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Intermittent contact

Intermittent contact
« on: August 20, 2009, 12:22:11 pm »
Access 2 prober.  I'm having real issues with consistent good contact for/with the robot probe.  I've lowered the down position & tried different pins with no real success.  Just looking for any suggestions that might mitigate my having to hand-reprobe. 

Thanks.
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Re: Intermittent contact
« Reply #1 on: August 20, 2009, 02:02:02 pm »
I am assuming these boards are conformal coated? Getting consistent contact is always an issue. A couple of things to look at besides what you have tried already...
Make sure the board is well supported and has minimal flex during probing. Board bounce can cause intermittent opens.
Cleaning the board with alcohol or other mild (but safe) solvent may help reduce opens when probing especially if the board is from a dirty environment.
You may need to consider partially removing the coating on the board to get good contact. The Access Prober may get through 95% of the time but it is the other 5% that is annoying.

Hope this helps.

Curtis

 
The most important troubleshooting tool is your eyes.

Re: Intermittent contact
« Reply #2 on: August 21, 2009, 07:30:15 am »
You the man, Curtis.  I hadn't considered cleaning the board prior to testing.  I'll give it a shot.  The board support might actually come in handy as well; I've got relatively small PCBs, but thinking back, the do flex a bit during the testing.  I hadn't thought it would be enough to interfere with the prober connection, but then, maybe it does.  I'll give it a shot. 

I'm a bit disappointed at the lack of real pick-up for this forum.  I really thought there would be more involvement by now. 

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Re: Intermittent contact
« Reply #3 on: August 21, 2009, 11:07:07 am »
It may take some time for the forum to catch on but it is pretty a matter of getting the news out. Feel free to spread the word!

Thanks.

Curtis
The most important troubleshooting tool is your eyes.

Re: Intermittent contact
« Reply #4 on: November 14, 2009, 06:23:38 am »
AES_Wind, depending on how 'marginal' the contact is you could try a heavier spring rate in the probe or setting the teach height a little lower so that the spring tension is raised through more compression.

Steve.
English may be a strange language but I can assure you that an empty-head and an open-mind are not the same thing!

gman

Re: Intermittent contact
« Reply #5 on: November 16, 2009, 11:15:21 am »
If you recently changed the prober tip and performed an offset as stated in the manual, your teach height settings may have changed, especially if you reset to factory defaults in the offset tab. Changing the Z in the Offset tab will have an effect on the Teach Height tab Sequence Z Down and Sequence Z Up settings.  Write down your teach height Z down and Z up settings before performing the offset. That way, after changing your tip and doing the offset you can see if the settings have changed and if so, you can put them back. Otherwise, you will have to perform the teach height after the offset. Hope this helps!

Re: Intermittent contact
« Reply #6 on: November 16, 2009, 11:38:18 am »
Gentlemen,

I do appreciate the feedback you have provided.  I have in fact solved my problem (mostly) by setting my height/down positions to down and more down.  I feel almost as if I'm drilling for oil, but my faulty signatures  and opens have been greatly reduced.  There is still a bit more of hand probing than I would like, but, mitigation is mitigation, and beggars cannot be picky. 

Thanks again.

Rob
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gman

Re: Intermittent contact
« Reply #7 on: November 16, 2009, 11:46:28 am »
You can also check to see if your prober tip has become "loose" within the tube it slides up and down in. When I start getting grounds with slight resistance instead of direct shorts and faulty signatures throughout the board, that's usually a sign the tip needs replacing even if it's still needle sharp.