A method for building scalable electronic subsystems is described. Stackable modules employ copper substrates with solder connections between modules, and a ball grid array interface is provided at the bottom of the stack. A cooling channel is optionally provided between each pair of modules. Each module is re-workable because all integrated circuit attachments within the module employ re-workable flip chip connectors. Also, defective modules can be removed from the stack by directing hot inert gas at externally accessible solder connections.