The RoHS (reduction of hazardous substances) and WEEE (waste electrical and electronic equipment) discussion has largely focused on the plastics and additives that go into products, but its impact has gone as far as the technologies used to make those plastic products, including hot runners. At a presentation at the Society of Plastics Engineers (SPE; Brookfield, CT) Global Plastics Environmental Conference, Thomas Linehan, manager of electrical engineering, D-M-E Co. (Madison Heights, MI), detailed how WEEE, enacted in August 2005, and RoHS, instituted in July 2006, have affected his companies production of hot runner manifolds and temperature controls for Europe.
In addition to applying the WEEE symbol (a trashcan with an X through it) to items like hot runners, D-M-E in Europe has to recycle or recover equipment made after August 2005, fully funding that process, while registering with the 25 greater-European nations, except the U.K. where WEEE implementation has been delayed.
Linehan says that in lieu of national clearing houses for recovery and recycling, private for-profit firms have stepped in to aid in the collection process for a fee. In terms of RoHS conflicts or gray areas, Linehan says temperature controllers, a top product for D-M-E, are alternatively described as regulated and not regulated. In addition, restricted components are assigned a maximum weight per assembly, but there is uncertainty as to whether the assembly includes just the circuit board or the whole product.
RoHS has also placed limits on the use of lead, directly impacting soldering for electrical assemblies, with the recommended replacement being a 97% tin, 2.5% silver, and 0.5% copper alloy. This solder requires higher temperatures to process, and there can be voids within the solder once it forms, according to Linehan. In addition, the use of tin promotes so-called whiskers, tiny filaments of tin extending beyond the connector pins. With the pitch, or spacing, of those pins shrinking in recent years, the chance that these whiskers will bridge the gap between pins, and short out the device, are increasing. Linehan offered the example of an old microprocessor with pitches of 0.1 mm, compared to the new, compliant micro, with pitches of 0.5 mm.
D-M-E Co., www.dme.net