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'[PICLIST] [OT] Moisture Absorbing Parts?'
2001\09\25@101649 by Howard McGinnis

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I just received samples of Burr-Brown's ISO-124 low cost isolation
amplifier from TI and found an unusual label attached to the normal static bag:

NOTICE!! PARTS ARE SUBJECT TO MOISTURE ABSORBTION. TAKE CARE TO PREVENT
DAMAGE WHEN VAPOR OR IR SOLDERING. BAKE PRIOR TO SOLDERING TO REDUCE THE
CHANCE OF DAMAGE.

These are somewhat normal looking DIP packages, other than the fact that
they don't have a full complement of legs.

What's the deal? Is it the manufacturing process?

Howard

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2001\09\25@112416 by Spehro Pefhany

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At 10:15 AM 9/25/01 -0400, you wrote:
>I just received samples of Burr-Brown's ISO-124 low cost isolation
>amplifier from TI and found an unusual label attached to the normal static
bag:
>
>NOTICE!! PARTS ARE SUBJECT TO MOISTURE ABSORBTION. TAKE CARE TO PREVENT
>DAMAGE WHEN VAPOR OR IR SOLDERING. BAKE PRIOR TO SOLDERING TO REDUCE THE
>CHANCE OF DAMAGE.
>
>These are somewhat normal looking DIP packages, other than the fact that
>they don't have a full complement of legs.
>
>What's the deal? Is it the manufacturing process?

This has been a standard warning on all SMT packages subjected to IR
soldering for some time. You may have noticed dessicant and moisture-sealed
packages. Probably they just mark all the bags that way. I wouldn't worry
too much about it for normal soldering of through-hole parts under normal
conditions. The typical problem is that moisture migrates into an plastic
SMT package (they are NOT hermetic), and when IR soldering is performed
the resulting steam cracks the package or pops a chunk out of it.

Best regards,
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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2001\09\25@112631 by Kathy Quinlan

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Hi Howard,

Ok the label is real, it is not a left over April fools day joke.

I take it the parts are surface mount ?

With surface mount components when soldering the following happens:
# The temperature is high for a fair period of time
# The temperature is relatively even over the entire chip
# The temperature level is raised fairly rapidly

Any moisture that has seeped into the bond between the top and bottom half
of the component will rapidly expand (it is steam now)as the exit (around
the leads / legs) is not big, the pressure can cause the component to loose
its top, and or break the wire bonds off either the die or the legs (or
both).

This problem only occurs in soldering techniques where individual legs are
not heated i.e. where the device / legs are heated as a whole. If a device
is left in the open and mass heating techniques are to be used, then the
device needs to be baked according to the data from the manufacturer to
slowly dispel any moisture.

Hope this helps,

Regards,

Kat.

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{Original Message removed}

2001\09\25@122026 by mike

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On Tue, 25 Sep 2001 10:15:05 -0400, you wrote:

>I just received samples of Burr-Brown's ISO-124 low cost isolation
>amplifier from TI and found an unusual label attached to the normal static bag:
>
>NOTICE!! PARTS ARE SUBJECT TO MOISTURE ABSORBTION. TAKE CARE TO PREVENT
>DAMAGE WHEN VAPOR OR IR SOLDERING. BAKE PRIOR TO SOLDERING TO REDUCE THE
>CHANCE OF DAMAGE.
>
>These are somewhat normal looking DIP packages, other than the fact that
>they don't have a full complement of legs.
>
>What's the deal? Is it the manufacturing process?
>
>Howard
This is a standard warning for surface mount parts - moisture
absorbtion by the package can cause cracking when subjected to the
thermal shock of soldering. Maybe the iso amp has characteristics that
make it more susceptible - perhaps a bigger die which is more
susceptible to stresses from the package.
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2001\09\25@124115 by David VanHorn

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At 10:15 AM 9/25/01 -0400, Howard McGinnis wrote:
>I just received samples of Burr-Brown's ISO-124 low cost isolation
>amplifier from TI and found an unusual label attached to the normal static
>bag:
>
>NOTICE!! PARTS ARE SUBJECT TO MOISTURE ABSORBTION. TAKE CARE TO PREVENT
>DAMAGE WHEN VAPOR OR IR SOLDERING. BAKE PRIOR TO SOLDERING TO REDUCE THE
>CHANCE OF DAMAGE.
>
>These are somewhat normal looking DIP packages, other than the fact that
>they don't have a full complement of legs.
>
>What's the deal? Is it the manufacturing process?

When parts absorb moisture, then get heated above 212F, they can crack, or
explode.
The pre-heat allows the moisture to evaporate and escape slowly, and not
damage the device.

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