Well, considering that most of the stuff I design these days is SMT, (and
mostly hobby stuff) I'm not sure I see that particular advantage of double
sided pcb manufacture.
  I've seen plenty of TH (through hole) components pop off single and
double sided boards, and I will certainly agree for production boards with
switches, connectors, and higher mass TH components, a double sided board
will do a job better.

  The advantage I do see with single sided prototyping is cost and speed.
Single sided copper clad is cheap. Toner transfer paper is cheap (at least
the stuff I use).
   I can lay out a board in the morning, and have it stuffed and tested by
the evening. And when I find problems in the board, toss it in the garbage
and just cut another one.

  Now, I'm not going to insist that this is a no-brainer process, and it
does take some experimenting to get the process down. But It's not too
difficult for most people, just don't expect perfect results the first time.

   Certainly sending it out to fab house is easier, but when I want it now,
and I want it cheap (we'll not discuss what I pay myself in hourly wages) I
make it myself.

   btw, here is a pdf on my projects page that may help anybody who want's
to experiment with toner transfer pcb fabrication. Learn from my mistakes.
     http://users.rcn.com/carlott/projects.html


-carl


At 08:28 AM 11/24/2002, you wrote:
>Being an old guy, having worked with commercial
>1-sided PCBs in the past, I feel that I need to pass
>my 2-cents to people attempting 1-sided PCBs. The
>2-cents is: don't waste money on 1-sided boards.
>
>A PCB must perform two, unrelated tasks: (1) it must
>interconnect the components, and (2) it must rigidly
>MOUNT (hold in place) the components.
>
>A 1-sided board makes a fair attempt at the first requirement,
>in that wire jumpers can be installed to eliminate top-side traces,
>but it fails miserably to properly mount the components. The leads
>of all components are passed through the board and only contact
>the bottom copper traces through a small solder blob about 30 mils thick.
>That blob has little strength, and the connection can withstand very
>little vibration or flexing. Commercially, in years past the board was
>dipped in shellac to strengthen the physical resistance to vibration, but
>that lessens its ability to accept flexing.
>
>A 2-sided PCB, on the other hand, has an interconnect from a pad on
>top to a similar pad on the bottom, with a hole lined with copper at least
>1/16" long+ a 1/16" blob. When a component is passed through that and
>soldered and the hole filled with solder, the solder connection is 100x
>stronger than that of single-sided boards. Vibration tests done at TI in
>1960 proved to us that 2-sided boards could sustain 1Khz 5G swings (some
>components could
>not, though).
>
>These days, the best way to make a prototype is to send it to somebody who
>can make a decent 2-sided, 1-oz PCB with good feedthru holes. Its worth the
>money, it really is.
>
>--Bob
>EDTec LLC

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