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April 2015

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From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Tue, 7 Apr 2015 14:25:45 +0000
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Yes. You can see a good example of what happens when attempting to solder heavily oxidized solder spheres in IPC-7095A Figure 9-11. This can occur from improper long-term storage of BGAs, and in fact is very common. Not too many people understand just WHY this happens. It can be from too many reflow cycles, but quite often is just from using older BGAs, especially those with SN100 or SAC305 balls, that have either been baked or stored without benefit of a good nitrogen filled sealed drypak or in a nitrogen cabinet. SAC305 balls quickly oxidize when exposed to air for long periods of time.
Odin

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Tuesday, April 07, 2015 9:08 AM
To: [log in to unmask]
Subject: Re: [TN] 5 year old BGAs

Hi Pete,

There is no playing on BGA balls but ‎their surface will oxidize over time. Baking will speed it up. 

You can easily calculate for how long and at what temperature to "age" the package to mimic 5 years of storage and then try to solder few of those to see what to expect in 5 years.

Regards,

Vladimir

SENTEC

Sent from my BlackBerry 10 smartphone on the Rogers network.
  Original Message
From: Peter G. Houwen
Sent: Tuesday, April 7, 2015 09:54
To: [log in to unmask]
Reply To: TechNet E-Mail Forum
Subject: [TN] 5 year old BGAs

We have an FPGA that may not be available to us soon. One of the options available to us to avoid a redesign is to buy 5 years' supply of the BGA.

I'm being asked to analyze the risk factors (and we need an answer today of course)

We can easily bake parts for moisture, but what about plating degradation on the balls? Any other problems I might expect?

I assume that even with baking we should expect some yield reduction, but I can't begin to guess how much.

Thanks,

Pete

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