ES2327702A1 - System of automatic regulation of the anodic current in a galvanic bath. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Automatic regulation system of the anodic current in a galvanic bath, comprising means of control and automatic regulation of the signal that is provided to the bath, in such a way that in a control loop and following a pre-established pattern, the current is adjusted and tension of the bath in function of the surface of the piece subjected to said bath. (Machine-translation by Google Translate, not legally binding)

Description

Automatic current regulation system Anodic in a galvanic bath.

Object of the invention

The object of the present invention is a new system for automatic regulation of anodic current in a galvanic bath, so that the influence of the Operator in the initialization of the process. They are objects of the present invention automatic regulation of the current to from the active cathode surface.

This invention is of special application in any process that requires the use of galvanic baths.

Background of the invention

In a galvanic bath, the current flows between anode and cathode, applying a metallic deposition on the surface of the cathode, which is proportional to said current.

The thickness of the material deposited in the cathode, it depends directly on the anodic current, the time of application and deposition factor of the electrolytic bath, influencing the cathode surface inversely on it.

For example, we will have to:

G = \ frac {A \ text {*} T \ text {*} F} {S}

Where G is the thickness in microns, To the current in amps, T the time in minutes, S the cathode surface in square decimeters, and F the deposition factor defined by:

F = \ frac {A} {S} * G * T

Looking at the elements of the formula, it is possible to appreciate the following points:

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Is known the desired thickness.

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Is possible control of the current to be applied.

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Is possible control of the application time of the stream.

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Is known the deposition factor of the bathroom.

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Is difficult to know the cathode surface, and therefore its measurement is complicated

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Without him exact knowledge of the cathode surface, it is impossible Know the amount of microns we are depositing.

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In conventional galvanic baths, the regulation occurs manually, or assisted by computer, but always with the data provided by the operator. The curve Initialization of current is done manually, according to the constants more or less established by an experience acquired. There are rectifiers that stabilize the current, this is good to keep it constant, but the regulation has to follow being done manually. These rectifiers are used to have the option of stabilizing the bath voltage, but not compensate for the falls that the connections between them can suffer and bathroom.

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So, the main drawbacks that present the systems currently used are summarized in:

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Need for regulation of the current from erroneous surface data of the cathode.

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Still in the case of knowing the current that is necessary to apply, is necessary to give a lower current and start without knowing exactly which current is correct. It is a common practice using a criterion of use of half or a third of the rated current, depending on the materials, the state of the cathode or the Operator criteria, for an approximate time and between 5 and 10 minutes.

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He production success simply depends on the proper functioning of the equipment and its calibration.

Description of the invention

To alleviate the problems mentioned above, it presents the automatic current regulation system anodic in a galvanic bath, object of the present patent of invention.

First, it must be taken into account that there are two important factors in a galvanic bath, which are the Anodic current and voltage between anode and cathode. Between these factors there is a relationship that can vary if they are not constant The following factors:

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Bath conductivity, constant, although it may vary after several days of work.

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Bathroom volume, is constant.

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Distance between anode and cathode, is constant.

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Anode surface, is constant, but tends to decrease slightly by the contribution of material to cathode, which may vary after a few days of job.

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Bath shaking, which can be keep uniform.

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Surface of the cathode, varies constantly, because they are the different pieces that we are going through the bathroom to galvanize them. In addition each of them is different from the others, and it is not possible to calculate its surface.

Thus, for example, in a copper bath intended To add this metal on printed circuits we have to:

1.- Five copper plates with different sizes, with different surfaces: 2 dm 2, 4 dm 2, 6 dm 2, 12 dm 2, 18 dm 2.

2.- An essay is carried out on each of them, applying an anodic current of 1 amp for each dm 2 of surface after applying an upward curve of current to allow time to fully activate the copper of the cathode, finally measuring in each one the value of the tension between anode and cathode, as can be seen in the following table:

one

It is observed during the trial that, when changing the plate without varying the voltage, increases or decreases the current in function of the surface of said plate, but never reaches the value correct that it would have to arrive. So, when the surface is lower, the current does not lower enough, while when the current is higher, the necessary does not rise. Is therefore deductible that the galvanic bath does not have a pure resistive behavior.

But since for the same tension between anode and cathode the surface of the cathode influences in a direct way and proportional to the anodic current applied is possible preparation of a pattern of behavior for oneself test conditions. Thus it will be possible to deposit plates of unknown surface, simply varying the tension of the bathroom until the current and voltage values correspond with those of the employer or reference.

The calibration procedure is simple, since that two different calibration cathodes will be available, one with a surface approximated to the minimum piece with which we have to work in the bathroom and another with the maximum area that can be perform, so that current measurements are taken and voltage in each case, drawing a calibration curve that covers The whole range of work. It is clear that the tensions that remain between the two calibration voltages, will coincide with the calibration curve for controlled deposition.

The system where the regulation is implemented is an electronic circuit that, by means of test probes connected to the anodes and to the same cathode, controls the tension in the bathroom at all times, and also controls in parallel the voltage of a shunt , where it passes the current consumed by the bathroom. With these data, plus the reference provided by the defined calibration curve, it is able to regulate the bath voltage.

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It is achieved through this regulation a optimization of the deposition relationship - giving more time profitability to the process and better quality because there is no rejection possible parts that have received more deposition than they could assimilate. Other advantages over the current state of the art They are:

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It is not It is necessary to know the cathode surface.

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All The pieces have an identical finish.

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We eliminate possibility of rejection.

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Deposition of the maximum material in the minimum possible time, because this technology is based on taking advantage of the active cathode deposition capacity at all times.

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It is equally remarkable that, if there is any problem in the bathroom, such as lack of agitation or sudden increase in conductivity, with a conventional system, would cause passivation and precipitation of deposition. With this new system, and being applied by a system like the one described here invention patent, which regulates the tension according to the load admissible by the cathode, this system would detect the onset of passivated, since the intensity falls slightly, no corresponding to the tension of the bath, going down automatically the tension of the bathroom and looking for a new point of balance corresponding to the calibration curve, before which the part He would never passivate and / or rush.

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Brief description of the figures

They are described very briefly below. a series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention presented as an illustrative example but not limiting it.

In figure 1 a plane can be observed schematic of the automatic current regulation system Anodic in a galvanic bath.

An electrical scheme is shown in Figure 2 of a preferred embodiment of the control means of the galvanic regulation.

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Preferred Embodiment of the Invention

As it is possible to observe in figure 1 the automatic regulation system of anodic current in a bath Galvanic, object of the present invention, comprises at least:

media drives (1),

means of voltage transformers (2),

a plurality of silicon rectifying means (3),

shunt means (4),

means of electronic regulation and control 5,

means of engine control 6,

a motor reducer 7,

measuring means of current 8,

a plurality of anodes 9, comprising

a plurality of baskets 13, and

a plurality of connection terminals 16,

a cathode 10, understanding

a rack 14,

some tweezers connection 15,

a Cuba galvanic 11,

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The power supply is connected to the drive 1, and from there to the transformer 2. The output of the transformer is connected to shunt 4 and rectifiers 3. The current in shunt 4 is measured by ammeter 8.

The current flowing through the rectifiers 3 feeds the anodes 9. Another terminal of shunt 4 is connected to the cathode 10.

The following are available to the control means 5 signals:

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signal of test cathode 15,

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signal of anode 9,

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signal shunt 4, cathode 10

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signal shunt 4 of transformer 2,

The control means 5 are connected to the motor control, and from there to the drive, closing the loop of control.

Figure 2 shows an embodiment of the control means 5, based on an electronic circuit with three different feeds, two of them with different potential even between masses and that exactly correspond to the shot Shunt negative and with cathode 10.

The masses 21 and 22, which are those of different potential, are fed by two stabilized sources and totally independent, this being so that they do not interfere the signals measured in the bathroom with the measurements in shunt 4. The mass number 23 feeds the maneuver circuits and their optocouplers; this mass has a stabilized source with independent regulator

Bath current measurement

The first important point is the measurement of bath current, comprising adjustment means of scale 100. Right at the shunt outlet, we have an adjustable potentiometer multiturn final adjustment scale 101, where for a maximum value of shunt, preferably 100 mV, we will obtain a maximum value of output, preferably 7 V. To the other end of this potentiometer adjustable, we have a resistance to mass and the output of a operational that gives the bias voltage to the amplifier of the shunt signal through this adjustment potentiometer, for the current value 0 in the bathroom, in this case by means of the multiturn potentiometer adjustment start scale 102 we will adjust to have an appropriate reading at the optocoupler output, preferably 1 V.

As the signal from the shunt is pulsating continuous since the rectified current is not filtered, it has disposed at the entrance of the operational a type filter low-pass for possible interference from high frequencies Also at the output of the amplifier, it has arranged a similar filter in counter-reaction connecting it to the negative input of the operational.

Note that to make these adjustments there is a resistance, which comes from positive eating, which raises the voltage at the shunt voltage input points in how much this one is disconnected. With a calibration plate based on Adjustable potentiometers resistors and switches, we can regulate Easily desired stresses to calibrate. In this way, in the output has a voltage value indicative of the current flowing through the bathroom.

Bath voltage measurement

Bathing voltage measurement comprises means of adjustment of curve 200, at its maximum 201 and minimum 202. The cathode is connected to ground 22 and on the other hand right at the anode we take the connection that enters the curve adjustment means maximum, this must be left midway since it is one of the adjustments to be made periodically and from the outside the device, as was the case with the amplifier to bath current measurement, we can see that at the other end of this potentiometer there is a resistance to ground and the output of a operational amplifier that provides us with the voltage of polarization for the minimum working voltage signals of the bath, this is adjusted with a multiturn potentiometer adjusting minimum curve, this is also left midway as it is the another adjustment that must be made periodically and, therefore, It will also be done from the outside.

It can be seen that they also have low pass filters at the entrance of the amplifier and in the counter-reaction output, already that the tension in the bathroom is also pulsating and continuous. Observe yourself that at the output of the amplifier, using a potentiometer multiturn, we can adjust the gain of the amplifier, that is, the maximum working point is adjusted.

We can observe that at the voltage input coming from the bathroom, there is a resistance coming from feeding. At this point, proceed as described in the current, disconnecting the signal from the bathroom and connecting a board  Calibration with adjustable resistors and switches. We will look in the bath which tension is between anode and cathode putting the maximum cathode surface and making the bathroom work with the corresponding current for the surface of said cathode; is tension we will adjust it on the calibration plate and then we will adjust the amplifier gain so that at the output of the Optocoupler let's have an appropriate reading. Then we have to go to the opposite, see what tension is the minimum of the bathroom to deposit on a tiny surface, and the correct current for its surface. We adjust this tension on the plate calibration and we set the preset potentiometer to that gives us a voltage value at the optocoupler output appropriate. These adjustments also influence each other. One time Once the adjustments are made, the adjusted equipment is arranged. So, in the optocouplers output, the calibrated signal is available, preferably between 1 and 7 volts for the scale. And on the way out, the bath voltage signal, preferably calibrated between 1 and 7 volts for the voltage scale.

It only remains to send these two signals to a comparator 300 and this according to the signals will give a positive signal by one exit or the other, but in the case that the signals are exact within a range between +3 millivolts and -3 millivolts, will give a positive signal at the two outputs, in this one case will mean that the current applied to the bathroom is correct for the tension existing in said bath. Now these departures from comparator go to the power control board, which in the case of This device is a motor control board with which we move the drive that feeds the power part.

Note that at the output of the optocoupler, there is a resistor that carries the signal to comparator 300, and just there we found a zéner diode to ground, this is to stop the signal upon reaching the bottom scale of the current and that way protect the device and the piece put in the bathroom, since the controller at the end of scale runs the risk of being out of control in the case that we put a piece that by its size the regulator had to send administer a current by above the bottom of the device regulation scale.

The reference signal amplifiers of the voltage and current applied in the bathroom, have the point of saturation measured at the output of the optocouplers above the 8 volts, if the signals reach these values, could cause two very different things, or the descent of ancestry of current because the reference voltage of the current, or on the contrary the rise of the current to reach the upper limit switch of the drive, for having saturated before the reference signal corresponding to the ' tension. In the first case we would be depositing in the piece less material, but we would not spoil it, while in the second In case we burn the piece by an excessive current. To remove the possibility of the current rising uncontrollably in the if the end of scale is exceeded, the zerner diode has been arranged previously commented on the optocoupler output corresponding to the reference voltage of the current, of such so that, when the full scale is reached, a brake that ensures saturation voltage at this point of measurement, which is the input to the comparator, is always less than the saturation voltage referring to the bath voltage.

When the full scale current arrives, the controller will forcefully stop the power surge, whatever be the surface of the cathode; in this case we simply have to know that when the device is working at full scale, it is not reliable and we would have to lower the cathode surface.

The plate that feeds and controls the engine, It comprises two complementary stages with 2 type transistors Darlington class C, which feed each motor pole. These stages are fed through a transistor, by which you can vary the supply voltage using a potentiometer connected to its base and thus adjust the motor speed. Each stage is connected to a different output of the comparator 300, when the current is correct, comparator 300 will give the two positive signals and the outputs of the two stages will be in phase, therefore the motor will not move, but when the current is not correct, comparator 300 will only test positive at the output corresponding, as you have to increase or decrease the current. By consequently, the stages that feed the motor will be in the phase corresponding so that the motor turns to the right side. He drive has 2 limit switches, one at the upper limit and the another at a point higher than the zero limit, so that in this way the bath receive a voltage slightly lower than the minimum of work, corresponding to the minimum surface, being able to of this form the control circuit detect the increase in current at put a plate in the bathroom and start the regulation, since in At rest, the drive is always at this lower limit. Observe yourself that the resistance that carries positive voltage to the input that measures the anode voltage causes the voltage to rise at this input of test when disconnecting the cathode to remove the plate, since the circuit is open and therefore considerably increases its impedance, being on the other hand the tension of the shunt O. consequently, comparator 300 gives the order to lower the voltage of the bath until you reach the end of the drive.

Claims (10)

1. Automatic regulation system for anodic current in a galvanic bath characterized in that it comprises at least

a variator one,

a motor reducer 7,

means of electronic regulation and control 5,

means of control 6 of the reduction motor 7,

a shunt 4,

a plurality of anodes 9, comprising

a plurality of baskets 13, and

a plurality of connection terminals (16),

a cathode 10, understanding

a rack 14,

some tweezers connection 15,

a Cuba galvanic 11,

where drive 1 and gear motor 7 control the power delivered to the galvanic bath, and where electronic control and control means 5 in turn control the reduction motor 7, through the control means 6 of the motor reducer; and where the means of regulation and control 5 compare the signals of anodes 9, positive and negative of shunt 4 and cathode 10, to provide an output according to the pattern of reference; and because all the elements form a loop closed control. 2. Automatic regulation system of the anodic current in a galvanic bath, according to claim one, characterized in that the electronic control and regulation means 5 comprise at least: Measuring means of bath current, comprising, at least, means of adjusting the scale (100), in its maximum and minimum, which in turn include:

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media of start of scale adjustment, comprising an amplifier and a adjustable multiturn potentiometer (102) to obtain an output appropriate for the zero value of the current; Y

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media end-of-scale adjustment, comprising an amplifier and a adjustable multiturn potentiometer (101) to obtain a value maximum output for a maximum value of shunt 4;

measuring means of bath voltage, comprising at least, means for adjusting the curve (200) of tension, at its maximum and minimum, which in turn include:

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media minimum curve adjustment, comprising an amplifier and a adjustable multiturn potentiometer (202) to obtain an output appropriate for the minimum value of the bath voltage; Y

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media of maximum curve adjustment, comprising an amplifier and a adjustable multiturn potentiometer (201) to obtain a value maximum output for a maximum bath voltage value;

a comparator (300) in charge of comparing the measured bath voltage and measured bath current, where said means (100,200,300) are electrically powered by stabilized sources and independent, so that they do not interfere with each other. 3. Automatic regulation system of the anodic current in a galvanic bath, according to claim 2, characterized in that the appropriate output for the zero value of the current is 1 volt. 4. Automatic regulation system for anodic current in a galvanic bath according to claim 2, characterized in that the maximum shunt value 4 is 100 mV. 5. Automatic regulation system of the anodic current in a galvanic bath, according to claim 2 and 4, characterized in that the output value for the maximum shunt value 4 is 7 V. 6. Automatic regulation system for anodic current in a galvanic bath, according to claim 2, characterized in that the scale adjustment means (100) comprise low-pass filters. 7. Automatic regulation system of the anodic current in a galvanic bath, according to claim 2, characterized in that the appropriate output for the minimum value of the bath voltage is 1 V. 8. Automatic regulation system for anodic current in a galvanic bath, according to claim 2, characterized in that the maximum output value for a maximum bath voltage value is 7 V. 9. Automatic regulation system for anodic current in a galvanic bath, according to claim 2, characterized in that the voltage curve adjustment means (200) comprise low-pass filters. 10. Automatic regulation system for anodic current in a galvanic bath, according to claim 2, characterized in that the inputs to the comparison means are made by means of optocouplers.