X-Ray is a very effective Non-Destructive tool that can be used to “look Inside” a semiconductor to see if the lead frame, bonding wires and chip architecture is uniform across a sampling of components in receiving inspection.
X-Ray used in concert with other inspection tools like De-encapsulation and X-Ray Fluorescence offers visibility that would be impossible if just visual inspection techniques are employed.
Acid Etch De-encapsulation
“De-Cap” is an excellent tool to actually read what is on the Die of a chip. Of course this method is a Destructive test as a section of the package is removed to allow examination of the die marking.
Once the authenticity of the die is verified, the remaining parts in the lot can be x-rayed and the mechanical characteristics compared to the exemplary device.
X-Ray Fluorescence (XRF)
X-Ray Flourescence (XRF) is the emission of characteristic “secondary” (or fluorescent) X-rays from material that has been excited by bombarding with high energy gamma rays.
The phenomenon is used for elemental analysis particularly to discover compliance to RoHs requirements and the presence or absence of elements such as Lead(Pb),Mercury(Hg), Cadmium(Cd), Polybrominated Bipenyls(PBB and Polybrominated diphenal ether (PBDE).
Some customers can only accept components which are made with a Lead/Tin process (Leaded) and oterhs run a lead free design and can not accept any product containing lead.
Without XRF it would be impossible to differentiate between compliant and noncompliant parts.