JPH04332646A - Printer - Google Patents

Abstract

PURPOSE:To perform printing of a higher quality by a method wherein a solder paste pressed into printing holes of a metal mask by moving a squeegee in a direction Y is hardly again scraped at the time of an X-direction printing. CONSTITUTION:A printer in this invention is a printer in which a squeegee 6 is moved in a direction Y and, thereafter, moved in a direction X for conducting screen printing. The printer is provided with a vertical drive motor 22 and a printing pressure controller 31, which control said squeegee 6 so that the printing pressure thereof in an X-direction printing is approximately a half of the printing pressure in a Y-direction printing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus for printing solder paste onto a wiring pattern of a surface mounting board, for example.

0002

2. Description of the Related Art Generally, when a large number of LSIs are mounted on a relatively large circuit board, the mounting is often performed by reflow soldering as described below.

[0003] Reflow soldering first involves applying paste-like solder (
(hereinafter referred to as "solder paste") is supplied. After making each terminal of the LSI correspond to the wiring pattern of this board, this LSI is mounted on the board. Then, the LSI and the substrate are inserted into a heating furnace. With this, LS
Solder I to the printed circuit board.

[0004] With such reflow soldering, a plurality of LSIs can be surface-mounted all at once by one soldering. For this reason, reflow soldering is suitable for mass production, and this method is widely used for surface mounting of large circuit boards.

[0005] In recent years, in response to the demand for higher density and smaller electronic equipment, surface mount type LSI packages have been made to have more terminals and a narrower pitch. For this reason, even more severe conditions are imposed on screen printing technology. A conventional screen printing technique will be explained with reference to FIG. FIG. 3 is an enlarged view of the printed part.

Reference numeral 1 in the figure is a circuit board (hereinafter referred to as "substrate") on which an LSI is mounted. A metal mask 4 for screen printing, which has printing holes 3 corresponding to the wiring patterns 2 of the substrate 1, is arranged on the upper surface of the substrate 1. For example, this metal mask 4 is for QFP (a flat package IC with terminals protruding in four directions), and a plurality of printing holes 3 corresponding to the terminals of the QFP are formed on a thin stainless steel plate. It is provided.

A squeegee 6 is provided above the metal mask 4 for pushing solder paste shown at 5 in the figure into the printing holes 3 of the metal mask 4. . This squeegee 6 is this metal mask 4
is provided across the width direction of the metal mask 4, and the metal mask 4 is pressed while the lower end is in contact with the upper surface of the metal mask 4 with a predetermined printing pressure.
move in the longitudinal direction (direction shown by the arrow in the figure).

The lower end 6a of the squeegee 6 is made of synthetic resin and has elasticity, and is supplied to the front of the squeegee 6 by being pressed against the metal mask 4 with a predetermined impression pressure. The solder paste 5 can be effectively pushed into the printing holes 3.

When the squeegee 6 pushes the solder paste 5 into the printing holes 3 of the metal mask 4, the metal mask 4 is gently driven upward. As a result, solder paste 5 is printed on each wiring pattern 2 of the substrate 1.

0010

[Problems to be Solved by the Invention] By the way, the above substrate 1
In order to effectively print the solder paste 5 on the wiring pattern 2, it is insufficient to move the squeegee 6 forward once. This is because the solder paste 5 may not be in complete contact with the wiring pattern 2 of the board 1.

For this reason, the squeegee 6 is moved back and forth on the metal mask 4 to force the solder paste 5 into the metal mask 4. However, in the past, the printing pressure of the squeegee 6 in the backward movement was the same as the printing pressure in the forward movement, so the solder paste 5 pressed in the forward movement during the backward movement was
There were times when I ended up scraping off the . In this case, as shown in FIG. 4, the printing of the solder paste 5 becomes uneven, making it difficult to perform good soldering.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a printing device that can evenly and uniformly print a binder such as solder paste.

[0013]

[Means for Solving the Problems] The present invention provides a mask member having a printing hole corresponding to a wiring pattern of a substrate, and a mask member having a printing hole that corresponds to a wiring pattern of a substrate, and a mask member that is connected to the substrate so that the printing hole and the wiring pattern face each other. It has a positioning means for positioning the mask member relative to the mask member, and a squeegee, and is supplied onto the mask member by moving the squeegee along the mask member multiple times with a predetermined impression pressure. a printing means for extruding a binder from the printing hole and printing it on the wiring pattern;
The present invention is characterized by comprising a printing pressure control means that sequentially reduces the printing pressure of the squeegee every time the squeegee moves a predetermined number of times.

[0014]

[Operation] According to this structure, it is unlikely that the binder pushed into the printing holes by the squeegee will be scraped off again by the squeegee.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the same components as in the prior art are given the same reference numerals and their explanations will be omitted.

FIG. 1 shows the main parts of a printing apparatus according to the present invention. In the figure, 4 is a metal mask as a mask member. This metal mask 4 is attached to a mask frame 14. The mask frame 14 is provided so that its height can be adjusted by a height adjusting means (not shown).

A holding table 16 is provided below the metal mask 13 as a positioning means for holding the substrate 1 on its upper surface.
is provided. Once the holding table 16 holds the substrate 1 on its upper surface, it slides as shown by arrow A in the figure and positions and drives the substrate 1 in the X and Y directions. A squeegee device 18 is provided above the metal mask 4 as a printing means.

The squeegee device 18 includes a squeegee 6,
an X-direction drive device 20 that drives the squeegee 6 in the X-direction;
a Y-direction drive device 21 that drives the squeegee 6 in the Y-direction;
A vertical drive motor 22 that moves the squeegee 6 up and down, and a
A stepping motor 23 rotates the motor 6 about 90 degrees about the axis e.

The X-direction drive device 20 includes a first guide rail 25 provided along the Y direction and a pair of first sliders 26, 26 provided at both ends of the first guide rail 25. It consists of The pair of first sliders 26
, 26 are slidably attached to a pair of second and third guide rails 27 and 28, respectively, which are provided parallel to each other and spaced apart from each other along the X direction. The first guide rail 25 is driven in the X direction by an X drive source (not shown).

A second slider 30 serving as the Y-direction drive device 21 is provided on the first guide rail 25 so as to be slidable therein. And this second slider 30
is driven in the Y direction by a Y drive source (not shown).

A stepping motor 23 having a vertical axis and a vertical drive motor 22 for driving the stepping motor 23 in the vertical direction are integrally provided on the lower surface side of the second slider 30. ing. This vertical drive motor 22 is connected to a printing pressure control device 31, and is operated by commands from this printing pressure control device 31.

The lower end of the drive shaft 23a of the stepping motor 23 is fixed to one end in the width direction of the upper end surface of the squeegee 6. That is, this squeegee 6 is driven by the squeegee device 18 in the θ, Z, X, and Y directions. Next, the operation of this device will be explained.

The holding table 16 moves in the direction shown by the arrow A in FIG. 1, so that the substrate 1 held on its upper surface faces the lower surface of the metal mask 4. Then, the first positioning mark A provided on the substrate 1 by moving in the XY direction
and the second positioning mark B provided on the metal mask 4 side. With this, the above metal mask 4
The printing hole 3 and the wiring pattern 2 of the substrate 1 are positioned to face each other.

Once the printing holes 3 of the metal mask 4 and the wiring pattern 2 of the substrate 1 have been positioned, the mask frame 14 is driven downward. When the lower surface of the metal mask 4 comes into contact with the upper surface of the substrate 1, the mask frame 14
stops descending.

Next, the squeegee 6 is driven downward from the state shown in FIG. 1 by the vertical drive motor 22. As shown with reference to FIG. A solder paste 5 as a bonding agent is supplied in front of the wafer.

Next, a Y drive source (not shown) is activated, and the second slider 30 is driven in the Y direction along the first guide rail 25. With this, the above squeegee 6
As shown in FIG. 2(a), Y
The solder paste 5 is pushed into each printing hole 3 by moving from one end to the other end in the direction.

The squeegee 6 is attached to the Y of the metal mask 4.
When the other end in the direction is reached, the vertical drive motor 22 is activated to lift the squeegee 6 by a small amount. Then, the stepping motor 23 operates, and the squeegee 6
is rotated about 90 degrees around the axis e as shown in FIG. 2(b). As a result, the squeegee 6 is positioned with its width direction parallel to the Y direction.

In this state, the printing pressure control device 31 issues a control signal to the vertical drive motor 22, and the squeegee 6
The vertical drive motor 22 is operated so that the printing pressure is approximately halved.

[0029] Next, the X drive device 20
, and slide along the third guide rails 27 and 28 in the X direction. With this, as shown in Figure 2(c),
The squeegee 6 presses the solder paste 5 into each of the printing holes 3 with approximately half the printing pressure as in the case of printing in the Y direction, while pressing the solder paste 5 over the metal mask 4 from one end in the X direction to the other end. Move to the department.

The squeegee 6 is attached to the X of the metal mask 4.
When reaching the other end in the direction, the squeegee 6 is driven upward by the vertical drive motor 22. Then, the mask frame 14 is gently driven upward. As a result, the solder paste 5 pushed into the printing hole 3 separates from the metal mask 4 and is printed on the wiring pattern 2 of the substrate 1.

According to this configuration, the squeegee 6
The printing pressure for printing performed by moving in the X direction (second printing) was approximately half the printing pressure for printing performed by moving in the Y direction (first printing), so for printing in the X direction ( second printing),
In printing in the Y direction (first printing), the printing hole 3
It is rare to scrape off the solder paste 5 that has been pushed into... Also in printing in the X direction (second printing), it is possible to effectively push the solder paste 5 into the printing holes 3. This makes it possible to print with better quality than the conventional example, that is, to print a sufficient amount of solder paste 5.

Further, according to the above-described configuration, the squeegee 6
Since the moving direction is not only in one direction but also in the X direction and the Y direction, the solder paste 5 is applied almost uniformly to the plurality of printing holes 3 not only in one direction but also in the entire area. It is possible to push it. This makes it possible to make the printed state of the solder paste 5 more uniform. Note that this invention is not limited to the one embodiment described above, and can be modified in various ways without changing the gist of the invention.

For example, in the above-mentioned embodiment, the squeegee 6 is operated once in each of the X and Y directions, but it may be configured to be operated multiple times in each direction. According to such a configuration, more uniform printing can be performed. In this case, if the printing pressure is reduced each time the printing is performed, the solder paste 5 that has been printed once will be less likely to be scraped off again, so it is possible to perform good printing. .

Further, in the above embodiment, the squeegee 6 is configured to move in the X direction and the Y direction, but it may be configured to reciprocate only in the X direction or to reciprocate only in the Y direction. You can also do it. In this case, the printing pressure is changed between forward and backward movements.

Furthermore, in the above embodiment, the printing pressure for printing in the X direction was set to approximately half the printing pressure in the Y direction, but if the printing pressure in the X direction is smaller to some extent than the printing pressure in the Y direction, You can get the same effect. For example, the printing pressure may be about 70%.

Further, in the above embodiment, the printing pressure of the squeegee 6 is changed by the vertical drive motor 22, but a mechanical structure such as a cam may also be used. - A mechanism for changing the printing pressure may be provided inside the cage 6, and any structure that can change the printing pressure is sufficient.

Further, in the above embodiment, the stepping motor 23 itself is driven in the vertical direction, but the drive shaft 2 of the stepping motor 23 is
A configuration may be adopted in which only 3a is moved up and down.

Further, in the above embodiment, the drive shaft 23a is fixed to one end of the upper end surface of the squeegee 6, but it is not fixed to the side surface of the squeegee 6 or near the center of the upper end surface. It's okay if it's done.

On the other hand, in the above embodiment, the solder paste 5 is printed, but other bonding agents such as conductive adhesive (thermosetting adhesive containing conductive particles) etc. may also be printed. You can also do it.

[0040]

Effects of the Invention As explained above, in the printing apparatus of the present invention, in screen printing performed by moving the squeegee multiple times, each time the squeegee moves once, the squeegee is moved. The printing pressure was controlled to be smaller than the previous one.

[0041] According to this configuration, the solder paste pushed into the printing hole of the metal mask by the movement of the squeegee is less likely to be scraped off again by the squeegee, resulting in better quality. It is possible to perform various printing.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the invention.

FIGS. 2(a) to 2(c) are plan views illustrating the printing process.

FIG. 3 is a perspective view showing general screen printing.

FIG. 4 is a perspective view showing a printing state of conventional screen printing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Board, 2... Wiring pattern, 3... Printing hole, 4... Metal mask (mask member), 5... Solder paste (binder), 6... Squeegee, 16... Holding table ( 18... squeegee device (printing means), 22... vertical drive motor, 31... printing pressure control device (printing pressure control means).

Claims (1)

[Claims] 1. A mask member having a printing hole corresponding to a wiring pattern on a board; and relatively positioning of the board and mask member so that the printing hole and the wiring pattern face each other. and a squeegee, and by moving the squeegee along the mask member multiple times with a predetermined printing pressure, the binder supplied on the mask member is removed from the printing hole. A printing device comprising a printing means for printing on the extruded wiring pattern, and a printing pressure control means for sequentially reducing the printing pressure of the squeegee every time the squeegee moves a predetermined number of times. .