Lead in the tin-lead solder used to assemble the vast majority of electronics provides a number of advantages. Among these are low cost, availability, low melting temperature, and a proven history of resistance to corrosion.

However, the ever increasing disposal of outdated, obsolete, and failed consumer electronic equipment has caused world governments, most notably the European Union, to mandate a reduction or total elimination of lead in electronics. Therefore, alternative solders and component finishes are being identified and implemented to replace lead. For example, tin, a popular choice as a replacement for lead, is an alternative source for filamentary, single crystal tin growths (whiskers). These may create electronic paths and short out circuitry. Zinc and cadmium have also been associated with creating whisker failures in electronic equipment.

Thus, as the July 1, 2006, compliance date approaches, many electronic manufacturing centers and their supply partners are quickly realizing they are facing a huge endeavor to test and document their compliance with the new global mandates. As a result, the market demands instruments that provide fast, reliable and easy-to-understand results.

X-ray fluorescence analysis (XRF) is one of the best solutions for performing an analysis of all components and materials used in electronic products. XRF analyzers provide the perfect screening tool and are able to measure complicated plated layer structures found in common electronic components, ceramic capacitors, and resistors. For instance, XRF can be used to confirm the absence or presence of lead in electronic assemblies. Often, XRF instruments have the capability to scan entire PC boards and generate an element composition mapping of all components and measure coating thickness, two key requirements to meet current mandates. Most importantly, the XRF analysis process is non-destructive and provides results in a matter of minutes, an important factor for quality assurance and in-coming inspection.

Many XRF units permit users to configure a basic pass / fail test to analyze solder and finishes and provide a comprehensive, fully quantitative and qualitative report. Thus, by implementing an XRF inspection process, materials used in the manufacturing of electronic board assemblies can be easily measured to insure compliance with manufacturing standards such as the European directive, which requires less than 0.1 percent by weight of lead in any homogeneous material in any electronic equipment put on the European market.

It should be noted that some equipment using an X-ray fluorescence process will display a spectrum of individual elements as described above, but may not differentiate which layer the lead is present.

For example, a common MLCC layer structure consists of ceramic material. Often, this ceramic contains lead. Currently, only the lead content of the ceramic is exempt; the rest of the MLCC must be brought into compliance. Above this ceramic material is a metallization layer containing silver and lead. A nickel barrier is often found on top of this layer and, above it, tin-lead solder. Thus the component can be completely analyzed, the top layer of lead can be accurately measured, and the findings will comply with the RoHS requirements when lead-free solders are used in the manufacturing of the MLCCs.

This level of XRF analysis often will indicate the presence of lead as a group or gross measurement, thus being interpreted as exceeding the standards and requirements of RoHs. Other equipment, using an X-ray fluorescence process, will clearly identify each layer and reference precisely the composition of each layer.

Currently, XRF analysis is available through the EMPF to assist in the transition of the electronics industry away from tin-lead.

The American Competitiveness Institute recently received an X-Strata 960+ XRF from Oxford Instruments (Figure 6-1), which has been installed and integrated into the ACI EAB Program.

For additional information on the X-Strata 960+ XRF, or to schedule a demonstration, please contact Bob Berta, American Competitive Institute, by telephone at (610) 362-1200, extension 253, or via e-mail at rberta@aciusa.org.