The real trade with china didn't begin until silver mining took off in the 1550s. Before that, spices and the trade with the 'indies'(India) were the primary trading interests. Most maps didn't even get the eastern half of the Indian ocean correct until the mid-1600s and from the east the pacific ocean was a mystery for longer.

Silver was the item that the chinese intensively desired for monetary reasons as multiple experiments with paper money failed due to runaway inflation and they lacked precious metals of their own. Almost 40% of the silver mined in the late 16th century ended up in china.