JPH0312148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to electroless plating, such as electroless Co-P
The present invention relates to a plating start detection device for plating, electroless Co-Ni-P plating, etc., and particularly relates to an electroless plating start detection device suitably used for controlling the film thickness of electroless plating.

Conventional techniques and problems to be solved by the invention Conventionally, in the production of magnetic memories, etc., electroless plating such as electroless Co-P plating and electroless Co-Ni-P plating has been used as a means of providing a magnetic film. However, in such electroless plating, the thickness of the plated film greatly affects the physical properties, so film thickness control is the most important item. especially,
These electroless Co-P plating, electroless Co-Ni-P
When forming an electroless magnetic plating film by plating, etc., the plating film thickness is usually very thin, about 0.1 μm, and the plating time is very short, about 40 to 60 seconds, so it is difficult to control the film thickness. Detecting the start of plating is very important. In other words, film thickness control for plating is normally controlled on-site by plating time, but in this case, after the object to be plated is immersed in the plating solution, it takes several seconds due to the difference in the activity of the plating solution. Alternatively, even if plating starts after more than ten seconds, or even tens of seconds in some cases, the difference in film thickness is less than 0.1 μm compared to when plating starts at the same time as immersion in the plating solution. When the plating film thickness is relatively thick and the plating time is long, the plating time is the time from when the plated object is immersed in the plating liquid until it is lifted out of the plating liquid, that is, the plating time of the plated object. There is almost no error in the plating film thickness when it is considered as the immersion time in the liquid, so there is no need to accurately detect the point at which plating actually starts after the object to be plated is immersed in the plating liquid. By regarding the immersion time in the plating solution as the plating time, the film thickness can be adequately controlled. However, in the case of the electroless magnetic plating film mentioned above, the film thickness is usually about 0.1 μm, and the plating time is
Since it is about 40 to 60 seconds, the time of immersion in the plating solution cannot be considered as the plating time. This is fatal in terms of film thickness control, and therefore the film thickness cannot be controlled by the immersion time in the plating solution, so it is necessary to detect the plating start point and manage the actual plating time from this plating start. The film thickness must be controlled accordingly.

In this case, a possible method for detecting the start of plating is to use a calomel electrode or a silver-silver chloride electrode as a reference electrode (comparative electrode) and measure the potential difference between it and the object to be plated. ,
This method is not practical because maintenance and management of these electrodes is troublesome and the apparatus becomes complicated.

The present invention has been developed in view of the above circumstances, and can reliably detect the start of electroless plating, and therefore can be effectively used to reliably control the actual plating time and plating film thickness. Moreover, it is an object of the present invention to provide an electroless plating start detection device that is easy to maintain and manage, has a relatively simple configuration, and can be manufactured at low cost.

Means for Solving the Problems That is, in order to achieve the above object, the present invention provides a DC power source, and two wires connected to the positive and negative terminals of the DC power source and immersed in an electroless plating solution. A predetermined current is passed between the metal electrode and the two electrodes by outputting the DC power supply for a predetermined time, and metal deposition is performed from an electroless plating solution for a predetermined time on the electrode connected to the negative terminal of the DC power supply. an electrolysis control means for giving an electrolysis instruction signal to cause electrolysis to be carried out; an inoperation control means that operates for a predetermined period of time immediately after the electrolysis instruction signal stops; and an electrode connected to the negative terminal of the DC power supply and the plated object. A potentiometer that measures the potential difference between the two and the non-operating control means becomes operable immediately after the operation stops, and compares the potential difference value measured by the potentiometer with a predetermined set value, and the potential difference value is determined as the predetermined set value. The present invention provides an electroless plating start detection device characterized in that it is equipped with a comparison means that issues an electroless plating deposition start signal when the electroless plating deposition start signal is reached.

According to the present invention, since a metal electrode such as a metal wire can be used as the reference electrode, its maintenance and management are easy, and the cathode, which is compared with the object to be plated, has a potential difference from the plating solution. Since metal deposition is applied and a plating film is formed in the same state as when the object to be plated is immersed in the plating solution and plating starts, the potential difference when the object to be plated starts plating is always compared. Therefore, when the potential difference between the cathode and the coated object is compared, the surface is always kept in an active state and stabilized, so the potential difference between the cathode and the coated object is always maintained. It is possible to perform stable comparisons, to detect changes in potential difference reliably and sensitively, and to detect the plating start point without error and with reliability.

Further, according to the present invention, the comparison of the potential difference between the coated object and the cathode is started a predetermined time after the electrolysis instruction signal for causing metal deposition on the cathode is stopped by the operation of the non-operation control means. Therefore, a reliable comparison can be made in this respect as well. That is,
When immersing the plated object in electroless plating solution,
In particular, when an automatic conveyance device is used to immerse a plated object in a plating solution, it usually takes several seconds from when the bottom end of the object begins to be immersed to when the top end of the object is completely immersed. When comparing without taking into account the time lag mentioned above, if plating precipitates on a part of the immersed object before it is completely immersed, it will not be possible to cover all of the immersed object. There is a risk that a malfunction may occur in which the start of plating is detected even though no plating precipitation has occurred. However, as described above, the apparatus of the present invention can provide a time lag corresponding to the time required for the plated object to be completely immersed in the plating solution before starting the comparison, so that the plated object can be completely immersed in the plating solution. Since the potential difference can be compared after being completely immersed in the plating solution, the start of plating can be detected reliably.

Further, in the apparatus of the present invention, by making variable the set values for comparing the electrolytic current, time lag, and potential difference between the cathode and the object to be plated, it is possible to adapt to various types of electroless plating.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Embodiment FIG. 1 shows an electroless plating start detection device according to an embodiment of the present invention. In the figure, 1 is a DC power supply, and metal electrodes are connected to the positive and negative terminals of the DC power supply 1, respectively. 2 and 3 are connected, and both electrodes 2 and 3 are immersed in an electroless plating solution 5 in a plating tank 4. Further, the DC power source 1 is connected to a computer 7 via a manual changeover switch mechanism 6, and in response to an electrolysis instruction signal A from the computer 7, the DC power source 1 outputs an output for a predetermined period of time to provide a predetermined gap between the electrodes 2 and 3. A current flows through the electrode (cathode) 3 connected to the negative terminal of the DC power supply 1 to cause metal deposition from the electroless plating solution 5 for a predetermined period of time. In this case, the computer 7 is disconnected by switching the switch mechanism 6 to the manual side, and the electrolysis instruction signal A is generated by turning on the start switch 8.

Here, the DC power supply 1 is preferably a constant current or constant voltage power supply, and the current output thereof is preferably variable within a predetermined range (for example, 0 to 1000 mA), so that the current output value can be controlled. In this case, both metal electrodes (anode and cathode) 2, 3
When electrolysis is performed by applying electricity to the cathode 3, the amount of current should be at least the minimum current that can form a plating film on the cathode 3, but if the amount of current is large, the amount of metal deposited on the anode 3 per unit time will be large. Therefore, it is preferable to flow a very small current that is slightly larger than the minimum current, usually ^about 50 to 500 mA/dm2. Further, although the energization time _t1 is variable, it is usually preferably 1 to 10 seconds. Note that the amount of current is displayed on the display panel 9. As the metal electrodes 2 and 3, in order to eliminate wasteful metal deposition on the cathode, metal wires, metal rods, or other objects with a small surface roughness are preferably used. In the case of No. 2, an insoluble material that is not eluted by electrolysis, such as platinum, is suitable. Furthermore, the material of the metal electrode 3 serving as the cathode is not particularly limited;
Various materials can be used, but platinum, stainless steel, etc., which do not dissolve in the plating solution, are preferably used.

In addition, 10 is a timer (non-operation control means),
Immediately after the electrolysis instruction signal A stops, it operates for a predetermined period of time, and after the operation stops, the comparing means 11 starts operating. Here, timer 1
0 operation time t ₂ means that the object 12 to be plated is covered with the plating liquid 5.
It is set at a time sufficient for complete immersion from the start of immersion, and is usually variable from 0.5 to 20 seconds.

Furthermore, 13 is a potentiometer (sensor), and this potentiometer 13 measures the potential difference between the cathode 3 and the object 12 to be plated.

As described above, the comparison means 11 becomes operational immediately after the operation of the timer 10 stops, and the potential difference value D measured by the potentiometer 13 is given to the comparator 14, where it is set in advance. When the measured potential difference value D reaches the set value S (D≦S), an electroless plating deposition start signal B is issued, the deposition start indicator lamp 15 lights up, and the relay 16 is turned on. The information is transmitted to the computer 7 connected via the computer 7.

Here, to explain the principle of plating start detection according to the present invention, for example, as shown in FIG. 3, when copper is immersed as an object to be plated in an electroless Ni-P plating solution, The potential difference between the cathode and the object to be plated before starting is approximately 500 mV, but once plating starts, metal is deposited on the object to be plated in the same state as the metal deposited on the cathode, and the metal is immediately deposited on the object to be plated. Since the surface of the plated object is covered with this plated metal, the potential difference becomes approximately 0 mV, and therefore, the start of plating can be clearly detected from this change in potential difference (in the figure, L indicates when plating starts, M indicates plating) Before reaction, N indicates after plating reaction). Therefore, by setting the set value S to 0 mV or around it, reliable plating start detection can be performed by detecting that the measured potential difference value D has decreased below this set value (0≦S). It is something that Note that it is preferable that the set value D is variable and can be set using the digital switch 17 or the like.

The computer 7 is connected to the conveyance lifting device 18 for the covered object 12, and when the conveying lifting device 18 transports the covered object 12 to a predetermined position, the computer 7 sends the electrolysis instruction signal A to the DC power source 1 as described above. and when the electrolysis instruction signal A is turned off, the conveyance lifting device 1
8 is given a descending instruction to immerse the plated object 12 in the plating liquid 5, and after a predetermined period of time has elapsed from immediately after receiving the precipitation start signal B from the comparison means 11, The object 12 to be plated is lifted up from the plating liquid 5 by giving a lifting instruction to the conveyance lifting device 18, so that the object 12 to be plated is always moved for a certain period of time (t ₃ ) after plating starts. Plating is applied and the thickness of the plating film is controlled to be constant.

The operation time _t4 of the comparison means 11 is as shown in FIG. Although the operation of the comparison means 11 is designed to continue to stop until it stops, depending on the case, the operation of the comparison means 11 may be stopped at the time when the electrode instruction signal A or the time when the deposition start signal B is issued. can.

Note that the plating start detection device is manually obtained separately from the computer 7, and the plating and start can be detected by the lighting of the precipitation start indicator lamp 15 as described above.
When controlling the plating time without computer control, a timer is provided to control the lifting and lowering of the conveyance lifting device 17, and a deposition start signal B is sent to this timer.
This can be done by, for example, giving the

Furthermore, the configuration of the present invention is not limited to the above-described embodiments, and can be modified in various ways within the scope of the gist of the present invention.

Here, there is no particular restriction on the electroless plating solution in which plating start is detected using the device of the present invention.
Examples include electroless plating solutions such as Co-P, Co-Ni-P, Ni-P, and Ni-B, and electroless copper plating solutions can also be used, but any plating solution can be used. In any case, the apparatus of the present invention is particularly suitable for use in electroless plating where the plating film thickness is thin and the plating time is short.

In addition, the material to be plated may be any material that can be electrolessly plated, and in addition to metals, electroless plating can also be applied to ceramics, plastics, etc. that have metal catalyst nuclei attached to their surfaces. The device of the invention can be used.

Effects of the Invention As explained above, according to the apparatus of the present invention, metal precipitation from the electroless plating solution is applied to the cathode immediately before the object to be plated is immersed in the plating solution, so that the object to be plated can be deposited on the cathode. When the potential difference is compared with the attached object,
A plating film is formed on the object to be plated in the same state as when plating started, and the surface is in an active state suitable for comparison. Therefore, the potential between the cathode and the object to be plated is stabilized. Since the potential difference between can be measured with a potentiometer, the start of plating can be reliably detected from the potential difference measurement result, and this start detection can be performed after the object to be plated is completely immersed in the plating solution. Therefore, there are no errors in detection,
Therefore, the start of electroless plating can be detected reliably and reliably, and therefore it is suitable for controlling the actual plating time or plating film thickness of electroless plating, and maintenance management is also easy. This has the advantage that the device has a simple configuration and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Figure 2 is a signal waveform diagram explaining the operation of the same example, and Figure 3 is a signal waveform diagram explaining the operation of the same example.
The figure shows a chart that measures the potential difference between the cathode and the covered object. 1...DC power supply, 2, 3...Metal electrode, 4...
...Plating tank, 5...Plating liquid, 6...Switch mechanism, 7...Computer, 10...Timer (non-operation control means), 11...Comparison means, 12...Plating object, 13... ... Potentiometer, 14 ... Comparator, 15 ... Deposition start indicator lamp, 18 ... Conveyance lifting device.

Claims (1)

[Claims] 1. A DC power supply, two metal electrodes connected to the positive and negative terminals of the DC power supply, respectively, and immersed in an electroless plating solution; an electrolysis control means for supplying an electrolysis instruction signal to cause a predetermined current to flow between the electrodes and cause the electrode connected to the negative terminal of a DC power source to perform metal deposition from an electroless plating solution for a predetermined time; a non-operation control means that operates for a predetermined period of time immediately after, a potentiometer that measures the potential difference between the electrode connected to the negative terminal of the DC power supply and the covered object, and the operation of the non-operation control means has stopped. It becomes operational immediately after
An electroless plating device characterized in that it comprises a comparison means for comparing the potential difference value measured by the potentiometer with a predetermined set value and issuing an electroless plating deposition start signal when the potential difference value reaches the predetermined set value. Plating start detection device.