From: firstname.lastname@example.org (Glen Walpert)
Subject: Re: PBGA Solder...HELP....
X-Newsreader: News Xpress 2.01
Date: Sun, 12 Jan 2003 16:06:22 GMT
NNTP-Posting-Date: Sun, 12 Jan 2003 11:06:22 EST
Organization: Net Access (netaxs.com)
In article , "KT88" wrote:
>I have get some ADSP21160 samples, and my problem is that I don't know how
>may I solder it.
>The socket is PBGA (plastic ball grid array).
>Some suggestion will be appreciated...
I have started experimenting with PBGA soldering, and while it is doable with
hot air it is not simple. The basic concept is identical to the method used
for precision furnace brazing for at least 50 years before the invention of
BGA: heat the entire assembly to just below the melting point of the solder
and let it soak for long enough for the temperatures to largely equalize, but
not so long that the flux deactivates. Then quickly bump the temperature
above the solder melting point, and cool moderatly slowly to avoid inducing
excess stress in the joints. The commercial rework equipment I have seen uses
hot air from both sides, with time/temperature profiles carefully tuned for
each type of part.
An alternative method I have had some success with on small BGAs is to heat
the entire board and part to about 20 C below solder melting, with no low
melting point plastic parts mounted, on an electric pancake griddle, spaced
off the surface with short standoffs, and insulated with cardboard. Soak
around 2 minutes, then remove the cardboard cover and apply heat through the
package with the same hot air gun I use for regular SMT. The part will move
as it centers on the pads as the solder melts, same as regular SMT, so you can
see when the solder is melted. Removal is done the same way, except before
you can reuse the part you must make new solder balls by screening solder
paste onto the cleaned part through an appropriate mask and melting with
preheat and hot air again. Practice on something you don't care about. With
enough temperature and flow controlled hot air and appropriate home-made
nozzles, I expect this to work on medium size BGAs also.
chg not -> net to reply