[sdiy] SMD part availability, manufacture

Seb Francis seb at burnit.co.uk
Wed Nov 12 16:12:32 CET 2008

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.

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?

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 

I'm assuming PCB headers will have to be thru-hole.

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?


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