JPH0210595B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for applying liquid varnish to a printed circuit board for the purpose of dust prevention, corrosion prevention, migration prevention, and whisker prevention. .

[Background of the invention]

In conventional liquid paint coating methods, the following steps are taken to speed up coating.

That is, the pressure in front of the nozzle is adjusted to a range of 5 to 200 kg/ ^cm2 , and the paint is discharged from the discharge nozzle 1 in a completely atomized state into a wide-angle conical shape 2, as shown in FIG. As shown in FIG. 1B, the ink is discharged from the discharge nozzle 1 in a substantially bell-shaped state 3 in an incompletely atomized state, so as to apply the product over a wide area to an object to be coated (not shown).

However, when the discharge nozzle 1 discharges the paint in the shape shown in FIG. requires masking processing to shield the

Therefore, when applying varnish to a printed circuit board using the above-mentioned conventional technique, it is necessary to mask the areas where coating is prohibited, and depending on the shape and number of areas where coating is prohibited, the coating work performance may be significantly reduced. There was a drawback.

[Purpose of the invention]

An object of the present invention is to provide a printed circuit board that can prevent the occurrence of varnish mist, and therefore allows liquid varnish to be applied to the prohibited areas without masking even if the printed circuit board has areas where application is prohibited. To provide a method for applying liquid varnish to.

[Summary of the invention]

In the method of the present invention, the varnish viscosity is adjusted to 3 to 100 CPS under a temperature condition of 0 to 40°C, the varnish discharge pressure is adjusted to 0.3 to 1.0 Kg/cm ² at the nozzle front pressure, and the nozzle is adjusted based on these values. The feature is that the diameter is adjusted to 0.20 to 0.25φ in terms of the diameter of the area equivalent circle, and the liquid varnish is discharged from the discharge nozzle in the shape of a bamboo leaf and applied to the printed circuit board. As a result, the liquid varnish can be applied to the prohibited areas of the printed circuit board without masking.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

2 and 3 show an embodiment of an apparatus for carrying out the method of the invention.

The liquid varnish coating device shown in these figures includes a varnish tank 4 that stores liquid varnish 5, a pressure pump 7 connected to this through a supply pipe 6, and a cooling/heating device connected to the pressure pump 7 through a supply pipe 6. 8. A flow rate detector 9 provided in the supply pipe 6 between the pressure pump 7 and the cooling/heating device 8; a first and second flow rate detector provided in the supply pipe 6 before and after the cooling/heating device 8;
temperature detectors 10 and 11, a discharge nozzle 12 connected to the cooling/heating device 8 through a supply pipe 6, and a return pipe 1 connecting the discharge nozzle 12 and the varnish tank 4.
Pressure detector 14 installed in 3, same return pipe 1
3, a constant temperature controller 16 that controls the cooling/heating device 8, and a constant pressure maintaining valve 1 provided in the constant pressure maintaining valve 1.
5, a constant pressure controller 18 that controls the pressure pump 7 and the constant pressure maintenance controller 17, and a nozzle opening/closing controller 19 that controls the discharge nozzle 12.

The cooling/heating device 8 and the first and second temperature detectors 1
0 and 11 and the constant temperature controller 16 constitute varnish viscosity control means for adjusting the varnish viscosity of the liquid varnish supplied to the discharge nozzle 12. In this varnish viscosity control means, as shown in FIG. send. Further, the second temperature detector 11 detects the temperature of the liquid varnish discharged from the cooler/heater 8, and sends the temperature signal B to the constant temperature controller 16. Next, as shown in FIG.
and a target value, calculate the control amount necessary for constant temperature control, and further generate a temperature instruction signal (control signal) to be sent to the heater and cooler of the cooler/heater 8. The cooler/heater 8 heats or cools the liquid varnish according to the temperature instruction signal sent from the constant temperature controller 16, and adjusts the viscosity of the liquid varnish to be supplied to the discharge nozzle 12.

The flow rate detector 9, the pressure detector 14, the constant pressure maintenance valve 15, the constant pressure maintenance controller 17, and the constant pressure controller 18 constitute a nozzle front pressure control means for adjusting the nozzle front pressure of the liquid varnish. In this nozzle front pressure control means, as shown in FIG. 2, the flow velocity at the outlet of the pressure pump 7 is detected by the flow velocity detector 9, and the detected flow velocity signal is sent to the constant pressure controller 18. On the other hand, the pressure detector 14 detects the pressure in the discharge nozzle 12 and the return pipe 13 of the constant pressure maintenance valve 15, and sends the pressure signal to the constant pressure controller 18. Next, as shown in FIG. 3, the constant pressure controller 18 calculates the flow rate of liquid varnish entering the discharge nozzle 12 from the flow rate signal and the pressure signal, compares the flow rate with a target value, and converts the comparison result into pressure. Then, the nozzle front pressure is detected from this pressure, the control amount necessary for constant pressure control of this nozzle front pressure is calculated, and the pressure feed amount control signal to be sent to the pressure pump 7 and the constant pressure maintenance controller 17 are sent. A constant pressure maintenance valve opening/closing signal to be sent is generated. The pressure feed pump 7 controls the flow rate of liquid varnish sent to the discharge nozzle 12 based on the pressure feed amount control signal from the constant pressure controller 18, and the constant pressure maintenance controller 17 receives a constant pressure maintenance valve opening/closing signal from the constant pressure controller 18. By controlling the opening/closing amount of the constant pressure maintenance valve 15 and controlling the pressure pump 7 and the constant pressure maintenance valve 15, the nozzle front pressure is adjusted.

As shown in FIG. 3, coordinate information and application information are sent to the nozzle opening/closing controller 19 as a nozzle diameter control means. Here, the coordinate information is information in which either the varnish viscosity or the nozzle front pressure is plotted on the horizontal axis and the other is plotted on the vertical axis, and it also shows the relationship between the varnish viscosity, the nozzle front pressure, and the nozzle diameter. (See Figures 6 to 10). Also,
The application information is information on the actually adjusted varnish viscosity and nozzle front pressure. The nozzle opening/closing controller 19
Then, the coordinate information and coating information are taken in, and then converted into opening/closing information for the discharge nozzle 12. Furthermore, the liquid varnish can be discharged from the discharge nozzle 12 in the shape of a bamboo leaf, the discharge shape is stable, and there is no rebound from the printed circuit board. The nozzle diameter that allows the discharge to be avoided is calculated, a discharge nozzle opening/closing control amount is created based on the calculated nozzle diameter, and the opening/closing signal is sent to the discharge nozzle 12.

Next, an embodiment of the coating method according to the present invention will be described in relation to the operation of the coating device.

The liquid varnish 5 stored in the varnish tank 4 is
It is sucked up by the pressure pump 7 and sent to the cooling/heating device 8 through the supply piping 6.
The varnish viscosity is adjusted by the varnish, and then sent to the discharge nozzle 12.

Meanwhile, the temperature of the liquid varnish before entering the cooling/heating device 8 is detected by the first temperature detector 10, and the temperature signal is sent to the constant temperature controller 16, and the temperature signal is sent to the constant temperature controller 16.
The temperature of the liquid varnish discharged from the cooler/heater 8 is detected by the temperature detector 11 , and the temperature signal is sent to the constant temperature controller 16 . The constant temperature controller 16 generates a temperature instruction signal to control the cooler and heater of the cooler/heater 8 from the temperature signals sent from the first and second temperature detectors 10 and 11, and A temperature instruction signal is sent to the cooler and heater, and the liquid varnish is adjusted to a varnish viscosity of 3 to 100 CPS under the condition of 0 to 40°C by the cooler/heater 8 including the cooler and heater. .

On the other hand, the flow rate of the liquid varnish discharged from the pressure pump 7 is detected by the flow rate detector 9, and the flow rate signal is sent to the constant pressure controller 18. In addition, pressure detector 1
4 detects the pressure of the liquid varnish returned to the varnish tank 4 from the discharge nozzle 12 through the return pipe 13, and the pressure signal is sent to the constant pressure controller 18. In this constant pressure controller 18, the flow rate detector 9
The pressure of the fluid varnish entering the discharge nozzle 12 is calculated from the flow rate signal sent from the pressure sensor 14 and the pressure signal sent from the pressure detector 14, and the pressure feed amount control signal is used to control the discharge flow rate of the pressure pump 7 from this pressure. Then, a constant pressure maintenance valve opening/closing signal for controlling the constant pressure maintenance controller 17 is generated. Next, the pressure feed amount control signal is sent to the pressure pump 7 to control the discharge flow rate of the pressure pump 7, and the constant pressure maintenance valve opening/closing signal is sent to the constant pressure maintenance controller 17, which controls the constant pressure maintenance valve. 15 opening degrees are controlled. By controlling the discharge flow rate of the pressure pump 7 and the opening degree of the constant pressure maintenance valve 5, the nozzle pressure of the discharge nozzle 12 is adjusted to 0.3 to 1.0 kg/cm ² .

Next, the nozzle opening/closing controller 19 receives coordinate information indicating the relationship between varnish viscosity, nozzle front pressure, and nozzle diameter, and coating information that is the actually adjusted value. From the information, a nozzle opening/closing signal is generated to control the nozzle diameter of the discharge nozzle 12 to an appropriate value within the range of 0.2 to 0.25φ in terms of the diameter value of the area equivalent circle. This nozzle opening/closing signal is sent to the discharge nozzle 12, and the nozzle diameter is
It is adjusted to an appropriate value within the range of 0.20 to 0.25φ.

As a result, the varnish is discharged from the discharge nozzle 12 into the fourth
As shown in the figure, it is discharged in the shape of a bamboo leaf, and as shown in FIG. 5, it is discharged to a thin thickness, and is discharged in a stable shape, and furthermore, it is discharged so that it does not bounce off the printed circuit board. In addition, the varnish discharged in FIGS. 4 and 5 is indicated by the reference numeral 20.

Next, FIGS. 6 to 10 show experimental results regarding the relationship between varnish viscosity, nozzle front pressure, and nozzle diameter that can discharge liquid varnish in the shape of a bamboo leaf.

In the experimental results shown in FIGS. 6 to 10, the varnish temperature was 0 to 40 DEG C., and the nozzle diameter was expressed as the diameter of a circle equivalent in area.

The shaded area in Figure 6, varnish viscosity = 10 CPS or less, nozzle front pressure = 0.3
Under the conditions of Kg/ ^cm2 or less and nozzle diameter = 0.20φ or less,
The discharge shape was unstable and inappropriate.

Next, in the shaded area in FIG. 7, that is, under the conditions of varnish viscosity = 3 to 100 CPS, nozzle front pressure = 0.3 to 1.0 Kg/cm ² , and nozzle diameter = 0.20 to 0.25φ, stable discharge is achieved. The shape was obtained, there was no rebound from the printed circuit board, and the discharge condition was proper.

Also, the shaded area in Figure 8, varnish viscosity = 10 to 500 CPS, nozzle front pressure = 1.0
~2.0Kg/cm ² , nozzle diameter = 0.25~0.33φ, the shaded area in Figure 9, varnish viscosity = 20~1300CPS, nozzle front pressure = 2.3~3.0
Kg/cm ² , nozzle diameter = 0.33 to 0.43φ, and the shaded area in Figure 10, that is, varnish viscosity = 30 to 2000 CPS, nozzle front pressure = 3.0 to 4.0
The conditions of Kg/cm ² and nozzle diameter of 0.43 to 0.56φ were unsuitable because the outflow speed of the discharged varnish was too fast, the varnish hit the printed circuit board, and further bounced and scattered.

Next, FIGS. 11 and 12 A, B, and C are
2 shows a situation in which liquid varnish is applied to a printed circuit board by applying the present invention.

In FIG. 11, the varnish 20 is discharged from the discharge nozzle 12 in the shape of a bamboo leaf, and the printed circuit board 21 and the discharge nozzle 12 are moved relative to each other in one direction as shown by the arrows to apply the varnish. .

In addition, FIGS. 12A, B, and C use two discharge nozzles 12a and 12b arranged at a set interval l, and a printed circuit board 2 on which an electronic component 22 is mounted.
1 is placed on the XY table 23. At first, as shown in FIGS. 12A and 12B, the varnish 20b is discharged from the discharge nozzle 12b, and the XY table 23 is moved in the Y ₁ →Y ₂ direction to apply the varnish.
At that time, a first
As shown in FIG. 2B, an unvarnished surface 22' may occur. Next, the XY table 23 is moved in _the X ₁ -> The varnish 20a is discharged from the discharge nozzle 12a, and applied by moving the XY table 23 in the Y ₂ →Y ₁ direction. As a result, the electronic component 22
It is also possible to apply varnish to the uncoated surface 22'.

In the application states shown in FIG. 11 and FIG. 12 A, B, and C, the varnish viscosity = 3 to 100 CPS and the nozzle front pressure = 0.3 to 1.0, as described above.
By adjusting the nozzle diameter to Kg/cm ² and 0.2 to 0.25φ, the varnish can be applied in a stable discharge shape and in an appropriate state without rebounding from the printed circuit board 21. Therefore, varnish can be applied to areas where application is prohibited without performing a masking process to block the varnish discharged as a spray paint.

The varnish viscosity control means, the nozzle front pressure control means, and the nozzle diameter control means are not limited to the embodiments shown in FIGS. 2 and 3, and may be any means having the desired functions.

〔Effect of the invention〕

According to the method of the present invention explained above, the varnish viscosity is adjusted to 3 to 100 CPS under a temperature condition of 0 to 40°C,
Varnish discharge pressure is 0.3 to 1.0 at nozzle front pressure.
Kg/cm ² , and based on these values, adjust the nozzle diameter to 0.20 to 0.25φ in terms of the diameter of the area equivalent circle.
Since the liquid varnish is discharged from the discharge nozzle in the shape of a bamboo leaf and applied to the printed circuit board, the varnish can be discharged from the discharge nozzle in a stable shape and without splashing back from the printed circuit board. This has the effect that varnish can be applied without masking the areas where application is prohibited.

[Brief explanation of drawings]

1A and 1B are explanatory diagrams of the prior art, FIG. 2 is a block diagram showing an embodiment of an apparatus for carrying out the method of the present invention, and FIG. 3 is a block diagram showing details of the controller, Figures 4 and 5 are front and side views of the discharge shape of varnish obtained by the present invention, and Figures 6 to 10 are experiments on the relationship between varnish viscosity, nozzle front pressure, and nozzle diameter, respectively. Figures showing the results, Figures 11 and 12A,
B and C are diagrams showing a state in which varnish is applied to a printed circuit board by applying the present invention. 4... Varnish tank, 5... Liquid varnish, 7... Pressure pump, 8... Cooler/heater, 9... Flow rate detector, 10, 11... First and second temperature detector, 1
2...Discharge nozzle, 14...Pressure detector, 15...
... Constant pressure maintenance valve, 16 ... Constant temperature controller, 17 ... Constant pressure maintenance controller, 18 ... Constant pressure controller, 19 ... Nozzle opening/closing controller, 20 ... Bamboo leaf-shaped discharge varnish, 21 ... Printed circuit Board.

Claims (1)

[Claims] 1 The varnish viscosity is 3 to 3 under the temperature condition of 0 to 40℃.
Adjust the varnish discharge pressure to 0.3~1.0Kg/ ^cm2 at the nozzle front pressure, and adjust the nozzle diameter to 0.20~1.0Kg/cm2 based on these values in terms of the diameter of the area equivalent circle.
A method for applying liquid varnish to a printed circuit board, which comprises adjusting the diameter to 0.25φ, discharging liquid varnish from a discharge nozzle in the shape of a bamboo leaf, and applying the liquid varnish to the printed circuit board.