Lead / Lead Free
Regarding Lead vs. Lead-Free soldering, the Restriction of Hazardous Substances directive, more commonly known in the electronics industry as RoHS, took effect in 2006 in the European Union. In turn, RoHS restricts the use of certain hazardous substances in electrical and electronic equipment. Over time, this environmental standard has spread more towards the mainstream, and in decisions to move to RoHS, it is important to understand the complexity of this transition. Many individuals believe that converting to RoHS is just a matter of selecting RoHS components and manufacturing with lead-free solder. The issue is that many parts may be RoHS compliant, but they cannot handle the more extreme RoHS manufacturing process. There is a difference between being RoHS compliant versus being RoHS compatible. RoHS compliant means that the component does not contain six hazardous substances: lead, mercury, cadmium, hexavalent chromium, PBB, & PBDE. Closely linked with the RoHS directive is the Waste Electrical and Electronic Equipment directive which is more commonly known as the WEEE directive. The WEEE directive sets collection, recycling and recovery targets for electrical goods. The effect these two initiatives have had on the electronics industry varies greatly depending on product end use and target sales market. The overall supply chain from individual components to bare printed circuit board manufacturing has shifted from a predominately tin-lead alloy based market to one that caters almost exclusively to lead-free finishes. The result has been limited supply, and in some cases, complete elimination of tin–lead plated components. This has, in effect, forced manufacturers to make design and process changes on products that were traditionally tin-lead based.
In selecting alternate materials to plate the leads, component manufacturers will look at characteristics such as solderability and resistance to whiskers. It does not mean that these parts are compatible with the manufacturing process. RoHS compatible means that the component can handle the higher solder temperatures used in RoHS board assembly. RoHS manufacturing requires at least 30º C higher soldering temperatures than Tin-Lead to ensure reliable connections between the board and components. Also, since lead-free solders have poorer wettability, the components and PCB are held at this higher temperature for much longer time than tin-lead solders. The issue is that some RoHS compliant components cannot handle these elevated temperatures. As a result of this higher process temperature, liquid-containing components, such as aluminum electrolytic capacitors can blow apart, bulge, or blow electrolyte out their seals; large ceramic components, such as resistors, capacitors, and inductors, may crack because the components shrink more than the PCB does as the assembled board cools down from the solidus temperature of the solder; delaminating or cracking of components can occur when moisture is absorbed by the plastic package turns to steam; components can warp if the plastic’s softening temperature is reached; degrading of the plastic can occur if the degradation temperature is approached; breaking or weakening bonds inside the component, from differential expansion/contraction between conductors and the surrounding insulators, can occur if the Glass Transition Temperature Tg is exceeded.
PPI-Time Zero can help you mitigate these issues through careful component selection, selected manufacturing techniques, and Design for Manufacturing (DFM). Because of the growing need for RoHS compliance, it is critical that designs are evaluated for manufacturability, and that your manufacturing partner has extensive materials expertise. DFM is a valuable part of our service offerings to help ensure the quality of your product, in addition to a careful selection of components and processes to make your project successful.LEAD/LEAD-FREE