
PCB Design Tutorial for Startups - poindontcare
http://www.nepsu.com/nepsu_ultimate_pcb_design_guide.html
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bsder
A couple things that I wish people had pointed out before I got started with
PCB's:

1) You will spend your life reading datasheets.

2) Datasheets lie.

3) You will spend way more time in component selection than schematic design
or board layout.

4) You will spend way more time creating component footprints than in
schematic design or board layout.

5) Lay out the board by hand. You will waste more time fighting an autorouter
than if you just laid it out.

6) A 6 layer board is not that much more expensive than a 4 layer board and is
_VASTLY_ easier to lay out. 2 layer boards should be avoided unless you you
are a masochist or every fraction of a penny _really_ counts.

Some of the given advice is a bit off.

1) He doesn't put enough emphasis behind avoiding BGA. BGA should be avoided
like the plague. Period. It will only cause excruciating pain.

2) Small QFN isn't that hard to deal with ... if you tweak the PCB footprints
a touch (make sure you have .5 mm of bare copper outside the package outline
and you can treat them like QFP).

3) 0603 is actually pretty small. Most people should stick with 1206/1210.

~~~
TaylorAlexander
Agree on most parts. I would say you can learn to love 0603 and even 0402 if
you have the right equipment. You need a proper stereo zoom microscope and
then everything is big, and smaller components can save a lot of space. But
don't go there until you've done the bigger stuff and actually felt a need for
more room. Definitely 1206 and 0805 are plenty fine for people who aren't
super in to it.

Another hard lesson I have learned is that PCB assemblers lie. Even supposedly
reputable community friendly ones. If they can save money by swapping out a
component for unknown alternatives, there's some nonzero chance that will
happen.

~~~
toomanybeersies
I was a solder monkey for a summer a few years back, and all I had was a
magnifying glass lamp [1], I was soldering resistors down to 0603.

Last semester at university I did a hardware design course (sort of by
accident), at the lab, they had a stereoscopic microscope similar to [2]. I
never realised what I was missing out on until I used one, apparently they're
up to 10 grand a pop, so I can see why my old work didn't have one, being a
pretty small shop.

[1] [http://uk.farnell.com/lightcraft/lc8093led-euk/led-table-
mag...](http://uk.farnell.com/lightcraft/lc8093led-euk/led-table-
magnifier-1-75x-4x-mag/dp/2442796)

[2] [http://www.visioneng.com/products/stereo-microscopes/lynx-
dy...](http://www.visioneng.com/products/stereo-microscopes/lynx-dynascope-
inspection-microscope)

~~~
TaylorAlexander
I've seen that style but never used them. I will say that a $200 AmScope is
well worth the investment. Not as nice as a high quality microscope, but
vastly superior to a magnifier.

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honkhonkpants
A long article that says almost nothing. Instead of choosing trace widths and
layer count and component sizes at random, take a week to read and understand
the very useful book "High Speed Digital Design" by Howard Johnson. Despite
the name it concerns itself more with the analog domain than with the digital.
Very useful information about the behavior of traces and holes in boards.

~~~
pmorici
I didn't want to be critical of it but as someone who went through the process
of designing and manufacturing my own hardware product to sell a couple years
ago that was my thought as well. Really long and very little insight into the
real difficult parts.

~~~
jwr
As someone who has actually designed manufacturable boards I'd say the same.
In addition the article has some strange recommendations:

* don't use QFN — I see no reason to, on the contrary, these are great packages (see my other post in this thread)

* 0603 minimum size for passives — huh? I see no reason not to go down to 0402, which is both easy to manufacture (assembly costs are the same, component costs are usually lower), and easy to prototype (just get a large desk magnifying glass and a good pair of tweezers and you're good to go).

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jwr
Here's something I don't get: why discourage people from using QFN packages?

QFNs are only a problem if you are hand-soldering your boards with a
traditional soldering iron. Which is nuts. These days everyone should have a
soldering station with both traditional iron and hot air — and soldering QFNs
using hot air is straightforward and easy.

Besides, the article is about manufacturing, so you aren't likely to solder
those QFNs yourself. So why discourage them?

I think QFN and DFN packages are fantastic. They save lots of board space (and
believe me, board space matters a _lot_ in all designs, more than you think!),
have good thermal properties, lack of leads makes for better low-inductance
connections, less material means lower price. And most still have pitch of
0.5mm or more, so you can use the same design rules and same PCB pricing.
Everything is great about them.

BGAs are a different matter, but not for the reason most people think: they
are problematic not because they are difficult to solder, but because you need
much tighter PCB parameters to be able to route all the signals. In
particular, via size is the biggest problem. You need really small vias that
can be placed between four BGA balls.

I dislike the hate being poured onto QFNs. I think it is a relict of the past:
back when hot air was expensive and "strange" and people tried to solder
everything by hand using a soldering iron, QFNs were the enemy. But these days
they should not be.

The unfortunate effect of hobbyists hating QFNs is that some manufacturers
(Freescale/NXP, notably) later class certain chips as "hobbyist" and don't
provide QFN packaging at all. And believe me, if you're designing a wearable
device, the difference in size between a QFN-64 and an LQFP-64 is monstrous.
Providing no real advantages, because both have 0.5mm pin pitch.

So, while I would agree with the author that BGA packages are best avoided, I
would encourage everyone to actually go ahead and use QFN/DFN packages. They
are better in every respect.

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zw123456
Nice overview article. I have been doing PCB's for about 3 decades and here
are just a couple of little tricks I have learned over the years, some are too
long to go into here, but just a couple quickies maybe will help someone out:

1) Often the chip manufacture provides BSDL files which often times contain
the foot print info and a lot of CAD tools have macros that will read them in
and create your foot print for you.

2) There are often foot print libraries already out there you can download or
are provided by the CAD software. But in either case, don't trust them, there
are often errors, get your parts first, do the PCB layout, print it out on a
good printer (usually the CAD SW will print it to scale and test fit
everything.

3) There is a big difference between doing prototype boards and production
boards. For prototype boards, make them big because you will have mistakes and
will probably have to black wire (cut a trace and fix) it. I often use 2 layer
or 4 layer for prototypes because it is easier to do fixes. If you CAD SW does
auto layout then it is not that big of a deal as long as the board is large
enough for it to route everything for you. For Production PCB's it is a
different story and a lot more work to do right and I recommend farming it out
if you can afford to.

4) I agree that part selection is critical but also, if you have simulation
software either a separate program or in your CAD system, doing simulations
can save you a lot of time. If you don't have simulation SW check into it,
there are some decent free ones to learn on but to get serious you have to pay
a lot.

5) For complex designs, I do separate prototype boards, one with the FPGA on
it, another with the MCU and another one with the analog on it and so or, sort
of a unit test approach (sort of like dev-ing SW) that way you can swap out
sections that aren't working for you without throwing away a board full of
parts, it is more effort but if you plan it out it can save you time and
money.

6) I agree with the BGA comments, don't use those types of components unless
you have a reflow oven and know how to use it, it is easier to debug QFN and
QFP type packages since all the leads are exposed for inspection. You can
often get parts in either package type and when you go to production you can
always swap out to the smaller package later. If you have to use those for
prototyping check if the manufacturer has a prototype board for it already it
can be easier to just use an off the shelf one.

A lot of people say the first board is a throw away, but that can be expensive
for a production one so I have learned these tricks for prototyping so when
you get to production you can avoid that bad first board.

~~~
mschuster91
> There is a big difference between doing prototype boards and production
> boards. For prototype boards, make them big because you will have mistakes
> and will probably have to black wire (cut a trace and fix) it. I often use 2
> layer or 4 layer for prototypes because it is easier to do fixes

Not only this, you can also print your own boards if you stick to two layers.
Way, way, way faster than waiting days to try something out and notice you
swapped Vcc and GND pins on a chip by accident.

~~~
zw123456
Heck ya, if you have the capability to do your own boards, even if only 2
layer, I would do that. So much faster t !

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turnip1979
I'm in the Bay area and a hardware hobbyist (software is my full time gig). I
see tons of meetups for SW but almost nothing for electronics hardware. Any
recommendations?

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arcticbull
Also, ChipQuick is great. It's super-low melting point solder you can use to
easily rework SMD components. This thing has saved my ass too many times to
count as a hobbyist :) Was able to get away without a reflow station for the
small stuff I've been working on.

[http://www.chipquik.com/store/index.php?cPath=200](http://www.chipquik.com/store/index.php?cPath=200)

