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Why should vias be placed not too close to the SMT pads?
For SMT pads with a surface area equal to or less than 0.8 x 0.8 mm, the risk of assembly defects due to Via in Pad capillary action is very high. Our first advice here is to avoid this type of Via in Pad entirely, if at all possible, as it will unavoidably complicate your project’s assembly.
Should thermal vias be tented?
Vias that are also in close proximity to SMT pads should also be tented. This will prevent the solder paste from wicking into the via and creating a poor solder joint. This is especially important with dogbone style BGA escaping.
Should thermal vias be filled with solder?
Designers may leave the bottom copper plane exposed. However, studies have shown that this has minimal impact on thermal performance. TI recommends placing thermal vias in the solder mask defined thermal pad to effectively transfer heat from the top copper layer of the PCB to the inner or bottom copper layers.
Can you put a via under a pad?
With via in pad, the drill hole for the via is inside the pad. This means you can not tent the via with soldermask. Leaving the via open to allow the paste to wick into the barrel will cause reliability problems during manufacturing.
What is Viapad?
In PCB design, via refers to a pad with a plated hole that connects copper tracks from one layer of the board to other layer(s). High-density multi-layer PCBs may have blind vias, which are visible only on one surface, or buried vias, which are visible on neither, normally referred to as micro vias.
What is a plugged via?
Via plugging is a process in which vias are completely filled with resin or closed with a solder mask. Via plugging is done as a preventive measure to secure the vias from the unwanted flow of solder material during the assembly/soldering process.
What is a thermal via?
Thermal vias are—very simply—holes located under a surface-mounted heat source in a circuit board that allow heat transfer. Simple vias or via-in-pad can provide a large reduction in thermal resistance. The number and position of thermal vias has a direct impact on thermal resistance.
What is a blind via?
A blind Via connects exactly one outer layer with one or more inner layers. A buried via is a via between at least two inner layers, which is not visible from the outer layers. This technology allows more functionality in less board space (packing density).
Can you put a via on a pad?
Via in pad is the design practice of placing a via in the copper landing pad of a component. Compared to standard PCB via routing, via in pad allows a design to use smaller component pitch sizes and further reduce the PCBs overall size.