Testing ball welding

[GGMM]

Hello,

Simple question:

Can we test with Jtag probe or other that all weld ball connections are correct on a component? (ex Cyclone III). -->Impossible to be seen

In addition, can we test auxiliary components connected to others connected to a Jtag chain (ex Ram connected to a blackfin)?

Not simple and of course without any scheme...

cdt