[time-nuts] PCB design questions thread II
Richard H McCorkle
mccorkle at ptialaska.net
Mon Jun 2 14:41:16 EDT 2008
David and Patrick,
Check out the following two sites to get an idea of the
current costs to have a custom made board produced.
> Hi David and list
> I am quite interested in this post too.
> I have wanted to fabricate my own PCBs for several years now but I have
> never made an attempt. I am set up here to do silk screening and I have
> ovens and a hot-air soldering iron. Has anyone else tried to fabricate
> their own boards or is the price of farming the work out just so low now?
> If anyone has farmed out work, could you please feedback as to the entry
> level costs and if possible, some suggested companies?
> P.S Many of the boards I want to fabricate are replacements for obsolete
> ones. Is there a way to split the layers of an old board apart to study
> David C. Partridge wrote:
>> I've been working on the design for a frequency divider to complement the
>> Thunderbolt I recently bought from TVB (thank you Tom, it's working very
>> well as far as I can tell, though of course I've no other standard to
>> compare against).
>> Thanks to lots of advice and guidance from Bruce Griffiths (many thanks
>> again Bruce), I've got the design near completion.
>> I'm not aiming for NIST or equivalent perfection in terms on minimising
>> jitter and other noise, but would like to at least make a at least a
>> half-way decent job of this.
>> I'm now thinking ahead to the PCB requirements,with the caveat that I've
>> only ever designed one PCB before and that was a single layer board done
>> using double sized mylar and sticky black tape (Yes, it was a good many
>> years ago).
>> Now to questions:
>> 1. Surface mount or through hole? I don't have a re-flow oven (or even a
>> hot air soldering system), so my inclination is to use through hole CMOS
>> (74HC163s with 74AC glue logic and flip-flops), with the surface mount
>> restricted to the clock shaper using a BAV99 and either an ADCMP600 or
>> MAX999 and surrounding components. Will using through hole cause me grief?
>> 2. How many layers? In an ideal world with money no object, if I
>> understand the current art correctly, I think I'd probably aim for a five
>> layer board with Vcc, Digital Ground and Power Ground being separate
>> internal planes, and trace routing on the top and bottom of the board with
>> as few vias between top and bottom as possible. Does that sound right?
>> Do you think I can safely restrict myself to two layers, and if so does it
>> make most sense to make one side of the board digital ground, and route
>> everything else (Vcc, Power/Analogue Ground, and signals) on the other side.
>> Or is there a better approach (always assuming that a two layer board is a
>> viable option).
>> Dave Partridge
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