Vit,
I will use Doug Pauls stock answer - it all depends.
If your product has aluminum electrolytic capacitors, then you will be probably be limited to the life time guaranteed by the supplier. Then ask yourself are there other components like this.
Next, maybe not next, but at least on your list, are there any 100% tin finishes? I know they say tin whiskers are spontaneous and not time dependent, but still... I would look at a representative number of products.
Was the product not only stored at the right temperature and humidity, but was it also stored away from dust, oil, silicones, salt spray, excessive vibration, sunlight, sulfide containing paper and cardboard? The latter might affect certain switch surfaces, etc. Sunlight will embrittle plastics. Use your imagination for the others.
Another item, are there any components that have stored programs that might be corrupted from stray alpha particles from the radioactive impurities in lead206 and from cosmic radiation? I know the former can happen, but it depends on how close the chip is to the lead and where the lead came from. And I must say I really don't know how much, if any, the latter is a real problem. Certainly if there is any danger from this, sitting on a shelf for ten years won't help.
Since the parts are already soldered then the growth of tin oxides should not be an issue, unless there is a soldering step to make it part of a larger whole. The intermetallic layers will be growing, but at room temperature, I can't see that this should be a big issue.
If you cover all these bases, I can't see why ten years shouldn't be OK. Guys, am I off base here? Some of the fellows from the military depots should have tons of info on this topic.
regards,
Bev Christian
Research in Motion
-----Original Message-----
From: Sklenar Vit (RBAU-EB/MGE4) [mailto:[log in to unmask]]
Sent: March 25, 2003 4:28 PM
To: [log in to unmask]
Subject: [TN] shelf life of spare parts - electronic units
Hi Techneters,
Is somebody in this forum who can help us with advise? IPC advised there is
no standard covering this issue but some companies may have an internal
guidelines...???
When the electronic assembly product is made as a spare part how
many years it
can be on the shelf ( normal conditions 20 degsC 60-70 % RH) before
it
should be disposed and not used - sold to customer... ?
Thank you for help.
Best Regards to all
Vit Sklenar
T: +613 9541 7734
F: +613 9541 3909
Robert Bosch Australia P/L
Cnr Centre & McNaughton Rd
Clayton VIC 3168
work e-mail:[log in to unmask]
home email: [log in to unmask]
-----Original Message-----
From: Arbour, Michel [mailto:[log in to unmask]]
Sent: Wednesday, 26 March 2003 8:10 AM
To: [log in to unmask]
Subject: Re: [TN] FW: [TN] TCE above Tg for Dupont CB100 silver resin
I received the TMA graph from Dupont from 25-200C. Draw two straight lines
below and over Tg (115).
The difference between the graph and the lines is negligible .
CTE 25-115C : 27ppm/C
CTE 115-200C: 47.2ppm/C
Regards
> -----Original Message-----
> From: Mcmaster, Michael [SMTP:[log in to unmask]]
> Sent: 25 mars, 2003 13:22
> To: [log in to unmask]
> Subject: Re: [TN] FW: [TN] TCE above Tg for Dupont CB100 silver resin
>
> Substates typically have anisotropic CTEs in X/Y and Z because of the
> effect of the glass reinforcement limiting expansion in the X/Y direction.
> CB-100 is a silver filled epoxy. Unless there is something about the size
> and shape of the filler and application method that would provide an
> orientation to the filler (I'm unaware of any of this being done with this
> material), CB-100 should have isotropic CTE values.
>
>
> Mike McMaster
> RF Product Engineer
> Merix Corporation
> 503-992-4263
>
>
>
> ----------
> From: Yuan Li[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;Yuan Li
> Sent: Tuesday, March 25, 2003 10:02 AM
> To: [log in to unmask]
> Subject: Re: [TN] FW: [TN] TCE above Tg for Dupont CB100 silver
> resin
>
> Is it the CTE on Z-direction?
> The CTEs on X- and Y- directions above Tg are lower for BT substrates.
>
>
>
> -----Original Message-----
> From: peter blokhuis [ <mailto:[log in to unmask]>]
> Sent: Tuesday, March 25, 2003 6:07 AM
> To: [log in to unmask]
> Subject: Re: [TN] FW: [TN] TCE above Tg for Dupont CB100 silver resin
>
> Methode Electronics <http://www.methode.com/mdc/via.pdf>
> has a similar material (their 1210) with a Tg of
> 190ppm/C above their Tg of 120C. Perhaps this will be
> close enough for your needs.
> Peter Blokhuis
>
>
> --- joyce <[log in to unmask]> wrote:
> > if it is standard epoxy filled with silver, my guess
> > is 3x TCE above Tg.
> > With absent of data and not going to do any test
> > (which I think you
> > really should do the test... rather than question it
> > endlessly, why not
> > just pay few $ run a TMA?), I would design per 3x
> > TCE above Tg, provide
> > you cure it properly. On the other hand, why Dupont
> > not provide above
> > Tg data? very strange...
> >
> > my 2 cents.
> >
> > jk
> >
> > -----Original Message-----
> > From: TechNet [ <mailto:[log in to unmask]>] On Behalf Of
> > Mcmaster, Michael
> > Sent: Monday, March 24, 2003 5:41 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] FW: [TN] TCE above Tg for Dupont
> > CB100 silver resin
> >
> >
> >
> > I'm going to have to disagree with Guy on this.
> > There's nothing that
> > says CTE above Tg has to be non-linear. Nor is
> > there anything that says
> > it has to be linear, especially when working with
> > systems like today's
> > high performance epoxy systems.
> >
> > There are multiple ways to define, measure, and
> > determine Tg, but it is
> > generally regarded as the temperature below which
> > free rotations cease
> > because of intramolecular energy barriers. In other
> > words, the material
> > acts as a glass.
> >
> > Above Tg the polymer achieves what is known as
> > segmental mobility. The
> > reason for this is that as you heat the material up
> > it expands (the
> > CTE). This expansion results in an increase in free
> > volume. Below, Tg,
> > the free volume is too small to allow segmental
> > mobility, whereas above
> > Tg, the free volume is large enough.
> >
> > The Tg the shows up as a discontinuity in the
> > specific volume vs
> > temperature curve. For amorphous polymers,
> > especially something like a
> > cross-linked epoxy, the transition is not clean.
> > Difference in cross
> > link density, segment length, initial free volume
> > and other factors mean
> > that different sections of the material achieve the
> > necessary free
> > volume for segmental mobility at different
> > temperatures. As a result,
> > the glass transition is usually not abrupt (like
> > say, the melting of
> > water, another transition). So while the Tg is
> > reported as a single
> > temperature, that's rarely true. The temperature is
> > usually arrived at
> > by extrapolating the specific volume vs temperature
> > curves above and
> > below Tg. The reported Tg is the intersection of
> > the two lines, even
> > though the transition itself started below and
> > continued above this
> > temperature.
> >
> > For CTE above Tg to be restricted to "non-linear" or
> > "linear" is
> > unfounded. I've seen plenty of TMA scans that
> > exhibit linear behavior
> > for at least some section above the Tg. I've also
> > seen materials that
> > exhibit very non-linear behavior. Much of this has
> > to do with the
> > highly variable structures and compositions of
> > polymeric materials. You
> > have materials that are difunctional,
> > tetrafunctional, mulitifunctional
> > and then the co-polymer blends that tend to exhibit
> > multiple transitions
> > to the point where you can't find two lines from a
> > TMA scan to
> > extrapolate to an intersection. In some cases, it's
> > nearly impossible
> > to get a good Tg determination from TMA alone and
> > alternative methods
> > such as DSC and DMA must be used. But these look at
> > properties other
> > than volume to determine the transition and don't
> > necessarily give the
> > same result.
> >
> > And I'm guessing that you don't really care whether
> > it's truly linear or
> > not as along as it's a reasonable approximation of
> > the CTE in the
> > temperature range of interest. In all likelihood
> > you want to know how
> > the material is going to perform during reflow
> > soldering (from below to
> > above Tg). And maybe the properties during the
> > operational life (likely
> > below Tg). So you need to know the Tg, preferably
> > measured with TMA
> > since that is how CTE is measured also. You need to
> > know the
> > temperature range for the CTE measurements. You at
> > least want the value
> > above and below Tg. Reporting and using a CTE value
> > that is the
> > combination of the values above and below Tg is not
> > of any practical
> > value. The material exhibits this particular
> > behavior only at one very
> > specific temperature during the transition phase.
> > It's akin to a
> > stopped watch being right twice per day.
> >
> > Like you, I've had no luck determining the CTE of
> > CB-100 above Tg.
> >
> > Mike McMaster
> > RF Product Engineer
> > Merix Corporation
> > 503-992-4263
> >
> >
> >
> > ----------
> > From: Arbour,
> > Michel[SMTP:[log in to unmask]]
> > Reply To: TechNet E-Mail Forum.;Arbour, Michel
> > Sent: Monday, March 24, 2003 6:10 AM
> > To: [log in to unmask]
> > Subject: [TN] FW: [TN] TCE above Tg for
> > Dupont CB100 silver resin
> >
> >
> > > OK,
> > > So the values for ZTCE > Tg given in the material
> > specs or various
> > > articles
> > > are linear approximation of the behaviour of ZTCE
> > >Tg . Right ??
> > >
> > > And the Zaxis expansion% (50 to 288C) is the
> > "real" value ?
> > >
> > > Ref. : circuitree magazine Feb. 2001: High
> > reliability/Low CTE epoxy
> > > technology,
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Guy Ramsey [SMTP:[log in to unmask]]
> > > > Sent: 21 mars, 2003 16:01
> > > > To: 'TechNet E-Mail Forum.'; 'Arbour, Michel'
> > > > Subject: RE: [TN] TCE above Tg for Dupont
> > CB100 silver resin
> > > >
> > > > TCE above Tg is non-linear. What you're asking
> > for is like asking
> > for
> > > > the distortion characteristics of a amp is after
> > clipping.
> > > >
> > > > > -----Original Message-----
> > > > > From: TechNet [ <mailto:[log in to unmask]>] On
> > Behalf Of Arbour, Michel
> >
> > > > > Sent: Friday, March 21, 2003 2:52 PM
> > > > > To: [log in to unmask]
> > > > > Subject: [TN] TCE above Tg for Dupont CB100
> > silver resin
> > > > >
> > > > >
> > > > > Hello Techies,
> > > > > By any chance, would you know what is
> > the TCE > Tg
> > > > > for Dupont CB100 silver resin ??
> > > > >
> > > > > Can't get that info from DuPont's
> > Micro-Circuit
> > > > > Materials group in the U.S. . They have not
> > measured that
> > > > > characteristic they said...
> > >
> > >
> > ---------------------------------------------------
> >
> === message truncated ===
>
>
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