The most pressing issue many designers of medical electronics have in the foreseeable future is how to effectively design lead-free products. It's difficult to kick long-standing habits associated with designing lead-based products.
But designers must learn to do so, because within the next year or so the European Union's Restriction of Hazardous Substances (RoHS) lead-free directive is expected to incorporate medical electronics. Hence, medical device designers must start now to incorporate new design considerations and understand the adverse effects previous lead-based design techniques can have on lead-free electronics assemblies.
Component suppliers report that most major medical electronics OEMs are moving toward RoHS compliance. Yet, there are many small and midsized medical electronics manufacturers operating under a cloud of confusion over a variety of lead-free issues and technologies.
Many OEM designers buttonhole themselves into their own engineering departments, refusing to consult with outside experts. This is not a good idea, because the lead-free regime introduces numerous design methods and components, including printed circuit board (PCB) laminates, surface finishes and solder pastes. Each carries unique characteristics, tradeoffs and potential pitfalls that can be avoided only with specialized know-how.
Out with the old
Take components, for example. Medical electronics OEMs are at times reluctant to make product changes—especially if a product is functioning properly, and is FDA-approved, time-tested and verified. However, with ever-changing technology, components often become obsolete. This is certainly the case now, as component makers transition to lead-free. So once plentiful lead-based components are becoming obsolete, and OEMs that insist on them must pay a premium.
Savvy medical electronics OEMs develop contingency plans for designing out obsolete components. Some also get support by working in tandem with an electronics manufacturing services (EMS) provider or contract manufacturer (CM) knowledgeable about lead-free medical electronics. In addition to locating components, these organizations can help OEMs avoid surprises by providing component lifecycle alerts. They can also counsel on the tradeoffs and options at hand.
For instance, the OEM can test prototypes while designing out a particular component over three to six months, or can buy two to three years of soon-to-be obsolete components inventory to cover its production for that period. However, the key to success in this regard is to rely on a knowledgeable EMS provider or CM. The main service here is disciplined and expert communications with the OEM to keep it updated on obsolete component schedules.
Assuring lead-free components are used where necessary is another critical aspect of successful design. A miscue in this regard can prove disastrous. For example, SMT component selection at design layout can have a major adverse effect at assembly if a particular component doesn't meet the higher lead-free temperature requirements (255º C to 260º C). So it's essential to clearly identify the component and its package for reflow temperatures.
