Library strategy question

[Steve Kraft]

I've done a few boards with Eagle and am getting pretty comfortable with
it. I'm getting ready to start on a project that is pretty large, and I
have a question about library strategy....

On my earlier projects, I use a mishmash of parts from the existing
libraries, and then also create parts in my own library. This seems
easy while I'm doing the schematic/layout, but is bad when the boards
come back because invariably a few of the devices I used are messed up
in some fashion.

So on this upcoming project, here's the strategy I'm thinking of using:

1) Copy ref-packages.lbr to mylibrary.lbr. This gives me a (hopefully)
pretty good head start with package footprints that I can have
reasonable confidence in.

2) Create all the symbols and devices myself straight from the part
datasheets, as well as all packages that are not included in
ref-packages.lbr. This seems sort of crazy what with all of the
pre-built stuff in the included .lbr files, but it just seemed to me if
I'm using, say, 100 different parts on my board, and if each part takes
10 minutes to create in the library editor, then that's only about 2
days worth of work. I can sure burn up more than 2 days when I get
boards back that use a couple of parts that are incorrect in the
libraries that come with Eagle, then I have to debug, re-layout, and
re-fab the boards.

Am I crazy? If so, do you have any suggestions?

Thanks,
Steve

[David Moodie]

Post by Steve Kraft
I've done a few boards with Eagle and am getting pretty comfortable with
it. I'm getting ready to start on a project that is pretty large, and I
have a question about library strategy....
On my earlier projects, I use a mishmash of parts from the existing
libraries, and then also create parts in my own library. This seems
easy while I'm doing the schematic/layout, but is bad when the boards
come back because invariably a few of the devices I used are messed up
in some fashion.
1) Copy ref-packages.lbr to mylibrary.lbr. This gives me a (hopefully)
pretty good head start with package footprints that I can have
reasonable confidence in.
2) Create all the symbols and devices myself straight from the part
datasheets, as well as all packages that are not included in
ref-packages.lbr. This seems sort of crazy what with all of the
pre-built stuff in the included .lbr files, but it just seemed to me if
I'm using, say, 100 different parts on my board, and if each part takes
10 minutes to create in the library editor, then that's only about 2
days worth of work. I can sure burn up more than 2 days when I get
boards back that use a couple of parts that are incorrect in the
libraries that come with Eagle, then I have to debug, re-layout, and
re-fab the boards.
Am I crazy? If so, do you have any suggestions?
Thanks,
Steve

It is good practice to build up your own trusted libs. I'm pretty sure that
you'll find the usual weasel words somewhere in the documentation that the
libraries are provided as an additional service and no guarantee is given
concerning their accuracy

Eagle does come with lot of reasonable libs, but I would check each part
before using it. Personally I really don't like a lot of their silk screen
art work. Many parts simply have too much of it and all detail could be on
layer 51 rather than 21. Some have a lot of silk screen running over pads,
and while your board house can take care of this it is bad practice.

If you want to use the Eagle libs as the basis for your own then that is OK,
but I would recommend that you only copy over the packages from the
ref-packages lib when you want to use one rather than ending up with
numerous footprints you will never use.

A quick look also shows that most of there SMT packages do not have a clear
indicator of pin 1 outwith the package body. This can be a real pain in the
ass when debugging and trying to probe individual pins. It also makes life
difficult for your assembly house if they are doing an optical inspection.
Copy a part over when you need it, check this and then add a dot/circle at
pin one outwith the body.

In fact when I look again some parts are completely missing any useful
silkscreen. Trust no-one, and check everything before you use it

You would only be crazy if you went ahead and used the libs without checking
their validity for yourself. The approach of making your own libs is
recommended.

cheers

David

[Steve Kraft]

Post by David Moodie

Post by Steve Kraft
I've done a few boards with Eagle and am getting pretty comfortable
with it. I'm getting ready to start on a project that is pretty
large, and I have a question about library strategy....
On my earlier projects, I use a mishmash of parts from the existing
libraries, and then also create parts in my own library. This seems
easy while I'm doing the schematic/layout, but is bad when the boards
come back because invariably a few of the devices I used are messed up
in some fashion.
1) Copy ref-packages.lbr to mylibrary.lbr. This gives me a
(hopefully) pretty good head start with package footprints that I can
have reasonable confidence in.
2) Create all the symbols and devices myself straight from the part
datasheets, as well as all packages that are not included in
ref-packages.lbr. This seems sort of crazy what with all of the
pre-built stuff in the included .lbr files, but it just seemed to me
if I'm using, say, 100 different parts on my board, and if each part
takes 10 minutes to create in the library editor, then that's only
about 2 days worth of work. I can sure burn up more than 2 days when
I get boards back that use a couple of parts that are incorrect in the
libraries that come with Eagle, then I have to debug, re-layout, and
re-fab the boards.
Am I crazy? If so, do you have any suggestions?
Thanks,
Steve

It is good practice to build up your own trusted libs. I'm pretty sure
that you'll find the usual weasel words somewhere in the documentation
that the libraries are provided as an additional service and no
guarantee is given concerning their accuracy
Eagle does come with lot of reasonable libs, but I would check each part
before using it. Personally I really don't like a lot of their silk
screen art work. Many parts simply have too much of it and all detail
could be on layer 51 rather than 21. Some have a lot of silk screen
running over pads, and while your board house can take care of this it
is bad practice.
If you want to use the Eagle libs as the basis for your own then that is
OK, but I would recommend that you only copy over the packages from the
ref-packages lib when you want to use one rather than ending up with
numerous footprints you will never use.
A quick look also shows that most of there SMT packages do not have a
clear indicator of pin 1 outwith the package body. This can be a real
pain in the ass when debugging and trying to probe individual pins. It
also makes life difficult for your assembly house if they are doing an
optical inspection. Copy a part over when you need it, check this and
then add a dot/circle at pin one outwith the body.
In fact when I look again some parts are completely missing any useful
silkscreen. Trust no-one, and check everything before you use it
You would only be crazy if you went ahead and used the libs without
checking their validity for yourself. The approach of making your own
libs is recommended.
cheers
David

Thanks very much for the help! Since you sound like an expert, I'm
going to ask for a favor... would you possibly send me a small library
with one through hole package and one surface mount package that you
think are perfect? I look through the libraries included with Eagle,
and there seems to be no standard. Some parts have no pin 1 mark, some
have a pin 1 mark inside the part footprint, some have silkscreen over
the pads, some have no silkscreen at all, some use a keepout boundary
and some do not, some have tGlue and some do not, some have the SMD pad
1 a different size, etc.

Sorry in advance if I'm asking for too much here!

Steve

[Paul Romanyszyn]

Post by Steve Kraft

Post by David Moodie
cheers
David

Thanks very much for the help! Since you sound like an expert, I'm
going to ask for a favor... would you possibly send me a small library
with one through hole package and one surface mount package that you
think are perfect? I look through the libraries included with Eagle,
and there seems to be no standard. Some parts have no pin 1 mark, some
have a pin 1 mark inside the part footprint, some have silkscreen over
the pads, some have no silkscreen at all, some use a keepout boundary
and some do not, some have tGlue and some do not, some have the SMD pad
1 a different size, etc.
Sorry in advance if I'm asking for too much here!
Steve

"perfect" is a broad term. The libs were made by people who did there
own pcb etching and drilling without a silk screen. Others that sent
their designs off to a cheap board house and require larger tolerances.
Others to a more expensive house and can support tighter tolerances.
A few years back 10 mil was a tight clearance. Now it is 6 mil to 8 mil.

You need to decide what you want and what your board house will support
such as drill sizes and clearances and customize your lib's to that.

Paul R.

[Steve Kraft]

Post by Paul Romanyszyn

Post by Steve Kraft

Post by David Moodie
cheers
David

Thanks very much for the help! Since you sound like an expert, I'm
going to ask for a favor... would you possibly send me a small
library with one through hole package and one surface mount package
that you think are perfect? I look through the libraries included
with Eagle, and there seems to be no standard. Some parts have no pin
1 mark, some have a pin 1 mark inside the part footprint, some have
silkscreen over the pads, some have no silkscreen at all, some use a
keepout boundary and some do not, some have tGlue and some do not,
some have the SMD pad 1 a different size, etc.
Sorry in advance if I'm asking for too much here!
Steve

"perfect" is a broad term. The libs were made by people who did there
own pcb etching and drilling without a silk screen. Others that sent
their designs off to a cheap board house and require larger tolerances.
Others to a more expensive house and can support tighter tolerances.
A few years back 10 mil was a tight clearance. Now it is 6 mil to 8 mil.
You need to decide what you want and what your board house will support
such as drill sizes and clearances and customize your lib's to that.
Paul R.

I agree with you entirely that I need to understand the capabilities of
the board house I am planning to use.

That being said, I was judging from David's answer that he is somewhat
of an expert who has faced problems similar to the ones I will face
(e.g. I'm guessing he's not a hobbyist etching and drilling his own
boards). In my opinion one great way to learn is to examine work
considered perfect by an expert ... that's why I'm hoping David might
send me a couple of examples of his work.

Steve

[David Moodie]

Post by Steve Kraft

Post by Paul Romanyszyn

Post by Steve Kraft

Post by David Moodie
cheers
David

Thanks very much for the help! Since you sound like an expert, I'm
going to ask for a favor... would you possibly send me a small
library with one through hole package and one surface mount package
that you think are perfect? I look through the libraries included
with Eagle, and there seems to be no standard. Some parts have no
pin 1 mark, some have a pin 1 mark inside the part footprint, some
have silkscreen over the pads, some have no silkscreen at all, some
use a keepout boundary and some do not, some have tGlue and some do
not, some have the SMD pad 1 a different size, etc.
Sorry in advance if I'm asking for too much here!
Steve

"perfect" is a broad term. The libs were made by people who did there
own pcb etching and drilling without a silk screen. Others that sent
their designs off to a cheap board house and require larger
tolerances. Others to a more expensive house and can support tighter
tolerances.
A few years back 10 mil was a tight clearance. Now it is 6 mil to 8 mil.
You need to decide what you want and what your board house will
support such as drill sizes and clearances and customize your lib's to
that.
Paul R.

I agree with you entirely that I need to understand the capabilities of
the board house I am planning to use.
That being said, I was judging from David's answer that he is somewhat
of an expert who has faced problems similar to the ones I will face
(e.g. I'm guessing he's not a hobbyist etching and drilling his own
boards). In my opinion one great way to learn is to examine work
considered perfect by an expert ... that's why I'm hoping David might
send me a couple of examples of his work.
Steve

Hi Steve

While I use Eagle in a professional environment, I wouldn't necessarily
consider myself an expert on library design, it is simply a tool that I use
occasionally to get the job done. My libs are far from perfect, as often I
throw a component together relatively quickly when it is needed. Most of my
packages lack any courtyard info on the Keepout layers.

However, for examples of what I'd consider near perfect packages have a look
a the land pattern calculator from PCB libraries.

http://www.pcblibraries.com/IPC-7351/LPCalcLE.asp

Their documentation on library construction is also good
http://www.pcblibraries.com/resources/GEN-docs.asp

I like their clean and simple silkscreen, and generally follow the
guidelines that this program spits out

cheers

David