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JP-7857473-B2 - Metal mask for printing

JP7857473B2JP 7857473 B2JP7857473 B2JP 7857473B2JP-7857473-B2

Inventors

  • 中島 貴士
  • 堀之内 強
  • 高嶋 健一

Assignees

  • マクセル株式会社

Dates

Publication Date
20260512
Application Date
20250421

Claims (7)

  1. The mask body (7) is made of a thin metal plate and its back surface (9) faces the object to be printed (2), The mask body (7) is provided with numerous through-holes (10) that penetrate from front to back and are filled with printing paste (4), The through-hole (10) consists of a first hole (13) which is a straight, circular hole with a uniform inner radius that opens in a perfect circle on the surface (8) of the mask body (7), and a second hole (14) which is bell-mouth shaped , with an R-shaped inner cross-section, smoothly continuous with the first hole (13), and expanding as it opens in a perfect circle on the back surface (9) of the mask body (7) . The cross-sectional shape of the inner surface of the bell-mouth-shaped second hole (14) is configured such that the radius of curvature is small at the upper end portion continuous with the first hole (13), and increases as it goes downwards. A printing metal mask characterized in that, at the upper end of the second hole (14), the tangent to the upper end of the arc formed by the radius of curvature defining the cross-sectional shape of the inner surface of the upper end coincides with the straight line defining the cross-sectional shape of the inner surface of the straight first hole (13) .
  2. The printing metal mask according to claim 1 , wherein, when the thickness (T) of the mask body (7) is 1, the (H1) defined by the hole depth of the first hole portion (13) is set to 0.2 or more and 0.6 or less .
  3. The printing metal mask according to claim 1 , wherein when the thickness (T) of the mask body (7) is 1, the (H1) defined by the hole depth of the first hole portion (13) is set to 0.2 or more and less than 0.5 .
  4. A printing metal mask according to any one of claims 1 to 3, wherein the hole depth of the second hole (14) is defined as (H2) and half of the enlarged dimension of the second hole (14) is defined as (D3), and the second hole ( 14 ) is formed such that the inequality (H2 < D3) is satisfied.
  5. A printing metal mask according to any one of claims 1 to 4, wherein when the opening dimension of the first hole (13) on the surface (8) of the mask body (7) is defined as (D1) and the opening dimension of the second hole (14) on the back surface (9) of the mask body (7) is defined as (D2), the opening dimension (D2) is set to be 1.5 times or more the opening dimension (D1) .
  6. A printing metal mask according to any one of claims 1 to 5 , wherein the thickness (T) of the mask body (7) is set to 25 μm or less .
  7. A coating layer (17) is formed on the inner surface of the through-hole (10) and on the back surface (9) of the mask body (7) to suppress the adhesion of the printing paste (4). A printing metal mask according to any one of claims 1 to 6, wherein the coating layer (17) is formed such that the inequality (C1 ≤ C2 ≤ C3) is satisfied when the thickness of the coating layer (17) in the first hole (13) is defined as (C1), the thickness of the coating layer (17) in the second hole (14) is defined as (C2), and the thickness of the coating layer (17) on the back surface (9) of the mask body (7) is defined as (C3).

Description

This invention relates to a technique for improving printing defects such as bleeding and smudging of the printed layer in a printing metal mask. An example of a printing metal mask according to this invention is one used when printing a layer of flux (printing paste) for temporarily adhering solder balls to a substrate using a screen printing method. As a technology to improve the printing accuracy of metal masks for printing, the applicant previously proposed Patent Document 1. In Patent Document 1, the cross-sectional shape of the through-holes formed in a metal mask manufactured by electroforming is tapered, with a smaller hole diameter on the electroformed surface side and a larger hole diameter on the electroformed mold surface side. During printing, the electroformed surface side becomes the surface side, i.e., the squeegee side, and the electroformed mold surface side becomes the back side, i.e., the substrate (printing target) side. When forming the ink/paste (printing paste) layer (printing layer), first, the substrate side of the metal mask is brought into close contact with the substrate. Then, ink/paste is placed on the squeegee surface of the metal mask, and the ink/paste on the squeegee surface is spread with the squeegee to fill the inside of the through-holes. After the filling of the through-holes with ink/paste is complete, the metal mask is separated from the substrate, thereby printing and forming the ink/paste printing layer corresponding to the through-holes on the substrate. Japanese Patent Application Publication No. 10-305670 This is a longitudinal cross-sectional front view showing the main parts of a printing metal mask according to the first embodiment of the present invention.This is a plan view showing the entire metal mask for printing.This is a longitudinal cross-sectional side view showing an example of how a metal mask for printing is used.This is an explanatory diagram showing the manufacturing process of metal masks for printing.The main parts of a printing metal mask according to a second embodiment of the present invention are shown, with (a) being a longitudinal cross-sectional front view and (b) being a bottom view. (First Embodiment) Figures 1 to 4 show a first embodiment of the printing metal mask according to the present invention. Note that the dimensions such as thickness and width in each figure are schematic representations and not actual representations. The printing metal mask (hereinafter simply referred to as "mask") 1 is used to print a printing layer consisting of flux (printing paste) 4 for temporarily adhering solder balls onto electrodes 3 formed on the surface of a circuit board (printing target) 2 using a screen printing method, as shown in Figure 3. In Figure 2, the mask 1 is based on a mask body 7 made of a thin metal sheet formed by electroforming using an electrodeposited metal such as nickel, copper, or nickel-cobalt alloys. The mask body 7 has numerous through-holes 10, which are circular holes penetrating from the front surface 8 to the back surface 9. The mask 1 is formed in a square shape with sides of 250 mm. When the mask 1 is divided into four quadrants, a pattern formation region M is demarcated in each quadrant. The through-holes 10 are provided within the pattern formation region M, positioned to correspond to the electrode patterns of the circuit board 2's electrodes 3. Around the pattern formation region M, a cut mark formation region C is demarcated, enclosing the region M, for printing cut marks used when cutting the circuit board 2 into a specified shape in a post-screen printing process. The mask 1 is mounted on the mask fixing part of the screen printing apparatus, either alone or with a frame fixed to its four periphery. As shown in Figure 1, the through-hole 10 consists of a first hole 13 opening on the surface 8 of the mask body 7 and a second hole 14 opening on the back surface 9 of the mask body 7. The first hole 13 is a straight, round hole extending in the thickness direction of the mask body 7, while the second hole 14 is a bell-mouth-shaped hole that smoothly continues from the first hole 13 and expands downwards. The thickness T of the mask body 7 is preferably 25 μm or less, and more preferably 18 μm or less. In this embodiment, the thickness T of the mask body 7 is set to 18 μm. The hole depth H1 of the first hole 13 (see Figure 1) is set to be 0.2 or greater and less than 0.5 when the thickness T of the mask body 7 is 1. In this embodiment, the hole depth H1 is set to 3.6 μm, and the hole depth H1 when the thickness T of the mask body 7 is 1 is 0.2 (3.6/18 = 0.2). The opening dimension of the first hole 13, i.e., the opening diameter (diameter) D1 (see Figure 1), is set to be the same as the diameter of the flux 4 layer to be formed on the electrode 3. The diameter of a typical flux 4 layer is set to 20 μm to 50 μm; therefore, in this embodiment, the opening diameter D1 is set to 40 μm. The opening diameter D1 of t