JPH02205097A - Automatic control mechanism for shear rate of cream solder printing machine - Google Patents

Abstract

PURPOSE:To enable uniform printing of cream solder to be done by calculating the shear rate which maintains the properties such as viscosity of cream solder, etc., in accordance with the external conditions such as temperature of cream solder at a specified value so as to do automatic control. CONSTITUTION:There are A/D converters 71 and 72, which convert the analog measurement values of external conditions such as the temperature, viscosity, etc., of cream solder by sensors 7 and 8 into digital values, a controller 5, which receives the digital measurement values and calculates the shifting speed of the squeegee 1 to keep the cream solder 4 at the specified viscosity, and a storage part 6, which holds data, etc., required in calculation. Further, the controller 5 is composed the A/D converters 71 and 72, an interface part 53, an interface part 54 with a driving controller, the CPU 51 to execute operation, judgement, etc., a memory 52, etc. There is further a driving controller 9 which drives and controls the shifting of the squeegee 1 through a motor 11, according to the value of the shifting speed of the squeegee 1 to maintain the cream solder at the specified viscosity which is calculated by this controller 5.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention is directed to applying cream solder to a PCB ( Regarding cream solder printing machines that transfer onto printing objects such as printed circuit boards, in particular, the external conditions such as the temperature and viscosity of the cream solder are determined, and the shear rate and squeegee are used to maintain the cream solder at a predetermined viscosity. This invention relates to an automatic shear speed control mechanism for a cream solder printing machine that calculates the moving speed and controls the drive.

(Prior Art) When mounting components on a PCB (printed circuit board, hereinafter simply referred to as a board), a cream solder printing machine is used to transfer cream solder onto an object to be printed.

In a cream solder printing machine, cream solder placed on a transfer member such as a metal mask is transferred onto an object to be printed such as a PCB while being squeezed (moved) by the movement of a squeegee.

FIG. 5 shows an example of transfer by such a ream solder printing machine. A metal mask 3 is placed on a substrate 2 and fixed on a cream solder printing machine.

This metal mask 3 has slits 31 at locations where the cream solder □ is to be transferred to the substrate 2 of the object to be printed. Then, the cream solder 4 is placed on the metal mask 3 and squeezed by moving the squeegee 1. The cream solder 4 flows through the slit 31 formed in the metal mask 3 while being squeezed by the movement of the squeegee 1, and is transferred onto the substrate 2.

FIG. 6 shows an example of cream solder 41 printed on the substrate 2 by transfer.

In this way, on the cream solder printed on the board etc.,
Components and the like are mounted, and soldering is completed through a reflow process and the like.

In such a ream solder printing machine, it is important to maintain the cream solder in a state with a predetermined viscosity and thixotropy. The viscosity of the cream solder is agitated when the squeegee moves over a transfer member such as a metal mask, and the viscosity of the cream solder decreases to a specific value and stabilizes. Further, when the material passes through a transfer slit provided in a transfer member such as a metal mask and is placed on the object to be printed, it is stirred even faster and its viscosity decreases. This reduction in viscosity allows smooth transfer.

(Problem to be solved by the invention) However, various properties such as the viscosity and thixometry of cream solder show various changes due to external phenomena such as temperature, humidity, and external shear stress due to squeegee printing, and they are always in the same state. Not in.

FIGS. 3 and 4 show characteristic diagrams showing the influence of the shear rate (corresponding to the moving speed of the squeegee) of the cream solder, changes in temperature, etc. on the viscosity (P) of the cream solder.

As is clear from these figures, even at the same temperature, the viscosity (P) of cream solder varies depending on the shear rate. Also,
Even at the same shear rate, the viscosity (P) decreases over time.

Despite various variations in properties such as the viscosity of cream solder, in conventional cream solder printing machines, the moving speed of the squeegee and therefore the squeegeeing speed (shearing speed) of cream solder remains fixed. Met. For this reason, for example, problems such as the shape of the cream solder to be transferred are not constant occur, and problems such as the inability to obtain uniform printing may occur.

This invention was made in view of the above conventional circumstances, and is a cream solder printing method that automatically controls the movement speed of the squeegee to be appropriate according to the external conditions such as the temperature and viscosity of the cream solder. It is an object of the invention to provide an automatic shear rate control mechanism for a machine.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve such an object, in the automatic shear speed control mechanism of the cream solder printing machine according to the present invention, the printing target is sheared by the movement of the squeegee. A sensor that determines the external condition such as the temperature and/or viscosity of the cream solder to be transferred onto the body; The squeegee is configured to include a speed calculation unit that calculates the movement speed of the squeegee to maintain the viscosity of the squeegee, and a drive control unit that drives and controls the movement of the squeegee according to the movement speed calculated by the speed calculation unit.

(Function) According to the automatic shear rate control mechanism of the cream solder printing machine with such a configuration, the temperature and/or viscosity of the cream solder that is sheared and transferred onto the printing target by the movement of the squeegee is controlled. The external state of the vehicle is determined by the sensor, and the determined value is sent to the speed calculation section. Then, the speed calculation unit that receives this side predetermined value calculates the moving speed of the squeegee to maintain the cream solder at a predetermined viscosity. Then, the moving speed 1 calculated by this speed calculating section
4, the movement of the squeegee is drive-controlled by the drive control unit.

In this way, the shear rate of the ream solder, and therefore the movement speed of the squeegee, is automatically determined according to the external conditions such as the temperature and viscosity of the cream solder, and the movement of the squeegee is controlled. Become.

(Embodiment) FIG. 1 is a block diagram showing the main structure of an automatic shear rate control mechanism of a cream solder printing machine according to an embodiment of the present invention.

An object to be printed, for example, a PCB (printed circuit board, hereinafter simply referred to as a substrate) 2, and a transfer member, for example, a metal mask 3, which is placed on the substrate 2, are both fixed on a cream solder printing machine. This metal mask 3 has slits at the locations where the cream solder is to be transferred to the substrate 2 of the object to be printed, and the cream solder 4 is placed on top of the slits. And a squeegee 1 for squeezing (slipping) this cream solder 4,
A drive mechanism for moving this squeegee 1, such as a motor 1
There is 1.

Driven by the motor 11, the squeegee 1 is moved over the metal mask 3, and while squeezing (slipping) the cream solder, it is transferred onto the substrate 2 of the printing target via the metal mask 3.

At this time, a sensor for determining external conditions such as the temperature and/or viscosity of the cream solder 4 which is shearly moved by the movement of the squeegee 1 and transferred onto the substrate 2 of the printing target; a temperature sensor 7 and a viscosity sensor; A sensor 8 is provided at a position in contact with the cream solder 4 that is being displaced.

A/D converters 71 and 72 that convert analog fixed values of external conditions such as the temperature and viscosity of the cream solder 4 detected by the sensors 7 and 8 into digital values, and the A/D converter 71
and 72, and calculates the moving speed of the squeegee 1 to maintain the cream solder 4 at a predetermined viscosity.
For example, there is a storage unit 6 that holds a table of correspondence values between temperature, etc. and shear rate according to the characteristic diagram shown in FIG. 3 and the like. The control unit 5 further includes an A/D converter 7
1 and 72, and an interface section (I/F) 53 with the drive controller described later.
) 54, a CPU 51 that executes calculations, judgments, etc., and a memory 52 that provides a storage area for temporary data during these calculations, etc.

Then, in response to the moving speed of the squeegee 1 that maintains the cream solder 4 at a predetermined viscosity, which is calculated by the control unit 5,
The movement of squeegee 1 is controlled by motor 1 according to the value of this movement speed.
A drive controller 9 is provided which controls the drive via 1.

FIG. 2 is a flowchart showing the operation of the automatic sliding speed control mechanism of the cream solder printing machine according to one embodiment of the present invention.

For example, in the graph of FIG. 3, suppose that 100 OP is selected as the viscosity value that provides the best printing condition. According to the graph showing cream solder characteristics with respect to shear rate and temperature changes, a viscosity value of 1000P means that when the cream solder temperature is 20°C, the shear rate is 17.0 per second, and when the temperature is 25°C, it is 6. 0 and 30℃, 3.
It will be obtained as 0. Furthermore, it is also necessary to take into account changes in viscosity over time as shown in FIG. 4 to the values thus obtained from the graph in FIG. 3.

The automatic shear rate control mechanism of the cream solder printing machine according to the present invention determines the temperature etc. using a sensor, calculates the shear rate using the method described above, and feeds it back to the movement control of the squeegee. Automatic control has been realized.

First, fixed value information such as temperature/viscosity determined by the temperature sensor 7 and/or viscosity sensor 8 shown in FIG. is received by the CPU 51 (step 11 in FIG.
0).

Then, in accordance with this fixed value, a storage unit 6 stores information such as a table of corresponding values to the sliding speed based on a graph of changes in characteristics of cream solder due to changes in temperature, etc., as shown in FIG. 3, etc. Information on the optimum shear rate is read out from (step 120 in FIG. 2).

From the information on the shear speed obtained in this way, the CPU 51 calculates the moving speed of the squeegee.

At this time, it is also possible to add, for example, an integral term or a differential term in PID (proportional/integral/derivative) control. Furthermore, the changes over time may not be held as a table in the storage section 6, but may be taken into account through calculations here (step 130 in FIG. 2).

The squeegee movement speed information obtained in this way is
The information is sent to the drive controller 9 and output as a control signal according to this speed information to the drive motor 11 of the squeegee 1, etc., so that the moving speed of the squeegee 1 is automatically controlled (step 140 in FIG. 2).

In the above embodiment, a temperature sensor and a viscosity sensor (or only one of them is possible) are provided separately from the squeegee and brought into contact with the cream solder as sensors for determining the external state of the cream solder. was shown, but
The configuration is not limited to this, and it is of course possible to use other types of sensors, or a configuration in which these sensors are built into the squeegee, for example. Further, although a metal mask is shown as an example of the transfer member, it goes without saying that similar effects can be obtained by using a mesh screen method, for example.

[Effect of the invention] As described above, according to the automatic shear rate control mechanism of the cream solder printing machine according to the present invention, the external conditions such as the temperature of the cream solder are determined, and the cream solder is adjusted according to the external conditions. Automatic control is performed by calculating the shear rate to maintain properties such as viscosity at predetermined values, and therefore the moving speed of the squeegee.

Therefore, properties such as the viscosity of the cream solder are always maintained in a substantially constant state, and uniform ream solder printing can be performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a cream solder printing machine and automatic shear rate control mechanism according to an embodiment of the present invention, Fig. 2 is a flowchart showing the operation of the same embodiment mechanism, and Figs. 3 and 4 are cream solder printing machines. FIG. 5 is an explanatory diagram of the operation of the cream solder printing machine, and FIG. 6 is a perspective view showing an example of printing by the cream solder printing machine. 1... Squeegee 2... Board 3... Metal mask 4... Cream solder 5... Control section 6...
Memory unit 7...Temperature sensor 8...Viscosity sensor 9...
・Drive controller patent attorney Hidekazu Miyoshi (, I) Bait! 11 (,I)-no! (1

Claims (1)

[Claims] (1) A sensor that determines the external state of the cream solder that is sheared and transferred by the movement of the squeegee and transferred onto the printing target; and a sensor that determines the external state of the cream solder by this sensor, and determines the cream solder in a predetermined manner. A cream solder comprising: a speed calculation unit that calculates the movement speed of the squeegee to maintain the viscosity; and a drive control unit that drives and controls the movement of the squeegee according to the movement speed calculated by the speed calculation unit. Automatic shear speed control mechanism for printing presses.