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SOT223; Joining pad to tab

Former Member

Hi folks.

 

I'm having a problem with using the tab on SOT223 voltage regulators that use the tab as a heatsink and is usually the same connection as the centre pin. But when I add a  polygon around it to increase the surface area, it either leaves the centre pin disconnected or the tab is isolated.

 

Is there a nice way to achieve this?

 

Thank you.

  • 0 in reply to autodeskguest

    I have tried other components with this method and it seems simple with those, but I'm sure I was trying the same thing with the two I mentioned, and it just wasn't working. The main difference I see is that the others have the tab numbered 4, so if this is present, then there is no problem. The problem seems to start when the tab is not numbered. Maybe I just found an awkward couple. If you want to check other sot223 devices to find one without that number 4 tab, and try connecting to it.

     

    Well I have learned a lot more by confronting a problem and finding helpful people, and I am still a novice with Eagle, so I expect I will be back with more dumb questions.image

     

    Thank you all for your help.

  • 0 in reply to Former Member

    Am 14.12.2014 um 12:39 schrieb Richard Perkins.:

    I have tried other components with this method and it seems simple with

    those, but I'm sure I was trying the same thing with the two I

    mentioned, and it just wasn't working. The main difference I see is that

    the others have the tab numbered 4, so if this is present, then there is

    no problem. The problem seems to start when the tab is not numbered.

    Maybe I just found an awkward couple. If you want to check other sot223

    devices to find one without that number 4 tab, and try connecting to it.

     

    Well I have learned a lot more by confronting a problem and finding

    helpful people, and I am still a novice with Eagle, so I expect I will

    be back with more dumb questions.:^0

     

    Thank you all for your help.

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/134754

     

     

    PADs are what you see in the board and in the packages, PINs are what

    you see in the schematic and the symbols. You can connect multiple PADs

    to one PIN. This will solve your problem. It has to be done in zthe LBR

    editor. If you want to have a heatsink copper area around a PAD without

    thermals, just draw a polygon in the board and give it the same name as

    the signal the PAD is connected to, and uncheck 'Thermals'. You will see

    the checkbox by activating 'INFO' and clicking on the poly.

    Ever tried 'help connect', 'help poly' etc?

    And, after all, it would be a really good idea to read the manual...