[Alneyan]

To answer your specific question Bbq, a given shot will target components based on their relative hitpoints, where smaller components (ie with fewer hitpoints) are less likely to be hit than bigger components. The exception is for armour, where smaller pieces are more likely to be destroyed first; an Armour III (50kt) will usually be destroyed before a Scattering Armour III (150kt).

So, if your damage has been applied to the ECM device, and there remain 90 points of damage, another component will be selected, and destroyed if possible. If you still have some damage points, they will go to yet another component, until the selected component cannot be destroyed. Once you reach this point, the damage left will be "partial damage", and will be added to the damage of your next hit on this ship. Note that this partial damage is not located in a specific component, as components are either destroyed or intact.

I do not know if 40 partial damage would add to, say, a shot from an Ionic Disperser; "Only Component" weapons do not deal partial damage, but do they use up partial damage, when there is some still present on the ship? It would probably not matter, save for the sake of completiveness, but...