ABSTRACT
Research into three-dimensional (3D) electronics has continued for more than three decades and a very large number of techniques have been studied. But, there has been relatively little commercial exploitation for volume applications. A number of 3D computing systems have been realized, using both multi-chip modules and stacked wafers or dice. A 3D implementation of the Associative String Processor is described by R. M. Lea et al. This implementation uses the Irvine Sensors technology in which each layer consists of a die which is ‘re-routed’ so that connections to each layer are brought out to one or, as in this case, two edges. Systems using directly stacked chips are more difficult to cool because the substrates are generally thin and have low thermal conductivity. This makes it difficult to thermally connect a heatsink so that the centre of the cube is efficiently cooled.
