[SOLVED] SMD cap footprint wrong ?

[CataM]

Hello everyone,

I have downloaded from "ultralibrarian.com" the UCZ1V221MCL1GS SMD capacitor footprint for Altium.

From the datasheet, I read that "UCZ 1V 221 MCL1GS" is diameter=10mm x L=10mm and standard type (because the bolded CL means standard in the datasheet).
Then, I go to the recommended land pattern and I read: X=2.5mm , Y=4mm and a=4mm.

From the footprint from ultralibrarian.com shows 2.1mm height, 3.9mm long and 4.3mm distance between pads (corresponding to the "a" above).

**broken link removed**

Datasheet: http://nichicon-us.com/english/products/pdfs/e-ucz.pdf
Recommended land pattern: http://www.nichicon.co.jp/english/products/pdfs/e-ch_ref.pdf
Digikey reference: http://www.digikey.es/product-detail/es/nichicon/UCZ1V221MCL1GS/493-4322-1-ND/2533889

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Here is another one. I have downloaded the UCZ1E102MNQ1MS SMD cap footprint from "componentsearchengine.com".

From the datasheet, I read that "UCZ 1E 102 MNQ1MS" is diameter=12.5mm x L=13.5mm (also it is standard type because of "NQ").
From the recommended land pattern, I read: 4, 7.5 and 7mm for the X,Y and "a" respectively.

The footprint provided fells short in this one also, see picture:


Am I wrong ? Otherwise, what is going on with this guys ? I am surely wrong in something because it is difficult for those guys to get short in an easy footprint.

Kindly tell your taughts.

P.D.: Attached ".rar" contains schematic symbol and footprint from the mentioned websites for Altium.

 

[barry]

Not sure what your problem is. Looking at the first one, the Nichicon recommended footprint is very close to the ultralibrarian one you cite (your link didn't work, btw). There's not a lot of difference between 3.9mm and 4mm. There's no 'absolute' correct value for a footprint. It's definitely worthwhile checking that the device will fit properly on the footprint, but I don't see anything wrong here (I only looked at the first one.)

 

[FvM]

The 12.5mm footprint looks basically correct, too.

 

[CataM]

Here is the 1st picture that does not work in post #1:

The 12.5mm footprint looks basically correct, too.

O.K. I can go with the 1st one, but definitely not with the 2nd one because they are falling way too short.
Distance between pads they are using is ~3.5mm against recommended 7mm (the "a" parameter).

Not sure what your problem is

The problem I have is that I do not understand how does someone come up with those numbers (e.g. 5.9mm for the length of the pad of the 2nd cap, when the recommended is 7.5mm) instead of using the numbers recommended by the manufacturer.

- - - Updated - - -

From the datasheet, I read that "UCZ 1E 102 MNQ1MS" is diameter=12.5mm x L=13.5mm (also it is standard type because of "NQ").
From the recommended land pattern, I read: 4, 7.5 and 7mm for the X,Y and "a" respectively.

That cap has the 11th digit "Q", so the recommended land parameters are: 2, 7.3 and 3mm for the X,Y and "a" respectively. It is closer to the one given by the web site.

 

[marce]

Go read and learn about IPC-7351 then you will understand how a footprint is developed...