0
\$\begingroup\$

I have submitted my PCB design to JLCPCB for population. They are asking me if the orientation of my capacitors are correct:

enter image description here

My PCB and schematic of it:

enter image description here

enter image description here

In the datasheet it states that these are non-polarized according to the schematic:

enter image description here

Am I correct? Should I tell them it does not matter which orientation it is in?

The part numbers are as follows:

22uf 16v Kyocera AVX TAJB226K016RNJ (datasheet, LCSC, Footprint, Symbol and 3D model)

10uf 50v KEMET T491X106M050AT (datasheet, LCSC, Footprint, Symbol and 3D model)

UPDATE Changing the caps to the following:

22uf 16v Taiyo Yuden EMK325BJ226MM-P (datasheet, LCSC, Footprint, Symbol and 3D model)

10uf 50v Taiyo Yuden UMK325BJ106KM-P (datasheet, LCSC, Footprint, Symbol and 3D model)

\$\endgroup\$
6
  • \$\begingroup\$ Exactly which capacitors have you specified to be populated on the board? (provide a link to the datasheet and a part number). \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Nov 28, 2023 at 17:19
  • \$\begingroup\$ If you are using non-polarized capacitors, the PCB silkscreen and assembly drawings should not show polarity markings. \$\endgroup\$
    – Peter Bennett
    Commented Nov 28, 2023 at 17:23
  • \$\begingroup\$ The data sheet of a DC/DC converter module does not know which capacitors you have selected to buy and place before and after a DC/DC converter module. You do. You might have selected polarized capacitors, but we don't know which capacitors you have selected to buy as C2 and C3, and that's why they are asking you how to place them, because it's not their job to guess, and they are doing you a service to make sure there are no errors on their side. You must show which capacitors you told them to mount there. \$\endgroup\$
    – Justme
    Commented Nov 28, 2023 at 17:31
  • \$\begingroup\$ Side note: JLCPCB is topnotch. They've reached out to make sure this circuit is correct instead of just printing and sending. \$\endgroup\$
    – earl
    Commented Nov 28, 2023 at 17:41
  • \$\begingroup\$ I updated my OP with those part numbers. \$\endgroup\$
    – StealthRT
    Commented Nov 28, 2023 at 18:44

2 Answers 2

Reset to default
3
\$\begingroup\$

Both of those capacitors are polarized and must be installed in the correct orientation or they will go up in flames.

You have specified tantalum electrolytic parts which are different from those in the manufacturer's datasheet. They have inferior ESR and will not perform as well in this application as those called out by the manufacturer of the DC-DC converter.

\$\endgroup\$
4
  • \$\begingroup\$ It mentions this in the datasheet: Refer to Table 1 for C1 and C2 capacitor values. For certain applications, increased values and/or tantalum or low ESR electrolytic capacitors may also be used instead; \$\endgroup\$
    – StealthRT
    Commented Nov 28, 2023 at 18:56
  • \$\begingroup\$ Yes, they don't suggest using tantalum or low-ESR electrolytic unless you have such a 'certain application' that is suitable (and it's up to you to confirm that it's a suitable application). Because they're generally inferior. In any case, if you want to take a chance with the tantalum caps, getting the polarity correct is essential. As others have said, the PCB should have markings indicating the positive side and the parts should be populated correctly wrt those markings. Replacing the tantalum parts with ceramic X7R or X5R parts will avoid both issues. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Nov 28, 2023 at 19:10
  • \$\begingroup\$ Thanks for the advice. I'll go ahead and change them to UMK325BJ106KM-P and EMK325BJ226MM-P. \$\endgroup\$
    – StealthRT
    Commented Nov 28, 2023 at 19:19
  • \$\begingroup\$ @StealthRT Looks good. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Nov 28, 2023 at 20:03
1
\$\begingroup\$

Well, they need to be in some kind of orientation where the contacts touch the pads...

If they're non-polarized (probably ceramic) the terminals can be positioned either way. Unfortunately, the spec you had mentions the value of the cap, but not the part number. It's possible you chose, for example, tantalum--it's possible one could fit on those footprints. If you give us the part numbers of the caps, we can make sure.

\$\endgroup\$
1
  • \$\begingroup\$ I updated my OP with those part numbers. \$\endgroup\$
    – StealthRT
    Commented Nov 28, 2023 at 18:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.