JPS5945238B2 - Squeegee control method in screen printing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a squeegee control system in a screen printing machine that prints patterns on, for example, semiconductor thick film circuit boards.

The squeegee control means in conventional screen printing machines of this type is such that by turning on an operation switch, for example, a hood switch, the squeegee, which has returned to the starting position, descends and presses onto the printing surface of the printing material through the screen. Pressure is applied to the screen, and the ink immediately starts moving in a predetermined direction to transfer the ink that has already been supplied onto the screen to the printing material.

When the squeegee has moved a predetermined amount, the squeegee is raised, jumps over the residual ink, and is further moved in the same direction as described above by a predetermined amount, and then the squeegee is returned to complete the operation cycle. However, such conventional squeegee control means has the following disadvantages.

In other words, as soon as the squeegee moves a predetermined amount during the printing operation, the squeegee rises rapidly, so while the printing material and the screen are adsorbed by the adhesive force of the transferred ink, the printing material and the screen suddenly move. The pressing force is released, and high-precision printing cannot be expected. Conventionally, this problem of plate separation has been avoided by increasing the distance between the screen and the printing material, increasing the stroke length of the squeegee, or slowing down the moving speed of the squeegee. However, with such a method,
The surface tension of the screen loosens and distortion occurs due to screen elongation, shortening the life of the screen and increasing printing errors.Furthermore, the moving speed of the squeegee must be slowed down.
There have been various inconveniences, such as ink tending to flow into non-printing areas, which impairs printing performance. The present invention was made in view of the above circumstances, and an object of the present invention is to provide a squeegee control method for a screen printing machine that can reliably perform highly reliable and high-precision printing without deteriorating the life of the screen.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 11 is a printing material such as a semiconductor integrated circuit board, 12 is a screen on which a printing pattern is formed, and 13
1 is a squeegee, 14 is a squeegee head, 15 is a squeegee down piston that controls the vertical movement of the squeegee 13, 16 is a squeegee moving piston, and 11 is the squeegee 1
3, a microswitch for detecting the squeegee release position when moving forward; 18, a microswitch for detecting the stop position when the squeegee 13 moves forward; 19, a microswitch for detecting the squeegee release position when the squeegee 13 moves backwards. 20 is a micro switch for detecting the stop position when the squeegee 13 moves backward;
21 is a cam for operating the micro switch 17, 22 is a cam for operating the micro switch 18, 23 is a cam for operating the micro switch 12, and 24 is a cam for operating the micro switch 20. A cam, 25 is a timer circuit which will be described in detail later and receives the output of the micro switch 17 and performs a timing operation in a preset time period, 26 is a food switch operated at the start of operation, and 27 is the micro switch 18.
, 19, 20, timer circuit 25 and food switch 2
A relay circuit 28 which is operated in response to the outputs of the relay circuit 27 is an air solenoid valve mechanism which drives and controls the squeegee down piston 15 and the squeegee moving piston 16 by the output of the relay circuit 27. FIG. 2 shows an example of the configuration of the timer circuit 25, in which Ql, Q2, Q3,
Q4 is a switching transistor, R, to Rll are operating resistors of each of the transistors Q to Q4, VR and C are variable resistors and capacitors for determining the timer operating time, RLl (C), BL2 (C) ) is the relay coil, RLl (NO) is the above relay coil RLl (C)
The normally open side contact, RL, (NC) is also the normally closed side contact, R
L2 (NC) is the normally closed contact of relay coil RL2 (C), C2 is a charging capacitor for temporarily demagnetizing the relay coil RL2 (C), and D is the relay coil R.
17c is a movable contact of the micro switch 17, 17a is a normally open fixed contact, and 17b is a normally closed fixed contact. The operation of the timer circuit 25 in such a configuration will now be explained with reference to the time chart shown in FIG.
When the micro switch 17 is actuated by the cam 21 and the movable contact 17c comes into contact with the normally open fixed contact 17a, the switch is turned on as shown in FIG. 3a.
Transistors Ql and Q3 are both turned off, and transistors Q3 and Q4 are both turned on, so that relay coil RLl (C) is demagnetized and enters a self-holding state. As a result, relay coil RLl (
The normally open side contact RLl (NO) operated by C) is on (
The normally closed contact RLl (NC) is in the off (open) state as shown in FIG. 3b. After the movable contact 17c of the microswitch 17 returns to the normally closed fixed contact 17b, the transistor Q1 changes to the variable resistance V.
It turns on after a time determined by the time constant of Rl and capacitor C1, and as a result, the subsequent transistor Q
2 is off, Q3 is on, and Q4 is off, and the relay coil RLl (C) is de-energized, and at this time, the charge stored in the capacitor C2 is transferred to the relay coil RL2.
(C), and the normally closed contact RL2 (NC) of this relay coil RL2 (C) is temporarily turned on as shown in FIG. 3C.

Therefore, each relay coil R that is not inserted in the timer circuit
Normally closed contact RLl (NC) of Ll (C), RL2 (C)
, RL2 (NC) switch outputs Sl, S2 are the first
This is supplied to the relay circuit 27 shown in the figure. Here, to describe the operation of the device with the above configuration, by turning on the hood switch 26, the squeegee down piston 15 is driven, and the squeegee 13, which has returned to the starting position, descends and presses the screen 12. The screen 12 and the printing material 11 are brought into pressure contact with each other.

When the squeegee 13 is lowered by a predetermined amount, the squeegee moving piston 16 is driven to drive the squeegee 13 forward, and the ink (not shown) supplied to the screen 12 is transferred onto the printing medium 11. Furthermore, the squeegee 13 is driven forward and the cam 21 comes into contact with the actuator of the micro switch 17. When the micro switch 17 is turned on, the timer circuit 25 shown in FIG. ), the squeegee 13 stops at that position. The operating time of the timer circuit 25 at this time can be set arbitrarily by a variable resistor VRl, and the ink (
The operation time is selected and set in accordance with the period during which the object is attracted by the adhesive force (not shown). When the time counting operation of the timer circuit 25 is completed, the switch output S2 is turned off (open) for a period of time, and the squeegee 13 is controlled to move upward by this signal, and moves in the forward direction again. When the cam 22 comes into contact with the actuator of the microswitch 18 and turns on the microswitch 18, the forward drive control of the squeegee moving piston 16 is prohibited, and then the movement moves backward. In this way, after ink transfer, the operation of the timer circuit 25 causes the printing material to
1 and the screen 12 are adsorbed by the adhesive force of the ink, a signal is output to control the rise of the squeegee 13, so that the screen 12 rises while being adsorbed to the printing material 11. Printing defects caused by such problems are eliminated, yields can be improved, and since the moving speed of the squeegee 13 can be set regardless of plate separation of the screen, printing performance can be ignored and the rework rate can be reduced.
Furthermore, since there is no need to increase the distance between the screen 12 and the printing material or to increase the stroke of the squeegee 13, the life of the screen 12 can be extended. Although the embodiments described above are constructed using an electronic timer circuit, the present invention is not limited to this, and for example, a pure mechanical timer, a delay relay element, etc. can be easily used.

Further, in the above embodiment, the squeegee head 14 is pneumatically operated.
Although the drive control is described above, the drive control is not limited to this, and can be easily implemented by, for example, a hydraulic servo type or an electric type. As detailed above, according to the present invention, in a screen printing machine that transfers ink onto a substrate through a printing screen by moving a squeegee, a timer operates after the ink is transferred by moving the squeegee. By prohibiting the squeegee from opening (raising) during the period when the screen and printing material are adsorbed by the adhesive force of the ink, highly reliable high precision can be achieved without deteriorating the life of the screen. It is possible to provide a squeegee control system in a screen printing machine that allows printing to be performed reliably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of the configuration of a timer circuit used in the above embodiment, and FIG. 3 is for explaining the operation of the timer circuit. This is a time chart. 11... Printing material, 12... Screen 13... Squeegee, 14... Squeegee head, 15... Squeegee down piston, 16... ... Squeegee moving piston, 17, 18
, 19, 20... Micro switch, 21, 2
2, 23, 24...cam, 25...timer circuit, 26...hood switch, 27...
...Relay circuit, 28...Air solenoid valve mechanism.

Claims (1)

[Claims] 1. In a screen printing machine that transfers ink onto a printing material through a printing screen by moving a squeegee, there is a switch that detects when the squeegee has moved a certain amount, and an output from this switch that separates the squeegee from the printing screen. A squeegee control in a screen printing machine having a functional configuration in which a timer is interposed between the squeegee and the squeegee drive mechanism, and after the squeegee has moved a certain amount, the squeegee is separated from the printing screen after the time set in the timer has elapsed. method.