Ion beam induced charge (IBIC) microscopy provides a means of imaging the depletion layers of working microelectronic devices beneath their thick metallization and passivation layers. The concept of IBIC microscopy is outlined, its advantages over optical and electron microscopy techniques are described, and examples of images are presented. One particular application is as a way of identifying device components that are susceptible to having their logic state altered by cosmic rays when used in satellites, for example.