JPH0725129A - Printed wiring board - Google Patents

Abstract

PURPOSE:To sharply form the symbol mark of a printed wiring board without causing blur and make the symbol mark fine. CONSTITUTION:The symbol mark of a printed wiring board is formed by printing a photosensitive film 3 on the marking surface 1a of a printed circuit board 1 using photosensitive developing type ink and exposing the same through an exposure film 3 to develop the exposed film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a printed wiring board,
In particular, it relates to marking on a printed wiring board.

[0002]

2. Description of the Related Art A printed wiring board is usually constructed by forming a printed wiring circuit made of a conductor on one or both sides of a printed circuit board. Further, necessary components are mounted on the printed wiring circuit. It is configured by

However, markings (symbol marks) are provided on the printed circuit board of the printed wiring circuit for the purpose of displaying characters and symbols such as the type of the part, the part number, the mounting position of the part, and the road map. To be done.

Further, as the finishing specifications of the marking, the definition of characters and the prohibition of printing on the land portion are required, and the marking is generally performed by a printing method using a stencil screen. The method will be described.

As a method of forming a symbol mark using the conventional Suntesyl screen, first, a photosensitive emulsion is applied onto a screen in which a mesh of polyester, stainless steel or the like is evenly tensioned and attached to a hollow aluminum frame. At the same time, the photosensitive emulsion is exposed to light to form a photosensitive film.

Further, while the positive or negative film surface of the symbol mark to be drawn is brought into close contact with the photosensitive film, the blank image for printing is arranged directly on the screen through the steps of ultraviolet exposure and development on the film surface. . The symbol printing ink is placed on the stencil screen formed by the above, and the symbol is printed by printing the image at the mark printing position on the printed board by scraping the ink on the printed board with the squeegee through the extracted image. The mark is applied.

In addition to the symbol drawing, Japanese Patent Publication No.
As disclosed in Japanese Patent No. 41102, in order to prevent a solder bridge extending over lands during device mounting such as soldering, a "soldering resistance layer" is formed at the same time as symbol printing between lands having a relatively small interval. An application example of printing is also known.

[0008]

However, the printing method adopted in carrying out the marking step required in the manufacturing process of the printed wiring board has the following problems.

The image through the stencil screen has a practical effective line width of up to 0.15 mm (design value), and the drawing resolution is poor. When an image is drawn by a printing method, ink bleeding tends to occur due to its characteristics. The stencil screen itself, which is formed by applying tension to the mesh, has a large expansion and contraction behavior, and the printing accuracy is greatly affected by the squeegee printing pressure. Difficult to do.

Therefore, the present invention was developed to eliminate the above-mentioned drawbacks in the conventional marking, and it is possible to realize high-precision mounting capable of accommodating high-density mounting of components accompanying the high-density circuit of a printed wiring board. It is an object of the present invention to provide a printed wiring board that can be printed with a symbol mark without lowering productivity.

[0011]

The printed wiring board of the present invention is a printed wiring board having markings (symbol marks) on one side or both sides of the printed board. The marking surface of the printed board is provided with a photosensitive coating film. It is formed by providing a symbol mark formed by.

[0012]

According to the printed wiring board of the present invention, since the marking surface of the printed board is provided with the symbol mark formed of the photosensitive coating film, it is possible to prevent the occurrence of blurring development by the printing method, While improving the thinning of symbol marks such as figures, it is possible to form high-precision and high-quality symbol marks, relax the restrictions on the symbol mark design, and improve the design flexibility. Have.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method of forming a symbol mark on a printed wiring board according to the present invention will be specifically described below with reference to the drawings.

1 to 9 are explanatory views showing a printed wiring board according to the present invention. First, a desired printed wiring circuit (not shown) is formed on one surface or both surfaces of the printed circuit board 1 (for example, a copper clad laminate) via a copper foil (not shown), and then a solder resist (not shown) is formed thereon. A case where one symbol mark 2 is formed on the marking surface of the printed circuit board 1 that has been completed will be described below.

As shown in FIG. 1, when the symbol mark 2 indicating the numeral 1 is formed at a required position on the marking surface 1a of the printed circuit board 1, as shown in FIG. A stencil screen 4 for applying the film 3 to the marking surface 1a of the printed board 1 is manufactured.

The stencil screen 4 can be manufactured by the same method as a conventional stencil screen for printing a symbol mark. That is, a fiber cloth (mesh) 5 knitted from fibers such as polyester or stainless is stretched inside a rectangular frame body (not shown) formed of an aluminum hollow frame while applying uniform tension. The screen 6 is formed and a photosensitive emulsion (not shown) is formed by coating a photosensitive emulsion on the screen 6.

Thereafter, the exposed film surface of the positive or negative film is brought into close contact with the photosensitive film, exposed to ultraviolet rays, and developed to form a blank image 7 for printing on the screen 6. it can.

The blank image 7 on the screen 6 is shown in FIG.
It is formed so that a bold character 1 can be printed from the symbol mark 2 formed on the marking surface 1a of the printed circuit board 1 shown in FIG. For example, bold characters are formed using a technique such as photo reversal or laser plotter.

Using the stencil screen 4 formed as described above, the photosensitive coating film 3 is formed by locating it on the wiring position of the symbol mark 2 of the printed board 1 as shown in FIGS. That is, as shown in FIG. 3, while the stencil screen 4 is placed on the upper side of the marking surface 1a of the printed board 1, the marking surface 1a of the printed board 1 is photosensitively developed by the same method as the conventional stencil screen printing method. Type ink (eg PSR-5
Printing is performed by using 00 / MW-3, manufactured by Gosho Chemical Co., Ltd., etc.

By drying this, the photosensitive coating film 3 made of the photosensitive developing ink can be formed on the upper side of the marking surface 1a of the printed board 1 while being positioned at the position where the symbol mark 2 is formed (FIG. 4, FIG. 4). (See FIG. 5). still,
In FIG. 4, the size of the symbol mark 2 actually formed is indicated by a dotted line in comparison with the photosensitive coating film 3.

As described above, after the photosensitive coating film 3 made up of the bold type 1 is printed by using the stencil screen 4 while being positioned at the position where the symbol mark 2 is formed on the printed circuit board 1, this is exposed. ， By developing,
The symbol mark 2 shown in FIGS. 8 and 9 is formed.

That is, in order to form the symbol mark 2 by exposing and developing the photosensitive coating film 3 on the printed circuit board 1, first, the symbol mark exposure film 8 is formed.
(Positive or negative film capable of exposing the symbol mark 2 to the photosensitive coating film 3 as shown in FIG. 6) is placed and fixed while aligning the photosensitive coating film 3 and the exposed portion of the symbol mark 2 of the film 8. After that, as shown in FIG. 7, the photosensitive coating film 3 is exposed by irradiating exposure light 9 such as ultraviolet rays from above the exposure film 8.

After exposure, by developing with an alkaline aqueous solution, an organic solvent or the like, as shown in FIGS. 8 and 9, the symbol mark 2 of the numeral 1 is formed at a predetermined position on the marking surface 1a of the printed board 1. You can The symbol mark 2 formed in this manner accelerates the curing reaction by a method such as heating or ultraviolet irradiation depending on the characteristics of the ink.

In the method, the symbol mark 2 actually formed by being positioned at the position where the symbol mark 2 is formed is used.
Bold characters and the like are printed by the photosensitive coating film 3, but instead of this, the marking surface 1a of the printed circuit board 1 can be formed so that a plurality of symbol marks 2 or a plurality of symbol marks 2 in a wider range can be formed. By applying a photosensitive developing type ink to the marking surface 1a with a spray, a roll coater or the like to form a photosensitive coating layer (not shown) on the marking surface 1a, and exposing and developing it through an exposure film. Of course, it is also possible to form a plurality of symbol marks at the same time.

That is, in the case of such a method, it is not necessary to form the stencil screen 4 for forming the photosensitive coating film 3 corresponding to the symbol mark 2, but on the other hand, the area to be developed is large, which is a cost disadvantage. Occurs.

As is clear from the above description, by adopting this embodiment, it is possible to remarkably improve the sharpness of symbol drawing which cannot be obtained by the conventional printing method.

That is, by exposing and developing the flat portion having the largest ink coating film thickness in the center of the state drawn by printing, the bleeding portion generated by printing is deleted, resulting in a clearer image. And a highly accurate symbol mark can be obtained.

Further, in the current printed wiring board manufacturing process, the blurring of symbol characters caused by printing is a major cause of defects, and the application of this embodiment is basically characterized in that the blurring does not occur. From that,
It can greatly contribute to the manufacturing yield. Moreover, due to the highly accurate finish, the characters can be thinned (0.0
5 mm) and downsizing, design restrictions are relaxed, and design flexibility is improved. Further, as compared with the screen printing method, in this embodiment, since the photographic method based on the exposure to the phenomenon is applied, the control factor relating to the position accuracy is remarkably reduced, and the position accuracy is greatly improved as compared with the conventional technology. To do.

In the case of the present embodiment, as described above, it is possible to apply the ink over a wide range with a sprayer, a roll coater or the like, and to expose this to the phenomenon, but the application is limited by partial printing. As a result, the portion removed by development is reduced, that is, the amount of ink used is reduced, which leads to cost reduction.

[0030]

As described above, according to the printed wiring board of the present invention, the formed symbol mark has no blurring, and the sharpness is improved, so that the drawn character can be thinned. The position accuracy of drawing becomes high, the management factors related to the position accuracy are reduced, the design restrictions are relaxed, and the manufacturing yield can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of a printed circuit board.

FIG. 2 is a plan view of a stencil screen.

FIG. 3 is a plan view showing a printed state of a photosensitive coating film.

FIG. 4 is a plan view of a printed circuit board showing a state of formation of a photosensitive coating film.

5 is a sectional view taken along line AA of FIG.

FIG. 6 is a plan view showing an exposed state of a photosensitive coating film.

7 is a sectional view taken along line BB of FIG.

FIG. 8 is a plan view of a printed circuit board showing a symbol mark after development of a photosensitive coating film.

9 is a sectional view taken along line CC of FIG.

[Explanation of symbols]

 1 Printed circuit board 2 Symbol mark 3 Photosensitive coating film 4 Stencil screen 5 Fiber cloth (mesh) 6 Screen 7 Extracted image 8 Symbol mark exposure film 9 Exposure irradiation

Claims (1)

[Claims] 1. A printed wiring board comprising markings (symbol marks) on one or both sides of a printed circuit board, wherein the symbol marks are formed by a photosensitive coating on the marking surface of the printed circuit board. .