Medtronic's Chinese headquarters in Shanghai, China. (Glen Stubbe/Minneapolis Star Tribune/MCT)

Medtronic, the Minnesota-based health care product manufacturer, plans to buy Mansfield's Covidien and move its base overseas to save on federal taxes. But that's not the only controversy facing the corporate giant.

Since 2006, the company that manufactures a wide array of pacemakers, defibrillators and other medical products has paid tens of millions of dollars in settlements on charges it violated federal law by paying illegal kickbacks to doctors to promote its products.