JP2008103745A - Method for manufacturing wired circuit substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a wired circuit substrate with a simple structure, which reduces transmission loss, sufficiently secures adhesion between a metal support substrate and a metal foil, and also secures a long-term excellent reliability. <P>SOLUTION: Two metal support substrates 2 are prepared, the metal thin film 3 is formed on the substrate 2, the foil 4 is formed on the film 3, a base insulating layer 5 is formed on the foil 4 and the substrate 2, a conductor pattern 6 is formed on the layer 5 as a wired circuit pattern, and an opening 9 is formed by etching in a portion opposed to the foil 4 in the substrate 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a wired circuit board, and more particularly to a method for manufacturing a wired circuit board such as a suspension board with circuit.

Conventionally, a suspension board with circuit is known in which an insulating layer made of resin and a conductor pattern made of copper are sequentially formed on a metal supporting board made of stainless steel.
In such a suspension board with circuit, since the metal support board is made of stainless steel, transmission loss increases in the conductor pattern.
Therefore, in order to reduce transmission loss, a lower conductor made of copper or a copper alloy containing copper as a main component is formed on a suspension made of stainless steel, and an insulating layer, a recording-side conductor, and a lower conductor are formed on the lower conductor. It has been proposed to sequentially form the reproduction-side conductor (for example, see Patent Document 1).
JP 2005-11387 A

However, in the above proposal, the adhesion between the suspension and the lower conductor is insufficient, and it is difficult to ensure long-term reliability.
An object of the present invention is to provide a method of manufacturing a printed circuit board that can reduce transmission loss with a simple layer structure and improve the adhesion between a metal supporting board and a metal foil and has excellent long-term reliability. There is to do.

In order to achieve the above object, a method of manufacturing a wired circuit board according to the present invention includes a step of preparing a metal support substrate, a step of forming a metal thin film on the metal support substrate, and a metal on the metal thin film. Etching a portion of the metal supporting substrate facing the metal foil, a step of forming a foil, a step of forming an insulating layer on the metal foil, a step of forming a conductor pattern on the insulating layer And a step of forming an opening.
In the method of manufacturing a wired circuit board according to the present invention, in the step of forming the metal thin film, the step of forming the metal thin film by sputtering or electrolytic plating and forming the metal foil is performed on the metal thin film. A step of forming a plating resist, a step of forming the metal foil on the metal thin film exposed from the plating resist by electrolytic plating, and a portion of the metal thin film where the plating resist and the plating resist were formed. And a step of removing.
In the method for manufacturing a wired circuit board according to the present invention, it is preferable that the metal supporting board is made of stainless steel and the metal foil is made of copper.
In the wired circuit board manufacturing method of the present invention, it is preferable that the wired circuit board is a suspension board with circuit.

According to the method for manufacturing a wired circuit board of the present invention, since a metal thin film is formed between the metal support substrate and the metal foil, transmission loss can be reduced by a simple layer configuration, and the metal support Adhesiveness between the substrate and the metal foil can be sufficiently achieved, and a printed circuit board that can ensure excellent long-term reliability can be obtained.
Moreover, according to the method for manufacturing a wired circuit board of the present invention, a metal thin film is formed on a metal support substrate, and a metal foil is formed on the metal thin film, so that the metal foil on the metal support substrate is opposed. When the opening is formed in the portion to be etched, the metal thin film becomes a barrier layer, and the metal foil can be prevented from being etched.

FIG. 1 is a cross-sectional view of an essential part showing an embodiment of a wired circuit board obtained by the method for producing a wired circuit board of the present invention.
In FIG. 1, a wired circuit board 1 is a suspension board with circuit mounted on a hard disk drive, and a metal thin film 3 is formed on a metal supporting board 2 extending in the longitudinal direction. In addition, a metal foil 4 is formed, and a base insulating layer 5 as an insulating layer is formed on the metal foil 4, and a conductor pattern 6 is formed on the base insulating layer 5. Accordingly, a cover insulating layer 7 is formed on the conductor pattern 6.

The metal support substrate 2 is made of a flat metal foil or a metal thin plate. The metal support substrate 2 has an opening 9 that faces the metal foil 4. As the metal forming the metal support substrate 2, for example, stainless steel, 42 alloy, or the like is used, and stainless steel is preferably used. Moreover, the thickness is 15-30 micrometers, for example, Preferably, it is 20-25 micrometers.
Further, the metal thin film 3 is formed as a pattern on the surface of the metal support substrate 2 so as to face the portion where the metal foil 4 is formed. Examples of the metal that forms the metal thin film 3 include chromium, gold, silver, platinum, nickel, titanium, silicon, manganese, zirconium, and alloys thereof, or oxides thereof. Moreover, the thickness is 0.01-1 micrometer, for example, Preferably, it is 0.1-1 micrometer.

In addition, the metal thin film 3 takes into account the adhesion between the metal support substrate 2 and the metal foil 4. After the metal thin film 3 is formed, the second metal thin film 3 made of a metal having high adhesion to the metal foil 4 may be laminated on the surface of the first metal thin film 3 to form a multilayer.
The metal foil 4 is formed as a pattern on the surface of the metal thin film 3 so as to face at least a portion where the conductor pattern 6 is formed. Copper is preferably used as the metal forming the metal foil 4. Moreover, the thickness is 2-5 micrometers, for example, Preferably, it is 2-4 micrometers.

  The base insulating layer 5 is formed on the surface of the metal support substrate 2 so as to cover the metal foil 4. As the insulator for forming the base insulating layer 5, a synthetic resin such as polyimide, polyether nitrile, polyether sulfone, polyethylene terephthalate, polyethylene naphthalate, or polyvinyl chloride, which is usually used as an insulator of a printed circuit board, is used. Used. Of these, a photosensitive synthetic resin is preferably used, and a photosensitive polyimide is more preferably used. Moreover, the thickness is 5-15 micrometers, for example, Preferably, it is 8-10 micrometers.

  The conductor pattern 6 is formed on the surface of the base insulating layer 5 as a wiring circuit pattern including a plurality of (for example, four) wirings arranged in parallel along the longitudinal direction at intervals. . As a conductor which forms the conductor pattern 6, metals, such as copper, nickel, gold | metal | money, solder, or those alloys normally used as a conductor of a wiring circuit board, are used, for example. Of these, copper is preferably used. Moreover, the thickness is 5-20 micrometers, for example, Preferably, it is 7-15 micrometers, The width | variety of each wiring is 15-100 micrometers, for example, Preferably it is 20-50 micrometers, The space | interval between each wiring is, for example, It is 15-100 micrometers, Preferably, it is 20-50 micrometers.

The insulating cover layer 7 is formed on the surface of the insulating base layer 5 so as to cover the conductor pattern 6. As an insulator that forms the insulating cover layer 7, the same insulator as the above-described insulating base layer 5 is used. Moreover, the thickness is 3-10 micrometers, for example, Preferably, it is 4-5 micrometers.
Such a wired circuit board 1 can be manufactured by the method shown in FIG. 2 (one embodiment of the method for manufacturing a wired circuit board of the present invention).

First, as shown in FIG. 2A, a metal support substrate 2 is prepared, and a metal thin film 3 is formed on the entire surface of the metal support substrate 2 by sputtering or electrolytic plating.
And as shown in FIG.2 (b), the resist 8 is formed in the pattern reverse to the pattern of the metal foil 4 mentioned above. For example, the resist 8 is formed by a known method in which exposure and development are performed using a dry film resist.

Next, as shown in FIG. 2C, the metal foil 4 is formed on the entire surface of the metal thin film 3 exposed from the resist 8 by electrolytic plating, preferably electrolytic copper plating, using the resist 8 as a plating resist. .
Then, as shown in FIG. 2D, the resist 8 and the metal thin film 3 where the resist 8 is formed are removed by a known etching method such as chemical etching (wet etching) or peeling.

  And as shown in FIG.2 (e), after apply | coating the solution (varnish) of the above-mentioned synthetic resin uniformly, for example on the surface of the metal foil 4 and the metal support substrate 2, it dries, and then, as needed Then, the base insulating layer 5 made of synthetic resin is formed by curing by heating. The base insulating layer 5 can also be formed as a pattern by exposing and developing a photosensitive synthetic resin. Furthermore, the formation of the insulating base layer 5 is not particularly limited to the above method. For example, a synthetic resin is formed in advance on a film, and the film is attached to the surfaces of the metal foil 4 and the metal support substrate 2 by a known adhesion. It can also be stuck through the agent layer.

Next, as shown in FIG. 2F, the conductor pattern 6 is formed in the above-described wiring circuit pattern by a known patterning method such as an additive method or a subtractive method.
For example, in the case of patterning by the additive method, first, a conductive thin film is formed on the entire surface of the base insulating layer 5 by, for example, a vacuum film forming method or a sputtering method, and the surface of the conductive thin film Then, exposure and development are performed using a dry film resist or the like to form a plating resist having a pattern that is reverse to the wiring circuit pattern. Next, the conductive pattern 6 is formed as a wiring circuit pattern on the surface of the conductive thin film exposed from the plating resist by plating, and the plating thin film and the portion of the conductive thin film on which the plating resist has been formed are removed by etching or the like. The plating may be either electrolytic plating or electroless plating, but electrolytic plating is preferably used, and among them, electrolytic copper plating is preferably used.

  For example, when patterning is performed by the subtractive method, first, a conductor layer is formed on the entire surface of the base insulating layer 5. The formation of the conductor layer is not particularly limited, and for example, the conductor layer is attached to the entire surface of the base insulating layer 5 via a known adhesive layer. Next, the conductive layer is exposed and developed using a dry film resist or the like to form an etching resist having the same pattern as the wiring circuit pattern. Thereafter, the conductive layer exposed from the etching resist is etched (wet etching), and then the etching resist is removed.

  Next, as shown in FIG. 2 (g), for example, the above-described synthetic resin solution is uniformly applied to the surface of the base insulating layer 5 so as to cover the conductor pattern 6, and then dried, and then necessary. Accordingly, the cover insulating layer 7 made of synthetic resin is formed by curing by heating. The insulating cover layer 7 can also be formed as a pattern by exposing and developing a photosensitive synthetic resin. Furthermore, the formation of the insulating cover layer 7 is not particularly limited to the above method. For example, the surface of the insulating base layer 5 is formed such that a synthetic resin is previously formed on a film and the film is covered with the conductive pattern 6. Moreover, it can also stick through a well-known adhesive bond layer.

Although not shown, the insulating cover layer 7 is formed so as to expose a portion to be a terminal portion of the conductor pattern 6. In order to expose the portion to be the terminal portion of the conductor pattern 6, it is formed into a pattern using the above-described photosensitive synthetic resin, or drilled with a laser or a punch.
Thereafter, in order to adjust the characteristic impedance, the wiring circuit board 1 is etched to remove the portion of the metal supporting board 2 facing the metal foil 4 as shown by the dotted line in FIG. Part 9 is formed. Thereby, the printed circuit board 1 is obtained.
In the printed circuit board 1 obtained in this way, as shown in FIG. 1, a metal foil 4 is laminated on a metal supporting board 2 via a metal thin film 3. Therefore, the transmission loss of the conductor pattern 6 facing the metal support substrate 2 increases only with the metal support substrate 2, whereas the metal foil 4 is interposed between the metal support substrate 2 and the conductor pattern 6 in this way. Thereby, the transmission loss of the conductor pattern 6 can be reduced. In addition, by interposing the metal thin film 3 between the metal support substrate 2 and the metal foil 4, the adhesion between the metal support substrate 2 and the metal foil 4 can be sufficiently achieved with a simple layer configuration, and is excellent. Long-term reliability can be ensured.

  In addition, since the opening 9 is formed in the metal support substrate 2 by etching in this way, the metal foil 4 is directly laminated on the metal support substrate 2 in the conventional wired circuit board. Are also etched.

  However, in this wired circuit board 1, the metal thin film 3 is laminated on the metal support substrate 2, and the metal foil 4 is laminated on the metal thin film 3. When the opening 9 is formed, the metal thin film 3 becomes a barrier layer, and the metal foil 4 can be prevented from being etched.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the examples and comparative examples.
Example 1
A 0.03 μm-thick chromium thin film and a 0.07 μm-thick copper thin film were sequentially formed as a metal thin film on a metal support substrate made of stainless steel having a thickness of 25 μm (see FIG. 2A). And the plating resist of the pattern reversed with the pattern of metal foil was formed using the dry film resist (refer FIG.2 (b)). Next, a copper foil having a thickness of 4.0 μm was formed by electrolytic copper plating on the entire surface of the metal thin film exposed from the plating resist (see FIG. 2C). Then, after removing the plating resist and the metal thin film where the plating resist was formed by chemical etching (see FIG. 2 (d)), the surface of the metal foil and the metal supporting substrate is coated with a varnish of photosensitive polyamic acid resin. After coating, the base insulating layer made of polyimide resin having a thickness of 10 μm was formed as a pattern covering the entire surface of the metal foil by exposure and development, and further heat curing (see FIG. 2 (e)). . Next, a conductive pattern having a thickness of 10 μm was formed as a wiring circuit pattern on the surface of the base insulating layer by an additive method (see FIG. 2F). Further, after applying a photosensitive polyamic acid resin varnish so as to cover the conductor pattern, exposure and development, and further heat-curing, the cover insulating layer made of polyimide resin having a thickness of 5 μm is formed on the entire surface of the conductor pattern. It was formed as a pattern covering (excluding the terminal portion) (see FIG. 2G). Thereafter, gold plating was applied to the terminal portion, and the metal support substrate was cut into a desired shape by etching to obtain a suspension board with circuit.

Example 2
A suspension board with circuit was obtained in the same manner as in Example 1 except that the metal thin film was changed to a nickel chromium alloy thin film having a thickness of 0.03 μm.
Example 3
A suspension board with circuit was obtained in the same manner as in Example 1 except that the metal thin film was changed to an electrolytic gold plating film (formed by electrolytic gold plating) having a thickness of 1 μm.

Comparative Example 1
A suspension board with circuit was obtained in the same manner as in Example 1 except that a copper foil was directly formed by electrolytic copper plating on a metal supporting board without forming a metal thin film.
Comparative Example 2
A suspension board with circuit was obtained in the same manner as in Example 1 except that the metal thin film and the metal foil were not formed.

Evaluation (Copper foil etching evaluation)
In Examples 1-3, when the metal support substrate of the suspension board with circuit obtained in each Example and each Comparative Example was etched into a predetermined shape to adjust the characteristic impedance, an opening was formed. It was confirmed that the metal thin film became a barrier layer and the copper foil as the metal foil was not etched. On the other hand, in Comparative Example 1, it was confirmed that the copper foil as the metal foil was etched.
(Transmission efficiency evaluation)
In the suspension board with circuit obtained in each example and each comparative example, the output signal strength (P _OUT ) and the input signal strength (P _IN ) are measured, and the output signal strength is expressed by the following equation (1). The transmission efficiency was evaluated as a ratio to the input signal strength. The results are shown in Table 1.

Transmission efficiency (%) = P _OUT / P _IN (1)
(Adhesion evaluation)
The suspension board with circuit obtained in each example and each comparative example was left under the condition of a temperature of −40 ° C. and then left under the condition of a temperature of 120 ° C. About the suspension board with attachment, the adhesive force between a metal support substrate and metal foil was evaluated by tape peeling. The results are shown in Table 1.

It is principal part sectional drawing which shows one Embodiment of the wired circuit board obtained by the manufacturing method of the wired circuit board of this invention. It is a manufacturing process figure which shows the manufacturing method (one Embodiment of the manufacturing method of the wired circuit board of this invention) of the wired circuit board shown in FIG. 1, Comprising: (a) is sputtering or electrolytic plating on a metal support substrate. A step of forming a metal thin film, (b) forming a resist on the metal thin film with a pattern reversed to the pattern of the metal foil, and (c) forming a resist on the metal thin film exposed from the resist. , A step of forming a metal foil by electrolytic plating, (d) a step of removing the resist and a portion of the metal thin film where the resist has been formed, and (e) on a metal supporting substrate including the metal foil, (F) forming a conductor pattern on the base insulating layer; (g) forming a cover insulating layer on the base insulating layer so as to cover the conductor pattern; Shows the process of forming .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wiring circuit board 2 Metal support board 3 Metal thin film 4 Metal foil 5 Base insulating layer 6 Conductor pattern 8 Resist 9 Opening

Claims (4)

Preparing a metal support substrate;
Forming a metal thin film on the metal support substrate;
Forming a metal foil on the metal thin film;
Forming an insulating layer on the metal foil;
Forming a conductor pattern on the insulating layer;
And a step of forming an opening by etching in a portion of the metal support substrate facing the metal foil. In the step of forming the metal thin film, the metal thin film is formed by sputtering or electrolytic plating,
The step of forming the metal foil includes
Forming a plating resist on the metal thin film;
Forming the metal foil by electrolytic plating on the metal thin film exposed from the plating resist;
The method for manufacturing a printed circuit board according to claim 1, further comprising a step of removing the plating resist and the metal thin film in a portion where the plating resist is formed. The metal support substrate is made of stainless steel, and the metal foil is made of copper,
The manufacturing method of the wired circuit board of Claim 1 or 2.   The method for manufacturing a wired circuit board according to claim 1, wherein the wired circuit board is a suspension board with circuit.

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