Post by thread:[EE] Trays for MSL Baking

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

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}> 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 >

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). >

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}

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>

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

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

>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?

--- "Alan B. Pearce" <spam_OUTA.B.PearceTakeThisOuTrl.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

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

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 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 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFGaL4h3bMhDbI9xWQRAoEeAJ0ROxDvSQp65gULpolBGquEi3CBgwCfRk5U E8Rn4VqMoCd8f8p5lxUW7eU= =wZLM -----END PGP SIGNATURE-----

>> 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

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