This thesis is focused on high temperature electronics and how the reliability of solder can be improved for high temperature applications using nanoparticles. Therefore this thesis first investigates a method of using cross-section polishing (CSP) based on argon ion milling to cross section the sample without damaging it. This research will show that this method is very effective in cross-sectioning the delicate samples and allowing embedded nanoparticles to be detected. Once this method of detecting nanoparticles is established, the thesis reports on an investigation into nano-composite solders. This part of the thesis will show that passive Silica (SiO2) nanoparticles can be added to solder to improve room temperature creep resistance of the solder. Compression tests at room temperature and elevated temperature were performed to compare the mechanical characteristics of normal solder and nano-enhanced solder. Compressed samples were cross-sectioned to investigate their microstructure. Results show that while nanoparticles are effective in improving creep resistance of the solder at room temperature, the efficiency of nanoparticles decreases with increasing the temperature. Finally the thesis reports on attempts to combine solders with highly reactive nanoparticles, focussing on the fundamental property of dissolution of thin aluminium layers in solder. As aluminium is highly reactive with oxygen, the main thrust of this chapter is to generate a method to avoid the oxidation of aluminium prior to introducing molten tin to it. After introducing molten tin to aluminium thin films, samples were cross-sectioned by CSP to examine the thickness of the remaining aluminium layer by scanning electron microscopy (SEM). Results did not allow accurate determination of the dissolution rate of aluminium in molten tin and the likely reasons for this are discussed.