Re: gEDA-user: solderpaste on pads for BGAs

[Stefan Salewski <mail@xxxxxxxxxxxx>]

On Thu, 2010-11-18 at 09:17 -0500, Rick Collins wrote:
> Specifically, the solder balls on the part are to provide some space 
> between the part and the board.  The solder paste is as large as the 
> pad and makes sure the full pad is wet with solder and completes the 
> connection.
> 
> Rick
> 
> 
> At 04:23 AM 11/18/2010, you wrote:
> >Hi all,
> >
> >
> >I'd like to ask if solder-paste is necessary for BGAs. The BGA already has
> >some tin, so the solder-paste on the pad wold be a bad idea.
> >
> >Do I miss something?
> >

I have never soldered BGA myself, but I have read that for new BGA parts
and PCB boards made by professionals (gold or  tin plated pads, solder
mask) only flux is used, no paste containing tin.

The tin on the BGA balls should be sufficient.

For repairing/rework or home made boards solder paste may be necessary.
(That may be wrong, whenever I need to do soldering BGA myself I will do
some more research.)

I think, if the BGA device is only available green/ROHS/leadfree then
paste with lead may be helpful indeed?




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