Homebrew PCBs

On Fri, 08 Dec 2006 14:49:53 +0100, DJ Delorie <dj@...> wrote:

>
> For vias at least, you only need one size (holes for pins is a
> different story), and 1000 seems reasonable.  I just checked a recent
> 4.5x3.5" board and it had nearly 300 vias (12 mil) all by itself, plus
> 168 pin holes, a majority of which were close enough in size (28/35/40
> mil) that I could probably get away with one size for all of them.
> Hmmm... I wonder if we can use standard copper tubing for this.  The
> issues would be (1) getting small enough sizes, and (2) cutting them
> without destroying them.
> (humor: I googled for "tiny copper" and half the sponsored links were
> for a "mini cooper" :)


And how much fun would it be to place 300 vias a board, manually? Not to  
speak of the other problems like them being much larger than regular vias  
and they protrude a bit from the board which may be impossible under SMD  
parts. Also, with 300 vias a board you only get 3 boards out of your 1000  
pieces pack, for 15 pounds? I don't think so, you can almost have the  
boards made for that in places.

You can also use ferrules, but the smallest size i could find is still  
rather large. Thin copper tubing is also used for capillary lines  
(thermostats etc.), but you'd need to cut that, and it doesn't have a  
flanged end, and it's probably still large, or too thick walled.
Those eyelets were useful to some extent before SMD, because you could use  
throughhole parts on non-pth boards that could not be soldered top side  
and still have a via there. But now, with the small sizes, there just  
seems little to no point in them.


I'm _very_ cheap, and very much in favor of homebrewing, but the whole  
eyelets thing has always struck me as rather nonsensical from a  
price/reliability/effort/usefulness perspective. If you are going to make  
that sort of compromise, you are much better off putting the extra effort  
into layout to get away with no or very few (solderable) vias. If you  
can't do that, it seems better to have the board made than using any of  
the commercial fake via solutions.

Anyway, just my opinion.

ST