2 - Soldering methods, solder joint design

Wave soldering is a popular automated soldering method for through-hole components, where both the heat and the solder are provided by the solder wave. After the component placement, the flux is deposited to the bottom side of the PCB; the assembly is preheated and then immersed into the molten solder wave.

The board is moved through the soldering system by a conveyor with a speed of ca 1.3–1.5 m/min, to get the right thermal profile. The total length of the thermal profile is usually about 60 seconds, whereas the peak temperature is about 30 °C higher than the melting point of the solder alloy.

The wave soldering is discussed in details in Section 6.

In reflow soldering, the solder in a paste form is deposited at first onto the PCB. Then, the board is populated with components, and the assembly is placed into / transported through a reflow oven to melt the alloy in the solder paste. The soldering is usually carried out in a convection and/or infrared type oven, heated by hot air or N₂ gas. Fast heating is necessary above the melting point to avoid the formation of thick intermetallic layers.

The total length of the thermal profile is usually about 240 seconds, whereas the peak temperature is about 30 °C higher than the melting point of the solder alloy.

The reflow soldering is discussed in details in Section 3, in Section 4 and in Section 5.