JP2011243256A - Suspension flexure substrate, suspension, suspension with head, and hard disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suspension flexure substrate, suspension, suspension with a head, and a hard disk drive which are capable of preventing detachment of a wiring due to an undercut on the bottom of the wiring and also preventing increase in impedance due to the cross-sectional shape of the wiring, without any additional complicated processes.SOLUTION: In etching by a subtractive method, a wiring having an approximately rectangular cross-sectional shape is formed by an anisotropic etching where an etch factor is greater than 5.

Description

  The present invention relates to a suspension flexure substrate, a suspension, a suspension with a head, and a hard disk drive, in which wiring for electrically connecting a magnetic head and an external circuit is integrally formed.

  In recent years, due to the spread of the Internet and the like, there has been a demand for an increase in the amount of information processing of personal computers and an increase in information processing speed. Increasing information transmission speed is required.

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

  In addition, a component called a magnetic head suspension used in the hard disk drive is also a so-called wireless suspension in which a signal line such as a copper wiring is directly formed on a stainless spring from a conventional type in which a signal line such as a gold wire is connected. It is shifting to a wiring integrated type called flexure.

  As for wirings formed on such a flexure substrate for suspension, a reading side wiring consisting of a pair of wirings and a writing side wiring consisting of a pair of wirings are usually formed on the same surface of the insulating layer. In addition, such a pair of wires, for example, transmits electrical signals by differential transmission, and there is a differential impedance that is a characteristic impedance of the differential transmission line as a distributed constant circuit between the pair of wires. To do. The differential impedance is required to be lowered from the viewpoint of impedance matching as the impedance of the magnetic head and the preamplifier is lowered.

  Here, as a wiring forming method in the manufacture of the above-described suspension flexure substrate, a semi-additive method and a subtractive method that have been conventionally used for manufacturing a flexible printed wiring board are known (Patent Document 1, 2).

  For example, in the semi-additive method, a conductive thin film layer is formed on the entire surface of the insulating layer of the substrate, a resist pattern having a wiring pattern opened on the conductive thin film layer, and electrolytic plating by feeding from the conductive thin film layer. In this method, a wiring made of copper or the like is formed in the opening, and then the resist pattern is removed and the exposed portion of the conductive thin film layer is etched away.

  On the other hand, in the subtractive method, for example, a resist pattern is formed on the wiring conductor layer of the base material on which a metal support substrate, an insulating layer, and a wiring conductor layer are sequentially formed, and wiring exposed from the resist pattern is used. The conductor layer is etched to form a wiring.

  Conventionally, rolled copper foil or the like has been used as the wiring conductor layer. However, in recent years, the wiring copper layer is formed by electrolytic plating mainly for miniaturization of wiring. A conductive thin film layer for plating power supply is provided between the insulating layer and the wiring conductor layer. In this case, after the wiring is formed, the unnecessary conductive thin film layer exposed is removed.

JP 2006-24521 A JP 2007-194265 A JP 2005-158848 A

  However, in the above-described semi-additive method, as shown in FIG. 5A, the resist pattern 25 formed on the conductor thin film layer 22A has a skirt that becomes wider toward the bottom contacting the conductor thin film layer 22A. Therefore, the cross-sectional shape of the wiring 21 formed in the opening of the resist pattern by electrolytic plating is an undercut that becomes narrower toward the bottom at the bottom contacting the conductor thin film 22, as shown in FIG. 5B. Part 26 is produced.

  Therefore, when the exposed portion of the conductive thin film layer is removed by etching, the conductive thin film 22 at the bottom of the wiring 21 is etched so as to be largely removed inside the wiring 21 due to the undercut portion 26. If it does so, the adhesive force of the insulating layer 23 and the conductor thin film 22 will fall significantly, and the malfunction that the conductor thin film 22 and the wiring 21 will peel from the insulating layer 23 will arise.

  As a method for preventing the conductor thin film 22 and the wiring 21 from being peeled, a method is proposed in which a metal thin film is formed on the entire surface after the wiring is formed, and the undercut portion 26 is filled with the metal forming the metal thin film ( Patent Document 3). However, such a method has a disadvantage that the number of complicated processes increases and productivity is inferior.

  On the other hand, in the case of the subtractive method described above, the wiring 31 is formed by etching the wiring conductor layer exposed in the opening of the resist pattern 35 as shown in FIG. There is no problem of generating a portion, and a wiring having strong adhesion can be obtained.

  However, conventional etching is likely to be isotropic etching with a small etching factor (Ef), and as shown in FIG. 6B, the cross-sectional shape of the formed wiring has a width at the top of the wiring. A trapezoidal shape that is smaller than the width of the bottom of the wiring tends to be formed, and as a result, the cross-sectional area between the wirings becomes larger than the cross-sectional area between the wirings having an ideal rectangular cross section. There was a tendency to make it smaller.

  Here, the etching factor (Ef) is a factor representing the degree of side etching. The thickness of the wiring conductor layer 11A is H, the width of the bottom of the wiring formed by etching is B, and the wiring When the upper width is T, it is obtained from the equation Ef = 2H / (B−T).

  That is, when the thickness (the height of the wiring 11) H of the wiring conductor layer 11A is constant, the degree of side etching decreases as the value of the etching factor (Ef) increases. The wiring 31 formed under the conventional etching conditions with a strong isotropic tendency has a large degree of side etching, and its cross section has a shape of 2H / (BT) <3.5.

  Therefore, when the wiring formed by the subtractive method has the same wiring pitch (usually, the width between the wiring bottom and the wiring bottom is designed to be 1: 1), the wiring formed by the semi-additive method is used. There is a tendency that the inter-wiring capacitance becomes smaller than that, and the impedance of the wiring becomes larger.

  The present invention has been made in view of the above circumstances, and without increasing the number of complicated steps, while preventing the separation of the wiring due to the undercut at the bottom of the wiring, the impedance also increases due to the cross-sectional shape of the wiring An object of the present invention is to provide a suspension flexure substrate, a suspension, a suspension with a head, and a hard disk drive that can be prevented.

  As a result of various studies, the present inventor has found a condition for making the etching in the subtractive method more anisotropic and reducing the difference between the width at the top and the bottom of the formed wiring, thereby making the complex The present invention has been completed by finding that an undercut at the bottom of the wiring can be prevented and an impedance can be reduced without increasing the number of processes.

  That is, the invention according to claim 1 of the present invention is a suspension flexure substrate in which a plurality of parallel running wirings are formed on an insulating layer formed on a metal support substrate. There is no undercut, and the relationship between the height (H) of the wiring, the width (B) of the bottom of the wiring, and the width (T) of the top of the wiring is 2H / (B−T)> 5. Is a flexure substrate for suspension.

  The invention according to claim 2 of the present invention is the flexure substrate for suspension according to claim 1, wherein the pitch of the wiring is 30 μm or less.

  The invention according to claim 3 of the present invention is the flexure substrate for suspension according to any one of claims 1 and 2, wherein the width (B) of the bottom of the wiring is 15 μm or less. .

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

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

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

  According to the present invention, since the wiring of the flexure substrate for suspension is formed by the subtractive method, there is no problem that an undercut portion such as the wiring formed by the semi-additive method is generated. Therefore, a suspension flexure substrate having wiring with high adhesion reliability can be obtained without increasing complicated processes.

  Further, according to the present invention, since the wiring of the flexure substrate for suspension is formed by anisotropic etching with a high etching factor, the formed wiring has a substantially rectangular shape with a small difference between the width at the top and the width at the bottom. Since the cross-sectional shape is increased, the inter-wiring capacitance is increased, and a suspension flexure substrate with reduced impedance can be obtained.

1 is a schematic plan view illustrating an overall image of a flexure substrate for suspension according to the present invention. It is AA sectional drawing of the R area | region in FIG. It is a schematic explanatory drawing which illustrates the section shape of the wiring of the flexure substrate for suspensions concerning the present invention. It is a manufacturing process figure which shows an example of the manufacturing method of the flexure board | substrate for suspensions which concerns on this invention. It is the schematic explaining the shape of the wiring formed by the conventional semiadditive method, (a) is sectional drawing which shows the relationship between a resist pattern shape and wiring shape, (b) is wiring finally obtained It is sectional drawing which shows the shape. It is the schematic explaining the shape of the wiring formed by the conventional subtractive method, (a) is sectional drawing which shows the relationship between a resist pattern shape and wiring shape, (b) is wiring finally obtained It is sectional drawing which shows the shape.

Hereinafter, the flexure substrate for suspension of the present invention will be described in detail.
[Flexible substrate for suspension]
FIG. 1 is a schematic plan view illustrating an overall image of a flexure substrate for suspension according to the present invention. A suspension flexure substrate 1 shown in FIG. 1 has a gimbal portion 2 for mounting a magnetic head in the vicinity of its tip, and the gimbal portion 2 has a connection terminal portion for electrical connection with the magnetic head. Is formed.

  On the other hand, a connection terminal portion 3 for connection to an external circuit is formed in the vicinity of the end of the suspension flexure substrate 1, and the connection terminal portion of the gimbal portion 2 for connection to the magnetic head is connected to the external circuit. A plurality of wirings 4 are formed so as to be electrically connected to the connection terminal portion 3 for the purpose.

  2 is a cross-sectional view of the R region in FIG.

  As shown in FIG. 2, the suspension flexure substrate according to the present invention includes a metal support substrate 14 made of SUS or the like, an insulating layer 13 formed on the metal support substrate 14, and the insulating layer 13. And a wiring 11 to be formed.

  In FIG. 2, a conductor thin film 12 is formed between the insulating layer 13 and the wiring 11 in order to exemplify a form in which the conductor layer processed into the wiring 11 is formed by electrolytic plating.

  Although not shown in FIG. 2, a cover layer made of an insulator may be formed so as to cover the wiring 11.

  In the present invention, since the wiring 11 is formed by the subtractive method, an undercut portion unlike the wiring formed by the semi-additive method does not occur at the bottom of the wiring 11.

  Therefore, there is no wiring peeling caused by a decrease in adhesion due to the above-mentioned undercut portion, and the flexure substrate for suspension according to the present invention has a configuration having a high adhesion reliability.

  In the present invention, since the wiring 11 is formed by anisotropic etching having a large etching factor (Ef), the formed wiring has a substantially rectangular shape in which the difference between the width at the top and the width at the bottom is small. The cross-sectional shape is as follows. Therefore, the inter-wiring capacitance is increased, and a suspension flexure substrate with reduced impedance can be obtained.

  FIG. 3 is a schematic explanatory view showing the cross-sectional shape of the wiring of the suspension flexure substrate according to the present invention.

  Since the wiring 11 of the flexure substrate for suspension according to the present invention is formed by anisotropic etching having a large etching factor (Ef), the wiring height is H and the wiring as shown in FIG. When the width of the bottom portion of B is B and the width of the upper portion of the wiring is T, the value obtained by dividing the value twice H by the value obtained by subtracting T from B is larger than 5. ing.

  That is, the wiring 11 has a shape in which the relationship among the height (H) of the wiring, the width (B) of the bottom of the wiring, and the width (T) of the top of the wiring satisfies 2H / (B−T)> 5. It is.

  By adopting such a shape, the cross-sectional area between parallel wirings can be made smaller than the cross-sectional area between wirings having a conventional trapezoidal cross-sectional shape when the wiring pitch is the same, and as a result. The inter-wiring capacity is increased, and a suspension flexure substrate with reduced impedance can be obtained.

  In the present invention, since the wiring 11 has a substantially rectangular cross-sectional shape as described above, the conventional cross-sectional shape is suitable for increasing the density and miniaturization of the wiring as compared to a trapezoidal wiring.

  More specifically, in a conventional wiring having a trapezoidal cross-sectional shape, when a wiring pattern having a wiring width (line width) and a wiring interval (space width) of 1: 1 is desired, In consideration of side etching, it is necessary to make the space width (opening width) narrower than the line width (for example, line width: space width = 3: 1). It has been difficult to form a small resist pattern.

  On the other hand, if the cross-sectional shape of the wiring is rectangular, the influence of side etching is reduced, so even in the resist pattern, the space width can be made as large as the line width, and the wiring pitch is reduced. Even in this case, it becomes easy to form a resist pattern.

  Therefore, according to the present invention, for example, it is possible to sufficiently meet the demand for high-density wiring and fine wiring such that the wiring pitch is 30 μm or less or the width (B) of the bottom of the wiring is 15 μm or less.

Next, the suspension flexure substrate according to the present invention will be described for each configuration.
[Metal support substrate]
The material of the metal support substrate 14 is not particularly limited as long as it has a spring property, and examples thereof include SUS, 42 alloy, copper, copper alloy, etc. Among them, SUS is preferable. The thickness of the metal support substrate 14 is, for example, in the range of 12 μm to 76 μm, and preferably in the range of 14 μm to 25 μm.
[Insulation layer]
The material of the insulating layer 13 is not particularly limited as long as it has a desired insulating property, and examples thereof include polyimide. The material of the insulating layer 13 may be a photosensitive material or a non-photosensitive material. The thickness of the insulating layer 13 is preferably in the range of, for example, 5 μm to 20 μm, and more preferably in the range of 8 μm to 12 μm.
[Conductive thin film]
The conductor thin film 12 exists between the insulating layer 13 and the wiring 11 and exists when a wiring conductor layer for forming the wiring 11 is formed by an electrolytic plating method. More specifically, when a wiring conductor layer for forming the wiring 11 is formed by an electrolytic plating method, a conductive thin film layer is formed on the insulating layer 13 as a seed layer for plating power feeding. After forming the wiring 11 by etching, the exposed conductive thin film layer is removed by etching to form the conductive thin film 12.

  The formation method, material, etc. of the conductor thin film 12 can use a well-known technique, and are not specifically limited. For example, Cr, Ni, and Cu can be formed by sputtering film formation.

In the present invention, for example, the conductor thin film 12 may be formed by forming Cr alone or Ni—Cr with a thickness of 8 to 60 nm in the lower layer and forming Cu with a thickness of 50 to 200 nm in the upper layer. it can.
[wiring]
The wiring 11 is not particularly limited as long as it has desired conductivity, but Cu is usually used as the material thereof.

  For example, the thickness of the wiring 11 is preferably in the range of 4 μm to 18 μm, and more preferably in the range of 5 μm to 12 μm. If the wiring thickness is too small, it may not be possible to achieve a sufficiently low impedance. If the wiring thickness is too large, etching processing becomes difficult and the rigidity of the flexure substrate for suspension is high. This is because it may become too much.

The line width of the wiring 11 is, for example, in the range of 5 μm to 50 μm. If the wiring line width is too small, the desired conductivity may not be obtained. If the wiring line width is too large, the suspension flexure substrate may not be sufficiently densified. Because there is.
[Cover layer]
In order to suppress deterioration due to electrical signal attenuation and wiring corrosion, the wiring 11 may be covered with a cover layer made of an insulating layer. However, in order to suppress the occurrence of warping of the flexure substrate for suspension, it is preferable that the cover layer is formed only at a necessary portion.

The material for the cover layer is not particularly limited, and a known material can be used. For example, polyimide can be used. The material of the cover layer may be a photosensitive material or a non-photosensitive material. The thickness of the cover layer is preferably in the range of 2 μm to 20 μm, for example.
[Metal plating layer]
The metal plating layer is formed on the exposed surface of the wiring 11 in the connection terminal portion, and is intended to improve electrical connection with a magnetic head or an external circuit and to protect the exposed wiring from corrosion.

  The metal plating layer is formed by an electrolytic plating method, and any material can be used without particular limitation as long as it can form the terminal portion of the flexure substrate for suspension. For example, Cu (copper) ), Ni (nickel), Cr (chromium), Au (gold), or the like.

Further, the metal plating layer may be formed as a multilayer. For example, electrolytic Ni plating and electrolytic Au plating may be sequentially performed to form a multilayer structure of Ni in the lower layer and Au in the upper layer. The thickness of the Ni layer is, for example, about 0.1 to 3 μm, and the thickness of the Au layer is, for example, about 0.3 to 5 μm.
[Manufacturing method of flexure substrate for suspension]
Next, a method for manufacturing a flexure substrate for suspension according to the present invention will be described.

  FIG. 4 is a schematic manufacturing process diagram showing an example of the manufacturing method of the flexure substrate for suspension according to the present invention, and schematically shows a cross section perpendicular to the longitudinal direction of the wiring as shown in FIG. . In the present invention, the wiring 11 is formed by a subtractive method.

  In the method for manufacturing a flexure substrate for suspension according to the present invention, first, as shown in FIG. 4A, a base material on which a metal support substrate 14, an insulating layer 13, and a wiring conductor layer 11A are sequentially formed is prepared. In FIG. 4, in order to exemplify a form in which the wiring conductor layer 11A is formed by electrolytic plating, a conductive thin film layer 12A for plating power feeding is formed between the insulating layer 13 and the wiring conductor layer 11A. Yes.

  Next, a dry film resist is laminated on the wiring conductor layer 11A, and exposure and development are performed to form a resist pattern 15 corresponding to the wiring pattern (FIG. 4B).

  Next, as illustrated in FIG. 4C, the wiring conductor layer 11 </ b> A exposed from the opening of the resist pattern 15 is etched to form the wiring 11.

  In order to make the cross-sectional shape of the wiring substantially rectangular, the etching solution used for the etching is an aqueous solution containing ferric chloride as a main component, and at least one of ethylene oxide and propylene oxide as an additive is an amine compound. It is preferable to use a compound containing a compound added to activated hydrogen, and it is more preferable that the additive is a compound obtained by block addition or random addition of ethylene oxide and propylene oxide to activated hydrogen of ethylenediamine. The additive has an affinity for Cu and has an effect of suppressing side etching.

  The etching is spray-type etching, and the spray pressure is preferably 0.01 to 0.1 MPa.

  By the etching as described above, anisotropic etching in which the value of the etching factor (Ef) is larger than 5 can be performed.

  In the present invention, since the wiring 11 is formed by the subtractive method, an undercut portion unlike the wiring formed by the semi-additive method does not occur at the bottom of the wiring 11. Therefore, there is no wiring peeling caused by a decrease in adhesion due to the undercut portion, and the flexure substrate for suspension manufactured by the manufacturing method according to the present invention has a configuration having a high adhesion reliability wiring. Become.

  Finally, as shown in FIG. 4D, the resist pattern 15 is peeled off to obtain the flexure substrate for suspension according to the present invention.

  Although not shown in FIG. 4, a cover layer may be formed so as to cover the wiring 11. The cover layer can be formed, for example, by photoengraving non-photosensitive polyimide.

  As described above, according to the method for manufacturing a flexure substrate for suspension according to the present invention, the wiring of the flexure substrate for suspension can be formed by anisotropic etching with an etching factor (Ef) larger than 5. Since the wiring has a substantially rectangular cross-sectional shape and the capacitance between the wirings can be increased, a suspension flexure substrate with reduced impedance can be obtained.

In addition, according to the method for manufacturing a flexure substrate for suspension according to the present invention, since the wiring of the flexure substrate for suspension is formed by the subtractive method, an undercut portion such as the wiring formed by the semi-additive method is generated. Does not occur. Therefore, a suspension flexure substrate having wiring with high adhesion reliability can be obtained without increasing complicated processes.
[suspension]
Next, the suspension according to the present invention will be described.

  The suspension according to the present invention includes the above-described suspension flexure substrate, and usually further includes a load beam. The suspension flexure substrate is the same as described above, and is not described here. The load beam can be the same as the load beam used for a general suspension.

In the suspension according to the present invention, by using the above-described suspension flexure substrate, it is possible to cope with a finer or higher density wiring design.
[Suspension with head]
Next, the suspension with a head according to the present invention will be described. A suspension with a head according to the present invention includes the above-described suspension and a magnetic head slider mounted on the suspension.

  Since the suspension is the same as described above, description thereof is omitted here. Further, the magnetic head slider can be the same as the magnetic head slider used in a general suspension with a head.

In the suspension with a head according to the present invention, by using the above-described suspension, it is possible to cope with a finer or higher density wiring design.
[Hard disk drive]
Next, the hard disk drive according to the present invention will be described. A hard disk drive according to the present invention includes the above-described suspension with a head.

  The hard disk drive according to the present invention has at least a suspension with a head, and normally, the suspension with the head further writes and reads data, a spindle motor that rotates the disk, an arm connected to the suspension with the head, and A voice coil motor for moving the magnetic head slider of the suspension with head; Since the suspension with a head is the same as described above, description thereof is omitted here. As other members, the same members as those used in a general hard disk drive can be used.

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

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

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
20 μm thick SUS is used for the metal support substrate 14, 10 μm thick polyimide is used for the insulating layer 13, the conductor thin film layer 12 </ b> A is sputter-deposited with a Cr layer of 30 nm in thickness, and Cu is 100 nm in the upper layer. A base material using a 9 μm thick Cu film formed by electrolytic plating is prepared for the wiring conductor layer 11A using a multilayer film formed by sputtering at a thickness of 5 mm, and the wiring pitch is set using a dry film resist. A resist pattern 15 of 30 μm was formed, and the wiring conductor layer 11A exposed from the opening of the resist pattern 15 was spray-etched to form the wiring 11 of the flexure substrate for suspension according to the present invention.

  Ferric chloride added with ADEKA Adekapluronic TR-704 (compound in which ethylene oxide and propylene oxide were added to activated hydrogen of ethylenediamine. Molecular weight 5000, ethylene oxide content 40% by weight) was added to the etching solution. .89 wt%) aqueous solution was used, and the spray pressure of spray etching was 0.05 MPa.

  Thereafter, the resist pattern 15 was peeled off, the conductor thin film 12 at the bottom of the wiring 11 was left, and the other exposed conductor thin film layer 12A was etched away to obtain a flexure substrate for suspension according to the present invention.

  The cross-sectional shape of the wiring 11 obtained as described above was observed with a laser microscope, and the width (B) at the bottom of the wiring and the width (T) at the top of the wiring were measured.

  As a result of the observation, no undercut was observed at the bottom of the wiring 11, the width (B) of the bottom of the wiring was 15.0 μm, and the width (T) of the top of the wiring was 12.8 μm.

  Since the height (H) of the wiring is 9 μm, which is the same as the thickness of the wiring conductor layer 11A, the value of 2H / (BT), that is, the value of the etching factor (Ef) was 8.2.

DESCRIPTION OF SYMBOLS 1 Suspension flexure board | substrate 2 Gimbal part 3 Connection terminal part 4, 11, 21, 31 Wiring 11A Wiring conductor layer 12, 22, 32 Conductive thin film 12A, 22A, 32A Conductive thin film layer 13, 23, 33 Insulating layer 14, 24, 34 Metal support substrate 15, 25, 35 Resist pattern 26 Undercut portion H Wiring height T Wiring top width B Wiring bottom width

Claims (6)

In the flexure substrate for suspension, in which a plurality of parallel wirings are formed on the insulating layer formed on the metal support substrate,
The wiring has no undercut at the bottom,
For the suspension, the relationship among the height (H) of the wiring, the width (B) of the bottom of the wiring, and the width (T) of the top of the wiring is 2H / (BT)> 5 Flexure board.   The suspension flexure substrate according to claim 1, wherein a pitch of the wiring is 30 μm or less.   The suspension flexure substrate according to claim 1, wherein a width (B) of a bottom portion of the wiring is 15 μm or less.   A suspension comprising the suspension flexure substrate according to claim 1.   A suspension with a head comprising the suspension according to claim 4 and a magnetic head slider mounted on the suspension. A hard disk drive comprising the suspension with a head according to claim 5.

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