Diff between two vias in image

Discussion in 'General Electronics Chat' started by Vindhyachal Takniki, Sep 10, 2016.

  1. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
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    1. Attached is the image of two different vias on two pcb's. Second pcb(green) have vias designed by me in ultiboard, it has a drill & pad diameter as metal layer around each via.

    2. First board(blue), has different vias. It dont have any metal/cu on top. What is this type of via?

    3. How to create it? Is there any different between two or one ia better than another?

    4. These vias are only used for current transfer from one layer to another..
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    The convention is a via is used as a connection only and has a solder mask covering, as opposed to a plated thru hole (PTH) used to hold and connect a thru lead, where a pad is exposed on both sides.

    Neither is better.
     
  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    We called it masked or unmasked vias. And actually my manufacturer says that there is a difference in reliability especially with small vias, beacuse with the mask over them there could be leftover chemical solution inside the via that the mask prevents from being washed out, so it could eat away the copper in a few years and make unreliable connection.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Vindhyachal Takniki and ErnieM like this.
  5. ian field

    Distinguished Member

    Oct 27, 2012
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    Clustered vias are often used for heat transfer - under a SMD LED would be a convenient example.

    Can also be for very low resistance ground planes in multilayer boards, if its more about fitting as many vias as possible than soldering anything to them - they may not have much in the way of solder pads.
     
  6. SLK001

    Well-Known Member

    Nov 29, 2011
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    The blue board has plenty of metal/cu on the top. The only difference between these vias, is that one is tented (has a solder mask over them) and one is not. How it is created depends on the PCB layout program. Some programs have a "mask" setting that under the setting the vias are masked and over the setting the vias are open.

    Vias are not only used for signal/current transfer from one layer to another, but, as ian_field mentioned, also heat transfer.
     
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