JP3061206B2 - Manufacturing method of metal mask - Google Patents

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 metal mask for screen printing, which is used for manufacturing, for example, a lead frame for an IC chip and a wiring pattern printed circuit board of a hybrid IC.

[0002]

2. Description of the Related Art It is known that electroforming is used as a method for manufacturing a metal mask of this type. At the time of the electroforming, for example, as shown in FIG. 4 (A) to FIG. 4 (D), a process chart of the manufacturing process is shown, and first, as shown in FIG.
A film-like photoresist 2 on the surface of
On the photoresist 2, a film 3 having a pattern (network pattern) corresponding to a mask pattern is closely adhered and baked, followed by development processing to form a resist film 4 as shown in FIG. Then, an electrodeposited metal 10 is electrodeposited on the surface of the electroformed mold 1 not covered with the resist film 4 as shown in FIG. 2C, and then as shown in FIG. The electrodeposited metal 10 is peeled off from the electroformed mold 1,
By removing the resist film 4, an electroformed product of a metal mask is obtained.

[0003]

However, when the metal mask is relatively thick, the photoresist 2 is laminated with two or three layers as shown in the figure. , Exponentially rays (ultraviolet rays)
As a result, ultraviolet rays hardly reach the position of the electroformed mold 1, the amount of ultraviolet rays reaching the lower layer portion of the resist film 4 on the side of the electroformed mold 1 is reduced, and surface hardening precedes. Since the lower layer portion 4a is apt to be uncured, defects such as the lower layer portion 4a of the resist film 4 being easily peeled off or floating from the electroformed mold 1. When electroforming is performed in this state, the electrodeposition escapes to the peeling or floating portion of the lower layer portion 4a of the resist film 4, and as shown in FIG.
Is easy to occur. For this reason, the adhesiveness of the metal mask to the surface of the printed material is deteriorated, and the solder paste oozes during printing of the solder paste or the like and easily wraps around the back of the metal mask, resulting in poor printing accuracy. On the contrary, when the exposure amount is increased, the ultraviolet rays reach the lower side of the film 3 as shown by a broken line in FIG. 6A, and the resist film 4 requires as shown in FIG. 6B. The opening 9 is enlarged and hardened more than the width W, and the size of the cross section of the opening 9 becomes smaller than the size actually required. Such a phenomenon applies to plasma irradiation, ion beam irradiation, and the like in addition to ultraviolet rays.
Therefore, an object of the present invention is to further develop and improve the above-described electroforming method of a metal mask to obtain a metal mask which eliminates burrs and enables sharp printing with high precision and sharpness of pattern edges. is there.

[0004]

According to the present invention, as shown in FIG. 1, a step of forming a resist film 4 such as a photoresist having a pattern corresponding to a mask pattern on the surface of an electroformed mold 1. A step of electrodepositing a primary electrodeposition layer 5 having a thickness smaller than the thickness of the resist film 4 on a surface of the electroforming mold 1 not covered with the resist film 4; After performing a peeling process, a step of forming the secondary electrodeposition layer 6 by secondary electroforming and a step of peeling the secondary electrodeposition layer 6 from the primary electrodeposition layer 5 are performed. To obtain a metal mask consisting of:

[0005]

When the primary electrodeposition layer 5 electrodeposited on the portion of the resist film 4 which is likely to be insufficiently exposed to light, burrs are generated and discarded, and only the secondary electrodeposition layer 6 electrodeposited thereon is formed. Is peeled off to form a metal mask, so that a metal mask without burrs can be obtained.

[0006]

According to the present invention, two primary electrodeposition layers 5
By forming the secondary electrodeposition layer 6 and using the secondary electrodeposition layer 6 as a metal mask, it is possible to obtain a high-precision metal mask with a sharp pattern edge without burrs and screen printing with high resolution. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a metal mask according to the present invention will be described with reference to FIGS. First, as shown in FIG. 1A, a film-shaped photoresist 2 is superposed on the surface of a stainless steel electroformed mold 1 to form a uniform thick film of, for example, 150 to 200 μm. As the photoresist 2, a negative type alkaline resist using a polymer obtained by copolymerizing methacrylic acid, itaconic acid or the like using sodium carbonate and sodium hydroxide as a developing and stripping solution, respectively, is used. For example,
"H-F2" of "Photoc" manufactured by Hitachi Chemical Co., Ltd.
"40" (layer thickness 40 m) or "HS-250" (layer thickness 50 m) is preferable, and when used as a permanent mask, "SR-2300G" of "Phototec" manufactured by the company can be used. Next, as shown in FIG. 2B, a film 3 having a pattern (pattern) corresponding to a mask pattern is brought into close contact with the photoresist 2 and irradiated with an ultraviolet lamp, baked, developed, and dried. Then, as shown in FIG.
200 μm thick). Of course, it is also possible to use a liquid resist or a film resist laminated on a liquid resist, and depending on the properties of the resist, it is also possible to cure by exposure using excimer, plasma, or ion beam in addition to ultraviolet rays. is there. To form a permanent mask with a liquid resist, use “PHT” manufactured by Hitachi Chemical Co., Ltd.
-404V "is applied by dip coating, roll coating or curtain coating, developed with trichloroethane after exposure, and then heated to cure the contained epoxy resin. Further, Ciba-Gei mainly containing a polymer containing an epoxy group that is thermally reactive with a chalcone group.
gy Corporation "Probimer" can also be used.

Next, the electroforming mold 1 is transferred to an electroforming tank such as a nickel sulfamate bath and electroformed with nickel or a nickel-cobalt alloy, and as shown in FIG. On the surface of the mold 1 that is not covered with the resist film 4, a primary electrodeposition layer 5 is formed of electrodeposited metal having a thickness smaller than the thickness of the resist film 4 and lower than the surface height of the resist film 4. The thickness of the primary electrodeposition layer 5 varies depending on the type of exposure light such as ultraviolet rays and electron beams, and is, for example, 5 to 10 μm at the center position in the case of ultraviolet exposure.

Next, after the surface of the primary electrodeposition layer 5 is subjected to a release treatment, a secondary electroforming is performed to form the secondary electrodeposition layer 6 on the resist film 4 as shown in FIG. To a thickness of about the height of Finally, as shown in FIG.
By peeling the secondary electrodeposition layer 6 from the primary electrodeposition layer 5, an electroformed product of a metal mask as shown in FIG.

Since the metal mask made of the secondary electrodeposition layer 6 thus obtained is free of burrs, the adhesiveness to the surface of a printed material such as a printed circuit board during printing of the solder paste is improved, and the bleeding of the solder paste or the like is achieved. And the wraparound to the back of the mask was eliminated, and the printing accuracy was improved.

As shown in FIG. 2, the primary electrodeposition layer 5 has an arc-shaped cross-section because the electrodeposition grows at the skirt 5a in contact with the resist film 4 with a delay more than the center of the cross-section. Therefore, the lower surface of the secondary electrodeposition layer 6 electrodeposited on the surface side of the primary electrodeposition layer 5 is formed in a dish shape in cross section having an edge 6a over the entire periphery as shown in FIG. According to such a metal mask having a dish-shaped lower surface in cross section, for example, the pressing force of a squeegee acts on the lower surface of the dish-shaped cross section, in particular, the periphery thereof during printing, thereby improving the adhesion to the surface of a printed material such as a printed circuit board. The effect is further improved, the cut of the printing paste is good, and the effect of suppressing bleeding and wraparound to the back surface of the mask can be further enhanced. Thus, the edge of the pattern edge was extremely good, and sharp printing with very high precision was achieved even in the thin line portion.

[Brief description of the drawings]

FIG. 1 is a process explanatory view of a manufacturing process of a metal mask.

FIG. 2 is a partially enlarged cross-sectional view of a primary electrodeposition layer and a secondary electrodeposition layer.

FIG. 3 is a partially enlarged cross-sectional view of a metal mask.

FIG. 4 is a process explanatory view of a manufacturing process of a conventional metal mask electroformed product.

FIG. 5 is a perspective view of a part of the electroformed product in FIG. 4;

FIG. 6 is a process explanatory view of a manufacturing process of another conventional metal mask electroformed product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electroforming mold 4 Resist film 5 Primary electrodeposition layer 6 Secondary electrodeposition layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41C 1/14 B41N 1/24 G03F 7/12

Claims (1)

(57) [Claims] A step of forming a resist film having a pattern corresponding to a mask pattern on the surface of the electroformed mold; and forming a resist film on the surface of the electroformed mold not covered by the resist film. A step of electrodepositing the primary electrodeposition layer 5 having a thickness smaller than the thickness of the first electrode layer 4; A method for manufacturing a metal mask, comprising: a step of separating the secondary electrodeposition layer 6 from the primary electrodeposition layer 5.