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'[EE] Trays for MSL Baking'
2007\06\05@220222 by Forrest Christian

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So, I've got a couple components on my new board that have a MSL of 3,
which basically means that I'm going to have to bake the components at
125*C overnight before I can use them in assembly (since I will have a
lot of open stock).

I have acquired a suitable used industrial oven to do this in.  What I
can't find is some sort of designed-for-this-purpose tray to put the
components on to put in the oven.  Before I just go out and grab a
cookie sheet for this purpose, are there special ESD trays for this?

-forrest

2007\06\06@082435 by Carl Denk

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Not terribly conversant on this topic, but aren't ESD trays conductive,
and cookie sheets are steel (could be stainless) which is conductive
(except the coated non-stick variety), therefore would meet the ESD
requirement. Possibly need a ground wire while loading/unloading (wire
with 2 alligator clips). :)

Forrest Christian wrote:
{Quote hidden}

2007\06\06@154535 by Carey Fisher

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Forrest,
What's MSL and why does it matter?
Thanks,
Carey

Forrest Christian wrote:
> So, I've got a couple components on my new board that have a MSL of 3,
> which basically means that I'm going to have to bake the components at
> 125*C overnight before I can use them in assembly (since I will have a
> lot of open stock).
>  

2007\06\06@163155 by Peter van Hoof

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See these sites

en.wikipedia.org/wiki/Moisture_Sensitivity_Level
http://www.jedec.org/download/search/jstd020c.pdf

Basically MSL is moisture sensitivity level 3=168 hours max time
after opening package before it needs to be re-flowed/soldered
If it is not soldered within this time-span it will need a bake before doing so
If this is not done moisture trapped in the device can turn to steam and
damage the device (immediately or over time)

Peter van Hoof


{Original Message removed}

2007\06\06@164112 by Peiserma

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piclist-bounces@mit.edu wrote:
> What's MSL and why does it matter?

Moisture Sensitivity Level. basically certain components can be damaged during reflow if they have absorbed too much moisture

<http://en.wikipedia.org/wiki/Moisture_Sensitivity_Level>

2007\06\07@034554 by Forrest W Christian

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Carey Fisher wrote:

>Forrest,
>What's MSL and why does it matter?
>
Others have answered with what it is... basically a rating which has to
do with absorbtion of moisture from the air which vaporizes during
soldering cracking the package (or doing other damage).

What is scary is how many packages are at MSL 3 or above.  What is
biting me are the regulators I want to use which are in a TO-263 package
which is basically a surface mount version of the TO-220.  Once I open
the package I have to use all of them within 7 days or I have to bake
them at 125*C for at least 8 hours to dry them out before I do use them.

-forrest

2007\06\07@113437 by Bob Barr

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On Thu, 07 Jun 2007 01:47:22 -0600, Forrest W Christian wrote:

>Carey Fisher wrote:
>
>>Forrest,
>>What's MSL and why does it matter?
>>
>Others have answered with what it is... basically a rating which has to
>do with absorbtion of moisture from the air which vaporizes during
>soldering cracking the package (or doing other damage).
>
>What is scary is how many packages are at MSL 3 or above.  What is
>biting me are the regulators I want to use which are in a TO-263 package
>which is basically a surface mount version of the TO-220.  Once I open
>the package I have to use all of them within 7 days or I have to bake
>them at 125*C for at least 8 hours to dry them out before I do use them.
>

Something doesn't sound right about that. Aren't there provisions in
MSL handling procedures that allow for resealling the devices that
won't be used over the next 7 days?

You may be able to avoid some bake-outs by doing this. I'll see if I
can find a link on the topic.


Regards, Bob

2007\06\07@115243 by Alan B. Pearce

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>Something doesn't sound right about that. Aren't there provisions
>in MSL handling procedures that allow for resealling the devices
>that won't be used over the next 7 days?

Umm, yeah, if you put dry dessicant in the bag and heat seal it ...

Not too many hobbyists would have a heat sealer handy, would they?

2007\06\07@123044 by Bob Blick

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--- "Alan B. Pearce" <spam_OUTA.B.PearceTakeThisOuTspamrl.ac.uk> wrote:
> Umm, yeah, if you put dry dessicant in the bag and
> heat seal it ...
>
> Not too many hobbyists would have a heat sealer
> handy, would they?

I've got a hot glue gun right here, that should be
fine for that purpose.

Cheerful regards,

Bob

2007\06\07@161427 by Robert Rolf

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Alan B. Pearce wrote:

>>Something doesn't sound right about that. Aren't there provisions
>>in MSL handling procedures that allow for resealling the devices
>>that won't be used over the next 7 days?
>
>
> Umm, yeah, if you put dry dessicant in the bag and heat seal it ...
>
> Not too many hobbyists would have a heat sealer handy, would they?

It's called a 'metal ruler and soldering iron'.
You draw the iron tip quickly across the plastic baggy
(at a low angle) while holding the end closed with the metal ruler. You get a good seal
after a bit of practice to get the speed right.
Too fast you don't seal. Too slow and you melt through.
I do it all the time and it gives a nice hermetic seal.

You can also fold the open end over several times and tape fully (using packing
tape or 'vapor barrier' tape used in home construction.

Robert

2007\06\07@222601 by Peter Todd

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On Thu, Jun 07, 2007 at 04:52:39PM +0100, Alan B. Pearce wrote:
> >Something doesn't sound right about that. Aren't there provisions
> >in MSL handling procedures that allow for resealling the devices
> >that won't be used over the next 7 days?
>
> Umm, yeah, if you put dry dessicant in the bag and heat seal it ...
>
> Not too many hobbyists would have a heat sealer handy, would they?

Surely a zip-lock bag would be good enough if you put dessicant in it?

- --
http://petertodd.ca
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2007\06\07@231241 by William Chops Westfield

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>> Not too many hobbyists would have a heat sealer
>> handy, would they?
>>
Not too many hobbyists wave/reflow solder, and I don't
think it's expected to be a big issue for hand soldering.

I suspect MSL3 "bake for 8 hours" is becoming like "wash
under running water for 15 minutes"; a standard instruction
applied to almost everything whether it makes sense or not.

 :-(
BillW

2007\06\07@232429 by Carey Fisher
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Forrest W Christian wrote:
> Carey Fisher wrote:
>
>  
>> Forrest,
>> What's MSL and why does it matter?
>>
>>    
> Others have answered with what it is... basically a rating which has to
> do with absorbtion of moisture from the air which vaporizes during
> soldering cracking the package (or doing other damage).
>
> What is scary is how many packages are at MSL 3 or above.  What is
> biting me are the regulators I want to use which are in a TO-263 package
> which is basically a surface mount version of the TO-220.  Once I open
> the package I have to use all of them within 7 days or I have to bake
> them at 125*C for at least 8 hours to dry them out before I do use them.
>
> -forrest
>  

Doesn't it matter what the relative humidity is where the parts are kept
after opening the package?
Carey


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