SAN FRANCISCO — Qualcomm turned up the heat in its high-profile feud with longtime customer Apple, accusing the iPhone maker of feeding proprietary information about Qualcomm chips to rival Intel.

In a court filing made Tuesday, Qualcomm accused Apple of "a multi-year campaign designed to steal Qualcomm's confidential information and trade secrets." The filing alleges that Apple took information provided by Qualcomm software development tools and used to improve the performance and time-to-market of "lower-quality modem chipsets," including those made by Intel.

Qualcomm had been the supplier of baseband chips to every generation of iPhones since the first iPhone debuted in 2007. But the relationship between the two companies turned sour in 2016 over a royalty payment dispute. Last year, the two companies traded lawsuits in multiple venues, including a $1 billion suit filed by Apple against Qualcomm and a separate suit brought by Qualcomm against Apple in San Diego last November.

Teardowns of the latest iPhones announced earlier this month have confirmed that they use Intel modem chipsets exclusively.

In the November suit, Qualcomm alleged that Apple accidentally passed its confidential information to Intel. But Tuesday's filing,which amends the November suit, takes the claim much further, claiming that its analysis of discovery documentation found that Apple has "wrongfully acquired, failed to protect, wrongfully used, wrongfully disclosed and outright stolen" Qualcomm's confidential information and trade secrets and used it to divert its chipset business to Intel.

The filing alleges that Apple engineers working to incorporate Intel chipsets  into Apple devices repeatedly accessed used, and provided to Intel engineers Qualcomm software and confidential information —  including source code — for the purpose of improving the performance of Intel's chipsets

“Once again Apple has flouted its contractual commitments and misappropriated Qualcomm’s property rights in an effort to improve its performance and increase its profits," a Qualcomm spokeswoman said in a statement emailed to EE Times. "The code, tools and design details of Qualcomm’s modem technology which are the subjects of this litigation represent the genius and labors of our dedicated engineers. We have only the rule of law to protect them.”

Apple did not immediately respond to EE Times' request for comment.

The suit is currently scheduled to go to trial next April. 

— Dylan McGrath is the editor-in-chief of EE Times.