EC (embedded controller) firmware runs the keyboard controller, power sequencing, battery charging and fans. Depending on the board it lives in a separate chip (ENE KB9012, ITE IT85xx, Nuvoton NPCE) or inside the main SPI image, so check which applies before flashing.

Tools to open these files

Format	What it is	Open with
.7z	7-Zip archive	7-Zip or WinRAR
.brd	.brd boardview (Test_Link format)	OpenBoardView, FlexBV or BoardViewer
.rar	RAR archive	7-Zip or WinRAR