Paul,
I've done it without problem, it is non preferred, but will be no less reliable than the BGA without the ball.  I can only envision a thump (tech term) during liquidous that cause a spattering.  This is of course based on the BGA in question is sound design on its on merit which is not necessarily a given.
Brad
  ----- Original Message ----- 
  From: Black, Paul<mailto:[log in to unmask]> 
  To: [log in to unmask]<mailto:[log in to unmask]> 
  Sent: Monday, July 17, 2006 12:02 PM
  Subject: [TN] BGA Pad Missing on Board


  Hi Everyone,

  I have a quick question on BGA's. I have a board that is laid out for a BGA that the manufacturer is still developing. In the meantime, it can be populated with a different BGA from the same manufacturer and functionally it works fine. My problem is that the board layout has a location where there is no BGA pad. The newer part has no ball in that area but the one I am currently using does have a ball there. Are there any potential problems of having a BGA ball reflowing but not having a pad to bond with?

  Thank you, 
  Paul Black 
  Manufacturing Engineer 
  Kronos 

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