Hi As it happens: We're in China and have access to these folks you've mentioned. But careful! Salaries here a raising continuously here so it might be not as cheap as you might expect either. Anyway. I'm working on getting a basic SoC wired together right now with all the essentials inside, so that we can test to boot up a Linux with HDMI output on a RISC-V.
Cheers David
yes i can handle high-speed differential-pairs, now, i know the rules about doing proper impedance matching, and how to create the clearance rules. also i can happily do power-tracks (PMICs), and general layout, no problem.
what i *can't* do is DDR3/DDR4 layouts. or, i can... but you should expect it to take several months and require several iterations. really *really* good people cost around $5k-$10k in china and they can do DDR3 layouts in about 3 weeks flat.
the absolute absolute best teams have access to ultra-expensive simulation software that's specially designed to check DDR3/DDR4 layouts. they're... hell, frankly. DDR4 has got to the point where the length of the bond-wires and the layout of the PCB *inside the fucking chip* has to be taken into account.