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October 1998

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From:
Russ Winslow <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 7 Oct 1998 21:03:46 -0700
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Good Question.
According to MIL-PRF-38535 the solderability test in
Mil-Std-883 method 2003 can be considered "non-destructive" if the component
does not have a glass seal.  This implies that components which meet this
specification should withstand a 250 C dunk in solder for 5 seconds without
preheat.  I'm not sure this is a real good idea.  We always consider a
solderability test to be a destructive test.  Most ceramic (hermetic)
components can withstand many sudden exposures to 250 C only if you preheat
above100 C (Minimum body temperature).  Our experience suggests that 5 or
more exposures (with preheat) will not significantly impair most ceramic
devices.  Of course ceramics are easier to monitor than plastics because the
ceramic, metal, and glass
properties are not adversely affected at this temperature and the
typical failure mode is hermeticity failure which is easy to monitor
non-destructively.

Plastic components are a different story.  Different
components can behave very differently.  The average plastic component
(pre-BGA) can withstand some incredible pain however the damage created can
easily go undetected.  Without using an acoustic microscope you cannot see
the lead fingers seperating from the molding compound and entrapping
contaminants which could find their way to the aluminum bond pads with
enough time.  The molding compound can shear a wire bond but leave the die
functional (for a while).  Together with some manufacturers who may tell
you that one reflow at 230 C for 60 seconds is all they will guarantee.

One specification to check out is J-STD-020 Moisture reflow sensitivity
classification...
It requires that the components survive three reflows at 220 C for 10
seconds.  Unfortunately the vapor phase version of the test is optional.
The preconditioning test JESD22-A113 is essentially the same.

Another one is JESD22-B106-A  Resistance to soldering temperature for
through-hole mounted devices.  This one is a dunk in molten solder at 260 C
for 10 seconds with no preheat.
We have seen more than one customer requirement to test PQFPs in molten
solder at 260 C for 30 seconds.  Problem is the fine pitch ones come out
leadless.

I believe that most microelectronics manufacturers will soon begin assuming
that peak temperature exposures in board assembly will decrease from 260 C
(good old wavesolder days) to the 220 C surface mount (here comes BGA) days.

Yes, I do think you have a good question there.

Good Luck

Russ


-----Original Message-----
From: glenn pelkey <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Wednesday, October 07, 1998 1:25 PM
Subject: [TN] Assy: Max Soldering Temp/Time spec.


>Hello all,
>
>     Is there a specification to address the soldering maximum
>temperature and time for an active leaded component?  The assembly
>technique would be either hand soldering or through-hole wave soldering.
>I've seen temperatures from 245 to 315 C and times from 5 to 15 seconds
>listed by others.  So far, the only spec. I found with reference to
>temperature and time is Mil-Std-883, Method 2003.  However, it only
>addresses solderability of the leads, not functionality.
>
>Thanks for your input.
>
>Glenn Pelkey
>[log in to unmask]
>[log in to unmask]
>Maxtek Components Corp.

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