JP2000067421A - Production of suspension for magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make reducible the alignment frequency and to attain a reduced cost and enhanced productivity by forming a conductor pattern part on an electrically conductive substrate, patterning an insulating resin-base material corresponding to the conductor pattern part on a metallic sheet, bonding the conductor pattern part to the insulating resin-base material after alignment, peeling the substrate and forming a protective layer. SOLUTION: The surface of an electrically conductive substrate is coated with a liq. photosensitive resin compsn. and a desired resin pattern hardened body is formed by exposure and development. A conductor pattern is formed by electroplating on the part freed of the resin compsn. and the resin pattern hardened body is removed to form a conductor pattern part. An insulating resin-base material corresponding to the conductor pattern part is patterned on a metallic sheet, the conductor pattern part is bonded to the insulating resin- base material after alignment and the substrate is peeled. A protective layer is formed on the conductor pattern part and the metallic sheet is formed in a desired shape by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a "suspension" for supporting a magnetic head mounted on a hard disk drive. For more information,
This is a method for manufacturing a “suspension” having a wiring pattern suitably used in a high frequency region of the MHz band or higher.

[0002]

2. Description of the Related Art Conventionally, the structure of a suspension used in a magnetic head of a hard disk drive has been fixed by means of laser welding or the like along a "twisted" wire along a stainless steel mount. However, as the recording density has increased, the size of the magnetic head has been required to be smaller, making it difficult to manufacture the magnetic head by the wire fixing method, the flying height of the magnetic head has been reduced, and an extremely high precision weight balance has been required. For this reason, a “wiring-integrated suspension” that forms wiring directly on a mount is being adopted. For example, Nikkei Electronics '98.
No. 4 (No. 713) p. 167 describes a method for producing a general wiring-integrated suspension. Also, Japanese Patent Application Laid-Open
No. 45213 discloses a method of manufacturing a suspension by a photolithography method.

The suspension obtained by these methods is formed by an "additive method" in which wiring is stacked on a mount, and while high positional accuracy is obtained, the number of complicated positioning steps is large, and productivity and cost are reduced. At leaving the problem. Furthermore, due to the increase in the frequency of signals due to the increase in information density, it has become impossible to obtain sufficient characteristics of the required conductor pattern shape using conventional round wires or square wires. That is, there are problems of impedance and crosstalk in a high frequency region. In order to improve the impedance, the resistance has been reduced by increasing the cross-sectional shape of the wiring itself.However, in the high frequency region, the current flows through the surface layer of the conductor due to the skin effect, so the controlling factor of the wiring resistance is the cross-sectional area. Not by surface area. Therefore, high-frequency wiring is required to have a large surface area. on the other hand,
When the conductor projected area is large, an eddy current is generated on the conductor surface, which causes a problem of noise, and it is not preferable that the conductor wiring is too close due to a problem of crosstalk.

As described above, the wiring design required for a high-frequency circuit is a conductor shape having a small conductor width and a large conductor thickness in order to increase the surface area. A method for forming a conductor circuit includes the following three methods. That is, an etching method in which a desired circuit is formed by etching or the like using a cured resin image of a photosensitive resin composition formed on a conductive substrate as a protective film, a resin pattern is formed on an insulating substrate, and electroless copper is used. An additive method in which a conductor circuit is formed by plating or the like, and a semi-additive method which is an intermediate method between the two.

[0005]

However, the subtractive method cannot be applied to a high frequency circuit due to the problem of side etching, and the additive and semi-additive methods cannot obtain a resin pattern having a large aspect ratio. In response to these requests, Microelectronic
Engineering 4 (1986) p.35 and Proc.IEEE Solid-State S
A sensor production method by X-ray lithography (LIGA process) combining a PMMA resist and synchrotron radiation has been proposed in P1 of the ensor & Actuator Workshop June (1988). These methods enable extremely high-density and high-precision conductors to be produced. However, since the X-ray source is extremely expensive, it is difficult to reduce the cost, and the size of a usable substrate is limited. In this respect, there remains a problem in industrial production.

Accordingly, the present invention has been made to solve the above-mentioned drawbacks. That is, it is an object of the present invention to provide a method for manufacturing a suspension for a wiring-integrated magnetic head, which has a low number of times of high-precision alignment, is low in cost, has excellent productivity, and has excellent high frequency characteristics.

[0007]

As a result of intensive studies, the present inventor has applied the technique proposed in Japanese Patent Application Laid-Open No. Hei 6-283830 to a conductor formation technique.
The present inventors have found that a suspension for a wiring-integrated magnetic head having good high-frequency characteristics can be stably manufactured at low cost, and have led to the present invention.

That is, the present invention provides a method for applying a liquid photosensitive resin composition to the surface of a conductive substrate, forming a desired resin pattern cured product by exposure and development, and electrolytically plating the portion from which the resin composition has been removed by electrolytic plating. Forming a conductor pattern, removing the cured resin pattern, thereby forming a conductor pattern portion, patterning an insulating resin base material corresponding to the conductor pattern portion on a metal plate, After aligning the pattern portion and the insulating resin base material, a laminating step of bonding and, after peeling the conductive substrate, forming a protective layer on the conductive pattern portion and etching the metal plate into a desired shape by etching. Forming a suspension for a magnetic head. In other words, there is a method in which a conductor pattern is formed once on a conductive substrate without directly forming a conductor pattern on a mount, and then laminated on an insulating resin base pattern formed on a suspension.

The liquid photosensitive resin composition used here is:
Ethylenic unsaturated bond concentration is 10 ^-2 to 2 × 10 ^-4 mol
/ G and a prepolymer and / or oligomer having an ethylenically unsaturated bond having a molecular weight of 500 to 100,000 and an ethylenically unsaturated compound monomer. More preferably, the oligomer or prepolymer having an ethylenically unsaturated bond is an alcohol component comprising a mixture of an alkyl diol and a diol having 5 or more ether bonds in a molecule, and a dicarboxylic acid having an ethylenically unsaturated bond. An unsaturated polyester obtained by polycondensation of an acid component consisting of an acid alone or a mixture of a dicarboxylic acid having no ethylenically unsaturated bond and a dicarboxylic acid having an ethylenically unsaturated bond.

If the molecular weight is less than 500, the sensitivity of the photosensitive resin composition is too low to withstand the formation of a resin pattern. The developability of the cured resin portion is significantly reduced, and high resolution cannot be obtained. From the standpoint of sensitivity and resolution, a more preferred molecular weight range is 1200 to 250.
00 range.

As oligomers or prepolymers used as the liquid photosensitive resin composition, unsaturated polyesters, unsaturated polyurethanes, oligoester acrylates or oligoester methacrylates, unsaturated polyamides, unsaturated polyimides, unsaturated poly Examples thereof include ethers, unsaturated polyacrylates or unsaturated polymethacrylates, various modified products thereof, mixtures thereof, and compounds having a carbon-carbon double bond. Among these, unsaturated polyesters and unsaturated polyurethanes provide particularly good resin patterns.

As unsaturated polyesters, for example, unsaturated dibasic acids such as maleic acid, fumaric acid and itaconic acid or anhydrides thereof and ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, Polyesters reacted with polyhydric alcohols such as pentaerythritol, 1,4-polybutadiene having a terminal hydroxyl group, hydrogenated or non-hydrogenated 1,2-polybutadiene, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer And polyesters in which a part of the acid component is replaced with a saturated polybasic acid, or polyesters modified with a drying oil or semi-dry oil.

Examples of unsaturated polyurethanes include, for example,
Polyols such as the above-mentioned polyhydric alcohols, polyester polyols and polyether polyols, 1,4-polybutadiene having a terminal hydroxyl group, hydrogenated or non-hydrogenated 1,2-polybutadiene, butadiene-styrene copolymer, butadiene -Acrylonitrile copolymer and the like, tolylene diisocyanate, diphenylmethane,
Compounds in which unsaturated groups are introduced by utilizing the reactivity of terminal isocyanate groups or hydroxyl groups of polyurethanes derived from polyisocyanates such as 4,4'-diisocyanate and hexamethylene diisocyanate. That is, an unsaturated group is introduced by reacting a compound having active hydrogen such as a hydroxyl group, a carboxyl group, or an amino group with an isocyanate, or an unsaturated group is introduced by a reaction between a carboxyl group and a hydroxyl group, or And the like in which unsaturated polyesters of the above are linked by polyisocyanates.

The liquid photosensitive resin composition of the present invention can be used by adding various components as needed for the purpose of obtaining a better resin pattern or for the convenience of handling. For example, a monomer having two or less polymerizable functional groups in one molecule to adjust the viscosity of the liquid photosensitive resin composition, or a phosphoric acid group to improve the adhesion to the conductive substrate A polymerizable monomer, a thermal polymerization inhibitor or the like may be included as a component in order to improve the storage stability of the photosensitive resin composition.

In the present invention, a photopolymerization initiator or a photosensitizer can be added for the purpose of shortening the reaction time and curing time of the liquid photosensitive resin composition, or improving sensitivity and resolution. The high energy ray referred to in the present invention is an ultraviolet light, a far ultraviolet light, a laser beam or the like which can efficiently cure the liquid photosensitive resin composition, and a soft X-ray, an electron beam or the like is also used in the liquid of the present invention. It is effective for curing the photosensitive resin composition.

The inter-conductor insulating layer can be stripped by any method such as dissolution and removal with a chemical solution such as concentrated sulfuric acid, burnout by heat treatment, and mechanical stripping. Since the conductor obtained by the method of the present invention has a rectangular shape, a large film thickness, and a narrow pitch, it is excellent in terms of the skin effect of current in a high frequency region and suppression of eddy current generation.

In the case of the high-frequency circuit, when the cross-sectional area of the conductor is the same, the resistance in the high-frequency region decreases as the conductor surface area increases, and the impedance characteristic improves. That is,
When the cross-sectional shape is rectangular rather than round, the conductor surface area is 27
%, And the high frequency characteristics are dramatically improved. The conductor surface area and S cannot be unambiguously determined by the suspension configuration or the required conductor cross-sectional area.
Good characteristics are given when S ≦ 360 μm ² . 30 μm ² ≦ S
In the high frequency resistance is high, the impedance characteristics deteriorate,
If S ≧ 360 μm ² , a problem arises from the viewpoint of miniaturization of the suspension.

The surface diffuse reflectance of the conductive substrate used for obtaining a rectangular resin pattern in the photolithography step is preferably 20% or less. In addition, industrially inexpensive aluminum substrates and copper substrates can be suitably used. Next, the patterning of the insulating resin base material formed on the suspension can be obtained by screen-printing a liquid insulating resin material, for example, a conventional insulating resin such as an epoxy resin, a polyimide resin, an acrylic resin, and an ester resin. Further, the photosensitive resin can be easily obtained by a photolithography method in which the photosensitive resin is coated, and a mask is exposed and developed. Before patterning the insulating resin, it is preferable that the suspension material is subjected to a heat treatment for adjusting rigidity. By performing the heat treatment for adjusting the rigidity first, the heat resistance of the insulating resin becomes unnecessary.

For bonding the conductive pattern to the insulating base, first, an insulating resin material is applied to the conductive pattern portion by screen printing or the like, and then pressure bonding is performed by a pin matching method. In this case, it is necessary to control the temperature and humidity at the time of pressure bonding in order to increase the bonding position accuracy, and the number of used positioning pins is preferably four or more. After the conductive pattern is adhered, any method such as dissolution and removal by a chemical solution (hydrochloric acid in the case of aluminum, nitric acid in the case of copper substrate) or mechanical peeling can be used for peeling the conductive substrate.

As a final step, a protective film made of a photosensitive resin is patterned on a necessary portion including the conductor pattern portion, and a rigid metal plate is processed into a desired shape by a technique such as etching. If necessary, heat treatment for adjusting the rigidity of the suspension is performed. By performing the above steps, it is possible to manufacture a wiring-integrated magnetic head suspension having a good number of alignment steps and excellent high-frequency characteristics.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating the manufacturing process of the present invention. In FIG. 1, (1) first, a liquid photosensitive resin composition 3 is applied on a conductive substrate 4. The photolithographic mask 1 is disposed on the liquid photosensitive resin composition 3 via the protective film 2. (2) The resin is hardened by a laser through the mask 1 and a portion not exposed to the laser is removed by developing. (3) A plated conductor pattern 5 is formed on the removed portion by electrolytic plating.
(4) Next, the insulating resin base material 6 patterned on the metal plate 7 is bonded so that the patterns face each other. After that, the conductive substrate 4 is peeled off. (5) A protective film is formed on the surfaces of the metal plate 7 and the plated conductor pattern 5. (6) A photosensitive resin film is stuck on the opposite side of the metal plate 7, developed and exposed through a photolithographic mask 10,
Perform desired patterning. Finally, unnecessary portions are removed to form a magnetic head suspension.

Next, the present invention will be described in more detail with reference to examples.
The present invention is not limited by the embodiments.

[0023]

Example 1 Toyo Aluminum Co., Ltd., thickness 100 μm
m aluminum substrate was subjected to a surface treatment at 30 ° C. for 80 seconds using an AZ401 treatment solution manufactured by Uemura Kogyo Co., Ltd. As a result of measuring the surface diffuse reflectance at 365 nm of the obtained aluminum substrate with an MPS-2000 spectrophotometer manufactured by Shimadzu Corporation, it was found to be 19%.

Next, propylene glycol, diethylene glycol and adipic acid, isophthalic acid, and fumaric acid are each in a molar ratio of 0.12 / 0.38 / 0.24 / 0.1.
100 parts of an unsaturated polyester resin obtained by condensation at a ratio of 2 / 0.14 were mixed with 12 parts of diethylene glycol dimethacrylate, 30 parts of tetraethylene glycol dimethacrylate, and 12 parts of 2-hydroxyethyl methacrylate.
Parts, 6 parts of diacetone acrylamide, 2 parts of benzoin isobutyl ether, and 0.03 part of 4-tert-butylcatechol were sufficiently stirred and mixed to obtain a liquid photosensitive resist raw material.

The prepared photosensitive resist material was applied to the above-treated aluminum substrate using an SRB apparatus manufactured by Asahi Kasei Corporation. At this time, the thickness of the resist layer is 40 μm.
m was adjusted with a specer. Exposure and development of mask using a predetermined glass mask and a parallel light source manufactured by Oak Co. (1% sodium borate solution, 40 ° C., discharge pressure 0.1 kg)
/ cm 2), and a resist pattern having a width of 15 μm or more and a height of 40 μm was formed on an aluminum substrate at a pitch of 30 μm. The obtained resist pattern was coated with a current density of 3 A /
Under the condition of dm2, a 40 µm plated copper film is deposited,
Further, the resist pattern was decomposed and removed in concentrated sulfuric acid at room temperature for 5 minutes to form a desired conductor pattern on the aluminum substrate.

Next, a thermosetting polyimide resin was patterned on the surface of a rigid metal such as stainless steel by screen printing to a thickness of about 15 μm so as to have a shape corresponding to the conductor pattern. After patterning, 30
After curing for a minute, complete curing was performed at 300 ° C. for 3 minutes. The conductive pattern is coated with photosensitive polyimide on the conductive substrate surface, pre-baked, subjected to mask exposure and development, bonded to the rigid substrate using four alignment pins, and baked at 260 ° C. for 30 minutes. And bonded. Further, the aluminum substrate was removed by etching with 10% hydrochloric acid.

As a final step, the surface of the rigid metal substrate was patterned with a protective resist so as to obtain a desired pattern, and the suspension was finished by etching. After cutting out the part containing the conductor of the obtained suspension into about 2 cm square and curing it with epoxy resin,
As a result of mirror-polishing with a polishing machine and observing the cross-sectional shape of the conductor pattern portion, the cross section was rectangular with a conductor height of 40 μm, a distance between conductors of 15 μm, and a wiring pitch of 30 μm.

The calculated shape factors are: conductor surface area per unit, S = 95 μm ² , conductor cross section, D = 600
μm ² , and the conductor height / interconductor distance ratio H / G was 2.7.

[0029]

According to the present invention, a high-aspect-ratio, high-density conductor pattern is prepared in advance and adhered to a highly rigid metal base, thereby reducing the number of alignment steps and improving the high-frequency characteristics. A suspension for a magnetic head can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a manufacturing process of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photolithographic mask 2 protective film 3 liquid photosensitive resin composition 4 conductive substrate 5 plated conductor pattern 6 insulating resin base material 7 metal plate 8 protective layer 9 photosensitive resin film 10 photolithographic mask

Claims (3)

[Claims] 1. A liquid photosensitive resin composition is coated on the surface of a conductive substrate, a desired resin pattern cured product is formed by exposure and development, and a conductor pattern is formed by electrolytic plating on a portion where the resin composition is removed. Then, by removing the cured resin pattern, a step of forming a conductor pattern portion, a step of patterning an insulating resin base material corresponding to the conductor pattern portion on a metal plate, After aligning the insulating resin base material, a laminating step of bonding, and after peeling off the conductive substrate, forming a protective layer on the conductive pattern portion, and forming the metal plate into a desired shape by etching, A method of manufacturing a suspension for a magnetic head, comprising: 2. A liquid photosensitive resin composition comprising an ethylenically unsaturated resin.
Saturation bond concentration is 10 ^-2~ 2 × 10^-Fourmol / g and min
Ethylenically unsaturated bond having a molecular weight of 500 to 100000
Prepolymers and / or oligomers having
Characterized by comprising a lenic unsaturated compound monomer
A method for manufacturing a suspension for a magnetic head according to claim 1. 3. The method of manufacturing a suspension for a magnetic head according to claim 1, wherein the conductive substrate used is aluminum or copper.