Today we're going to show you three different ways that we solder electronic components to printed circuit boards. We'll talk about three different forms of solder and three forms of flux - a material that removes any oxidation and prepares the metal areas to be bonded. So the first technique is called reflow. This is used for surface mount technology (or SMT) components. For this we use solder paste - a paste of flux with tiny balls of solder suspended in it. The paste is applied to the board with a stencil and the components are stuck into the paste using a robotic pick-and-place system. Then the board goes into the reflow oven. This is a convection oven with multiple different temperature zones inside. In the oven the board is slowly heated and the flux goes to work until the solder beads melt and flow into place then cool and solidify. To do a double-sided SMT board you do one side and then flip it over and repeat the process. On the second pass we don't let the bottom side get quite as hot, but the solder will flow again so experienced board designers know to put all the heavier components on the "top" side as a matter of design for manufacturing. The second technique is wave solder where we have a wave of molten solder for the boards to pass through. This is used for through-hole and mixed technology boards. As boards go in, the underside is sprayed with flux and as the board travels through the machine it is slowly heated and the flux mostly evaporates before the board passes through the molten solder wave - actually several different kinds of controlled waves - to completely fill in all areas of the board. For double-sided boards to be wave soldered you place the SMT components first, on one side, using glue to hold them in place and then place the through-hole components on the other side. The SMT components go through on the underside and get soldered in the wave along with the through-hole pins. For both reflow and wave solder we'll use a thermal profiler to program the different temperature zones. We need to ensure that all areas of the board reach the proper temperature for the right amount of time for optimal soldering without overheating. At Z-AXIS we create and store a unique profile for each board design we run, showing temperature versus time for multiple areas on the board as it travels through the oven or wave solder. Finally some components are best hand soldered. The flux is usually in the core of the solder wire. We hand solder components like lithium batteries that can't go in the ovens or tall, tippy parts. We may also hand solder parts like this using a fixture to hold a tight tolerance on mounting angle. Everyone involved in soldering should be trained to IPC standards. There is an initial 40-hour classroom training course with re-certification every two years. It includes an online exam through IPC and a hands-on exam in which participants assemble a test board and have their work assessed by a certified trainer. At Z-AXIS we have a certified trainer on staff for both IPC-A-610 and IPC J-STD training. There's a lot more to soldering than we can show in a short video - for example, leaded versus lead-free solder, water-soluble versus no-clean flux, how to do thermal profiling, and many other considerations. See our related videos or contact us to learn more.