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106 PCB007 MAGAZINE I OCTOBER 2018 understand, while others seemingly resemble alchemy. Problems and Solutions Stripping problems usually result from two performance deficiencies: failure of the anti- tarnish system and/or wide variance of strip- ping speed and quality with use of the stripper. Most photoresist strippers give adequate an- ti-tarnish performance when the stripper is fresh but at some time during the life of the stripper, the panels start coming out tarnished. This is frequently thought to be the result of the anti-tarnish chemistry being consumed, which is not the case. The real reason this oc- curs is that dissolved copper in the stripper In the world of chemical processes, the ac- tion of the chemistry to bring about the de- sired result is often a blend of both art and sci- ence. The two mesh together quite easily. The job of the chemical supplier is to ensure that sound science is behind the formulation and designed for the job at hand. Remember, the PWB fabricator hires a product or process to perform a certain job, but it is not that simple. Photoresist stripping has become a complicat- ed process due to many unique resist formu- lations on the market. The expectation is that many new concoctions will be introduced over the next few years. What happens chemically during the stripping process depends on a myr- iad of factors. Some of these factors are easy to The Art and Science of Photoresist Stripping, Part 1 Trouble in Your Tank by Michael Carano, RBP CHEMICAL TECHNOLOGY