Hello ! ! !
Is anybody home ! ! !
This is sheer stupidity ! ! !
So far only one person has asked the critical question, and everyone including Joe
has ignored it ! ! !
Joe - What type of PCB Software, if any, do you have ? ? ?
Joe - What, if anything other than a pencil and paper, did you use to draw your
schematics with ? ? ?
You say you have been "tasked" - Do the people (your boss? - your company?) that
have "tasked you" with this "task" own any PCB / Schematic software?
You say that a board house has done this for you in the past, and made PCB's for
you - what PCB / Schematic software did they use to make your previous PCB's
If you really don't want to answer all of these questions, and if you feel that the
PCB is such a "no brainer", then go to PCB Express and download their "no brainer"
software and make your own "no brainer" PCB in "10 to 12 hours" and spare us the
false humility.
If you are serious about needing help, or even needing to find someone to do the PCB
for you, you need to start with the above questions, since it does you absolutely no
good whatsoever to have your PCB done in Mentor Graphics by someone consulting for
you, when your employer owns Protel, and you board house has done 2 or 3 previous
PCB's in PADs, and you have been using an old copy or OrCAD 7.10 to do your
schematics.
You need to start with the Software, and so does anyone else who is really going to
be of any real help to you.
One simple word of advice no matter what you do, and that is this: Unless you are
doing something for Spaceflight or the Military, or it has to operate above a
Gigahertz, you are worrying far far far far too much, and making much more out of
the project than it has to be - in otherwords, don't be too paranoid about
"libraries" at this point in the game, just use what you have, since by your
discription, almost any library will do at this point in time for what you appear to
be doing.
Start by using the software your company already owns, and just start and go from
there. If your company doesn't own any software, then you have totally mis-judged
and mis-stated your real task, which means that you really have to start at the
beginning and chose what software you need based on what you have to do and what you
can afford, which is really a whole different can of worms than what you have
presented here. (This question should take into consideration what was used to make
any previous PCB's done for you by the board house, but does not have to be ther
overiding factor in the decision if there are not to many previous boards and they
were not too complicated.)
Enough for now, at least until you define where you really are right now in terms of
software.
Even if you decide that you or your company doesn't want to buy any software, you
really do need to choose a brand of software to work with before you just walk into
a consulting situation in which you end up with your designs done with who knows
what, just as your previous designs. And yes, you need to consider your previous
designs here too, to whatever extent that is worth.
JaMi
----- Original Message -----
From: "Harter, Robert" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, February 08, 2005 8:05 AM
Subject: Re: [DC] Designing PCB footprints
Joseph,
I tend to agree with Ted on his opinion of the CAD company's footprints,
they're usually overly generous with the pad geometries which can really
screw up a tight board trying to keep components from twisting or tomb
stoning.
I have been doing layout of mixed signals for 3 years after being thrown
to the wolves as a RF Technician. Fortunately I had a manager at the
time that saw the value of attending the CAD company's training classes.
I have found the best source of information to be forums when I need a
quick answer but I also try and get my hands on everything I can read
especially PCB Design Magazine, it's free and comes in either digital or
print monthly and for specialized design information I am a committed RF
Design reader now lots of great information for the proper handling of
high frequency circuits and noise reduction too.
Bob Harter, Jr.
PCB Designer
Paratek Microwave, Inc.
6935 G Oakland Mills Rd.
Columbia, MD 21045
PH# (443)259-0140 x278
CP# (443)739-8407
WWW.PARATEK.COM
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Ted
Tontis
Sent: Tuesday, February 08, 2005 10:47
To: [log in to unmask]
Subject: Re: [DC] Designing PCB footprints
Joseph,
I for one stay away from using footprints provided by the CAD
vendor, CAD vendors are in the business to sell CAD software not
footprint libraries, but that's just my personal opinion. I too was
thrown to the wolves and forced to learn about designing PCB's in a
crunch. From first hand I can tell you that there is no good time to
start learning, and experience is the best teacher. Learning PCB design
will also make you more marketable, and a better Design Engineer. If you
have access to some of the IPC doc's that's a great place to start. I
would also suggest you take a look at the book Karl suggested Printed
Circuits Handbook it is worth its weight in gold. Also check with your
CAD vendor most have forums that you can get on that have a knowledge
base that is usually better then their customer support, and much
faster.
Tom Hausherr wrote an article in PCDmag about the future of CAD
libraries, this article will not give you all the answers but may clear
up some questions. http://pcdandm.com/pcdmag/mag/current_issue.shtml
What type of design is this Analog, Digital, or both? There is a
lot to designing a PCB then throwing a bunch of parts down, connecting
the parts, and sending it to the contract manufacture to be
manufactured. If you need help use the Designers forum as a sounding
board, that's what it is here for.
Good luck in your first design and welcome to the PCB designers world :)
Ted
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]]On Behalf Of
Joseph Matthews
Sent: Tuesday, February 08, 2005 12:58 AM
To: [log in to unmask]
Subject: Re: [DC] Designing PCB footprints
Dear Mario, Everyone;
Thanks for the feedback everyone. Thanks Mario. Understood, it'd be
impractical for me to think I could learn all of the nuiances of PCB
design and in being perfectly candid, I'm not about to -- there are too
many seasoned people out there...it makes no sense for me to embark down
that road at this stage in my carrer -- irrespective of how lucrative it
might be ;) (trust me, hardware engineers aren't paid *that* much).
No less, for simple, one or two day prototypes I need to be able to
layout my own boards. It's not practical to outsource hardware test
boards (Processor/Controller boards, FPGAs, CPLDs, etc -- literally
20-30 components, a few pull ups, bypass caps, etc., and usually one or
two real "interface" devices -- i.e. a header or two, comm. connector
(RS-232, I2C), power, etc.)
The unfortunate thing is that I've gone down this road before and
to-date I've been able to get away with literally giving a schematic
over to the baord house and for pennies (ok, maybe not pennies, but
cheap) they've gone ahead and taken my schematic and a little
chicken-scratch and put out a board for me. Well, things are getting a
bit more complicated that that and our proto shop has had to
change...long story short, I need to be able to turn out something like
a decent set of gerbers and though I fancy myself pretty good at
interpreting standards and information, thought who better to ask than
the experts (I too am aware of just how little I know sometimes, beleive
me).
So I'm hoping that people have some tips, some basics, some fundamentals
that'll help me get started in making something farily reliable. I
checked with the board house and they are fine about specifying certain
design constraints, and as you'd expect, the datasheet gives you some
more to go with. The problem is that all the informaiton I can get from
the fabricator is not going to be enough to spare me the inevitable
reject and I'm sure (though you may hat e to admit it) you've seen years
of mistakes that I'm hoping to avoid. Any wisdom, insights, thoughts,
prayers, would be appreciated :)
Sincerely,
Joe
Mario Irigoyen <[log in to unmask]> wrote:
Hi all,
Well, here we go. I guess that's why there are professional PCB
designers who design circuit boards and there are hardware engineers who
design circuits. I certainly wouldn't try to grasp (or even attempt to
learn) all the caveats of hardware design so I certainly wouldn't expect
an engineer to do the same for PCB design. Us PCB guys understand the
processes, guidelines, rules ... because we deal with them every day. I
feel for you. You are being asked (forced) to move out of your realm
into uncharted territory for what, to save time, money? The reality is -
neither. Engineers get paid more than PCB designers (if not true please
correct me). So, even if you could design a board in the same time as a
PCB designer the cost is higher. But that won't happen. Then there are
all of the manufacturing, testing, reliability ... issues that you have
to "learn". Wow. The company would be much, much better off from every
aspect to have the board designed by a seasoned professional PCB
designer. Lower cost, certainly much better quality and a lot quicker.
I'm sure you are an excellent engineer so please do not take offense. It
takes years of experience to develop the expertise required to be a good
PCB designer.
Good luck.
Best regards,
Mario Irigoyen
MPC Engineering
[log in to unmask]
[log in to unmask] Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Joseph Matthews
Sent: Monday, February 07, 2005 5:50 PM
To: [log in to unmask]
Subject: [DC] Designing PCB footprints
Greetings,
As a hardware engineer I have been tasked with laying out my first real
circuitboard in years (first *real* board I guess). It's proved a bear.
With years of experience designing hardware I am totally unprepared for
the leap from the "logical" into the "physical" at this stage in my
career. No less, I am under a crunch (as we all are, right?) and this
being a fairly simple board, I figured it's time I dove in and
learned...Simply stated, I'm stumped. Where can I find a comprehensive,
clearly defined explaination on how to create *quality* PCB footprints
and/or what the terms are used by the Footprint calculator made by PCB
Libraries. I see all of these fields to enter information but I'm not
sure what these mean and how to translate what's on the datasheet to
these fields.
I have read through a few of the IPC standards (some of the 122x stuff)
and still can't say I undertsand much more of what's required. Is there
a more comprehensive standard or something that more clearly deliniates,
"do this...don't do this"...or, "if the pad is this big on the
datasheet, add n%". These standards seem fairly high-level and at times
seem almost circular. No less, they are not totally specific and I'm
not sure where I can get the very specific information. I of course am
aware that there's probably more to it than simply adding a bit here or
a bit there, but assuming I know nothing, can someone offer some
straight-forward advice on how to build up a board. Nothing fancy, just
the basics. I should be smart enough to take it from there.
I hate to inundate people with how-to's but everything I've read,
including a book on the fundamentals of PCB layout seems very high-level
and seem almost afraid to say anything for certain.
Thanks for your help.
Joe
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