[SI-LIST] Re: How to solve short circuit issues in high dense pcbs
- From: "Pommerenke, David" <davidjp@xxxxxxx>
- To: "Danny Damhave" <dd@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 1 Nov 2011 17:20:41 -0500
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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