The entire area. You can also pick and place the BGA into a heated flux tray that applies flux over just 50% (the bottom half) of the ball, similar to a flip chip placer, then the BGA is placed on the pads on the PWB.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
Sent: Wednesday, January 26, 2011 1:11 PM
To: [log in to unmask]
Subject: Re: [TN] Lead Free / Lead policy

Do you flux just the pads, or the entire area? It seems like it would be difficult 
to flux only the pads, you would have to screen print flux or something.

Blair

On Wed, 26 Jan 2011 08:56:53 -0600, Stadem, Richard D. <Richard.S@GD-
AIS.COM> wrote:

>Thanks, Mike, another point I forgot to mention.
>When not using solder paste for BGAs, the pads are fluxed with a very fine 
sheen of the proper tacky flux.
>They should be all the same chemistry, never mix them.
>Again, QUALIFY YOUR PROCESS AND MATERIALS.
>

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