Simpson Thacher & Bartlett, Jones Day and Lee and Li are advising on Chinese state-backed chip maker Tsinghua Unigroup’s proposal to purchase a 25 percent stake in Taiwan chip packaging and testing firm Powertech Technology Inc.

The $600 million deal, which is pending approval from Powertech’s shareholders and Chinese and Taiwanese regulatory authorities, would make Tsinghua Unigroup the largest shareholder in Powertech.

A Simpson Thacher team led by Hong Kong partners Chris Lin and Jin-Hyuk Park is representing Tsinghua Unigroup.

Lee and Li and Jones Day are advising Tsinghua and Powertech, respectively, on Taiwanese law. 

Powertech said in a statement that the move will help expand its global market share as a chip assembly and tester, and allow it to vertically integrate with the semiconductor businesses of Tsinghua Unigroup.

Powertech’s main operations are in Taiwan and it employs more than 11,000 on the island, which is around 90 percent of the company's total staffing.