[SI-LIST] Re: Active components on a highspeed backplane

  • From: Dimiter Popoff <dimiter.popoff@xxxxxxxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 16 Oct 2003 22:49:11 +0300

Naveen,

> Have any of you folks had any designs where you had to place an active
> component on the backplane? In particular, I need to have a unique
> 'Board ID' for each backplane and the only feasible solution I can think
> of is to add a Serial EEPROM; but I am a little weary of this solution
> because of the risk of 'frying' the chip. 

I have done it more than once. My volumes are low, I typically reflow
the board for the components at the bottom side (being on top during
reflow), then again for those on the top side. The parts at the bottom
side hold because of surface tension, I have had SO-8 chips, SDRAMs (can't
think of the package name now), and various other stuff. Once I had
also a metal can quartz oscillator on the bottom and forgot it there
to reflow the board, I wanted to remove a BGA on the top. Well,
I got the BGA out allright, but the quartz oscillator had fallen
out - on a surface hotter than it would take and it died. Then again,
this was on a fairly complex first-ever prototype board, I had it
reflown > 30 times...

 To make it short, I see no problem with your EEPROM (SO-8?) on the card
bottom, I have done exactly this on another one.

Good luck,

Dimiter


--------------------------------------------------------------------
Dimiter Popoff
Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria
http://transgalactic.freeyellow.com
Phone: 00359/2/9923340

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