Automatic concentration control in PCBA cleaning
When PCBAs are cleaned a lot of factors influence the cleaning result. There are not only the residues which have been cleaned from the PCBAs but also process-dependent influences like evaporation or transportation of cleaner into the rinsing stage. To achieve permanent good cleaning results, continuous monitoring of the cleaning bath is recommended. For this purpose, manual and automatic methods exist.
Manual methods are the measurement of conductance or pH value. However, the result of both measuring methods is influenced by temperature or contamination and do not provide absolute values. Furthermore, if only the above mentioned parameters are analyzed then the cleaning bath quality often cannot be evaluated efficiently when employing water based cleaning processes. On the other hand the concentration of the cleaning agent provides a very good guide to efficiency. To evaluate this parameter there are rapid manual chemical tests, based on acid-base titration, and also refractive index measurement. However both methods are only fully effective with fresh cleaning baths, whereas a further manual concentration measurement method based on the phase separation procedure e. g. the ZESTRON Bath Analyzer works very reliably and accurately independently of contamination.
Besides the above mentioned low priced manual bath monitoring methods there are automatic techniques available, such as the ZESTRON EYE. Utilizing that system, both cleaner concentration and temperature is measured permanently and in real-time. This measurement is more precise than the manual measurement methods and furthermore resistant to contamination. Besides the continuous process data documentation the data can be saved for up to two years providing full traceability. The ZESTRON EYE is compatible with all common cleaning machines on the market and can communicate with their PLCs. It’s expandable by addition of an automatic dosage system (dosage of concentrate and DI water), directly controlled from the measurement data of the ZESTRON EYE.
The additional automatic method is the ZESTRON EYE CM (CM: ‘concentration management’), a product new to the market, a fully automatic stand alone module, performing both automatic concentration measurement and automatic dosage.