Pb footprint SMD transistor

I developed a PCB with components on both sides.
I use SMD components classics (Capacitor, resistor) and also SMD transistors.
When I implanted the components on the B-side, I used the “Change Side” option.
Everything went well, no design error. The components are well connected to the good pins of the transistor.
Nevertheless, the 3D view gives a bad sense to the transistor as if the base and emeter were inverted. It is therefore unusable in the state.
So what happens? Imprint a classic SOT 23 Handsolder.


Une explication?


I did a test by doing the same manipulation and the same fingerprint and it works. Don’t get it!
You’ll see that 1 and 2 are well reversed, which is not my case.


SOT-23 is an annoying package. There is no real consensus of where pin 1 on that package is located.

Maybe you can trace it back to some unreadable fax somewhere in the 80’ies.
This screenshot you posted is the most common pinout, and therefore that is what KiCad uses.

The MMBT3904 from the screenshot below seems to have a more fitting pinout for your requirement.

Some datasheet manufactures omit the pin numbering of SOT-23 altogether, and that leads to situations of showing a 3D model with C, B, & E as in the picture you posted.

In the end it’s up to you to make the right combination of schematic symbol and footprint.

Normally using the other side, pins 1 and 2 must be reversed on view 3 D.
That is not the case.
There may be a problem with the fingerprint used. I don’t know where.
I ran another test with another print, it works.
I’m going to go over this again, and then I’m going to go over it again , but happy to have seen it before manufacture


It is not clear to me what you are trying to say.

The PCB view (with black background) does not have the pin numbers visible. Red looks like the mirror image (apart from some details) and I think that is your intention.

However, when you turn the PCB around in the 3D viewer you are still looking at real parts from the top side. And therefore you do not see a mirror image.

Yup, PCB view is looking through the PCB while 3D view is like holding the PCB

You can get the bottom view in the pcb editor from View -> Flip Board View. Then the top layer is mirrored and the bottom layer looks like how it’s in the 3D view. But as Paul and Naib said, you don’t get the same mirroring effect in the 3D view because you don’t look through the board.

The schematic was one I retrieved from the Internet. I did the test on a transistor using the design and the official footprint of the MBT3904. It works. Only disadvantage, I am obliged to take the tracks and implantation because of necessity pins 1 and 2 are inverted. Seen 3D finally correct.
I’m gonna go over each transistor and actually change the footprint to have a little bigger pads for welding.
thank’s for your answers

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