Launch of report - XRF Measurement of Residual Materials in Electronics
Dec 12, 2007
The purpose of this study was to investigate the suitability of using XRF systems for screening electronics parts in two applications; RoHS compliance and tin whisker mitigation.
In total, fifteen systems were tested with a range of forty typical electronics components and assemblies. Eleven different systems were evaluated at twelve different sites. Systems based on PIN, SiLi and proportional counter detectors were included. Eleven systems were bench top instruments and four were portable.
The results indicate that while PIN (semiconductor diode) and SiLi detector based systems are suitable for RoHS compliance measurements in plastics and solders, proportional counter based systems are not. XRF systems using PIN or SiLi detectors generally proved efficient at distinguishing between non-compliant components (containing typically 2000+ppm of restricted substances) and compliant components (typically <500ppm of restricted substances). For levels between 500ppm and 2000ppm, the use of additional techniques may be required to provide discrimination.
The PIN or SiLi detectors also proved efficient at distinguishing compliant and non-compliant systems containing >1000ppm cadmium. Below this level, however, additional techniques may again be required to provide discrimination. The lower RoHS limit for cadmium of 100ppm did result in a number of false detections for this element.
Proportional counter based systems were capable of registering the presence of RoHS - banned elements at levels >3% e.g. such as found in some plastics. Below this level, however, their ability to detect any banned substances was questionable, and their use for such applications is not recommended.
In conclusion, XRF systems offer a viable method of screening for RoHS compliance and tin whisker mitigation. Compared to chemical analysis, these systems offer lower unit and running cost and faster results. Smaller sample sizes are also possible. However, the use of these systems does require at least a semi-skilled operator, who has a sound understanding of the principles of equipment theory and likely composition of materials involved in component and assembly manufacture.