Author Topic: SMD cap alternative - motherboard has extra set of pads  (Read 433 times)

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Offline sirlemonhead

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SMD cap alternative - motherboard has extra set of pads
« on: March 29, 2019, 07:05:00 am »
Hi,

I have an old computer motherboard from 1992 and I've just removed all the SMD capacitors as they were leaking, with the aim to replace them. I've noticed that each capacitor seems to have a second set of much larger pads. I've tested these for continuity and they appear to be alternative capacitor pads.

You can see them here - the thin rectangular pads are from the original caps, the larger square ones are either to the side of or above/below the original pads.

See picture:
https://www.dropbox.com/s/1ryd6329nvzidxh/dellsmdcaps.jpg - pardon the flux gunk/residue

I was wondering - why is this? Is this designed for an alternative capacitor type? If there were MLCCs or something longer lasting I could put on that would be great, especially as some of the alternative pads are oriented in much easier to access spaces than the original pads!

Thanks!
 

Offline wraper

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Re: SMD cap alternative - motherboard has extra set of pads
« Reply #1 on: March 29, 2019, 07:08:14 am »
Most likely they are for tantalum SMD capacitors.
 

Offline pbarton

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Re: SMD cap alternative - motherboard has extra set of pads
« Reply #2 on: March 29, 2019, 07:56:04 am »
To reduce component sourcing risks...…
https://www.eetimes.com/document.asp?doc_id=1121949#
 

Offline LateLesley

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Re: SMD cap alternative - motherboard has extra set of pads
« Reply #3 on: March 29, 2019, 08:14:50 am »
To reduce component sourcing risks...…
https://www.eetimes.com/document.asp?doc_id=1121949#

That's a very old article from June 1999.
Capacitor prices on the rise again
By Bettyann Liotta, 06.18.99
 

Offline pbarton

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Re: SMD cap alternative - motherboard has extra set of pads
« Reply #4 on: March 29, 2019, 08:47:52 am »
That's a very old computer motherboard.
The ‘buyers’ in manufacturers ‘Material Supply’ departments frequently experienced difficulty in securing supplies of certain components during the late 1990’s.
It’s not uncommon to find that PCB layouts were designed to accommodate equivalent or substitute parts.
« Last Edit: March 29, 2019, 07:34:58 pm by pbarton »
 
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Offline sirlemonhead

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Re: SMD cap alternative - motherboard has extra set of pads
« Reply #5 on: April 03, 2019, 06:36:22 am »
Thanks, that's good to know!

Would I be best off just using electrolytics? or is there anything else I can use worth considering over them or the tantalums?
 

Offline Rasz

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Re: SMD cap alternative - motherboard has extra set of pads
« Reply #6 on: April 24, 2019, 02:27:40 am »
Who logs in to gdm? Not I, said the duck.
My fireplace is on fire, but in all the wrong places.
 
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