Low energy X-Ray can also be used to check for some forms of liquid contamination on PCB's. Most notably, battery electrolyte.
If a PCB or piece of equipment has suffered a battery leakage event the leaked electrolyte shows up as more dense than plastic or FR4 PCB material. The effect you see is like wisps of smoke across surfaces, concentrated dense areas where the fluid has collected or soaked into a paper label (as in this case). Corrosion can also lead to a ball of 'corroded stuff' that spall's off of the PCB and floats around inside the equipment causing general havoc if it gets across component leads etc as it is conductive.
This capability lead to my discovering that a used mini remote control that i recently purchased had suffered battery leakage that got onto the PCB. I was already aware that a battery had leaked as one spring terminal had some classic corrosion on it. What I could not see was how far the corrosion had traveled and whether it was on the PCB. The remote is a real PITA to dismantle and as it might have to go back to the seller for exchange, I decided to X-Ray it to see what electrolyte was visible and where it was located.
I have ringed areas of electrolyte contamination and possible corrosion spalling on the attached images.
The seller was impressed by the images and is sending me a new remote along with his sincere apology. The unit had been placed in the 'OK' pile rather than the 'bin' pile when sorting through his stock.
UPDATE: I have added a reference image of the other , non corroded, remote control. The paper label in the battery compartment can be seen but none of the corrosion evidence that was seen on the damaged unit is present. Its always useful to have a known good reference unit during an
X-Ray examination for battery leakage.
Fraser