The cap might test OK if the via or BGA ball is actually not used or the test is DC. 

In a switching circuit the cap is going to effect the signal that it ias coupled to. 

The cap violates electrical spacing and if with vibration it breaks free and moves then you have to remove the BGA and fix it anyway but at much higher cost. 
----- Original Message ----- 
From: "Genny Gibbard" <[log in to unmask]> 
To: [log in to unmask] 
Sent: Friday, February 11, 2011 12:37:01 PM 
Subject: [TN] FW: What would you do? 

Please see the link below. 
Cap under BGA.   
Inquiring minds question: If the board tested out OK, would you ever 
consider just leaving this here? The part is a ceramic cap. 


________________________________ 

From: Steve Gregory [mailto:[log in to unmask]] 
Sent: February 11, 2011 10:37 AM 
To: Genny   
 Subject: RE: What would you do? 



Hi Genny, 

  

I have your picture posted: 

  

http://stevezeva.homestead.com/part_under_BGA.jpg 

  

It depends. First thing I would want to know, what is this? Is it metal? 
If it is, it would be a violation of electrical spacing and I wouldn't 
leave it there. 

  

Does the ball have any function? Some balls have no function. 

What is this board for? A critical application? If it is then no. 

How scarce is the BGA? 

  

There's a lot of "it depends" that would have to be answered before I 
would consider it. 

  

My first reaction is that I wouldn't leave it there. But there may be 
some circumstances that I might consider it. 

  

Steve 

  

From: Genny   

 Sent: Friday, February 11, 2011 10:32 AM 
To: Steve Gregory 
Subject: What would you do? 

  

<<part under BGA.jpg>> 

Genny 


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