The series 120 4mm2 TM reed relay range has attracted a lot of interest since being released in July. It requires a board area of only 4 mm x 4 mm, making it the highest packing density currently available, taking up the smallest board area ever. Two switch types are a general purpose sputtered ruthenium switch rated at 15 Watts, 1 Amp (3 Volt version) or 20 Watts, 1 Amp (5 & 12 Volt versions) and a low level sputtered ruthenium switch rated at 107 Watts, 0.5 Amps.
These are the same reed switches that are used in many other ranges but are orientated vertically within the package, allowing this very high density. The small size of the package does not allow an internal diode. Back EMF suppression diodes are included in many relay drivers but if they are not, and depending on your drive methods, these may have to be provided externally.
The relays feature an internal mu-metal magnetic screen, which has the advantage of a high permeability and low magnetic remanence and eliminates problems that would otherwise occur due to magnetic interaction. Relays of this small size without magnetic screening would be totally unsuitable for applications where dense packing is required.