Method for detecting concentration of mixed acid solution

Abstract

The invention provides a method for detecting the concentration of a mixed acid solution. In the prior art, the concentrations of various acids in a mixed acid to be detected cannot be accurately measured, or a detection process is complicated, the consumed time is long and more materials are used. The method for detecting the concentration of the mixed acid solution comprises the following steps: providing the mixed acid to be detected with a pre-set volume and a pH compound electrode; titrating with alkali liquid and detecting to obtain a first equivalent point and a second equivalent point by the pH compound electrode; determining the concentration of total hydrogen ions and the concentration of fluosilicic acid in the mixed acid through the first equivalent point and the second equivalent point; carrying out acid titration to recover the pH value of the mixed acid to be neutral; then adding lanthanum nitrate to titrate and detecting by the pH compound electrode to obtain a third equivalent point; and determining the concentrations of hydrofluoric acid and nitric acid through the third equivalent point, the concentration of the fluosilicic acid and the concentration of the total hydrogen ions. By adopting the method, the concentrations of all the acids in the mixed acid of the three acids can be accurately detected, the complexity of detection and calculation is extremely reduced and the professional requirements on detectors are lowered.

Description

technical field [0001] The invention relates to a solar cell manufacturing process, in particular to a method for detecting the concentration of a mixed acid solution. Background technique [0002] In the manufacturing process of crystalline silicon solar cells, hydrofluoric acid (HF) and nitric acid (HNO 3 ) mixed acid to corrode the surface of the polycrystalline silicon wafer to remove the damaged layer during the cutting process of the silicon wafer, and at the same time form a suede surface that can effectively reduce the reflectivity of the silicon wafer surface. In addition, after the silicon wafer is diffused, the silicon wafer will be etched with mixed acid of hydrofluoric acid and nitric acid to remove the PN junction at its edge. The reaction equation for texturing and etching is: 3Si+18HF+4HNO 3 =3H 2 SiF 6 +4NO+8H 2 O. Along with the reaction of described mixed acid and silicon chip, can constantly generate fluosilicic acid (H 2 SiF 6 ), the mixed acid c...

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Problems solved by technology

[0007] The method for detecting the concentration of each acid in the three-acid mixed acid provided in the above-mentioned 201210112213.4 patent application by Niu Chunxiao et al. has the following disadvantages: first, the detection method is too complicated, and a variety of chemicals are used to play an auxiliary role, and the temperature needs to be cooled to 0 ℃-5℃ and heating to generate salt. In addition, the concentration of HNO3 must be detected by oxidation-reduction method, which requires very professional personnel to operate to measure the concentration of the three acids; in addition, the terminal display is complicated and requires the development of various color reagents Auxiliary to effectively judge the titration end point

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