JPH02174192A - Printing of cream solder - Google Patents

Abstract

PURPOSE:To immediately print and coat with cream solder of optimum viscosity at the time of restarting after printing is started or interrupted by moving the cream solder by a squeegee and a spatula at the time of waiting for printing, and maintaining a printable cream solder viscosity state. CONSTITUTION:Both a squeegee 18 and a spatula 20 are reciprocated at a waiting position of the corner of a screen in contact with a screen in a waiting state for printing such as before the start of printing or at the time of interruption of printing (at the time of supply of cream solder 22, at the time of trouble) to apply similar motion (viscosity managing motion) to that at the time of printing to the cream solder 22 held between the squeegee 18 and the spatula 20 to prevent the viscosity of the cream solder 22 from varying. Thus, printing can be immediately started or restarted with the cream solder 22 of optimum viscosity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objective of the Invention) (Industrial Application Field) The present invention relates to a cream solder printing method for printing and applying cream solder to necessary locations on a printed wiring board using a screen printing method.

(Prior Art) There is a screen printing machine as shown in Japanese Utility Model Application Publication No. 63-101531. When printing, this screen printing machine moves the squeegee over the screen supplied with ink.
By moving the squeegee I, printing is performed on the printing material below the screen, but the squeegee is stopped at a standby position at one corner of the screen except when printing.

(Problems to be Solved by the Invention) When such a screen printing machine is used to print and apply cream solder, the following problems occur.

That is, cream solder has a thixotropic property in which the viscosity decreases when shearing force is continuously applied, and the viscosity becomes stable when the viscosity decreases to a certain value. On the other hand, this cream solder has the property of increasing its viscosity when it is in a stationary state. Therefore, in the printing standby state, the viscosity of the cream solder increases W, and the printability of the cream solder after the printing standby is affected by the change in viscosity, which changes the cream solder printability after the printing standby state.

For this reason, at present, at the start of printing, "trial printing" is performed using a large number of substrates (for setting conditions) until the cream solder stabilizes at the optimum viscosity. If conditions are bad,
This operation must be repeated many times.

The present invention aims to prevent changes in the viscosity of cream solder during printing standby when applying cream solder to a board using a screen printing machine, and to eliminate "test printing" at the start of printing. .

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a cream solder printing method in which cream solder 22 is printed and coated on a printed wiring board by a screen printing method using a squeegee 18 that operates on a screen 11. 18 and a spatula body 20 arranged in parallel with this squeegee are moved up and down alternately in relation to the reciprocating motion, and either one of them applies the cream solder 22 on the screen 11. When waiting for printing, The squeegee 18 and the spatula body 20 are both brought into contact with the screen 11 and swung at the standby position, and the cream solder 22 between the squeegee 18 and the spatula body 20 is given movement, thereby increasing the viscosity of the cream solder 22. This is a cream solder printing method that prevents.

(Function) In the present invention, in a printing standby state such as before starting printing or when printing is interrupted (when replenishing cream solder, when a trouble occurs), both the squeegee 18 and the spatula body 20 are in contact with the screen 11 and are in a standby position at one corner of the screen. Squeegee 1 moves back and forth in position.
A motion (viscosity control motion) similar to that during printing is given to the cream solder 22 sandwiched between the cream solder 8 and the spatula rest 20 to prevent the viscosity of the cream solder 22 from changing. Therefore, printing can be started or resumed immediately with cream solder having an optimum viscosity.

(Examples) Hereinafter, the present invention will be described in detail with reference to examples shown in the drawings.

As shown in FIG. 2, a pair of timing pulleys 12 are installed above the screen 11 in the screen printing machine.
A timing belt 13 is wound around the timing belt 13, and one of the timing pulleys 12 is rotated forward or reverse by a motor 14. A slider 15 is integrally provided on the timing belt 13, and the slider 15 is guided by a linear guide 16 to move horizontally in parallel with the screen 11. A squeegee 18 that is moved up and down by an air cylinder 17 and a spatula rest 20 that is moved up and down by an air cylinder 19 are provided below the slider 15. This spatula body 2
0 is a squeegee (in the case of a double squeegee) or a cream solder return plate (in the case of a jingle squeegee).

A viscosity measurement sensor 2 is installed between the squeegee 18 and the spatula 20.
1 is provided, and the viscosity of the cream solder 22 between the squeegee 18 and the spatula body 20 is measured by this sensor 21.

FIG. 3 shows the case of a double squeegee, in which a cream solder escape prevention plate 23 is provided with a slight gap between the end of the squeegee 18 and the end of the spatula body (squeegee) 20a, and these prevent the cream solder from escaping. It surrounds 22. This plate 23 is attached to the slider 15. Note that the gap is set to the minimum value so that the cream solder does not escape.

Figure 4 shows the case of a jingle squeegee, with squeegee 18
At both ends of the spatula body (cream soldering board) 20b
The ends of the bent portions on both sides are opposed to each other with a slight gap in between, and the cream solder 22 is surrounded by these.

Then, as shown in Figure 1), before printing starts,
In the printing standby state, such as when printing is interrupted (replenishing cream solder, 1 to syllable generation), the squeegee 18 and the spatula body 2
0 contact the screen 11 and move back and forth at a standby position at one corner of the screen, causing the cream solder 22 sandwiched between the squeegee 18 and the spatula body 20 to move in the same way as when printing (
(viscosity control movement) to prevent changes in the viscosity of cream solder.

During printing, the reciprocating motion shown in FIGS. 1(B) and 1(C) is performed. In the forward stroke shown in FIG. 1 ([3), the squeegee 18 is lowered by the cylinder 17 and the screen 1 is
1, and the spatula body 20 is brought into contact with the screen 11.
The cream solder 22 on the screen 11 is scraped from the right side of the screen to the left side using the squeegee 18, and then, in the backward stroke shown in FIG. 1(C), the spatula rest 20 is lowered using the cylinder 19. While making contact with the screen 11, the squeegee 18 is raised from the screen 11, and the cream solder 22 on the screen 11 is scraped from the left side to the right side of the screen using a spatula 20.

At this time, if the spatula body 20 is a squeegee (double squeegee), printing is performed also in this backward stroke, and the spatula body 20
If 0 is a cream solder return plate (jingle squeegee), this spatula body 20 scrapes the cream solder 22 back to its original position.

(Effects of the Invention) According to the present invention, the cream solder can be moved by the squeegee and spatula even during printing standby, and the viscosity of the cream solder can be maintained so that printing is possible. The viscous cream solder can be applied immediately by printing, and there is no need to perform trial printing using a large number of substrates (for setting conditions) as in the past.

[Brief explanation of the drawing]

Fig. 1 is an operational explanatory diagram showing one embodiment of the cream solder printing method of the present invention, Fig. 2 is a sectional view of a screen printing machine used in the method, and Fig. 3 is an example of the squeegee and spatula body ( Figure 4 is an explanatory diagram showing the squeegee and another example of the spatula body (jingle squeegee).
It is an explanation and a diagram showing. 11... Screen, 18... Squeegee, 20... Spatula body, 22... Cream solder.

Claims (1)

[Claims] (1) In a cream solder printing method in which cream solder is printed and applied to a printed wiring board by a screen printing method using a squeegee that slides on a screen, during printing, a squeegee and a spatula body installed in parallel with this squeegee are used. The squeegee and spatula body are moved up and down alternately in a reciprocating motion to scrape up the cream solder on the screen with one of them, and when waiting for printing, both the squeegee and spatula body are brought into contact with the screen and swung in the standby position. A cream solder printing method characterized in that an increase in the viscosity of cream solder is prevented by applying motion to the cream solder between a squeegee and a spatula body.