If the balls haven't been deformed, the surface tension of the solder does help the part align. It's interesting to see the part get pulled into position as the solder melts. I've seen a switcher chip (can't remember the p/n at the moment) that has on the order of 80 balls, most of which are ground. Both for current and heat sinking. It's a small part, but is able to get rid of whatever heat it needs to as it is switching about 30W @ ~ 400 kHz as I recall. Joe T
On Tue, Apr 28, 2009 at 12:58 PM, John Griessen <[1][email protected]> wrote: I'm going to look into methods of dealing with BGAs in prototypes since Bob's tech says they're less trouble after a learning curve. I've heard and can imagine the way they pull themselves to alignment by surface tension between the grid of chip balls and the grid of lands on the pcb. Do BGAs use zones of balls to dissipate heat? John _______________________________________________ geda-user mailing list [2][email protected] [3]http://www.seul.org/cgi-bin/mailman/listinfo/geda-user References 1. mailto:[email protected] 2. mailto:[email protected] 3. http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
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