JP2003152404A - Signal transmission line, suspension provided therewith, and recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the area of a stainless plate under a conductor concerns the transmission loss, the hole pitch concerns the transmission band, and there are some lines not ensuring the transmission band, depending on the a rate of hole area the hole pitch of the stainless plate. SOLUTION: It is found that increasing the rate of hole area (H/HP) of holes 33 formed in a stainless plate 30 reduces the line loss, and the transmission band can be ensured up to a frequency determined to such extent that the shortest wavelength is 5 times as much as the hole pitch HP. A transmission line is constituted with a maximum hole pitch HP set to 1/5 times as short as a wavelength meeting a required band involving harmonic components of a recorded waveform, this ensuring a low transmission loss and the required transmission band.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a transmission line structure of a recording system and a reproducing system from a preamplifier of a recording device such as a magnetic disk device to a recording / reproducing head, a suspension provided with the transmission line, and a recording device.

[0002]

2. Description of the Related Art With the development of computers, there has been a demand for high capacity and high speed transfer of magnetic disk devices.
For large-capacity and high-speed transfer, the recording head and the reproducing head are separated from each other, and the recording is performed by the inductive head, and the reproducing is performed by the MR head using the magnetoresistive effect. Therefore, dedicated reciprocating lines are provided adjacent to the recording head and the reproducing head from the preamplifier.

For information recording, information "1" and "0" are assigned according to the presence or absence of magnetization reversal on the medium. Therefore, when recording information, the reversal magnetic field from the recording head is recorded.

In order to generate a reversal magnetic field in the recording head,
The recording current waveform transmitted to the recording head is characterized by a rectangular wave having an overshoot at rising / falling.

In high frequency recording for advancing high speed transfer, it is necessary to shorten the time of the rising / falling portion of the recording current. If the rise / fall time is shortened, the spectrum of the waveform needs to have a high frequency.

From this point of view, it is known that it is necessary to perform impedance matching between the characteristic impedance of the line and the recording system preamplifier circuit. (John D. Leighto
n, Sally Doherty, Carl Elliott; ”Design Considera
tions for High Data-Rate Pre-Amplifiers for Use in
a Disk-Drive ”, IEEE Trans. MAG., vol.37, No.2, p
p.627-632) Japanese Patent Application Laid-Open No. 9-2826 for impedance matching.
There is a method of adjusting the characteristic impedance of the transmission line by appropriately adjusting the electrostatic capacitance and the mutual inductance between the line conductor and the stainless steel by forming a hole in the stainless steel portion under the transmission line as disclosed in Japanese Patent No. 24. .

[0007]

In order to adjust the characteristic impedance of the transmission line, when a transmission line having a hole in the stainless steel portion under the line conductor is used, transmission is performed at a certain frequency or higher even within the transmission signal band. Loss sharply increases and the transmission system becomes band limited. Therefore, a new problem arises that the transmission waveform is distorted, the characteristic of the magnetic recording current is deteriorated, and it becomes an obstacle to high recording density.

However, in the above-mentioned conventional example, there is no description about how to form the holes, and therefore this problem cannot be solved.

[0009]

[Means for Solving the Problems] As a result of various investigations on the above problems, transmission loss can be expected to be reduced by increasing the aperture ratio of the stainless portion under the line conductor, but the aperture pitch drastically reduces the transmission loss. It was found to be related to increasing frequency. Therefore, in order to secure a low loss line within the required transmission signal band, the maximum opening pitch of the stainless steel part was limited.

Specifically, a conductor for transmitting a differential signal,
A metal body provided with the conductor and the insulator sandwiched therebetween,
The metal body is provided with holes parallel to the conductor and provided at a pitch of 2 mm or less.

Alternatively, at least two transmitting differential signals
The present invention includes a book conductor and a metal body provided with the conductor and the insulator sandwiched therebetween, and has a width of a value obtained by adding 0.16 mm or more to the sum of the width of the conductor and the interval between these conductors. With holes.

Alternatively, a conductor for transmitting a differential signal,
A metal body provided with the conductor and the insulator sandwiched therebetween,
The holes are provided in the direction parallel to the conductor of the metal body at a pitch of 1/5 or less with respect to the wavelength of the maximum frequency of the transmission band.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the present invention is applied to a magnetic disk device will be described with reference to the drawings.

First, the structure of the magnetic disk device will be described with reference to FIGS. The magnetic disk device includes a head disk assembly (HDA) 10 and a recording / reproducing control circuit 1.
It is composed of 1. The HDA 10 and the recording control circuit 1
1 also includes those which are housed in the same housing. HDA10 is
The magnetic recording medium 13 is composed of a spindle section 12 and a carriage section 15 having a magnetic head 14 for recording information on the magnetic recording medium 13 and for reading the recorded information.

The carriage portion 15 includes a suspension 19
Voice coil motor (VCM) 17 for seeking and positioning the magnetic head 14 attached to the tip of the magnetic recording medium on the magnetic recording medium, an arm 18 to which a suspension 19 is attached, and a flexible coil for transmitting a recording / reproducing signal to the magnetic head 14. Printed Circuits (FPC; Flex
16), R / W-IC (preamplifier) 20 mounted on the FPC 16, and R / W-IC 2
0 and the magnetic head 14 are constituted by a transmission line 21 for relaying a recording / reproducing signal.

A recording / reproducing control circuit 11 is provided between the HDA 10 and the external device. The recording / reproducing control circuit 11 includes a signal processing LSI 22 and a hard disk drive control (HD
C control) 23 is installed. HDA side connector 25-1 and recording / reproduction control circuit 11 side connector 25-
By connecting 2, the R / W-IC 20 and the signal processing LSI 22 are connected. It is connected to an external device via the external interface 24 of the recording / reproducing control circuit 11.

Next, the wiring-integrated suspension 19 installed at the tip of the arm 18 will be described with reference to FIG. The structure of the suspension 19 is such that the transmission line 21 and the magnetic head 1 are formed on a spring portion made of a stainless material.
The members obtained by combining the gimbal portions including No. 4 are laminated and integrated by using a joining method such as welding. The transmission line 21 is divided into two parts, that is, an on-suspension wiring portion and an arm parallel running relay wiring portion. There is a transmission line 21a along the arm 18. Further, the transmission line 21b is also provided on the suspension 19. The magnetic head 14 is connected to the tip of the transmission line 21b.

The first line configuration of the transmission line 21 is a relay connection type, in which the connection is made from the arm parallel wiring portion to the wiring portion on the suspension at a place where the wiring form changes. The second line configuration is a long tail structure type in which a printed wiring having the same structure as the printed wiring on the suspension extends to the preamplifier. The present invention is applicable to both structures,
Particularly in the case of a long tail structure, the structure of the printed wiring portion of the suspension described below may be applied.

Next, the transmission line 21 targeted by the present invention
(B) The structure will be described with reference to FIG.

First, there is a lower metal plate which serves as a substrate. In this embodiment, the stainless plate 30 is used for description, but a metal other than stainless steel, for example, copper may be used. An insulating layer 31 typified by polyimide is applied on the stainless steel plate 30 which is the lower metal plate to form an insulator, and a reciprocating line (also referred to as parallel conductor or conductor) is formed on the insulating layer 31 by plating or vapor deposition. ) 32 is formed. A transmission line having a cross-sectional structure in which a part or all of the line is covered with polyimide to protect the conductor is basically used.

The transmission line 21 is made of a plate-shaped insulating material, a metal material such as stainless steel adhered to one surface, and a conductor 32 forming material such as rolled copper adhered to the other surface. Prepare a laminated substrate. The conductor surface of the laminated substrate may be formed by shaving the shape of the conductor 32 by a method such as etching. Whichever forming method is used, the plate 30 made of a stainless material is also used as a gimbal forming member.

By making appropriate holes 33 in the stainless steel plate 30 under the line conductor at a predetermined interval in parallel with the conductor, and selecting the ratio of the area of the size of the hole 33 and the area of the stainless steel plate 30 appropriately, The characteristic impedance is set to an appropriate value by controlling the inductance and capacitance between the reciprocating lines 32.

Here, although the area ratio of the holes 33 and the area ratio of the stainless steel plate 30 are properly selected, the transmission loss becomes very large above a certain frequency, and the transmission band is limited. Therefore, the relationship between the size of the hole 33 and the transmission band was investigated.

The main parameters are HP: hole pitch,
H: hole length, M: stainless steel cover length = HP-H, H
W: open hole width, Lw: conductor width, S: conductor interval. In addition, the aperture ratio = H / HP (%), Vp = signal propagation speed, α: transmission loss, θ: rotation declination, BWw: transmission band frequency, length: line length. is there.

First, a method of measuring the transmission characteristic of the transmission line will be described with reference to FIG.

The transmission characteristic of the transmission line is measured as the S parameter, and the transmission loss (α) and the propagation velocity (Vp) are obtained from S21 (the 2nd row and 1st column element of the S matrix). FIG. 4A shows S21 on a Gaussian plane. The locus rotates counterclockwise with increasing frequency. Rotation declination (θ) 34
Is the ratio of the wavelength to the line length. Therefore, as shown in FIG. 4B, the horizontal axis represents the frequency (Freq) and the vertical axis represents the rotation declination (θ), and the rotation declination (θ) for each frequency.
If is plotted, it becomes a straight line passing through the origin. The product of the reciprocal of the slope (θ / Freq) of this line and (−2π) represents the time required for the signal to pass through the line length. Therefore, this straight line is the propagation velocity (V
p), and Vp can be obtained from this figure.

Further, the center (coordinates (0,
From 0)) to a circle having a radius of 1 as a reference, the amount of decrease from the reference circle to the S21 locus at each declination (θ) represents the transmission loss (α) 35 including the effect of impedance mismatch.

As a result of evaluating the line samples having no holes 33 in the stainless plate 30, the ratio of the rotation deviation angle (θ) to the frequency is constant for each sample, that is, the propagation velocity (Vp).
Was constant without depending on the transmission band frequency (BWw). As a result of evaluating the transmission loss (α), it was found that the transmission loss increased substantially in proportion to the square of the transmission band frequency (BWw).

The definition of transmission loss (α) described below is as follows:     α = {ln (loss amount)} / length [Np / m] (Equation 1) It is represented by. Here, ln () represents a natural logarithm.

The task of the transmission line is to transmit the input data to the output point without loss. Therefore, it is necessary to reduce the transmission loss (α) in order to increase the transmission efficiency in the transmission line. Below, the line conditions are compared using the transmission loss (α) as an evaluation value.

First, the relationship between the transmission characteristics and the hole size of the stainless material will be described with reference to FIGS.

HW = 0.56 mm, open area ratio = 50% (H
= M), Lw = 0.16 mm, S = 0.08 mm (2 ×
FIG. 5 shows the frequency characteristic of the transmission loss (α) with respect to the transmission line (Lw + S = 0.40 mm) with the aperture pitch (HP) of the stainless plate 30 below the conductor 32 as a parameter. For measurement up to 6 GHz, the aperture pitch (H
P) = 30 mm, transmission loss (α) above 1.8 GHz
Is rapidly increasing, and the opening pitch (HP) = 14
In mm, the transmission loss (α) sharply increases above 3.7 GHz. In addition, opening pitch (HP) = 2 mm
Then, there is no frequency at which the transmission loss (α) rapidly increases up to at least 6 GHz. From this result, it can be seen that there is a relationship between the transmission band of the line and the aperture pitch (HP). It can also be seen that the transmission loss (α) can be kept small regardless of the frequency by setting the aperture pitch (HP) to 2 mm or less. Of course, when the transmission band frequency (BWw) is less than 3.7 GHz, the aperture pitch (HP) is 14 mm or less, and when the transmission band frequency (BWw) is less than 1.8 GHz, the aperture pitch (HP). Needless to say, may be designed to be 30 mm or less. Further, the aperture pitch (HP) may be 2 mm or less and may be made as small as possible.

On the other hand, as a result of obtaining the propagation velocity (Vp) of each line by the measurement of FIG. 4, it is approximately Vp = 1.6 × 10 ⁸ (m /
s). When the frequency at which the transmission loss (α) rapidly increases is defined as the transmission band (BWw), the propagation speed (V
The wavelength (λ) corresponding to the transmission band can be obtained using p).

Λ = Vp / BWw [m] (Equation 2) Therefore, using the aperture width (HW), aperture ratio (H / HP), etc. as parameters, from the transmission band and the propagation speed with respect to the aperture pitch (HP). The relationship of the obtained wavelength (λ) is shown in FIG. E8 in the figure means 10 ⁸ . Opening width (H
W), open area ratio (H / HP), etc. are measured under various conditions, the wavelength (λ) ((2.5 × HP) ≦ λ ≦ (5 × H
P)), and converted to the transmission band (BWw), ((Vp / (5 × HP)) ≦ BWw ≦ (Vp /
(2.5 × HP))) is determined.

In reality, no matter how the holes vary,
The worst state is the state in which the transmission band does not become narrower than this. Assuming that the wavelength corresponding to the transmission band at that time is (λmax), the following relationship holds: λmax = 5 × HP [m] (Equation 3). Therefore, the maximum frequency of the transmission band (BW
Hole pitch (HP) for wavelength (λ) corresponding to w)
It is advisable to provide the repeating pitch so that the maximum value of is less than 1/5. The lower limit is not particularly limited, but may be set to ⅕ or more from the above range. However, the two-fifths or more may be considered to be substantially the manufacturing limit or more.

Next, HW = 0.56 mm, HP = 2 m
m, Lw = 0.16 mm, S = 0.08 mm (2 × Lw
FIG. 7 shows the frequency characteristic of the transmission loss (α) measured using the open area ratio (H / HP) as a parameter for the transmission line of + S = 0.40 mm). According to this figure, as the open area ratio (H / HP) is increased, the transmission loss (α)
It can be seen that can be reduced.

Next, HP = 2 mm, open area ratio = 50% (H
= M), Lw = 0.16 mm, S = 0.08 mm (2 ×
Transmission loss (α) measured with the aperture width (HW) as a parameter for the transmission line Lw + S = 0.40 mm)
FIG. 8 shows the frequency characteristics of the. From HW = 0.40mm,
It can be seen that the transmission loss (α) under the conditions of HW = 0.56 mm and HW = 0.72 mm is small. From this result, it is understood that the transmission loss (α) can be sufficiently reduced if HW ≧ 0.56 at least. Therefore,
Since 0.56 = (2 × Lw + S + 0.16 mm), the sum of the conductor width (Lw) and the conductor interval (S) is 0.16 m.
It can be seen that the transmission loss (α) can be sufficiently reduced by setting the aperture width (HW) equal to or larger than the value obtained by adding m. The value of 0.16 mm is not affected by the width of the stainless plate 30 and the like. Needless to say, the opening width (HW) is narrower than the width of the stainless plate 30.

Based on the results shown in FIGS. 5 to 8, an examination will be conducted under two conditions.

Condition A: Lw = 0.16 mm, S = 0.0
8 mm, opening width (Hw) = 2 × Lw + S + 0.16 mm
= 0.56 mm, and the opening pitch (HP) is 2 mm ~
The open area dependency of the characteristic impedance was evaluated in the range of 30 mm.

Condition B: Lw = 0.08 mm, S = 0.0
8 mm, opening width (Hw) = 2 × Lw + S + 0.16 mm
= 0.40 mm, and the opening pitch (HP) is 2 mm to 3
The open area dependency of the characteristic impedance was evaluated in the range of 0 mm.

As a reference, the holes 33 are formed in the stainless steel plate 30.
The characteristic impedance of the transmission line that cannot be opened (aperture ratio = 0%) is taken. When the reference characteristic impedance is (Zo ′), the reference characteristic impedance (Z
o ′) is 44.8Ω, and the reference characteristic impedance (Zo ′) under condition B is 67.3Ω. Then, a transmission line in which a hole 33 is formed in the stainless plate 30 (aperture ratio>
When the characteristic impedance of 0) is (Zo), the increase (ΔZo) of the characteristic impedance due to the holes made in the stainless steel plate is obtained by ΔZo = Zo−Zo ′ (Equation 4). Therefore, the relationship between the increase in characteristic impedance (ΔZo) with respect to the open area ratio (H / HP) is shown in FIG. Porosity (H
/ HP) increases, the characteristic impedance increases, and the rate of increase does not depend on the line width and is almost the same. Also,
Even if the aperture pitch (HP) is changed, the characteristic impedance changes only slightly.

Therefore, in order to obtain the stainless steel plate aperture ratio of the line having the desired characteristic impedance, first, in order to obtain the relation of the characteristic impedance to the aperture ratio (H / HP), the stainless steel plate 30 is not perforated. Characteristic impedance of transmission line (reference characteristic impedance Zo ')
And the structure of the line conductor portion is the same, the characteristic impedance Z2 of the transmission line without the stainless plate 30 and the characteristic impedance Z3 of the transmission line with the open area ratio (H / HP) of 50% are obtained, and the open area ratio (H / HP) on the graph of the characteristic impedance with respect to / HP, the relationship of a quadratic curve passing through three points (Zo ', Z2, Z3) is obtained. By using the relationship, a means for obtaining the open area ratio (H / HP) for a desired characteristic impedance is used. The relationship of FIG. 9 is as follows: Increase in characteristic impedance (ΔZo) = 34.805 × (opening rate + 0.
³²⁵³⁾ can be approximated by 2 -3.682. Therefore, the characteristic impedance can be obtained by adding the characteristic impedance at the open area ratio (H / HP) of 0% to the increase in the characteristic impedance.

In the above examination, the hole 33 of the stainless steel plate is represented by a rectangle, and the direction of the rectangle is shown as a right angle (90 °) with respect to the conductor 32. The same effect can be obtained even when the corner is an arc. Moreover, the rectangle and the conductor 32 may be obliquely crossed. However, regardless of the direction of the holes 33, the opening pitch (HP) is represented by a value measured in the conductor 32 direction.

In consideration of the above transmission characteristics, a transmission line structure for securing a transmission band will be obtained.

First, a rectangular wave current is transmitted in the portion of the magnetic disk device using the transmission line. In the magnetic disk device, the rising and falling slopes of the rectangular wave current are important. Therefore, the permissible transmission loss is calculated from the permissible range of rising and falling slopes.

The waveform analysis teaches that how to obtain the waveform that has passed through the line having the transmission loss (α) can be obtained by multiplying the spectrum of the input waveform by the frequency characteristic of the loss. Therefore, let α be the transmission loss at 1 GHz,
And assuming that the transmission loss (α) is proportional to the square of the frequency,
Multiply the rising and falling (tr) rectangular wave spectrum. It is clear from FIGS. 5, 7 and 8 that the line loss (α) is approximately proportional to the square of the frequency. By solving the inverse Fourier transform of the lossy spectrum,
A square wave that suffers loss is required.

As an example, tr = 0.17 ns (nanosecond)
For the rise time of a rectangular wave that has not suffered loss, the ratio of the rise time of the square wave that has suffered loss to the rise time deterioration rate (trRatio), and is calculated in relation to the amount of transmission loss (α) at 1 GHz. It was Figure 1
It shows in 0. Here, if the rise deterioration (trRatio) in a 50 mm line length is allowed up to trRatio ≦ 1.015 (1.5% deterioration allowance) (Equation 5), α ≦ 3 [Np / m] (Equation 6).

If tr is different from the example, for example tr
= 1 for tr degradation 1.015 when = 0.34 ns
The transmission loss (α) at GHz is obtained as follows.

Α (0.34) = α (0.17) × √ (0.34 / 0.17) = 3 × √ (0.34 / 0.17) = 4.2 [Np / m] ( (7) Next, the rise time (t) with respect to the bit time (tbit)
A method of determining r) will be described with reference to FIG.

The recording current waveform at the highest recording frequency is approximated by a sine wave, and the current amplitude is matched with the amplitude including overshoot (30%) in the low frequency current waveform. The rise time (tr ') of the sine wave at that time is the amplitude change time of the sine wave corresponding to the amplitude 10% -90% change that defines the rise time (tr) referred to in the low frequency current. For a sine wave, it is advisable to make it earlier than tr ', as the amplitude decreases with a slower rise. The ratio of the rising time (tr ') of the sine wave to the bit time (tbit) can be obtained as follows.

First, when the amplitude of the sine wave is matched with the amplitude of the low frequency current waveform, the amplitude of the sine wave (2.0) corresponds to the amplitude of the low frequency current (160%). Now, the amplitude of the sine wave corresponding to the amplitude 10% and 90% of the low frequency current waveform is 1
0% amplitude is (-0.5), 90% amplitude is (0.5)
The rotation angle (θt) corresponding to tr ′ is θt = ArcSin (0.5) −ArcSin (−0.5) = π / 3 (Equation 8). The rotation angle (θb) corresponding to 1 bit in the sine wave is θb = π (Equation 9). Therefore, the ratio of tr ′ to tbit is tr ′ / tbit = θt / θb = 1/3 = 0.33 (Equation 10). Further, by passing even the fifth harmonic component, the rise time at the highest recording frequency is intended to be shortened as described above. Further, by ensuring that the rise time (tr ') of the approximate sine wave is less than or equal to the rise time (tr) of the low frequency current, the current amplitude at the highest recording frequency is guaranteed.

Therefore, the transmission pass band is set to 5 times the maximum recording frequency, and the rising time (tr) is set to 33% or less of the bit time (tbit).

As an example, a line structure of a recording system having a recording speed of 2 Gbps, a characteristic impedance of 80Ω and a line length of 50 mm will be obtained. The characteristic impedance is determined from the viewpoint of impedance matching, and 80Ω which is often used in this embodiment is used as an example.

When tbit is calculated from 2 Gbps, tbit = 1 / (2 × 10 ⁹ ) = 0.5 [ns] (Equation 11) is obtained. Therefore, the rise time (tr) is tr = tbit × 0.33 = 0.17 [ns] (Equation 12). If the deterioration ratio of the rise time (tr) is 1.015, the transmission loss (α) is 3.0 Np / m (1 GHz). The transmission band (BWw) is: BWw = 5 × maximum frequency = 5 × (1 / (2 × tbit)) = 5 × (1 / (2 × 0.5 [ns])) = 5 [GHz] 13).

Therefore, a line structure having a characteristic impedance of 80Ω, a transmission loss (α) of 3.0 Np / m (1 GHz) or less, and a transmission characteristic of a transmission band of 5 GHz or more should be obtained.

The relationship of the transmission loss (α) to the characteristic impedance (Zo) using the line structure as a parameter, including the above-mentioned characteristics, is summarized in FIGS. Figure 12
The relationship when a line is formed by a layer forming material having a conductor thickness (tCu) of 0.018 mm and a distance between stainless steel and a conductor (tBASE) of 0.018 mm is shown. FIG. 13 shows a relationship when a line is formed by a layer forming material having a conductor thickness (tCu) of 0.010 mm and a distance between stainless steel and a conductor (tBASE) of 0.010 mm.

With reference to FIG. 12, characteristic impedance 80
When the line structure at the intersection of Ω and the transmission loss (α) with 3.0 Np / m is obtained, the line width (Lw) = 0.08 mm, the line interval (S) = 0.08 mm, and the open area ratio (H / HP) = 3
It will be 0%. From the above results, the opening width (Hw) is Hw = 2 × Lw + S + 0.16 = 2 × 0.08 + 0.08 + 0.16 = 0.40 [mm] (Equation 14). On the other hand, the aperture pitch (HP) is obtained by the ratio between the transmission band and the propagation speed as described above.

Hp = (λmax / 5) (Equation 15) Substituting λmax = Vp / BWw (Equation 16) into the above equation, Hp = Vp / (5 × BWw) = 1.7 × 10 ⁸ / (5 ×) 5 × 10 ⁹ ) = 6.8 [mm] (Equation 17).

Therefore, the aperture length (H) is H = Hp x porosity = 6.8 × 0.30 = 2.0 [mm] (Equation 18) Becomes

The transmission band is determined by the data transfer rate specification of the disk device, and the propagation rate is determined by the transmission line structure. Generally, as the open area ratio (H / HP) increases, the propagation speed increases. Here, in order to take a safety measure, the propagation velocity at an aperture ratio (H / HP) of 0% is used.

Therefore, referring to the above-mentioned target point, the target range is defined as transmission loss (α) ≦ 3NP / m and characteristic impedance (Zo) = 75Ω to 85Ω. The line structure corresponding to the target range is as follows. Line width (Lw) is
Lw = 0.12 mm to 0.08 mm, conductor spacing (S) =
0.08 mm, open area ratio (H / HP) = 30% to 95%. Similarly, the aperture width (Hw) is Hw = 2 × Lw + S + 0.16 = (2 × 0.08 + 0.08 + 0.16) to (2 × 0.12 + 0.08 + 0.16) = 0.40-0. The range is 48 [mm] (Equation 19).

On the other hand, the opening pitch (HP) is Hp = Vp / (5 × BWw) = 1.7 × 10 ⁸ / (5 × 5 × 10 ⁹ ) = 6.8 [mm] (number) as described above. 20).

Therefore, the aperture length (H) is H = HP x porosity = (6.8 x 0.30) to (6.8 x 0.95) = 2.0 to 6.5 [mm] (Equation 21) It becomes the range of.

The above results show that the conductor film thickness (tCu) is 18
The distance (tBASE) between the micrometer and the conductor 32 and the stainless steel plate 30 is 18 micrometers. The same relationship as in FIG. 12 can be obtained with the conductor 32 and the stainless steel plate 30 having different intervals and with the conductor film having different thickness. Based on these results, the above study is performed for each line condition, and a line suitable for the disk device specifications is selected.

For a transmission line made of a layer forming material different from that shown in FIG. 12, for example, the conductor film thickness (tCu) = 10 micrometers, the distance between the conductor and the stainless steel plate (tBASE).
= 10 micrometer layer forming material, characteristic impedance 80Ω, transmission loss 3.0 Np / m or less, transmission band 5
Consider a line structure having a transmission characteristic of GHz or higher. FIG.
An examination using the relationship diagram between the characteristic impedance of 1 and the transmission loss (α) revealed that no solution satisfying the above characteristics was obtained. Therefore, it is necessary to widen the gap between the conductor and the stainless steel plate, and it can be understood that the transmission loss (α) can be reduced by this.

FIG. 14 shows a line structure for satisfying the line characteristics for each condition of the conductor film thickness and the distance between the conductor and the stainless steel plate. From the table, the distance between the stainless steel and the conductor (tBA
A solution can be found with a larger SE (tBASE = 0.018 mm), but a smaller tBASE (tBASE).
= 0.01 mm), no solution can be obtained.

In the above embodiment, the case where the present invention is applied to the magnetic disk device has been described. However, since the main feature of the present invention is the signal transmission line, the present invention is not limited to the magnetic disk device, and is not limited to the optical disk device or the optical disk device. It goes without saying that the present invention can be applied not only to the magneto-optical disk device but also to any device provided with a signal transmission line.

[0068]

According to the present invention, the pitch of the stainless steel plate holes for adjusting the characteristic impedance of the transmission line is related to the transmission band, and the open area ratio also affects the transmission loss. As a result, the transmission impedance of the transmission line can be kept low and the characteristic impedance can be adjusted while ensuring the required transmission band.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a transmission line of the present invention.

FIG. 2 is a diagram showing an outline of a magnetic disk device.

FIG. 3 is an enlarged view of an arm tip portion on which an R / W IC (preamplifier) is mounted.

FIG. 4 is an explanatory diagram of a transmission characteristic evaluation method.

FIG. 5 is a diagram showing frequency characteristics of transmission loss with the opening pitch of stainless plate holes as a parameter.

FIG. 6 is a diagram showing the relationship between the minimum transmission band (maximum wavelength) and the aperture pitch.

FIG. 7 is a diagram showing frequency characteristics of transmission loss with a porosity as a parameter.

FIG. 8 is a diagram showing frequency characteristics of transmission loss with the aperture width as a parameter.

FIG. 9 is a diagram showing a relationship diagram between a porosity and a characteristic impedance change amount.

FIG. 10 is a diagram showing rectangular wave rise time deterioration characteristics due to line loss.

FIG. 11 is a diagram for explaining a recording current rise time.

FIG. 12 is a diagram showing a relationship between characteristic impedance and transmission loss for each line condition.

FIG. 13 is a diagram showing a relationship between characteristic impedance and transmission loss for each line condition.

FIG. 14 is a diagram showing a line structure satisfying transmission characteristics for each material condition.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Head disk assembly (HDA), 11 ... Recording / reproducing control circuit, 12 ... Spindle part, 13 ... Magnetic recording medium, 14 ... Magnetic head, 15 ... Carriage part, 16 ...
Flexible Printed Circuits (FPC),
17 ... Voice coil motor (VCM), 18 ... Arm,
19 ... Suspension, 20 ... R / W-IC, 21 ... Relay line, 22 ... Signal processing LSI, 23 ... Hard disk drive control (HDControl), 24 ... External interface, 25 ... Connector, 30 ... Stainless plate, 31 ... Insulation layer , 32 ... Conductor, 33 ... Stainless plate hole, 34 ... Rotation declination (θ), 35 ... Transmission loss (α).

Claims (7)

[Claims] 1. A signal transmission line comprising a conductor for transmitting a differential signal and a metal body sandwiching the conductor and an insulator, wherein the metal body is 2 mm or less in parallel with the conductor. Signal transmission line with holes provided at the pitch. 2. A signal transmission line comprising at least two conductors for transmitting a differential signal, and a metal body provided sandwiching these conductors and an insulator, the width of the conductors and the width of these conductors. A signal transmission line in which the metal body is provided with a hole having a width of a value obtained by adding 0.16 mm or more to the sum of the intervals. 3. A signal transmission line comprising a conductor for transmitting a differential signal and a metal body provided with the conductor and an insulator sandwiched therebetween, wherein the signal transmission line has a length of 5 minutes with respect to the wavelength of the maximum frequency of the transmission band. Signal transmission line in which holes are provided in the metal body in a direction parallel to the conductor at a pitch of 1 or less. 4. A suspension comprising a spring portion made of a stainless material and a line for transmitting a signal from a head to an amplifier on the spring portion, the line being a conductor for transmitting the information. , 2 holes are provided in a direction parallel to the conductor by sandwiching the conductor and the insulator.
A suspension provided with a metal body provided at a pitch of mm or less. 5. A suspension comprising a spring portion formed of a stainless material and a line for transmitting a signal from a head to an amplifier on the spring portion, wherein the line is at least 2 for transmitting the signal. Hole having a width of a value obtained by adding 0.16 mm or more to the sum of the width of the conductor and the distance between the conductors in a direction parallel to the conductor, the hole being provided between the conductor and the insulator. A suspension provided with a metal body provided with. 6. A suspension comprising a spring portion formed of a stainless material and a line for transmitting a signal from a head to an amplifier on the spring portion, the line being a conductor for transmitting the signal. A metal body provided with holes in a direction parallel to the conductor at a pitch of ⅕ or less with respect to the wavelength of the maximum frequency of the transmission band of the signal provided with the conductor and the insulator interposed therebetween. suspension. 7. A recording medium for recording information, a spindle motor for rotating the recording medium, a head for recording information on the recording medium and reading the recorded information, and a suspension having the head mounted thereon. A magnetic disk device comprising: an arm to which the suspension is attached; a line for transmitting the information to the head along the arm; and a voice coil motor for positioning the head on the recording medium. Is a recording device including a conductor for transmitting the information, and a metal body having holes provided at a pitch of 2 mm or less and sandwiching the conductor and the insulator in parallel with the conductor.