Qualcomm Inc. has launched a unit to help Chinese smartphone makers sell overseas, part of efforts to build stronger relationships in the country following a long-running antitrust case.

The move is part of the U.S. chip maker’s efforts to prove itself a valuable partner in China at a time when Beijing is trying to reduce its reliance on foreign makers of chips and other technology. Qualcomm draws about half of its revenue from customers in China, but the company has run into a series of challenges there.

...