Bob Axtell wrote:
> Yes. In fact you will have trouble locating assembly houses that will do
> this (unless it is only one or
> two caps or resistors)..
>
> The reasons are myriad, but the main ones are (1) reflow soldering
> problems and (2) reliability
> problems due to so much manual rework. If you look at electronic
> cameras, cellphones etc you
> will find FLEX circuits in which the devices are mounted on one side,
> but are folded back on itself
> to obtain the effect of both sides.

I don't know which board houses you guys are talking about. We've been doing 
double sided SMT since 2005, and none of the board houses we have contacted, 
had any problem with the PCB being double sided. In our experience, the 
additional cost is *not* significant (~$1/2 per board).

The old board house simply populated and ran the PCB through the oven twice. 
Surface tension keeps components on the bottom from falling off. I'm 
assuming the new board house we just switched to, builds them the same way. 
Glue can be used to secure heavier components -- never had to do it, but the 
rumor is that it adds quite a bit to the cost because of the glue drying 
time.

I think Martin's best bet is to find a contract manufacturer, and put this 
question to them. It's a good idea to run the design by them anyway, even 
before you have the prototype -- ask them if they can see any opportunities 
to reduce your cost with a small design change, or improve the board's 
manufacturability.

> Another strategy I have seen is to use two very thin PCBs seperated by
> only a spacer; both are populated
> on one side only.

I've never seen such arrangement, but I've seen plenty of PCBs with SMT 
components on both sides. They're not by any means "atypical".

Best regards,

Vitaliy 

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