I’m working on a computer monitor’s power board (to replace a capacitor or two, which I assume is the problem), and found these:

board with caps

Replacements are easy to find, so no issues there, but I’m curious why the SMD aluminum electrolytic capacitors are on little platforms (or spacers). To buffer swelling maybe?

stock smd image

  • 2
    \$\begingroup\$ Isolating the metal case from traces/pads that may run underneath it. This is really only a problem for SMD caps, the lead-style ones naturally have a buffer due to the leads. \$\endgroup\$
    – Ron Beyer
    Feb 20 '20 at 16:36
  • \$\begingroup\$ With the faulty capacitors you have removed carefully remove the base. What can you see.<br> I suspect the casing could touch both pads on the PCB and is conductive. \$\endgroup\$ Feb 20 '20 at 19:36
  • \$\begingroup\$ @WarrenHill Probably right. I’ll take a look when I remove them. I had to order some replacements, so I left them on the board for the time being. \$\endgroup\$ Feb 20 '20 at 19:39

Those capacitors are really made similarly to the cylindrical radial lead through-hole capacitors. Two connections come out through a rubber bung (in an aluminum case that is crimped at the bottom to form a seal) and those leads are bend to form SMT leads.

From this Nichicon website (a conductive polymer type is shown, and conventional electrolytics are similar):

enter image description here

The plastic base is just there to provide physical support for the capacitor can so it doesn't flop around too much on the leads.


The base is for support plus when soldering it is a large object which would insulate heat. Same if you ever had to solder a ball grid array chip. Also these bigger capacitor are normally connected to a power connection again soaking heat away.

  • \$\begingroup\$ How does a plastic base "soak heat away" from the capacitor? Are you saying that a BGA chip has (or should have) a plastic base? \$\endgroup\$ Feb 22 '20 at 13:46

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