https://wccftech.com/galaxy-s10-exynos-variants-slp-circuit-boards/

If you’re unfamiliar with the term SLP or Substrate Like PCB, let us give you a recap. The iPhone X launched last year used a Substrate Like PCB, which allowed the flagship to free up space and accommodate other things like a larger battery plus different components to allow for better technology to be used. Samsung’s upcoming Galaxy S10 lineup is also expected to feature the same circuit boards, but according to the latest information, only those featuring the Exynos chipsets will get them.

Another attribute of SLP motherboards is that they are able to package the chips tightly together. As a result, this reduces their overall size, leaving space for manufacturers to place the more important components. This would include the battery. With battery technology being stagnant as ever, it makes sense for manufacturers to use other approaches and improve technology from different categories rather than wait for a breakthrough to come forth.