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Just saw these type of capacitors for the first time and I'm curious :

  1. Why do they have this additional block of plastic around them? Some kind of shielding?
  2. Is there some specific reason they didn't just use the normal "can" type of electrolytics?
  3. What type of capacitors are these? Are they still electrolytic?

capacitors

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    \$\begingroup\$ SMD? pick and place? Probably hard to do both with electrolytic cans. plastic doesn't shield. \$\endgroup\$
    – dandavis
    Jan 26, 2021 at 20:14
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    \$\begingroup\$ They look like they are SMD electrolytics, so the case is there to allow for vacuum pickup, mounting stability, and as a frame to hold the leads. Will probably also help with vibration resistance. \$\endgroup\$
    – Jon
    Jan 26, 2021 at 20:15
  • \$\begingroup\$ Thanks...SMD? I found SMT (Surface Mount Technology) but not SMD. I'm reading a wikipedia article now (en.wikipedia.org/wiki/Pick-and-place_machine) but even it doesn't mention what SMD means. \$\endgroup\$
    – raddevus
    Jan 26, 2021 at 20:17
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    \$\begingroup\$ SMD = surface-mount device, it's the same thing \$\endgroup\$
    – user253751
    Jan 26, 2021 at 20:17
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    \$\begingroup\$ How peculiar... \$\endgroup\$
    – DKNguyen
    Jan 26, 2021 at 21:09

1 Answer 1

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Why do they have this additional block of plastic around them? Some kind of shielding?

The plastic is to make them flat so they can be placed by SMT assembly machines. Electrolytic capacitors are round and SMT machines need something flat to work with.

Is there some specific reason they didn't just use the normal "can" type of electrolytics?

They are a normal 'can' but the pads are SMT pads, it is an alternate way of packaging them. The other way that is typically seed to package electrolytics for SMT purposes looks like this: enter image description here

The two SMT pads are below and there is a flat top which makes it easier for vacuum chucks to move it.

What type of capacitors are these? Are they still electrolytic?

Most likely electrolytic.

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    \$\begingroup\$ Is there any advantage or disadvantage to producing and/or mounting them in the plastic shell shown in the question, vs the more standard packaging pictured in your answer? The plastic would add more expense, which would explain why they are so rare - what would be a valid use-case for the plastic ones? \$\endgroup\$
    – Ian Kemp
    Jan 27, 2021 at 10:48
  • \$\begingroup\$ @IanKemp You could probably broaden the question in the last sentence to just "what would be a valid use-case for low-voltage low-value electrolytics." Not much, these days. (I'm assuming the "4.7" value in the OP's picture is microfarads) \$\endgroup\$
    – alephzero
    Aug 19, 2021 at 23:26

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