Especially if they're plastic-bodied BGA's, YES, unused components from a
package should be resealed with desiccant. The problem is not so much
oxidisation but atmospheric moisture absorbtion. This can happen within a
matter of hours depending on the RH of the atmosphere they're exposed to
and their sensitivity to moisture absorbtion (see reply to me earlier from
Francois).

If too much moisture is absorbed and not baked out again, the soldering
temperatures cause the moisture to vapourise. This leads to internal
weakening or physical damage to the insides of the devices, and even
delamination or explosion of the casing - a phenomenon known as
'popcorning'. JEDEC J-STD-033 tells you what you need to know in this
respect and is downloadable free from the Net.

Pete Duncan




                    Rick Howieson
                    <RHowieson@DELTAGRO        To:     [log in to unmask]
                    UPINC.COM>                 cc:     (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
                    Sent by: TechNet           Subject:     [TN] BGA
                    <[log in to unmask]>


                    05/24/01 10:35 PM
                    Please respond to
                    "TechNet E-Mail
                    Forum."; Please
                    respond to Rick
                    Howieson






Need information on protecting BGA's not loaded. Should BGA's from a
package
not used be sealed for the next run? If so, is this because the balls
become
oxidized or ...?
Thanks,
Rick Howieson
Delta Group Electronics, Inc.

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