JPH08181415A - Manufacture of bored circuit substrate - Google Patents

Abstract

PURPOSE: To correspond to microminiaturization by emitting laser beam directly and by forming a window by removing an unnecessary part leaving a plating metallic circuit pattern exposed in an adhesive layer surface. CONSTITUTION: A plating metallic circuit pattern 4 formed in a resist surface of a metal film 1 is buried in an adhesive layer of a substrate film 5 and made integral. Then, the metallic film 1 is peeled off together with a resist film 2 and a plating metallic circuit pattern 4 is left in an adhesive layer of the substrate film 5. Laser beam is omitted on an adhesive layer surface of the substrate film 5, and a window 7 is formed by removing a part of an unnecessary adhesive layer and the substrate film 5 leaving the plating metallic circuit pattern 4 exposed in an adhesive layer surface. During the laser irradiation, a part of the plating metallic circuit pattern 4 functions as a mask material. Therefore, precision defect caused by misregistration when a metal mask is used does not occur and flexibility of an entire of a bored circuit substrate is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a window opening circuit board used for micro precision coil products such as rotary transformers.

[0002]

2. Description of the Related Art A rotary transformer is generally used for accommodating a magnetic head or the like of a video tape recorder therein and converting a signal read by the magnetic head or the like into an electric signal. There are a type and a disc type, both of which are configured by providing windings along the circumferential direction inside a hollow cylindrical body or a disc body made of ferrite. In the cylindrical type, the provision of the winding inside the ferrite in this manner is performed as follows as an example. That is, a copper wire is wound around the outer circumference of the winding insertion tube, inserted into the inside of the cylindrical ferrite, the rolled cylinder is inflated to crimp the copper wire inside the cylindrical ferrite, and then the above-mentioned tube Is being pulled out. However, in such a case, there is a problem that miniaturization is limited and it takes time.

[0003]

Therefore, recently, a flexible printed board (hereinafter referred to as "FPC") has been used instead of the above winding.
Abbreviated) is used. This FPC
Is a copper foil laminated on a flexible plastic film, and a circuit corresponding to the winding is formed on the copper foil by etching. The FPC thus formed is mounted on the inner peripheral surface of the cylindrical ferrite. At the time of this mounting, a window is opened in a predetermined portion of the FPC by punching with a die, etching, or laser irradiation, and this window is formed into a protrusion provided on the inner peripheral surface of the cylindrical ferrite. Fitting and mounting are performed. However, due to the recent miniaturization of rotary transformers, there is a problem in accuracy and the like cannot be dealt with by punching with a die. Further, in both etching and laser irradiation, a window is opened using a mask material. However, when the mask material is used in this way, it must be accurately aligned with the proper position. However, 20
If an attempt is made to open a window with an accuracy of ˜100 μm, a positional deviation will inevitably occur and the window cannot be opened accurately. With such accuracy, recent ultra-miniaturization (coil pitch 90
It is not possible to meet the demand for a narrow pitch coil of μm and 7 turns.

The present invention has been made in view of such circumstances, and an object thereof is to provide a method of manufacturing a window-opening circuit board which can cope with miniaturization and is easy to manufacture.

[0005]

In order to achieve the above object, a method of manufacturing a window opening circuit board of the present invention comprises a step of etching a resist film formed on a film surface of a metal film to form a circuit pattern. , A step of performing metal plating on this circuit pattern forming surface to form a circuit pattern made of plated metal, and making the adhesive layer of the substrate film with an adhesive layer face-to-face with the above-mentioned plated metal circuit pattern forming surface. A step of squeezing and embedding the plated metal circuit pattern in the adhesive layer; and, after the embedding and integration, peeling the metal film together with the resist film to form the plated metal circuit pattern on the adhesive layer of the substrate film. There is no need to leave the plated metal circuit pattern exposed on the adhesive layer surface by directly irradiating the adhesive layer surface of the substrate film with laser. Wear agent layer and remove portions of the substrate film a configuration that includes the step of forming the window.

[0006]

According to the present invention, the surface of the metal film on which the circuit pattern is formed is subjected to metal plating, and the circuit pattern is formed by the deposited plating metal. Therefore, the conductor path made of plated metal that constitutes the circuit pattern becomes wider than the width of the conductor path of the intended circuit pattern due to the deposition of the plated metal, and the deposited metal is in a state of bulging upward. Therefore, the cross-sectional area of the whole conductor path becomes large,
The resistance of the current flowing therethrough can be reduced. Further, according to the present invention, since the above-mentioned plated metal circuit pattern formed on the resist film surface of the metal film is used to open a window as follows, the accuracy of opening the window can be greatly improved. That is, the plated metal circuit pattern formed on the resist surface of the metal film is embedded and integrated in the adhesive layer of the substrate film, and then the metal film is peeled off together with the resist film to form a plated metal on the adhesive layer of the substrate film. Leave the circuit pattern. Then, the adhesive layer surface of the substrate film is irradiated with laser to leave the plated metal circuit pattern (the back surface side portion of the circuit pattern) exposed on the adhesive layer surface, and the unnecessary adhesive layer and the substrate film portion are removed. Form a window. During the laser irradiation, the portion of the plated metal circuit pattern exposed on the adhesive layer surface acts as a mask material. As described above, according to the manufacturing method of the present invention, laser irradiation is performed without using a metal mask to remove unnecessary portions to form a window, so that the precision at the time of designing a circuit pattern is the precision of the window-opening circuit board. Therefore, unlike the case where a metal mask is used, the accuracy failure due to the positional deviation does not occur. Further, since the laser beam is directly irradiated to the plated metal circuit pattern by the laser irradiation, the plated metal conductor path forming the circuit pattern is annealed and softened. ,
The flexibility of the window-opening circuit board is improved.
The width of the plated metal conductor path is wide due to the deposition of the plated metal as described above, and the width between the conductor paths is narrowed accordingly. Therefore, the action of the laser beam on that portion is reduced, and at most, the groove is dug. The formation of this groove makes it difficult for a migration (short circuit) phenomenon to occur between adjacent conductor paths.

Next, the present invention will be described in detail.

According to the present invention, for example, a window opening circuit board is manufactured as follows. That is, a resist film 2 is formed on both surfaces of a metal film 1 such as an aluminum film as shown in FIG. 1 as shown in FIG. In this case, the material of the metal film 1 is not particularly limited, and a film such as a copper film, a stainless film, a tin film or the like is used in addition to the aluminum film. Also, the resist film 2 is not particularly limited, and a conventionally known resist film such as a negative photoresist is used. Next, as shown in FIG. 3, a conventionally known etching process is applied to the one resist film 2 to form a predetermined circuit pattern 3. Then, the metal film 1 on which the circuit pattern 3 is formed is subjected to metal plating to form a plated metal circuit pattern 4 made of a deposited plating metal as shown in FIG. Reference numeral 4a is a conductor path forming a circuit pattern.
In this case, the metal plating is usually performed using a plating bath. When the plating process is performed in this manner, the conductor paths 4a forming the circuit pattern 4 grow in the illustrated width direction (arrow A direction) and in the upward direction due to the deposition of the plated metal, and thus the cross-section half as illustrated. It is formed in a circular shape.
Next, with respect to the metal film on which the plated metal circuit pattern 4 is formed, as shown in FIG. 5, polyimide, polycarbonate, polyester,
The substrate film 5 made of epoxy or the like is pressed (pressed) with the surface of the adhesive layer 6 thereof aligned with the surface of the plated metal circuit pattern. As a result, as shown in FIG. 6, the plated metal circuit pattern 4 is embedded and integrated in the adhesive layer 6. When the metal film 1 together with the resist film 2 is peeled from this state, the circuit board X in which the back surface of the plated metal circuit pattern 4 is exposed from the surface of the adhesive layer 6 is obtained as shown in FIG. Next, the circuit board X is turned over and the exposed surface of the plated metal circuit pattern 4 is
Irradiation with excimer laser is performed as shown by the arrow in FIG. The excimer laser is, for example, manufactured by Nisshin Denki (NE
X-100) is used. When the excimer laser is irradiated in this way, the substrate film 5 and the adhesive layer 6
Unnecessary part (part Y on both ends of the chain line in FIG. 8)
Is removed by irradiation with laser light, and that portion is formed in the window 7 as shown in FIG. 9, and at the same time, the portion between the conductor paths of the plated metal circuit pattern acts as the laser light. It is formed in the groove 8 along the receiving conductor path 4a. FIG. 10 shows an overall perspective view of the window opening circuit board A ′ thus opened. FIG. 10 shows a window opening circuit board A '.
It shows a state in which the arch is curved. In FIG. 9, the circled part A in FIG.
The cross section cut in the A ′ direction is shown. That is, in the window-opening circuit board A ′ of FIG. 10, unnecessary portions are removed to form the window 7 by the laser light irradiation, and the conductor path 4 a is formed in the portion other than the window 7. FIG.
11 in the case of irradiating the laser beam as described above.
As shown in, the distance (trimming width) between the end of the conductor path 4a and the lowermost end of the window 7 is W ₁ , and the angle (taper angle) formed by the inclined surface connecting the uppermost end and the lowermost end of the window 7 is θ. , Conductor track 4a
When the distance between them (gap between conductor paths) is W ₂ , it is preferable to set the irradiation condition of the laser light as shown in the following mathematical formula 1. Then, the processing accuracy determined by the trimming width W ₁ is as follows. It comes to be expressed by Numerical formula 2. These mathematical expressions 1 and 2 are created based on an empirical rule derived as a result of many experiments conducted by the present inventors.

[0009]

[Equation 1]

[0010]

[Equation 2]

In the above equations 1 and 2, t ₁ and t ₂ are as follows.

T ₁ : substrate film thickness t ₂ : adhesive layer thickness (conductor thickness)

Next, examples will be described.

[0014]

Example 1 An aluminum film was used as a metal film, and a plated metal circuit pattern 4 was formed on the aluminum film in the same manner as in FIGS. In this case, a polyimide film is used as the substrate film 5, and the adhesive layer 6 is epoxy-
A urethane adhesive layer was used. Next, similarly to FIGS. 7 to 9, a window opening circuit board A ′ as shown in FIG. 10 was prepared. The circled portion A of the obtained circuit board A '
The -A 'cross section is shown in FIG. In this case, copper was used as the plating metal forming the conductor paths 4a, and the number of conductor paths 4a was seven. The dimension in this case is the thickness t of the polyimide film 5.
₁ is 25 μm, the thickness t ₂ of the adhesive layer 6 is 30 μm, and the interval (pitch) α between the conductor paths 4a made of plated metal is 90 μm.
m, the width β of the conductor path 4a is 80 μm, the inter-conductor gap W ₂
Is 10 μm, taper angle θ is 15 °, and trimming width W ₁ is 1
The groove depth between the conductor tracks was set to 4.4 μm and 20.8 μm.

[0015]

Example 2 The substrate film was replaced with polyethylene terephthalate. Other than that was carried out similarly to Example 1, and obtained the same window opening circuit board A '.

The above Examples 1 and 2 are summarized in Tables 1 to 3. In Tables 1 to 3, the condition range indicates a range that can be changed (however, the effect of the present invention can be obtained) in the above-described embodiment, and the preferable range indicates a preferable value among them.
In addition, suitable materials for the substrate film are collectively shown in Table 4.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

In the conventional method of etching FPC, the gap W ₂ between the conductors is limited to 100 μm, whereas in the above embodiment, the gap W ₂ between the conductors is 10 μm.
Since it can be set to m, it can be actually applied to a microminiature rotary transformer. Further, the trimming width W ₁ can be made considerably smaller than the conventional _one , which also contributes to miniaturization of the rotary transformer.

[0022]

As described above, according to the present invention, the plated metal circuit pattern formed on the resist surface of the metal film is embedded and integrated in the adhesive layer of the substrate film, and then the metal film is formed together with the resist film. Peel off and leave the plated metal circuit pattern on the adhesive layer of the substrate film.
Then, the adhesive layer surface of the substrate film is irradiated with laser to leave the plated metal circuit pattern (the back surface side portion of the circuit pattern) exposed on the adhesive layer surface, and the unnecessary adhesive layer and the substrate film portion are removed. Form a window. During the laser irradiation, the portion of the plated metal circuit pattern exposed on the adhesive layer surface acts as a mask material. As described above, according to the manufacturing method of the present invention, laser irradiation is performed without using a metal mask to remove unnecessary portions to form a window, so that the precision at the time of designing a circuit pattern is the precision of the window-opening circuit board. Therefore, unlike the case where a metal mask is used, the accuracy failure due to the positional deviation does not occur. Further, since the laser light is directly irradiated to the plated metal circuit pattern by the laser irradiation, the plated metal conductor path forming the circuit pattern,
Since it is annealed and softened, the flexibility of the window-opening circuit board as a whole is improved. Further, the width of the plated metal conductor path is widened by the deposition of the plated metal as described above, and the width between the conductor paths is narrowed accordingly. Therefore, the action of the laser beam on that portion is reduced, and at most, the groove is dug. The formation of this groove makes it difficult for a migration (short circuit) phenomenon to occur between adjacent conductor paths. Further, according to the present invention, the surface of the metal film on which the circuit pattern is formed is plated with metal, and the circuit pattern is formed by the deposited plating metal. for that reason,
The conductor path made of plated metal that constitutes the circuit pattern becomes wider than the width of the conductor path of the intended circuit pattern due to the deposition of the plated metal, and the deposited metal is in a state of bulging upward. Therefore, the cross-sectional area of the entire conductor path is increased, and the resistance of the current flowing therethrough can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an aluminum film used in the manufacturing method of the present invention.

FIG. 2 is a cross-sectional view of a state in which a resist film is formed on an aluminum film used in the manufacturing method of the present invention.

FIG. 3 is a cross-sectional view of the state of FIG. 2 with a pattern formed.

FIG. 4 is a cross-sectional view of the state of FIG. 3 subjected to plating metal treatment.

FIG. 5 is an explanatory view illustrating a state in which an adhesive layer-attached polyimide film is laminated on that of FIG.

6 is a cross-sectional view of the stacked state of FIG.

FIG. 7 is a cross-sectional view showing a state where the aluminum film is removed together with the resist film from FIG.

FIG. 8 is an explanatory diagram of irradiating a laser beam on that of FIG. 7.

FIG. 9 is a partial explanatory view of a state where a window is opened after laser irradiation.

FIG. 10 is an overall perspective view of a window opening circuit board.

FIG. 11 is an explanatory diagram illustrating laser irradiation conditions and the like.

FIG. 12 is a partial cross-sectional view of a window opening circuit board obtained in one embodiment of the present invention.

[Explanation of symbols]

 1 Metal Film 2 Resist Film 3 Circuit Pattern 4 Plated Metal Circuit Pattern 4a Conductor Path 5 Substrate Film 6 Adhesive Layer 7 Window 8 Groove

Claims (1)

[Claims] 1. A step of etching a resist film formed on a film surface of a metal film to form a circuit pattern, and metal plating is applied to the circuit pattern forming surface to form a circuit pattern made of a plated metal. And a step of causing the adhesive layer of the substrate film with an adhesive layer to face the plated metal circuit pattern forming surface and pressing to integrate the plated metal circuit pattern in the adhesive layer. After the embedding integration, a step of peeling the metal film together with the resist film to leave the plated metal circuit pattern in the adhesive layer of the substrate film, and directly irradiating the adhesive layer surface of the substrate film with a laser to the adhesive layer surface. A window opening circuit board including a step of forming a window by removing an unnecessary adhesive layer and a portion of a substrate film while leaving an exposed plated metal circuit pattern. How to make a board.