marking pcb's

Z

zapp

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I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's PCB. I
would like to engrave a number or initials. Anyone have any suggestions?

Zapp
 
On Sun, 14 Dec 2003 20:21:31 -0500, "zapp" <zapp@nospam.com> Gave us:

I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's PCB. I
would like to engrave a number or initials. Anyone have any suggestions?
Click to expand...
Locktite Black, Gap filling super glue.

Use a serialized stamping tool (rubber stamp), and use the super
glue as the ink. The only way to remove it is by scrapping it.

You could also use a simple scribe to scrawl serializations on
therm. n Put drop os varnish over it, and tell them that damaged
varnish or serial numbers results in a Grade "F".
>
 
"zapp" wrote ...
I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's PCB.
I
would like to engrave a number or initials. Anyone have any suggestions?
Click to expand...
Numeric "punches" from the hardware store? Like these...
http://www.justoffbase-tools.co.uk/hand_tools/AK9294.html
 
Professional PCB layout engineers usually put part numbers, version numbers,
and layer ident marls (L1, l2 etc) on the artwork itself so that it appears
"in copper". I guess it's too late to do that.


"zapp" <zapp@nospam.com> wrote in message
news:pZ7Db.11170$C24.9870@bignews5.bellsouth.net...
I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's PCB.
I
would like to engrave a number or initials. Anyone have any suggestions?

Zapp
Click to expand...
 
"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:uReDb.78743$Pm4.2946156@phobos.telenet-ops.be...
Professional PCB layout engineers usually put part numbers, version
numbers,
and layer ident marls (L1, l2 etc) on the artwork itself so that it
appears
"in copper". I guess it's too late to do that.


"zapp" <zapp@nospam.com> wrote in message
news:pZ7Db.11170$C24.9870@bignews5.bellsouth.net...
I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's
PCB.
I
would like to engrave a number or initials. Anyone have any
suggestions?

Zapp




That's it CW....put it on the artwork....that way its etched in!......Ross
Click to expand...
 
On Tue, 16 Dec 2003 03:19:45 GMT, "Ross Mac"
<this.is.a.mung@example.invalid> Gave us:

"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:uReDb.78743$Pm4.2946156@phobos.telenet-ops.be...
Professional PCB layout engineers usually put part numbers, version
numbers,
and layer ident marls (L1, l2 etc) on the artwork itself so that it
appears
"in copper". I guess it's too late to do that.


"zapp" <zapp@nospam.com> wrote in message
news:pZ7Db.11170$C24.9870@bignews5.bellsouth.net...
I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's
PCB.
I
would like to engrave a number or initials. Anyone have any
suggestions?

Zapp




That's it CW....put it on the artwork....that way its etched in!......Ross
Click to expand...
The guy wants serializations. Who is going to pay the tooling
charge for each new gerber setup? Certainly not the PCB house.

One can place a "pad" on the board. A rectangular area of reference
designator silk screen area that marks the location for placement of
a high temperature serial number label.

Put conformal coat over that (the varnish types) to set up the ID.

Hell, any label under varnish will do, if it isn't going back into
the reflow oven. That is... if it is an SMT design. The high temp
labels are cool though, and quite resilient. The conformal coating
guarantees non tampering if put down with a high gloss look.

(Dolph's AC-41) Don't allow access to the varnish can, of course.
Don't mention anything about solvents.

One can also encode the edge of the PCB with a file for quite a
large number count. Four edges allows for a nice matrix, depending on
the size of the board. One could encode thousands of serializations
in that manner. Triangle file... small notches, no intrusion into any
conductors or power planes, of course. The same varnish will seal the
edges of the PCB to prevent tampering with that form of coding.

If he is the only one that knows the coding scheme, he could keep
them honest.
 
Just use a hand operated pencil engraver for metal, wood, glass, etc.- these
are cheap ($10-$20) and they can be used to etch a permanent serial number
into the board. Make sure that you don't etch over traces so you don't
accidentally cut any traces in half.

justme

"zapp" <zapp@nospam.com> wrote in message
news:pZ7Db.11170$C24.9870@bignews5.bellsouth.net...
I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's PCB.
I
would like to engrave a number or initials. Anyone have any suggestions?

Zapp
Click to expand...
 
"DarkMatter" <DarkMatter@thebarattheendoftheuniverse.org> wrote in message
news:hs1ttvk1u017dh1jmgdn8gick9srrjrf7d@4ax.com...


The guy wants serializations. Who is going to pay the tooling
charge for each new gerber setup? Certainly not the PCB house.
Click to expand...
I assumed each student had designed their own PCB so they were all different
anyway. Perhaps that's not what he meant.

If the yare all the same just engrave them with a cheap engraving nmachine.

Colin
 
"JustMe" <none@none.not> wrote in message
news:brmegt$as48$1@news3.infoave.net...
Just use a hand operated pencil engraver for metal, wood, glass, etc.-
these
are cheap ($10-$20) and they can be used to etch a permanent serial number
into the board. Make sure that you don't etch over traces so you don't
accidentally cut any traces in half.

justme

"zapp" <zapp@nospam.com> wrote in message
news:pZ7Db.11170$C24.9870@bignews5.bellsouth.net...
I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's
PCB.
I
would like to engrave a number or initials. Anyone have any
suggestions?

Zapp




That's the most common way!
Click to expand...
 
"DarkMatter" <DarkMatter@thebarattheendoftheuniverse.org> wrote in message
news:hs1ttvk1u017dh1jmgdn8gick9srrjrf7d@4ax.com...
On Tue, 16 Dec 2003 03:19:45 GMT, "Ross Mac"
this.is.a.mung@example.invalid> Gave us:


"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:uReDb.78743$Pm4.2946156@phobos.telenet-ops.be...
Professional PCB layout engineers usually put part numbers, version
numbers,
and layer ident marls (L1, l2 etc) on the artwork itself so that it
appears
"in copper". I guess it's too late to do that.


"zapp" <zapp@nospam.com> wrote in message
news:pZ7Db.11170$C24.9870@bignews5.bellsouth.net...
I need to mark around 50 student PCB's for a microprocessor design
lab.
This is to make sure that no one is cheating by using someone else's
PCB.
I
would like to engrave a number or initials. Anyone have any
suggestions?

Zapp




That's it CW....put it on the artwork....that way its etched
in!......Ross


The guy wants serializations. Who is going to pay the tooling
charge for each new gerber setup? Certainly not the PCB house.

One can place a "pad" on the board. A rectangular area of reference
designator silk screen area that marks the location for placement of
a high temperature serial number label.

Put conformal coat over that (the varnish types) to set up the ID.

Hell, any label under varnish will do, if it isn't going back into
the reflow oven. That is... if it is an SMT design. The high temp
labels are cool though, and quite resilient. The conformal coating
guarantees non tampering if put down with a high gloss look.

(Dolph's AC-41) Don't allow access to the varnish can, of course.
Don't mention anything about solvents.

One can also encode the edge of the PCB with a file for quite a
large number count. Four edges allows for a nice matrix, depending on
the size of the board. One could encode thousands of serializations
in that manner. Triangle file... small notches, no intrusion into any
conductors or power planes, of course. The same varnish will seal the
edges of the PCB to prevent tampering with that form of coding.

If he is the only one that knows the coding scheme, he could keep
them honest.
Odds are each board is different...so artwork would not be a
Click to expand...
problem....otherwise, break out the old engraver...that's the most common
way to track boards through a shop, other than cropping the corners I
suppose....
 
On Sun, 14 Dec 2003 17:21:31 -0800, zapp wrote
(in message <pZ7Db.11170$C24.9870@bignews5.bellsouth.net>):

I need to mark around 50 student PCB's for a microprocessor design lab.
This is to make sure that no one is cheating by using someone else's PCB. I
would like to engrave a number or initials. Anyone have any suggestions?
Click to expand...
Do you also mean such that no one will be able to duplicate the s/n on
another PCB? Is this a requirement? One can easily duplicate a fellow
student's PCB *design* and put their own s/n (assigned to their original PCB
by you) on it.

You need a method that is unique for each PCB, and not easily forged. Many of
the methods mentioned in response can be easily done by the "wayward"
student, ie, to a pinched PCB *design*.

A solution has not yet been suggested that meets these requirements.

I suggest a digital photo of the PCBs, both sides. No s/n required. Simply
compare the handed-in project to the photos you keep on file. 50 projects is
a bit much, I realize, but I don't know any other way to be sure the
handed-in *design* is the student's own.

Good luck,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
 
"DaveC" wrote ...
Do you also mean such that no one will be able to duplicate the s/n on
another PCB? Is this a requirement? One can easily duplicate a fellow
student's PCB *design* and put their own s/n (assigned to their original
PCB
by you) on it.
Click to expand...
My impression was that these are identical "project boards" etc.
Else it wouldn't really be an issue, would it?

You need a method that is unique for each PCB, and not easily forged. Many
of
the methods mentioned in response can be easily done by the "wayward"
student, ie, to a pinched PCB *design*.

A solution has not yet been suggested that meets these requirements.
Click to expand...
Using a conventional "vibrator" engraving tool is easily "forged"
OTOH, using the punches as I suggested makes it significantly more
difficult to cheat.

Or a very subtle (and secret) code of small notches on one edge?
 
On Tue, 16 Dec 2003 10:31:36 GMT, "CWatters"
<colin.watters@pandoraBOX.be> Gave us:

"DarkMatter" <DarkMatter@thebarattheendoftheuniverse.org> wrote in message
news:hs1ttvk1u017dh1jmgdn8gick9srrjrf7d@4ax.com...


The guy wants serializations. Who is going to pay the tooling
charge for each new gerber setup? Certainly not the PCB house.

I assumed each student had designed their own PCB so they were all different
anyway. Perhaps that's not what he meant.

If the yare all the same just engrave them with a cheap engraving nmachine.

Colin

The PCBs are the same. The folks building (read assembling) them
Click to expand...
differ. It seems to be a hand assembly skills exercise.

Any engraving should include being sealed with a varnish afterward.
 
On Tue, 16 Dec 2003 10:36:47 GMT, "Ross Mac"
<this.is.a.mung@example.invalid> Gave us:

Odds are each board is different...so artwork would not be a
problem....otherwise, break out the old engraver...that's the most common
way to track boards through a shop, other than cropping the corners I
suppose....
Click to expand...

Wrong. Odds are.. each board is the same, and each student is being
tested on assembly process ability.
 
On Tue, 16 Dec 2003 7:01:17 -0800, DaveC <me@privacy.net> Gave us:

A solution has not yet been suggested that meets these requirements.
Click to expand...

Bullshit. My edge notch encoding scheme makes unique, all but
un-decodable (except by the instructor) PCB coding/serializations.
 
On Tue, 16 Dec 2003 7:01:17 -0800, DaveC <me@privacy.net> Gave us:

I suggest a digital photo of the PCBs, both sides. No s/n required. Simply
compare the handed-in project to the photos you keep on file. 50 projects is
a bit much, I realize, but I don't know any other way to be sure the
handed-in *design* is the student's own.
Click to expand...

I'll bet that the PCBs are all the same, and the test is for
assembly skill as well as finished assy function.
 
On Tue, 16 Dec 2003 07:09:51 -0800, "Richard Crowley"
<rcrowley7@xprt.net> Gave us:

My impression was that these are identical "project boards" etc.
Else it wouldn't really be an issue, would it?
Click to expand...
Some of these readers' interpretive powers wane when they arrive
home from work. Some waned long ago.

I agree with you.
 
On Tue, 16 Dec 2003 07:09:51 -0800, "Richard Crowley"
<rcrowley7@xprt.net> Gave us:

Or a very subtle (and secret) code of small notches on one edge?
Click to expand...
That's what *I* suggested.
 
Thanks for all the replies! Elaborating, these are identical
microcontroller boards with a perfboard wirewrap area. After some time into
the semester, there will be many of hours of wirewrap work put into each
board. Hopefully, the identifying mark will prevent a student from casually
using another's work.

Varnish can be dissolved, someone seemed to mention. Is epoxy insoluble?
Also, does it come in clear forms? Perhaps epoxy over a paper label or
engraving.

The digital camera may work, but there are several lab instructors.


Zapp



"DarkMatter" <DarkMatter@thebarattheendoftheuniverse.org> wrote in message
news:79gvtvkvbi4559j4sd7tcjukdbsl02tggk@4ax.com...
On Tue, 16 Dec 2003 7:01:17 -0800, DaveC <me@privacy.net> Gave us:

I suggest a digital photo of the PCBs, both sides. No s/n required.
Simply
compare the handed-in project to the photos you keep on file. 50 projects
is
a bit much, I realize, but I don't know any other way to be sure the
handed-in *design* is the student's own.


I'll bet that the PCBs are all the same, and the test is for
assembly skill as well as finished assy function.
Click to expand...
 
zapp threw some tea leaves on the floor
and this is what they wrote:

I need to mark around 50 student PCB's for a microprocessor design lab.
Click to expand...
How are the pcbs designed and made ?

This is to make sure that no one is cheating by using someone else's PCB.
Click to expand...
Do you mean someone elses pcb *design* ?

I
would like to engrave a number or initials. Anyone have any suggestions?
Click to expand...
A hand engraver ?

Zapp
Click to expand...

--
Kind Regards from Terry
My Desktop is powered by GNU/LinuX, Gentoo-1.4_rc2
New Homepage: http://milkstone.d2.net.au/
** Linux Registration Number: 103931, http://counter.li.org **
 
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