Change is a given. While this adage may be quite true and normally a good thing, it can wreak process engineering havoc in a printed circuit operation. Change is good, but the operative word is controlled change relative to the complex processes involved in manufacturing a printed circuit board. The key to successfully navigating process change is to develop a robust Temporary Process Change (TPC) program.
Process Engineering: 75% Science, 20% Black Magic and 5% Luck
My process engineer friends will certainly take exception to this statement, however, no matter how talented our process gurus are, I believe I could make a compelling argument with them over a couple of beers. It is incontrovertible that two plus two will always equal four, no matter who is doing the math. If printed circuit process engineering was 100% science, then what works in one shop would work just as well in every other shop, period. We all know that is about as true as the statement that “politicians never lie.” That is why it is so important, once the process recipe has been engineered to be highly repeatable, to have a controlled method to continue to tweak and improve it.
Even in the most controlled manufacturing environment, internal audits, rework and yield issues can oftentimes be traced back to an unauthorized minor process change. Changing a bath temperature or time, skipping a traveler step, or changing the supplier for a consumable may seem like a good idea at the time—until everyone is scratching their heads over a spike in scrap. Operators, leads and supervisors have their hearts in the right place when they want to try an idea to improve a process. More times than not they simply lack experience with the DoE (design of experiment) or other controlled change methodology.
To read the full version of this article which appeared in the September 2017 issue of The PCB Magazine, click here.