Edit: I think using the term "bus" might be wrong here. A "bus" needs to be large enough to facilitate an entire DDR4 stick's bandwidth to the Northbridge. The connection to each individual pin probably doesn't count as a "bus", maybe "pin" in the right term?
I'm sure data busses and pins differ in size, I suspect depending on how much current needs to flow through them. Household foil is roughly 0.016 mm thick. Can a connection pin between RAM and the motherboard be that thin?
Since this is an odd question that depends a lot on the scenario, probably, I'll explain the context. I'm starting to get my feet wet on the subject of computer engineering purely for the reason that I want to prove an idea is possible. So I decided to just try it. Worst case scenario I try something too difficult and learn something in the process. My idea is a micro-controller which physically intercepts the DDR4 RAM slot of a desktop PC with a thin sleeve. Like so:
Figure 1: Interceptor Sleeve, a paper-thin layered sleeve sits between the RAM slot and the motherboard. Normally, the Interceptor sleeve completes the connection between the RAM stick and Motherboard without interference. However, a transistor along this connection allows frames (or whatever they're called with busses to DDR4, I'm only familiar with the simpler CAN bus so far) from the motherboard to be conditionally intercepted by and replied to artificially, without passing the frame further. Likewise, while connections from the motherboard are being are being intercepted for a specific address range, the Interceptor can send its own frames over the RAM connector to read or write. In this way, the system can read and write to specific memory ranges while allowing
I only plan to test this with one single pin on the RAM at first.
Nevertheless, I grabbed a powered down mobo and RAM and found that three layers of foil could fit between an inserted RAM stick and the connection. So if a bus/pin can be as thin as tinfoil, those three layers should be the equivalent of a pin, insulator, and the other "side" of the pin as shown in Figure 1.