I need to buy a selective soldering machine for a process that is currently Sn/Pb, but I know that soon I will need to switch to lead-free. I cannot wait until that time and I need to purchase a system now. Can these machines be converted for minimal cost in the future or will I need a new machine? What do I need to be concerned with when purchasing a machine that can solder lead-free?

To convert a soldering machine to lead-free after the fact can be very expensive. Some machines cannot be converted and a new machine must be purchased. If you are sure you will need to run two alloys eventually, the best solution is to purchase a machine now that can do both later. There are machines available that can solder both Sn/Pb and lead-free simultaneously with no changeover. In fact, this is one of the driving factors for purchasing selective solder equipment, i.e. flexibility. It is important to realize how much flexibility you need prior to making any purchase. If you want to run dual alloys, then a dual pot system is the best choice. These types of systems can still be configured with multiple nozzles in each pot for optimum flexibility. In the lead-free side you may have a 4 mm and 8 mm nozzle and on the Sn/Pb side you could have the same configuration or something similar. The goal is to have the most flexible machine as possible to maximize throughput and solderability not only on the day the machine arrives but also in the months and years to come.

As far as what you need to plan for regarding lead-free, flexible process parameters and reliable nitrogen control over the nozzle are key factors. Programmable heated nitrogen at the nozzle is usually a must when soldering lead-free, especially on thick boards or boards with heavy grounds, high number of layers, or other thermally challenged boards. The machine should also configurable with any type of pre-heat that may be necessary on all future products. In most cases, heated nitrogen at the nozzle will be sufficient.