JP3580893B2 - Suspension wiring board for magnetic head - Google Patents

Description

[0001]
[Industrial applications]
The present invention ha - relates de suspension wiring board for a magnetic head of the disk drive.
[0002]
[Prior art]
In a wiring board used for transmitting high-speed digital signals, it is necessary to prevent electromagnetic waves from radiating from the signal transmission conductor to the outside, or to prevent external electromagnetic waves from entering the signal transmission conductor (ie, It is required to prevent crosstalk between signal transmission conductors.
If a magnetic head is attached to the tip and a crosstalk or electromagnetic wave noise occurs in the magnetic head suspension wiring board that connects the magnetic head to the hard disk drive, data is read from the magnetic disk. If an error occurs in writing and a harmonic component generated from a high-speed digital signal is radiated as electromagnetic noise, it causes a malfunction of the hard disk drive itself due to an induction failure. In this case, it is necessary to suppress the pressure and crosstalk.
[0003]
Recently, in the above-described suspension wiring board for a magnetic head, there has been a shift from a wire system to a printed circuit system, and a pair of conductors composed of a signal transmission conductor and a ground conductor has been placed on the same insulating layer surface (and therefore on the same plane). ). According to this conductor path structure, the electromagnetic field generated from the signal transmission conductor can be relatively well confined in the space between the signal transmission conductor and the ground conductor forming a pair with the signal transmission conductor. Since the emission range of the electromagnetic field can be suppressed to a small value, crosstalk and electromagnetic interference to the outside can be considerably suppressed.
[0004]
[Problems to be solved by the invention]
However, with this paired conductor configuration, it cannot be expected to prevent external electromagnetic waves from entering the signal transmission conductor.
In the above-mentioned suspension wiring board for a magnetic head of a hard disk drive, a levitation force generated by an airflow caused by rotation of the magnetic disk and a bending reaction force of the suspension are balanced by a predetermined levitation amount, thereby making the magnetic head a magnetic disk. A high-rigidity metal plate is laminated on the back surface of the wiring board so as to bring the predetermined bending rigidity close to the wiring board.
[0005]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a suspension wiring board for a magnetic head of a hard disk drive which can effectively prevent the invasion of an external electromagnetic wave by cooperating with the high-rigidity metal plate, suppress crosstalk and prevent an electromagnetic interference. It is an object of the present invention to provide a printed wiring board which can effectively prevent radiation of the printed wiring board.
[0006]
[Means for Solving the Problems]
The magnetic head suspension wiring board according to the present invention has a plurality of paired conductors formed of pairs of a signal transmission conductor and a ground conductor, and the plurality of pairs of conductors are provided on a high-rigidity metal plate on the back surface with an insulating layer interposed therebetween. A signal transmission conductor among the conductors is disposed, and a ground conductor among the plurality of paired conductors is placed on the signal transmission conductor group via an insulation layer different from the insulation layer on the signal transmission conductor group. The same pair of signal transmission conductors are disposed so as to sandwich the same pair of signal transmission conductors between the conductor conductor and the high-rigidity metal plate, and it is desirable that the width of the ground conductor be wider than the width of the signal transmission conductor.
[0007]
Hereinafter, the configuration of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory sectional view showing a suspension board for a magnetic head according to the present invention.
In FIG. 1, reference numeral 1 denotes a high-rigidity metal plate. Numeral 2 denotes a pair conductor composed of a signal transmission conductor 21 and a ground conductor 22. The signal transmission conductor 21 is formed between the ground conductor 22 and the high-rigidity metal plate 1 from above and below via insulating layers 3 and 4. Sandwiched between the high-rigidity metal plate 1 and the insulating layer 3, between the insulating layer 3 and the signal transmission conductor 21, between the insulating layer 3 and the insulating layer 4, and between the insulating layer 4 and the ground conductor. 22 is bonded and integrated.
The width of the ground conductor 22 is at least equal to the width of the signal transmission conductor 21, and is preferably wider than the width of the signal transmission conductor 21.
[0008]
A magnetic head is attached to the tip of the wiring board, and is bent by a levitation force generated by an air flow accompanying the rotation of the magnetic disk to bring the magnetic head close to the magnetic disk.
The high-rigidity metal plate 1 is provided to impart bending rigidity required for the operation to the printed wiring board. The high-rigidity metal plate has a thickness of 5 to 100 μm, preferably a thickness of 10 to 50 stainless steel. Can be used, and the component ratio of iron, nickel, chromium and the like is not particularly limited.
[0009]
As a material of the signal transmission conductor 21 and the ground conductor 22, metals such as copper, chromium, nickel, titanium, aluminum, gold, and silver, or alloys of these metals can be used. Further, a multilayer structure can be formed by using two or more of these metals. The thickness of each of the signal transmission conductor 21 and the ground conductor 22 is 0.1 to 100 μm, preferably 1 to 50 μm, and the width of the conductor is usually 5 to 20 times the thickness.
The material of the insulating layers 3 and 4 is not particularly limited, and for example, a synthetic resin such as a polyimide resin, a polyester resin, and a fluororesin can be used. In order to form a negative electrode, the resin may be provided with photosensitivity by adding or blending a photosensitive agent or the like. The thickness of each of these insulating layers 3 and 4 is 0.5 to 100 μm, preferably 1 to 50 μm.
[0010]
The magnetic head suspension wiring board can be manufactured, for example, as follows.
That is, in FIG. 1, first, the insulating layer 3 is formed on one surface of the high-rigidity metal plate 1. The insulating layer 3 is formed by applying a resin to one surface of the high-rigidity metal plate 1 and performing a heat treatment as necessary, or by attaching a resin film to one surface of the high-rigidity metal plate 1 with an adhesive. Etc. can be used.
Next, a conductor layer is formed on the insulating layer 3 by a vacuum deposition method or the like, and the signal transmission conductors 21, 21,... Of a predetermined pattern are formed by photolithography.
Next, the insulating layer 4 is formed so as to cover the upper and side surfaces of the signal transmission conductors 21, 21,. For forming the insulating layer 4, a method of applying a resin and performing a heat treatment as necessary can be used. If necessary, a through hole can be provided from the insulating layer 4 to the insulating layer 3.
Next, a conductor layer is formed on the insulating layer 4 by a vacuum evaporation method or the like, and the ground conductors 22, 22,... Are formed by photolithography with a predetermined pattern covering the signal transmission conductors 21, 21,. Then, the production of the printed wiring board is completed.
[0011]
According to this method of manufacturing a suspension wiring board for a magnetic head, after forming the signal transmission conductor, a metal foil is laminated on a signal transmission conductor formation surface via an adhesive, and the metal foil is used for signal transmission by photolithography. It can also be formed by etching a predetermined pattern of the ground conductor for covering the conductor.
If electrical contact between the ground conductor and an electric circuit in the hard disk becomes a problem, an insulating cover coat is provided on the ground conductor.
[0012]
[Action]
The high-rigidity metal plate 1 has a lower conductivity than the conductor 22 for the ground conductor, but has a conductance comparable to that of the conductor 22 for the ground conductor because of its large cross-sectional area. Thus, the signal transmission conductor 21 is sandwiched between the ground conductor 22 and the high-rigidity metal plate 1, and the signal transmission conductor 21 is disposed on each of the ground conductor 22 and the high-rigidity metal plate 1. Since they are sufficiently close, it is possible to prevent foreign electromagnetic waves from entering the signal transmission conductor 21 well.
In addition, since the pair of signal transmission conductors 21 and the ground conductor 22 are arranged close to each other without shifting in the width direction, the pair of conductors 21-22 for the electromagnetic field generated from the signal transmission conductor 21 are disposed. The protrusion from the space is suppressed to a small extent, and the crossing of the generated electromagnetic field to the adjacent signal transmission conductor and the crossing to other electric circuit parts can be suppressed well.
Accordingly, it is possible to favorably suppress electromagnetic wave shielding and crosstalk, and the effect of (1) can be confirmed also by comparing the following example with a comparative example.
[0013]
【Example】
[Example 1]
A polyimide precursor (3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride as a tetracarboxylic acid component and a p-phenylenediamine as a diamine component) on one side of a stainless steel plate (SUS304) having a thickness of 30 μm. Was applied by spin coating, and this coating layer was heated at 380 ° C. for 1 hour under a nitrogen gas atmosphere to form an insulating layer having a thickness of 10 μm. Next, a copper layer having a thickness of 5 μm is laminated on the insulating layer by a vacuum deposition method, and the copper layer is etched using a ferric chloride solution, and two signal transmission conductors having a width of 50 μm are arranged at intervals of 50 μm. Formed. A polyimide precursor is applied on the signal transmission conductor forming surface by spin coating in the same manner as described above, and the applied layer is heated at 380 ° C. for 1 hour in a nitrogen gas atmosphere to have a thickness of 10 μm. An insulating layer was formed, and a 5 μm thick copper layer was laminated on the insulating layer by a vacuum evaporation method. Then, the copper layer was etched using a ferric chloride solution to form two ground conductors having a width of 50 μm, which were positioned immediately above the signal transmission conductors (accordingly, the interval was 50 μm).
[0014]
[Example 2]
Example 1 was the same as Example 1 except that the width of the ground conductor was set to 70 μm and the interval between the ground conductors was set to 30 μm.
[0015]
(Comparative example)
A polyimide precursor is applied on one side of a stainless steel plate (SUS304) having a thickness of 30 μm by spin coating, and this coating layer is heated at 380 ° C. for 1 hour under a nitrogen gas atmosphere to form an insulation layer having a thickness of 10 μm. Was formed. Next, a copper layer having a thickness of 5 μm was laminated on the insulating layer by a vacuum evaporation method, and the copper layer was etched using a ferric chloride solution to form four conductors having a width of 50 μm at intervals of 50 μm. Two pairs of conductors were formed on the same surface in an arrangement of a conductor for ground conductor, a conductor for signal transmission, a conductor for signal transmission, and a conductor for ground conductor.
[0016]
The crosstalk coefficient of these examples and comparative examples was measured using a pulse generator and a digital oscilloscope. As a result, 0.002 was obtained for Example 1 and 0.001 for Example 2. It was 0.01 in the comparative example product, and the example product was much better than the comparative example product.
From the measurement results, according to the present invention, the electromagnetic field generated from the signal transmission conductor can be confined between the ground conductor and the high-rigidity metal plate to sufficiently prevent radiation to the outside. It can be confirmed that the arc suppression performance and the electromagnetic wave shielding performance can be guaranteed.
[0017]
【The invention's effect】
According to the suspension wiring board for a magnetic head according to the present invention, the electromagnetic field generated from the signal transmission conductor can be confined between the ground conductor and the high-rigidity metal plate to prevent radiation to the outside, and Since the signal transmission conductor is compactly confined between the ground conductor and the high-rigidity metal plate, it is possible to prevent the invasion of the external electromagnetic field into the signal transmission conductor, so that the excellent electromagnetic shielding performance and Crosstalk suppression performance can be guaranteed.
[0018]
Further, since the signal transmission conductor and the ground conductor, which form a pair conductor, are arranged vertically, the wiring space can be reduced as compared with the conventional example in which the conductors are arranged on the same plane. Since the metal plate is provided on the back surface side of the conductor for use with an insulating layer interposed therebetween, the transmission line has a stripline structure, and there is an advantage that impedance matching can be easily performed.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a suspension wiring board for a magnetic head according to the present invention in cross section.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High rigid metal plate 2 Pair conductor 21 Signal transmission conductor 22 Ground conductor 3 Insulation layer 4 Insulation layer

Claims (2)

A plurality of paired conductors each comprising a pair of a signal transmission conductor and a ground conductor are provided, and the signal transmission conductor among the plurality of paired conductors is disposed on a high-rigidity metal plate on the back surface via an insulating layer. On these signal transmission conductor groups, the ground conductor of the plurality of paired conductors is the same as the ground conductor and the high-rigidity metal plate via the insulating layer different from the insulating layer. A suspension wiring board for a magnetic head, comprising a pair of signal transmission conductors sandwiched therebetween . The suspension wiring board for a magnetic head according to claim 1, wherein the width of the ground conductor is wider than the width of the signal transmission conductor.

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