Printed Circuit Design & Fab - September 2008 - (Page 22)

ENvIRONMENTAL uPdatE Design for Green: LaminaTes Taking the risk for a greener planet. by MICHAEL TAyLOR The need to control hazardous materials has influenced the design of circuit boards since their conception. While the industry has worked to minimize these materials by incorporating less-toxic ones, some of these safer solutions have their own risks to the environment and the health of the population. Incorporating green laminates into PCBs is just one stage of a continuing tradition of risk management in design. In recent months, published findings regarding the safety of commonly used flame retardants has the industry rethinking previous efforts to remove all halogens from the laminate supply chain. Recently, the European Union (EU) passed far-reaching environmental laws, known as RoHS and WEEE, that have affected the electronics industry. Japan, China, Korea and many other countries have followed suit with laws attempting to regulate products either produced or imported into their countries that may contaminate the environment. These regulations, while locally implemented, have global impacts. In a world economy, products are manufactured to the most severe standards so that there are no barriers to sales. As a result, the electronics industry has been impacted in order to accommodate these requirements. There are myriad regulations throughout North America, including those pertaining to individual states and Canada. There are additional regulations being debated by state and local governments on a regular basis. FiGurE 1 is a summary of many of these regulations, supplied by Dynamic Details Incorporated (DDi) of Anaheim, California. The most severe of these regulations will affect manufactured products not only in an individual state, but also in any country that the company may want to export to from its individual state. temperature (Tg) materials made with this curing agent have been found to have inadequate temperature capability for lead-free assembly on high-layer-count boards, although it may be adequate for some low-layer-count applications. Multifunctional epoxies with phenolic curing agents were adopted to provide higher-temperature capabilities chemically. In addition, low coefficient of thermal expansion (CTE) inert fillers were compounded with the resins to reduce the overall change in dimension during thermal excursions. This provided higher-temperature capabilities mechanically. For example, flame retardant materials interfere with the burning process, either by cooling or by preferentially reacting with decomposition products, excluding oxygen. As additives, their intent is to reduce the risk of injury from fire. Printed circuit boards were formulated using brominated hydrocarbons and antimony trioxide to ensure they burned slowly and were self-extinguishing. Certain sources of bromine, which includes most polybrominated diphenyl ethers and polybrominated biphenyls, have been found to have unac- High-Temperature and HalogenFree Materials Dicyanamide is a latent curing agent for epoxies commonly used before the advent of leadfree capable materials. High glass transition FiGurE 1. Summary of active or pending legislation in the US and Canada. 22 printEd CirCuit dESign & fAB SEPTEMBER 2008

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - September 2008

Printed Circuit Design & Fab - August 2008 Contents Our Line Market Watch Around the World Happenings ROI Positive Plating Off the Shelf Marketplace Ad Index EMC for the Real World Final Finish Forum Design for Green: Laminates A Systematic Approach to Increasing Layer Count The NTI $100 Million Club Printable Nanocomposites BGA Bulletin

Printed Circuit Design & Fab - September 2008

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