JPS6033045A - Quantitative determination of metallic ion in electroplating liquid - Google Patents

Abstract

PURPOSE:To measure quickly Pb<2+>, Sn<2+>, Sn<4+> in an electroplating liquid with good accuracy by making use of the phenomenon that Sn<4+> does not disturb the quantitative determination of Pb<2+> and Sn<2+> in a phosphoric acid soln. and that Pb<2+> does not disturb the quantitative determination of Sn<2+> and Sn<4+> in a pyrogallol soln. CONSTITUTION:A fixed amt. of an electroplating liquid sample is drawn and is heated for about 15min at 90 deg.C. H2O2 is added thereto to oxidize all the Sn in the sample to Sn<4+>, then an ascorbic acis is added thereto to reduce the Fe<3+> in the sample and thereafter a phosphoric acid is added to the sample and the concn. of Pb<2+> is known by using a calibration curve from the Pb<2+> peak. A fixed amt. of the sample is added to the ascorbid acid to reduce Fe<3+> and thereafter a phosphoric acid is added thereto. The concn. of Sn<2+> is known by using the calibration curve from the peak height obtd. by subtracting the Pb<2+> component determined previously from the peak height of Sn<2+>+ Pb<2+>. A fixed amt. of the sample is added to the ascorbic acid to reduce Fe<3+> and thereafter Sn<2+> is made Sn<4+> by the soln. prepd. by adding HClO4 to pyrogallol and the peak which is the sum of Sn<4+> existing in the sample and Sn<4+> from Sn<2+> is determined. The peak for the above-described Sn<2+> component is subtracted therefrom and the concn. of Sn<4+> is known.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to Pb''+ Sn2+ and (・
Top--'-++↓)+, Okirz Tomo, +enter (Background of the Invention) The presence of Pb2+ in the electroplating solution has an adverse effect on the plating properties. On the other hand, Sn is sometimes added to the plating solution to improve plating properties, but Sn is
It is in a valent and tetravalent state and has a strong tendency to hydrolyze and form a precipitate. Of these Sn, only ionic Sn2+ and Sn4+ are effective in improving plating properties. Therefore,
In order to control the plating properties, Pb”, S
It is necessary to bring n''4' and Sn'+ to a constant value quickly.

(Prior art) DPASV (Differential Zero Parallel Anodic Stripping Portammetry) is a suitable method for analyzing trace metal ions in solutions.
PV (differential pulse portammetry), etc. In both cases, information about ions in the sample solution can be obtained from the potential-current curve at the electrode immersed in the sample solution. This is a powerful electrochemical analysis method. There are several precedents for individually analyzing each of Pb'', an!+, and Sn'+ using portammetry. For example, the determination of Sn'+ in a pyrogallol solution, and the determination of ” and the quantitative determination of Sn'+. However, Zn and F
PB", Sn"" in the electroplating solution containing e as the main component
There is no example of total quantification of these trace components. This is because the main components Zn and Fe affect the analysis results, and the trace components interact with each other, making it difficult to achieve high accuracy. This is because no analysis is performed.

(Object of the Invention) The present invention suppresses the above-mentioned effects and improves P in the electroplating solution.
The aim is to accurately quantify b ” + Sn' ” and Sn'.

(Structure of the Invention) The present invention takes advantage of the fact that Sn'+ does not interfere with the determination of Pb2+ and Sn2+ in a phosphoric acid solution, and that Pb2+ does not interfere with the determination of Snt+ and Sn'+ in a pyrogallol solution. It is something to do.

That is, the present invention provides S measured in a phosphate supported electrolyte.
pb'' peak of the n-oxidized sample solution, (sn''+pb'') peak of the Sn unoxidized sample solution measured in the phosphate-supported electrolyte, and ('Sn'' + Sn of the Sn-unoxidized sample solution measured in the pyrogallol-supported electrolyte). Pb2+, 3n2+, and S+i'+ in the plating solution are electrochemically quantified from the ``) peak.At this time, the influence of Fe''+ ions can be reduced by adding ascorbic acid to reduce Fe3+. suppress. Further, the support '1Jt solute is selected in consideration of preventing precipitation of ZnFe, which is the main component of plating, and that its peak does not overlap with the target component.

a. Quantification of Pb"+ By heating the sample, Fe'+ in the sample promotes the oxidation of Sn" and all 3n becomes Sn'+, or by adding 1(,O,) to the sample. to oxidize all Sn to Sn40.Next, ascorbic acid is added to oxidize Fe3+.
to reduce. Then, Sn4+ in the sample was masked with a phosphate supporting electrolyte, and I)b2++') was measured by DPASV.
Measure the e −≠Pb' (I(g) peak, and quantify the Pb needle from this measured value.

b. Add ascorbic acid to a quantitative sample of Sn20 to reduce Fe"
This aims to suppress the influence of 3+ ions and prevent the oxidation of Sn''+.Next, after diluting the sample with a phosphoric acid solution to mask Sn'+, DPASV is carried out to suppress the influence of Sn''+2e-sol and SnSn0 (H peak and Pb2++2e -Sosuke Pb'
A peak with overlapping (Hg) peaks is obtained.

By subtracting the previously determined pb'' from this value, the Sn'' can be calculated.

c, Ascorbic acid was added to the quantitative sample of Sn'+ to reduce Fe3+, and F
This aims to suppress the influence of e3+ ions and prevent the oxidation of Sn''+.Next, when the sample is diluted with pyrogallol-HCl2. solution and DPV is performed, both Snz+ and Sn4+ are Sn'''+2 e'--8n'' and 3n
"-1-2e-so→SnSn0(H) shows two peaks. However, Sn"+2e-so→SnO(TI
g) The peak is pbt" + 2 e-, ==Pb'(
Hg) overlaps with the peak, so Sn" + 2e-, = i
Sn'+ is quantified using the ThSn'+ peak. In other words, Sn”+ where Sn”+ and Sn4+ overlap
Calculate B n 4 + by subtracting the previously determined Sn2 2e−<−8n”+Peafka.

(Example) p b2 + in a plating solution containing Zn-Fe as the main component
, 3 specifically shows the method for quantifying n2+ and Sn4+.

First, sample 5 samples of the plating solution and place them on a water bath.
Either heat at 0°C for 15 minutes or add 20m of HtO after sampling (1,099°C) to remove all Sn.
It is also oxidized to n4+. Oxidation due to heating removes Fe in the sample.
”+ If the concentration is above I G D Oppm, 90°C,
15 minutes was sufficient. Next, 5 m of 10 thiascorbic acid was added to reduce Fe3+.

Subsequently, after adding 0.5 MH3PO45d, H,O
diluted to 50-. DPASV was carried out using this as a measurement solution under the measurement conditions shown in Table 1, and the pb2+ concentration was determined from the obtained pb'' peak height using the pbt+ analytical line.In addition, under the same measurement conditions, the pb2+ concentration was calculated. , Ct voice, etc. can also be added.

Table 1. DPASV Measurement (Pb'+) Next, 5 ml of the plating solution was sampled, and 10 thiascorbic acid 5- was added to reduce Fe'+.

After adding an additional 0.5 ml of MH3P045
Diluted 50- with IO. Using this as a measurement solution, DPASV was carried out under the measurement conditions shown in Table 2 to obtain (Snz
+-1-Pb") from the peak height, subtract the amount corresponding to the previously determined Pb" concentration using the pb'+ calibration curve, and then use the 8n"+ calibration curve to subtract the amount corresponding to the Pb" concentration determined previously. The degree was calculated.

Table 2. DPASV measurement conditions (for Sn”+) Continued
A plating solution sample 5- was sampled, and after adding 10 thiascorbic acid 5-''f to reduce Fe''+, 0.12
Diluted to 50M with M pyropyrogallol-12M HCIO* solution. Using this as a measurement solution, DPV was carried out under the measurement conditions shown in Table 3, and the obtained Sn" + 2e
--8J1"Peak height Sn" 10Sn4+) was read. S n ” ” * S n in this solution
” 'Since the calibration curve is slightly distorted, the method for calculating the Sn' tenth ratio will be explained below according to Figure 1. In the figure, h is the peak height of the sample read, and C is the h read from the sn4+ calibration curve. The corresponding Sn'+Q degree, the turtle's previous S-'concentration, b
Indicates the Sn' 10 concentration that gives the same peak height as the Sn''+ peak height corresponding to n a. Therefore, Sn' 10 degrees can be expressed as c - b.

Table 3. D PV measurement conditions (for 3n 4+) Table 4 shows the measurement results when the same sample was analyzed continuously in this manner. As is clear from Table 4, the method of the present invention enabled analysis with high paper precision. The time required for the analysis was approximately 940 minutes for each sample.

Table 49 Analysis results (ppm)

[Brief explanation of drawings]

FIG. 1 shows the calibration curves of B n t + and Sn'+ in the pyrogallol system with varying Sn'+ concentrations. Agent Patent Attorney Toshi Satoshi Sasaki

Claims (1)

[Claims] (1) In the constant of metal ions in the electroplating solution by portammetry, S measured in a phosphate-supported electrolyte
The pb2+ peak of the n-oxidized sample solution, the (Sn''+Pb2+) peak of the Sn unoxidized sample solution measured in the phosphate-supported electrolyte, and the (Sn''+Pb2+) peak traced in the pyrogallol-supported electrolyte fr)
(Sn”+Sη4+) peak force of Sn unoxidized sample solution＼
p b2 + , 3 n2+ and S in the plating solution
Calculating the amount of n'+ is 4? A method for quantifying metal ions in electroplating liquid based on the characteristics. (2. Claim (t) i) A method characterized by reducing D Fe 3+ (D Fe 3+ in a group feed solution) with ascorbic acid in the self-published method.