I'm just wondering why this schottky diode have three pins? enter image description here

I know two of the pins acts like rectifier but what does the a third pin do?



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    \$\begingroup\$ Take a look at the datasheet... \$\endgroup\$ – stefandz Oct 13 '15 at 12:40
  • \$\begingroup\$ Have a look at the datasheet, pin 2 is floating \$\endgroup\$ – Bimpelrekkie Oct 13 '15 at 12:40
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    \$\begingroup\$ For the diode in question, nothing semicon.panasonic.co.jp/ds4/DB3J208K_E.pdf. It's a reasonable question though why some SMD diodes are packaged like this. That's in fact not too different than the (more general) recent hot question: electronics.stackexchange.com/questions/194693/… \$\endgroup\$ – Fizz Oct 13 '15 at 12:57
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    \$\begingroup\$ @Olin - The datasheet tells that pin 2 is not connected (NC) but doesn't say why the three pin package is used instead of a two pin one. The question isn't dumb nor directly answered in the datasheet at all. \$\endgroup\$ – Ricardo Oct 13 '15 at 13:58
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    \$\begingroup\$ @Ricardo The OP asked what the third pin does, which is answered directly in the datasheet. If he didn't know why some packages have N/C pins, he should have done a little research before asking here. Those answers were also right in front of him. This was a question that could be answered easily if he'd done a little bit of research first. \$\endgroup\$ – DerStrom8 Oct 13 '15 at 14:27

In general, single diodes in 3-lead SM packages have no connection on the third pin. This is a fairly common practice in the industry.

I don't have a solid answer as to 'why' they do this, but will share a few possibilities for debate:

  • You cannot install a single diode in a 3-lead package with reverse polarity because of the asymmetry of the package; if the diode were in an 'inline' 2-lead SM package (like SOD323) there is a chance of reverse installation

  • 3-lead packages are larger, allowing for larger die sizes (better thermal performance), easier installation by pick-and-place machinery (generally, the smaller the part, the trickier installation is) and easier optical inspection

  • \$\begingroup\$ possibility to add a heatsink \$\endgroup\$ – YoussefDir Feb 29 '20 at 13:35
  • \$\begingroup\$ Far too small for practical heatsinking in my opinion. Also with dense SM layout you would not likely be able to route much copper to it, and if you connect the pin to a heavy internal copper layer with vias you would have a very hard time soldering that pin properly. \$\endgroup\$ – Adam Lawrence Mar 2 '20 at 15:33

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