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Author Topic: Are snap-in capacitors solderable?  (Read 7491 times)
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solutions
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« on: July 05, 2015, 02:49:22 14:49 »

Anyone done it successfully? Both lead and non-Pb solders are of interest, preferably the latter.

I don't have any on hand and am thinking about doing a PCB design. But, until that's started (if it's started), then done, I'm not going to order any Coke cans to experiment on, since they cost more than lunch money.

thanks in advance
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pickit2
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« Reply #1 on: July 05, 2015, 04:54:00 16:54 »

Snap-in capacitors,  I thought they had bent connectors a way to hold them in place when assembling the pcb, before soldering.
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solutions
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« Reply #2 on: July 05, 2015, 09:28:50 21:28 »

They are normally not soldered, which is why I asked.

There's a tradeoff, as with anything else, of connection reliability and being able to easily replace failed caps (easy as changing a fuse).
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Magnox
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« Reply #3 on: July 05, 2015, 09:52:26 21:52 »

I've never seen snap-in capacitors not soldered. Everything I've seen about them says the bent pins are to hold the capacitor to the board prior to soldering, as Pickit said.

From EPCOS datasheet (just one I pulled completey at random):

"Snap-in solder pins to hold component in place on PC-board"

(emphasis mine)
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crunx
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« Reply #4 on: July 05, 2015, 09:55:09 21:55 »

I used some snap-ins many years ago, and they were soldered after mounting. But because it is long time ago, I can't remember if there were some pre-cautions or similar.

If you give one example of supplier name & part number, I could check what the manufacturer claims.

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cup58
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« Reply #5 on: July 08, 2015, 02:00:36 02:00 »

In my experience, all the snap-in capacitors I've seen were, without a single exception, soldered to the PC board where they were installed. The only ones I've seen sometimes not soldered to a PC board were capacitors with screw terminals.
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CocaCola
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« Reply #6 on: July 08, 2015, 11:13:40 23:13 »

When I was working at Motorola there was still one manual insertion and legacy wave solder line running that was used for some legacy products...  On occasion when they ran out of snap ins they would switch over to traditional legged caps and they never had much success getting them through the wave solder machine without about half of them needing manual reorientation due to them tipping over during the wave soldering process...

It's my understanding that the snap in legs are simply there to hold the part properly on the board prior to soldering, not a replacement for soldering...
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optikon
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« Reply #7 on: July 08, 2015, 11:59:43 23:59 »

interesting comments ...... seems there is somewhat of a consensus that snap style caps are for temporary holding prior to the permanent soldering in place.

While I have not worked with snap in style capacitors, I can add that even "press-fit" style components (like connectors) also get regularly soldered.
"Press-fit" being the style that requires a tool to mount the component by pushing the pins into the socket/PTH so firmly, that a gas-tight connection is made.
After years of operating in a high vibration environment, even these can come loose/crack and so they are pressed-in and then soldered for added reliability.

I can't imagine one of those giant capacitors staying in place long with just a "loose" snap-in that could be done by hand?

Maybe its ok for the prototype that sits on your bench for years though as a one -off..

(I've always imagined how much energy storage you could get from a big array of those things..., charge it up then short it with a crowbar)
« Last Edit: July 09, 2015, 12:02:08 00:02 by optikon » Logged

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pickit2
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« Reply #8 on: July 09, 2015, 12:36:42 00:36 »

while doing prototype work 30 years ago it was common practice when wire-wrapping a pcb, to also soldering the joint.
some kit even got in to the field, the fail rate was very high for those that had soldered wire-wrap joints, and most failures was in the joint, the failures that was wire-wrapped only was less then 1 in 50 and zero joint failures. 
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CocaCola
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« Reply #9 on: July 09, 2015, 03:47:10 03:47 »

the fail rate was very high for those that had soldered wire-wrap joints

I wonder how much of that could be attributed to improper or bad soldering and/or solder incapable plating on the wrap post...

In the end in some applications wire wrapping or other mechanical connections can be just as good if not better (arguable of course) than solder...
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crunx
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« Reply #10 on: July 09, 2015, 07:29:35 07:29 »

"Once in a time" a.k.a "long ago" I worked a lot with wire-wrapped prototypes and short production series. The dual-in-line ICs were socketed on a universal board, with just ground and voltage pins soldered to their respective buses. All of the signal wiring was by wire-wrap. We never soldered the WW connections.

That time we also used a lot of snap-in electrolytic capacitors, which were either hand-soldered or wave-soldered.

In general, the wire-wrap joints virtually never failed, if the work was done right. Especially stripping the wire by inexperienced person using wrong stripping tool, or similar. As all that happened many years ago and in a different company, now defunct, I have no exact reliability figures to refer to.

Also I can't remember any special problems with snap-in capacitors, rather contrary: They were quite convenient, as they kept well in place during pre-soldering handling, unlike some other heavy and tall parts with conventional soldering terminals. And I believe we never even tried to use them without soldering first. Not even for short-term lab tests, as the contact resistance would have been quite high and unstable.

A summary: Wire-wrap is not intended to be soldered, but snap-in is intended to be soldered. Don't do the opposite!
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