring pattern and the second wiring pattern have the same width and are arranged at the same position in the width direction . 2. The relative dielectric constant of each of the first to third insulating layers is set so that the impedance of the first wiring pattern and the impedance of the second wiring pattern are substantially equal to each other. Or the printed circuit board of 2. The third dielectric layer, a wiring circuit board according to any one of claims 1 to 3, characterized in that it is formed of a resin containing a high dielectric constant material. 5. The printed circuit board according to claim 4, wherein the high dielectric constant material includes barium titanate. A third wiring pattern formed on the first insulating layer at a distance from the first wiring pattern;
A fourth wiring pattern formed on the second insulating layer at a distance from the second wiring pattern,
It said third and fourth wiring pattern is a wiring circuit board according to any one of claims 1 to 5, characterized in that forming the second signal line pair. A head portion provided on the conductive substrate for reading and writing signals;
7. The printed circuit board according to claim 6 , wherein the first, second, third and fourth wiring patterns are electrically connected to the head portion.

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