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Continued from March 2008  CTI Newsletter

City Theatrical Gets the Lead Out

By Pranav Shah

In November 2007 the City Theatrical Electronics Assembly department completed its conversion process to meet the European Restriction of Hazardous Substances Directive (more commonly known as RoHS).   Although RoHS is best known for banning lead in electronic devices, five other substances are also included in the directive – mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ether.  These substances are commonly used in all pre-RoHS electronic devices (computers, televisions, phones, etc.).  They are not toxic while in use in our homes and workspaces, but once discarded in landfills they leach into the soil and enter our environment.

 City Theatrical constructs every one of its electronic products from the circuit board level up, so every part, component, and tool in the shop had to be tested and confirmed as RoHS compliant.  This conversion process took approximately four months of research, planning, and application to complete.  During this time we faced several challenges including logistical planning of inventory (both finished goods for shipment as well as components for assembly), learning what new processes were required, and learning how we would need to change current processes.  Our best sources for advice on this came from other manufacturers, their representatives, and our suppliers of products used in the assembly process.

 During the actual conversion of our assembly shop, aspects of production had to be slowed or halted for periods over the course of two weeks.  Each workstation and requisite equipment had to be cleaned and tested.  Components had to be verified as RoHS compliant while non-compliant parts were segregated or phased out.  The sourcing and purchasing of RoHS compliant components had started months before, so most of the non-compliant parts had already been used and rolled over. 

 The biggest single challenge and threat to our production schedule was the cleaning of our wave solder machine, and we quickly learned we were one of the first in the region to do so.  We were in uncharted territory as the manufacturer of our wave solder machine had never seen a company perform this process, and did not have any formal procedure to guide us.  That being the case, they were helpful in guiding us through the process over many phone calls and emails.  In short, we had to drain the 250 pound pot of leaded solder, thoroughly clean it, refill it with pure tin in order to get the residual lead out, drain it again, thoroughly clean it again, and fill it with the new lead-free solder.  After the new solder had mixed and melted in the pot, we sent a sample from the pot to a lab for analysis.  The results showed the sample was within the necessary requirements of the RoHS directive thus validating our conversion to lead-free.

 The most significant challenge for our employees was learning how to use lead-free solder.  Since the standard Sn63Pb37 could no longer be used, new formulas of tin, silver, and copper have become the industry’s preferred alloy.  This alloy (commonly referred to as SAC) has a much higher melting temperature of 217°C, versus the old 183°C of leaded solder.  The higher melting temperature requires longer dwell times for irons and longer contact time in the wave solder machine for the solder to properly flow.  One of the concerns our manufacturer’s representatives told us to look for were cold solder joints and inadequate flow.  With new temperature and speed profiling of the machine—and a few sacrificial circuit boards—we proved we could achieve appropriate solder joints on components.

 As of December 2007, anything manufactured in the electronics assembly department meets the European RoHS directive.  Accordingly, City Theatrical has officially “gotten the lead out.”

 

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