These chips ain't cheap.

Qualcomm filed a lawsuit Wednesday against Apple's iPhone manufacturers that alleges breach of contract. The suit, filed in US District Court in California, comes less than a month after Apple stopped paying patent royalties to the chip company.

Apple's manufacturers, such as Foxconn, used to pay Qualcomm for the intellectual property rights to make chips that connect phones online. The legal battle between Apple and Qualcomm has been heating up as the two companies brawl over who has licensing rights to the processor technology.

"Our license agreements with Apple's manufacturers remain valid and enforceable," Don Rosenberg, Qualcomm's general counsel said in a statement. "The manufacturers must continue to live up to their obligations under these agreements and Apple should immediately cease its tortious interference."

Qualcomm argues that the manufacturers acknowledge they have a contractual obligation to pay royalties to chipmakers but that they need to follow Apple's orders against paying. The two companies have sued and countersued each other since January.

Apple said that Qualcomm has "refused to negotiate fair terms" and decided to stop paying until a judge can determine how much it should cough up in royalties.

"Qualcomm's demands are unreasonable and they have been charging higher rates based on our innovation, not their own," an Apple spokesman said.