The accusation is in a report published by the Dutch multinational research institute Somo and GoodElectronics.
Both organisations are involved in trying to improve working conditions in low-wage countries.
Somo reports that the workers, mainly women, in the Philippines and Thailand are forced to work overtime and during national holidays.
It added that workers in Thailand,there are also too few measures for safeguarding the workers.
NXP claims that the a 12-hour day is perfectly normal in the chip industry. Apparently the unions disagree.
NXP has 27,000 workers, 3,000 of whom work in the Netherlands, it is not clear if the Dutch workers are expected to work 12 hours, although we suspect not.
For those who came in late, NXP Semiconductors provides mixed signal and standard RF, analogue, power management, interface, security and digital processing chips. It is one of those which has done rather well with the boom in mobile tech. It made US$ 5.647 Billion in 2014 and was so flush it bought Freescale.