A Study of Fatigue-degreeme-asurement of Ferric Chloride Etching Solution by Using Ethylenediamine Tetraacetic Acrd Disodium Salt and Restoring Method of Etching Capability

The etching action of Copper by FeCl₃ solution is a chemical reaction which arises form the potential difference from oxidation-reduction. As for this reaction, the following formula is led.<br>E=E_o+0.059log[Fe⁺³]/[Fe⁺²] E=E_o+0.059log[Cu⁺²]/[Cu] 2Fe⁺³+Cu⇔2Fe⁺²+Cu⁺²<br>Fatigue degree of the FeCl₃ solution is in proportion to decreasing its Fe⁺³ density and increasing its Fe⁺²-Cu⁺² density, on the reason, we tried to measure the density of the FeCl₃ solution.<br>The fractional quantitative analysis for Fe-Cu conjugate solution was studied by Sweetser and Bricker, Underwood and Hoshikawa, but it is not industrial technique. We measured the density of Fe⁺³ with EDTA by means of complexion titration.<br>The following reagents were used for the measurement of the quantitative analysis of Fe.<br>M/100 EDTA solution Salicylic acid (2%Alcohol solution) as an indicator. AcOH: AcONa (each solutionis is 1N, 10:1) as buffer solution. The sample solution: pH 4-4.5<br>We took three stages of the quantitative analysis. At first we titrated Fe⁺³ of Fe⁺³-Fe⁺² conjugate solution, second oxidized Fe⁺² of the solution with H₂O₂ and titrated it (Fe⁺³). Third with regard to Fe⁺³-Fe⁺²-Cu⁺² conjugate solution it is difficult to proceed directly to the fractional quantitative analysis, so we chose the above second method for titration of Fe^+m and titrated Cu⁺² separated by the ion-exchange resin of Colomn Chromatography. The error of Cu⁺² to measure was within -0.34-+9%, but it will be more reduced.<br>At factory the following process should be adopted.<br>1. Take 10cc out of the practically used solution and dilute it to 1, 000cc with distilled water, and take again 10cc out of the dilution for the titration.<br>2. As for the reagents, make use of the above mentioned chemicals.<br>3. The Fe⁺³ is calculated from the following formula.<br>M/100 EDTA:1cc=Fe⁺³:5.585mg<br>The FeCl₃ solution is oxidized by the outside conditions, and it is already known by the fact that Fe⁺² changes into Fe⁺³. And if Fe⁺² is oxidized by the H₂O₂ before increasing Cu⁺², the etching ability of that solution can be recovered.