has anyone tried adding leads to SMD caps?

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pucho812

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I need a lot of axial caps for a project and they are pricy. I can get the same values in radial for less money but they don't fit. So I am thinking maybe do SMD and long leads. I can't imagine it not working. Has anyone ever tried. It would clear physical space as well as be less expensive. for example a cap value I need in axial is 6-7 dollars each VS it's SMD value at 2-3 each. Both known brands of caps.
 

JohnRoberts

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Axial caps were falling out of fashion decades ago because they consumed so much PCB real estate. In a pinch I have bent radial cap leads to fit in place of axial cap lead spacing.

JR
 

Khron

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Fitting them to the other side of the board is not an option?

You maaaaaaaybe could get away with soldering one end of the smd capacitor to the existing pad, and then only need to tack on one wire-leg, instead of two.

But I guess it depends largely on what you decide that your time and effort is worth...
 

JohnRoberts

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You can lay down the radial so it's body is roughly in the same location as the axial would be. Then bend the leads to go where they need to go. This is not ideal of course. My gut feeling is to make the grounded lead the long one.

Back last century a major capacitor maker confided to me that Peavey was their largest US customer for axial capacitors. We had machine insertion capability for both axial and radial caps, but radial caps used less PCB real estate.

JR

PS: I recall back in the day taking an axial capacitor from a new low cost vendor apart to kick the tires and finding a radial cap secreted inside with the leads bent to route out both ends like an axial cap. Modern caps were physically smaller so it was possible to fit in.
 

abbey road d enfer

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So I am thinking maybe do SMD and long leads. I can't imagine it not working. Has anyone ever tried.
Actually I just have, not with caps but with resistors. It's a 100 Meg resistor. I ordered them in SMD because they were instantly avaialble, compared to the axial, which took a couple of weeks to be delivered.
So I soldered one end to a pad and a strand of wire at the other end. It took me about 5 minutes to do it right. I wouldn't even think of doing that repeatedly.
 

pucho812

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All excellent suggestions. Sadly I can’t fit them to the underside of the pcb, sadly I can’t lay them flat in some positions as it’s multiple axial caps next to each other.
Things I have had to do in the past.
I like the idea of solder an smd part to the pad and then one lead.
That is definitely an option.
 

Phantasm

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chilidawg

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You may find small 1 component only SMT adaptor PCB that you can fit the SMT cap to then wire that to the main PCB perhaps. Not sure about this particular component but have seen a variety of PCBs for prototyping so you may get on better with that. You may be able to butcher something like this into use:- https://www.mouser.co.uk/ProductDetail/SchmartBoard/204-0021-01?qs=WfBYDmZgvZISmYE57SOtDw==
for 6 quid a piece, I'd rather make my own tiny SMD caps to axial adapter board. $10 for 10 pcs of 4" x 4" dual layer PCB should yield more than a hundred of such tiny boards.
 

Phantasm

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for 6 quid a piece, I'd rather make my own tiny SMD caps to axial adapter board. $10 for 10 pcs of 4" x 4" dual layer PCB should yield more than a hundred of such tiny boards.
Yes agree, not a cheap option - just mentioned incase it was useful
 

Electrobumps

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this can work, but it might be hard to keep the SMD in place. I would super glue the SMD to the board. Then solder the legs and then connect the cut the legs to size and solder to the SMD. Maybe worth trying it on a scrap board with a cheap SMD part before you commit.
 

babisbabis

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Blue caps look familiar. Chemicon LXE/LXZ? :)
I didn't even notice what caps they were... I just put them like this to show that it's possible and relatively easy to use radial ones as axial :)

Edit: Funny thing is that I'm searching for them now to check them but I can't find them...
Always the same thing happens...
 
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CJ

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I had to cut some Matantz dual caps in half and wire in two 6800/80 volt caps (plus minus center tap ground) What a pain scraping the plastic guts out of those cans without screwing them up. Could build a board with four caps but boss wants it retro.

You can find cheap axials if you shop around.
 

abbey road d enfer

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this can work, but it might be hard to keep the SMD in place. I would super glue the SMD to the board. Then solder the legs and then connect the cut the legs to size and solder to the SMD. Maybe worth trying it on a scrap board with a cheap SMD part before you commit.
You don't need to do that. Solder one of the ends of the resistor/capacitor/inductor to one of the pads, so you don't need to anchor it, then connect the little piece of wire between the remaining end and the remaining pad.
 

Khron

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You don't need to do that. Solder one of the ends of the resistor/capacitor/inductor to one of the pads, so you don't need to anchor it, then connect the little piece of wire between the remaining end and the remaining pad.

Fitting them to the other side of the board is not an option?

You maaaaaaaybe could get away with soldering one end of the smd capacitor to the existing pad, and then only need to tack on one wire-leg, instead of two.

But I guess it depends largely on what you decide that your time and effort is worth...

Yup...
 

Electrobumps

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You don't need to do that. Solder one of the ends of the resistor/capacitor/inductor to one of the pads, so you don't need to anchor it, then connect the little piece of wire between the remaining end and the remaining pad.
Soldering direct to the pad is a good idea and you don't need to anchor. However in my experience of soldering SMD's is it a pain they are not designed to be hand soldered. They like to stick to the iron. I would still use a tiny dab of super glue to save my frustration and time chasing a tiny little SMD around. Otherwise you need 3 hands, one to hold the iron, one to hold the tweezers to keep the SMD in place and one to feed a tiny bit of solder. Yes you can tin the component and pad then solder without any reflow, but this can create a dry or weak joint. When holding such a small component with tweezers there is risk of movement post heat which is more likely to create a dry joint. If the SMD can not move the risk is removed.

My point is it will probably make the OP's life easier if you fix it in position before soldering and the likely hood of a dry joint will be less. You could use something less permanent like Blue Tac. Or they might be a solder ninja and this is not required.
 
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Khron

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Soldering direct to the pad is a good idea and you don't need to anchor. However in my experience of soldering SMD's is it a pain they are not designed to be hand soldered. They like to stick to the iron. I would still use a tiny dab of super glue to save my frustration and time chasing a tiny little SMD around. Otherwise you need 3 hands, one to hold the iron, one to hold the tweezers to keep the SMD in place and one to feed a tiny bit of solder. Yes you can tin the component and pad then solder without any reflow, but this can create a dry or weak joint. When holding such a small component with tweezers there is risk of movement post heat which is more likely to create a dry joint. If the SMD can not move the risk is removed.

My point is it will probably make the OP's life easier if you fix it in position before soldering and the likely hood of a dry joint will be less. You could use something less permanent like Blue Tac. Or they might be a solder ninja and this is not required.

... Or you can put some flux (either tacky flux paste, or from a flux pen) on the pad first...

Where there's a will, there's a way ;)
 
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