Layout Tipps & Tricks
Soldering / soldering processes
In order to produce a mechanically and electrically reliable brazed joint, time and temperature are required. Soldering does not produce a metallurgical joint as in welding, but instead creates a joint in which different alloys or metals diffuse into each other. This creates an intermetallic phase (IMP). The goal is to achieve the ideal thickness of this IMP. If it is too narrow, a cold solder joint results; if it is too thick, it becomes brittle.
Here, the layout lays the foundation for the subsequent achievement of an optimal solder joint, especially with regard to heat requirements, connection surfaces and heat input or heat dissipation. There are various methods for soldering, but a nitrogen tunnel is used in all machine soldering processes to achieve the best possible soldering result.
###IMAGE1### In wave soldering, the assembled component to be soldered is transported over a solder wave (=turbulent bath) of liquid tin. Beforehand, flux is applied from below, which is activated in the preheating phase. This breaks down existing oxide layers and heats the assembly to the required base temperature. This is followed by soldering and cooling of the assembly.
Wave soldering is used to solder THT components on the TOP side and SMT components on the BOT side. SMT components on the BOT side must first be bonded to the PCB in an upstream process step.
Design parameters for soldering THT components
For an ideal pad design for THT components, the manufacturer's data sheet should be consulted as the first point of reference, which describes how the footprint should be designed. However, this should always be questioned critically, as the proposed designs are not always optimal!
Rule of thumb for pad diameter: pad to hole ratio = 1.5 but rest ring min 0.25mm
Rule of thumb hole diameter: max. wire diameter +0.2 to 0.6 mm
Tips and tricks from 30 years of experience in electronics production can be found in our EMS Design Guide.
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