Mounting of moulded AFM probes by soldering

Electrical probes consisting of cantilever beams with integrated pyramidal metal or diamond tips have to be mounted to small holder chips before they can be used in electrical atomic force microscopy (AFM). Gluing procedures have been developed for this step but such a connection suffers mainly from low electrical conductivity and often also from low mechanical stability. Furthermore, it is not very suitable for massfabrication. Soldering is a well-established mounting method in microelectronics (e.g. surface mounted devices (SMD)) and could overcome these problems. Therefore, we have developed a soldering procedure for moulded AFM probes. This paper presents the optimized soldering procedure and demonstrates its use for probe mounting. Excellent results were obtained using a metallization system of Ti:W+Ni+Au and a SnBi58 solder paste in combination with a hotplate for the soldering step. The soldered probes are highly conductive and the mechanical connection between probe and holder chip is very rigid. They show clear resonance peaks in tapping mode AFM which we could not obtain with our glued probes before.