JPH0261554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for directly measuring the etching rate in etching processing.

[Conventional technology/problems to be solved]

Generally, in etching processing, such as copper etching processing of printed circuit boards, the composition of the etching solution is controlled by measuring the composition each time using a chemical analysis method and replacing or replenishing the etching solution. Specific methods include collecting the etching solution as appropriate and titrating the etched metal component with a reagent, or measuring the oxidation ring potential of the etching solution to determine the concentration of metal ions in the solution. It has been known. However, these methods do not directly measure the etching rate of the etching solution, but only indirectly estimate the etching rate from the composition of the obtained etching solution. There are also devices that automatically perform titration, but these devices are large and have many disadvantages in terms of space and equipment costs.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an etching rate measuring method that can quickly and easily determine the deterioration state of an etching solution and manage the etching solution without requiring reagents or large-sized equipment.

The object of the present invention is to (a) provide a first electrode and a second electrode inserted into an etching solution.
A first step in which the metal to be etched is deposited on the second electrode by applying current to the electrode, and then (b) a third electrode inserted in the same etching solution is connected to the second electrode to deposit the metal on the second electrode. This is achieved by a method for measuring the etching rate of an etching solution, which comprises a second step of measuring the time taken for the metal to dissolve, and determining the etching rate of the etching solution from this time.

[Action of the invention]

The present invention will be explained in more detail below with reference to the drawings. FIG. 1 is a diagram for explaining the method of the present invention. In FIG. 1, 1 is a constant current power source, 2 is a potential difference measuring device, and 8 is a microcomputer, which form a control section B. In FIG. In addition, 4 is a stirrer, 5 is a first electrode, and 6 is a second electrode.
The electrode 7 is a third electrode, and these form the sensor section A.

If you want to know the etching speed of the etching solution in a certain etching process, collect the etching solution 10 in the container 9 of the sensor section A, close the relay 3, and apply current from the constant current power source 1 for a certain period of time. Etched metal ions (e.g. copper ions) in the etching solution move between the first electrode (e.g. platinum electrode) 5 and the second electrode (e.g. platinum electrode) and are deposited (plated) on the second electrode. . The thickness of the metal layer deposited at this time is substantially constant regardless of the concentration of metal ions in the etching solution.
After energizing for a desired time, the relay 3 is switched to connect the second electrode 6 and the third electrode 7 (for example, a platinum electrode) via the potential difference measuring device 2 to form a closed circuit. At this time, a potential difference is generated between the second electrode and the third electrode, and this potential difference can be read by the potential difference measuring device 2. By the way, since the second electrode is in the etching solution, the metal deposited on the second electrode is gradually dissolved by the etching solution, and when all of the metal is dissolved, the second electrode becomes only platinum. At this time, the potential difference indicated by the potential difference measuring device becomes 0. Therefore, the time from when the relay is switched to connect the second and third electrodes until the potential difference between the two electrodes becomes 0 is measured, and the arithmetic circuit 8 calculates the etching time using the etching solution. You can know the speed immediately. Incidentally, during the measurement, the stirrer 4 is always operated so that the composition of the etching solution becomes uniform. Alternatively, the etching solution may be circulated within the container 9 as shown in FIG.

After the series of operations described above, that is, after collecting the etching solution, energizing the first and second electrodes from a constant current power source, switching the relay, and connecting the second and third electrodes indicated by the potential difference measuring device. Measurement of the time until the potential difference between the two becomes zero, calculation to determine the etching speed of the etching solution from this time, display of the etching speed, and further operations such as replacing the etching solution should be controlled by a microcomputer. Can be done.

Fig. 1 shows an example in which the etching solution is collected in the measurement container 9 for measurement, but as shown in Fig. 3, the bottom of the container is opened and the sensor section A is placed directly in the etching bath. May be inserted.

The method of the present invention will be explained in more detail with reference to the following examples.

〔Example〕

The first example shows the use of the etching rate measurement according to the present invention for copper etching process control of printed wiring boards.
This will be explained with reference to the figures.

A platinum plate was used as the first electrode 5, a disk-shaped platinum plate was used as the second electrode 6, and a platinum wire-type oxidation ring source electrode was used as the third electrode 7. A constant current of 100 mA was applied between the first electrode and the second electrode for 60 seconds. By this energization, copper with a thickness of 3.0 μm was deposited on the second electrode. Thereafter, the current was turned off and the potential between the second and third electrodes was measured using a potentiometer. The potential is 500mV potential difference between copper and platinum.
showed that. After the energization ended, it took 2 minutes and 30 seconds for the potential difference to decrease from 500 mV to 0. That is, the etching rate is 1.2 μ/min.

Furthermore, after 3 hours, the same operation as above was performed, but the time it took for the potential difference between the second electrode and the third electrode to become 0 was 3 minutes and 10 seconds, and this time was
This corresponds to an etching rate of 0.95μ/min.

〔Effect of the invention〕

According to the method for measuring the etching rate of an etching solution of the present invention, the etching solution can be optimally controlled at all times, and it is possible to prevent etching residue caused by a defective etching solution or poor soldering in the next process.

In conventional etching solutions, the etching rate is estimated by chemically measuring the components of the etching solution, but this method requires titration, requires skill, and is time consuming. However, the method for measuring the etching rate of an etching solution according to the present invention actually measures the rate at which metal is etched;
This method is excellent as a liquid management method, and since there is no need to use reagents for measurement, maintenance of the measuring device has become easier.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the method of the present invention, Figure 2 is a diagram for explaining the method of the present invention.
3 and 3 are diagrams showing one embodiment of the present invention. 1... Constant current power supply, 2... Potential difference measuring device, 3
... Relay, 4 ... Stirrer, 5 ... First electrode, 6
...Second electrode, 7...Third electrode, 8...Arithmetic circuit, 9...Measurement container, 10...Etching liquid.

Claims (1)

[Claims] 1. (a) A first step in which the metal to be etched is deposited on the second electrode by applying electricity to a first electrode and a second electrode inserted in an etching solution, and then (b) in the same etching solution. The second step is to connect the inserted third electrode and the second electrode, measure the time for dissolution of the metal deposited on the second electrode, and calculate the etching rate of the etching solution from this time. Characteristic method for measuring etching speed of etching solution.