Homebrew PCBs

At 12:47 PM 3/24/2008 -0400, you wrote:

>... and would like to be able to measure trace widths, etc
>wthout reinventing the wheel.

Has anyone looked into "IPC-9251"?

http://dcchapters.ipc.org/html/downloads.htm

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[from the web page...]

IPC-9251 
Test Vehicles for Evaluating Fine Line Capability 

Conductor Analysis Technologies, Inc. and E. I. DuPont Company
developed test patterns for evaluating fine line capabilities, and
IPC has been provided permission to distribute the data to the
industry. The effort has been coordinated by the Etch and Strip
Subcommittee (4-15) of the Fabrication Processes Committee (4-10)
of IPC and is now being made available to industry for free. You will
be asked to complete a short information form before downloading.

Download IPC-9251 (.zipped file)
[ http://dcchapters.ipc.org/html/9251form.htm ]

---------------------------------------------------------------
[from the pdf included in the downloaded zip...]

The files are named IPC221.ZIP and IPC441.ZIP. Both designs are 18- by
24-inch with 352 one-inch-square modules arranged in 16 rows and 22
columns. IPC221.ZIP has multi-pitch modules with 2-, 3-, 4-, and 5-mil
lines separated by 2-, 3-, and 4-mil spaces, respectively; IPC441.ZIP
has multi-pitch modules with 4-, 5-, 6-, and 7-mil lines separated by
4-, 5-, and 6-mil spaces, respectively. Each design contains an aperture
list and a \ufffdREADME\ufffd file that describes the pattern, and provides
recommended processing procedures.

The IPC441 design is useful to evaluate process uniformity, while the
IPC221 design is intended for evaluating narrow lines and spaces. Both
patterns may be inspected optically or tested electrically. Precision
electrical resistance measurements from the patterns can provide
conductor and space defect density, and conductor width and height
uniformity.

---------------------------------------------------------------

The idea is to  run off a batch of  these boards then send them (along
with some number of $US) to a testing service who will evaluate them and
return a report of their quality.  If you're making boards for sale to
NASA/ESA/CSA/JSA, such a report might come in handy.

bad: they're Gerber files
good: "... tested electrically" (check out the patterns)
bad: "...18- by 24-inch"
good: "...one-inch-square modules"

I believe one of the 1" module patterns would be worthwhile for
evaluating the work done here; the idea of using precise resistance
measurements to qualify a board is intriguing.

I wanted to extract one of the modules from the huge design, but by the
time I found a workable Gerber viewer and sorted out aperature issues, I
had lost my ambition to hand-edit/awk the files.   Recreating the
patterns programmatically is left as an exercise for javag^H^H^H^H^H the
student.

I thought I first heard about IPC-9251 in one of the Riston spec sheets,
but can't find the reference right now.  If I can find the time I'll
contact CAT/IPC/DuPont to see how they would feel about allowing a copy
of their files here for our reference.

Mike