To best visualize the factors effecting resolution, carry in your minds eye an image of a light shadow being cast on the wall using a flashlight. The size of the flashlight filament would be the analagous x-ray "focal spot" The smoothness and/or roughness of the wall would be the intrinsic x-ray camera resolution. The intensity of the light, analagous to the kV. If the wall is very smooth, we can postion the structure close to or touching the wall and get a very sharp shadow on the wall, independent of the size of the filament. If the wall is rough, then we have to move the structure towards the light to geometrically magnify the smallest features to a size greater than the roughness texture. As you move the structure towards the filament, you now observe penubric blurring of the shadow and unless you can move the flashlight very far away, you then must use a smaller filament. Try this experiment yourself and you will begin to understand the inter-relationship of focal spot size, camera resolution, image magnification and tube voltage (kV) This understanding is the prerequisite for making an intelligent purchase decision on x-ray inspection systems.
Taking a different tact to get at an answer to the original question, if applications such as general, BGA attach, and die attach inspection require a resolution of 10 units. What would you suggest are the minimum resolutions for the following:
* uBGA and flipchip attach and wire bond inspection
For the applications you mention you would probably want to resolve details of at least 8 microns (0.0003") which would translate into a bare minimum resolution requirement of 60 to 100 line pairs per millimeter at a minimum geometric magnification of about 100X.