Sensitive electronic components can be mounted on a printed circuit board within an electronic device. To isolate a sensitive component from stresses that may arise during an unintended impact event, the electronic component can be isolated using a groove in the printed circuit board. The electronic component may be mounted to a component mounting region using solder balls. The component mounting region may be surrounded on some or all sides by the groove. Flex circuit structures that bridge the groove or a portion of the rigid printed circuit board may be used to hold the component mounting region in place. The flex circuit structures may be provided in the form of separate structures or may be provided as an integral portion of the printed circuit board.