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Using 0805 on 0603

Posted: Wed Nov 21, 2012 7:21 pm
by msj121
I have an 0603 capacitor pad, and it was designed for 100uF. Sadly, they are not available on digikey, so I am looking to put an 0805 part 0603, do you think its possible? Has anyone tried this?

Re: Using 0805 on 0603

Posted: Wed Nov 21, 2012 9:00 pm
by skimask
Yep, tombstoned a 1206 on a 0603 pad with a chunk of wire running down to the other pad. Worked good enough for me.
And whatever you do, don't tell us what type of capacitor...

Re: Using 0805 on 0603

Posted: Wed Nov 21, 2012 9:11 pm
by Duane Degn
Attached is an image from DipTrace for pads of 0603 (C1) and 0805 (C2) caps.

I'm betting the 0805 will work on the 0603 pads.
SmtCaps121121a.PNG

Re: Using 0805 on 0603

Posted: Wed Nov 21, 2012 9:59 pm
by MichaelN
Yep, I've soldered 0805 directly to 0603 pads a bunch of times without issue. The largest capacitance I can see in a 0603 package is 68uF, 4V tantalum at Mouser:
http://au.mouser.com/ProductDetail/Nich ... a3z4Cso%3d

Re: Using 0805 on 0603

Posted: Wed Nov 21, 2012 10:42 pm
by msj121
Yes, I was looking for 100uF in MLCC preferably, sorry skimask for not mentioning the type.
Thank you guys so much, sadly I still can't find MLCC in 0805, but I was able to find Tantalum in 0805, I might try to put a Tantalum and MLCC in parallel, we shall see. I will look more into this tomorrow, if anyone has further advice, I would appreciate it.

Sadly I already ordered a couple of boards, but this hack might need to do for now.

Re: Using 0805 on 0603

Posted: Wed Nov 21, 2012 11:25 pm
by Mee_n_Mac
Whenever I hear tantalum caps I am concerned about surge currents causing failures. I don't know your usage but 100 uF says to me power supply which in turn implies potentially large surge currents. I would advise you to read up on tantalums in whatever usage you design entails.

http://www.ryston.cz/pdf/avx/solid_ti.pdf

Re: Using 0805 on 0603

Posted: Wed Nov 21, 2012 11:42 pm
by MichaelN
Mee_n_Mac wrote:Whenever I hear tantalum caps I am concerned about surge currents causing failures.
I agree - I don't use them in my designs, and only use electrolytics when the capacitance is too great for ceramics.

In msj121's case, if 100uF is really needed, I’d suggest figuring out a way to mount a 1206 package, as there are plenty of 100uF ceramic caps in that size. Maybe glue to the PCB adjacent the pads and run solder bridges.

Re: Using 0805 on 0603

Posted: Thu Nov 22, 2012 6:38 am
by msj121
Yes, if I used a 100uF tantalum cap, I would likely use a 0.01uF cap in parallel.

Sadly, it is a tight board and I am not sure I will have room for 1206, I will try to check, someone (GSM man) pointed out to me digikey has 0805 MLCC, so that will help a lot.

On a side note, I have found 100uF 0603 MLCC from Alibaba, is that a trustworthy place to buy components? Meaning, are the components I buy likely what I will even get (will I open up the package to find 100nF?), and are the components even usable for prototyping or for professional use? The part that scares me is that the part is pretty cheap, less than $1 which is a surprise, and as little as 10 cents.

Re: Using 0805 on 0603

Posted: Thu Nov 22, 2012 7:03 am
by MichaelN
msj121 wrote:On a side note, I have found 100uF 0603 MLCC from Alibaba, is that a trustworthy place to buy components?
It can be if you're careful, but when they are claiming something that big capacitor companies like Kemet and AVX don't come close to (100uF MLCC in 0603 package), then I'd say it's too good to be true.