BGA central ground matrix

In fact,

This link is also confused.  They talk about ferrous vs non ferrous, and 
skin effect, too.  The basic effect has nothing to do with ferrous or 
skin effects.

austin

austin wrote:

> dp,
> 
> Perhaps these folks say it better:
> 
> "Proximity Effect"  As true at DC as at any frequency
> 
> http://www.cda.org.uk/Megab2/elecapps/pub22/sec4.htm#Proximity%20Effect
> 
> Commonly misunderstood.
> 
> You tell me what is happening?
> 
> I say the DC magnetic field affects current flow.
> 
> Austin
> 
> dp wrote:
> 
>> Austin Lesea wrote:
>>
>>> .....
>>> The static magnetic field will force the static electric field to be
>>> confined to the area adjacent to the current flow in the opposite 
>>> direction.
>>>
>>> .....
>>
>>
>>
>> Austin,
>>
>> sure you did not really mean that? Static magnetic fields do not
>> affect electric field(s) according to physics.
>>
>> Dimiter
>>
>> ------------------------------------------------------
>> Dimiter Popoff               Transgalactic Instruments
>>
>> http://www.tgi-sci.com
>> ------------------------------------------------------
>>

Further,

Anyone who can point to a clear and simple explanation, please do.

When I first mentioned this to our packaging group, the lead engineer 
said "oh yes, I see this in the EM simulations..."

So, I know I am not imagining it!

Austin

austin wrote:
> Further,
>
> Anyone who can point to a clear and simple explanation, please do.
>
> When I first mentioned this to our packaging group, the lead engineer
> said "oh yes, I see this in the EM simulations..."
>
> So, I know I am not imagining it!
>
> Austin

Austin,

the only way a simulator can see DC current
resulting from a static magnetic field is a software bug
or, worse, misconcepted basics behind the software.
 If physics would allow that we would have unlimited
energy for free... just put a magnet next to a conductor
and off you go... :-)

Perhaps you meant moving (mechanically) a static magnetic
field relative to some conductors? This would of course
do the job.

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------

dp,

I know you do not belive me.  And you haven't ever solved Maxwells 
equations for this case (or else you would see it).

I am not going to convince you, so I will not try, but it is a real 
effect, and it really happens.

I also admit that it is greatly misunderstood (after all, Westinghouse 
believed as you do, util they made a million dollar mistake by building 
it, and experiencing it first hand).

Austin

dp wrote:

> austin wrote:
> 
>>Further,
>>
>>Anyone who can point to a clear and simple explanation, please do.
>>
>>When I first mentioned this to our packaging group, the lead engineer
>>said "oh yes, I see this in the EM simulations..."
>>
>>So, I know I am not imagining it!
>>
>>Austin
> 
> 
> Austin,
> 
> the only way a simulator can see DC current
> resulting from a static magnetic field is a software bug
> or, worse, misconcepted basics behind the software.
>  If physics would allow that we would have unlimited
> energy for free... just put a magnet next to a conductor
> and off you go... :-)
> 
> Perhaps you meant moving (mechanically) a static magnetic
> field relative to some conductors? This would of course
> do the job.
> 
> Dimiter
> 
> ------------------------------------------------------
> Dimiter Popoff               Transgalactic Instruments
> 
> http://www.tgi-sci.com
> ------------------------------------------------------
> 

austin wrote:
> dp,
>
> I know you do not belive me.  And you haven't ever solved Maxwells
> equations for this case (or else you would see it).
>

Austin,
I also think it is some kind of misunderstanding, of course.

Perhaps (if you refer to the railroad story) the motion came
from the train moving, or something else they just did
not take into account initially, things like that do happen.

 However, for the case of the BGA socket, this cannot
apply. If there is no DC current through the central pads
it can only be because of higher active resistance or,
more likely, because there is little if any (leakage only,
I guess) DC current to talk about. Come to think of it,
it should be that last one.

 BTW,  my (1.27 mm pitched) BGA designs all have a
 via hole in the center of each pad, this is OK if you run
small quantities.
 The most important drawback is the necessity to once
fry the BGA chips belly up with some flux, before you use
them on the board, lest some of the balls get detached
(come coldly soldered from chip vendor) and flow through
the board forming a bubble .... (I had this several times until
I figured out how to deal with the problem).
 The most important advantage is obviously having access
to all the BGA pads with the scope etc.

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------

austin wrote:
> dp,
> 
> I know you do not belive me.  And you haven't ever solved Maxwells 
> equations for this case (or else you would see it).
> 
> I am not going to convince you, so I will not try, but it is a real 
> effect, and it really happens.
> 
> I also admit that it is greatly misunderstood (after all, Westinghouse 
> believed as you do, util they made a million dollar mistake by building 
> it, and experiencing it first hand).

  Take a magnet near the front of a Shadow mask CRT, and you can
clearly see the effect a magnet has on moving (dc) electrons.
  DC current requires electrons to move, even if the ammeter does not.

-jg

dp,

As I said, you do not believe me.

Go run the simulation for a 6X6 array.

The outer wall of 6 is + (6+6+3+4, the perimeter), and all the inner 5X5 
(25 conductors) are -.

Then look at the distribution of current at DC.

I did find one article on furnaces, which showed the proximity effect on 
carbon electrodes, but it also made mention of frequency effects, and 
seemed unclear on what they saw.  They clearly saw what I describe in 
the plots of current.  But, they also attributed it to the 50 Hz AC 
field (which is pretty absurd....skin effect at 50 Hz is negligable!).

As I said, well misunderstood.  Even after looking at the answer, they 
explained it wrongly.

Austin

dp wrote:

> austin wrote:
> 
>>dp,
>>
>>I know you do not belive me.  And you haven't ever solved Maxwells
>>equations for this case (or else you would see it).
>>
> 
> 
> Austin,
> I also think it is some kind of misunderstanding, of course.
> 
> Perhaps (if you refer to the railroad story) the motion came
> from the train moving, or something else they just did
> not take into account initially, things like that do happen.
> 
>  However, for the case of the BGA socket, this cannot
> apply. If there is no DC current through the central pads
> it can only be because of higher active resistance or,
> more likely, because there is little if any (leakage only,
> I guess) DC current to talk about. Come to think of it,
> it should be that last one.
> 
>  BTW,  my (1.27 mm pitched) BGA designs all have a
>  via hole in the center of each pad, this is OK if you run
> small quantities.
>  The most important drawback is the necessity to once
> fry the BGA chips belly up with some flux, before you use
> them on the board, lest some of the balls get detached
> (come coldly soldered from chip vendor) and flow through
> the board forming a bubble .... (I had this several times until
> I figured out how to deal with the problem).
>  The most important advantage is obviously having access
> to all the BGA pads with the scope etc.
> 
> Dimiter
> 
> ------------------------------------------------------
> Dimiter Popoff               Transgalactic Instruments
> 
> http://www.tgi-sci.com
> ------------------------------------------------------
> 

Jim Granville wrote:
> austin wrote:
> > dp,
> >
> > I know you do not belive me.  And you haven't ever solved Maxwells
> > equations for this case (or else you would see it).
> >
> > I am not going to convince you, so I will not try, but it is a real
> > effect, and it really happens.
> >
> > I also admit that it is greatly misunderstood (after all, Westinghouse
> > believed as you do, util they made a million dollar mistake by building
> > it, and experiencing it first hand).
>
>   Take a magnet near the front of a Shadow mask CRT, and you can
> clearly see the effect a magnet has on moving (dc) electrons.
>   DC current requires electrons to move, even if the ammeter does not.
>
> -jg

High school physics is sufficient to know you can deflect the beam of
electrons because of the two interacting magnetic fields, the one the
electrons produce when moving with the one you apply with your
magnet.
 The DC current value remains unchanged, I hope you are aware of
that.

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------

austin wrote:
> dp,
>
> As I said, you do not believe me.
>
> Go run the simulation for a 6X6 array.
>
> The outer wall of 6 is + (6+6+3+4, the perimeter), and all the inner 5X5
> (25 conductors) are -.
>
> Then look at the distribution of current at DC.
>
> I did find one article on furnaces, which showed the proximity effect on
> carbon electrodes, but it also made mention of frequency effects, and
> seemed unclear on what they saw.  They clearly saw what I describe in
> the plots of current.  But, they also attributed it to the 50 Hz AC
> field (which is pretty absurd....skin effect at 50 Hz is negligable!).
>
> As I said, well misunderstood.  Even after looking at the answer, they
> explained it wrongly.
>
> Austin
>
> dp wrote:
>
> > austin wrote:
> >
> >>dp,
> >>
> >>I know you do not belive me.  And you haven't ever solved Maxwells
> >>equations for this case (or else you would see it).
> >>
> >
> >
> > Austin,
> > I also think it is some kind of misunderstanding, of course.
> >
> > Perhaps (if you refer to the railroad story) the motion came
> > from the train moving, or something else they just did
> > not take into account initially, things like that do happen.
> >
> >  However, for the case of the BGA socket, this cannot
> > apply. If there is no DC current through the central pads
> > it can only be because of higher active resistance or,
> > more likely, because there is little if any (leakage only,
> > I guess) DC current to talk about. Come to think of it,
> > it should be that last one.
> >
> >  BTW,  my (1.27 mm pitched) BGA designs all have a
> >  via hole in the center of each pad, this is OK if you run
> > small quantities.
> >  The most important drawback is the necessity to once
> > fry the BGA chips belly up with some flux, before you use
> > them on the board, lest some of the balls get detached
> > (come coldly soldered from chip vendor) and flow through
> > the board forming a bubble .... (I had this several times until
> > I figured out how to deal with the problem).
> >  The most important advantage is obviously having access
> > to all the BGA pads with the scope etc.
> >
> > Dimiter
> >
> > ------------------------------------------------------
> > Dimiter Popoff               Transgalactic Instruments
> >
> > http://www.tgi-sci.com
> > ------------------------------------------------------
> >

Austin,
I do believe you know what you are talking about.

I just do not accept the explanation - physics, as we know it,
says it must be different.

I am pretty sure you don't just assume there is little,
if any DC current flowing through the central BGA pads,
you know it is so. It just cannot be explained by any
static magnetic field, that's all. My assumption
is that there just is no DC current, it can be measured
as DC once it has been summed up in the power/ground
plane capacitance, decoupling capacitors etc. With CMOS
chips, you actually have only leakage DC current, which
is orders of magnitude lower than what I believe we are
talking about. The rest is only AC.

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------

Austin did not claim that the current changes, just that it takes a
different path.
I look at it this way:
Everything else being equal, the dc current would take the path that
puts the least energy into the magnetic field. In other words, it
minimizes the rea of the current loop.
But opposing that is the resistive drop if all current were to use the
smallest loop. So the current finds the right balance. Nature is smart,
and consistent.
Peter Alfke