Every electronic company buyer or electronic hobbies is always looking for low cost printed circuit board in China. Indeed, it is really cheap even there is express courier cost included. But there are thousands of PCB companies in China, how to choose a right one?
What is the criteria of right PCBs supplier?
Reasonable price, good quality, express production and well communication.
Now the cost of PCB is highly transparent. You can find many through B2B website. You can always find a lowest offer from PCB suppliers. However everything has there cost, is it possible that 2 layers PCBs only cost USD 10? I don't think you don't dare to use it as the components cost is more than it, but the worst is you have to spend much much more time to solve the PCBs trouble. So don't be focus on price only, you will pay for it.
Quality is the most buyer asking for. So what is the good quality of PCBs? The basic of good quality requirements are solder mask hard enough, circuitry is no open circuit, no short circuit, PTH is smooth enough. A lot of suppliers factory is no dustless room, so you can imagine what will you get if you pay only USD 10.
For sampling PCBs, most suppliers will offer AOL checking and fly probe testing.