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PREVIOUS NEXTPeroxy-Sulfuric Etching Module
Chemical Analysis/Safety-Analysis Tools
Peroxy-sulfuric etchant tends to be very stable and predictable. That is not to say that the components of the bath do not need to be regularly maintained. In the absence of periodic analysis, the etchant bath will eventually drift out of the acceptable operating region and the etch quality will deteriorate.
Test samples for the techniques presented in this chapter are most easily measured with a 100 uL (0.10 ml) fixed volume "automatic" pipettor. To use this device, place a disposable tip firmly on the end of the pipettor. Depress the plunger until the first stop is felt. Immerse the tip into the liquid to be sampled and slowly release the plunger. To dispense the sample, press the plunger all of the way in (past the first stop) to clear the tip. The disposable tip can be re-used several times, especially if the pipettor is used to consistently measure the same bath.
Using a digital titrator is far superior to pipette titration in terms of convenience, repeatability, and absolute accuracy. The operating principal behind the titrator is usually well described in the manual from the manufacturer and will not be repeated here. One point that is usually left out however, is that the hooked delivery tubes included with the device can be reused indefinitely if they are rinsed out with forced deionized water and shaken like a thermometer to remove any residual liquid. They may also be blown out if care is taken to use compressed air that has been filtered and dried. Always re-use a delivery tube for the same titrant that it was originally used for. Failure to observe this precaution may cause contamination of the titrant syringes and lead to erroneous results.