Apple’s 5G iPhone will come to market in 2020, a source with knowledge of Apple’s plans says.

Apple plans to use Intel’s 8161 5G modem chip in its 2020 phones. Intel hopes to fabricate the 8161 using its 10-nanometer process, which increases transistor density for more speed and efficiency. If everything goes as planned, Intel will be the sole provider of iPhone modems.

Intel has been working on a precursor to the 8161 called the 8060, which will be used for prototyping and testing the 5G iPhone.

Apple, our source says, has been unhappy with Intel lately. The most likely reason relates to the challenge of solving heat dissipation issues caused by the 8060 modem chip.

Many wireless carriers, including Verizon and AT&T in the U.S., will initially rely on millimeter-wave spectrum (between 28 gigahertz and 39 Ghz) to connect the first 5G phones. But millimeter-wave signal requires some heavy lifting from the modem chips and RF chains, our source explains. This causes the release of higher-than-normal levels of thermal energy inside the phone–so much so that the heat can be felt on the outside of the phone.

The problem also affects battery life. Heat generated by a device component is always converted from electricity stored in the battery.

Our source says Apple’s current issues with Intel are not serious enough to cause Apple to reopen conversations with Qualcomm about supplying 5G modems. Qualcomm’s X50 modem has also created heat dissipation problems for other smartphone OEMs developing smartphones that support millimeter wave 5G.