JPH07251493A - Manufacture of metal mask - Google Patents

Abstract

PURPOSE:To remove a burrlike protrusion and the parting properties of ink by, peeling off an electrodeposition layer formed on a surface not covered by the resist film of a matrix, then half-etching, to begin with, the matrix face side of the electrodeposition layer, and electrolytically polishing the etched face side. CONSTITUTION:When manufacturing a metal mask, first a photoresist 2 is applied to the surface of a matrix 1, and at the same time, a film 3 with a specified pattern is closely attached to the upper surface of the photoresist to form a resist film 4. Next, the matrix is electrically cast, then an electrodeposition layer 5 is formed on a surface not covered by the resist film 4 of the matrix 1, and the electrodeposition layer 5 is peeled off the matrix 1. After that, the electrodeposition layer 5 is half-etched. That is, a resist 6 is formed on the opposite surface side of the electrodeposition layer 5 to deposit a stiffening plate 7 electrically. At the same time, a pattern resist 8 is formed on the matrix face side. Thus a recessed part 9 is formed in the part not covered by the pattern resist 8, and later, a burrlike protrusion 11 is removed by polishing the etched surface of the electrodeposition layer 5 electrically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal mask for screen printing, which is used for producing a lead frame for an IC chip, a wiring pattern printed circuit board for a hybrid IC and the like.

[0002]

2. Description of the Related Art As an example of this type of metal mask, there is an electroformed product as shown in FIGS. In the electroformed product of this metal mask, the electrodeposition layer 5 having the through holes 10 of a predetermined pattern is formed by electroforming, and then the recessed surface 9 is formed by half etching to lower a part of the electrodeposition layer 5 to lower it. I will do it. The recessed surface 9 is formed so as to have a change in printing thickness. A process diagram of the manufacturing process is illustrated in FIGS. First, as shown in (A) of the same figure, a resist film 4 having a desired pattern (mesh pattern) is formed on the surface of the mother die 1, and then, as shown in (B) of the same figure, the resist of the mother die 1 is formed. A metal is electrodeposited on the surface not covered with the film 4 to form an electrodeposited layer 5. After electroforming, the electrodeposition layer 5 is peeled from the matrix 1 as shown in FIG. Thus, half-etching was performed from the master surface side of the electrodeposition layer 5 to form the recessed surface 9 as shown in FIG.

[0003]

However, in the metal mask thus obtained, as shown in FIG. 6, a flash-like projection 11 is formed at the edge of the through hole 10 on the etching surface side. It is considered that this is due to the way the electrodeposition layer 5 grows. That is, as shown in the enlarged view of the structure of the electrodeposition growth method in FIG. 5B, the central portion 5a of the electrodeposition layer 5 which is separated from the resist film 4 grows in advance, and The growth of the end portion 5b on the contact side tends to be delayed. After the electrodeposition layer 5 formed through such growth is peeled from the master mold 1 and half-etched from the master mold surface side, the electrodeposition formation layer 5 is etched along the electrodeposition formation layer as shown in FIG. 5D. As a result, the flash-like protrusions 11 are generated at the edges of the through holes 10. Depending on the etching conditions, the cross section of the protrusion 11 may have an acute angle as shown by 11a in FIG. 6 or may have a rounded solitary shape as shown by 11b.

When the flash-shaped projection 11 is formed on the edge of the through hole 10 on the etching surface side of the metal mask in this way, when the etching surface side is used as a squeegee hanging surface during printing, the projection 11 is formed by the squeegee. May fall into the through holes 10, hinder the ability of the ink or the solder paste to escape from the through holes 10, or damage the squeegee. The object of the present invention is to solve such a problem, and an object of the present invention is to provide a method for manufacturing a smooth metal mask having no protrusion by adding a process for removing the protrusion.

[0005]

According to the present invention, when a metal mask is manufactured, a resist film 4 having a desired pattern on the surface of a mother die 1 is illustrated in FIG.
Then, an electrodeposition layer 5 is formed by electrodeposition on the surface of the mother die 1 not covered with the resist film 4, and the electrodeposition layer 5 is peeled from the mother die 1 after electroforming. The steps up to half-etching are the same as those of the above-mentioned conventional one, but the feature is that after the etching, electrolytic polishing is performed or mechanical preliminary polishing is performed and then electrolytic polishing is performed.

[0006]

By the electrolytic polishing, the projections 11 generated by the half etching can be electrolytically removed. By adding a mechanical preliminary polishing step, the protrusions 11 which cannot be easily removed only by electrolytic polishing can be removed.

[0007]

According to the present invention, since the burr-like projections 11 formed on the edge of the through hole 10 can be removed by electrolytic polishing or by mechanical preliminary polishing and electrolytic polishing, printing is performed using this metal mask. At times, ink and solder paste can be easily removed from the through holes 10, and the plate thickness accuracy can be further improved. Therefore, printing faithful to the metal mask can be performed, and the printing accuracy can be improved. Furthermore, because the ink and solder paste can be easily removed, the number of times the metal mask is cleaned can be reduced.
It is possible to increase the number of continuous printings.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a metal mask manufacturing method according to the present invention will be described with reference to the manufacturing process of FIG. First, as shown in FIG. 1 (A), on the surface of the master mold 1 made of stainless steel,
The film-shaped photoresist 2 is overlaid. As the photoresist 2, a negative type alkaline resist is used. Then, a film 3 having a pattern corresponding to a desired mask pattern is brought into close contact with the photoresist 2 and irradiated with an ultraviolet lamp for baking, developing, and drying. As shown in FIG. Thus, the resist film 4 is formed. Although a film-shaped resist was used as the photoresist 2, it is of course possible to use a liquid resist or the like.

Next, the mother die 1 having the resist film 4 formed thereon is transferred to an electroforming bath of a nickel sulfamate bath, and electroforming is performed using nickel or a nickel-cobalt alloy. The composition and plating conditions of this nickel sulfamate bath are shown below. By performing the electroforming with a current density of 3A / dm ² ~7A / dm ² at nickel sulfamate 450 g / l boric acid 30 g / l Bath temperature 50 ° C. PH 4.0 to 4.5 above the bath, the figure Mother mold 1 as shown in (C)
The electrodeposition layer 5 is formed on the surface not covered with the resist film 4 of FIG. After electroforming, the electrodeposition layer 5 is formed on the mother die 1 as shown in FIG.
Peel from.

Then, half etching is performed from the master surface side of the electrodeposition layer 5. Therefore, the resist 6 is previously formed on the side surface of the electrodeposition layer 5 opposite to the master surface side, as shown in FIG.
Then, the pad material 7 is formed by electrodeposition. Further, a pattern resist 8 for etching is formed on the master surface side of the electrodeposition layer 5. Thus, this is immersed in an etching solution such as ferric chloride. As a result of this dipping, as shown in (F) of the figure, the portion of the electrodeposition layer 5 not covered with the pattern resist 8 on the master die surface side is corroded to form the recessed surface 9. In this case, since the etching progresses along the electrodeposition forming layer as described above, the flash-like protrusions 11 are formed on the peripheral edge of the resist film 4 to be the through holes 10.

Therefore, in the next step, the flash-shaped projection 11 is formed.
Electropolishing to remove. In electrolytic polishing, as shown in (G) of FIG.
It is dipped in 5% phosphoric acid diluted 3 times), connected to a positive electrode, and electrolyzed as an anode. Then, the etching surface side of the electrodeposition layer 5 is formed as a satin-shaped grain surface, and the flash-like protrusions 11 can be removed. In this case, for example, a carbon plate is used as the negative electrode in the electrolytic cell. After the electrolytic polishing, the patch 7 is peeled off, and the resist film 4 and the resist 6 are removed with an alkaline solution, so that the through holes 10 having a desired pattern are formed as shown in FIG.
An electroformed product of the metal mask 12 having is obtained.

When the flash-like projection 11 is an acute-angled projection 11a as shown in FIG. 6, the electric current is likely to be concentrated, so that it can be easily removed by electrolytic polishing. However, as described above, depending on the etching conditions, the projections 11 do not have an acute angle as shown in FIG. Cannot be removed. Therefore, in order to completely remove such a droopy protrusion 11b, it is desirable to perform mechanical preliminary polishing before electrolytic polishing. As the mechanical polishing, for example, rough polishing is manually performed using a grindstone of # 500 to 6000, and then final polishing is performed, or final polishing such as horn finishing, lapping, buff polishing, and belt polishing is performed. After this mechanical polishing, electrolytic polishing is further performed in the same manner as in the above embodiment.

By adding such a mechanical preliminary polishing step, it is possible to remove the avalanche-shaped projections 11b which cannot be easily removed only by electrolytic polishing. Also, mechanical polishing alone causes internal stress and causes warpage, but since electrolytic polishing is performed after polishing, the internal stress caused by such mechanical polishing is also removed and relaxed by electrolytic polishing, and flatness does not occur. It is also possible to increase burrs and remove burrs caused by mechanical polishing.

In the electropolishing step, the electropolishing surface of the metal mask can be positively satinized by setting the electrolytic solution and electrolysis conditions. For example, by increasing the current as the electrolysis condition and further stirring the electrolyte solution, a large amount of bubbles are generated to positively promote the satin formation. When the electropolished surface of the metal mask is made satin like this, the squeegee is applied to the electropolished surface side of the solder paste when printing the solder paste, so that the solder paste rolls smoothly over the matte surface of the metal mask while passing through holes. Therefore, the rolling property of the solder paste can be improved.
The present invention can be similarly applied to the manufacture of a metal mask in which the entire surface of the pattern having the through holes 10 other than the peripheral frame portion 13 as shown in FIG.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing an example of a metal mask.

FIG. 3 is an enlarged sectional view taken along line XX in FIG.

FIG. 4 is a perspective view showing another example of a metal mask.

FIG. 5 is a process explanatory view of the manufacturing process of the conventional metal mask.

FIG. 6 is an enlarged view of a part of a defective metal mask having protrusions.

[Explanation of symbols]

 1 mother die 4 resist film 5 electrodeposition layer

Claims (2)

[Claims] 1. A step of forming a resist film 4 having a desired pattern on the surface of the mother die 1, and an electrodeposition layer 5 on the surface of the mother die 1 not covered with the resist film 4.
Electrodeposition forming step, a step of peeling the electrodeposition layer 5 from the matrix 1 after electroforming, a step of half-etching from the matrix surface side of the electrodeposition layer 5, and an etching surface side of the electrodeposition layer 5. And a method for producing a metal mask, which comprises the step of electrolytically polishing. 2. A step of forming a resist film 4 having a desired pattern on the surface of the mother die 1, and an electrodeposition layer 5 on the surface of the mother die 1 which is not covered with the resist film 4.
Electrodeposition forming step, a step of peeling the electrodeposition layer 5 from the matrix 1 after electroforming, a step of half-etching from the matrix surface side of the electrodeposition layer 5, and an etching surface side of the electrodeposition layer 5. And a step of electrolytically polishing the polished surface after the mechanical polishing.