Issue link: https://iconnect007.uberflip.com/i/1529411
NOVEMBER 2024 I PCB007 MAGAZINE 39 free acid level decreased, but so did the etch rate. It appears to be a given that anything done to decrease sideways etch also lowers the etch rate. Testing has shown the lowest sideways etch occurs at around 0.8N. Free acid levels below this become hard to control and don't improve the etch quality that much. I usually recommend running the cupric chlo- ride etchant at a specific gravity of 36°Be and a free acid level of 0.8N for the best etch quality. ere is an etch rate penalty for this, however. e etch rate for a cupric etch bath running at 32 o Be and 1N free acid is usually around 1.2 to 1.3 mils/min (30.5 to 33 µm/min) as opposed to 1 mil/min (25.4 µm/min) for a bath running at 36°Be and 0.8N free acid level. ere is one potential process problem while running at low acid levels that was recently brought to my attention: losing control and finding that there is no free acid le. One func- tion of free acid is to keep the cuprous chlo- ride byproduct of the etch reaction in solution. It is not very soluble in water and precipitates out of solution when the acid level gets too low. is will affect your ORP readings since they indicate the ratio of cupric ions to cuprous ions. If the cuprous ions precipitate out of solu- tion, then the ORP reading will be inaccurate, and your etch bath will stop etching. e signs of this are the color of the etchant changing from dark jade to neon green and your ORP readings going to 900+ mv but with no chlo- rine odor. Fortunately, adding acid back to the bath (and a lot more than you think) will bring the bath back to normal. Hopefully, this will help answer some ques- tions that come up about the best operating conditions for achieving the highest cupric chloride etch quality under production condi- tions. PCB007 Don Ball is a process engineer at Chemcut. To read past columns or contact Ball, click here. In a future where fully autonomous vehicles rule the road, cars and trucks will move to a split-second torrent of data shared by computers that are on board, nearby and in the cloud. In this dynamic web of communication, any failure in the network is a threat to passengers. To ensure that cyber-physical systems—like a fully automated transportation sys- tem—can withstand breakdowns, hacking and un- anticipated situations, the National Science Foun- dation (NSF) is funding a new center led by Purdue Universi- ty to develop scientific mecha- nisms that enable resilience in the face of threats, with the goal of using technology develop- ment to help inform policy. Through this project, the team expects to develop new compu- tational approaches and solutions that ensure resil- ience in systems composed of interconnected hard- ware and software components, which individually may not be inherently highly reliable or secure. While the project will develop these tools around CATS, the foundational computer breakthroughs that will emerge from the project will be applicable to many large-scale cyber-physical systems. Researchers anticipate that all vehicles con- nected and operating autonomous- ly will improve safety, estimating an 85% reduction in the current rate of 100 deaths per day, and more than 14,000 collisions per day, accord- ing to the National Highway Traffic Safety Administration. (Source: Purdue University) Purdue University Leads Research on Autonomous Transportation Network