Wet: Adhere, join, bond....        Not melt 





-----Original Message-----
From: Kane, Amol (349) [mailto:[log in to unmask]] 
Sent: Friday, June 02, 2006 10:11 AM
To: TechNet E-Mail Forum; Dehoyos, Ramon
Cc: [log in to unmask]
Subject: RE: [TN] BGA solder

Hi Ramon,
What do u mean by wet? Do you mean melt? ........What reflow profile was
used? If SnPb temperatures were used, then SAC balls will not reflow and
form a homogenous joint, which creates reliability issues........a sort
of a hybrid profile is needed to solder backward compatible BGAs using
SnPb solder.....depending upon the % of solder volume of SAC BAG to the
% of solder volume of SNPb on the pad, the SAC can melt anywhere from
210 to 215 degree C. the key is to hold it above that temp just enough
to melt all the SAC and dissolve it in the SnPb to form a homogenous
microstructure, but not to overheat the SnPb components

Wow! Haven't seen the Mixed BGA scenario....not yet atleast!

Amol Kane
M.S (Industrial Eng.)
Process Engineer
Harvard Custom Manufacturing
941 Route 38  Owego, NY 13827
Phone: (607) 687-7669 x349
[log in to unmask]

 -----Original Message-----
From:   TechNet [mailto:[log in to unmask]]  On Behalf Of Dehoyos, Ramon
Sent:   Friday, June 02, 2006 9:55 AM
To:     [log in to unmask]
Subject:        [TN] BGA solder

        Two experiences were shared with  me and would like them to be
known for comments. In one instance a COTS BGA  was used on a prototype.
It would not wet to SN63Pb37 after several attempts and profile
temperature  increments It was found out that it had SAC 305 balls. Has
anyone experienced that SAC does not wet well with eutectic tin lead
solder paste? In another instance balls from SAC and Tin Lead were found
in the same BGA. Apparently solder balls were inadvertently mixed.
        Ramon

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