JPH03227241A - Screen printing method and printing attachment - Google Patents

Abstract

PURPOSE:To improve printing precision and life of a metallic mask by a method wherein a screen printing metal mask supported via an elastic support member is arranged opposed to a printing substrate inside a frame like attachment, and a printing agent is applied to the printing substrate therethrough. CONSTITUTION:A metallic mask frame 60 made by a square frame is, in an on/off free manner, fitted to a center inside an attachment 6 composed of metal lic materials of Al or the like via elastic support member 61 by using screws 62. A metal mask 63 for screen printing of a wiring pattern on a substrate 1 is fixed to its lower surface. At first an arranging position of the attachment 6 is established at a position where a surface sticks fast to the lower surface to the metal mask 63 when a thinnest substrate 1 is set. In that case, though a thick substrate 1 is set, the elastic support member 61 absorbs pushing up force, and deformation of the metal mask 63 does not occur. Then, when the substrate 1 is set, a solder applied layer is formed on a wiring pattern forming part of the substrate 1 by using solder paste applied preliminarily on an upper surface side of the metal mask 63.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a screen printing method used, for example, in the manufacture of hybrid ICs, and a printing attachment used to carry out the method.

Conventional ``Limit'' Hybrid ICs are manufactured by soldering chip components by reflow soldering or flow soldering to wiring patterns formed on one or both sides of a board by screen printing.

Among these methods, when using reflow soldering, a screen printing mask with holes corresponding to predetermined positions of the wiring pattern is placed facing the board surface, and the solder paste is spread using a printing means such as a hard rubber squeegee. Solder paste is applied only to the wiring pattern portion corresponding to the hole forming position of the mask, and then the solder is melted to solder the desired chip component placed at this position.

One conventional example of a mask used in such a solder application process is a gauze mask made of cloth material such as silk formed into a mesoche shape. The screen printing method using this gauze mask is carried out as shown in FIG.

That is, the substrate 1 is placed with a predetermined gap G provided below the gauze mask 2, which is placed at a predetermined position and whose upper surface is coated with the solder paste 3. From this state, squeegee 4
spread the solder paste 3 laterally. At this time, the gauze mask 2 is bent downward by the pressing force of the squeegee 4 as shown by the dashed line in the figure, and comes into contact with the surface of the substrate 1. Therefore, according to this method, the solder paste 3 that has penetrated through the mesh is applied to the wiring pattern forming portion of the substrate 1.

Further, as another conventional example of a mask, there is one called a metal mask. This metal mask has a thickness of 0.2f
It is made of a metal plate with a thickness of about 1 to 0.3 fins, and holes are formed by etching or the like at locations corresponding to predetermined positions of the wiring pattern on the substrate 1.

The solder application process using a metal mask is performed using the same squeegee 4 as described above with the metal mask in close contact with the surface of the substrate 1.

However, when using the gauze mask 2, when the solder paste 3 is spread, the gauze mask 2, which is pressed against the surface of the board 1, is applied to the wiring pattern when it lifts up from the surface of the board 1. Since a part of the solder paste 3 is lifted up, there is a drawback that it becomes difficult to accurately apply the solder paste 3 to the wiring pattern. That is, when the gauze mask 2 separates from the surface of the substrate 1, a portion of the solder paste 3 that has been attached is peeled off from the wiring pattern, resulting in the above-mentioned drawback.

On the other hand, when using a metal mask, although it does not have the disadvantages of the gauze mask 2 described above, in order to accurately perform the solder application process using a metal mask, it is necessary to keep the metal mask in close contact with the surface of the substrate 1 at all times. However, it is difficult to maintain close contact all the time due to variations in the thickness of the substrate 1 and problems with the accuracy of the printing machine as a whole. Therefore, there is a limit to how accurately the solder coating process can be performed.

In addition, when using a metal mask, due to variations in the thickness of the substrate 1, if the substrate 1 pushes the metal mask upward, the metal mask itself has no elasticity.
This also has the disadvantage that it may be forcibly deformed, which may impair its lifespan.

Therefore, in order to eliminate the drawbacks of the gauze mask 2 and the metal mask, a mask called a combination mask may be used. As shown in FIG. 5, this combination mask is made up of a small metal mask 5 and a gauze stretched part 50 made of a cloth material connected around it.The gauze stretched part 50 imparts elasticity to the metal mask 5, and this The metal mask 5 is always kept in close contact with the surface of the substrate 1 by absorbing variations in the thickness of the substrate 1 and variations in accuracy of the printing machine as a whole.

Therefore, according to such a combination mask, a part of the solder paste 3 that has been applied will not be peeled off and the application accuracy will not be impaired, the metal mask 5 can be kept in close contact with the surface of the substrate 1 at all times, and the metal Since the mask is not forcibly deformed, there is no drawback that the life of the metal mask 5 is impaired.

However, when using a combination mask,
There are new drawbacks as shown below.

(2) Manufacturability is poor because a technique is required to reliably connect the gauze section 50 and the metal mask 5.

(2) Since the size and hole shape of the metal mask 5 are selected depending on the substrate 1, a large number of combination masks must be manufactured depending on the type of the substrate 1, leading to an increase in cost.

(2) Although the lifespan of the metal mask 5 is not unnecessarily impaired, since the lifespan of the gauze section 50 is short, the lifespan of the metal mask 5 as a whole is shortened.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide a screen printing method that can eliminate the various drawbacks of the prior art described above, and a printing attachment used for carrying out the method.

In the screen printing method according to the present invention, a metal mask for screen printing supported inside a frame-shaped attachment via an elastic support member is disposed opposite to a printing substrate, and The present invention is characterized in that the printing agent is applied to the printing substrate through a metal mask.

Further, the printing attachment according to the present invention includes a frame-shaped attachment body surrounding a metal mask for screen printing that is arranged opposite to a printing substrate, and a frame-shaped attachment body that is provided inside the attachment body, and that has a tip that It is characterized by comprising an elastic support member that supports the peripheral edge of the metal mask.

If a metal mask is elastically supported by an elastic support member as described above, if the metal mask is placed in close contact with the substrate without a gap, the thickness of the substrate Even if the substrate comes into contact with the metal mask in such a way as to push it up due to variations in the metal mask, the elastic support member absorbs this pushing up force.

Therefore, no pushing-up force that would cause unreasonable deformation of the metal mask is applied.

In addition, since the elastic support member imparts elasticity to the metal mask, for example, a predetermined gap is provided between the metal mask and the substrate, and from this state, the metal mask is pressed with a printing means such as a squeegee. If so, the metal mask will be in close contact with the substrate.

Fruit = 1L Two squares An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing a mask used for implementing the screen printing method according to the present invention, and FIG. 2 is a side sectional view showing the state in which the method of the present invention is implemented.

This mask has an attachment 6 consisting of a rectangular frame.
It is used while being held inside.

That is, in the center of the interior of the attachment 6 made of a metal material such as Aβ, there is a metal mask frame 60 made of a rectangular frame.
can be installed. A metal mask 63 having holes corresponding to predetermined positions of the wiring pattern formed on the substrate 1 is assembled to the lower surface of the mask frame 60, as shown in FIG.

Attaching the mask frame 60 to the attachment 6 is as follows:
This is done via an elastic support member 61 made of a leaf spring or the like.

That is, as shown in FIG. 1, the tips of U-shaped elastic support members 61, 610, both sides 61a, etc. are located at the longitudinal intermediate portions of the left and right peripheral edges 6L and 6R of the attachment 6 in the drawing. , for example, by welding or the like. The left and right peripheral edges 60L and 60R of the mask frame 60 are detachably attached to the connecting portions 61b and 61b of the elastic support members 61 and 61, respectively.

This attachment is performed by screws 62, 62, 62, and 62 fastened to both front and rear ends of the peripheral portions 60L and 60R in the drawing. As shown in FIG. 2, the intermediate portions of both sides 61a, 61a of the elastic support member 61.61 are bent, so that the connecting portions 61b, 61b are positioned upward.

Screen printing using such a metal mask 63 is performed in the second stage.
This is done as shown in the figure. First, the installation position of the attachment 6 is set so that the metal mask 63 attached to the lower surface side of the mask frame 60 is always in close contact with the surface of the substrate work set below it. Specifically, when the substrate 1 with the thinnest thickness is set, the surface thereof is set in a position where it comes into close contact with the lower surface of the metal mask 63.

In such a case, when a thick substrate 1 is set, it pushes the metal mask 63 upward, but since the metal mask 63 is elastically supported by the cantilevered elastic support member 61 via the mask frame 60, The elastic support member 61 absorbs the pushing force at this time. Therefore, no deformation occurs in the metal mask 63 that would impair its lifespan.

Then, when the substrate 1 is set on the lower surface of the metal mask 63, a solder coating layer is formed on the corresponding wiring pattern forming portion of the substrate 1 using the solder paste applied in advance to the upper surface side of the metal mask 63.

Thereafter, desired chip components are attached to this solder coating layer.

As mentioned above, when attaching the mask frame 60 to the attachment 6 removably using the floss 2...
It becomes possible to assemble metal masks 63 having hole shapes corresponding to various wiring patterns to one attachment 6. Therefore, it is particularly effective when performing screen printing for high-mix, low-volume production.

In addition, instead of screwing, a convex part is formed on either the elastic support member 61 or the mask frame 60, and this is fitted into a concave part formed on the other, so that the two can be attached and detached. Good too. Alternatively, both may be fixed.

Furthermore, in the illustrated example, both sides 61a of the elastic support member 61,
61a are welded to the peripheral edges 60L, 60R of the attachment 6, but the attachment 6 itself is made of a highly elastic material, and the elastic support member 61 is integrally extended from the peripheral edges 60L, 60R. You can also do that.

In addition, the elastic support member 61 may be made of hard rubber or the like instead of a leaf spring.
You may also decide to form. Furthermore, the elastic support member 6
1 is not limited to the U-shaped one, but the both sides 61a161
a may be independent.

FIG. 3 shows another implementation state of the method of the present invention. In this embodiment, an appropriate gap G is provided from the beginning between the metal mask 63 and the substrate l, and the upper surface of the metal mask 63 is coated in advance. A method is used in which screen printing is performed by spreading the solder paste with a squeegee 4. Also in this method, since the elastic support members 61, 61 absorb the pressing force of the squeegee 4, deformation that would impair the life of the metal mask 63 does not occur.

In the above embodiments, the method of the present invention and the printing attachment used in its implementation are applied to the solder coating process, but it goes without saying that the method can also be applied to other types of screen printing.

According to the screen printing method according to claim 1, by deforming the elastic support member, the metal mask can be easily brought into close contact with the substrate at 4° without putting any burden on it. , printing accuracy can be significantly improved compared to conventional screen printing methods using metal masks. Moreover, the lifespan of the metal mask can be improved.

Moreover, especially according to the printing attachment according to claim 2, since the metal mask and the attachment can be easily connected, it is possible to improve the productivity compared to the case of using a conventional combination mask, and to reduce costs. It becomes convenient.

In addition, since there is no member with a short lifespan such as a gauze part, there is an advantage that the overall lifespan can be significantly improved compared to a combination mask.

[Brief explanation of drawings]

Fig. 1 is a plan view showing a mask used in carrying out the screen printing method according to the present invention, Fig. 2 is a side cross-sectional view showing a state in which the method of the present invention is carried out, and Fig. 3 is another state in which the method of the present invention is carried out. FIG. FIG. 4 is a drawing showing a solder application process using a conventionally known gauze mask, and FIG. 5 is a plan view showing a conventionally known combination mask. DESCRIPTION OF SYMBOLS 1... Substrate, 6... Attachment, O... Mask frame, ■... Elastic support member.

Claims (2)

[Claims] (1) A metal mask for screen printing supported through an elastic support member inside a frame-shaped attachment is arranged opposite to the printing substrate, and a printing agent is applied to the printing substrate through the metal mask. A screen printing method characterized by coating. (2) A printing attachment that supports a metal mask for screen printing that is placed opposite to a printing board, comprising: a frame-shaped attachment body that surrounds the metal mask; and a frame-shaped attachment body that is provided inside the attachment body. and an elastic support member that supports the peripheral edge of the metal mask at its tip.