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I have ordered a PCB for my circuit which includes transistor BC548 (Q1), SK100 (Q2) and a Zener diode (D2), but when I got the PCB it has no holes for those three components. Then I searched for SMD type equivalent of those, but their Pins are too distant as compared to my PCB.

So now, should I drill the holes or should I use SMD equivalent? And can somebody suggest the SMD equivalent for these three components according to my PCB imageenter image description here (attached)

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    \$\begingroup\$ Those look like SOT23 pads for Q1 and Q2, no? Anyway, you should probably post your schematic and description of what the circuit is supposed to do. \$\endgroup\$ – mkeith Aug 20 '16 at 6:51
  • \$\begingroup\$ Drilling holes tends to destroy the pads, so don't try that. \$\endgroup\$ – pjc50 Aug 20 '16 at 7:18
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    \$\begingroup\$ Next time you lay out a PCB, you'll know to choose from the different outlines for that transistor, and pick one with holes (TO-92) rather than pads (SOT-23). \$\endgroup\$ – Brian Drummond Aug 20 '16 at 8:34
  • \$\begingroup\$ Thanks @BrianDrummond I will take care of this next time. \$\endgroup\$ – Krishnan Aug 22 '16 at 5:45
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Don't drill holes unless you want to mount the parts on the other side of board. You can use through-hole parts by cutting their leads short and soldering them end-on to the SMD pads.

The SMD equivalent of a BC548 is BC848. Closest equivalent I can think of for the SK100 is BC807 (SMD version of BC327). It's only rated for 45V vs 50V, but this shouldn't be a problem unless your supply voltage is close to the limit. It's smaller power dissipation rating might be a problem, depending on how much current and voltage it has to handle simultaneously.

I can't suggest an equivalent for the Zener diode because you haven't provided the part number for the through-hole version.

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  • \$\begingroup\$ Thanks @bruce for the reply. Zener Diode is of 4.7v/1w. Also the Transistors equivalents, that you have suggested, can be fit properly on the pads given for them? Because as looking into their images, their pins are looking distant as compare to the pads. \$\endgroup\$ – Krishnan Aug 20 '16 at 7:28
  • \$\begingroup\$ DL4732 is 4.7V 1W in MELF package, which may fit your board. Otherwise just use an axial lead Zener, and cut and bend the leads under the body. Transistor leads must be bent to line up with the pads (not that hard, I do it often when making temporary repairs). \$\endgroup\$ – Bruce Abbott Aug 20 '16 at 8:46

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