The deionized water is a stupid idea, I don't know what I was thinking... too hard to maintain purity if there is any metal at all in the cooling loop.
If one COULD manage to keep deionized water pure in a WC setup, sealing the die would not be an issue. Otherwise, any metal particles would corrode the traces connecting the die to the substrate.
I know next to nothing about sealants and adhesives, but I would suppose the problem is maintaining the seal between the die and substrate under heat and pressure. Sealing the package itself should be no problem; since it is organic (porous), almost any sealant is likely to adhere. But (I am assuming) the silicon die is not porous, making it hard for a sealant to adhere.
What about a mechanical sealant? An O-ring, shaped to fit around the die?
A precisely made top could fit flush over the die, and not leak if the gap between the die and top was small enough.
Here's another one: Machine out a hole in a baseplate just barely smaller then the CPU die, to be positioned over the die. (A small?) clamping pressure would keep any water from flowing between the die and baseplate, yet water could still be impinged in most of the die's surface.
I can make a diagram if there are any questions as to what I am describing.
I am still determined to test this concept myself, I just need advice on the appropriate course of actions to take. As demonstrated, there are many possible ways to accomplish direct die cooling (theoretically), but which is most feasible?
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