Hello!

Please, anyone feel free to correct me if I'm wrong, but I believe that here's how it works:

When you're playing as a Scientific HQ, you can either build buildings the normal way (place non-resource-producing buildings anywhere) and then mine each specifc element, or you can place a non-producing building on top of a resource that it requires (any quality) and that building no longer requires an external source of that good.

For example: as a Scientific HQ, you could put a fuel plant on bare ground, and it would require 1 water. Or, place the fuel plant on any water tile and it will not need to pull that from your stores anymore. Or, for your example. put an electronics producer on a carbon and it no longer needs carbon but still needs aluminum, silicon. etc.

The trade-off for placing a Scientific building on a resource is that you can't mine that resource anymore, which will almost always provide higher yield. But you're also sort of doing both with one claim.

Make sense?

Theoretically if the ground has both input resources then your factory wont need any, otherwise it wont need any of the resource the ground has and you will have to provide the other. The likelyhood of a tile having two resources is already slim, having both resources to be the ones you need - well you'll be looking for that tile over a course of many games.