JP2003204130A - Flexible printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed circuit board for a head suspension assembly that can suppress the breakdown of a magnetic head. <P>SOLUTION: This flexible printed circuit board 1 directly relays a magnetic head placed on a suspension and the connecting end section of the base-side end section of a carriage arm to each other in the head suspension assembly of a magnetic disk device. This circuit board 1 comprises a laminate 11 composed of a base layer 12, a conductor circuit 13 formed on the layer 12, a cover layer 14 coating the circuit 13, and a conductive polymer layer 15 formed at least on the underside of the base layer 12 and the upside of the cover layer 14; and a stainless steel layer 16 stuck to the laminate 11 from the underside of the base layer 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed circuit board used in a head suspension assembly of a magnetic disk device. More specifically, the present invention relates to a flexible printed circuit board that is capable of sufficiently preventing electrostatic breakdown of a magnetic head even when a head suspension assembly is formed using a high-performance magnetic head and has high productivity.

[0002]

2. Description of the Related Art At present, a magnetic disk device widely used as a storage device is generally a magnetic disk as a recording medium, a spindle motor for rotating the magnetic disk, a head suspension assembly including a magnetic head, and The main components are a carriage arm that supports the head suspension assembly, a servo device that moves the carriage arm, and a board unit that processes electrical signals.

The head suspension assembly includes a magnetic head for reproducing and recording information, and a metal plate suspension for mounting the magnetic head.
It consists of a flexible printed circuit board that is connected to the suspension at one end. In the head suspension assembly, fixed wiring is formed on the suspension in advance, the pad portion is exposed at the end of the fixed wiring opposite to the magnetic head, and the pad portion is formed on a flexible printed circuit board. By connecting with a circuit, it relays between a magnetic head and a substrate unit.

A problem in the head suspension assembly having such a structure is electrostatic discharge (ESD) of the magnetic head. In particular, a flexible printed circuit board made of an insulating material such as plastic in order to insulate the conductor circuits formed inside the flexible printed circuit board is very likely to be charged due to friction during handling, and the charged flexible printed circuit board is magnetically affected. When the head is attached, a rapid discharge is generated toward the magnetic head, which causes electrostatic breakdown of the magnetic head. The electrostatic breakdown includes breakdown of the insulating film of the magnetic head (hard ESD) and deterioration of performance of the magnetic head (soft E).
SD) is mentioned, but both are not preferable, and they are a major cause of lowering the yield of manufacturing the head suspension assembly. This problem is especially caused by an MR (magnetoresistive) head having a thin insulating film and a GMR (gi
ant magnetoresistive) head is a big problem.

As a technique for preventing electrostatic breakdown of a magnetic head, there is a technique disclosed in Japanese Patent Laid-Open No. 11-250434. In a head suspension assembly for a magnetic disk device disclosed in this publication, a flexible printed circuit board that relays a magnetic head and a board unit covers a base layer, a conductor pattern formed on the base layer, and a conductor pattern. It is characterized by comprising a cover layer and a conductive layer formed on the cover layer. By adopting the flexible printed circuit board having such a structure, triboelectrified static electricity is discharged through the conductive layer, thereby preventing electrostatic breakdown.

[0006]

In recent years, as the recording density of magnetic disk devices has increased, it has become necessary to improve the performance of magnetic heads, in particular to increase the reproduction output. As a magnetic head capable of generating a larger reproduction output than the existing MR head and GMR head, a GMR head using a specular spin valve film has been proposed. However, since such a high performance magnetic head uses an extremely thin insulating film, it is much more likely to be electrostatically damaged than a conventional magnetic head.

In the conventional head suspension assembly, first, a fixed wiring having a structure in which a copper foil layer is generally sandwiched between polyimide layers is provided between the magnetic head and the suspension side end of the flexible printed circuit board. The conductor circuit formed in the flexible printed circuit board relays between the suspension side end of the flexible printed circuit board and the board unit, that is, the magnetic head and the board unit have a total of two. It was relayed by one member. Therefore, it is necessary to connect the fixed wiring and the conductor circuit in the flexible printed circuit board by soldering or the like when manufacturing the head suspension assembly. However, the insulating film of a high-performance magnetic head used in a magnetic disk device that achieves a recording density of 100 Gbits / square inch is so static that it can be electrostatically destroyed even by minute static electricity generated during such connection work. Is expected to be sensitive to.

As a flexible printed circuit board capable of solving the above problems, a magnetic head mounted on a suspension and a connecting end of a carriage arm base end are directly relayed to each other to form a stainless steel layer and the stainless steel layer. A base layer formed on the base layer, a conductor circuit formed on the base layer, a cover layer covering the conductor circuit, and a conductive layer formed at least below the stainless steel layer and above the cover layer. Flexible printed circuit boards comprising a polymer layer have been proposed. By providing the conductive polymer layer on at least two surfaces of the flexible printed circuit board, static electricity generated by friction can be easily discharged. Also, unlike the conventional head suspension assembly, there is no relay between the magnetic head and the board unit by two members, so the work of connecting the fixed wiring that may cause static electricity and the conductor circuit in the flexible printed circuit board. Is omitted. The flexible printed circuit board having such a structure enables the use of a magnetic head which is extremely susceptible to electrostatic breakdown, but has a drawback of low productivity. That is, the manufacture of the flexible printed circuit board starts with forming a base layer on the stainless steel layer, and the manufacturing process thereafter has to deal with a laminate including the stainless steel layer. Since the deformation of stainless is irreversible, it is necessary to keep the stainless layer from being deformed. However, since the stainless layer is very thin and easily deformed, handling of the laminate is considerably difficult. Also, for the same reason, the flexible printed circuit board must always be in sheet form throughout the manufacturing process and cannot be folded or reeled.

Therefore, even when a high performance magnetic head is used, it is desired to develop a flexible printed circuit board which can manufacture a head suspension assembly without causing electrostatic damage to the magnetic head and has high productivity. ing.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have established a conductor circuit between a base layer and a cover layer, and at least the lower side of the base layer. And a laminated body in which a conductive polymer layer made of a conductive polymer is formed on the upper side of the cover layer, a stainless layer is attached to the conductive polymer layer on the lower side of the base layer to form a flexible printed circuit board, and By extending the obtained flexible printed circuit board to the magnetic head mounting portion and directly relaying the magnetic head and the substrate unit, discharging static electricity generated by friction during manufacturing through the conductive polymer layer, And the connection between the fixed wiring and the conductor circuit in the flexible printed circuit board, which were indispensable in the manufacture of conventional head suspension assemblies. While allowing the omission, in the production of flexible printed circuit boards, the laminate can be processed in a form peculiar to the flexible film until the stainless layer is adhered, and as a result, the conventional magnetic head can be used. The present invention has been found that a head suspension assembly capable of sufficiently suppressing the destruction of the magnetic head and the performance deterioration due to static electricity can be provided with high productivity even when a high-performance magnetic head that is weak against electrostatic breakdown is used. Was completed.

Therefore, the present invention provides a flexible printed circuit board for directly relaying a magnetic head mounted on a suspension and a connecting end of a carriage arm base end in a head suspension assembly of a magnetic disk device. A flexible printed circuit board, a base layer, a conductor circuit formed on the base layer,
A cover layer covering the conductor circuit, and a laminated body composed of at least a conductive polymer layer formed on the lower side of the base layer and on the upper side of the cover layer, and attached to the laminated body from the lower side of the base layer. And a flexible stainless steel layer.

In the flexible printed circuit board, if both the base layer and the cover layer are made of a polyimide resin or an epoxy resin, and the conductive polymer layer is made of a polypyrrole resin,
Due to the high miscibility of the polyimide resin or epoxy resin with the polypyrrole resin, the polypyrrole resin penetrates into the polyimide resin or epoxy resin when forming the conductive polymer layer, and as a result, the adhesion of the conductive polymer layer is improved. To do. Therefore, the present invention also relates to the flexible printed circuit board, wherein the base layer and the cover layer are made of a polyimide resin or an epoxy resin, and the conductive polymer layer is made of a polypyrrole resin.

From the viewpoint of giving the necessary strength to the conductive polymer layer, the thickness of the conductive polymer layer is 0.01 to 0.
It is preferably 1 μm, particularly preferably 0.03 to 0.05 μm. If the thickness exceeds 0.1 μm, the weight of the suspension itself increases, which may adversely affect the flying performance of the magnetic head. From the viewpoint that the flexible printed circuit board has sufficient conductivity to release static electricity, the surface resistivity of the flexible printed circuit board is preferably 10 ⁵ to 10 ¹¹ Ω, particularly 10 ⁶ to 10 ⁸ Ω. Therefore, the present invention
The conductive polymer layer has a thickness of 0.03 to 0.05.
characterized in that it is a [mu] m, wherein the flexible printed circuit board, and the surface resistivity is 10 ⁶ to 10 ⁸ Omega, also relates to the flexible printed circuit board.

The present invention further comprises forming a base layer, forming a conductor circuit on the base layer, forming a cover layer on the base layer to cover the conductor circuit, and at least the base layer. The present invention relates to a method for producing a flexible printed circuit board, which comprises forming a conductive polymer layer on a lower side and an upper side of the cover layer to form a laminated body, and adhering the laminated body to a stainless layer.

It is preferable to use an epoxy adhesive for the attachment. Therefore, the present invention also relates to the above-mentioned manufacturing method, characterized in that an epoxy-based adhesive is used for the attachment.

The flexible printed circuit board of the present invention has conductive polymer layers on at least two sides of the lower side of the base layer and the upper side of the cover layer. Therefore, the generated static electricity is very easily discharged as compared with one having a conductive polymer layer on only one side, and as a result, it is possible to significantly reduce the charging potential of the flexible printed circuit board. . Further, in the case of imparting the same conductivity, the thickness of the conductive polymer layer provided on the flexible printed circuit board of the present invention can be about half that of the conductive polymer layer having only one surface.

The flexible printed circuit board of the present invention extends to the magnetic head mounting portion of the suspension and directly relays the magnetic head and the circuit unit. That is, the flexible printed circuit board of the present invention,
One member plays the role of the fixed wiring and the relay flexible printed circuit board in the conventional head suspension assembly. By using the flexible printed circuit board having such a configuration, it is possible to omit the connection work between the fixed wiring and the flexible printed circuit board when manufacturing the head suspension assembly,
It is possible to prevent electrostatic breakdown of the magnetic head due to static electricity generated by the work.

In the flexible printed circuit board of the present invention, a conductive polymer layer is used to impart conductivity.
Since the conductive polymer layer is formed of a conductive polymer and does not contain an ionic substance having a low molecular weight, the ionic substance does not penetrate into the base layer, the cover layer and the like to be contaminated, and low humidity is sufficient. It can exhibit conductivity.

The conductive polymer layer provided on the flexible printed circuit board of the present invention may be formed at least on the upper side of the cover layer and the lower side of the base layer, or may be formed on the entire periphery thereof. Therefore, in forming the conductive polymer layer, for example, a conductor circuit is previously provided between the base layer and the cover layer, and the monomer is polymerized by immersing it in a treatment liquid containing a monomer and an oxidative polymerization agent,
A method of forming a conductive polymer layer on the surfaces of the base layer and the cover layer can be used, and it is not necessary to use a conventional complicated method including a step of applying a monomer and a step of curing the applied monomer.

In the production of the flexible printed circuit board of the present invention, the conductive polymer layer is formed on the surfaces of the base layer and the cover layer, and then the stainless layer is attached.
That is, the laminate including the base layer, the conductor circuit, the cover layer, and the conductive polymer layer has flexibility and can be reversibly deformed until the stainless layer is attached in the final step. By adopting such a so-called flex-on suspension, even if the laminate is very thin and difficult to handle, it can be processed in a form peculiar to a flexible film such as a reel, The productivity of the flexible printed circuit board can be further improved.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a plan view illustrating one embodiment of a head suspension assembly using the flexible printed circuit board of the present invention, and FIG.
2 is a sectional view taken along the line AA ′ of FIG.

Flexible printed circuit board 1 of the present invention
The head suspension assembly a using the is composed of a flexible printed circuit board 1, a magnetic head 2, and a suspension 3. Further, at the end opposite to the side of the flexible printed circuit board 1 connected to the magnetic head 2, a base end side connection end to be connected to a board unit for processing a signal reproduced and recorded by the magnetic head 2. 4 are provided. In the magnetic disk device, the entire head suspension assembly a is supported by the carriage arm.

Flexible printed circuit board 1 of the present invention
Has an elongated shape as a whole, and is formed by extending the suspension 3 to the magnetic head 2. this is,
This is in contrast to the conventional head suspension assembly in which the relay flexible printed circuit board is provided only up to the portion in contact with the suspension. The flexible printed circuit board 1 is attached to the suspension 3 by, for example, spot welding, adhesion, or preferably ultrasonic fusion.

The magnetic head 2 is a magnetic head for reproducing information recorded on the magnetic disk in the magnetic disk device and / or for recording information on the magnetic disk, and usually has four electrodes (not shown). It is provided. Further, any type of magnetic head 2 can be adopted, for example, an MR head and a GMR head, and a G using a specular spin valve film.
It can be an MR head or the like.

The suspension 3 is a deformable plate-like member that supports the magnetic head 2 at its tip, and is generally made of a metal plate having a thickness of about 60 to 70 μm. During operation of the magnetic disk device, the magnetic head 2 levitates from the magnetic disk at a constant interval and performs recording / reproduction in a state of non-contact with the magnetic disk. It is possible to maintain the interval at which the 2 floats at a predetermined amount.

The flexible printed circuit board 1 is directly connected to the magnetic head 2 at one end, and a base end side connecting end 4 is provided at the other end. Thus, the flexible printed circuit board 1 directly relays the magnetic head 2 and the substrate unit, so that the fixed wiring and the relay flexible printed circuit board in the conventional head suspension assembly can be replaced by one member. Therefore, by using the flexible printed circuit board 1 of the present invention, it is possible to omit the connection between the fixed wiring and the conductor circuit in the relay flexible printed circuit board, which is essential when manufacturing the conventional head suspension assembly.

The flexible printed circuit board 1 of the present invention in the embodiment shown in FIGS. 1 and 2 has a base layer 12,
The conductive circuit 13, the cover layer 14, and the laminated body 11 including the conductive polymer layer 15 formed on the entire periphery including the lower side of the base layer 12 and the upper side of the cover layer 14, the stainless layer 16 from the lower side of the base layer 12. Is adhered with an adhesive agent 17.

The base layer 12 is formed of a non-conductive material used as a base layer in a general flexible printed circuit board. Examples of the material include polyvinyl chloride, polystyrene, polymethyl methacrylate,
Polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polyvinylidene chloride, polyvinylidene fluoride, polyimide, polyetherimide,
Examples thereof include polyether sulfone, polyether ketone, polysulfone, polyacrylate, and epoxy resin.

Conductor circuit 13 formed on the base layer 12
Is made of copper, for example, and four electrodes are formed corresponding to the number of electrodes provided on the magnetic head 2.

The cover layer 14 is formed on the base layer after the formation of the conductor circuits 13 in order to prevent the conductor circuits 13 from being exposed to the air to be oxidized or corroded and to insulate the conductor circuits 13 from each other. 12 is formed. At the same time, it can also serve as a solder resist when wiring to the conductor circuit 13. The cover layer 14 is also made of a non-conductive material used in a general flexible printed circuit board, and the example thereof is the same as that of the base layer 12.

The conductive polymer layer 15 surrounds their entire underside, including the underside of the base layer 12 and the overside of the cover layer 14. The conductive polymer layer 15 is composed of an electron-conjugated polymer having conductivity, and is formed, for example, by polymerizing a monomer having a conjugated double bond in its molecular structure and capable of being polymerized by oxidation. A typical example of the monomer is a 5-membered heterocyclic compound, which includes pyrrole, thiophene,
Furan, indole or their derivatives such as N-
Methylindole, 3-methylthiophene, 3-methylfuran, 3-methylindole and the like are preferable. The thickness of the conductive polymer layer 15 is preferably 0.01 to 0.1 μm, particularly preferably 0.03 to 0.05 μm, and the surface resistivity of the flexible printed circuit board 1 is 10 μm.
^The conductive polymer layer 15 is preferably formed so as to have a resistance of ⁵ to 10 ¹¹ Ω, particularly 10 ⁶ to 10 ⁸ Ω.

When the materials of the base layer 12 and the cover layer 14 and the material of the conductive polymer layer 15 are selected so as to be a combination having a large miscibility, the material of the conductive polymer layer 15 is formed at the time of forming the conductive polymer layer 15. Base layer 1
2 and the cover layer 14, and as a result, the adhesion of the conductive polymer layer 15 is improved. Examples of the combination of materials that can achieve this effect include a combination of polyimide or epoxy selected as the material of the base layer 12 and the cover layer 14 and polypyrrole selected as the material of the conductive polymer layer 15.

The stainless layer 16 is a layer for imparting a certain strength to the flexible printed circuit board, and is provided on the conductive polymer layer 15 below the base layer 12. The stainless steel layer 16 is preferably made of a thin stainless steel foil and has a thickness of about 40 to 50 μm, which is thinner than the metal plate used for the suspension 3.

The adhesive 17 is used to adhere the stainless layer 16 to the laminate 11. As the adhesive 17, any kind of adhesive can be used as long as it does not harm each layer constituting the flexible printed circuit board 1. Epoxy adhesives are particularly preferable.

Flexible printed circuit board 1 of the present invention
Is manufactured by forming a laminate 11 including a base layer 12, a conductor circuit 13, a cover layer 14, and a conductive polymer layer 15 in advance, and then attaching a stainless layer 16 to the laminate 11 with an adhesive 17. It can be carried out.

The production of the laminated body 11 starts by forming a conductor circuit 13 having a desired pattern on the base layer 12, preferably by a lithographic method. After forming the conductor circuit 13, the cover layer 14 is formed thereon. A simple method of coating and drying can be used to form the cover layer 14, but the cover layer 14 plays a role of a solder resist, and the cover layer is formed only in a specific range excluding a portion to be a connection end. When it is necessary to form 14, it is formed by a lithographic method. It is also possible to appropriately perform gold plating during these operations.

The conductive polymer layer 15 can be formed, for example, according to the method described in JP-A No. 62-140313. In this method, the base layer 12, the conductor circuit 13, and the cover layer 14 are formed in advance, and the base layer 12, the cover layer 14 and the cover layer 14 are immersed in a treatment liquid containing a monomer capable of forming an electron conjugated polymer and an oxidative polymerization agent to form the base layer 12 and the cover. The conductive polymer layer 15 is formed by polymerizing the monomer on the surface of the layer 14. In this method, in order to reduce the thickness of the conductive polymer layer 15, the monomer concentration in the treatment liquid should be kept low, preferably about 5 × 10 ⁻³ to 1 molar concentration. Further, in order to avoid that the monomer is rapidly polymerized to form a fine particle polymer and the polymer becomes a contamination particle, the polymerization is carried out at a low reaction temperature, for example, -20
It is preferably carried out at a temperature of from 0 to 30 ° C, particularly from 0 to 20 ° C. From the viewpoint of forming a more uniform conductive polymer layer 15 and improving the adhesion of the conductive polymer layer 15, the surface of the base layer 12 and the cover layer 14 is subjected to corona treatment, plasma treatment, etc. before the formation of the conductive polymer layer 15. It is preferable to pretreat.

The above-mentioned forming method of forming the conductive polymer layer 15 by immersing the conductive polymer layer 15 in the treatment liquid is suitable for manufacturing an article in which the conductive polymer layer 15 is provided over the entire periphery like the flexible printed circuit board 1 of the present invention. Is very suitable. Further, it is simpler than a forming method including a step of applying a monomer and a step of curing the applied monomer. In addition to the method of forming the conductive polymer layer 15 in the treatment liquid, a method of contacting the monomer in a gas phase atmosphere and irradiating with active energy to form the conductive polymer layer 15 can also be adopted.

In the flexible printed circuit board 1, the laminated body 11 does not include the stainless layer 16. The laminate 11 can be treated as a normal flexible film, since it does not include the stainless steel layer 16 which is liable to be deformed and whose deformation is irreversible and must be handled with great care. That is, the laminated body 11 can be operated in a reel state like a normal film, and even if the laminated body 11 is very thin, it is relatively easy to handle, and as a result, the flexible print is obtained. Circuit board 1
Productivity will be greatly improved.

The stainless steel layer 16 is attached to the laminated body 11 thus obtained from the lower side of the base layer 12 by an adhesive agent 17. In the manufacture of the flexible printed circuit board 1 shown in FIGS. 1 and 2, the stainless steel layer 16 is provided by pasting the stainless steel layer 16 processed in a predetermined shape on the conductive polymer layer 15. Also,
A flexible printed circuit board can be manufactured by sticking the stainless layer 16 to the laminate 11 and then cutting the both into a predetermined shape. In this case, the conductive polymer layer is formed only on the laminated surface of the flexible printed circuit board. 15 exists, and it does not exist on the side surface.

[0041]

The present invention will be described in more detail by the following examples. However, the examples are for the purpose of illustrating the present invention and are not intended to limit the present invention in any way.

Example 1 Four conductor circuits made of copper were formed on a base layer made of polyimide by a lithography method. After that, a cover layer made of polyimide was formed on the base layer and the conductor circuit. A lithographic method was used to form the cover layer, and the conductor circuit was exposed at an end portion on the substrate unit side to form a connection end portion. 0.1M in a 1L glass beaker
Add 500 ml of potassium peroxodisulfate aqueous solution to 2
The laminate composed of the base layer, the conductor circuit, and the cover layer was immersed while being kept at -3 ° C. Subsequently, 100 mL of a 0.2 M pyrrole aqueous solution was added, and the mixture was stirred at 15 ° C. for 10 minutes to form a conductive polymer layer. A stainless steel foil was attached to the obtained laminate from below the base layer with an epoxy resin. Thus, the total length is about 30 mm and the width is about 1 m.
A flexible printed circuit board of the present invention having a thickness of m and a thickness of about 0.5 mm was manufactured.

Comparative Example 1 Four conductor circuits made of copper were formed on the base layer made of polyimide by the lithography method. Then, a cover layer made of polyimide was formed on the base layer and the conductor circuit. Lithography is used to form the cover layer,
The conductor circuits were exposed at both ends of the base layer. Then, a conductive polymer layer made of polypyrrole was formed only on the cover layer to manufacture a comparative flexible printed circuit board having the same dimensions as in Example 1.

Test Example 1 The flexible printed circuit boards obtained in Example 1 and Comparative Example 1 were subjected to a triboelectrification test. The flexible printed circuit board was rubbed with ceramic tweezers at a distance of 2 cm three times to be charged, and then the amount of charge on the surface of the flexible printed circuit board was measured. The measurements were carried out on 5 different samples each. The results are shown in Table 1.

[Table 1] Table 1 shows that the flexible printed circuit board of Example 1
Compared with the comparative example, it has only about 1/3 the amount of electric charge, indicating that the static electricity generated by friction is discharged more quickly.

Test Example 2 A triboelectrification test was conducted on a head suspension assembly constructed by using the flexible printed circuit boards obtained in Example 1 and Comparative Example 1. First, the resistance value and the peak current value of the magnetic head of the head suspension assembly were measured. Then, the flexible printed circuit board of the head suspension assembly was rubbed twice with ceramic tweezers at a distance of 3 cm to be charged, and then the resistance value and the peak current value of the magnetic head were measured and compared with the values measured before charging. . The measurements were carried out on 5 different samples each. The results are shown in Table 2.

[Table 2] In the head suspension assembly using the flexible printed circuit board of Example 1, both the resistance value and the peak current value of the magnetic head hardly changed before and after charging, and the magnetic head was not destroyed and the performance was not deteriorated. On the other hand, among the head suspension assemblies using the flexible printed circuit board of Comparative Example 1, in Samples 3 and 4, the resistance value of the magnetic head remarkably increased and the peak current value drastically decreased. This indicates that the insulating film of the magnetic head has been destroyed (hard ESD). In Sample 5, the resistance value of the magnetic head did not change, but the peak current value changed significantly. This is deterioration of magnetic head performance (soft ESD)
Represents what happened.

Test Example 3 The flexible printed circuit board obtained in Example 1 was tested for adhesion of the conductive polymer layer. First, the charging potential of the flexible printed circuit board was measured and used as the initial potential. Subsequently, the flexible printed circuit board was rubbed with a rubbing plate a predetermined number of times, and then the charging potential was measured again. Also, when the flexible printed circuit board was rubbed 50 times with a cotton swab impregnated with isopropanol between the initial potential measurement and the friction with the friction plate, the charging potential after rubbing a predetermined number of times was similarly measured. The results are shown in Table 3.

[Table 3] Table 3 shows that the charging potential after the friction plate was rubbed 500 times hardly changed regardless of the presence or absence of the application of isopropanol, which is the same as that of the conductive polymer layer of the flexible printed circuit board of Example 1. It demonstrates excellent adhesion and chemical resistance.

[0047]

EFFECT OF THE INVENTION The flexible printed circuit board of the present invention is provided with the conductive polymer layer on at least the lower surface of the base layer and the upper surface of the cover layer, so that static electricity generated by friction is quickly discharged. The charging potential can be reduced. Further, in the conventional head suspension assembly, the magnetic head and the board unit are connected by the two members of the fixed wiring and the flexible printed circuit board, whereas the flexible printed circuit board of the present invention extends to the magnetic head. As a result, the magnetic head and the substrate unit are directly relayed, so that the work of connecting the fixed wiring, which causes static electricity, and the conductor circuit in the flexible printed circuit board becomes unnecessary. As a result, in the head suspension assembly using the flexible printed circuit board of the present invention, even when a high-performance magnetic head that is extremely sensitive to electrostatic breakdown is used, breakdown of the insulating film of the magnetic head and magnetic head It is possible to sufficiently suppress the deterioration of the performance. In addition, in the production of the flexible printed circuit board of the present invention, it is not necessary to handle the stainless layer which is easily irreversibly deformed until the final production step. Therefore, many manufacturing processes can be operated in the same form as the flexible film, and as a result, productivity can be improved step by step.

[Brief description of drawings]

FIG. 1 is a plan view illustrating an aspect of a head suspension assembly using a flexible printed circuit board according to the present invention.

FIG. 2 is a sectional view taken along the line A-A ′ of FIG.

[Explanation of symbols]

a Head suspension assembly 1 Flexible printed circuit board 2 magnetic head 3 suspension 4 Base end side connection end 11 laminate 12 Base layer 13 conductor circuit 14 cover layer 15 Conductive polymer layer 16 stainless steel layer 17 Adhesive

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D042 NA01 PA08 TA07                 5D059 AA01 BA01 CA26 DA36 EA20                 5E314 AA32 AA36 BB02 BB11 CC15                       DD07 FF06 FF16 GG01 GG03                 5E338 AA01 AA12 AA16 BB72 CC01                       CC05 CD13 EE11

Claims (6)

[Claims] 1. A flexible printed circuit board for directly relaying a magnetic head mounted on a suspension and a connection end of a base end of a carriage arm in a head suspension assembly of a magnetic disk drive, The circuit board comprises a base layer, a conductor circuit formed on the base layer, a cover layer covering the conductor circuit, and a conductive polymer layer formed at least below the base layer and above the cover layer. A flexible printed circuit board comprising: a laminated body having the following structure; and a stainless steel layer attached to the laminated body from below the base layer. 2. The flexible printed circuit board according to claim 1, wherein the base layer and the cover layer are made of a polyimide resin or an epoxy resin, and the conductive polymer layer is made of a polypyrrole resin. 3. The thickness of the conductive polymer layer is 0.03.
To 0.05 μm.
The flexible printed circuit board described. 4. The flexible printed circuit board according to claim 1, wherein the surface resistivity is 10 ⁶ to 10 ⁸ Ω. 5. A base layer is formed, a conductor circuit is formed on the base layer, a cover layer is formed on the base layer to cover the conductor circuit, and at least an underside of the base layer. The method for manufacturing a flexible printed circuit board according to claim 1, further comprising: forming a conductive polymer layer on the upper side of the cover layer to form a laminate, and adhering the laminate to a stainless layer. 6. The manufacturing method according to claim 5, wherein an epoxy adhesive is used for the attachment.