JPH0227975Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a flux coating device for applying flux to objects to be soldered, such as printed wiring boards.

(Prior Art and its Problems) The reason why flux is applied to an object to be soldered before soldering is to activate the object before soldering and to ensure good soldering.

If the flux does not have an accurate concentration value, good soldering cannot be ensured.

In particular, as soldering becomes more precise in recent years, flux concentration management is required to be more precise.

Incidentally, flux is a liquid mixture of a flux stock solution and a diluent (mainly alcohol).

However, in most conventional flux coating apparatuses, the specific gravity of the flux 3 in the flux tank 2 is simply detected by the specific gravity sensor 4, as in the flux coating apparatus 1, 1' shown in FIG. 1 or 2.
This specific gravity value signal is simply converted into a temperature-corrected specific gravity value based on the signal from the temperature sensor 5 which is also immersed in the flux 3, making it impossible to obtain a flux 3 with an accurate concentration. There is.

6 is a liquid level sensor, and 7 is a flux 3 life sensor.

The flux coating apparatuses 1 and 1' shown in FIGS. 1 and 2 will be explained in detail below.

8 is a control circuit into which the upper and lower limits of the specific gravity of the outputs of the specific gravity sensor 4, temperature sensor 5, liquid level sensor 6, and life sensor 7 are input; The temperature is corrected to the reference temperature and the corrected specific gravity is compared with the upper and lower limit set values. It has a display function that displays an output indicating whether or not the flux 3 should be replaced on a display section (not shown) in response to a signal.

9 and 10 are electromagnetic valves, 11 is a pump, 12 is a stock tank containing stock solution, 13 is a diluent tank containing a diluent (generally alcohol is used), 14, 1
5 is a supply pipe.

Note that the liquid level sensor 6 has three electrodes 6a, 6b, and 6c of different lengths, and the electrodes 6a, 6c,
The upper and lower limits of flux 3 are detected by the conduction between 6b and 6c.

Therefore, the control circuit 8 performs temperature correction of the specific gravity using the output values of the specific gravity sensor 4 and the temperature sensor 5, and compares the temperature-corrected specific gravity with the upper and lower limit values. The output of the control circuit 8 operates the solenoid valve 10 and the pump 11 to supply the diluent in the diluent tank 13 to the flux tank 2, and when the flux is lower than the lower limit set value, the output of the control circuit 8 operates the solenoid valve 9 and the pump 11. The electromagnetic valve 9 and the pump 11 are controlled so that the stock solution in the stock solution tank 12 is supplied to the flux tank 2 by operating the stock solution tank 12 so that the flux 3 has a specific gravity within a predetermined range.

When the flux 3 reaches the lower limit liquid level, the liquid level sensor 6 outputs the lower limit value, and the solenoid valve 9, pump 11, and solenoid valve 10 are controlled by the control circuit 8 so that the specific gravity of the flux 3 falls within a predetermined range. and the pump 11 are operated alternately to supply the undiluted solution or diluted solution to the flux tank 2 until the flux 3 reaches the upper limit.
supply to.

In this way, the flux 3 under constant conditions is always supplied to the flux tank 2, and is applied to objects to be soldered, such as printed wiring boards, by a jet device (not shown).

Another conventional flux coating device 1' will be described below with reference to FIG. Furthermore, the first
Explanation of parts common to the figures will be omitted.

Referring to FIG. 2, 27 is a temperature correction circuit, 28
is a working amplifier, 16 is a digital panel meter, 1
7 is an upper and lower limit specific gravity setting device, and 19 is a solenoid valve control circuit. A control circuit 8 is configured by these.

20 is a pressure air source, and 21 and 22 are pressure air supply pipes.

Therefore, the changeover switch 23 is set to the second position during automatic operation.
Turn it to the automatic side as shown in the figure. Then, the temperature sensor 5 outputs an output according to the temperature, and a part of this output enters the temperature correction circuit 27, which calculates the difference necessary for temperature correction based on the temperature, for example, if it is 20°C or higher. The negative output is corrected so as to output a positive output if the temperature is below 20°C, and this output and an output corresponding to the specific gravity of the specific gravity sensor 4 are output to the differential amplifier 28 so as to be converted to 20°C.

The output of the differential amplifier 28 is compared with the upper and lower limit set values of the upper and lower limit setter 17 in the upper and lower limit specific gravity determination circuit 18 in terms of specific gravity values.

When the specific gravity value is high or low, an output is output from the upper and lower limit specific gravity determination circuit 18 to the solenoid valve control circuit 19, which controls the solenoid valve 9 or 10 to supply pressurized air A from the pressurized air source 20. Outputs the output to be supplied to the pipes 21 and 22, and pressurized air A
is supplied to a stock solution tank 12 containing a flux stock solution 24 or a dilution solution tank 13 containing a dilution solution 25.

Therefore, the stock solution tank 12 or diluted solution tank 13 is removed by an amount proportional to the time that the solenoid valve 9 or 10 is open.
The stock solution 24 or diluted solution 25 is added to the flux tank 2.
is supplied to maintain the specific gravity of flux 3 within a predetermined range.

Incidentally, when the liquid level sensor 6 outputs the upper limit liquid level of the flux 3, the solenoid valve 9 or 10 is immediately closed. Also, when the liquid level sensor 6 outputs the lower limit liquid level of the flux 3, the stock solution 24 or the diluted liquid 25 is pumped into the flux tank 2 while keeping the specific gravity within a predetermined range until the liquid level outputs the upper limit value, which is the upper limit liquid level. supply to.

The conventional flux coating devices 1 and 1' described above are as follows:
Flux 3 can always be maintained at a certain level of specific gravity.

However, as mentioned above, in the conventional flux coating devices 1 and 1', the measured specific gravity value signal is simply corrected to a predetermined temperature value, and the flux 3 actually used is adjusted to a predetermined temperature. Since it was not repaired, flux 3 with an accurate concentration (specific gravity) could not be obtained, so there was a drawback that highly accurate soldering could not be performed.

In other words, although the temperature of the flux 3 has a great influence on the defect rate, which represents the percentage of soldering that is good or bad, the conventional flux applicators 1 and 1' hardly take into consideration measures for constant temperature control of the flux 3. The current situation is that this has not been done.

More specifically, since flux contains alcohol, its concentration (specific gravity) changes greatly with changes in temperature, and therefore it is not possible to perform soldering with high accuracy simply by correcting the temperature.

Regarding the flux applicators 1 and 1' shown in FIGS. 1 and 2, although not shown, as shown in FIG. It is equipped with a flux jet device for forming the flux into a foam, guiding it upward through a foam tube cover 30, flattening it through a foam nozzle 31, and applying the flux to an object to be soldered such as a printed wiring board to be soldered. ing.

Another conventional flux coating device 1'' is disclosed in Japanese Patent Application Laid-open No. 72755/1983.

This flux coating device 1'' will be explained below with reference to FIG.

This flux applicator 1'' has a temperature sensor 5 such as a thermocouple or thermistor placed in a flux tank 2, and a signal from this temperature sensor 5 is applied to a temperature control device, and a set temperature value signal from a temperature setting device 33 is input. The signal from the temperature sensor 5 is compared and the heat exchange device 34 is operated to raise or lower the temperature of the flux 3 in the flux tank 2 so that the flux 3 reaches a predetermined temperature.
Incidentally, in FIG. 3, reference numeral 32 indicates a temperature control device.

This flux applicator 1'' applies flux 3
It is certainly useful in that it keeps the temperature of the object constant.

For this reason, although it has been put into practical use, this flux applicator 1'' merely keeps the temperature of flux 3 constant, and does not measure the actual specific gravity of flux 3. Since the concentration value cannot be maintained, high precision soldering cannot be expected.For example, when using the flux applicator 1'', the temperature control circuit 33
Even if the power is turned on and the temperature sensor 5 is activated, or the heat exchange device 34 is activated based on the signal from the temperature sensor 5, the completely cold flux 3 is instantly raised to a predetermined temperature. Therefore, the response operation was very poor, and the flux 3 could not be used for a long time until it reached a predetermined temperature value.

Furthermore, if the temperature of the flux 3 is changing and, for example, the specific gravity of the flux 3 is corrected or the liquid level is controlled by supplying a flux undiluted solution or a diluted solution into the flux tank 2, the temperature of the flux 3 will change. However, it takes a long time for Flux 3 to reach the predetermined temperature value, and during that time Flux 3, which has a specific gravity value that is significantly deviated, must be used, making it difficult to perform high-precision soldering. There is a drawback that it cannot be done.

Furthermore, according to the flux applicator 1'', the temperature of the flux 3 is simply kept constant, but the actual specific gravity of the flux 3 is not measured. There is a drawback that it cannot be maintained at the correct specific gravity value, and since the temperature of flux 3 at that time is not corrected, there is also a drawback that it cannot be corrected to the correct specific gravity value of flux 3, and accurate and high precision soldering cannot be expected. Ta.

The reason why the flux applicator 1'' has these drawbacks is that the flux 3 contains an alcohol-based diluent, and when this flux 3 is warmed by a heat exchanger, the alcohol in the flux 3 evaporates and the flux This is because the specific gravity value of No. 3 varies greatly.

In addition, since Flux 3 uses an alcohol-based diluted liquid, it absorbs and mixes moisture in the atmosphere, causing its specific gravity to fluctuate greatly, and actually warming Flux 3 with water mixed in. This method has the disadvantage that it is not possible to maintain a desired temperature to keep the specific gravity of the flux 3 constant, and that it is not possible to maintain the specific gravity of the flux 3 at a constant value. In addition, when impurities are mixed into the flux 3, the specific gravity value of the flux 3 fluctuates, but in the case of the flux coating device 1'', these drawbacks cannot be addressed, and as a result, the flux 3 is kept at a constant specific gravity. There was a drawback that it was not possible to maintain the same value and that accurate soldering could not be expected.

(Purpose of the present invention) The present invention has been made in order to solve the drawbacks and problems of the above-mentioned prior art. , 1', the specific gravity of the flux 3 is detected using the specific gravity sensor 4, and the detected specific gravity value signal is immersed in the flux 3 and temperature-corrected by the temperature signal from the temperature sensor 5. As in the above-mentioned flux coating device 1'', the temperature of the flux 3 is detected using the temperature sensor 5, and the operation of the heat exchange device 34 is controlled based on the detected temperature signal of the flux 3 to simply maintain the flux 3 at a constant level. There is a known method of managing flux 3 to a predetermined specific gravity value simply by maintaining the temperature, and by simply using one of the above methods, flux 3 could be managed to a predetermined specific gravity value. However, as a result of pursuing these methods, it was found that due to the various drawbacks mentioned above, it was not possible to control flux 3 to an accurate specific gravity value, and as a result, accurate soldering could not be performed. There was found.

Here, the present invention organically combines the above conventional methods to compensate for the drawbacks of each of the above two methods, and also provides a flux coating device that produces a completely new and different effect. Flux application that allows the flux to be set to a constant specific gravity value with high accuracy at all times, even after the power is turned on and during flux application, making it possible to perform extremely accurate soldering. This was done for the purpose of providing equipment.

(Means for Achieving the Purpose of the Invention) The object of the present invention is to provide a means for detecting the specific gravity in a flux tank storing a flux consisting of a diluent and a flux stock solution, and to detect the specific gravity of the flux obtained by the above-mentioned specific gravity detecting means. A means for correcting the specific gravity value to a specific gravity value at a set temperature is provided, a constant temperature control device is provided for raising the flux to the set temperature, a means for detecting the temperature of the flux is provided, and a This can be achieved by providing means for correcting the flux to a specific gravity value at a set temperature based on a signal, and a flux management device that operates a constant temperature controller to maintain the flux at a constant specific gravity value.

(Example) An example of the present invention will be described with reference to FIG. 4 and the following drawings.

In the flux applicator 1 of the present invention, the flux tank 2' storing the flux 3 and the flux applying section 35 may be integrated, but in order to make it more convenient, the flux tank 2' storing the flux 3 An example in which the flux application section 35 and the flux application section 35 are separated will be described as an example.

The flux tank 2' is connected to the stock solution tank 12 and the diluted solution tank 13 via a supply pipe 38 which is provided with a flux stock solution supply pump 36 and a diluent supply pump 37 in the middle.
It is connected to the.

The pumps 37 and 38 are driven and controlled by signals from a control circuit 39, and pump the flux undiluted solution 24 in the undiluted solution tank 12 and/or the diluted liquid 25 in the diluted solution tank 13.
is supplied into the flux tank 2' through the supply pipe 38, and the liquid level and specific gravity of the flux 3 in the flux tank 2' are kept constant.

A bob 41 connected to the specific gravity sensor 4 via the transmission line 40 is immersed in the flux 3 of the flux tank 2'.

In addition, the flux 3 in the flux tank 2' is
The above-described liquid level sensor 6 for detecting the liquid level of the flux 3 has an electrode portion 6A at its tip immersed.

Furthermore, the flux 3 in the flux tank 2'
A temperature sensor 5 for detecting the temperature is immersed in the flux 3.

The flux tank 2' may be installed in an automatic soldering device or removed from the automatic soldering device, but in the embodiment of the present invention, in order to make the automatic soldering device compact, the flux tank 2' is It is assumed that the flux application section 35 is installed at a position removed from the soldering device, and only the flux application section 35 is installed in the automatic soldering device.

The flux tank 2' is connected to a foaming nozzle 46 through a flux supply pipe 44 having a flux supply pump 42 and an electromagnetic valve 43 disposed in the middle thereof, and a supply pipe 45 connected to the flux supply pipe 44.

The foaming nozzle 46 has an opening 47 at its upper end, a flux storage cavity 48 for storing a small amount of flux 3 inside, and a flux storage cavity 48 at the bottom of the cavity 48 for turning the flux 3 into a foam. A foam cylinder 49 is provided.

This foam tube 49 is connected to an air pump 51 via an air supply pipe 50.

Therefore, when the air pump 51 is driven, air passes through the air supply pipe 50 and air is generated from the foaming tube 49, so that the foamed air-like flux 52 made into a foam by the foaming tube 49 is foamed. It is ejected from the upper part of the opening 47 of the nozzle 46 and applied to the object to be soldered.

The foaming nozzle 46 is provided with a temperature sensor 53 for detecting the temperature of the flux 3 inside the foaming nozzle 46, that is, inside the cavity 48.

This temperature sensor 53 can detect the temperature of the flux 3 in the foaming nozzle 46 just before it is applied to the object to be soldered.
By driving and controlling a constant temperature controller 54 of the flux 3 (to be described later) based on a signal from the foaming nozzle 3 by the control circuit 39, the temperature inside the foaming nozzle 46 can be set to the set temperature.

That is, since the foamed air-like flux 52 has a set temperature, it is possible to apply the flux 3 at an accurate concentration to the object to be soldered, thereby facilitating accurate soldering.

Note that the foaming nozzle 46 also needs to contain the flux 3 so that the liquid level is always constant, so the foaming nozzle 46 is equipped with a liquid level sensor 5.
5 is provided. The signal from the liquid level sensor 55 is input to the control circuit 39, and the flux supply pump 42 and the electromagnetic valve 43 are controlled to drive and control the flux 3 in the flux tank 2° until the liquid level of the flux 3 in the foaming nozzle 46 becomes constant. is supplied to the foaming nozzle 46. Foaming nozzle 46
is surrounded by a heat insulating cover 56.

Inside the constant temperature temperature controller 54, the supply pipe 4
A heater 56 for heating the flux 3 from the outside is wound around the outer circumference of the flux 3, as shown in FIG.

The reason for this is that since the flux 3 is an organic solvent, it is dangerous to heat the flux 3 directly within the foaming nozzle 46.

Further, the end of a cooling pipe 58 connected to a cooler 57 is wound around the outer periphery of the supply pipe 45 as shown in FIG. 5, so that the flux 3 is cooled from the outside of the supply pipe 45. .

FIG. 6 shows the main system block diagram of the present invention.

The signal from the liquid level sensor 55 is input to the liquid level up/down determination circuit 59, and the flux supply circuit 60 operates the flux supply pump 4 until the flux 3 in the foaming nozzle 46 reaches a certain level.
2 and the electromagnetic valve 43 to supply the flux 3 in the flux tank 2' to the foaming nozzle 46 through the flux supply pipe 44 and the supply pipe 45.

When the drive switch 61 is turned on when the flux applicator 1 is in use, the air pump drive circuit 62 causes air to flow through the air supply pipe 50 and the foam tube 49, and the foamed air-like flux 52 is ejected from the opening 47, and the soldered object is heated. is applied to.

Based on the output signal from the temperature sensor 53, the temperature determination circuit 67 controls the operation of the constant temperature temperature control device 54.

The specific gravity value signal from the specific gravity sensor 4 is input to the specific gravity determination circuit 63 and then sent to the specific gravity temperature correction circuit 64.
The specific gravity signal is corrected to match the temperature signal inputted to the temperature determining circuit 65 and converted to the set temperature. Note that the signal from the specific gravity sensor 4 is input to the specific gravity determination circuit 63.

In order to maintain the flux 3 in the flux tank 2' at a predetermined specific gravity value, the stock solution supply pump 36 or the diluent supply pump 37 is driven by a signal from the correction circuit 64, and an appropriate amount of the stock solution in the stock solution tank 12 is pumped. 24 or the diluent 25 in the diluent tank 13 is supplied into the flux tank 2' via the supply pipe 38.

The signal from the liquid level sensor 6 is sent to the liquid level judgment circuit 6.
6 and pump 36 or 3 until the flux 3 in the flux tank 2' reaches a certain level.
7 to drive flux 3 into flux tank 2'.
supply.

(Effects of the present invention) As described above, the present invention performs constant temperature control of the flux and also measures the specific gravity of the flux, and further corrects the specific gravity value at the temperature value at that time. Since the flux can be set to an accurate concentration, it is possible to ensure more accurate soldering than conventional flux applicators, which is a great practical effect.

That is, according to the present invention, a means for detecting the temperature of the flux is provided, and a means for correcting the flux to a specific gravity value at a set temperature and a constant temperature control device are operated based on a signal from the temperature detecting means. Since the flux is kept at a constant specific gravity value, when using the flux applicator, when operating the constant temperature control device to maintain the flux at a constant specific gravity value, the flux is kept at a constant temperature value. Even if the flux decreases and the flux undiluted solution or diluted solution is supplied, and the temperature changes and the specific gravity value fluctuates, the specific gravity value of the flux detected by the specific gravity sensor can be read from the temperature sensor. Since the specific gravity value is temperature-corrected using the signal, the flux can be controlled to a predetermined specific gravity value with relatively good accuracy, and good soldering can be performed.

In addition, in order to set the flux to a desired specific gravity value, a constant temperature controller is operated and controlled based on the signal from the temperature sensor to raise and lower the temperature of the flux, thereby maintaining the flux at a predetermined temperature value. Therefore, the flux can be set and managed to a desired specific gravity value, and therefore, flux with an extremely accurate specific gravity value can be ensured, and extremely accurate soldering can be expected.

Even if the constant temperature control device is controlled to maintain the flux at a predetermined temperature value, alcohol evaporation, water contamination, and impurity contamination may occur in the flux, as described above. Even if the specific gravity value or temperature changes, the specific gravity value of the flux at that time is detected by the specific gravity sensor, and the temperature value of the flux is detected by the temperature sensor. Since the specific gravity value signal can be temperature-corrected and the flux specific gravity value can be managed accurately with few errors, it is possible to perform soldering with high precision.

Moreover, in this case, it is possible to control the constant temperature controller to maintain the flux at the optimum temperature by taking into consideration the measured specific gravity value signal of the flux. This makes it possible to maintain high precision soldering.

Furthermore, if the flux tank and flux application section are separated, for example, only the flux application section is installed in the automatic soldering device, and the flux tank is removed from the automatic soldering device, the automatic soldering device can be made very compact. .

Further, by separating as described above, the flux applying section can be made very small, so that a constant temperature control device for controlling the temperature of the flux in the foaming nozzle can be formed in a small size and at low cost.

In this example, the flux is heated and cooled from outside the supply pipe that supplies the flux to the foaming nozzle 46, but it is also possible to heat and cool the flux from outside the foaming nozzle 46 containing the flux. good.

In any case, by separating as described above, the constant temperature control device can be formed in a small size and at low cost.

Although the above embodiment shows the case where two temperature sensors 5 and 53 are used, it is also possible to use only one of the temperature sensors. For example, the temperature sensor 53 may be omitted and the temperature sensor 5 may be shared. In this case, the signal from the temperature sensor 5 may be output to the temperature determination circuits 65 and 67. However, in the example, an example was shown in which the flux application part was separated from the flux tank, so in such a case, knowing the temperature information of the flux immediately before foaming allows setting the flux to a desired specific gravity value, Temperature sensors 5 and 53 are used as described above.
It is desirable to output signals from the temperature determination circuits 65 and 67 to the temperature determination circuits 65 and 67. Therefore, the temperature sensor 53 is very useful when provided inside the foaming nozzle. Especially if you do it this way,
Since the flux in the foaming nozzle can be maintained at a desired temperature at all times, the flux can be kept at an accurate concentration, allowing for highly accurate soldering.

[Brief explanation of the drawing]

FIGS. 1 to 3 are explanatory diagrams of flux coating apparatuses shown as different examples of conventional ones, FIG. 4 is an explanatory diagram of the flux coating apparatus of the present invention, and FIG. 5 is a constant temperature control device of the same flux coating apparatus. FIG. 6 is an explanatory diagram of the control system of the flux coating device. Explanation of symbols: 1, 1', 1'', 1...flux coating device, 2, 2'...flux tank, 3...
Flux, 4... Specific gravity sensor, 5... Temperature sensor, 6... Liquid level sensor, 7... Life sensor, 8... Control circuit, 9, 10... Solenoid valve, 1
1... Pump, 12... Stock solution tank, 13... Diluted liquid tank, 14, 15... Supply pipe, 16... Digital panel meter, 17... Upper and lower limit specific gravity setting device, 18... Upper and lower limit specific gravity Judgment circuit, 19... Solenoid valve control circuit, 20... Pressure air source, 21, 2
2... Pressure air supply pipe, 23... Selector switch, 24... Flux stock solution, 25... Diluent, 26... Air source, 27... Temperature correction circuit, 2
8... Differential amplifier, 29... Foam tube, 30... Foam tube cover, 31... Foaming nozzle, 32... Temperature control device, 33... Temperature setting device, 34... Heat exchange device, 35... Flux application section, 36... Flux stock solution supply pump, 37... Diluent supply pump, 38... Supply pipe, 39... Control circuit, 4
0... Transmission line, 41... Bob, 42... Flux supply pump, 43... Solenoid valve, 44... Flux supply pipe, 45... Supply pipe, 46... Foaming nozzle, 47... Opening, 48... ...Flux storage cavity, 49... Foam tube, 50... Air supply pipe, 51... Air pump, 52... Foamed air-like flux, 53... Temperature sensor, 54...
Constant temperature temperature controller, 55...Liquid level sensor, 56...
Heater, 57... Cooler, 58... Cooling pipe, 59... Liquid level up/down determination circuit, 60... Flux supply circuit, 61... Drive switch, 62...
Air pump drive circuit, 63...specific gravity determination circuit,
64... Specific gravity temperature correction circuit, 65... Temperature judgment circuit, 66... Liquid level judgment circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A means for detecting the specific gravity in a flux tank storing a flux consisting of a diluent and a flux undiluted solution is provided, and the specific gravity value of the flux obtained by the above specific gravity detecting means is A means for correcting the specific gravity value at a set temperature is provided, a constant temperature control device is provided for raising the flux to the set temperature, a means is provided for detecting the temperature of the flux, and based on a signal from the temperature detecting means. 1. A flux coating device, characterized in that said flux is maintained at a constant specific gravity value by operating means for correcting said flux to a specific gravity value at a set temperature and a constant temperature control device. (2) The above-mentioned constant temperature temperature control device is located at a position where it can raise and lower the temperature of the flux in a foaming nozzle that foams the flux, as stated in claim (1) of the utility model registration claim. flux coating equipment. (3) The means for detecting the temperature of the flux consists of a first temperature sensor immersed in the flux in the flux tank and a second temperature sensor immersed in the flux in the foaming nozzle for foaming the flux, The means for correcting the specific gravity value of the flux in the flux tank to the specific gravity value at the set temperature is operated based on the signal from the first temperature sensor, and the flux in the foaming nozzle is operated based on the signal from the second temperature sensor. The flux coating device according to claim (2) of the registered utility model, characterized in that the flux coating device operates a constant temperature control device that raises and lowers the flux to a set temperature.