A customer called into the EMPF Helpline asking for testing to confirm RoHS compliance...

A Tier-Two Electronic Manufacturing Service (EMS) provider, located in the Mid-Atlantic region, recently received a multi-million dollar contract to build RoHS compliant product.  This contract required the procurement and integration of an electronic sub-assembly into the main product from a third party EMS provider.  In order to certify the end product was manufactured to meet RoHS requirements, the EMPF was solicited to provide non-destructive inspection of the electronic assemblies of the third party EMS provider. 

The recommended testing to be performed was X-ray Fluorescence (XRF) which has the capability to complete an elemental analysis without damaging the electronic assembly.  XRF operates through the emission of characteristic secondary x-rays by exciting lower level electrons to “jump” out of their orbit into higher orbits.  This change leaves the atom unstable resulting in higher level electrons dropping down to these lower level orbits while simultaneously emitting photons equal to the difference between the two orbitals involved.  The energy radiated is characteristic of the element under testing which is observed by a detector.  XRF can be used for RoHS compliance by verifying the elements in solder or on pads on the electronic assembly.  There are limitations to XRF analysis.  Lighter elements have less detection sensitivity and the possibility of x-ray absorption by the area surrounding the test location exists.  In the case of Pb, which is a heavier element, sensitivity is not an issue.  The particular XRF instrument used has the ability to minimize the energy absorbed by the surrounding area by focusing the beam onto the location chosen for examination.      

After reviewing the provided electronic assembly, the EMPF was able to quickly determine if the assembly process incorporated a SnPb solder by examining the solder joints and fiducials on the assembly.  Figure 2-1 represents a solder joint on the electronic assembly while Figure 2-2 represents solder on the fiducial.  The fiducial was examined for base line testing.  Pb is the peak at approximately 10 keV and Sn is the peak at approximately 25 keV.  

The customer was given the captured images in a one day turnaround and was able to discuss with their third party EMS provider the issues with their manufacturing processes. 

In conclusion, XRF testing indicated that lead (Pb) was found in the solder joint of this product.  The use of lead (Pb) demonstrates this electronic assembly’s non-compliance with RoHS.