used for coupling signals to and from the asic 31 and the image device 32 through the wafer the metal routing on both sides of interposer 30 means that the position of output pads on imaging device 32 must not necessarily match those on the asic 31 this is referred to as redistribution with u201c fan in fan out u201d of routings connections between the vias 33 and the asic 31 is via contact bumps 34 on bottom surface of the asic and routing structures 35 suitably in the form of narrow metallizations on the interposer 30 the bumps 34 are shown to be elliptical only for the purpose of distinguishing them from the vias in the figure only a few of the routings 35 have been indicated for clarity in the part of the interposer labelled digital and 39 separated from the part labelled analogue by means of the barriers 38 see further below there are arranged a plurality of u201c i o u201d bumps 36 these bumps are connected to external control devices not shown for digital control of the asic 31 routing metallizations 35 connect the bumps 36 to the contact bumps 34 on the asic 31 in the other part of the interposer labelled analogue there are also a plurality of u201c i o u201d.