JP5604840B2 - Suspension board, suspension, suspension with head and hard disk drive - Google Patents

Description

  The present invention relates to a suspension substrate used in a hard disk drive (HDD), and more particularly to a suspension substrate capable of reducing differential impedance.

  In recent years, due to the spread of the Internet and the like, there has been a demand for an increase in the amount of information processing of personal computers and an increase in information processing speed, and along with this, the capacity of hard disk drives (HDD) incorporated in personal computers has increased. Increasing information transmission speed is required.

  A hard disk drive is a magnetic disk that is a magnetic recording medium, a spindle motor that rotates the magnetic disk at high speed, a magnetic head that reads or writes information on the magnetic disk, and each component that moves it while holding it with high precision. Drive control circuit and signal processing circuit.

  In addition, a component called a magnetic head suspension that supports the magnetic head used in this hard disk drive also has a signal line such as a copper wiring directly formed on a stainless steel spring from a conventional type in which a signal line such as a gold wire is connected. The so-called wireless suspension has been shifted to the integrated wiring type. Further, as the information transmission speed increases, it is necessary to design the suspension substrate as a distributed constant circuit.

  Wirings formed on such a suspension substrate are generally composed of a reading wiring consisting of a pair of wirings and a writing wiring consisting of a pair of wirings, as shown in Patent Document 1, respectively. It is formed on the same surface. In addition, such a pair of wires, for example, transmits electrical signals by differential transmission, and there is a differential impedance that is a characteristic impedance of the differential transmission line as a distributed constant circuit between the pair of wires. To do. The differential impedance is required to be lowered from the viewpoint of impedance matching as the impedance of the magnetic head and the preamplifier is lowered.

  As a differential wiring capable of reducing the differential impedance, a dielectric support substrate and a plurality of commonly connected first conductors disposed on the dielectric support substrate and having a first signal conductor. And at least one second having a second signal conductor disposed on the dielectric support substrate in an alternating relationship with the electrical trace and a plurality of the first electrical traces adjacent to each other in a plane. A trace interconnect array with reduced inductance, wherein the first and second signal conductors connect at least one of the read and write elements of the transducer head to a read / write circuit Has been proposed (Patent Document 2).

  The differential wiring (interleaved wiring) in which the wiring for transmitting the first electrical signal and the wiring for transmitting the second electrical signal having the opposite phase to the first electrical signal are alternately arranged as described above. For example, as shown in FIGS. 10 and 11, a pair of wirings 3 a and 3 b that are electrically connected by a jumper wire 21 to form an annularly closed line are sandwiched between substantially U-shaped portions. In the portion where the wirings 3a and 3b run side by side, a total of four wirings of two wirings 3a and two wirings 3b are arranged alternately. Therefore, the differential impedance can be reduced as compared with a configuration in which two pairs of wirings are arranged as in a normal differential wiring.

  It should be noted that the pair of wirings 3a and 3b constituting the interleave wiring may not be in the same form. Other examples of interleaved wiring are shown in FIGS. In this case, the wiring 3a is an annular line, but the wiring 3b has a normal single-line wiring configuration.

JP 2005-11387 A JP-A-10-124837

  Here, in order to further reduce the differential impedance with the configuration of the interleave wiring as described above, for example, it is necessary to increase the line width of the wiring or to reduce the distance between the wirings. However, increasing the line width of the wiring is not preferable from the viewpoint of increasing the density of the wiring, and reducing the distance between the wirings requires high processing accuracy, leading to an increase in cost. Therefore, it is not preferable.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a suspension substrate, a suspension, a suspension with a head, and a hard disk drive that can further reduce the differential impedance of interleaved wiring.

  As a result of various studies, the present inventor has found that the above problem can be solved by filling a dielectric material having a high relative dielectric constant between interleaved differential wirings in an interleaved wiring configuration, thereby completing the present invention. It is a thing.

That is, the invention according to claim 1 of the present invention includes a gimbal portion on which a magnetic head slider is mounted on which a magnetic head for reading or writing information on a magnetic recording medium is mounted, and the magnetic head and the reading circuit. In the suspension substrate having a read wiring electrically connected and a write wiring electrically connecting the magnetic head and the write circuit, the read wiring and the write wiring receive the first electric signal. A differential wiring comprising at least one transmission line for transmitting and at least one transmission line for transmitting a second electric signal having a phase opposite to that of the first electric signal, wherein at least one of the transmission lines. has become a closed line annularly, the differential lines are at least a part of a substrate for the suspension, it has a configuration in which three or more wirings are alternately disposed, the three Including both sides of the wiring lines of the upper is sandwiched on both sides of the wiring in the interleaved arrangement, between the differential lines, the dielectric consisting of dielectric constant of 5 or more resin to fill the space is formed This is a suspension substrate.

  The invention according to claim 2 of the present invention is characterized in that the dielectric is formed under a cover layer provided for covering and protecting the differential wiring. This is a suspension substrate.

  In the invention according to claim 3 of the present invention, the dielectric is formed on a cover layer provided to cover and protect the differential wiring. This is a suspension substrate.

  In the invention according to claim 4 of the present invention, the dielectric is made of the same material as a cover layer provided to cover and protect the differential wiring. Substrate.

Further, in the invention according to claim 5 of the present invention, the dielectric is made of a polyimide resin containing barium titanate, and the suspension substrate according to any one of claims 1 to 4 It is.

According to a sixth aspect of the present invention, there is provided a suspension comprising the suspension substrate according to any one of the first to fifth aspects.

According to a seventh aspect of the present invention, there is provided a suspension with a head comprising the suspension according to the sixth aspect and a magnetic head slider mounted on the suspension.

According to an eighth aspect of the present invention, there is provided a hard disk drive including the suspension with a head according to the seventh aspect.

  According to the present invention, since the dielectric having a high relative dielectric constant is filled between the alternately arranged differential wirings in the interleaved wiring, the capacitive coupling between the differential wirings is further increased. There is an effect that the differential impedance of the differential wiring thus formed can be further reduced.

It is a schematic plan view showing an example of a suspension substrate according to the present invention. It is AA sectional drawing of the R area | region in FIG. It is a schematic sectional drawing which shows the other example of the board | substrate for suspensions concerning this invention. It is a schematic sectional drawing which shows the other example of the board | substrate for suspensions concerning this invention. It is a schematic sectional drawing which shows the other example of the board | substrate for suspensions concerning this invention. It is a typical process figure showing an example of a manufacturing method of a substrate for suspensions concerning the present invention. 1 is a schematic plan view showing an example of a suspension according to the present invention. It is a schematic plan view showing an example of a suspension with a head according to the present invention. 1 is a schematic plan view showing an example of a hard disk drive according to the present invention. It is explanatory drawing which shows an example of the interleave wiring in the conventional board | substrate for suspensions. It is BB sectional drawing in FIG. It is explanatory drawing which shows the other example of the interleave wiring in the conventional board | substrate for suspensions. It is CC sectional drawing in FIG.

  Hereinafter, the suspension substrate, suspension, suspension with head, and hard disk drive of the present invention will be described in detail.

[Suspension substrate]
First, the suspension substrate of the present invention will be described.
FIG. 1 is a schematic plan view showing an example of the suspension substrate of the present invention. A suspension substrate 10 shown in FIG. 1 has a gimbal portion 11 for mounting a magnetic head slider at a tip portion and a connection portion 12 for connecting a reading circuit or a writing circuit at a terminal portion. A read wiring 13 for electrically connecting the magnetic head and the read circuit and a write wiring 14 for electrically connecting the magnetic head and the write circuit are provided between the section 11 and the connection section 12. It is what you have.
Here, the read wiring 13 and the write wiring 14 are arranged along the outer periphery of the suspension substrate in order to avoid mutual electrical influence as much as possible and to maintain the mechanical balance of the suspension substrate. ing.

  Although not shown in detail in FIG. 1, each of the read wiring 13 and the write wiring 14 has at least one transmission line that transmits the first electric signal and an opposite phase to the first electric signal. A pair of differential wirings composed of at least one transmission line for transmitting the second electrical signal, wherein three or more transmission lines are alternately arranged, and at least one of the transmission lines. One is an annularly closed track.

  FIG. 2 is a cross-sectional view taken along the line AA in the region R in FIG. In the present invention, the write wiring 14 is described in the same manner as the read wiring 13.

  As shown in FIG. 2, the suspension substrate 10 includes an insulating layer 2, two wirings 3 a that transmit a first electric signal formed on one surface of the insulating layer 2, and a second electric signal. Formed on the other surface of the insulating layer 2 and a pair of four differential wirings composed of two wirings 3b for transmitting the signal, a dielectric 4 formed so as to fill the space between the wirings 3a and 3b. And a metal substrate 1.

  Each of the wirings 3a and 3b is electrically connected in the vicinity of both ends of the suspension substrate to form a circular line. In the portion where the wirings 3a and 3b other than the vicinity of both ends of the suspension substrate run in parallel, the wiring 3a 3b, 3a and 3b are alternately arranged in this order.

  Furthermore, in order to suppress the attenuation of electrical signals and the deterioration of wiring, the suspension substrate of the present invention may have a structure having a cover layer 5 formed so as to cover the wirings 3 a and 3 b and the dielectric 4.

  Further, the suspension substrate of the present invention may have a configuration in which a dielectric 4 is formed on a cover layer 5 formed so as to cover the wirings 3a and 3b, as shown in FIG.

  Further, as shown in FIG. 4, the suspension substrate of the present invention has a configuration in which the dielectric 4 is formed so as to cover the wirings 3a and 3b while filling the space between the wirings 3a and 3b, that is, a cover layer. 5 may be made of the same material as that of the dielectric 4.

  As described above, according to the present invention, in addition to the effect of reducing the differential impedance by the interleaved wiring structure in which a plurality of wirings are alternately arranged, the presence of the dielectric formed between the wirings causes the electrical between the differential wirings. Since the capacitive coupling is further improved, the differential impedance can be further reduced.

  Hereinafter, the suspension substrate of the present invention will be described for each configuration.

[wiring]
The material of the wirings 3a and 3b is not particularly limited as long as it has desired conductivity, and examples thereof include copper (Cu). Note that a material having electrical characteristics similar to that of pure copper may be used as the wiring material.
In the present invention, the materials of the wirings 3a and 3b may be the same or different from each other, but are preferably the same. This is because the wiring 3a and 3b can be easily designed and manufactured.
The wirings 3a and 3b may have a protective plating layer formed of nickel (Ni) or gold (Au) on the surface thereof.

  The thickness of the wirings 3a and 3b is, for example, preferably in the range of 4 μm to 18 μm, more preferably in the range of 5 μm to 15 μm. This is because if the wiring thickness is too small, it may not be possible to achieve a sufficiently low impedance, and if the wiring thickness is too large, the suspension substrate may become too rigid.

  The line width of the wiring is preferably in the range of 10 μm to 100 μm, for example. If the wiring line width is too small, the desired conductivity may not be obtained. If the wiring line width is too large, the suspension substrate may not be sufficiently dense. Because.

  Moreover, it is preferable that the distance between wirings exists in the range of 10 micrometers-100 micrometers, for example. If this distance is too small, it is not preferable because it requires high processing accuracy and increases costs. On the other hand, if this distance is too large, the suspension substrate may not be sufficiently dense. Because there is sex.

In the present invention, the line widths of the wirings may be the same or different as long as the differential impedance reduction effect by the interleaved wiring structure can be obtained.
For example, as shown in FIG. 2, if the number of wirings 3a for transmitting the first electrical signal and the number of wirings 3b for transmitting the second electrical signal are the same, the line width of each wiring is the same. It is preferable that This is because the design of interleave wiring becomes easy.

On the other hand, when the number of wirings 3a that transmit the first electrical signal is different from the number of wirings 3b that transmit the second electrical signal, the line width of each wiring is preferably changed appropriately.
For example, as shown in FIG. 5, when the wiring 3a is composed of two lines and the wiring 3b is composed of one line, the line width of the wiring 3b is preferably twice the line width of the wiring 3a. . This is because a symmetrical configuration makes it easier to design interleaved wiring.

  As shown in FIG. 5, when the wiring 3a is composed of two and the wiring 3b is composed of one, the wiring 3a is electrically connected in the vicinity of both ends of the suspension substrate to form an annular line. However, the wiring 3b has a normal single-line wiring configuration.

[Dielectric]
Next, the dielectric in the present invention will be described. For example, as shown in FIG. 2, the dielectric 4 in the present invention is formed so as to fill a space between the wiring 3a and the wiring 3b. As a result, the capacitive coupling between the differential wirings is further increased, so that the differential impedance of the differential wirings arranged alternately can be further reduced.

  In the example of FIG. 2, the cover layer 5 is formed so as to cover the wirings 3a, 3b and the dielectric 4. However, as shown in FIG. 3, the dielectric 4 covers the wirings 3a, 3b. You may form on the cover layer 5 formed in this way.

  As shown in FIG. 4, the dielectric 4 is formed so as to cover the wirings 3 a and 3 b while filling the space between the wirings 3 a and 3 b, that is, the cover layer 5 is the same as the dielectric 4. It is good also as composition which consists of material.

The material of the dielectric 4 is not particularly limited as long as it is a resin having a high relative dielectric constant, for example, a relative dielectric constant of 3 or more, preferably 5 or more. For example, titanic acid, which is a ferroelectric material, is used. A polyimide resin containing barium (BaTiO ₃ ), lead zirconate titanate (Pb (Zr, Ti) O ₃ ), or the like can be used.
In this case, it is possible to control the relative dielectric constant of the resin within a desired range by controlling the content of barium titanate or the like. For example, the relative dielectric constant of a polyimide resin having a relative dielectric constant of 3.0 is By containing an appropriate amount of 1200 barium titanate, the relative dielectric constant can be increased to 5 or more.

The dielectric has only to have a thickness necessary for filling the space between the wirings. For example, the thickness is preferably in the range of 4 μm to 20 μm, and more preferably in the range of 5 μm to 17 μm. If the thickness of the dielectric 4 is too large compared to the thickness of the wirings 3a and 3b, the coverage with the cover layer 5 is inferior. In addition, when the thickness of the dielectric is smaller than the thickness of the wiring, it is not preferable because the capacitive coupling between the differential wirings is inferior.
The width of the dielectric is preferably the same as the distance between the wirings, for example, in the range of 10 μm to 100 μm.

[Cover layer]
Next, the cover layer used in the present invention will be described. In order to suppress the attenuation of the electric signal and the deterioration of the wiring, the wirings 3a and 3b are preferably covered with a cover layer. However, in order to suppress the occurrence of warpage of the suspension substrate, it is preferable that the cover layer is formed only at necessary portions.

  For example, as shown in FIG. 2, when the dielectric 4 is formed so as to fill between the wiring 3a and the wiring 3b, the cover layer 5 is formed so as to cover the wiring 3a, 3b and the dielectric 4. It is preferable. In the present invention, as shown in FIG. 3, the cover layer 5 may be formed so as to cover the wirings 3 a and 3 b, and then the dielectric 4 may be formed on the cover layer 5.

Examples of the material of the cover layer 5 as described above include polyimide. The material of the cover layer 5 may be a photosensitive material or a non-photosensitive material. In the present invention, as shown in FIG. 4, the same material as that of the dielectric 4 is used for the cover layer 5, the gap between the wiring 3 a and the wiring 3 b is filled with the dielectric 4, and the wiring 3 a is further covered with the dielectric 4. 3b may be covered.
The thickness of the cover layer 5 is preferably in the range of 3 μm to 30 μm, for example.

[Insulation layer]
Next, the insulating layer in the present invention will be described. For example, as shown in FIG. 2, the insulating layer 2 in the present invention has wirings 3a and 3b on one surface and a metal substrate 1 on the other surface. The material of the insulating layer 2 is not particularly limited as long as it has a desired insulating property, and examples thereof include polyimide. The material of the insulating layer 2 may be a photosensitive material or a non-photosensitive material. In addition, the thickness of the insulating layer 2 is preferably in the range of, for example, 5 to 30 μm, and more preferably in the range of 10 to 20 μm.

[Metal substrate]
Next, the metal substrate in the present invention will be described. As shown in FIG. 2, the metal substrate 1 in the present invention is formed on the surface of the insulating layer 2 opposite to the wirings 3a and 3b. In order to prevent transmission loss when transmitting a high-frequency signal, it is preferable that the metal substrate 1 on the surface opposite to the insulating layer 2 where the wirings 3a and 3b are formed is removed.

  The material of the metal substrate 1 is not particularly limited as long as it has desired conductivity and springiness, and examples thereof include stainless steel. The thickness of the metal substrate 1 is, for example, preferably in the range of 10 μm to 30 μm, and more preferably in the range of 15 μm to 25 μm.

[Method of manufacturing suspension substrate]
Next, the manufacturing method of the suspension substrate of the present invention will be described. The manufacturing method of the suspension substrate of the present invention is not particularly limited as long as it is a method capable of obtaining the suspension substrate having the above-described configuration. Hereinafter, an example of a method for manufacturing a suspension substrate according to the present invention will be described with reference to FIG.

  In the method for manufacturing a suspension substrate shown in FIG. 6, first, a laminate in which a metal substrate 1A (for example, stainless steel), an insulating layer 2 (for example, polyimide), and a conductive layer 3 (for example, copper) are stacked in this order is prepared. (FIG. 6A).

  Next, a dry film resist is laminated on the surface of the conductive layer 3, and a resist pattern 6 is formed by performing exposure and development. Similarly, a resist pattern 6 is formed on the surface of the metal substrate 1A (FIG. 6B). Next, the conductive layer 3 and the metal substrate 1A exposed from the resist pattern 6 are etched, and the resist pattern 6 is peeled off after the etching, thereby forming the wirings 3a and 3b and the metal substrate 1 (FIG. 6C).

  Next, a coating liquid containing a dielectric 4 (for example, a polyimide resin added with barium titanate) is applied, dried, exposed, developed, and then heat treated at a predetermined temperature to form dielectric 4. (FIG. 6D).

  Finally, the cover layer 5 is formed by a known material and method (for example, photosensitive polyimide plate making). Thereby, the suspension substrate 10 can be obtained (FIG. 6E).

  In the above description, for example, as shown in FIG. 2, the method of manufacturing the suspension substrate in which the dielectric 4 is formed under the cover layer 5 has been described. However, for example, the wirings 3a and 3b and the metal substrate After the step of forming 1 (FIG. 6C), the cover layer 5 is formed, and then the dielectric 4 is formed, so that the dielectric 4 is formed on the cover layer 5 as shown in FIG. The suspension substrate in the formed form can be manufactured.

  Further, in the step of forming the dielectric 4 (FIG. 6D), the dielectric 4 is formed so as to cover the wires 3a and 3b while filling the space between the wires 3a and 3b, for example, FIG. A suspension substrate having a configuration as shown in FIG. In addition, you may form the part which functions as a dielectric material, and the part which functions as a cover layer by another process as mentioned above.

[suspension]
Next, the suspension of the present invention will be described. The suspension of the present invention includes the above-described suspension substrate.

  FIG. 7 is a schematic plan view showing an example of the suspension of the present invention. The suspension 40 shown in FIG. 7 has the above-described suspension substrate 10 and the load beam 30 provided on the surface of the suspension substrate 10 opposite to the surface on which the magnetic head slider mounting region 15 is formed. Is.

  According to the present invention, by using the above-described suspension substrate, a suspension with a further reduced differential impedance can be obtained.

  The suspension of the present invention has at least a suspension substrate, and usually further has a load beam. Since the suspension substrate is the same as described above, description thereof is omitted here. The load beam can be the same as the load beam used for a general suspension.

[Suspension with head]
Next, the head suspension according to the present invention will be described. The suspension with a head of the present invention includes the above-described suspension and a magnetic head slider mounted on the suspension.

  FIG. 8 is a schematic plan view showing an example of the suspension with a head of the present invention. A suspension 50 with a head shown in FIG. 8 has the above-described suspension 40 and a magnetic head slider 41 mounted on the magnetic head slider mounting region 15 of the suspension 40.

  According to the present invention, by using the above-described suspension, a suspension with a head with a further reduced differential impedance can be obtained.

  The suspension with a head of the present invention has at least a suspension and a magnetic head slider. Since the suspension is the same as described above, description thereof is omitted here. Further, the magnetic head slider can be the same as the magnetic head slider used in a general suspension with a head.

[Hard disk drive]
Next, the hard disk drive of the present invention will be described. The hard disk drive of the present invention includes the above-described suspension with a head.

  FIG. 9 is a schematic plan view showing an example of the hard disk drive of the present invention. A hard disk drive 60 shown in FIG. 9 is connected to the suspension 50 with a head described above, a disk 61 on which the head suspension 50 writes and reads data, a spindle motor 62 that rotates the disk 61, and the suspension 50 with a head. The arm 63, the voice coil motor 64 that moves the magnetic head slider of the suspension 50 with head, and the case 65 that seals the above members are included.

  According to the present invention, a hard disk drive with higher functionality can be obtained by using the suspension with a head described above.

  The hard disk drive of the present invention has at least a suspension with a head, and usually further includes a disk, a spindle motor, an arm, and a voice coil motor. Since the suspension with a head is the same as described above, description thereof is omitted here. As other members, the same members as those used in a general hard disk drive can be used.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
In accordance with the manufacturing method described above, a suspension substrate according to the present invention having the structure shown in FIG. 2 was obtained. Here, a stainless steel having a thickness of 20 μm is used for the metal substrate 1A, a polyimide having a thickness of 10 μm and a relative dielectric constant of 3.0 is used for the insulating layer 2, and copper having a thickness of 12 μm is used for the conductive layer 3. .
The line widths of the wirings 3a and 3b were both 45 μm, and the distance between the wirings 3a and 3b was 15 μm. Further, the horizontal distance between the end of the metal substrate 1 and the ends of the wirings 3a and 3b was set to 40 μm.
The dielectric 4 was made of polyimide whose relative dielectric constant was controlled to 5.0 by containing barium titanate, and the thickness was 12 μm, which was the same as that of the wirings 3a and 3b. The cover layer 5 was made of polyimide having a relative dielectric constant of 3.0 so that the thickness from the insulating layer 2 was 17 μm.
As a result of calculating the differential impedance in the obtained suspension substrate, the differential impedance was 28Ω.

(Comparative Example 1)
A suspension substrate of Comparative Example 1 was obtained in the same manner as in Example 1 except that the dielectric 4 and the cover layer 5 were not formed. As a result of calculating the differential impedance in the obtained suspension substrate, the differential impedance was 31.5Ω.

  As described above, in the suspension substrate according to the present invention, the differential impedance can be further reduced by forming the dielectric having a high relative dielectric constant between the differential wirings arranged alternately. By using the suspension substrate according to the present invention, it is possible to obtain a suspension, a suspension with a head, and a hard disk drive having a differential impedance reduced from that of the conventional configuration.

DESCRIPTION OF SYMBOLS 1, 1A ... Metal substrate 2 ... Insulating layer 3 ... Conductive layer 3a ... Wiring (wiring which transmits a 1st electric signal)
3b... Wiring (wiring for transmitting the second electric signal)
DESCRIPTION OF SYMBOLS 4 ... Dielectric 5 ... Cover layer 6 ... Resist pattern 10, 10 '... Suspension substrate 11 ... Gimbal part 12 ... Connection part 13 ... Reading wiring 14 ... Write wiring 15 ... Magnetic head slider mounting area 20 ... Interleave wiring 21 ... Jumper wire 22 ... Connection terminal 30 ... Load beam 40 ... Suspension 41 ... Magnetic head slider 50 ..Suspension with head 60 ... Hard disk drive 61 ... Disk 62 ... Spindle motor 63 ... Arm 64 ... Voice coil motor 65 ... Case

Claims (8)

A gimbal portion on which a magnetic head slider for mounting a magnetic head for reading or writing information on a magnetic recording medium is mounted; a read wiring for electrically connecting the magnetic head and a reading circuit; and the magnetic head; In a suspension substrate having a write wiring for electrically connecting a write circuit,
The read wiring and the write wiring each include at least one transmission line for transmitting a first electrical signal and at least one transmission line for transmitting a second electrical signal having a phase opposite to that of the first electrical signal. Differential wiring consisting of
At least one of the transmission lines is an annularly closed line,
The differential wiring has a configuration in which three or more wirings are alternately arranged in at least a part on the suspension substrate,
In a configuration in which the three or more wirings are alternately arranged, a dielectric made of a resin having a relative dielectric constant of 5 or more so as to fill a space between the differential wirings, including both sides of the wiring sandwiched between both adjacent wirings A suspension substrate, wherein:   The suspension substrate according to claim 1, wherein the dielectric is formed under a cover layer provided to cover and protect the differential wiring.   2. The suspension substrate according to claim 1, wherein the dielectric is formed on a cover layer provided to cover and protect the differential wiring.   The suspension substrate according to claim 1, wherein the dielectric is made of the same material as a cover layer provided for covering and protecting the differential wiring. The suspension substrate according to any one of claims 1 to 4, wherein the dielectric is made of a polyimide resin containing barium titanate . A suspension comprising the suspension substrate according to any one of claims 1 to 5. A suspension with a head comprising the suspension according to claim 6 and a magnetic head slider mounted on the suspension. A hard disk drive comprising the suspension with a head according to claim 7.

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