Prehistoric technology Ground and polished stone tools continued to be created and used during the Neolithic period. Numeric record keeping evolved from a system of counting using small clay tokens that began in Sumer about 8000 BC. The Stone Age developed into the Bronze Age after the Neolithic Revolution. The Neolithic Revolution involved radical changes in agricultural technology which included development of agriculture, animal domestication, and the adoption of permanent settlements. The Bronze Age is characterised by metal smelting of copper and its alloy bronze, an alloy of tin and copper, to create implements and weapons. Polished stone tools continued to be
Tin-silver-copper The melting point of SAC alloys is 217–220 °C, or about 34 °C higher than the melting point of the eutectic tin-lead (63/37) alloy. This requires peak temperatures in the range of 235–245 °C to achieve wetting and wicking. Some of the components susceptible to SAC assembly temperatures are electrolytic capacitors, connectors, opto-electronics, and older style plastic components. However, a number of companies have started offering 260 °C compatible components to meet the requirements of Pb-free solders. iNEMI has proposed that a good target for development purposes would be around 260 °C. Also, SAC solders are alloyed with a larger