[SI-LIST] Re: How to solve short circuit issues in high dense pcbs
- From: johndp@xxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 02 Nov 2011 14:03:30 +0000
If you use a low voltage ( low enough as to not turn on the ICs) and current
limited supply, you can use a thermal imaging camera to show local heating in
the PCB.
Regards
John
davidjp@xxxxxxx wrote:
> Danny,
>
> Use magnetic field tracking.
>
> A method is to take a signal generator and a power amplifier and apply a low
> frequency to the PCB. You may need an Ampere or so. The frequency depends on
> the bulk capacitance, select the frequency as high as possible, but low
> enough such that the current flows through the short, not via the large
> capacitors. Next you need a magnetic field probe useful for that frequency. A
> Hall effect sensor, a GMR sensor (check NVE's offerings) works pretty well.
> Attach a narrow band amplifier behind the magnetic field sensor, tuned to the
> frequency you are using (like 10Hz), then begin searching the board for areas
> with strong magnetic field.
>
> You can try DC current, but the magnetic field of the earth is kind of
> strong, so you will have to use an on/off method to see changes in teh field
> between having DC current and having no DC current.
>
>
> David Pommerenke
>
> ________________________________
>
> From: si-list-bounce@xxxxxxxxxxxxx on behalf of Danny Damhave
> Sent: Tue 11/1/2011 1:31 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: How to solve short circuit issues in high dense pcbs
>
>
>
> Hi Kiruba
> If not already done it is also a good idea to check the orientation of all
> the ICs and that all land patterns for the ICs are correct (right pitch etc.)
> I have seen both causes shorts.
> BR
> Danny Damhave
> On 31/10/2011, at 09.01, rskiruban wrote:
>
> > Hi All,
> > One of my board having a short circuit (Zero Ohms) across a power supply
> > (That supply connects to thousands of decoupling capacitors and 44 BGAs)
> > and Ground. Is there any method to identify the route cause for the short
> > without removing any components?
> >
> > Note:
> > ####
> > 1. The board is not yet powered on.
> > 2. It was verified that the PCB doesn't contains any short across supplies
> > before board assembly.
> >
> >
> > Thanks and regards
> > Kiruba Sankar
> > Project leader
> > Hardware Design & Development
> > Email: rskiruban@xxxxxxxxxxxxxxxxxx
> > web: www.datapatternsindia.com
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