We currently use a Huntron prober to test circuit boards and I would like to build a "Bed of Nails" to use with Labview to do detailed board testing. PIC will be involved somewhere. Has anyone built a tester from scratch or from a commercial frame? Any tips, or traps? boards are typically 6 X 8" and contain 10 to 15 16 pin DIP chips and 15 to 25 PTH diodes and resistors. All boards are double sided with components all on one side with an obsolete 22 pin board connector on one end. I think under 100 pins would cover my needs but that number may go up if the tester works. Looking to develop a tester for one board and expand it to test several different but related boards.
The cheap and easy method I've used was to create three additional
circuit boards for the tester pins. The bottom board had flat pads,
the middle board was spaced slightly above the bottom board and had
holes just larger than the pogo pins, and the top board was identical
to the middle board, but spaced a little above the middle board. Drop
the pogo pins in the holes and they make contact with the pads on the
bottom PCB. One could replace the middle and top boards with delrin
or some other insulating thick material as well.
The boards had screws with nuts to space them, and at certain
locations the screws would go past the top board to guide the unit
under test onto the top board. I usually used nuts to hold the unit
under test onto the tester, but one could also develop a hinged
overboard that holds the unit under test correctly.
The bottom board pads would terminate to appropiate connectors (in
this case JTAG, power, and an RS-232 connector)
I don't have the tester at hand, so I cannot provide pictures,
hopefully the description is adequate.
Previously I used a hardwood board. I drilled holes slight larger
than the pogo pins, stuck one end of a stripped wire in the hole, then
forced the pogo pin in. It was very fiddly, and rarely worked well so
I went to the PCB method. But for a few test points that are well
spaced apart, it should be fine.
If you have the flexibility for your development to make sure a few
mounting holes and all the test points are on a common 1/10" grid,
then you could make a fairly simple generic test bed.
-Adam
On 10/28/06, Tom Wehn <spam_OUTtomliveshereTakeThisOuTsbcglobal.net> wrote:
> We currently use a Huntron prober to test circuit boards and I would like to build a "Bed of Nails" to use with Labview to do detailed board testing. PIC will be involved somewhere. Has anyone built a tester from scratch or from a commercial frame? Any tips, or traps? boards are typically 6 X 8" and contain 10 to 15 16 pin DIP chips and 15 to 25 PTH diodes and resistors. All boards are double sided with components all on one side with an obsolete 22 pin board connector on one end. I think under 100 pins would cover my needs but that number may go up if the tester works. Looking to develop a tester for one board and expand it to test several different but related boards.
>
> Thanks in advance!
>
> Tom
> -
> The cheap and easy method I've used was to create three additional
> circuit boards for the tester pins. The bottom board had flat pads,
> the middle board was spaced slightly above the bottom board and had
> holes just larger than the pogo pins, and the top board was identical
> to the middle board, but spaced a little above the middle board. Drop
> the pogo pins in the holes and they make contact with the pads on the
> bottom PCB. One could replace the middle and top boards with delrin
> or some other insulating thick material as well.
>
> The boards had screws with nuts to space them, and at certain
> locations the screws would go past the top board to guide the unit
> under test onto the top board. I usually used nuts to hold the unit
> under test onto the tester, but one could also develop a hinged
> overboard that holds the unit under test correctly.
>
> The bottom board pads would terminate to appropiate connectors (in
> this case JTAG, power, and an RS-232 connector)
>
> I don't have the tester at hand, so I cannot provide pictures,
> hopefully the description is adequate.
Adam, I would love to see a picture. How looks the pogo pins ?
(ok I'll search on google)
The bed of nails has a standardized positions for nails ? That means
the PCB designer should position the test points on the PCB according
on his bed of nails doccumentation, or the bed of nails could be
reconfigurable for a particular grid dimension used on PCB ?
Vasile Surducan wrote:
> Adam, I would love to see a picture. How looks the pogo pins ?
> (ok I'll search on google)
>
> The bed of nails has a standardized positions for nails ? That means
> the PCB designer should position the test points on the PCB according
> on his bed of nails doccumentation, or the bed of nails could be
> reconfigurable for a particular grid dimension used on PCB ?
>
I used to write drivers for "bed of nails" testers (Company was called
Innovate; the 9000 was the largest, but they did smaller desk-based ones
too, if anyone's ever seen one). As shipped from the factory, you get
several thousand pins in a grid configuration, and that's it. What each
client does, using the Gerbers for the PCB under test, is have an
adapter board made up which breaks out the PCB test points - usually one
per net - onto the bed of nails array. The tester then has to map the
net test points onto the correct bed of nails pin using the software,
and the test is run on that basis.
> Vasile Surducan wrote:
>> The bed of nails has a standardized positions for nails ? That means
>> the PCB designer should position the test points on the PCB according
>> on his bed of nails doccumentation, or the bed of nails could be
>> reconfigurable for a particular grid dimension used on PCB ?
>
> I used to write drivers for "bed of nails" testers (Company was called
> Innovate; the 9000 was the largest, but they did smaller desk-based ones
> too, if anyone's ever seen one). As shipped from the factory, you get
> several thousand pins in a grid configuration, and that's it. What each
> client does, using the Gerbers for the PCB under test, is have an
> adapter board made up which breaks out the PCB test points - usually one
> per net - onto the bed of nails array. The tester then has to map the
> net test points onto the correct bed of nails pin using the software,
> and the test is run on that basis.
Another way to use them is to make a custom fixture for your custom test
setup. This allows your test setup to easily contact points in the circuit
that are not routed to connectors on the board. It also makes it
unnecessary for testing to plug in any connector you might have. Just place
the board in the fixture and everything you need (and have placed a pin
for) is contacted. For example the programming pins for ICSP.
It helps to identify those test nets when designing the schematic and make
sure they have an accessible via in the layout.
They have good pictures there. If you needed more than hobbyist
quantities I expect they could be found elsewhere for less. When I
ordered them they didn't have the holders. Now that they do you could
use a holder and one or two PCBs instead of the three PCB stack I
suggested earlier.
A pogo pin has at least three parts. A hollow tube, a spring, and a
rod. The bottom of the tube is crimped, the srping goes in, then the
bottom of the rod goes in, where the tube is crimped a little bit.
The rod can slide freely in and out, but is caught by the crimp so it
can't completely leave the tube. The spring pushes the rod
constantly, so it look and feels like a little pogo stick
The end of the rod is shaped for different purposes. Some are
chiseled, some are cup shaped, some flat, etc. I usually put a large
flat SMD pad with a small (via size) hole in the center and use the
pointy one.
I'm sure you can purchase huge bed of nail testers that have standard
positions and you simply load the pins you need. For anything more
than a few hundred uses, though, most places custom make a test
fixture which is designed around the PCB instead of the PCB being
designed with the test fixture in mind.
Usually the test fixtures sit on top of a generic bed of nails tester,
though, so they don't need to build a whole new tester each time, just
the board holder, pogo pin holder, and clamp setup.
I know some places even have automated test equipment, that move one
or more test points around. Very slow, but highly flexible.
Generally used for low quantity prototyping where high reliability is
more important than cost.
> > Drop
> > the pogo pins in the holes and they make contact with the pads on the
> > bottom PCB.
> Adam, I would love to see a picture. How looks the pogo pins ?
> (ok I'll search on google)
>
> The bed of nails has a standardized positions for nails ? That means
> the PCB designer should position the test points on the PCB according
> on his bed of nails doccumentation, or the bed of nails could be
> reconfigurable for a particular grid dimension used on PCB ?
>
> thx,
> Vasile
piclist-bounces@mit.edu wrote:
>> I usually used nuts to hold the unit
>> under test onto the tester, but one could also develop a hinged
>> overboard that holds the unit under test correctly.
That's the approach I took. We do 100% testing, so speed of test
directly impacts cost. After designing several testers for various
products, I developed a "generic" tester consisting of various modules
like ADC, DAC, relays, buffers, etc. These modules plug into a
motherboard of sorts (controlled by a PIC of course).
I'm not sure what size picture I can post, so I'll try a separate post
with a picture of the bed of nails with hinged cover.
piclist-bounces@mit.edu wrote:
> I'm not sure what size picture I can post, so I'll try a
> separate post with a picture of the bed of nails with hinged cover.
of course it got rejected. If anyone really, really wants to see the
pictures I could put them on a webpage.
>-----Original Message-----
>From: .....piclist-bouncesKILLspam.....mit.edu On Behalf Of M. Adam Davis
>Sent: Monday, October 30, 2006 9:36 AM
>
>I purchased my pogo pins from
>http://www.solarbotics.com/
>In the pins section:
>www.solarbotics.com/products/index.php?scdfa-250100084-viewC
>ategory-categoryzq314=true&frm=sbsb
>
>They have good pictures there. If you needed more than hobbyist
>quantities I expect they could be found elsewhere for less. When I
These pins look like the pins manufactured by Interconnect Devices, Inc. http://www.idinet.com.
>> I usually used nuts to hold the unit
>> under test onto the tester, but one could also develop a hinged
>> overboard that holds the unit under test correctly.
The factory where I did my apprenticeship made jigs with pogo pins which
contacted onto the pads where the wires were soldered when the PCB was
assembled into the final unit, and had suitable diameter brass pins which
went through the mounting screw holes, and a hinged brass frame around the
perimeter of the PCB to hold it down.
Pogo pins are available from Harwin in the UK, through Farnell. Search for
"Harwin probe" on the farnell website, and there is a whole variety pith
pointed, concave, or serrated ends.
>
>>> I usually used nuts to hold the unit
>>> under test onto the tester, but one could also develop a hinged
>>> overboard that holds the unit under test correctly.
>
> The factory where I did my apprenticeship made jigs with pogo pins which
> contacted onto the pads where the wires were soldered when the PCB was
> assembled into the final unit, and had suitable diameter brass pins which
> went through the mounting screw holes, and a hinged brass frame around the
> perimeter of the PCB to hold it down.
>
> Pogo pins are available from Harwin in the UK, through Farnell. Search for
> "Harwin probe" on the farnell website, and there is a whole variety pith
> pointed, concave, or serrated ends.
>
You can also sample or buy pogo or spring pins from Mill-Max. http://www.mill-max.com
They scored in my book as they had and sent both hardcopy and cd catalogs with
my samples ;-]
> >I purchased my pogo pins from
> >http://www.solarbotics.com/
> >In the pins section:
> >www.solarbotics.com/products/index.php?scdfa-250100084-viewC
> >ategory-categoryzq314=true&frm=sbsb
> >
> >They have good pictures there. If you needed more than hobbyist
> >quantities I expect they could be found elsewhere for less. When I
>
>These pins look like the pins manufactured by Interconnect Devices, Inc.
>http://www.idinet.com.
>
>Paul
>
>
there seems to be some interest in this. I'll take you up on that. I'll
be glad to answer questions (and I welcome constructive criticism) once
the pictures are posted. Do keep in mind that was version 1.0. We've
made some refinements to version 2 (under construction right now, no
pictures available yet)
> piclist-bouncesEraseME.....mit.edu wrote:
> > If you email them to me directly ( EraseMEstienmangmail.com
> > ) I can post them on my website: http://ubasics.com
>
> there seems to be some interest in this. I'll take you up on that. I'll
> be glad to answer questions (and I welcome constructive criticism) once
> the pictures are posted. Do keep in mind that was version 1.0. We've
> made some refinements to version 2 (under construction right now, no
> pictures available yet)
>
>
>
>
piclist-bounces@mit.edu wrote:
> I would be happy to host that picture and any description we
> can put together in the PIC FAQ at piclist.com
I'm happy to provide further input if there is interest. I would love to
share everything, but I can hear managers uttering the words
"competitive advantage" already. We did spend a fair amount of resources
on this project. I probably won't be allowed to share pcb layouts,
Windows source code, etc. But certainly I should be able to share
concepts, partial schematics, problems encountered, etc.
sbcglobal.net> wrote:
