Author Topic: Vias on pads / metalized holes  (Read 1769 times)

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Offline fskyTopic starter

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Vias on pads / metalized holes
« on: October 09, 2015, 09:57:03 am »
Hello!

Look at the examples below.
I don't really get why they use vias on metallized holes or pads like that.
Is this connected with heat distribution? Does they make it to allow substrate to heat up evenly on both sides,
thus reducing the risk of copper pad to fall off during soldering of large components? Or maybe it's rather for something in connection with high current conduction? If I'm right, is it the only reason?

I got a THT component footprint with those vias and because I was not able to do such small ones it made me wonder if it's actually necessary. Any ideas :) ?

 

Offline RobertHolcombe

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Re: Vias on pads / metalized holes
« Reply #1 on: October 09, 2015, 12:00:09 pm »
Mounting holes are *generally* connected to the ground plane of the board. Vias offer redundancy in connecting to the ground plane as the hole plating can be damaged by screw threads and the pads can be ripped off either side, but they also strengthen the hole against over tightened fasteners which would otherwise crush PCB.

I'm not sure about the first picture as it appears to be a component lead so may well be to act as a heatsink, but its hard to say without a wider FoV
 

Offline peter.mitchell

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Re: Vias on pads / metalized holes
« Reply #2 on: October 09, 2015, 12:22:55 pm »
vias add mechanical strength to pads when soldered, the solder plugs the vias, going through the board anchoring the top part of the pad to the bottom part, thus anchoring the leg to both the top and bottom side of the board.
 

Offline fskyTopic starter

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Re: Vias on pads / metalized holes
« Reply #3 on: October 09, 2015, 02:42:41 pm »
One of the attached pictures is a foto of a hall effect current sensor, ACS756. Those leads are only a low resistance copper conductor, so I doubt the power dissipation is an issue here. However, maybe the footprint has those holes for mechanical strengthening, as mentioned before, given the size of the device (so maybe it could be affected by high vibrations). Thank you for your ideas :)
 


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