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'[OT] Designing PCBs - literature'
2005\09\29@100450 by pic

picon face
Recently I designed a board and sent it away to manufacture.
After it was soldered I discovered that not all components work.

Do you know any "good" literature about designing PCBs?

Thank you,
Sam


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2005\09\29@103352 by Wouter van Ooijen

face picon face
> Recently I designed a board and sent it away to manufacture.
> After it was soldered I discovered that not all components work.
> Do you know any "good" literature about designing PCBs?

What was your problem?
- the circuit : use simulation software and/or build your circuit on a
(solderless) breadboard first
- the PCB did not reflect the circuit : use a tool that warns you when
circuit and PCB do not agree (I like eagle)
- the PCB layout affects your circuit : that's the difficult one. there
is a lot to say about this, specifying your specific problem might help
others (who are more knowledgeable than me) to recommend a book.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\09\29@104835 by Howard Winter

face
flavicon
picon face
Sam,

On Thu, 29 Sep 2005 15:04:48 +0100, spam_OUTpicTakeThisOuTspamamusementcity.com wrote:

> Recently I designed a board and sent it away to manufacture.
> After it was soldered I discovered that not all components work.
>
> Do you know any "good" literature about designing PCBs?

I'm confused - why do you think that non-working components is related to PCB design?

Cheers,


Howard Winter
St.Albans, England


2005\09\29@111506 by Sam

picon face
I'm asking about the third possibility.
In my case I've got CS8900A on board ( ethernet part ) and PIC18F8621.
PIC works grand but CS doesn't even start. Chip is OK. My guess is that
I placed
power circuit on PCB badly.
So my questions are:
- how thick should be power and gnd paths
- what decoupling capacitors should I use
- how should be decoupling capacitors placed
- how distance between paths influence signal integrity

Basically I'm looking for some reference about it. I did look on
internet and I
found some resources but some of them tell different things.

I'm looking for opinion from somebody experienced who maybe know a good book (
or a website ) on this topic that he would recommend.

Regards,
Sam



Quoting Wouter van Ooijen <.....wouterKILLspamspam@spam@voti.nl>:

{Quote hidden}

> -

2005\09\29@112212 by Sam

picon face
I soldered out that component ( CS8900A ) and soldered it to another board and
it worked as it should.

Regards,
Sam

P.S. Schematic capture of both boards was exactly the same but layout was
different.

Quoting Howard Winter <HDRWspamKILLspamh2org.demon.co.uk>:

{Quote hidden}

> -

2005\09\29@113923 by Wouter van Ooijen

face picon face
> I soldered out that component ( CS8900A ) and soldered it to
> another board and it worked as it should.

Was it hand-soldered? Don't rule out the possibility of a bad solder
joint, I have seen things that were only visible with a x 20 loupe.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\09\29@113947 by Electron

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face
At 15.04 2005.09.29 +0100, you wrote:
>Recently I designed a board and sent it away to manufacture.
>After it was soldered I discovered that not all components work.
>
>Do you know any "good" literature about designing PCBs?

I'd say for this and other useful info:

"The Circuit Designer's Companion", by Tim Williams (a recent 2nd
edition is now available).

Very useful book.

2005\09\29@115835 by Sam

picon face
Thank you. It really seems to be a good one.

Regards,
Sam

Quoting Electron <EraseMEelectron2k4spam_OUTspamTakeThisOuTinfinito.it>:

{Quote hidden}

> -

2005\09\29@120935 by Marcel Birthelmer

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face
I think that's the one I've got arriving in the mail today. I can give
you more feedback later if you'd like.
- Marcel

Sam wrote:
{Quote hidden}

>> --

2005\09\29@121843 by Sam

picon face
Yes, please.

Thank you,
Sam

Quoting Marcel Birthelmer <@spam@marcelKILLspamspamcarrietech.com>:

{Quote hidden}

2005\09\29@122022 by olin piclist

face picon face
pic@amusementcity.com wrote:
> Recently I designed a board and sent it away to manufacture.
> After it was soldered I discovered that not all components work.
>
> Do you know any "good" literature about designing PCBs?

In don't know, but what does that have to do with components not working?

*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\09\29@122647 by Spehro Pefhany

picon face
At 04:15 PM 9/29/2005 +0100, you wrote:
>I'm asking about the third possibility.
>In my case I've got CS8900A on board ( ethernet part ) and PIC18F8621.
>PIC works grand but CS doesn't even start. Chip is OK. My guess is that I
>placed
>power circuit on PCB badly.

My guess is that it's really something else, like a connection you missed or a
duff crystal.

Despite the care we typically take with layout and bypass capacitors, IME
most digital stuff will work on the bench with pretty awful layout and with
minimal or no bypassing. Bypassing is not the same as ensuring stability- many
LDO regulators will oscillate without an output capacitor in the right
capacitance
range and with the right range of ESR. Follow those recommendations to the
letter.

>So my questions are:
>- how thick should be power and gnd paths

Thick as possible. ;-) Ground planes are always better than traces. The layout
is also important-- minimize loop area, don't have long serpentine power
and ground traces. Lay them out *first*. That's true even if you're using an
autorouter. Really, layout is more important than thickness in many cases. A
bad layout with a 100-mil wide trace can be a lot worse than a good layout with
a 10 mil wide trace, especially if there is low-level or high-current stuff on
the same board. Your board sounds especially non-critical.

>- what decoupling capacitors should I use

Ceramic, possibly with an electrolytic for more capacitance and damping.
Or you could use a large ceramic with a small resistor in series.

>- how should be decoupling capacitors placed

Near the Vdd and GND pins of each LSI chip, or as the manufacturer recommends
(one AD part I just used has a couple of dozen 0402 bypass caps for every
chip, as recommended).

>- how distance between paths influence signal integrity

Not much at low frequencies.

>Basically I'm looking for some reference about it. I did look on internet
>and I
>found some resources but some of them tell different things.

It's kind of a black art. You can look at professionally designed
boards and copy the techniques. I have found _Noise Reduction Techniques
in Electronic Systems_ somewhat useful, but you can probably find the
same information for free on the net. Try trolling through application
notes, in particular.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
RemoveMEspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\09\29@122937 by olin piclist

face picon face
Sam wrote:
> - how thick should be power and gnd paths

As thick as you can manage within the other constraints.  A whole ground
plane is best.  This gives the board good RF properties in addition to low
impedence between all the ground points.

> - what decoupling capacitors should I use

At least 100nF ceramic for lower power things.  Nowadays I use 1uF ceramic
for anything more than a few milliamps.  New ceramic technology and high
volumes have made these cheap and available.

> - how should be decoupling capacitors placed

As close to the power pins as possible.  If you've got a high current device
with multiple power and ground pins, bring each net together at a single
point and connect only that single point to the rest of the board power and
ground.  By doing that the local loop currents will stay local.

> - how distance between paths influence signal integrity

Longer makes it worse.  At short distances it's mostly an impedence issue.
Once the trace gets to be near 1/2 wavelength or longer you have to consider
antenna effects too.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\09\29@162541 by alan smith

picon face
then...the layout was probably not correct.  First review the gerbers...or troubleshoot the board.  Did you hook up power to the chip?  decouple caps need to be as close as possible, the lower the frequency of the design, the less importance that is.  If your running at 800Mhz and the cap placement isnt optimal, its essentially non-effective at that frequency.  There is an entire science devoted to signal integrity.  But if its slow, then stick them near.....

Course his problem could have been a cold solder as well.....

Sam <spamBeGonepicspamBeGonespamamusementcity.com> wrote:
I soldered out that component ( CS8900A ) and soldered it to another board and
it worked as it should.

Regards,
Sam

P.S. Schematic capture of both boards was exactly the same but layout was
different.

Quoting Howard Winter :

{Quote hidden}

> -

2005\09\29@164220 by Spehro Pefhany

picon face
At 01:25 PM 9/29/2005 -0700, you wrote:

>Course his problem could have been a cold solder as well.....

Or a short, or a line not tied to the right level.

There are 100 pins on that chip, lots of opportunity for that sort of thing.

I'd start by checking every one of them off on the schematic or netlist
one by one.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
RemoveMEspeffspamTakeThisOuTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\09\30@014049 by Marcel Birthelmer

flavicon
face
Well, I've looked it over a little bit, and it looks very promising.
It's a fairly easy-to-read style, good amount of substance/information.
Unfortunately it's not exactly what I was looking for. I was hoping for
an introduction to PCB design, which this book definitely isn't. This
book aims to augment other, more theoretical works about electronics
with information about practical scenarios and problems. It does not
include basic routing principles etc., but rather points out things to
avoid when you're routing. In other words, it's mainly don'ts, no dos.
Hope this is helpful. If you want to know anything else, feel free to ask.
- Marcel


Sam wrote:
{Quote hidden}

2005\09\30@112030 by Sam

picon face
Thank you everybody.
I'm going to follow your advices.

Regards,
Sam

Quoting Marcel Birthelmer <RemoveMEmarcelEraseMEspamEraseMEcarrietech.com>:

{Quote hidden}

>

2005\09\30@141503 by Bob J

picon face
"Build Your Own Printed Circuit Board" by Al Williams is an excellent
beginner's book. Lots of info on Eagle in there too.

Regards,
Bob

On 9/30/05, Marcel Birthelmer <EraseMEmarcelspamspamspamBeGonecarrietech.com> wrote:
{Quote hidden}

>

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