Apple is reportedly planning to use an advanced System on Integrated Chip packaging technology for the M5 chips in production.
The SoIC system was developed in 2018 by TSMC. This technology allows chip stacking in three dimensional arrangement for better thermal management as well as electrical performance compared to the conventional two dimensional chip structures.

Apple has extended its collaboration with TSMC for the production of the next generation hybrid package with the addition of molding technology utilizing thermoplastic carbon fiber composite, with plans to mass produce the chips for AI servers and Macs by next year and the following year, 2026.
Mentions of what is expected to be the Apple M5 Chip are found in the official code. It’s believed that the AI Cloud servers are run by the M2 ultra chips, and that the M5 is Apple’s step to future proof their supply chain integration for AI functionalities.