JP3023454B2 - Squeegee unit for screen printing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen printing method for printing a viscous printing material on a substrate through a screen plate having a plurality of holes having a predetermined print pattern. The squeegee to perform.

[0002]

2. Description of the Related Art In a screen printing machine, a squeegee is linearly slid in contact with the upper surface of a screen plate, and the squeegee slides a viscous printing material on the screen.
Although it is indispensable as a mechanical element for forcibly introducing it into a plurality of holes of a stencil plate, for example, as described in JP-B-1-19275, a rubbery elastic body is used. A flexible material formed into a generally thick plate has been widely used in general than before.

[0003] Conventionally known flexible skis as described above.
The screen printing is performed using a printing material having a relatively low viscosity, for example, a printing ink or an adhesive having a viscosity of about 0.2 to 2.0 × 10 ⁶ cP (centipoise). If there is no need for high-precision or high-density printing, there is no particular problem.

[0004]

However, a printing paste having a high viscosity, for example, a solder paste formed by kneading an alloy powder such as lead or tin and a high-viscosity liquid flux into a creamy shape. In the case where a printing material having a viscosity of ≧ 700,000 cP is screen-printed and high-precision or high-density printing is required, the conventional screen printing is used. The use of a flexible squeegee, such as a known squeegee, causes various disadvantages as described below.

That is, for example, when a chip-shaped electronic component is mounted on a printed circuit board, a solder paste screen printing performed on the board prior to the mounting operation is first considered. First, while the viscosity of the solder paste is extremely high, the flexibility of the squeegee inevitably increases the degree of bending deformation of the squeegee during screen printing. As shown in A),
The larger the hole 17A of the screen 17, the greater the degree of deformation of the tip of the squeegee N into the hole 17A, and accordingly, as shown in FIG. There is a tendency that the depression on the upper surface of the solder paste S printed film S 'printed on the P becomes large,
The printing pressure of the flexible squeegee N on the screen 17;
That is, since the sliding contact pressure at the time when the front end portion contacts and slides on the surface of the screen 17 is relatively weak, it enters the hole 17A of the screen 17 of the solder paste S having high viscosity. The tendency is that it becomes more difficult as the hole 17A becomes smaller, and thirdly, the rubbery elastic body lacks rigidity, so that it is used to reduce the wall thickness. It is difficult to make a squeegee that is thin and has high mechanical strength.

A screen used for screen printing of solder paste is generally made of a stainless steel plate, and its thickness is made as thin as possible, holes made in the screen are made as small as possible, and By narrowing the space between adjacent holes, high-precision and high-density screen printing with a minute printing pattern becomes possible.
In order to make it truly possible, it is essential to improve the squeegee itself, in addition to those conditions.

The present invention has been made in response to such a demand, and has been made to achieve high-precision and high-density screen printing.
In particular, it is a main object of the present invention to provide a new squeegee unit for a screen printing machine which can contribute to realization of high precision and high density of mounting chip-shaped electronic components on a printed circuit board. is there.

[0008]

In order to achieve the above object, a squeegee unit for a screen printing machine according to the present invention is provided with a recess having an opposing pressing surface inside.
A holding frame is formed by a pair of holding plates, and a single thin squeegee blade having both rigidity and elasticity is provided between the opposing pressing surfaces, and a tip portion is slightly attached to both surfaces of the squeegee blade. in a manner that was suspended protrude, each collectively with each one or a plurality of elastic plates were additionally provided with pinched, to tightening them, the holding plate by a fastening member with bolt and nut or threaded
Thereby, the structure is such that the pressure is integrally held by the opposed pressing surface .

The thickness of the squeegee blade is 0.5 mm.
The following is desirable, and when a thin strip-shaped steel sheet having high rigidity and elasticity such as a spring steel is used, 0.1 is preferable.
mm or less.

The tip of the squeegee blade has a substantially circular cross section.
It is desirable to form it in an arc shape.

In a configuration in which a plurality of elastic plates are respectively attached to both surfaces of the squeegee blade, the number of the elastic plates is the same, and the respective elastic plates are superposed stepwise in the form of a leaf spring. It is desirable to match them.

[0012]

[ Function] A thin plate having both rigidity and elasticity, for example, a thin steel plate
The squeegee blade manufactured by the above-mentioned squeegee blade has a lower bending load than the above-mentioned conventional soft squeegee .
Una a strong deformation resistance force against the load, bending deformation amount
Small Sai is, the thinner its thickness, the deformation resistance
Since the drag is weak, the amount of bending deformation increases. Therefore <br/> Te, met squeegee blade having both a rigid and an elastic
Be, for example, by using the following plate thickness thin sheet steel squeegee blades 0.5mm and fixed directly to the holder,
During screen printing, the blades are sensitive to changes in the smoothness of the screen used, the viscosity of the printing material, or changes in the composition of the printing material. It is easy to occur. If the printing material used has a high viscosity, such as a solder paste, the higher the viscosity, the more the squeegee
This tendency is exacerbated because a greater bending load acts on the tip of the blade. However, in the squeegee unit according to the present invention, a single thin squeegee blade having both rigidity and elasticity, which is a component of the squeegee unit, has an elastic plate as described above. The vibration is absorbed or mitigated by the clamping elastic plate, so that even when a high-viscosity printing material is used, the sliding state is stabilized and the bending stress acting on it is maintained. Can be dispersed, and its useful life can be extended. When the tip of the squeegee blade which is in contact with the upper surface of the screen is formed rounded, the friction coefficient during sliding is very small, not only does not damage the screen easily, The blade itself does not wear out early. Other functions will be described later in connection with the embodiment.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings showing embodiments thereof.

2 to 5, reference numerals 1 and 1 'denote a pair of holding plates, 2 denotes a squeegee blade made of one thin steel plate having a rounded tip 2', 3 denotes an elastic plate, Is a bolt, 5 is a nut, 6 and 6 are insertion holes for a plurality of bolts 4 formed in a row in the holding plates 1, 1 ', 7 is a recess for accommodating the head of the bolt 4, and 8 is a nut 5 FIG. 3 (A)
(C) to (C) show a first embodiment of the present invention, FIGS. (4A) and (4B) show a second embodiment thereof, and FIG. 5 shows a third embodiment thereof. The difference between the embodiments lies only in the number of elastic plates 2 used, the material, the shape, and the like, as will be described later, and all other points are common.

In each embodiment, a pair of holding plates 1, 1 'are used.
Inside each of the recesses 10, 1 having opposing clamping surfaces 9, 9
0 are formed, and each recess 10 is opened below and to the side of the holding plate, and is provided with a locking step 11 at the upper end. Therefore, the holding plates 1, 1
Are combined with each other to form a holding frame H having a substantially U-shaped cross section 12 for loading the squeegee blade 2 and the plurality of elastic plates 3 at a time.

In the first embodiment, FIGS.
As shown in (C), a squeegee
A blade 2 and three elastic plates 3 respectively attached to both sides thereof are collectively loaded.
The bolts 1 'are inserted into the insertion holes 6 and 6 through the bolts 6 and tightened with the nuts 5 so that the opposing pressing surfaces 9 and 9 are integrally pressed and held. In this example, each elastic plate 3
Are made of the same thin steel plate as the squeegee blade 2 and are each provided with a sled as shown in FIG. Blade 2
The inner elastic plate 3 which is in direct contact with the outermost elastic plate 3 is the longest, and the outer two elastic plates 3 are sequentially made shorter, and they are superposed like a leaf spring in a stepwise manner. On the other hand, each of the holding plates 1 and 1 'is made of a relatively hard synthetic resin having elasticity, and the lower portions 1A and 1'A are formed to have a tapered cross section, and the lower end opening of the gap 12 is narrowed. It protrudes slightly inward to make it work. Therefore, this first
In the embodiment, the squeegee blade 2 and three elastic members respectively provided on both sides of the squeegee blade are superposed stepwise in the form of a leaf spring. The plate 3 and the holding plate 9 are collectively loaded between the opposing holding surfaces 9 and 9 so that the upper ends thereof are aligned and engaged with the locking step portion 11. The squeegee blade 2 and the elastic plate are tightened by bolts and nuts 4, 5 or threaded fastening members via the holding plates 1, 1 'against the elasticity of the squeegee blade 1 and 1'. Means that the opposing pressing surfaces 9, 9 are integrally and firmly pressed and held.

In the case of the second embodiment, FIG.
As shown in FIG. 4B, the distal ends of the three elastic plates 3 are bent inward at substantially right angles, and the bent portion 14 of the longest inner elastic plate 3 has a squeegee blade. In FIG. 2, the bent portions 14 'of the other two elastic plates 3 which are sequentially shortened are respectively engaged with the elastic plates 3 adjacent to each other. FIG.
In FIG. 5A, reference numeral 15 denotes a spacer interposed between the squeegee blade 2 and the inner elastic plate 3 and between the elastic plates 3 adjacent to each other. The configuration of the other parts is the first
Since it is substantially the same as that of the embodiment, the description thereof is omitted.

In the third embodiment, a squeegee
One elastic plate 3 is provided on both sides of the blade 2 and each elastic plate 3 is made of a reinforced synthetic resin or a nylon engineering plastic having good mechanical and chemical properties. It is molded and has a relatively large thickness as shown in FIG. The configuration of the other parts is substantially the same as that of the first and second embodiments, and the description thereof will be omitted.

FIG. 6 shows an example of a screen printing machine using the squeegee unit according to the present invention. The squeegee unit according to the present invention has a holder for mounting the same. Any type of screen printing press can be used as long as it has a drive mechanism for reciprocating it in the horizontal direction and a drive mechanism for moving it up and down. The object to be used is not limited to the illustrated one. In FIG. 6, S is a solder paste, 15 is a machine frame, 16 is an air cylinder as a vertical drive mechanism of a squeegee unit, 17 is a metal screen, P is a printed circuit board, and 18 is a vertical circuit. A printing table operatively connected to the drive mechanism.

Used in the squeegee unit according to the present invention
The squeegee blade 2 is, for example, may thin carbon steel plate to be used as a thin plate spring material, to form a large becomes thin, such as elasticity and rigidity, such as alloy steel plate, its thickness,
0.5 mm or less is desirable, but as described above
Viscous printing materials such as printing inks and adhesives with relatively low viscosity
Squeegee boots for screen printing
As a raid 2, it must have great elasticity and rigidity
Not necessary. However, when a material produced from a thin plate having large elasticity and rigidity as described above is used, 1.0 /
The elastic plate 3 functions as a reinforcing material even if the thickness is as small as about 0.05 mm. Even when the printing material is a solder paste having a high viscosity, the elastic plate 3 functions as a reinforcing material. Can withstand practical use.
Such a thin squeegee blade has fine holes having an inner diameter of about 0.3 mm and a thickness of, for example, 0.1 mm.
It is suitable for high-precision and high-density screen printing of a solder paste using an extremely thin metal screen of about 5 mm to 0.2 mm.

In the squeegee unit for a screen printing press according to the present invention, an elastic plate 3 for holding the squeegee blade 2 by pressing it reinforces the blade. The blade 2 which has an adverse effect on the printing result during screen printing.
Can be effectively absorbed or mitigated by so-called friction between the plates, and the bending stress acting on the blade 2 can be dispersed by the elastic plate 3. And, as described above, the dispersion of the bending stress can extend the service life thereof. This means that the squeegee unit is mounted on the elastic plate 3
Can be easily understood by considering the operation of the squeegee blade assuming that the squeegee blade is not provided.

FIG. 7A illustrates the principle of operation of a cantilever spring C composed of a thin leaf spring having one end fixed.
In the figure, when a force W of a certain magnitude acts on the tip, which is the other end of the spring, from above, that is, the bending moment W
Acts, bending occurs as shown by a broken line, and a tensile stress is generated on its upper surface and a compressive stress is generated on its lower surface. In this case, the maximum stress occurs at the position of the fixed portion of the spring C, and if it exceeds the elastic limit of the spring C, permanent deformation occurs and the spring C cannot be used as a spring.
FIG. 7B shows a case where the cantilever spring C shown in FIG.
FIG. 5 shows a state in which the elastic plate 3 is removed from the squeegee unit for a printing press according to the present invention by rotating the squeegee unit so that the tip thereof is directed vertically downward. This is the same state as when it is assumed that only the blade is clamped and fixed to the clamping plates 1 and 1 '.

In view of this, the cantilever spring C shown in FIG. 7B is regarded as a squeegee blade 2 and the tip thereof is pressed against the upper surface of the screen at the tip thereof. Looking at the case of sliding in the direction of arrow Z in the drawing, the force received by the pressure contact and the resistance received from the viscous printing material such as solder paste when the screen is forcibly introduced into the hole of the printing material as a force W is expressed as a force W. The tip of the spring C acts in the direction opposite to the arrow Z, so that a tensile stress is generated on the right side of the spring C and a compressive stress is generated on the left side thereof. Also in this case, the generation of the maximum stress at the position of the fixed portion of the spring is almost the same as that in the case of FIG. Since the spring C cannot appropriately disperse the bending stress, the spring C is easily broken at the position of the fixing portion.

FIGS. 8A and 8B illustrate the state of the squeegee blade 2 of the squeegee unit according to the present invention in contact with the metal screen 17 and the finished state of printing. The squeegee blade 2 has both elasticity and rigidity as described above,
The hole 1 of the screen 17 at the tip of the flexible squeegee does not cause a large deformation as in the conventional squeegee.
Since the protrusion into the 7A does not occur, the hole 17A
Irrespective of the magnitude of the above, uniform and good printing can be always realized.

[0025]

Since the present invention is configured as described above, it has the following effects.

[0026] In the squeegee unit according to the present invention, the squeegee blade as the component of them together the rigidity and elasticity, and because the wall thickness is thin, using a metal screen having minute pores and is suitable for performing high-precision, high-density printing in which it, and since the blade is挾圧held by an elastic plate, towards before or after
Even if it is slid in the opposite direction , its vibration is absorbed or reduced by the pinching elastic plate, so that even when printing a high-viscosity printing material such as a solder paste, it is combined with the reinforcing function of the elastic plate. Therefore, the sliding state is stable, it is possible to effectively prevent the occurrence of printing unevenness due to fluctuations in printing pressure due to vibration, and the bending stress acting on the blade is dispersed by the elastic plate. Therefore, the useful life thereof can be extended. And also apparatus having the tip of the squeegee blade which slides in upper and培触the screen is formed in cross section generally arcuate
In addition, since the friction at the time of sliding is extremely small, not only is the screen not easily damaged, but also the blade itself is not worn out early.

Further, since the squeegee blade and the respective elastic plates are integrally held by the opposing pressing surfaces of the respective holding plates, the blades and the elastic plates may be loosened during printing. Vibration and its fall can be reliably prevented.

[Brief description of the drawings]

FIG. 1 (A) is a partially longitudinal front view showing a state of contact with a screen of a known flexible squeegee.

FIG. 1 (B) is a longitudinal sectional front view showing a finished state of printing by the squeegee shown in FIG. 1 (A).

FIG. 2 is an exploded side view showing a main part of a pair of holding plates.

FIG. 3A is a perspective view of a squeegee unit according to an embodiment of the present invention.

FIG. 3 (B) is a side view of main parts of the squeegee unit shown in FIG. 3 (A).

FIG. 3 (C) is a side view of a main part showing an assembling mode of the squeegee unit shown in FIG. 3 (A).

FIG. 4 (A) is a side view of a main part of a second embodiment of the present invention.

FIG. 4 (B) is a side view of a main part showing an assembling mode of the second embodiment shown in FIG. 4 (A).

FIG. 5 is a side view of a main part of a third embodiment of the present invention.

FIG. 6 is a schematic side view showing an example of a screen printing machine using the squeegee unit according to the present invention.

FIG. 7 (A) is a schematic side view showing the working principle of a cantilever spring.

FIG. 7 (B) is a schematic side view showing a state where the cantilever spring shown in FIG. 7 (A) is rotated by 90 °.

FIG. 8 (A) is a partial longitudinal sectional front view showing the state of the squeegee blade of the squeegee unit according to the present invention in contact with the screen.

FIG. 8 (B) is a longitudinal sectional front view showing a finished state of printing by the squeegee blade shown in FIG. 8 (A).

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 clamping plate 1 ′ clamping plate 2 squeegee unit 2 ′ tip of squeegee blade 3 elastic plate 4 bolt 5 nut 6 bolt insertion hole 9 opposed clamping surface 10 recess 11 locking step 12 Gap S Solder paste 15 Machine frame C Cantilever spring

Claims (8)

(57) [Claims] 1. A recess having an opposing pressing surface on an inner side.
A holding frame is formed by a pair of holding plates provided, and a single thin squeegee blade having both rigidity and elasticity is provided between the opposing pressing surfaces, and the tip of the squeegee blade is provided on both surfaces of the squeegee blade. the slightly drooping protruded allowed manner, each batch and each one or a plurality of elastic plates were additionally provided with pinched, these
A squeegee unit for a screen printing machine , wherein the clamping plate is tightened by a bolt and a nut or a fastening member with a thread so as to be integrally clamped and held on the opposed clamping surface . 2. A tip of a squeegee blade has a substantially circular cross section.
2. The structure according to claim 1, wherein the shape is formed in an arc shape.
Squeegee unit. 3. The squeegee unit according to claim 1, wherein each elastic plate is made of a thin steel plate curved in an arc shape . 4. A squeegee blade is provided on both sides.
The number of elastic plates is one each , and each elastic plate is made of a reinforced synthetic resin or a nylon-based engineering plastic having good mechanical and chemical properties. The squeegee unit according to claim 1. 5. A pair of holding plates are made of a relatively hard synthetic resin having elasticity, respectively, and a lower portion thereof has a cross-sectional end.
5. The device according to claim 1, wherein the device is formed in a thin shape.
The squeegee unit according to any one of the above. 6. The squeegee unit according to claim 1 , wherein the number of elastic plates attached to both surfaces of the squeegee blade is plural and equal. 7. A holding frame is formed by a pair of holding plates each having a recess having an opposing pressing surface on the inner side, and one thin wall having both rigidity and elasticity is formed between the opposing pressing surfaces. A squeegee blade and a plurality of and the same number of resilient plates, which are superposed stepwise in the form of a leaf spring on both sides of the squeegee blade, are collectively clamped, these,
A squeegee unit for a screen printing machine, wherein said holding plate is tightened by a bolt and a nut or a threaded fastening member so as to be integrally held by said opposing holding surface. 8. The squeegee blade having a thickness of 0.0
The thickness is 5 to 0.5 mm.
The squeegee unit according to any one of the above.