PCB007 Magazine

PCB-Mar2016

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80 The PCB Magazine • March 2016 • Removing toxic materials from electroless copper baths: Example: Reducing agent formaldehyde, a suspect carcinogen, is replaced by hypophosphite reducing agent. EDTA complexing agent that interferes with heavy metal waste treat- ment, is replaced by tartrate complexing agent. Toxic stabilizing agent cyanide is replaced by citrate. • Recycling of Mylar ® film (e.g., from dry film resist): Used Mylar® film and other PET products can be subjected to a pyroly- sis or alcoholysis process. The polymer is broken down into its building blocks (e.g., terephthalate ester which can be used again as raw material for PET). The recycle volume needs to be substantial to make this process economical. • Flame-retardant Issues: Although halogen- containing and phosphorous compound containing flame retardants are not in- cluded in the RoHS legislation, there is mounting pressure to get rid of these flame retardants, especially brominated flame retardants such as tetra-bromo- bisphenol A. The reasons are diverse: halogen-containing base materials are more expensive to recycle so that OEMs and fabricators see an incentive to get rid of them even without legislation. Studies are underway that are checking into the toxicity of bisphenol A, whether bromi- nated or not. The aversion to phosphorus- derived flame-retardants is not well based on toxicity data. One approach to avoid these compounds and still retain V-0 rat- ing is the use of resins with higher aroma- ticity content (more benzene rings). PCB Karl Dietz is president of Karl Dietz Consulting llC. he offers consulting services and tutorials in the field of circuit board and substrate fabrica- tion technology. To view past col- umns or to reach Dietz, click here. Dietz may also be reached by phone at (001) 919-870-6230. green legislation and the impaCt on eleCtroniC materials and proCesses A new one atom- thick flat material that could upstage the won- der material graphene and advance digital technology has been discovered by a physi- cist at the university of Kentucky working in collaboration with sci- entists from Daimler in Germany and the In- stitute for Electronic structure and laser (IEsl) in Greece. Reported in Physical review B, rapid communi- cation, the new material is made up of silicon, bo- ron and nitrogen—all light, inexpensive and earth abundant elements—and is extremely stable, a property many other graphene alternatives lack. "We used simulations to see if the bonds would break or disintegrate— it didn't happen," said Madhu Menon, a physi- cist in the uK Center for Computational sciences. "We heated the material up to 1,000°C and it still didn't break." using state-of-the- art theoretical compu- tations, Menon and his collaborators Ernst Rich- ter from Daimler and a former uK Department of Physics and Astronomy post-doctoral research associate, and Antonis Andriotis from IEsl, have demonstrated that by combining the three ele- ments, it is possible to obtain a one atom-thick, truly 2D material with properties that can be fine- tuned to suit various applications beyond what is possible with graphene. New 2D Material Could Upstage Graphene

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