Baking ICs?

[Rewar]

Hello

I just got some parts from Digikey and the 'moisture barrier bag' with TOIC
srams in it has the following warning;

Notice! Parts are subject to moisture absorption.
Take care to prevent damage when vapor or ir
soldering. Bake prior to soldering to reduce
the chance for damage.

It has been a couple of years since I last bought any TOIC srams but I do know
that there was no such warning then. Nor is there a warning for the DIP ICs I
got. Can someone tell me the significance of the warning? I will be
(painstakenly) hand soldering them. Thanks.

Robert

 

[Spehro Pefhany]

Hello

I just got some parts from Digikey and the 'moisture barrier bag' with TOIC
srams in it has the following warning;

Notice! Parts are subject to moisture absorption.
Take care to prevent damage when vapor or ir
soldering. Bake prior to soldering to reduce
the chance for damage.

It has been a couple of years since I last bought any TOIC srams but I do know
that there was no such warning then. Nor is there a warning for the DIP ICs I
got. Can someone tell me the significance of the warning? I will be
(painstakenly) hand soldering them. Thanks.

Hand soldering isn't a problem. Somtimes the really thin packages
absorb enough water that they are damaged when subjected to IR reflow.
Many SMT ICS have this warning (and are packaged with dessicant). You
can buy special dessicating cabinets to store them in once the package
is broken. SOIC and PLCC packages don't seem to be a problem.

Best regards,
Spehro Pefhany

 

[Mac]

Hello

I just got some parts from Digikey and the 'moisture barrier bag' with TOIC
srams in it has the following warning;

Notice! Parts are subject to moisture absorption.
Take care to prevent damage when vapor or ir
soldering. Bake prior to soldering to reduce
the chance for damage.

It has been a couple of years since I last bought any TOIC srams but I do know
that there was no such warning then. Nor is there a warning for the DIP ICs I
got. Can someone tell me the significance of the warning? I will be
(painstakenly) hand soldering them. Thanks.

Robert

It's the new Big Thing. First it was static, now it is moisture. The idea
(as it was explained to me) is that moisture can cause fracturing of the
die when the moisture is rapidly converted to steam. I think it is a
bigger concern for smaller dies, but digikey just labels everything. (You
know, like the static warnings on resistors or connectors.)

If you get parts with a real manufacturer's warning label on it, and
detailed instructions for re-dessicating the part, that is probably a real
warning based on some kind of analysis or experimentation. These parts
should come packaged with a dessicant.

Besides, the warning you quote above doesn't seem to mention hand
soldering, so maybe you are OK.

Mac

 

[CBarn24050]

Hi, it's only a problem if you are reflow soldering the board.

 

[Rewar]

Thanks all for the responses, which were both good news and bad news.

The good news is that the warning is probably irrelevant to handsoldering.

The bad news is that I now have no excuse for not starting the tedious process
of soldering these little monsters into place.

Thanks again

Robert

 

[Don Lancaster]

Hello

I just got some parts from Digikey and the 'moisture barrier bag' with TOIC
srams in it has the following warning;

Notice! Parts are subject to moisture absorption.
Take care to prevent damage when vapor or ir
soldering. Bake prior to soldering to reduce
the chance for damage.

It has been a couple of years since I last bought any TOIC srams but I do know
that there was no such warning then. Nor is there a warning for the DIP ICs I
got. Can someone tell me the significance of the warning? I will be
(painstakenly) hand soldering them. Thanks.

Robert

Baking is definitely preferred to deep frying.

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: [email protected] fax 847-574-1462

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Winfield Hill]

Spehro Pefhany <Spehro Pefhany wrote...

Hand soldering isn't a problem. Somtimes the really thin packages
absorb enough water that they are damaged when subjected to IR reflow.
Many SMT ICS have this warning (and are packaged with dessicant). You
can buy special dessicating cabinets to store them in once the package
is broken. SOIC and PLCC packages don't seem to be a problem.

Which types of SMT packages have this problem?

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Winfield Hill]

Rewar wrote...

I just got some parts from Digikey and the 'moisture barrier bag'
with TOIC srams in it has the following warning;

TOIC srams?

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Ian Stirling]

Rewar wrote...

TOIC srams?

Maybe TSOIC?

 

[Spehro Pefhany]

Which types of SMT packages have this problem?

Here's a detailed application note from National, which specifies what
packages have what senstivity. The table on the last page (6),
specifies which packages need what handling for which of two reflow
temperatures. Note that MSL 1 means that no special handling is
required for <= 30°C & 85% humidity, and thus are not dry-packed at
all, and MSL 2 allows them to be open for a whole year. The worst is
MSL 4- they can only safely stay open for 72 hours on the production
floor.

Looks like PQFP-44 is the worst, followed by FBGA (49..100), PLCC-52
and TO-220 SMT, and TO-263 (a bit of a surprise with those last two).

http://www.national.com/quality/files/Dry_Pack_Handling_with_MSL_Rating.pdf

Best regards,
Spehro Pefhany

 

[Rewar]

Maybe TSOIC?

Yup, TSOIC

Robert

 

[Roger Gt]

X-No-Archive: yes

"Spehro Pefhany >" <Spehro Pefhany
message

Here's a detailed application note from National, which specifies what
packages have what sensitivity. The table on the last page (6),
specifies which packages need what handling for which of two reflow
temperatures. Note that MSL 1 means that no special handling is
required for <= 30°C & 85% humidity, and thus are not dry-packed at
all, and MSL 2 allows them to be open for a whole year. The worst is
MSL 4- they can only safely stay open for 72 hours on the production
floor.

Looks like PQFP-44 is the worst, followed by FBGA (49..100), PLCC-52
and TO-220 SMT, and TO-263 (a bit of a surprise with those last two).

http://www.national.com/quality/files/Dry_Pack_Handling_with_MSL_Rating.pdf

Don't you always prebake at 90 to 100 degrees C
before IR soldering? I thought this was needed
to dry the board and all components before
subjecting it to the soldering temperatures!

 

[Mike]

Spehro Pefhany <Spehro Pefhany wrote...

Which types of SMT packages have this problem?

Quite a few of them may have; the JEDEC specifications was recently updated
(or will be soon). The previous specification offers two reflow temperature
classifications of 220C and 235C. The new specification adds a third
classification at 260C, due to the higher temperatures needed for some
lead-free mounting applications.

The relevant JEDEC specs are: USA Moisture Sensitivity Classification
(J-STD-020A) and Handling (J-STD-033). www.jedec.org

The above information is from an Amkor application note:

http://www.amkor.com/products/notes_papers/MBIRD_Article0700.pdf

There's also a technical article regarding delamination failures:

http://www.amkor.com/services/Thermal/Papers/ectc_98_RevB.PDF

-- Mike --

 

[Spehro Pefhany]

Don't you always prebake at 90 to 100 degrees C
before IR soldering? I thought this was needed
to dry the board and all components before
subjecting it to the soldering temperatures!

No, that's just preheating and is standard procedure for both SMT and
wave soldering process. You just bring the parts momentarily up to
100°C before the soldering process. The *baking* takes hours or even
days and is required to get moisture out of the non-hermetic plastic
packages.

BTW, a similar procedure is required before injection molding plastic
pellets (for most resins).

Best regards,
Spehro Pefhany