CN115782435A - Metal mask for printing - Google Patents

Abstract

The invention provides a metal mask for printing, which can further improve the printing precision when a printing layer is formed by printing and form a printing layer with high precision and high quality. The metal mask for printing of the present invention comprises: a mask body (7) having a back surface (9) facing the printing object (2); and a plurality of through holes (10) which penetrate the mask body (7) on the front and back sides and are filled with the printing paste (4). The through hole (10) is composed of a first hole (13) that opens at the front surface (8) of the mask body (7) and a second hole (14) that is continuous with the first hole (13) and that opens at the back surface (9) of the mask body (7). One of the first hole (13) and the second hole (14) is formed by a linear hole, and the other inner surface is formed in an R-shaped cross section.

Description

Metal mask for printing

Technical Field

The present invention relates to a technique for improving printing defects such as bleeding of a printed layer and mold paste in a metal mask. Examples of the metal mask of the present invention include a printing metal mask used when a layer of a flux (printing paste) for temporarily adhering a solder ball to a substrate is formed by screen printing.

Background

The present applicant has previously proposed patent document 1 as a technique for improving the printing accuracy of a metal mask for printing. In patent document 1, the cross-sectional shape of a through hole formed in a metal mask by electroforming is formed into a tapered shape having a small aperture on the electroforming surface side and a large aperture on the electroforming mother die surface side. In printing, the electroforming surface side is the blade surface side, which is the front surface side, and the electroforming mother die surface side is the printing object (printing target) side, which is the back surface side. In forming the layer (printing layer) of the ink paste (printing paste), first, the object side of the metal mask is brought into close contact with the object, then the ink paste is placed on the squeegee surface of the metal mask, and the ink paste on the squeegee surface is extended by the squeegee and filled in the through holes. After the filling of the through holes with the ink paste is completed, the metal mask is separated from the print target, whereby the print layer on which the ink paste corresponding to the through holes is formed can be printed on the print target.

Documents of the prior art

Patent document 1: japanese patent laid-open publication No. 10-305670

In the metal mask of patent document 1, since the through-holes are formed as tapered holes extending toward the back surface side, the plate-off property of the ink paste becomes good, and therefore, when the metal mask is separated from the printing object, the separation of the metal mask and the removal of a part of the ink paste can be suppressed, and therefore, the occurrence of print defects such as bleeding and stencil printing can be prevented. However, in the metal mask of patent document 1, since the ink paste is in contact with the entire inner surface of the through-hole, the ink paste still filled in the through-hole adheres to the inner surface of the through-hole, and in a state where a part of the ink paste adheres, the metal mask may be separated from the object to be printed, and a printing defect such as a distortion of a printing shape or a printing blur may occur. Further, since the adhesion state of the ink paste is not uniform in each through hole, a printing failure in which the amount of the ink paste in each printing layer is not uniform occurs.

Disclosure of Invention

The invention aims to provide a metal mask for printing, which can further improve the printing precision when a printing layer is formed by printing and form a printing layer with high precision and high quality.

The metal mask for printing of the present invention comprises: a mask body 7 made of a thin metal plate and having a back surface 9 facing the printing object 2; and a plurality of through holes 10 which penetrate the mask body 7 on the front and back sides and are formed by circular holes filled with the printing paste 4. The through hole 10 is composed of a first hole 13 and a second hole 14, which are linear holes and open to the front surface 8 of the mask body 7, and the cross-sectional shape of the inner surface of the second hole 14 is formed into an R-shape, smoothly continues to the first hole 13 and expands, and opens to the back surface 9 of the mask body 7.

The first hole 13 may be formed by a straight circular hole, and the second hole 14 may be formed by a flared hole.

When the thickness T of the mask body 7 is set to 1, H1 defined by the hole depth of the first hole 13 is preferably set to 0.2 or more and 0.6 or less.

More preferably, when the thickness T of the mask body 7 is 1, H1 defined by the hole depth of the first hole 13 is preferably set to 0.2 or more and less than 0.5.

When the hole depth of the second hole 14 is defined as H2 and half of the enlarged size of the second hole 14 is defined as D3, the second hole 14 may be formed so as to satisfy the inequality H2 < D3.

When the opening size of the first hole 13 in the front surface 8 of the mask body 7 is defined as D1 and the opening size of the second hole 14 in the back surface 9 of the mask body 7 is defined as D2, the opening size D2 may be set to be 1.5 times or more the opening size D1.

The thickness T of the mask body 7 is preferably set to 25 μm or less.

A coating layer 17 for suppressing adhesion of the printing paste 4 is formed on the inner surface of the through hole 10 and the back surface 9 of the mask body 7. When the layer thickness of the coating layer 17 in the first hole 13 is defined as C1, the layer thickness of the coating layer 17 in the second hole 14 is defined as C2, and the layer thickness of the coating layer 17 on the back surface 9 of the mask body 7 is defined as C3, the coating layer 17 is formed so as to satisfy the inequality C1 ≦ C2 ≦ C3.

The effects of the present invention are as follows.

In the metal mask for printing of the present invention, the through hole 10 penetrating the mask body 7 on the front and back sides thereof is constituted by a first hole portion 13 formed by a linear hole opened on the front surface 8 of the mask body 7 and a second hole portion 14 formed by an inner surface having an R-shaped cross-sectional shape, smoothly continuing to the first hole portion 13 and expanding, and opened on the back surface 9 of the mask body 7. In this way, when the first hole 13 opened in the front surface 8 of the mask body 7 is formed by a straight hole, the flow direction of the printing paste 4 when filling the through-hole 10 can be guided to the hole inner surface of the first hole 13 extending in the vertical direction, and therefore the printing paste 4 can be reliably dropped into the through-hole 10 in the thickness direction (vertical direction) of the mask body 7. Further, when the inner surface of the second hole 14 connected to the first hole 13 is formed in an R-shape in cross section and is opened to the back surface 9 of the mask body 7 while being smoothly continuous and enlarged with the first hole 13, when the printing paste 4 is guided by the hole inner surface of the first hole 13 and reaches the vicinity of the boundary portion between the two holes 13 and 14, the printing paste 4 can be peeled off from the hole inner surface of the second hole 14 in the vicinity of the boundary portion. In addition, the printing paste 4 can reach the back surface 9 side of the mask main body 7 of the second hole 14 in a state of being peeled off from the hole inner surface of the second hole 14. As described above, according to the metal mask for printing of the present invention, since the printing paste 4 can be peeled off from the hole inner surface of the second hole 14 in the vicinity of the boundary portion between the two holes 13 and 14, the contact area between the hole inner surface of the through hole 10 and the printing paste 4 can be reduced as compared with the conventional metal mask, and the amount of the printing paste 4 adhering to the mask and removed from the printing object 2 can be reduced when the metal mask is separated from the printing object 2 of the mask. As described above, according to the metal mask for printing of the present invention, since the occurrence of printing defects such as deformation of the printing shape of the printing layer on the printing object 2 and printing blur can be suppressed, it is possible to improve the printing accuracy in printing the printing layer, and to form a high-accuracy and high-quality printing layer on the printing object 2.

When the first hole 13 is formed by a straight circular hole and the second hole 14 is formed by a flared hole, the inner surface shape of the through hole 10 can be formed into a smooth inner surface shape without corner portions, as compared with the case where the first hole 13 and the second hole 14 are formed by polygonal holes having corner portions, and therefore, the occurrence of printing defects such as deformation of the printing shape of the printing layer on the printing object 2 and printing blur due to the printing paste 4 adhering to the corner portions can be further suppressed.

When the thickness T of the mask body 7 is set to 1, H1 defined by the hole depth of the first hole 13 is preferably set to 0.2 or more and 0.6 or less. This is because if the hole depth H1 is less than 0.2 or if the hole depth H1 exceeds 0.6, poor printing may occur. More specifically, if the hole depth H1 is less than 0.2, the guiding effect of the printing paste 4 on the inner surface of the hole of the first hole portion 13 becomes insufficient, and the printing paste 4 is filled in an undesired direction during printing, and the shape of the printing layer is deformed or the printing layer is whitened, resulting in occurrence of printing failure. When the hole depth H1 exceeds 0.6, the printing paste 4 adheres to the inner surface of the first hole 13, and a part thereof is removed together with the metal mask, thereby deforming the shape of the printing layer or whitening the printing layer, resulting in occurrence of printing failure.

When the thickness T of the mask body 7 is set to 1, H1 defined by the hole depth of the first hole 13 is more preferably set to 0.2 or more and less than 0.5, whereby occurrence of the previous printing failure can be suppressed and a printed layer having a substantially good thickness can be obtained.

When the hole depth of the second hole portion 14 is defined as H2 and the half of the enlarged size of the second hole portion 14 is defined as D3, if the second hole portion 14 is formed so as to satisfy the inequality H2 < D3, a large curvature of the cross-sectional shape of the inner surface of the hole constituting the second hole portion 14 formed of the bell-mouth-shaped hole can be formed, and therefore, the peeling of the printing paste 4 in the second hole portion 14 can be promoted.

When the opening size of the first hole 13 in the front surface 8 of the mask main body 7 is defined as D1 and the opening size of the second hole 14 in the back surface 9 of the mask main body 7 is defined as D2, if the opening size D2 is set to 1.5 times or more the opening size D1, a large curvature of the cross-sectional shape of the inner surface of the second hole 14 formed of the bell-mouth-shaped hole can be formed, as described above, and therefore, the peeling of the printing paste 4 in the second hole 14 can be promoted.

The thickness T of the mask body 7 is preferably set to 25 μm or less. This is because the opening dimension D1 of the first hole 13 is also reduced with higher definition of the metal mask for printing, but when the thickness T of the mask body 7 exceeds 25 μm, the hole depth of the through hole 10 becomes larger than the opening dimension D1, and therefore there is a possibility that the filling of the through hole 10 with the printing paste 4 by the squeegee becomes insufficient.

When the coating layer 17 for suppressing adhesion of the printing paste 4 is formed on the inner surface of the through hole 10 and the back surface 9 of the mask body 7, the printing paste 4 can be smoothly guided by the first hole 13 and the printing paste 4 can be smoothly separated from the second hole 14. Further, the coating layer 17 may be formed so as to satisfy the inequality C1 ≦ C2 ≦ C3 when the layer thickness of the coating layer 17 formed in the first hole 13 is defined as C1, the layer thickness of the coating layer 17 formed in the second hole 14 is defined as C2, and the layer thickness of the coating layer 17 formed on the back surface 9 of the mask body 7 is defined as C3. In this embodiment, by setting the layer thickness C1 of the overcoat layer 17 to be the minimum, the change in the shape of the opening diameter D1 of the first hole 13 that defines the shape of the printed layer can be reduced. In this embodiment, by forming the layer thickness C3 to be larger than the layer thicknesses C1 and C2 of the overcoat layer 17, the effect of the overcoat layer 17 gradually worn out by contact with the printing object 2 can be maintained for a longer period of time.

Drawings

Fig. 1 is a longitudinal sectional front view showing a main part of a metal mask for printing according to a first embodiment of the present invention.

Fig. 2 is a plan view showing the entire metal mask for printing.

Fig. 3 is a vertical sectional side view showing an example of the use of the metal mask for printing.

Fig. 4 is an explanatory diagram illustrating a manufacturing process of a metal mask for printing.

Fig. 5 shows main parts of a metal mask for printing according to a second embodiment of the present invention, in which (a) is a vertical sectional front view and (b) is a bottom view.

Fig. 6 is a vertical sectional side view showing an example of the use of a metal mask for printing according to a third embodiment of the present invention.

In the figure: 1-a metal mask for printing, 2-an object to be printed (circuit board), 4-a printed matter (flux, paste), 7-a mask body, 8-a surface of the mask body, 9-a back surface of the mask body, 10-a through hole, 13-a first hole portion, 14-a second hole portion, 17-a coating layer, D1-an opening size (opening diameter) of the first hole portion, D2-an opening size (opening diameter) of the second hole portion, D3-a half of an enlarged size (diameter-enlarged size of a radius) of the opening of the second hole portion, D4-a length size (diameter) of an electrode, D5-a half of an enlarged size (diameter-enlarged size of a radius) of the opening of the first hole portion, H1-a hole depth of the first hole portion, H2-a hole depth of the second hole portion, and T-a thickness of the mask body.

Detailed Description

(first embodiment)

Fig. 1 to 4 illustrate a first embodiment of a metal mask for printing according to the present invention. The dimensions such as thickness and width in the drawings are not actual and are illustrated schematically. As shown in fig. 3, a metal mask for printing (hereinafter, simply referred to as a mask) 1 is used for forming a printed layer made of flux (printing paste) 4 for temporarily adhering solder balls by screen printing on electrodes 3 formed on a surface of a circuit board (printing object) 2.

In fig. 2, a mask 1 is made of an electrodeposited metal such as nickel, copper, or a nickel alloy such as nickel-cobalt, and a mask body 7 made of a thin metal plate formed by electroforming is used as a base, and a plurality of through holes 10 made of circular holes penetrating the mask body 7 from a front surface 8 to a back surface 9 are opened in the mask body 7. The mask 1 is formed in a square shape with one side of 250mm, and when the mask 1 is divided into four quadrants, the pattern forming region M is divided into the quadrants. The through holes 10 are provided in the pattern forming region M in a state of being arranged in an electrode pattern corresponding to the electrodes 3 of the circuit substrate 2. Around the pattern forming region M, a dicing mark forming region C for printing a dicing mark used when the circuit board 2 is diced into a predetermined shape in a step after screen printing is defined so as to surround the region M. The mask 1 is attached to a mask fixing portion of the screen printing apparatus in a state where a frame is fixed to a single body or the peripheral edge.

As shown in fig. 1, the through-hole 10 includes a first hole 13 opened in the front surface 8 of the mask body 7 and a second hole 14 opened in the rear surface 9 of the mask body 7. The first hole 13 is a linear circular hole extending in the thickness direction of the mask body 7, and the second hole 14 is a flared hole smoothly continuous with the first hole 13 and extending downward.

The thickness T of the mask body 7 is preferably 25 μm or less, and more preferably 18 μm or less. In the present embodiment, the thickness T of the mask body 7 is set to 18 μm.

When the thickness T of the mask body 7 is set to 1, the hole depth H1 (see fig. 1) of the first hole portion 13 is set to 0.2 or more and less than 0.5. The hole depth H1 in the present embodiment is set to 3.6 μm, and the hole depth H1 when the thickness T of the mask body 7 is set to 1 is set to 0.2 (3.6/18 = 0.2).

The opening size of the first hole 13, i.e., the opening diameter (diameter) D1 (see fig. 1) is set to be the same as the diameter of the layer of the flux 4 to be formed on the electrode 3. The diameter of the layer of the flux 4 is usually set to 20 μm to 50 μm, and thus the aperture diameter D1 of the present embodiment is set to 40 μm. The opening diameter D1 of the first hole 13 defines the planar shape of the printed layer to be printed, and the electrode 3 is formed with a printed layer that is circular in plan view.

The hole depth H2 (see fig. 1) of the second hole portion 14 is a dimension obtained by subtracting the hole depth H1 of the first hole portion 13 from the thickness T of the mask body 7, and is set to 14.4 μm in the present embodiment. As described above, since the hole depth H1 when the thickness T of the mask body 7 is 1 is set to be less than 0.5, the relationship between the hole depth H1 of the first hole portion 13 and the hole depth H2 of the second hole portion 14 is set to satisfy the inequality H1 < H2.

The opening size of the second hole 14, i.e., the opening diameter (diameter) D2 (see fig. 1) is set to be larger than the opening diameter D1, and in the present embodiment, the opening diameter D2 is set to be 1.5 times or more the opening diameter D1. Further, the diameter expansion dimension (half of the opening expansion dimension) D3 of the radius of the second hole portion 14 is set to be larger than the hole depth H2 (H2 < D3). The diameter expansion dimension D3 in fig. 1 is a half ((D2-D1)/2) of a value obtained by subtracting the opening diameter D1 from the opening diameter D2. The aperture diameter (diameter) D2 is preferably set to 50 μm to 100 μm, and the aperture diameter D2 of the present embodiment is set to 80 μm. Accordingly, the diameter expansion dimension D3 is set to 20 μm. In the present embodiment, since the relationship between the diameter expansion dimension D3 and the hole depth H2 is set to satisfy the inequality H2 < D3, the cross-sectional shape of the inner surface of the second hole portion 14 is formed in a quarter elliptical arc shape having a short axis in the thickness direction of the mask body 7. The opening end of the second hole 14 is smoothly continuous with the back surface 9 of the mask body 7.

The electrode 3 of the present embodiment is formed in a circular shape, and when the diameter of the electrode 3 is D4, the opening diameter D1 of the first hole 13 is formed smaller than the diameter D4, and the opening diameter D2 of the second hole 14 is formed larger than the diameter D4, in other words, the opening diameters D1 and D2 are formed so as to satisfy the inequalities D1 < D4 < D2 (see fig. 1).

As shown in fig. 1, a coating layer 17 is formed on the inner surface of the through hole 10 and the back surface 9 of the mask body 7. The coating layer 17 suppresses adhesion of the flux 4 to the hole inner surface of the through-hole 10 and the back surface 9 of the mask body 7. The layer thickness C1 of the coating layer 17 in the first hole 13, the layer thickness C2 of the coating layer 17 in the second hole 14, and the layer thickness C3 of the coating layer 17 in the back surface 9 of the mask body 7 are set to satisfy an inequality C1. Ltoreq. C2. Ltoreq. C3. Further, since the hole inner surface of the first hole 13 defines the shape of the printed layer, the thickness C1 of the coating layer 17 in this portion is formed to be thinner than other portions, thereby enabling the shape change of the opening diameter D1 to be reduced, and the thickness C3 of the coating layer 17 in this portion is formed to be thicker than other portions since the back surface 9 of the mask body 7 is in contact with the circuit board 2 when the metal mask for printing 1 is used, thereby enabling the durability to be improved. Therefore, the thicknesses C1, C2, and C3 of the coating layer 17 are set to satisfy the inequality C1. Ltoreq. C2. Ltoreq. C3, and further satisfy the formula C1. Noteq.C 3.

In the present embodiment, the layer thickness C1 is set to 0.5 μm, the layer thickness C2 is set to 0.5 μm in the portion adjacent to the first hole 13, the portion adjacent to the back surface 9 of the mask main body 7 is set to 1.0 μm, and the layer thickness C3 is set to 1.0 μm. The layer thickness C2 of the coat layer 17 in the second hole 14 is formed to gradually increase from the first hole 13 side toward the back surface 9 side of the mask body 7, and becomes a smooth coat layer 17 without a step. The coating layer 17 may be formed by dip forming or coating based on spraying. Further, although the coating layer 17 of the present embodiment is formed on the μm scale, the coating layer 17 may be formed on the nm scale.

In addition, the coating layer 17 may be set to satisfy the inequality C1 < C2 < C3. Specifically, when the layer thickness C3 is set to 1, the layer thickness C1 is set to less than 0.5, and the layer thickness C2 is set to more than 0.5 and less than 1.

The front surface 8 of the mask body 7 constitutes a squeegee surface, and when a printed layer made of the flux 4 is formed by printing, the back surface 9 of the mask body 7 is brought into direct contact with the front surface of the circuit board 2, and the electrodes 3 are brought into close contact with the through holes 10 (the mask 1 and the circuit board 2). In the printing, the flux 4 placed on the squeegee surface (front surface 8) is squeegeed by the squeegee S, the flux 4 is filled in the through-holes 10 and the openings for the dicing marks, and the printed layer made of the flux 4 is formed on the front surface of the circuit board 2 so as to match the through-holes 10 and the dicing marks. The squeegee S prints a print layer while moving from the near side (lower side in fig. 2) of the mask 1 to the back side (upper side in fig. 2) in a state where the tip thereof is in contact with the squeegee surface (surface 8 of the mask main body 7).

The flux 4 during printing is filled from the surface 8 of the mask body 7 into the first hole 13. The flux 4 that has entered the through-hole 10 is guided by the hole inner surface of the first hole 13, and enters in a state where the filling direction falls in the thickness direction of the mask body 7, that is, in a direction toward the electrode 3. The flux 4 that has entered the inside of the through-hole 10 is separated from the second hole 14 at the boundary between the first hole 13 and the second hole 14 and directed toward the electrode 3, and the flux 4 that has reached the back surface 9 of the mask body 7 is brought into contact with the electrode 3, thereby forming a printed layer made of the flux 4 as shown in fig. 3.

Fig. 4 shows a method of manufacturing the mask 1 according to the embodiment.

(patterning Process)

As shown in fig. 4 (a), after a photoresist layer 22 having a predetermined thickness is formed on the entire surface of a master mold 21 made of, for example, stainless steel or brass having conductivity, a pattern film 23 made of a glass mask having a circular shape corresponding to the through hole 10 and a linear light-transmitting hole corresponding to the scribe mark is brought into close contact with the master mold. In this state, ultraviolet light is irradiated to perform each of exposure, development, and drying. The photoresist layer 22 is formed by laminating one or more negative sheet-like photosensitive dry film resists and thermocompression bonding to have a predetermined thickness. Next, the photoresist layer 22 in the unexposed portion is removed by dissolution, and as shown in fig. 4 (b), a patterned resist 25 having a resist body 24 corresponding to the through hole 10 and the cutting mark is obtained.

(electroforming step)

The master mold 21 having the patterned resist 25 formed thereon is placed in an electroforming bath, and as shown in fig. 4 (c), an electrodeposited metal is electrodeposited in a range not to go over the upper edge of the resist body 24, thereby forming an electroformed layer 26, i.e., a layer to be the mask body 7. At this time, since the edge portion of the growth tip of the electroformed metal is grown in the shape of a quarter ellipse, the bell-mouth-shaped second hole portion 14 can be formed only by electrodepositing the electroformed metal on the master mold 21.

(peeling step)

As shown in fig. 4 (d), after the electroformed layer 26 and the patterned resist 25 are peeled off from the master mold 21, the patterned resist 25 is dissolved and removed, thereby obtaining the mask 1 shown in fig. 3. The frame may be bonded to the outer peripheral edge of the obtained mask body 7 with an adhesive, and the mask body 7 and the frame may be integrally joined without being separated, thereby forming the mask 1 including the frame.

As described above, in the mask 1 of the present embodiment, since the first hole portions 13 that open to the front surface 8 of the mask main body 7 are formed of straight holes, the flow direction of the flux 4 when filling the through-holes 10 is guided to the hole inner surfaces of the first hole portions 13 extending in the vertical direction, and the flux 4 can be reliably dropped in the thickness direction (vertical direction) of the mask main body 7. Further, since the inner surface of the second hole portion 14 is formed in an R-shaped cross-sectional shape, smoothly continues to the first hole portion 13, and is formed of a flared hole having a diameter larger than that of the rear surface 9 of the mask body 7, when the flux 4 is guided by the inner surface of the first hole portion 13 and reaches the vicinity of the boundary portion between the two hole portions 13 and 14, the flux 4 can be peeled off from the inner surface of the second hole portion 14 in the vicinity of the boundary portion. In addition, in a state of being peeled off from the inner surface of the second hole 14, the flux 4 can be made to reach the back surface 9 side of the mask body 7 of the second hole 14. As described above, according to the mask 1 of the present embodiment, the flux 4 can be peeled off from the inner surface of the second hole portion 14 in the vicinity of the boundary portion between the two hole portions 13 and 14, and therefore, the contact area between the inner surface of the through hole 10 and the flux 4 can be reduced as compared with the conventional metal mask, and the amount of the flux 4 adhering to the mask 1 and removed from the circuit board 2 can be reduced when the mask 1 is separated from the circuit board 2. As described above, according to the mask 1 of the present embodiment, since the occurrence of printing defects such as deformation of the printing shape of the printed layer on the circuit board 2 and printing blur can be suppressed, it is possible to improve the printing accuracy in printing the printed layer, and to form a high-accuracy and high-quality printed layer on the circuit board 2.

Further, according to the through-hole 10 including the first hole portion 13 formed of a linear circular hole and the second hole portion 14 formed of a flared hole, the inner surface shape of the through-hole 10 can be made a smooth inner surface shape without a corner portion, and therefore, it is possible to further suppress the occurrence of a printing failure such as a printing shape deformation or a printing failure of the printed layer on the circuit board 2 due to the flux 4 adhering to the corner portion.

When the thickness T of the mask body 7 is set to 1, H1 defined by the hole depth of the first hole 13 is preferably set to 0.2 or more and 0.6 or less. This is because if the hole depth H1 is less than 0.2 or if the hole depth H1 exceeds 0.6, poor printing may occur. More specifically, if the hole depth H1 is less than 0.2, the guiding effect of the flux 4 by the inner surface of the hole of the first hole portion 13 is insufficient, and the flux 4 is filled in an undesired direction during printing, and the shape of the printed layer is deformed or the printed layer is whitened, resulting in poor printing. When the hole depth H1 exceeds 0.6, the flux 4 adheres to the inner surface of the first hole 13, and a part of the flux is removed together with the metal mask, so that the shape of the printed layer is deformed or the printed layer is whitened, and as a result, a printing failure occurs.

Further, when the thickness T of the mask body 7 is set to 1, H1 defined by the hole depth of the first hole portion 13 is more preferably set to 0.2 or more and less than 0.5, whereby occurrence of the previous printing failure can be suppressed and a printed layer having a substantially good thickness can be obtained.

Since the second hole portion 14 is formed such that the hole depth H2 of the second hole portion 14 and the diameter expansion dimension D3 of the radius of the second hole portion 14 satisfy the inequality H2 < D3, a large curvature of the cross-sectional shape of the inner surface of the hole of the second hole portion 14 formed by the bell-mouth-shaped hole can be formed, and the peeling of the flux 4 in the second hole portion 14 can be promoted.

Since the opening diameter D2 of the second hole portion 14 is set to be 1.5 times or more the opening diameter D1 of the first hole portion 13, a large curvature of the cross-sectional shape of the inner surface of the hole of the second hole portion 14 formed of the bell-mouthed hole can be formed, and the peeling of the flux 4 in the second hole portion 14 can be promoted, as described above.

As the mask 1 is made finer, the opening diameter D1 of the first hole 13 is made smaller, but if the thickness T of the mask body 7 is made larger, the hole depth of the through hole 10 becomes larger than the opening diameter D1, and therefore, there is a problem that the flux 4 is insufficiently filled into the through hole 10 by the squeegee. In the present embodiment, since the thickness T of the mask body 7 is set to 25 μm (18 μm) or less, the flux 4 can be prevented from being insufficiently filled into the through-hole 10 by the squeegee without causing the above-described problem.

Since the coating layer 17 for suppressing adhesion of the flux 4 is formed on the inner surface of the through hole 10 and the back surface 9 of the mask body 7, the flux 4 can be guided by the first hole portion 13 and the flux 4 can be smoothly peeled off from the second hole portion 14. In addition, since the layer thickness C1 is set to be the minimum in a state where the thicknesses C1, C2, and C3 of the respective layers of the overcoat layer 17 satisfy the inequality C1 ≦ C2 ≦ C3, it is possible to reduce the shape change of the opening diameter D1 of the first hole portion 13 that defines the shape of the printed layer. Further, since the layer thickness C3 is set to the maximum, the effect of the overcoat layer 17 gradually worn by contact with the circuit substrate 2 can be maintained for a long period of time.

From the above, the metal mask for printing according to the present embodiment can contribute to the target 9 (lay a foundation for industrial and technical innovation, promote industrial containment and sustainability, expand technical innovation) of the Sustainable Development targets (SDGs: sustainable Development targets) proposed by the united nations, and the target 12 (create responsibility, ensure Sustainable consumption and production patterns).

(second embodiment)

Fig. 5 illustrates a second embodiment of a metal mask for printing according to the present invention. In the present embodiment, the shape of the through-hole 10 is different from that of the first embodiment. Note that, the overcoat layer 17 omitted in fig. 5 is illustrated, and in fig. 5 (b), a line indicating a rounded quadrangle outside one of the quadrangles of the first hole 13 is a line indicating an opening end of the second hole 14 opening on the back surface 9 side of the mask body 7.

The through-hole 10 is configured such that a first hole portion 13 opened in the front surface 8 of the mask body 7 is a linear square hole (rectangular hole), and the inner surface of a second hole portion 14 is formed into an R-shaped cross section, smoothly continues to the first hole portion 13, and is enlarged, and is opened in the back surface 9 of the mask body 7. The cross-sectional shape of the inner surface of the second hole 14 also includes a quarter-circle region at the four corners of the second hole 14 when viewed from above, and is formed in a quarter-ellipse arc shape having a short axis in the thickness direction of the mask body 7. In this way, the through-hole 10 may have a rectangular shape or a polygonal shape, and the corner of the through-hole 10 formed by a rectangular or polygonal hole may be rounded. The through-hole 10 may be formed in an elliptical shape.

The length of one side of the square hole constituting the first hole 13 in the present embodiment is set to the opening dimension D1 of the first hole 13, and the opening dimension D1 is set to be the same as the opening diameter D1 of the first hole 13 in the first embodiment described above. Under these conditions, the opening area of the first holes 13 that open to the front surface 8 of the mask body 7 is larger than that of the first embodiment by about 1.3 times. Therefore, in the printing metal mask 1 in which the opening diameter (opening size) D1 is difficult to be formed in a large size, the first hole 13 having an opening shape as in the present embodiment is effective when printing a large amount of the flux 4 on the electrode 3 is desired. Further, it is also effective when the electrode 3 is formed in a rectangular shape (rectangular shape, polygonal shape).

(third embodiment)

Fig. 6 illustrates a third embodiment of a metal mask for printing according to the present invention. In the present embodiment, the structure of the through-hole 10 is different from that of the first embodiment. Specifically, the second hole in the first embodiment is defined as the front surface side of the mask body, and the first hole is defined as the back surface side of the mask body. Note that the coating layer 17 omitted in fig. 6 is illustrated.

The through hole 10 in the present embodiment is composed of a first hole 13 opened to the front surface (blade surface) 8 of the mask body 7 and a second hole 14 opened to the rear surface (circuit board facing surface) 9 of the mask body 7. The second hole 14 is a linear circular hole extending in the thickness direction of the mask body 7, and the first hole 13 is a flared hole having an R-shaped inner surface in cross section and smoothly continuous with the second hole 14 and extending upward. In this way, when the first hole 13 opened in the front surface 8 of the mask body 7 is formed by a bell-mouthed hole, the printing paste at the time of filling the through-hole 10 can be guided to the inner surface of the hole of the first hole 13 having the R-shaped cross-sectional shape, and therefore the printing paste 4 can be introduced into the through-hole 10. Further, when the second holes 14 connected to the first holes 13 are formed linearly, smoothly continue to the first holes 13, and are opened to the back surface 9 of the mask body 7, the printing paste 4 can be guided to the hole inner surfaces of the first holes 13, reach the vicinity of the boundary portion between the two holes 13 and 14, be guided into the second holes 14, and be filled therein, and the printing paste 4 can reach the back surface 9 side of the mask body 7 of the second holes 14. As described above, according to the metal mask for printing of the present embodiment, the printing paste 4 guided by the first hole 13 is collected near the boundary portion between the two holes 13 and 14 and can be guided into the hole of the second hole 14, and therefore, even if the printing paste 4 comes into contact with the inner surface of the through hole 10, the printing paste can be guided to the printing object 2. As described above, according to the metal mask for printing of the present embodiment, since the occurrence of printing defects such as deformation of the printing shape of the printing layer on the printing object 2 and printing blur can be suppressed, it is possible to improve the printing accuracy in printing the printing layer and to form a high-accuracy and high-quality printing layer on the printing object 2.

In the printing metal mask of the present invention, the overcoat layer 17 may be formed on the back surface (circuit board facing surface 9) of the mask body 7. When the coating layer 17 is formed on the hole inner surface of the through hole 10, it is only necessary to form the coating layer on the hole inner surface of the second hole 14. This is because, if the coat layer 17 is formed on the surface (blade surface) 8 of the mask body 7 or the inner surface of the hole of the first hole 13, the printing paste 4 does not roll when the printing paste 4 is squeegeed by the blade S, and there is a possibility that good printing (guiding and filling into the through hole 10) cannot be performed. When the coating layer 17 is formed on the back surface 9 of the mask body 7 and the inner surface of the hole of the second hole 14, the thickness of the coating layer 17 on the back surface 9 of the mask body 7 may be equal to or greater than the thickness of the coating layer 17 on the inner surface of the hole of the second hole 14. In the metal mask for printing according to the first embodiment, the opening dimension (opening diameter) D1 of the first hole 13 is formed smaller than the length dimension (diameter) D4 of the electrode 3, and the opening dimension (opening diameter) D2 of the second hole 14 is formed larger than the length dimension (diameter) D4 of the electrode 3, and the shape of the printed layer printed on the printed object 2 with such a configuration is formed into a columnar body having the same dimension as the opening dimension (opening diameter) D1 of the first hole 13 from the upper surface side to the lower surface side, or a cross-sectional mountain shape having the same dimension as the opening dimension (opening diameter) D1 of the first hole 13 on the upper surface side and having a dimension that increases toward the lower surface side (printed object 2 side). On the other hand, in the metal mask for printing in the present embodiment, the opening dimension (opening diameter) D1 of the first hole 13 is formed to be larger than the length dimension (diameter) D4 of the electrode 3, and the opening dimension (opening diameter) D2 of the second hole 14 is formed to be smaller than the length dimension (diameter) D4 of the electrode 3, and the print layer printed on the printing object 2 with such a configuration is formed into a columnar body having the same size as the opening dimension (opening diameter) D2 of the second hole 14 from the upper surface side to the lower surface side, with the through hole 10 filled with the printing paste 4. In this way, in the metal mask for printing of the present embodiment, since the second hole 14 opened in the back surface 9 of the mask is formed linearly, even if the through hole 10 is filled with the printing paste 4 and the printing paste 4 is in contact with the entire inner surface of the through hole 10, the printing paste 4 located in the inner surface of the second hole 14 can be printed on the printing object 2 when the metal mask for printing is separated from the printing object 2, and the amount of the printing paste 4 adhering to the inner surface of the through hole 10 and removed from the printing object 2 can be reduced as compared with a metal mask in which the inner surface of the through hole has an R-shaped cross section. Therefore, according to the metal mask for printing of the present embodiment, the printed layer having a uniform thickness and high reproducibility on the printing object 2 can be printed and formed.

In the above-described embodiment, the cross-sectional shape of the inner surface of the second hole portion 14 is formed in a quarter elliptical arc shape having a short axis in the thickness direction of the mask main body 7, but may be formed in a quarter elliptical arc shape or an arc shape having a long axis in the thickness direction of the mask main body 7. In short, the cross-sectional shape of the inner surface of the second hole portion 14 may be an R shape bulging toward the hole center side. For example, the cross-sectional shape of the inner surface of the second hole 14 may be an R-shape in which the curvature changes between the first hole 13 and the back surface 9 of the mask body 7, such as an R-shape in which the curvature near the first hole 13 and the back surface 9 of the mask body 7 are large and the curvature at the intermediate portion is small. In the above-described embodiment, the printing is performed by the contact printing in which the printing metal mask 1 is directly placed on the printing object 2, but the printing may be performed by the non-contact printing in which a gap is provided between the printing object 2 and the printing metal mask 1. The technique of the present invention is not limited to the metal mask for printing, and can be transferred to a metal mask such as a vapor deposition mask, a solder ball alignment mask, or a solder ball adsorption mask.

Claims (8)

1. A metal mask for printing is characterized in that,

the disclosed device is provided with:

a mask body (7) which is made of a thin metal plate and has a back surface (9) facing the printing object (2); and

a plurality of through holes (10) which penetrate the mask body (7) on the front and back sides and are filled with the printing paste (4),

the through-hole (10) includes: a first hole (13) that is open on the surface (8) of the mask body (7) and is formed from a linear hole; and a second hole (14) having an inner surface formed in an R-shape in cross section, smoothly continuing to the first hole (13), and opening on the back surface (9) of the mask body (7).

2. The printing metal mask according to claim 1,

the first hole (13) is formed by a straight circular hole, and the second hole (14) is formed by a flared hole.

3. The printing metal mask according to claim 1 or 2,

when the thickness T of the mask body (7) is set to 1, H1 defined by the hole depth of the first hole (13) is set to 0.2 to 0.6.

4. The printing metal mask according to claim 1 or 2,

when the thickness T of the mask body (7) is set to 1, H1 defined by the hole depth of the first hole (13) is set to 0.2 or more and less than 0.5.

5. The printing metal mask according to claim 1 or 2,

when the hole depth of the second hole (14) is defined as H2 and half of the enlarged size of the second hole (14) is defined as D3, the second hole (14) is formed so as to satisfy the inequality H2 < D3.

6. The printing metal mask according to claim 1 or 2,

when the opening size of the first hole (13) in the front surface (8) of the mask body (7) is defined as D1 and the opening size of the second hole (14) in the back surface (9) of the mask body (7) is defined as D2, the opening size D2 is set to be 1.5 times or more the opening size D1.

7. The printing metal mask according to claim 1 or 2,

the thickness T of the mask body (7) is set to be 25 [ mu ] m or less.

8. The printing metal mask according to claim 1 or 2,

a coating layer (17) for suppressing adhesion of the printing paste (4) is formed on the inner surface of the through hole (10) and the back surface (9) of the mask body (7),

when the layer thickness of the coating layer (17) in the first hole (13) is defined as C1, the layer thickness of the coating layer (17) in the second hole (14) is defined as C2, and the layer thickness of the coating layer (17) in the back surface (9) of the mask body (7) is defined as C3, the coating layer (17) is formed so as to satisfy the inequality C1 ≦ C2 ≦ C3.

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