JP2017170716A - Mask for paste embed-printing and printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve, when embed-printing a paste in a hole part formed in a dry film, the yield by leaving the paste as little as possible on the surface other than the hole part.SOLUTION: Provided is a mask 25 having an opening for exposing a plurality of hole parts on the surface of a dry film and to be overlaid on the surface of the dry film for embed-printing a paste in the hole parts, and in which there are formed an outer peripheral frame 23, and an annular thin wall 24 formed thinner than the outer peripheral frame 23 on the inner peripheral part of the outer peripheral frame 23 and an opening 22 is formed by the inner peripheral edge of the thin wall 24.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a paste embedding printing mask and a printing apparatus for printing in a state in which a paste is embedded in a plurality of holes on the surface of a substrate.

A circuit board on which electronic components are surface-mounted is provided with solder bumps on the surface electrodes. As a method of forming this solder bump, a dry film (photosensitive resin layer) is formed on the circuit layer formed on the surface of the insulating substrate, and the hole that leads to each electrode of the circuit layer is formed by exposing the dry film. Each of these holes is formed, a solder paste is embedded in these holes, and the solder paste on each electrode is reflowed.
In this case, the solder paste is embedded in the hole of the dry film by screen printing.

In this screen printing, a single opening is formed in the mask so as to expose a plurality of openings in the dry film, the mask is overlaid on the dry film, and a squeegee is placed on the mask. The solder paste is applied onto the dry film in the opening while moving.
As a method for printing a conductive paste such as a solder paste on a circuit board using such a mask, there are techniques described in Patent Document 1 and Patent Document 2, for example.
In Patent Document 1, as a metal mask for printing a solder paste, in a hole serving as a printing material filling portion of a metal mask, an opening area of a printing side opening is formed smaller than an application side opening of the hole. Has been disclosed.
Patent Document 2 also discloses a mask having a hole formed in a tapered shape so that the opening on the application side is larger.

JP 2006-187955 A Special table 2010-541208

By the way, when the solder paste is embedded and printed in the hole portion of the dry film described above, the mask portion is formed in a size that can surround the whole hole formation region of the dry film, so the inner peripheral edge of the opening portion. There is a problem that the solder paste tends to accumulate in the corner formed between the upper surface of the dry film and the dry film, and the solder paste remains on the dry film, resulting in poor yield of the solder paste.
In this case, as described in Patent Document 1 and Patent Document 2, it is considered that forming the inner peripheral edge of the opening in a tapered shape can reduce the remaining amount of solder paste, but the effect is slight. Only it is.

  The present invention has been made in view of such circumstances, and when the paste is embedded and printed in the hole formed on the substrate surface by the hole or the like of the dry film, the paste is left as much as possible on the surface other than the hole. The purpose is to improve the yield of paste.

In order to solve the problem, the present invention proposes a paste embedding printing mask and a printing apparatus.
The mask for paste embedding printing of the present invention has an opening for exposing a plurality of holes of a dry film on a substrate surface, and is a mask for embedding and printing a paste in the hole overlaid on the surface of the dry film. And an outer peripheral frame part and an annular thin part formed thinner than the outer peripheral frame part on the inner peripheral part of the outer peripheral frame part, and the opening is formed by the inner peripheral edge of the thin part. Has been.

In a conventional mask in which an opening is simply formed inside the outer peripheral frame, the squeegee is moved while supporting both ends of the squeegee arranged over the opening on the outer peripheral frame. When the paste is applied so as to be pushed into the opening, the paste remains without being scraped off by the height of the inner peripheral edge of the opening.
On the other hand, in the mask of the present invention, both ends of the squeegee arranged so as to straddle the opening can be moved in a state where the squeegee is supported on the thin part. It is possible to reduce the amount of paste remaining on the surface.
On the other hand, since the outer peripheral frame portion is thicker than the thin-walled portion, the thick outer peripheral frame portion can ensure the overall rigidity and suppress the occurrence of deformation and elongation.

  In the mask of the present invention, the thin portion may be formed so that the thickness gradually decreases from the outer peripheral frame portion side toward the opening portion side.

  Although the remaining amount of paste can be reduced by making the inner peripheral edge of the thin part as thin as possible, the strength as a mask is impaired to make the whole thin part thin. Therefore, by making the inner peripheral edge of the thin-walled portion the thinnest and gradually increasing the thickness toward the outside, the remaining amount of paste can be further reduced while ensuring the rigidity as a whole. In this case, since the squeegee is made of a rubber material and has elasticity, even when both ends are supported by the thick part of the thin part, the squeegee is pressed against the mask to reduce the thickness of the thin part. The surface can also be slid, and the remaining paste on the thin portion can be prevented.

  The paste embedding printing apparatus of the present invention includes the paste embedding printing mask, and a squeegee for applying the paste to the dry film surface through the embedding printing mask, the squeegee from the outer peripheral frame portion. Also, it is formed in such a length that both ends are supported by the thin portion across the opening.

  According to the present invention, embedding printing can be performed without leaving the paste as much as possible on the surface other than the hole portion of the dry film, and the yield of the paste can be improved.

It is sectional drawing which shows the mask apparatus in one Embodiment of the embedding printing apparatus of this invention. It is sectional drawing of the principal part of the embedding printing apparatus of one Embodiment. It is sectional drawing of the edge part of the mask for printing in one Embodiment. It is sectional drawing of the edge part of the mask for printing in 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described.
The substrate that is embedded and printed by the printing apparatus of the embodiment will be described. This substrate 1 is a printed circuit board, and as shown in FIG. 2, on the insulating substrate 2 made of an insulating material such as an epoxy resin, A circuit pattern 3 made of a good electrical conductor such as copper is formed. A dry film 4 made of an acrylic photosensitive material or the like is laminated on the circuit pattern 3, and holes for exposing the electrode portions of the circuit pattern 3 are formed in the dry film 4.

The printing apparatus of this embodiment is an apparatus that embeds and prints a solder paste as a paste in each hole 5 of the dry film 4. As the solder paste, a solder paste containing a Sn-based alloy such as a Sn—Cu alloy, a Sn—Ag alloy, or a Pb—Sn alloy is suitable.
The printing apparatus 11 includes a mask device 21 that is overlaid on the dry film 4 on the surface of the printed circuit board 1, and a squeegee head 31 that moves on the mask device 21 and applies paste. 21 is formed with an opening 22 having a size that exposes the entire area (hole forming area) in which the plurality of holes 5 of the dry film 4 are formed. The opening 22 is formed by one squeezing operation. A paste is embedded and printed in each exposed hole 5.

As shown in FIG. 1, the mask device 21 includes a rectangular frame 23, a screen ridge 24 attached to the inside of the frame 23, and a printing mask stretched on the inside of the screen ridge 24 (the present invention). ) Mask 25).
The frame 23 is made of a metal such as stainless steel or aluminum and has a strength capable of maintaining the shape of the mask device 21 as a whole. The printing mask 25 is a stencil mask made of metal such as stainless steel or nickel, and is formed in a thin flat plate shape. The screen cage 24 is a mesh-like thing having stretchability stretched between the inner periphery of the frame 23 and the outer periphery of the printing mask 25, and is formed of a resin such as polyester or a metal such as stainless steel, The printing mask 25 is held in a flat plate shape inside the frame 23.

  The printing mask 25 is integrally formed with a thick outer peripheral frame portion 26 and an annular thin portion 27 formed thinner on the inner peripheral portion of the outer peripheral frame portion 26 than the outer peripheral frame portion 26. An opening 22 is formed by the inner peripheral edge of the thin portion 27. When the length L2 of one side of the opening 22 of the printing mask 25 is 50 mm to 450 mm, as shown in FIGS. 1 and 3, the thickness H of the outer peripheral frame 26 is 0.05 mm to 2 mm. The thin portion 27 has a height (thickness) h of 0.01 mm to 0.03 mm, and its length (distance from the inner periphery of the outer peripheral frame portion 26 to the inner periphery of the thin portion 27) L is 5 mm to 10 mm. Formed. For example, when the length L2 of one side of the opening portion 22 of the printing mask 25 is 240 mm, the height H of the outer peripheral frame portion 26 is 1 mm, the height h of the thin portion 27 is 0.02 mm, and the length of the thin portion 27. L is formed to 5 mm.

  In the printing mask 25, the squeegee 34 is arranged so as to cross over the opening 22, and both ends of the squeegee 34 slide on the thin portion 27. Therefore, the length L3 of the squeegee 34 is larger than the width L2 of the opening 22 along the direction orthogonal to the sliding direction (squeezing direction), as shown in FIG. Is set to be smaller than the width L1 (the distance between the inner peripheral edges of the outer peripheral frame portion 26 in the direction orthogonal to the squeezing direction) L1. For example, when the width L1 between the step portions 28 between the peripheral frame portion 26 and the thin portion 27 is 240 mm, the length L3 of the squeegee 34 is smaller than L1 and is formed to be 235 mm to 238 mm.

A method for embedding and printing a paste in the hole 5 of the dry film 4 using the printing apparatus 11 configured as described above will be described.
The mask device 21 is stacked on the dry film 4 on the surface of the printed circuit board 1, and the entire hole forming region of the dry film 4 is exposed to the opening 22 of the printing mask 25. Then, the squeegee 34 of the squeegee head 31 is brought into contact with the thin portion 27 in front of the opening portion 22 of the printing mask 25 in the squeegeeing direction, and the printing mask 25 is pressed with a predetermined pressing force.
In this state, the squeegee head 31 is moved and squeezed while the paste P is pushed out from between the squeegees 34 while a predetermined pressing force is applied to the squeegee 34. By this operation, the paste P pushed out from between the squeegees 34 is filled in the hole 5 of the dry film 4. The squeegee operation is completed by moving the squeegee head 31 to the end of the printing mask 25 and disposing the squeegee 34 on the thin portion 27 from the opening 22.

In the final stage of this squeezing operation, when the squeegee 34 rides on the periphery of the opening 22, the paste P may remain in the opening 22. Since the height h of the peripheral edge is small (for example, 0.02 mm), even if the paste P remains, the amount thereof is extremely small. Therefore, the yield of paste P can be increased by using this printing mask 25.
Further, since the overall rigidity of the printing mask 25 is maintained by the outer peripheral frame portion 26, the durability against repeated printing is also good.

FIG. 4 shows another embodiment of the printing mask in the printing apparatus of the present invention. In the printing mask 41, the thickness of the thin portion 42 inside the outer peripheral frame portion 26 is formed so that the thickness gradually decreases from the inner peripheral edge side of the outer peripheral frame portion 26 toward the opening portion 22 side. The upper surface 42 a of the thin wall portion 42 is formed in an inclined surface with a downward slope toward the opening 22.
The printing mask 41 is formed such that the thinnest inner peripheral thickness h1 of the thin portion 42 is 0.01 mm to 0.03 mm, and the inclination angle θ of the upper surface 42a of the thin portion 42 is 10 ° to 45 °. The For example, the thickness h1 of the inner peripheral edge of the thin portion 42 is 0.01 mm and the inclination angle θ of the upper surface 42a is 10 °.
In the printing mask 41 according to the second embodiment, since the thickness of the thin portion 42 is gradually reduced toward the opening portion 22, the strength of the thin portion 42 can be secured by the relatively thick outer portion. The inner peripheral edge of 42 can be formed as thin as possible, and the amount of residual paste can be further reduced as compared with that of the first embodiment as much as it is thinned.

In addition, this invention is not limited to the thing of the structure of the said embodiment, In a detailed structure, it is possible to add a various change in the range which does not deviate from the meaning of this invention.
In the above-described embodiment, the paste is printed by the cartridge type squeegee head. However, a squeegee other than the cartridge type squeegee head may be used.
Moreover, although embodiment which prints a solder paste was demonstrated, this invention is applicable not only to a solder paste but the electrically conductive paste for wiring formation, coloring ink, etc.

1 ... Printed circuit board (board)
2 ... Insulating substrate 3 ... Circuit pattern 4 ... Dry film 5 ... Hole 11 ... Printing device 21 ... Mask device,
22 ... Opening 23 ... Frame 24 ... Screen 25 ... Printing mask (mask)
26 ... outer peripheral frame portion 27 ... thin portion 28 ... step portion 31 ... squeegee head 34 ... squeegee 41 ... mask for printing (mask)
42 ... Thin part P ... Paste

Claims (3)

  A mask having an opening that exposes a plurality of holes of a dry film on a substrate surface, being superimposed on the surface of the dry film, and for embedding and printing a paste in the hole, an outer peripheral frame, and the outer periphery The paste embedding is characterized in that an annular thin part formed thinner than the outer peripheral frame part is formed on an inner peripheral part of the frame part, and the opening is formed by an inner peripheral edge of the thin part. Mask for printing.   2. The paste embedding printing mask according to claim 1, wherein the thin portion is formed so that the thickness gradually decreases from the outer peripheral frame portion side toward the opening portion side.   The paste embedded printing mask according to claim 1 or 2, and a squeegee for applying the paste to the dry film surface through the embedded printing mask, wherein the squeegee is located inside the outer peripheral frame portion. The paste embedding printing apparatus, wherein the paste embedding printing apparatus is formed to have such a length that both ends are supported by the thin portion across the opening.