This file extension was added to our database by a visitor to this site, but no further information was provided. We have yet to investigate the sch file extension any further, or there was simply not enough information available at the time to report accurately on this format.
However, it is possible that other file formats exist that use the sch extension, so please let us know if you do not think this extension matches the file format you are looking for.
.SCH files are used to hold schematic diagrams for the ExpressSCH program available for free from ExpressPCB. It is used to create schematics that feed into the companies free PCB layout program ExpressPCB. No details on the internals of these files is know to me.