JPH0691846A - Cream solder screen printing machine - Google Patents

Abstract

PURPOSE:To provide a cream solder screen printing machine capable of detecting printing defects by itself. CONSTITUTION:An optical sensor 8 observes a screen plate and outputs a signal indicating an open state of holes (which are provided in the screen plate in a predetermined pattern for printing a cream solder). A converter 22 converts the signal outputted from the optical sensor 8 to a digital signal and outputs this digital signal. A measurement data storage part 24 stores the signal outputted from the converter 22 as measurement data. A reference data storage part 23 stores reference data indicating a normal pattern of a screen plate. A comparison part 25 detects the clogging of the screen plate by comparing the measurement data with the reference data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cream solder screen printer used in a surface mounting process of an electronic circuit board (printed circuit board).

[0002]

2. Description of the Related Art When screen printing is performed using a cream solder screen printing machine, as shown in FIG. 3 (a), a screen plate (attached to the screen frame 1) 2 Cream solder 3 on top
And the printed circuit board 4 is brought into close contact with the bottom of the screen plate 2. In this state, a spatula 5a called a squeegee is moved over the screen plate 2, and solder 3 is attached to the printed board 4 through the hole 2a of the screen plate 2 as shown in FIG.
To print.

Here, as shown in FIG. 1C, when the printed circuit board 4 is peeled from the screen plate 2, the cream solder 3 is not transferred to the printed circuit board 4 and the solder 3 is placed in the holes 2a of the screen plate 2. It may remain. As a result, the printed circuit board 4 was not properly finished, and the solder was thrown into a post-process in a faint state (printing failure).

Such printing defects can be detected by inspecting the solder height on the printed circuit board 4 using a solder height inspection device after printing. However, the separate introduction of the solder height inspection device has a problem that a large capital investment is required. On the other hand, adding the solder height inspection function of the printed circuit board 4 to the printing machine itself means that the solder height after printing is only a few hundred microns at the normal level.
very hard. For this reason, conventionally, the printing failure cannot be detected by the printing machine itself.

Therefore, an object of the present invention is to provide a cream solder screen printing machine which can detect the occurrence of a printing failure by the printing machine itself.

[0006]

In order to achieve the above object, the screen printing machine of the present invention prints cream solder on a substrate in close contact with the screen plate through holes formed in a predetermined pattern on the screen plate. A cream solder screen printer, which is an optical sensor for observing the screen plate and outputting a signal indicating the opening state of the hole, and a conversion for converting the signal output by the optical sensor into a digital signal and outputting the digital signal. Device, a measurement data storage unit that stores a signal output by this converter as measurement data, a reference data storage unit that stores reference data representing a normal pattern of the screen plate, the measurement data and the reference data. It is characterized in that a comparison section is provided for detecting clogging of the screen plate for comparison.

Further, when the screen plate is clogged, a signal indicating that the screen is clogged is received from the comparison section, the printed substrate is held without being discharged, and printing is performed on a new substrate. It is desirable to have control means to stop.

[0008]

In most cases, defective printing is caused by the clogging of the holes of the screen plate with the cream solder. Therefore, the present inventor has created a device for detecting a print defect of cream solder by inspecting a hole of a screen plate instead of inspecting a screen-printed substrate.

The cream solder screen printer of the present invention operates as follows. First, the reference data storage unit stores in advance a normal pattern of the screen plate, that is, reference data representing the position and size of each hole. Next, screen printing is actually performed, and the screen plate is observed by an optical sensor to obtain a signal indicating the opening state of the hole. Then, the converter converts the signal output from the optical sensor into a digital signal, and temporarily stores the signal in the measurement data storage unit as measurement data. Next, the comparison unit compares the measured data with the reference data to detect clogging of the screen plate. That is, the size of each hole is compared and the measured data
When the size of the hole represented by (after printing) is smaller than the size of the hole represented by the reference data, or when no hole can be detected after printing, it is determined that the screen plate is clogged. As described above, according to the cream solder screen printing machine, the printing machine itself can detect the occurrence of printing failure.

When the screen plate is clogged, a signal indicating that the screen is clogged is received from the comparison section, the printed substrate is held without being discharged, and printing is performed on a new substrate. In the case of having the operation stopping portion for stopping, the substrate with defective printing is not put into the subsequent process. Therefore, the yield reduction in the production process is prevented.

[0011]

EXAMPLES The cream solder screen printing machine of the present invention will be described in detail below with reference to examples.

FIG. 1 shows a signal processing system of a cream solder screen printing machine according to one embodiment, and FIG. 2 shows a mechanical system of the printing machine as seen from a side.

As shown in FIG. 2, this cream solder screen printing machine comprises a surface plate 11 and a screen frame 1 mounted on the surface plate 11 by fasteners 12. On the lower surface of the surface plate 11, the printed circuit board 4 to be printed can be brought into close contact with the screen plate 2,
An opening (not shown) having a size larger than that of the printed circuit board 4 is provided. A screen plate 2 having holes in a predetermined pattern is attached to the screen frame 1.

Above the surface plate 11, squeegees 5a and 5b are provided.
A traverse unit 14 that independently adjusts the heights of the squeegees 5a and 5b in the vertical direction, and a guide rod 13 that guides the traverse unit 14 in the front-rear direction are provided. The squeegees 5a and 5b are attached to the traverse unit 14 in a state of forming an inverted V-shape.

A line sensor is provided below the surface plate 11.
A (one-dimensional image sensor) 8, a traverse unit 10 for moving the line sensor 8 in the front-back direction, a feed mechanism 9 and a pulse motor 15 are provided. The line sensor 8 can observe the screen plate 2 and output a signal indicating the opening state of the hole. Further, further below, a substrate support base 6 on which the printed circuit board 4 to be printed is placed, and a substrate up-and-down mechanism 7 for elevating the printed circuit board 4 and the substrate support base 6 are provided. The substrate up-and-down mechanism 7 moves up before printing to bring the printed circuit board 4 into close contact with the screen plate 2, while it goes down after printing and retracts to a height that does not hinder the movement of the line sensor 8.

Further, as shown in FIG. 1, this cream solder screen printer has an A / D converter 22, a measurement data storage section 24, a reference data storage section 23, and a comparison section 25.
And the measurement data storage unit 24 and the reference data storage unit 23.
And a control unit 26 for controlling the operation of the comparison unit 25 is provided. The A / D converter 22 converts the signal output by the line sensor 8 into a digital signal and outputs the digital signal. The measurement data storage unit 24 and the reference data storage unit 23 include a switch 28.
It is possible to receive the signals output from the A / D converter 22 by switching and to store the received signals as measurement data and reference data. The comparison section 25 can receive the signals representing the data stored in the measurement data storage section 24 and the reference data storage section 23 and compare the two data. The motor drive unit 21 drives the pulse motor 15 that moves the line sensor 8 back and forth at a predetermined timing according to an instruction from the control unit 26.

The screen printing machine operates as follows as a whole.

Before starting printing, the substrate up-and-down mechanism 7 shown in FIG. 1 is lowered and the switch 2 shown in FIG.
The line sensor 8 is operated (moved in the front-rear direction) in a state where 8 is switched to the reference data storage unit 23 side. By synchronizing the signal output by the line sensor 8 with the output signal of the motor drive unit 21 (which drives the pulse motor 15), it is possible to obtain two-dimensional image information about the screen plate 2. This two-dimensional image information is converted into the A / D converter 2
2 through the reference data storage unit 23 to the screen version 2
Is stored as reference data representing the normal pattern, that is, the position and size of each hole.

Next, screen printing is actually performed. Specifically, the board up-and-down mechanism 7 shown in FIG. 1 is raised to bring the printed board 4 into close contact with the screen plate 2 and move the squeegee 5a on the screen plate 2. As a result, the cream solder 3 is printed on the printed board 4 through the holes of the screen plate 2. Then, the substrate up-and-down mechanism 7 is lowered.

Next, with the switch 28 shown in FIG. 2 switched to the measurement data storage section 24 side, the line sensor 8 is operated in the same manner as in the step. As a result, the two-dimensional image information about the screen plate 2 after printing is displayed on the A / D
The measurement data is stored in the measurement data storage unit 24 via the converter 22.

Next, the comparison unit 25 compares the measured data with the reference data to detect clogging of the screen plate 2. That is, comparing the sizes of the individual holes,
When the size of the hole represented by the measurement data (after printing) is less than the size of the hole represented by the reference data (before printing), or when no holes can be detected after printing, the screen plate is clogged. judge. In this way, it is possible for the printing machine itself to detect that a printing failure has occurred.

When the screen plate 2 is not clogged, the control unit 26 determines that the printing is normally performed and sends the printed circuit board 4 to the subsequent process. On the other hand, when the screen plate 2 is clogged, the control unit 26
Upon receiving a signal indicating that clogging has occurred from the comparison unit 25, the printed substrate is held without being discharged. Also, printing on a new printed circuit board is stopped. Therefore, the printed circuit board 4 that is defective in printing is not put into a subsequent process, and it is possible to prevent a decrease in yield in the production process.

[0023]

As is apparent from the above, the cream solder screen printing machine of the present invention detects the state of the holes of the screen plate by the optical sensor, and the comparison section detects the measurement data indicating the opening state of the holes. Since the reference data set in advance is compared, clogging of the screen plate can be detected by the printing machine itself.

Further, when the screen plate is clogged, a signal indicating that the screen is clogged is received from the comparison unit, the printed substrate is held without being discharged, and printing is performed on a new substrate. When the control means for stopping the printing is provided, it is possible to prevent the defective printed substrate from being sent to the subsequent process. Therefore, the yield of the production process can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing a signal processing system of a cream solder screen printing machine according to an embodiment of the present invention.

FIG. 2 is a view showing a mechanism system of the cream solder screen printing machine as seen from a side.

FIG. 3 is a diagram illustrating a general method for performing screen printing using a cream solder screen printing machine.

[Explanation of symbols]

1 Screen Frame 2 Screen Plate 3 Cream Solder 4 Printed Circuit Board 8 Line Sensor 9 Sensor Feed Mechanism 10 Sensor Traverse Unit 15 Pulse Motor 21 Motor Drive Unit 22 A /
D converter 23 Reference data storage unit 24 Measurement data storage unit 25 Comparison unit 26 Control unit

Claims (2)

[Claims] 1. A cream solder screen printer that prints cream solder on a substrate in close contact with the screen plate through holes formed in a predetermined pattern on the screen plate, and observing the screen plate to open the holes. An optical sensor that outputs a signal indicating the state, a converter that converts the signal output by the optical sensor into a digital signal and outputs the signal, and a measurement data storage unit that stores the signal output by the converter as measurement data. And a reference data storage unit for storing reference data representing a normal pattern of the screen plate and a comparison unit for comparing the measured data with the reference data to detect clogging of the screen plate. The cream solder screen printing machine. 2. When a clogging occurs in the screen plate, a signal indicating that the clogging has occurred is received from the comparison unit, the printed substrate is held without being discharged, and printing on a new substrate is performed. The cream solder screen printing machine according to claim 1, further comprising control means for stopping.