[sdiy] SMD part availability, manufacture

Anthony Rolando goldenechos at hotmail.com
Wed Nov 12 17:21:23 CET 2008




> Date: Wed, 12 Nov 2008 15:12:32 +0000
> From: seb at burnit.co.uk
> To: synth-diy at dropmix.xs4all.nl
> Subject: [sdiy] SMD part availability, manufacture
> 
> So, continuing with my thoughts for a generic digital module PCB, I'm 
> wondering now about availability of parts in SMD, specifically:
> 
> Odd resistor values - the balanced analog I/O of the CODEC IC I'm 
> planning to use calls for some quite obscure resistor values such as:  
> 634R, 715R, 1K33, 2K32, 4K42.Or am I simply reading the datasheet too 
> literally and when using 1% resistors the nearest standard E24 values 
> will be close enough? - in some cases maybe.

All of these values are available from Xicon, 1% sizes 0402-1206

> 
> Decent capacitors in nF sizes - for the 4xD I used polypropylene caps in 
> the range 1.5nF to 6.8nF and low-K 470pF ceramic discs.  Are these kind 
> of caps available in SMD?

low-k 470pf ceramics, those are no problem... but I am not sure what you could use for the polypropylenes.


> 
> And what about power supply components like regulators and large 
> electrolytics?  I've seen SMD regulators but I'm not sure how easy it 
> would be to heatsink these.  And large electrolytics are surely all 
> through-hole?
> 
> I'm assuming PCB headers will have to be thru-hole.

I prefer thru-hole headers. Easier to assemble by hand. Though reading further down, it seems you might not be doing that! There are some pretty large value electrolytic in surface mount packages. These are sometimes annoying to solder by hand, but not too much a problem.

Tony

> 
> If at some point I go the route of selling pre-populated PCBs, I'm 
> wondering what are the implications of using some thru-hole components 
> for automatic manufacture?  Do these then have to be soldering by hand?
> 
> Seb
> 
> 
> 
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