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I'm trying to save board space used up by regular cartridge fuses. An horizontal fuse holder for those occupies about 27×10mm in my board (vertical mount is not an option). An obvious solution seems to be replacing those by automotive blade fuses:

enter image description here

The mini fuse above is 10.9 × 3.6mm, so mounting a horizontal holder like this would save me a lot of space. So this solution seems good. In fact, too good: now I'm wondering why I don't see automotive blade fuses in PCBs everywhere. Are there disadvantages to this kind of fuse, when compared to regular cartridge fuses? Is there some reason (mechanical, perhaps) for not mounting blade fuse holders directly on PCBs?

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    \$\begingroup\$ SMD fuses are smaller used in HDD’s AMD so are SMD polyfuses. \$\endgroup\$ – Sunnyskyguy EE75 May 16 '18 at 16:56
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    \$\begingroup\$ User serviceability is often not a priority, so most of the time people use SMT fuses, which are much smaller, like Tony said. If user serviceability IS a priority, the fuse should be panel mount or something like that. Not on the PCB, where disassembly is required to gain access. \$\endgroup\$ – mkeith May 16 '18 at 17:04
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    \$\begingroup\$ I see them on a lot of places. While that doesn't mean it is a great thing, it at least means it is acceptable by some standards. I see them most often in UPSs \$\endgroup\$ – PlasmaHH May 16 '18 at 17:07
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    \$\begingroup\$ If you wanted to field service or by the user in the fuse is external, but if you want to support the salaries of field technicians to open it up then you make the fuse internal. \$\endgroup\$ – Sunnyskyguy EE75 May 16 '18 at 17:15
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    \$\begingroup\$ I’ve actually put an 80 A automotive maxi fuse soldered though hole just like the one you are describing in mass production. Only issue was to find one where the plastic didn’t melt in the soldering process and milling down the potrution (spelling?) on the bottom side once soldered. \$\endgroup\$ – winny May 16 '18 at 17:36
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I've seen them in aircraft-grade inverters on the high-current DC side, directly soldered to the board (actually a number in parallel as PCB protection- IIRC 5 or 6 20A fuses in parallel off the 28V bus).

Reasons they are not widely used:

  • They're too high current for many purposes- the standard starts at 1A, and 2A is the next one up.
  • They're only rated for low voltage, so useless for mains applications. Few applications outside of automotive and other lead-acid battery based applications are high current and less than 32VDC (there are some higher voltage ones designed for automotive applications with higher voltage electrical systems- rated 58V for use on 42VDC systems (but the automotive applications have not caught on as much as expected AFAIK (correct me if wrong), so I would be a bit cautious about those).
  • One-time fuses are not preferably compared to other means of protection; they're most useful for wiring protection.

They do have some good features- easy availability and high (1000A) interrupting capacity being a couple, so if your application fits I don't see a lot of downside.

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  • \$\begingroup\$ Thanks for accepting the answer, however it's usually a good idea to give it a day or so in case someone else comes up with a better answer. For example, there might be a fuse engineer lurking here, you never know. \$\endgroup\$ – Spehro Pefhany May 16 '18 at 17:47
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    \$\begingroup\$ ook, will keep that in mind next time \$\endgroup\$ – FrancoVS May 17 '18 at 10:32

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