Ramon,
Lead free reflow in air at higher temperatures will darken components.
These parts were exposed to a 250C peak.
John
At 05:15 AM 6/23/2005, you wrote:
> It looks like it was damaged by excessive heat to the point it
> was darkened.
> Ramon
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Ingemar Hernefjord
>(KC/EMW)
>Sent: Thursday, June 23, 2005 2:30 AM
>To: [log in to unmask]
>Subject: Re: [TN] Moisture sensitivity levels...
>
>
>John,
>1.How did you know for sure that this was caused by moisture?
>
>2.Furthermore, do you have an idea about what amount of moisture
>is needed for such an explosion?
>
>3. If you had several more tantalums on that board or other boards
>from that lot, why just only this one? Why did not the others explode
>too?
>
>Ingemar
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of John Maxwell
>Sent: den 22 juni 2005 21:42
>To: [log in to unmask]
>Subject: Re: [TN] Moisture sensitivity levels...
>
>
>Ingemar,
>I have a lovely photo of a tantalum cap that burst open during lead free
>reflow. Lots of venting of steam also moving adjacent parts from tantalum
>caps that did not rupture. What fun this lead free will be.
>
>John Maxwell
>
>At 12:15 AM 6/22/2005, you wrote:
> >Hi Gaby,
> >
> >we do have 60% too, all mounting area is 50-60% in order to get low ESD
> risk.
> >And still, most reels have no baking. Tantalum epoxy molded, resistors,
> >ceramics,
> >SOTs, QFPs etc are exposed to the humidity in the assembly halls. And
> they are
> >soldered with no problems, as far as I know. Millions of them.
> >
> >Exceptions: superBGAs and very large QFPs which are MS classed by the
> >component
> >maker himself. These are stored in nitrogen cabinets or in plastic bags with
> >dessicators. So, MS classed components are handled with care.
> >
> >You did not tell us what components caused big trouble. Were they MS
> classed ?
> >
> >Inge
> >
> >-----Original Message-----
> >From: Gabriela Bogdan [mailto:[log in to unmask]]
> >Sent: den 21 juni 2005 16:40
> >To: TechNet E-Mail Forum; Ingemar Hernefjord (KC/EMW)
> >Subject: Re: [TN] Moisture sensitivity levels...
> >
> >
> >Inge, try to work in an environment with up to 60% humidity... we are baking
> >and baking again...
> >If we miss we are in big trouble.
> >Gaby
> >----- Original Message -----
> >From: "Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
> >To: <[log in to unmask]>
> >Sent: Tuesday, June 21, 2005 9:53 AM
> >Subject: Re: [TN] Moisture sensitivity levels...
> >
> >
> > > Steve,
> > > how come that you jumped high so sudden? Have you used some kind of
> > > humidity issue filter
> > > all these years...he-he..cheating. There is humidity everywhere. Mother
> > > nature infiltrates
> > > water vapour molecules everywhere she can. We learned that there is
> > > humidity even on inside
> > > of glass feedtrues, water penetrates deeply into kovar packages, there is
> > > water in the solder
> > > paste, every single "plastic" has a small amount of water on inside.
> Water
> > > molecules are
> > > universal and unavoidable. We had a period of humidity hysteria, digged
> > > deeply into the
> > > mystery of water penetration mechanisms by means of proffessors and
> > > doctors, had seminars,
> > > and the learned painted scaring scenarios about all bad things that could
> > > occur due to water in
> > > the material. We spent a lot of money on residue gas analysis and made
> > > lots of MIL STD
> > > tests and so on. The years pass and behold, a miracle: there has been no
> > > catastroph. Some
> > > few reports have been noticed, but the equipments spread all over the
> > > globe seem to work,
> > > and mounting seems to go on rather free from incidents despite there is
> > > water in every
> > > single component. So, I wonder if all anti-humidity countermeasures are
> > > proportional to the
> > > very few failures that occur due to water.
> > >
> > > My thoughts do not necesserarily represent the general opinion here, I'm
> > > just curious about
> > > the mystery of water content and others experience. Is humidity a severe
> > > problem today?
> > > Can anyone give example?
> > >
> > > (I don't include water that penetrates into packages from the surrounding
> > > during field use,
> > > but just point at built-in humidity in parts before and during assembly.)
> > >
> > > Ingemar Hernefjord
> > > Ericsson Microwave Systems
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]]On Behalf Of Stephen Gregory
> > > Sent: den 20 juni 2005 17:26
> > > To: [log in to unmask]
> > > Subject: [TN] Moisture sensitivity levels...
> > >
> > >
> > > Good mornin' all!
> > >
> > > I hope all you Dads out there had a wonderful Fathers Day!
> > >
> > > As I posted about a week or so ago, we're getting our stockroom
> > > personnel to really focus on component moisture sensitivity levels.
> > >
> > > But now I'm starting to get a little confused about how components
> > > are generally classified with their respective MSL ratings.
> > >
> > > I've always thought that it had to do with component body size and
> > > thickness,
> > > but now I'm finding out that it doesn't necessarily.
> > >
> > > My stockroom clerk showed me an IDT SOJ28 that came in sealed with a
> MSL 3
> > > rating that we now have in our dry box because the package was opened.
> > >
> > > We have some Cypress SOJ28's and SOJ24's that are on reels that are
> not in
> > > original packaging, so I called Cypress and asked what the MSL rating is
> > > for the
> > > two part numbers and they are a MSL 1. Cypress gave me a link to the SRAM
> > > Qualification Report that states that.
> > >
> > > Now my stockroom clerk brought me some Vishay tantalum caps that have
> > > a MSL 2a rating label on them, and they are TNTC's. This is THE FIRST
> time
> > > I
> > > have ever seen a MSL label on a tantalum capacitor.
> > >
> > > Are these ratings based on qualification reports? Or can one look at the
> > > size and
> > > thickness of the part to base how you will handle it?
> > >
> > > Kind regards,
> > >
> > > -Steve Gregory-
> > > Senior Process Engineer
> > > LaBarge Incorporated
> > > Tulsa, Oklahoma
> > > (918) 459-2285
> > > (918) 459-2350 FAX
> > > __________________________________________________________________
> > > This message may contain information that is privileged and confidential
> > > to
> > > LaBarge, Inc. It is for use only by the individual or entity named
> above.
> > > If you are not the intended recipient, you may not copy, use or deliver
> > > this message to anyone. In such event, you should destroy the
> message and
> > > kindly notify the sender by reply e-mail.
> > >
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