The RoHS Lead Free Directive and How to Comply

The RoHS Directive 2002/95/EC is often referred to as the Lead-free RoHS, even though it covers five other hazardous materials. The reason for this nick-name may be the ubiquitous nature of lead in electronic equipment and the potential health hazards associated with lead contamination. As per the directive, a product has to be below a threshold limit of 1000 parts per million (ppm) of lead on a homogeneous (any single substance that cannot be separated mechanically) material basis.

The lead content in electronic components and systems comes mainly from discrete and IC (integrated circuit) packages, particularly their solder pins, solder balls or bumps, as well as from electrical insulation materials. Attempts to achieve a lead free regime within the EU have essentially been based on two approaches. The first is innovative new package designs such as Plastic Leaded Chip Carriers (PLCC) and LFQ (plastic) packages. The availability of RoHS qualified packages such as Thin Quad Flat Pack (TQFP); Plastic Quad Flat Pack (PQFP) is slowly but surely increasing.

The second approach is the replacement of conventional Sn60Pb40 solder with lead-free solders which are essentially tin-copper-silver alloys. Each element plays a different role in the solder alloy. The lead-free solders typically have higher melting points and consequently need higher reflow temperatures. Therefore re-engineering of most components used in electronic assemblies is often required. Low lead solders are harder, leading to cracks instead of plastic deformation due to thermal stresses, and so concerns remain regarding long term stability and life-cycle of RoHS compliant products.

Lead free RoHS compliance has been a slow process. Finding the correct components is still a problem, especially in the semiconductor chip segment where the rate of conversion to RoHS compliant parts has not been commensurate with needs. The high cost of process redesign and re-tooling for lead free soldering has also been a deterrent, particularly for small businesses. RoHS compliance issues, however, go beyond merely finding the right components or adopting lead-free soldering.

To successfully comply with the RoHS directive what is required is an all encompassing effort, backed by dedicated management commitment. A good starting point is a "know your customer" program. This gives insight into customer requirements, both short and long-term. It investigates their conversion plans, transition period plans, future requirements of spares for existing leaded products, backward and forward compatibility, etc.

The next important step is a company-wide inter-disciplinary compliance team, supported by a compliance mission statement and roadmap. The roadmap would include milestones for necessary conversions, retooling etc. It is extremely important to asses the company's supply chain exposure and to qualify its suppliers. The success of the compliance program will greatly depend upon the ability of suppliers to ensure RoHS compliance of the materials and components supplied by them. Therefore, supplier qualification is crucial.

An effective end to end material tracking and documentation system is essential for ensuring Lead-free RoHS compliance. It also demonstrates due diligence. The IPC 175X standard for supplier-manufacturer information exchange at different sophistication levels, called "classes" is such a system. Adopting an appropriate class level of the IPC 1752 standard (which is part of the IPC 172X Standard) may be a preferred option. Achieving Lead-free RoHS compliance will not be problem free, but following the above steps can certainly move a company well along the path to both RoHS compliance and a healthier world.