I. Preface

A liquid that carves by eroding the properties of materials. At present, there are mainly six types of etching solutions in use: acidic copper chloride, basic copper chloride, ferric chloride, ammonium persulfate, sulfuric acid/chromic acid, and sulfuric acid/hydrogen peroxide etching solutions. The etching speed of the ferric chloride etching solution is mainly affected by the etching temperature, the content of hydrochloric acid and the content of iron ions. The influence of the addition amount of hydrochloric acid in the etching solution: Adding hydrochloric acid to the etching solution can inhibit the hydrolysis of FeCl3 and increase the etching rate, especially when the copper dissolution amount reaches 37.4g/L, the effect of hydrochloric acid is more obvious. However, the amount of salt acid added should be appropriate. If the acidity is too high, it will cause damage to the liquid photoresist coating. In this experiment, the JH-T6 fully automatic potentiometric titrator was used to determine the endpoint based on its potential jump point and measure the content of hydrochloric acid to verify the feasibility of the experimental plan.

Ii. Instruments and Reagents

2.1 Instruments

JH-T6 fully automatic potentiometric titrator, composite PH electrode, analytical balance, etc

2.2. Reagents

3mol/L KF solution, 0.1mol/L sodium hydroxide standard titrant

Iii. Experimental Methods

3.1 Experimental Process:

Accurately weigh 1g of the sample to be tested (accurate to 0.0001g), add 50mL of deionized water and 25mL of 3mol/L KF solution in sequence, mix well, and titrate with the calibrated sodium hydroxide titrant until the potential suddenly exceeds the endpoint. At the same time, conduct a blank test and calculate the content of hydrochloric acid.

3.2 Instrument Parameters

The instrument parameters are shown in Table 1

Table 1 Parameter Settings of Titrator

Iv. Results and Discussion

4.1 Experimental Results

The samples were tested and the experimental results are shown in Table 2

Table 2 Content Test Results

 4.2 Titration chromatogram

4.3. Conclusion

This test determined the content of hydrochloric acid in the etching solution through potentiometric titration. The instrument's judgment reduced human errors and significantly improved the accuracy of the experiment. Therefore, potentiometric titration is a good choice for detecting such samples.