I'm guessing probably none today. The smartphone business is heavily commodified at this point and there is no "basic components" that be made exclusively only in China. As I noted earlier in my comment, there are over 200 suppliers and subcontractors who set up shops and make basic parts for Samsung in Vietnam. Further, none of the "key" components such as AP, memory, storage, wireless radio, display, or glass, is made in China. Lastly, considering South Korea's recent brouhaha over THAAD, no South Korean company wants any further economic risk from political conflict with China and have been severing their dependency on Chinese suppliers last two years.