JPH04120790A - Manufacture of flexible printed circuit board - Google Patents

Abstract

PURPOSE:To suppress dimensional shrinkage rate to a small value by increasing the width of an etching resist image larger than the width of a necessary circuit pattern by first etching, and forming it in the same width as that of a predetermined circuit pattern by second etching. CONSTITUTION:An optically curable type film 4 is laminated on a copper-plated polyimide film by using a first pattern forming negative film, and an image is printed by an exposure unit. Then, the uncured part of the film 4 is developed, peeled, exposed copper foil is then removed by etching, and the remaining film on a circuit pattern is peeled. Then, the film 4 is laminated on the surface of the part formed with a first pattern, the pattern of a second pattern forming negative film is aligned by an alignment mark 3 formed of the first pattern, and an image is printed by an exposure unit. Thereafter, the uncured part of the film is developed, peeled, then the exposed copper foil is removed by etching, and the film on the remaining pattern is peeled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of manufacturing a flexible printed wiring board for liquid crystals, etc., which requires high processing precision.

(Prior Art) As shown in FIG. 3(a), a conventional flexible printed wiring board is made of an insulating base material such as polyester, polyimide, polyether sulfone, polyether imide, polyether ether ketone, etc., which is flexible for boat fishing. 2, the metal foils are pasted together using an adhesive, and an etching resist 6 is formed in order to create the shape of the conductor 2 required for the circuit, and then, as shown in FIG. It is manufactured by selectively etching away the rough spots using a chemical solution or the like.

This selective etching is performed by forming an etching resist image 6 in the required shape on the surface of the metal foil, but it is usually carried out by screen printing resist ink or by laminating a photocurable film on the metal surface. In many cases, a method is adopted in which a film in which only the necessary circuit pattern shape is formed transparently, that is, a so-called negative film, is layered, exposed to light, and developed.

In this case, when the copper-clad laminated film used for the flexible printed wiring board is etched, the etching rate is 0.2 to 0.3% for the polyester base material and 0.0% for the polyimide base material.
．． It is known to shrink by 1 to 0.296. The reason why the base material shrinks due to etching is that when manufacturing copper-clad laminate film, it is processed in roll form, so tension is applied to prevent wrinkles from forming. This is because the stress applied to the film in the area where the foil was removed is released and the film shrinks in size. Further, the reason why the shrinkage rate is not constant is that the tension applied to the monthly charge when manufacturing the copper-clad laminate film is not constant, and the shape of the circuit pattern is not constant, so the shrinkage rate is different.

Because of this dimensional shrinkage, the processing accuracy of the pattern, the processing accuracy of the pattern and outer shape during post-processing, and the processing accuracy between multiple terminals decreases, resulting in poor formation during circuit mounting and poor connection with connectors, etc. occurs. For this reason, conventional techniques for improving the dimensional shrinkage of flexible printed wiring boards include negative films for etching resist image formation,
The circuit pattern of the screen printing mask was set to be as thick as the shrinkage of the film base material, and was made to have the dimensions required by the product after etching.

(Problem to be Solved by the Invention) However, although dimensional shrinkage is improved according to the conventional method described in 1-1, dimensional shrinkage may be affected depending on the production lot of the copper-clad laminate film and the shape and density of the circuit pattern to be formed. Because of the difference in size, negative filters and masks for screen printing have been produced by measuring the dimensional shrinkage rate for each etching process and then correcting the dimensions.

For this reason, the negative film l corrected for each etching process,
It requires a large number of masks and screen printing masks, and it takes a lot of time to measure the dimensional shrinkage rate. In addition, it requires jigs and tools such as negative film and screen printing masks, which is uneconomical and requires only a few manufacturing conditions. There was also the problem that machining accuracy was greatly affected by changes in .

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a flexible printed wiring board with excellent processing accuracy and repeatability.

(Means for Solving the Problems) In order to achieve the above objects, the present invention has the following configuration.

(1) The invention of claim 1 is a flexible print in which a circuit is formed by etching on the surface of the metal foil of base + 4 in which a film and metal foil are bonded together, and after the circuit is protected with a coverlay film, the outer shape of the circuit is processed. In a method for manufacturing a wiring board, a first etching resist image wider than the required width of a circuit pattern is formed on the surface of a metal foil of a base material for a flexible printed wiring board in which a film and a metal foil are bonded together; The metal foil exposed from the etching resist image 1 is removed by etching, and after the first etching resist image is removed, a second etching resist image having the same width as the required circuit pattern is etched onto the metal foil. It is characterized in that the metal foil formed on the remaining surface and exposed from the second etching resist image is removed by etching.

(2) The invention of claim 2 provides the method for manufacturing a flexible printed wiring board according to (1), wherein when forming the first etching resist image, a second etching resist image is formed. It is characterized by forming alignment marks at the same time.

(3) The invention of claim 3 is based on paragraph 1-(1) or (2).
In the method for manufacturing a flexible printed wiring board, a hole is made in the flexible printed wiring board base material, and this hole is used as a kite for positioning the first etching resist image and the second etching resist image. shall be.

The flexible printed wiring board used in the present invention is made of plastic films or plastics made of polyester, polyimide, polyether sulfone, polyether imide, polyether ether ketone, etc., which are used in general flexible printed wiring boards as a base material. A sheet is used, and its thickness is 0.0125 mm to 0.3 mm.
It is.

Furthermore, polyimide fill L1. It is preferable to use polyester film, tire wheel, mylar, aromatic polyamide impregnated with epoxy resin, polyester nonwoven fabric, etc. as the base material.

(Function) In the present invention, the first etching resist image is formed with a width larger than the required circuit pattern width in the first etching, and then the second etching resist image is formed to have the required circuit pattern width in the second etching. Process the image. Therefore, in the first etching, shrinkage of the base material occurs in most of the processed parts after the circuit pattern is processed into the required shape. Therefore, in the second etching, the shrinkage is only the difference between the width of the circuit pattern after the first etching and the width of the circuit pattern after the second etching, resulting in the total shrinkage of the base material. It will be possible to keep it to a minimum.

(Example) An embodiment of the present invention will be described below based on the drawings.

Example 1 FIG. 1 is a top view showing a circuit pattern used in this example. This flexible printed wiring board is first made using a base material 2 made by laminating polyimide film and copper foil.
After forming a circuit pattern on the copper foil surface by etching and then protecting the circuit with a coverlay film,
The outer shape is processed and made into a product.

As shown in FIG. 1, a conductor 1 having a desired circuit pattern shape and a positioning mask 3 are formed on the -L of the base material 2. As shown in FIG. This alignment mark 3 is a guide mark for forming the second etching resist image, and is provided at the same time as forming the first etching resist image.

Separately from the alignment mark 3, a hole is made at a set location in the base material 2, and this hole can be used as a guide for alignment of the first etching resist image and the second etching resist image.

In this example, the circuit pattern used was a parallel pattern in which the conductor width and conductor gap were both 0.3 mm, the conductor length was 50 mm, and the number of conductors was 30.

Then, as a first pattern forming negative film, the conductor width was 0.4 mm, the conductor gap was 0.2 mm, and the conductor length was 5 mm.
A negative film with a diameter of 0 mm and 30 conductors was used. In addition, as a negative film for forming a second pattern, the conductor width and conductor gap, which are the same dimensions as the required pattern, are both zero.
．． A negative film having a length of 3 mm, a conductor length of 50 mm, and 30 conductors was used.

When forming a circuit pattern on the above-mentioned flexible printed wiring board, first, a first pattern forming negative film is used, and a photocurable film 4 is placed on the copper-clad polyimide film.
An image was printed on the laminated product using an exposure machine (FIG. 2(a)).

Next, after developing and peeling off the uncured portion of the precurable film 4, the exposed copper foil was removed by etching, and the photocurable film 4 of the remaining circuit pattern ball was peeled off (see Figure (b).
)).

Next, a photocurable film 5 is laminated on the surface of the part on which the first pattern is formed, and the pattern of the second pattern forming film 5 is aligned using the alignment marks 3 formed in the first pattern, and the exposure machine The image was printed using the following steps ((C) in the same figure).

Next, after developing and peeling off the uncured portion of the photocurable film 5, the exposed copper foil was removed by etching, and the remaining photocurable film 5 of the circuit pattern-L was peeled off (see Figure 1).
d)).

A flexible printed wiring board was obtained by the above method.

Example 2 A flexible printed wiring board was produced in the same manner as in Example 1, except that a polyester film was used as the base material 1.

Comparative Example 1 A flexible printed wiring board was produced by the stud method of Example 1, except that only the second pattern forming NECA film used in the example was used.

Comparative Example 2 A flexible printed wiring board was produced in the same manner as Comparative Example 1 except that a polyester film was used as the base material.

By the methods of Example 1.2 and Comparative Examples 1 and 2 above,
Five products were produced for each product. The dimensional shrinkage rate (%) between the conductors of the flexible printed wiring board thus produced was measured.

The results are shown in the table.

As is clear from this table, the flexible printed wiring board manufactured by the method of the present invention has a dimensional shrinkage rate of 40 to 509% compared to the product of the comparative example in which etching was performed in one step.
A good result of 6 less was obtained.

(Effects of the Invention) As explained in Section 2 below, according to the present invention, the width of the etching resist image is made wider than the required circuit pattern width in the first etching, and the predetermined circuit pattern is etched in the second etching. Since the pattern is formed to the same width as the width, compared to the conventional method of forming the pattern by etching only once, the τJ
A method for manufacturing a flexible printed wiring board with excellent repeatability can be obtained.

In particular, in the invention of claim 2, since the alignment mark is formed simultaneously with the first etching resist image, it is possible to reduce the number of manufacturing steps without requiring special jigs and tools.

Further, in the invention according to claim 3, since the hole is used as a guide for positioning the first and second etching resist images,
Even if the manufacturing conditions change, the processing accuracy of the circuit pattern can be further improved.

[Brief explanation of drawings]

FIG. 1 is a -Y plane view showing a circuit pattern used in an embodiment of the present invention, FIGS. 2(a) to (d) are process sectional views explaining an embodiment of the present invention, and FIG. (a) and (b) are process cross-sectional views each illustrating a conventional example. 1.-Conductor 2...Base material 3...Alignment mark 4...Photocurable film 1, (first etching resist image) 5...Photocurable film (second etching resist image) ) ~ Hehehe

Claims (3)

[Claims] 1. In the manufacturing method of flexible printed wiring boards, a circuit is formed by etching on the metal foil surface of a base material made by laminating a film and metal foil, and after protecting the circuit with a coverlay film, the outer shape of the circuit is processed. A first etching resist image wider than the width of the required circuit pattern is formed on the metal foil surface of the flexible printed wiring board base material on which the foil is bonded, and the metal foil exposed from this first etching resist image is After removing the first etching resist image by etching, forming a second etching resist image having the same width as the required circuit pattern on the remaining surface of the metal foil,
A method for manufacturing a flexible printed wiring board, comprising etching away the metal foil exposed from the second etching resist image. 2. When forming the first etching resist image,
2. The method of manufacturing a flexible printed wiring board according to claim 1, further comprising forming alignment marks for forming the second etching resist image at the same time. 3. 3. A method according to claim 1, wherein a hole is formed in the flexible printed wiring board base material, and the hole is used as a guide for positioning the first etching resist image and the second etching resist image. A method for manufacturing a flexible printed wiring board.