JPS6181692A - Mask for screen printing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to screen printing, and more particularly to a cream solder screen printing mask used when forming an electric circuit.

BACKGROUND OF THE INVENTION Conventional screen printing masks can be roughly divided into two types. The first method is to form a pattern by applying emulsion to a mesh made of various materials, and the second method is to form a pattern on a metal plate.

Problems to be Solved by the Invention However, when printing cream solder, the type in which a pattern is formed by applying emulsion to various meshes is less likely to bleed, but has the drawback of lacking durability.

Furthermore, the metal plate G pattern formed thereon has poor continuous printing properties, and is particularly prone to bleeding when printing is carried out while holding the printing material by vacuum suction. Therefore, various measures have been devised to improve these types of problems. For example, as shown in Fig. 3, there is a type of mask in which a metal mesh (metal plate 11 is made of metal and a metal plate (2) is pasted together by plating or the like is attached to a screen holder (3). Fig. 4 is an enlarged view. be.

These are good when the thickness of the paste to be printed is 100μ or less, and at most 200μ or less, such as thick film paste printing, but if the thickness of the paste to be printed is 300μ or more in a wet state, thick metal plates such as thick Saga 200μ
It is technically very difficult to connect the above items to a metal mesh by plating, which makes it difficult to manufacture.
This has not yet been achieved. In addition, a type of improvement measure in which a pattern is formed on a metal plate and attached to the frame is generally called a combination mask, and as shown in Figure 5G, an elastic film (5) is applied to the screen frame (4). ) and a patterned metal mask (6). As shown in Figure 6, when printing on printed matter (8) using the squeegee of the printing machine, the metal mask (6) is the same as the type of mask in which emulsion is applied to various meshes as shown in Figure 3. Since it bends like this and prints in a state close to line contact with the printed circuit board (8), there are relatively few bleeds, but when printing cream solder on the printed circuit board (9), the line A-0-A' in Figure 6 As shown in Fig. 7, which is a cross-sectional view of the printed circuit board (9) viewed from the direction of the arrow, there are areas where the copper foil α1 remains and areas where it does not remain on the surface of the printed circuit board (9), and solder resist etc. are further applied. lla, llb,
There remains a drawback that there are more cases of protrusion printing defects such as Ilc and Ild than in masks in which the mesh is coated with emulsion.

Means for Solving the Problems The present invention provides a screen printing mask used for screen printing, in which the portion forming the pattern to be printed is formed by overlapping a metal plate and a resin plate or resin film. It is in.

Effects of the present invention By forming the part where the pattern to be printed is formed by overlapping a metal plate and a resin plate or a resin film, the part that is pressed by the squeegee is in close contact with the printed circuit board. The printing paste, such as cream solder, is less likely to bleed, and since it is made of a metal sheet, the squeegee wears out as much as other metal masks, but the screen has a longer lifespan.

Embodiment FIG. 1 is a longitudinal cross-sectional view of a screen printing mask of the present invention.
shows.

In the figure, u is a screen frame, and ao is an elastic mesh or film (hereinafter referred to as elastic mesh).
, i+3 is a screen plate, 12a is a metal sheet, [2b is a resin film or coated resin material,
17a, 17b, 17c, and 17d indicate adhesives.

The structure of the screen printing mask of the present invention will be explained.

An elastic mesh αe is fixed to the lower surface of the screen frame a9,
A metal sheet L2a and a resin film 121) are arranged in order on the lower surface of the elastic mesh αe in close contact with the lower surface, and adhesive 1
7a, , 17cL, 17b, and 17c are adhesively fixed to each other.

FIG. 2G The case of printing cream solder using the screen printing mask of the present invention will be explained based on the A-0-Al13 sectional view seen from the direction of the arrow in FIG.

In FIG. 2, a screen plate αa consisting of a printed circuit board (9) to be printed and a pattern L2a and +2'b formed with a pattern to be printed is placed on the copper HH with a pattern formed thereon. As shown in the figure, steel foil a■, 10
The resin film L2b with high elasticity absorbs the error due to the thickness of a, 10b, IOc by its elastic deformation, and the squeegee (force Q) contacts the printed circuit board (91) closely, so it is difficult to print. It is difficult for the paste α to bleed, such as cream solder, to bleed.Furthermore, since the top surface of the screen that rubs against the squeegee (7) is made of a metal sheet, the wear of the squeegee (7) is large, as with Ike's metal masked, but the screen has a long lifespan.

In Fig. 2, the metal sheet [thickness of part 2a is 01 mm]
s, resin film t2b made from photosensitive resin film
When the thickness of the copper foil is 0.3 mm and the thickness of the copper foil is approximately 20 microns, if cream solder is printed using 250 mesh under solder powder, the metal thickness will be 0.4 m.
In the so-called combination screen of m, about 50
However, when printing was performed using the two-layer combination screen of metal and resin according to the present invention, printing could be performed approximately 750 times under the same conditions. The tongue is 6
It was at the same level as screen printing, in which a photosensitive resin laminated pattern was formed on an O-mesh stainless steel screen. However, the stainless steel screen of the 6o mesh has a short lifespan and also has the drawback of not being able to print thin patterns, so it is impossible to print solder on flat back E-C, which is an electronic component. The mesh type screen also has the disadvantage that if the viscosity of the cream solder changes slightly, the amount printed will change significantly.

In the embodiments of the present invention, the metal plate portion of the so-called combination screen has been described as having a two-layer structure of a metal sheet and a resin film, but the entire surface of the screen may have this two-layer structure.

Effects of the Invention The present invention provides a mask for use in screen printing.
By forming a pattern on a metal plate and a resin film in close contact with each other, it combines the advantages of conventional metal screens or combination screens with the advantages of screens made by coating various meshes with emulsion or laminating resin films. This has great practical effects, such as a long life with less bleeding, a reduction in the number of mask replacements during screen printing, and a reduction in the number of times the back side of the mask has to be wiped due to fewer bleeding circuits.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of the screen printing mask of the present invention, and FIG. 2 is a view of the case where cream solder is printed using the screen printing mask of the present invention, viewed from the direction of the arrow in FIG. -0-A' line cross-sectional view, Figure 3 is a cross-sectional view of a conventional mask made by plating a metal plate onto a metal mesh, Figure 4 is an enlarged view, and Figure 5 is a cross-sectional view of a conventional combination mask. Fig. 6 is a front view of the case where cream solder is printed on a printed circuit board using a combination mask with a squeegee of a printing machine, and Fig. 7 is an A-0-p view as seen from the direction of the arrow in Fig. 6! A cross-sectional view of the line is shown. 7: Squeegee 12 Clean plate 12a Metal sheet 121) Resin film 15 Clean frame 16 Elastic mesh 17a, 17b, 17c
, 17d: Adhesive patent applicant Isao Abe, Patent attorney representing Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 3 Figure 4 Figure 7

Claims (1)

[Claims] A screen printing mask used in screen printing, in which the part forming the pattern to be printed is formed by overlapping a metal plate and a resin plate or resin film.