JPH04206677A - Manufacture of double-access flexible printed wiring board - Google Patents

Abstract

PURPOSE:To form a good circuit pattern without deformation of a conductor exposed within an access hole by executing the electrical solder plating within the access hole of a base film to form a circuit pattern and then removing the electrical solder plating. CONSTITUTION:After depositing a plating protection resist layer 12, electrical solder plating 13 is conducted to cover a meal foil 3 exposed within an access hole 9. Next, the resist layer 12 is removed, an etching resist layer 10 is formed by deposition, a circuit pattern is formed on the metal foil 3 by the etching and thereafter the resist layer 10 is removed. Next, the electrical solder plating 13 within the access hole 3 is chemically removed. The coverlay films 5 are attached with a bonding agent 4 and are pressurized for contactness with a layer-stacking press method.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a double-access flexible printed wiring board, and in particular, to a method for manufacturing a double-access flexible printed wiring board, and in particular, to produce a good circuit turn without deforming the conductor exposed on the inner wall surface of an access hole. The present invention relates to a method for manufacturing a double access flexible printed wiring board that can form a double access flexible printed wiring board.

<Prior art> Flexible printed wiring boards (hereinafter referred to as FPCs) are bendable and are widely used in various electronic devices. As shown, a base film 1, a metal foil 3 bonded to the base film 1 with a base adhesive 2, and a coverlay film 5 bonded to the metal foil 3 with a coverlay adhesive 4.
An access hole 6 for mounting components is provided only on one side.

However, in recent years, as electronic devices have become smaller and thinner, the space given to FPCs has become smaller, and in order to effectively utilize the component mounting space, access holes are provided on both sides. An FPC (hereinafter referred to as a double access FPC) has become necessary.

As shown in FIG. 3, the double access FPC has metal foils 3 bonded to both sides of a base film 1 with a base adhesive 2, and a circuit pattern is formed on both sides of the metal foils 3. A double access FPC has a double-sided (two-layer) circuit configuration in which the circuit patterns of the metal foils 3 on both sides are conductively connected to each other by the through-hole plating 8 of the through-hole 7, as shown in FIG. Although it has a single-layer circuit configuration with only one layer of metal foil 3 as shown in FIG.
PC is known.

” Among the two types of double access FPC, such as
In the case of double-access FPC with double-sided circuit configuration,
As mentioned above, since two layers of metal foil 3 are required and through-hole plating 8 is required to conductively connect the circuit patterns of metal foil 3 on both sides to each other, material costs and manufacturing costs are high. It also has drawbacks such as reduced bending resistance. For these reasons, a double access FPC having a single layer circuit configuration as shown in FIG. 4 is preferable as the tuple access FPC.

Conventionally, a double access FPC having a single layer circuit structure has been generally manufactured in the order shown in FIGS. 5(a) to 5(h), which will be explained below.

First, as shown in Figure (a), the base film 1
Adhesive 2 is applied in a layered manner to the base film 1, and then, as shown in Figure (b), an access hole 9 for mounting components is provided in the base film 1.

After this, as shown in Figure (C), the metal foil 3 is pasted on the base fill 1 with adhesive 2, and as shown in Figure (d), the metal foil 3 and the base fill 1 are each attached. The etching resist layer 10 is deposited on the metal foil 3 side by screen printing or photoprinting, and then the etching resist layer 10 on the metal foil 3 side and the metal foil 3 are coated as shown in FIGS. Etching is performed to form a circuit pattern using the metal foil 3.

Thereafter, as shown in Figure (g), the etching resist layer 10 on both sides is removed, and as shown in Figure (h), a coverlay film 5 having access holes 6 is removed.
The metal foil 3'' is laminated and bonded to the metal foil 3'' with adhesive 4.

In the case of a manufacturing method such as ``Double Series'', an etching resist layer 10 is applied to the access hole 9 provided through the base film 1 to make the metal foil 3 exhibit a WK appearance to the outside in order to protect the metal foil 3. The etching resist layer 10 is made of ordinary screen printing etching resist ink, photosensitive elatin resist film,
Alternatively, a liquid etching resist ink or the like may be used.

Further, as shown in FIG. 6, the access hole 9 is filled with a cut piece or the like produced during processing as a sealing material 11, thereby covering the exposed portion of the metal foil 3 due to the access hole 9. has been considered, and this is shown in Japanese Patent Laid-Open No. 181090/1983. In FIG. 6, parts corresponding to those in FIG. 5 are designated by the same reference numerals as those in FIG.

<Problems to be Solved by the Invention> In manufacturing a double access FPC having a single layer circuit configuration as described above, a metal foil 3 is pasted on a base film 1 in which an access hole 9 has been provided in advance, and the two are pressed together. However, since the metal foil 3 is then etched to form a circuit pattern, the metal foil 3, which is a conductor exposed in the access hole 9, is There is a problem that deformation easily occurs.

Also, when etching, the hook metal foil 3 in the access hole 9 portion is
In order to protect the access hole 9, as described above, the access hole 9 is filled with ink for screen printing etching resist, photosensitive eratin breath film, or liquid eratin breath ink. Even conductor parts are corroded, making it difficult to form good circuit patterns, and in extreme cases even leading to disconnection, which is one of the factors that lowers product yields.

As an improvement measure for this, as shown in the above-mentioned Japanese Patent Application Laid-open No. 59-181090, the access hole 9 is filled with a section etc. generated during processing as the sealing material 11, and thereby the access hole 9 is closed. It has been proposed to cover the exposed portion of the metal foil 3, but in this case, the access hole 9 is physically filled with the sealing material 11, and the sealing material 11 is also removed after etching. Due to this physical process, the conductor (metal foil 3) exposed in the access hole 9 is likely to be deformed, and for this reason, it is also difficult to form a good circuit pattern in this case, making it difficult to improve the yield of the product. I can't expect much to happen.

The present invention has been made in view of the conventional problems such as "double series", and an object of the present invention is to form a good circuit pattern without deforming the conductor exposed in the access hole. An object of the present invention is to provide a method for manufacturing a double-access flexible printed wiring board.

<Means for Solving the Problems> In order to achieve the above-mentioned objectives, in the method for manufacturing a double access flexible printed wiring board according to the present invention, adhesive or a predetermined base film coated in layers is used. Double access flexible printed wiring in which an access hole is provided in advance at a location, a metal foil serving as a conductor is bonded to the base fill with the adhesive, and a circuit pattern is formed on the metal foil after the two are pressed against each other. In the method for manufacturing the board, electro-solder plating is applied to the access holes of the base fill to which metal foil is laminated, the access holes are filled with electro-solder plating, and then a circuit pattern is formed on the metal foil to form the circuit. The method is characterized in that the electro-solder plating within the access hole is removed after forming the pattern.

Function> In the method for manufacturing a double access flexible printed wiring board according to the present invention, the sealing to fill the access hole is performed by electric solder plating, and the sealing of the access hole by electric solder plating and its removal are all Since it is performed electrochemically or chemically, a double access FPC with a good circuit pattern can be manufactured without deforming the conductor exposed in the access hole.

<Example> Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 1(a) to 1(j) show the process order of the method for manufacturing a double access flexible printed wiring board according to the present invention. In FIG. 1, the same parts as those of the conventional double access flexible printed wiring board shown in FIGS. 2 to 6 will be described with the same reference numerals as in the conventional example.

As shown in Figures (a) and (b), after coating the base film 1 with adhesive 2 in a layered manner, access holes 9 for mounting components are provided in the base film 1, and then As shown in C), a metal foil 3 is bonded to a base film 1 using an adhesive 2, and then the metal foil 3 and the base film 1 are pressed together. The steps up to this point are substantially the same as conventional ones.

The access hole 9 may be provided by press punching using a punching die, a Vic 1, a rear blade die, or the like. Incidentally, when the hole position accuracy in the access hole 9 is strict or when the hole diameter is small, it is preferable to use a punching die.

The metal foil 3 is preferably a copper foil from the viewpoints of electrical properties, bending resistance, and the like.

Possible methods for press-bonding the metal foil 3 and the base film 1 include a lamination press method and a lamination method. but,
Since the lamination pressing method may cause deformation of the metal foil 3 exposed in the access hole 9, which may lead to a decrease in product yield, it is preferable that this pressure bonding be performed by the lamination method.

Next, in the laminate of the base film 1 and the metal foil 3 obtained as described above, the surface on which the circuit pattern is to be formed,
That is, as shown in Figure (d) on the metal foil 3 side, there is a plating protective resist layer 12 that can withstand electric solder plating.
to be coated with.

This plating protection resist layer 12 can be resist ink, photosensitive film, etc., and the method of applying it is as follows:
In order to suppress deformation of the conductor (metal foil 3) exposed in the access hole 9 as much as possible, it is most preferable to apply the resist ink without applying physical force.

Next, after depositing the plating protection resist layer 12,
), electro-solder plating 13 is applied within the access hole 9 to cover the metal foil 3 exposed to the outside within the access hole.

The composition of the solder in the electrolytic solder plating 13 may be either 9:1 solder or 6:4 solder, and the thickness of the electrolytic solder plating 13 should be no greater than 'Bzm. Since excessive plating increases the time required for removal, 10μ plating is removed.
A thickness of about m is most preferable.

In this case, of course, the metal foil 3 exposed inside the access hole 9 is also subjected to the electrosolder plating 13, but if the metal foil 3 is roughened, Before performing the electric solder plating 13, it is necessary to remove the roughened surface by soft etching with chloride chloride, ferric chloride, or the like.

After applying the electric solder plating 13, the plating protection resist 5 adhering to the surface on which the circuit pattern is to be formed is removed.

As shown in Figure (f), an etching resist @10 is formed on both sides of the base material obtained in the above manner by either screen printing or photoprinting, and then As shown in Figure (g), etching is performed, a circuit pattern is formed on the metal foil 3 as shown in Figure (h), and the etching layer 10 is etched.
remove. When forming the etching resist layer 10, the etching resist layer 10 may be formed only on the side on which the circuit pattern is to be formed, but it is preferable to form it on both sides.

Further, as the liquid used for etching, an alkaline etching liquid, a sulfuric acid-hydrogen peroxide etching liquid, or the like may be used as long as it does not attack the electrosolder plating 13.

However, when using an alkaline etching solution, the etching resist layer 10 must be selected from a material that does not peel off with alkali, such as a solvent-developed photosensitive film.

Next, as shown in Figure (i), the access hole 3
The electric solder plating 13 inside is removed.

This removal may be carried out using a nitric acid-hydrofluoric acid mixed solution or the like.

Next, as shown in Figure (j), a coverlay film 5, which has access holes 6 for mounting components at desired positions, is attached to the base material after the circuit pattern is formed using an adhesive 4. They are bonded together and pressed together using a lamination press.

The access hole 6 in the coverlay film 5 is
-Similar to the case of the base film 2 described above, it is sufficient to form the film by punching it using a press containing a punching die, a punching die, etc., and when the hole position accuracy is strict or the hole diameter is small, etc. , it may be formed by press punching using a punching die.

If plating is required within the product, after plating the desired lands, the outer shape of the product is punched out using a punching die, Victoria blade die, etc., to obtain a double access FPC.

Example 1 As base film 1, rcIsV 2535 (K
B) After forming an access hole 9 in this base film 1 with a Victoria blade die using a J made by Kkan Kogyo Co., Ltd. (trade name), this base film 1 and a rolled 35 μm copper foil rBAN-02J (as a metal foil 3) were formed. Nippon Mining Co., Ltd. (trade name) was laminated at 120℃ using a silicone rubber roll with a rubber hardness of 65 degrees at a speed change of 1.5 m/min, and dried for 24 hours in a constant temperature bath at 80℃ and 20% humidity. Then, the adhesive 2 of the base film 1 was semi-cured.
.

Then 30% by weight sulfuric acid, 2. 5 f+jff1%
Using a mixed aqueous solution of hydrogen peroxide, the surface of the copper foil forming the circuit pattern and the roughened surface of the copper foil exposed in the access hole 9 were removed by soft etching.

Resist ink rUVM on copper foil forming circuit pattern
800J was applied by screen printing method, and ultraviolet 8
After curing this resist ink by irradiating with 00 mj/crrr to obtain a plating protection resist layer 12, a current density of 3 is applied to the conductor (copper foil) exposed in the access hole 9.
A/drr1', plating time of 10 minutes, approximately 10 μm 9:
1 Electrical solder plating 13 was applied.

Etching resist layers 10 were formed on both sides of the base material obtained as described above by a screen printing method using etching resist ink rUVM800J. Etching was performed for 120 seconds using a hydrogen oxide mixture to form a circuit pattern. After this, the remaining etching lens (etching lens) and ink remaining in the solution are peeled off and removed using a 2.5% by weight aqueous sodium hydroxide solution. The electrolytic solder plating 13 was removed using the same method.

Then, an access hole 6 is provided in advance using the blade die 5,
The cover 4z' film 5 rCISV 2535 (KB) manufactured by J Nikkan Kogyo Co., Ltd. (trade name), which had been subjected to the necessary processing, was laminated to the above semi-finished product, and heated at a heating platen temperature of 170°C and a molding pressure of 3. Pressure bonding was carried out by lamination pressing at 43×10 6 pa for 60 minutes.

Furthermore, the access hole 6 of the laminated product as described above is
．． 9 was subjected to 9=1 electro-solder plating of about 10 μm at a current density of 3 A/drrl' and a plating time of 10 minutes,
The outer shape of the product is punched out using a press using a punching die.
Obtained double access FPC.

Example 2 As the base film 1, rCISV 5035 (
After forming an access hole 9 in this base film 1 with a punching die using Nikka Kogyo Co., Ltd. (trade name), this base film 1 and a rolled 35 μm copper foil rBAN- as a metal foil 3 were formed. 02J (manufactured by Nippon Mining Co., Ltd.; trade name) was laminated at 120°C using a silicone rubber roll with a rubber hardness of 65 degrees at a speed of 1.5 m/min, and then placed in a constant temperature bath at 80°C and 20% humidity for 24 hours. After drying, the adhesive of the base film was semi-cured.

Then, using a mixed aqueous solution of 30% by weight 96% sulfuric acid and 2.5% by weight hydrogen peroxide, the surface of the copper foil forming the circuit pattern and the roughened surface of the copper foil exposed in the access hole 9 are softened. It was removed by etching.

Photosensitive film rPHT on copper foil to form circuit pattern
-887AF-25J is applied by lamination, and the photosensitive film is cured by irradiating ultraviolet rays of 60 mj/cm' with an exposure device to obtain the plating protection resist layer 12, and then the conductor exposed in the access hole 9 is At a current density of 3 A/d and a plating time of 10 minutes, the plating time was approximately 10. clm
9=1 electric solder plating 13 was applied.

After laminating the photosensitive film rPHT-143-50J on the surface of the base material obtained in the above manner on which the circuit pattern is to be formed, the photosensitive film is irradiated with ultraviolet rays of 800 mj/crt+' using an exposure device to make it photosensitive. The film was cured and developed for 90 seconds with 1°1, 1-) dichloroethane at a liquid temperature of 25°C to form an etching resist layer 10.
was formed.

After forming the etching resist layer 10, the solution temperature is 50°C.
9 using an alkaline etching solution consisting of "Knee Process" (manufactured by Japan Metal Finishing Co., Ltd.; trade name).
After etching for 0 seconds and forming a circuit pattern,
The photosensitive film was peeled off and removed using methylene chloride at room temperature, and then removed using "Metsukurimover-3-3-" at a liquid temperature of 40°C.
The electric solder plating 13 was removed using 6KMJ (manufactured by MEC Co., Ltd.; trade name).

Then, the coverlay film 5 is prepared with an access hole 6 using a blade mold and subjected to necessary processing.
rc I SV 5035 (KB) J manufactured by Nikkan Kogyo Co., Ltd. (trade name) was laminated to the above semi-finished product and heated at 60°C at a heating platen temperature of 170°C and a molding pressure of 3.43 x 106pa.
They were laminated and pressed together for a minute.

Furthermore, the access hole 6.9 of the product laminated as described above was plated with a current density of 3 A/drrl'' and a plating time of 10.
After applying 9:1 electro-solder plating to a thickness of about 10 μm, the outer shape of the product was punched out using a punching die to obtain a double access FPC.

According to these examples, it was possible to obtain a double access FPC with a good circuit pattern without causing deformation of the conductor exposed in the access hole 6.9.

<Effects of the Invention> As can be understood from the above explanation, according to the method for manufacturing a double access flexible printed wiring board according to the present invention, electric solder is applied electrochemically into the access hole of the base fill formed by laminating metal foil. After plating, a circuit pattern is formed on the metal foil, and then the electrical solder buildup inside the access pole is chemically removed. Double-access FPCs with circuit turns can be manufactured with high yield.

[Brief explanation of the drawing]

FIGS. 1(a) to (j) are cross-sectional views showing each step of the method for manufacturing a tuple access flexible printed wiring board according to the present invention, FIG. 2 is a cross-sectional view showing the general structure of the flexible printed wiring board, and FIG. 3 is a cross-sectional view showing the general structure of a double-access flexible printed wiring board with a double-sided circuit configuration, FIG. 4 is a cross-sectional view showing the general structure of a double-access flexible printed wiring board with a single-sided circuit configuration, and FIGS. 6
Each figure is a cross-sectional view showing each step of a conventional method for manufacturing a double-access flexible printed wiring board with a single-sided circuit configuration. 1...Base film 2...Adhesive 3...Metal foil 4...Adhesive 5...Coverlay film 6...Access hole 7...Through hole 8...Through hole plating 9... Access hole 10... Etching resist layer 11... Sealing material 12... Plating protection resist layer 13... Electric solder plating Figure 1 Figure 2 Figure 5

Claims (1)

[Claims] 1. An access hole is provided in advance at a predetermined location on a base film coated with a layer of adhesive, and a metal foil serving as a conductor is bonded to the base film using the adhesive, and after the two are pressed against each other, the metal foil In a method for manufacturing a double-access flexible printed wiring board in which a circuit pattern is formed on a base film, electro-solder plating is applied to an access hole in a base fill to which a metal foil is laminated, and the access hole is filled with electro-solder plating. A method for manufacturing a double access flexible printed wiring board, characterized in that a circuit pattern is later formed on the metal foil, and after the circuit pattern is formed, the electrolytic solder plating in the access hole is removed.