For those Technetters with interest in this thread, here are pieces of a side-discussion I had with Victor (with his permission):
-------------- beginning of discussion -------------------
Carl:
Can you be more specific? There are a variety of short circuit detection and location methods, including a car battery and jumper cables. (great-big-grin here . . .)
I spend a lot of time locating shorts, but your question is too open-ended for a helpful comment.
Victor:
Thank you very much for responding to my above stated inquiry.
Back in the mid eighty I used a Flir Thermal heat camera to assist with isolating shorts on a Printed Circuit Board assembly, PCBA. Camera technology was not as sensitive as it is today. The EMMI instrument was just coming around but too expensive. Anyway.... I was given a Flir Thermacam IR SC2000 system from a sister group. Therefore, I want to brush up my knowledge on this new technology. Some suspected shorts have been on the surface of the PWBA. Perhaps flux residue activated. Others have been on internal layers. I will have to find a source for a precision power supply and current meter setup. In the old days our sample was placed in a make shift refrigerator to keep the temperature low when power was applied to the PCBA and for camera sensitivity.
I worked in a panel factory many years ago and used a Tone Ohm Meter for short isolation and used the board net data to identify an external/internal layer. Power and ground shorts were more difficult to isolate. I conduct cross section analysis once the suspected short site has been determine, even for CAF……
I hope this helps……
Carl:
OK, that extra information helps to understand your subject line.
Thanks for the explanation.
*** Warning – thinly veiled commercial promotion below ***
I have a handheld FLIR camera that I use for other troubleshooting, but I don’t use it for thermally finding shorts on populated PC boards. I worry about my short circuit test currents suddenly turning into test voltages that might damage components if the short suddenly goes open. Before the FLIR camera, I also used quick-freeze frost-melt patterns and nematic liquid crystal sheets in hopes of identifying shorts. Those methods often work for hairline shorts but would fail when the short-blob was larger than the smallest conductors of the path. The Toneohm often worked where the conductors were accessible, but not on inner layers. My go-to device for short locating has been the ShortSniffer, but I must admit that I’m prejudiced, since it is my design. I’ve used it for hairline shorts as high as 500 Ohms, and also for ground-plane shorts. If you short-finding needs are not adequately covered by your current tools, check out the ShortSniffer website at http://www.shortsniffer.com/.
-------------- end of discussion -------------------
Later,
Carl
Carl B. Van Wormer, P.E., AE7GD
Senior Hardware Engineer
Cipher Engineering LLC
21195 NW Evergreen Pkwy Ste 209
Hillsboro, OR 97124-7167
503-617-7447x303
[log in to unmask] http://cipherengineering.com
-----Original Message-----
From: TechNet <[log in to unmask]> On Behalf Of Bhanu Sood
Sent: Tuesday, June 05, 2018 12:49 PM
To: [log in to unmask]
Subject: Re: [TN] PCBA Short detection/isolation, Flir IR Thermacam SC2000, Thermal Imaging
Be careful applying IR camera for short localization. Cross-section (and
impedance) of the sustained pathway may NOT support the current required for an effective IR imaging and subsequent localization.Start by identifying the offending nets and walk through (virtually) to locate the higher opportunity neighborhoods. From there, apply a lock-in IR (you will need pulse generator, power supply and a few other HW w/IR camera (Breitenstein, O., Langenkamp, M., Altmann, F., Katzer, D., Lindner, A., & Eggers, H. (2000). Microscopic lock-in thermography investigation of leakage sites in integrated circuits. *Review of scientific instruments*, *71*(11), 4155-4160) or go the SQUID way (Sood, Bhanu, and Michael Pecht.
"Conductive filament formation in printed circuit boards: effects of reflow conditions and flame retardants." *Journal of Materials Science: Materials in Electronics* 22.10 (2011): 1602.). Once localized, cross-section laterally (in case of inner layer short) to the suspect shorting site.
On Tue, Jun 5, 2018 at 11:44 AM, <[log in to unmask]> wrote:
> Hello Fellow TechNetters:
>
> I didn't get too many responses on my initial above inquiry.
> Therefore, I will post once again.
>
> Victor,
>
> From: Hernandez, Victor G
> Sent: Wednesday, May 16, 2018 1:24 PM
> To: TechNet E-Mail Forum
> Cc: Hernandez, Victor G
> Subject: PCBA Short detection/isolation, Flir IR Thermacam SC2000,
> Thermal Imaging
>
> Fellow TechNetters:
>
> Does anyone out there have experience that they can share on the above
> stated subject? I can be contacted off line if so desired.
>
> Victor,
>
--
Bhanu Sood
Tel: (202) 468-8449
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