Ramon,
Normally the FA result is based on "need to know" basis regarding all
the party direct impacted. Unless it is common problem affect a
multiple party. ME normally is not on the distribution list of "root
cause" except the personnel directly involved. However, the ME will be
on the distribution list for ECO (engineering change order) or recall
notice if it is affect in stock item. Field failure with lot related
issue will not put current MFG on the distribution list. I am sure each
company has different rules. Small company normally distributed to
everybody.... ;-).
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of David Douthit
>Sent: Wednesday, September 10, 2003 1:56 PM
>To: [log in to unmask]
>Subject: Re: [TN] Silicone conformal coating
>
>
>Ramon,
>
>The answer is yes to all 3 with a caveat. Labs will report to
>whom ever is the "responsible" party. What happens to the
>information after that is out of their control. There also
>tends to be a lack of "feed back" from customer support and
>field engineers to the "MEs".
>
>David A. Douthit
>Manager
>LoCan LLC
>
>"Dehoyos, Ramon" wrote:
>
>> One more thought and I am going to shut up. I am for super
>> clean boards, and perfect coating please do not
>misunderstand me but,
>> many boards are digital circuit type require only 0.6 volts signals
>> which is the diode turn on voltage. Could that be a reason
>why not so
>> many problems exist? Or is it because dendrites take so
>long to form
>> that by that time the boards are absolete? Or is it because labs do
>> not give MEs feed back about such problems?
>> Regards,
>> Ramon
>>
>> > -----Original Message-----
>> > From: David Douthit [SMTP:[log in to unmask]]
>> > Sent: Tuesday, September 09, 2003 11:59 PM
>> > To: Dehoyos, Ramon
>> > Subject: Re: [TN] Silicone conformal coating
>> >
>> > Ramon,
>> >
>> > Dendrite growth is a type of corrosion/metal reduction. As such
>> > there is very little need for "power". Corrosion is a form of
>> > ionized metal migration where moisture combines with
>> > contamination/dissimilar metals and creates its
>> > own voltage cells.
>> >
>> > Dendrite formation evolves pico/micro amps of current flow. The
>> > resulting dendrites are microscopic and will vaporize with just a
>> > few microamps of current. When they are discovered it's usually
>> > after several dozen dendrites have formed
>> > and vaporized
>> > in the same location. The most notable situation is when
>high impedence
>> > very
>> > slow logic lines are involved
>> > (such as reset or interrupt lines). An unknown reset or
>interrupt is
>> > generated
>> > and cannot be duplicated.
>> > After numerous attempts and repeated resets/interrupts
>it's time to get
>> > the SEM
>> > or high power (200+) microscope out
>> > and start looking. Sometimes all you find is residue
>vaporized metal mixed
>> > with
>> > carbon from damaged laminates.
>> > If you are lucky you may find partially formed dendritic
>paths that have
>> > not
>> > reached the anode path.
>> >
>> > In the case of BGA's this is very, very expensive and
>extraordinary
>> > processes are implimented (rigrous cleaning programs)
>> > to prevent these problems. These issues are of major
>concern to the US
>> > military
>> > because COTS components and circuitry are designed for
>> > speed and size reduction and not durability or longevity.
>Depending on the
>> > end
>> > use environment it can take 10 or more years for dendrites to form.
>> >
>> > You are correct that it "takes a certain amount of power" but the
>> > amount is very low!
>> >
>> > David A. Douthit
>> > Manager
>> > LoCan LLC
>> >
>> >
>> > "Dehoyos, Ramon" wrote:
>> >
>> > >
>> > > Hello David:
>> > > My degree is in electrical engineering so I understand
>> > > something about currents and voltages. Besides voltage you need
>> > > current. In my oppinion you need cetain amount of power to start
>> > > the dendrite
>> > formation.
>> > > You can hold with your hands the output of a power
>supply that can
>> > produce
>> > > hundreds of amps and low voltage or the output of a high voltage
>> > > and
>> > very
>> > > low current ( in the pico amps ) power source and not be hurt by
>> > > it but
>> > you
>> > > can not hold a power source that can produce 480 volts and a few
>> > > milli
>> > amps
>> > > because it can kill you ( one of my neighbors could hold a 240
>> > > volt
>> > outlet
>> > > bare wire that is why I chose 480 V ) I have seen so
>many boards
>> > > that
>> > are
>> > > not cleaned properly. In some cases with hydrolyzed flux on some
>> > components
>> > > due to the cleaning agent being to weak or the flux not being
>> > > cleaned withing the hour or other reasons. . Specially
>PGA and BGA
>> > > type of
>> > componets
>> > > are extra difficult to clean. Also conformal coating the joint
>> > > of the previous parts is not easy to accomplish. Yes we spend a
>> > > lot of effort
>> > in
>> > > cleaning our boards at the present job, and try our best to
>> > > conformal
>> > coat
>> > > but other than dipping the boards in CC as we used to do in a
>> > > previous
>> > life
>> > > is nearly imposible to coat every solder joint. Traces could be
>> > > solder masked and be taken cared of them that way, but
>not solder
>> > > joints. I am speaking from experiences and not from lab
>tests that I have made.
>> > > My one and a half cent
>> > > Regards,
>> > > Ramon
>> > >
>> > >
>> > > > -----Original Message-----
>> > > > From: David Douthit [SMTP:[log in to unmask]]
>> > > > Sent: Tuesday, September 09, 2003 1:37 PM
>> > > > To: TechNet E-Mail Forum.; Dehoyos, Ramon
>> > > > Subject: Re: [TN] Silicone conformal coating
>> > > >
>> > > > Ramon,
>> > > >
>> > > > That is a very poor conclusion! Experiments done by IBM in the
>> > > > 70's showed that dendrites would form with as little as .5 VDC
>> > > > bias. Further, electrolysis of water can occur with as
>little as
>> > > > 2 VDC
>> > potential
>> > > > difference.
>> > > >
>> > > > The limiting issue is the amount of liquid water present.
>> > > > Corrosion engineers consider a layer of water molecules 5 deep
>> > > > to be a "liquid" film. That is the film will behave chemically
>> > > > the same as bulk liquid water. The limitation here is
>the volume
>> > > > of water in the film. The deeper the layer the more
>> > > > ions the water can transport. The chemistry that
>converts water vapor
>> > to
>> > > > liquid is very complex
>> > > > but it does occur on surfaces with as little as 60% RH in the
>> > > > local
>> > area.
>> > > > Just how long the water is there, the amount of water, and the
>> > > > amount
>> > of
>> > > > contamination all combine to
>> > > > cause several failure modes besides dendrites. There are
>> > > > numerous variables involved and the testing can be very
>> > > > expensive. But if you are building high reliability products
>> > > > this testing is needed.
>> > > >
>> > > > David A. Douthit
>> > > > Manager
>> > > > LoCan LLC
>> > > >
>> > > > "Dehoyos, Ramon" wrote:
>> > > >
>> > > > > After reading carefully the inputs from Per-Erik,
>> > > > > Brian and
>> > > > others
>> > > > > it seems that the biasing between traces is a very important
>> > > > > factor
>> > in
>> > > > > dendrite forming which are unwanted shorts. I know
>from first
>> > > > > hand obsevation that sometimes boards are not cleaned well
>> > > > > enough under
>> > BGAs,
>> > > > and
>> > > > > CC under BGAs is done by pure accident in very few cases. So
>> > > > > by
>> > > > conclusion
>> > > > > the traces between BGA balls do not have high enough
>bias for
>> > > > > the
>> > > > dendrites
>> > > > > to form. Because they are not conformal coated , not cleaned
>> > properly in
>> > > > > some cases and RMA flux is used.
>> > > > > Regards,
>> > > > > Ramon
>> > > > >
>> > > > > > -----Original Message-----
>> > > > > > From: Brian Ellis [SMTP:[log in to unmask]]
>> > > > > > Sent: Tuesday, September 09, 2003 8:21 AM
>> > > > > > To: [log in to unmask]
>> > > > > > Subject: Re: [TN] Silicone conformal coating
>> > > > > >
>> > > > > > Per-Erik
>> > > > > >
>> > > > > > Unfortunately, I don't have time just now to discuss this
>> > > > > > further
>> > in
>> > > > > > detail. I agree with you on most points, but let's not
>> > > > > > forget that atmospheric humidity has four components:
>> > > > > >
>> > > > > > - H2O in clumps (mist): this is relatively harmless to
>> > > > > > coatings as
>> > it
>> > > > > > wets or sits on the surface, rather than penetrates
>> > > > > > - H2O as isolated molecules (true humidity). This
>penetrates
>> > > > > > all polymers ± easily
>> > > > > > - H+ as a result of hydrolysis: a very reactive
>and unstable
>> > reducing
>> > > > > > gas which can penetrate and react easily with many
>groups in
>> > > > > > and
>> > under
>> > > > > > the coating.
>> > > > > > - OH- as a result of hydrolysis: a very reactive and
>> > > > > > unstable
>> > > > oxidising
>> > > > > > gas which can penetrate and react easily with many
>groups in
>> > > > > > and
>> > under
>> > > > > > the coating.
>> > > > > >
>> > > > > > The hydrogen radical and hydroxyl group may be just as
>> > > > > > dangerous
>> > as
>> > > > H2S
>> > > > > > and are ever-present in air, constantly forming and
>> > > > > > recombining at random, under the influence of ozone
>> > > > > > molecules. The hydroxyl
>> > group, in
>> > > > > > particular, can play havoc with any loosely bonded
>hydrogen
>> > > > > > atoms
>> > in
>> > > > > > organics it comes in contact with, as H-OH is a much
>> > > > > > stronger bond
>> > > > than
>> > > > > > H-C (this is why many hydrocarbon vapours have a short
>> > > > > > atmospheric residence times: the molecules are literally
>> > > > > > torn apart by
>> > hydroxyls,
>> > > > > > during hydrolysis). As the global average tropospheric
>> > > > > > hydroxyl
>> > > > radical
>> > > > > > concentration is estimated at 8.1 x 10^5 radicals.cm-3 at
>> > > > > > any
>> > single
>> > > > > > moment, this is far from negligible.
>> > > > > >
>> > > > > > I feel this must also be a consideration.
>> > > > > >
>> > > > > > Best regards,
>> > > > > >
>> > > > > > Brian
>> > > > > >
>> > > > > >
>> > > > > >
>> > > > > > Tegehall Per-Erik wrote:
>> > > > > > > Brian
>> > > > > > >
>> > > > > > > What you are saying is that the function of the conformal
>> > coating is
>> > > > to
>> > > > > > act as an impervious barrier against humidity. Thus, a low
>> > > > permeability is
>> > > > > > crucial and the protection afforded is directly related to
>> > > > > > the permeability of the coating. Let's assume to
>begin with,
>> > > > > > that
>> > > > absorption
>> > > > > > of humidity will endanger the reliability of an assembly
>> > > > > > (which I
>> > do
>> > > > not
>> > > > > > agree with if the cleanliness is adequate). Then,
>why should
>> > > > permeability
>> > > > > > be more important than the water absorption level at
>> > > > > > equilibrium
>> > (that
>> > > > is,
>> > > > > > saturation level)? I guess that many assume that a high
>> > permeability
>> > > > also
>> > > > > > automatically means a high water absorption level
>but there
>> > > > > > is no
>> > such
>> > > > > > relation. Silicone materials have a very high permeability
>> > compared to
>> > > > > > most other coating materials but it is also a fact that the
>> > saturation
>> > > > > > level of water is lower for silicone materials than for
>> > > > > > other
>> > > > coatings.
>> > > > > > This means that the amount of water absorbed by a silicone
>> > > > > > coating
>> > > > likely
>> > > > > > is somewhat higher than for other coatings to beg in with,
>> > > > > > but after some time the other coatings will have absorbed
>> > > > more
>> > > > > > water. Which is then most dangerous, a high
>permeability or
>> > > > > > a high saturation level? As in many other discussions on
>> > > > > > TechNet, the
>> > answer
>> > > > is:
>> > > > > > It depends. In this case, among other things, on
>how long it
>> > > > > > will
>> > take
>> > > > to
>> > > > > > reach saturation.
>> > > > > > >
>> > > > > > > About ten years ago I did an experiment to prove that
>> > permeability
>> > > > of a
>> > > > > > coating is not crucial for the protection
>afforded. I coated
>> > > > > > a
>> > comb
>> > > > > > pattern on thoroughly cleaned HASL boards with one
>acrylic,
>> > > > > > one polyurethane and one silicone coating and
>Parylene, each
>> > > > > > with
>> > three
>> > > > > > different thicknesses. I then put the boards in a humidity
>> > > > > > cabinet
>> > and
>> > > > > > increased the temperature to 85 degree C but without any
>> > > > > > added
>> > > > humidity.
>> > > > > > When the temperature had stabilised, the humidity was
>> > > > > > increased to
>> > 85
>> > > > %
>> > > > > > RH. The surface insulation resistance (or rather interface
>> > insulation
>> > > > > > resistance in this case) for the comb patterns on
>the boards
>> > coated
>> > > > with
>> > > > > > the silicone coating decreased instantaneously and
>almost as
>> > > > > > fast
>> > and
>> > > > to
>> > > > > > almost the same level as on a non-coated reference board
>> > > > > > even for thicknesses of up to 150 um. So you are
>right, the
>> > > > > > permeability is
>> > > > very
>> > > > > > high for silicone coatings and the insulation resistance
>> > > > > > will be
>> > > > affected
>> > > > > > and, if that had been important, silicon coatings would be
>> > useless.
>> > > > How
>> > > > > > ever, the results very practically identical for
>the boards
>> > > > > > coated
>> > > > with
>> > > > > > the acrylic and the polyurethane coatings. The SIR
>decreased
>> > > > > > a
>> > little
>> > > > > > slower on the boards coated with Parylene but after about
>> > > > > > one hour
>> > the
>> > > > SIR
>> > > > > > was on about the same level on a board with 50 um Parylene
>> > > > > > as on
>> > the
>> > > > > > boards coated with the other conformal coatings. In fact,
>> > > > > > after
>> > longer
>> > > > > > exposure to humidity, the SIR on the Parylene coated boards
>> > actually
>> > > > > > decreased to the same level as for the noncoated
>board. That
>> > > > > > is,
>> > it
>> > > > > > decreased more for the Parylene coated boards than for the
>> > > > > > boards
>> > > > coated
>> > > > > > with the other coatings. These results show that
>SIR beneath
>> > > > > > a
>> > coating
>> > > > is
>> > > > > > affected very quickly even when Parylene is used
>as coating
>> > > > > > but
>> > they
>> > > > do
>> > > > > > not answer the question how long it will take to reach
>> > > > > > saturation
>> > > > level. I
>> > > > > > haven't measured that but the problem with pop-corning of
>> > > > > > plastic components shows that epoxy materials pick
>up quite
>> > > > > > large amounts
>> > of
>> > > > water
>> > > > > > in a few days, so my guess would be that it is a matter of
>> > > > > > da ys before an acrylic or a polyurethane coating
>has picked
>> > > > > > up as
>> > much
>> > > > water
>> > > > > > as a silicone coating.
>> > > > > > >
>> > > > > > > Is then a high uptake of water to the level of saturation
>> > dangerous?
>> > > > Of
>> > > > > > course not (under condition that the cleanliness is
>> > > > > > adequate). If
>> > had
>> > > > > > been, a coated board would not pass a humidity test.
>> > > > > > >
>> > > > > > > If the cleanliness is not adequate prior to the
>> > > > > > > application of
>> > the
>> > > > > > coating, then the situation is different. Hygroscopic
>> > contamination
>> > > > will
>> > > > > > pick up water through the coating and cause blistering and
>> > > > electrochemical
>> > > > > > migration. I think that you agree that this will
>also happen
>> > > > > > if
>> > you
>> > > > apply
>> > > > > > Parylene to a contaminated surface. Electrochemical
>> > > > > > migration
>> > requires
>> > > > > > three things to occur; contamination, humidity and a bias.
>> > > > > > Thus,
>> > if
>> > > > > > Parylene had been an impermeable barrier against humidity,
>> > > > > > it
>> > would
>> > > > not
>> > > > > > had been necessary to clean the assembly. I agree that
>> > > > > > hygroscopic contamination will be picked up much faster if
>> > > > > > you have a silicone coating. But on the other hand, it is
>> > > > > > only when you have a bias
>> > that
>> > > > > > electrochemical migration will occur. If heat is generated
>> > > > > > when
>> > the
>> > > > > > equipment is used, the assembly will dry up much faster if
>> > > > > > you
>> > have a
>> > > > > > coating with high permeability and low moisture uptake.
>> > > > > > Therefore,
>> > a
>> > > > > > silicone coating may be preferable under such conditions
>> > > > > > (although
>> > it
>> > > > > > should
>> > > > > > verified). If heat is not generated, silicone is
>perhaps not
>> > > > > > the
>> > best
>> > > > > > choice (but again it should be verified). In any case,
>> > > > > > reliability
>> > > > problem
>> > > > > > due to contamination needs to be solved by improving the
>> > cleanliness,
>> > > > and
>> > > > > > not by finding a coating that will delay failures somewhat.
>> > > > > > >
>> > > > > > > What is then the function of a conformal
>coating? It is to
>> > eliminate
>> > > > the
>> > > > > > third factor causing electrochemical migration (and
>> > > > > > blistering)
>> > from
>> > > > the
>> > > > > > surface beneath the coating by preserving a
>cleanliness that
>> > > > > > have
>> > been
>> > > > > > achieved by cleaning prior to application of the conformal
>> > coating.
>> > > > Thus
>> > > > > > it needs to be an impermeable barrier, but towards
>ionic and
>> > > > hygroscopic
>> > > > > > contamination from the field environment and not towards
>> > > > > > humidity.
>> > It
>> > > > may
>> > > > > > also need to protect the circuitry from being in direct
>> > > > > > contact
>> > with a
>> > > > > > condensed water film on the assembly. (Thus, air is
>> > > > > > disqualified
>> > as
>> > > > > > replacement for a conformal coating.) I have not seen any
>> > > > > > data of
>> > the
>> > > > > > permeability of various contaminants in conformal coatings
>> > > > > > but I
>> > guess
>> > > > > > that most coating have very low permeability of ionic
>> > contaminants.
>> > > > > > Organic contaminants may be a problem since they may be
>> > > > > > absorbed.
>> > I
>> > > > also
>> > > > > > have to admit that if you have corrosive gaseous
>pollutions
>> > > > > > such
>> > as
>> > > > > > hydrogen sulfide, silicone coating is a bad choice
>since it
>> > > > > > h as a high permeability for most gaseous pollutions.
>> > > > > > >
>> > > > > > > Then, why does Parylene generally afford a much better
>> > protection
>> > > > than
>> > > > > > other coatings? It is because it affords better protection
>> > > > > > against contamination from the field environment, not
>> > > > > > because better
>> > barrier
>> > > > > > properties but because of better sealing properties due to
>> > > > > > better coverage. With Parylene, you will get a
>coating with
>> > > > > > even
>> > thickness on
>> > > > all
>> > > > > > surfaces, even on the tip of a needle. It is very
>difficult
>> > > > > > to get
>> > > > good
>> > > > > > coverage with other types of coatings since the coverage of
>> > protruding
>> > > > > > parts such as solder joints and component leads due to
>> > gravitation,
>> > > > > > surface tension and capillary forces.
>> > > > > > >
>> > > > > > > Per-Erik Tegehall
>> > > > > > > IVF
>> > > > > > >
>> > > > > > > -----Ursprungligt meddelande-----
>> > > > > > > Från: Brian Ellis [mailto:[log in to unmask]]
>> > > > > > > Skickat: den 6 september 2003 09:48
>> > > > > > > Till: TechNet E-Mail Forum.; Tegehall Per-Erik
>> > > > > > > Ämne: Re: [TN] Silicone conformal coating
>> > > > > > >
>> > > > > > >
>> > > > > > > Per-Erik
>> > > > > > >
>> > > > > > > An interesting idea. Briefly, you are proposing a more
>> > > > > > > permeable
>> > > > coating
>> > > > > > > so that humidity can leave, as well as enter. I suggest
>> > > > > > > that if
>> > > > these
>> > > > > > > conditions apply, then the best coating would be the most
>> > permeable.
>> > > > > > > Probably 90% or more of electronic assemblies use such a
>> > coating. It
>> > > > is
>> > > > > > > called air. It is extremely successful for the
>conditions
>> > > > > > > under
>> > > > which
>> > > > > > > such circuits are normally used. Conformal coating is
>> > > > > > > usually
>> > used
>> > > > when
>> > > > > > > air-coating is unsuitable, for whatever reason.
>Therefore,
>> > > > > > > we
>> > need
>> > > > > > > something as far removed from the conditions of air as
>> > > > > > > possible,
>> > > > such as
>> > > > > > > a theoretically impervious skin. The nearest we have to
>> > > > > > > this in
>> > our
>> > > > > > > armoury of weapons of mass construction is para-xylylene
>> > > > > > > (Paralene/Parylene). This is near-ideal, but
>expensive and
>> > difficult
>> > > > to
>> > > > > > > apply, so we usually look to other materials. I would
>> > > > > > > suggest
>> > that
>> > > > > > > acrylics are closest to this ideal, except that
>they have
>> > > > > > > poor temperature and chemical resistances. So
>the choice,
>> > > > > > > IMHO is
>> > either
>> > > > air,
>> > > > > > > with maximum permeability, or a product with minimal
>> > permeability.
>> > > > > > > Compromises between the two are probably second-best.
>> > > > > > >
>> > > > > > > Brian
>> > > > > > >
>> > > > > > > Tegehall Per-Erik wrote:
>> > > > > > >
>> > > > > > >>After having thought a little more on this, I
>will expound
>> > > > > > >>my
>> > > > answer. It
>> > > > > > >>seems that all assume that high permeability is a bad
>> > > > > > >>thing but
>> > in
>> > > > my
>> > > > > > >>opinion it is not that simple and a high
>permeability may
>> > > > > > >>even
>> > be
>> > > > > > >>preferable. If you have adequate cleanliness on the
>> > > > > > >>assembly
>> > prior
>> > > > to
>> > > > > > >>applying the coating, the moisture penetrating
>the coating
>> > > > > > >>will
>> > not
>> > > > be a
>> > > > > > >>problem and the permeability will then not be an
>issue. It
>> > > > > > >>is
>> > when
>> > > > you
>> > > > > > >>have to much hygroscopic and ionic contamination beneath
>> > > > > > >>the
>> > coating
>> > > > > > >>that you may get problem with delamination and
>> > > > > > >>electrochemical migration. Even if you use
>Parylene, quite
>> > > > > > >>a lot of moisture
>> > will be
>> > > > > > >>picked up by hygroscopic contamination beneath
>it in a few
>> > > > > > >>days
>> > in a
>> > > > > > >>humid environment. If you then turn the euipment on and
>> > > > > > >>the
>> > board is
>> > > > > > >>heated due to power dissipation, it will take
>much longer
>> > > > > > >>time
>> > to
>> > > > dry up
>> > > > > > >>the assembly if you have a coating with low water
>> > > > > > >>permeability.
>> > And
>> > > > it
>> > > > > > >>is during this time period electrochemical
>migration will
>> > > > > > >>occur. Therefore, a silicone coating may actually be
>> > > > > > >>better than
>> > Parylene
>> > > > in
>> > > > > > >>this case.
>> > > > > > >>
>> > > > > > >>Per-Erik Tegehall
>> > > > > > >>IVF
>> > > > > > >>
>> > > > > > >> -----Ursprungligt meddelande-----
>> > > > > > >> Från: Tegehall Per-Erik
>> > > > > > >> Skickat: den 5 september 2003 08:38
>> > > > > > >> Till: [log in to unmask]
>> > > > > > >> Ämne: Re: [TN] Silicone conformal coating
>> > > > > > >>
>> > > > > > >> Steve,
>> > > > > > >>
>> > > > > > >> It depends on what you mean with good moisture
>> > > > > > >> resistance.
>> > All
>> > > > > > >> conformal coatings absorbs moisture but the
>diffusion
>> > > > > > >> rates
>> > of
>> > > > water
>> > > > > > >> in the coatings and the saturation level
>varies. Water
>> > molecules
>> > > > > > >> have a high diffusion rate in silicone coatings but
>> > > > > > >> the
>> > > > saturation
>> > > > > > >> level is lower than in most other coatings. Which is
>> > > > > > >> to be
>> > > > prefered?
>> > > > > > >> It probably depend on the application.
>> > > > > > >>
>> > > > > > >> However, a general statement of good
>moisture resistance, I
>> > > > > > >> interpret as that the coating properties are not
>> > > > > > >> degraded by
>> > > > > > moisture.
>> > > > > > >>
>> > > > > > >> Per-Erik Tegehall
>> > > > > > >> IVF
>> > > > > > >>
>> > > > > > >> -----Ursprungligt meddelande-----
>> > > > > > >> Från: Steve Gregory [mailto:[log in to unmask]]
>> > > > > > >> Skickat: den 4 september 2003 21:35
>> > > > > > >> Till: [log in to unmask]
>> > > > > > >> Ämne: [TN] Silicone conformal coating
>> > > > > > >>
>> > > > > > >> Hi All!
>> > > > > > >>
>> > > > > > >> I know when you look up properties for Silicone
>> > conformal
>> > > > > > >> coating, it usually states that it has good
>> > > > > > >> moisture
>> > > > resistance,
>> > > > > > >> but is it really that good?
>> > > > > > >>
>> > > > > > >> I've heard that it is somewhat permeable to
>> > > > > > >> moisture,
>> > that
>> > > > if
>> > > > > > >> you were worried about moisture, and the
>assembly
>> > > > > > >> were
>> > going
>> > > > to
>> > > > > > >> see the outside environment, you would be better
>> > > > > > >> off
>> > with an
>> > > > > > >> acrylic, or urethane coating.
>> > > > > > >>
>> > > > > > >> Any thoughts?
>> > > > > > >>
>> > > > > > >> Thanks!
>> > > > > > >>
>> > > > > > >> -Steve Gregory-
>> > > > > > ---------------------------------------------------
>> > > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > >
>> > > > > > ---------------------------------------------------
>> > > > > > Technet Mail List provided as a service by IPC using
>> > > > > > LISTSERV 1.8e To unsubscribe, send a message to
>> > > > > > [log in to unmask] with following
>> > text
>> > > > in
>> > > > > > the BODY (NOT the subject field): SIGNOFF Technet To
>> > > > > > temporarily halt or (re-start) delivery of Technet send
>> > > > > > e-mail
>> > to
>> > > > > > [log in to unmask]: SET Technet NOMAIL or (MAIL)
>> > > > > > To receive ONE mailing per day of all the posts:
>send e-mail
>> > > > > > to
>> > > > > > [log in to unmask]: SET Technet Digest
>> > > > > > Search the archives of previous posts at:
>> > > > http://listserv.ipc.org/archives
>> > > > > > Please visit IPC web site
>> > > > http://www.ipc.org/contentpage.asp?Pageid=4.3.16
>> > > > > > for additional information, or contact Keach Sasamori at
>> > > > [log in to unmask] or
>> > > > > > 847-509-9700 ext.5315
>> > > > > > -----------------------------------------------------
>> > > > >
>> > > > > ---------------------------------------------------
>> > > > > Technet Mail List provided as a service by IPC using
>LISTSERV
>> > > > > 1.8e To unsubscribe, send a message to [log in to unmask] with
>> > > > > following
>> > text
>> > > > in
>> > > > > the BODY (NOT the subject field): SIGNOFF Technet
>> > > > > To temporarily halt or (re-start) delivery of Technet send
>> > > > > e-mail to
>> > > > [log in to unmask]: SET Technet NOMAIL or (MAIL)
>> > > > > To receive ONE mailing per day of all the posts: send e-mail
>> > > > > to
>> > > > [log in to unmask]: SET Technet Digest
>> > > > > Search the archives of previous posts at:
>> > > > http://listserv.ipc.org/archives
>> > > > > Please visit IPC web site
>> > > > http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
>additional
>> > > > information, or contact Keach Sasamori at [log in to unmask] or
>> > 847-509-9700
>> > > > ext.5315
>> > > > > -----------------------------------------------------
>>
>> ---------------------------------------------------
>> Technet Mail List provided as a service by IPC using
>LISTSERV 1.8e To
>> unsubscribe, send a message to [log in to unmask] with
>following text in
>> the BODY (NOT the subject field): SIGNOFF Technet To
>temporarily halt
>> or (re-start) delivery of Technet send e-mail to
>[log in to unmask]: SET
>> Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the
>> posts: send e-mail to [log in to unmask]: SET Technet Digest
>Search the
>> archives of previous posts at:
>http://listserv.ipc.org/archives Please
>> visit IPC web site
>http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
>additional information, or contact Keach Sasamori at
>[log in to unmask] or 847-509-9700 ext.5315
>> -----------------------------------------------------
>
>---------------------------------------------------
>Technet Mail List provided as a service by IPC using LISTSERV
>1.8e To unsubscribe, send a message to [log in to unmask] with
>following text in the BODY (NOT the subject field): SIGNOFF
>Technet To temporarily halt or (re-start) delivery of Technet
>send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
>To receive ONE mailing per day of all the posts: send e-mail
>to [log in to unmask]: SET Technet Digest Search the archives of
>previous posts at: http://listserv.ipc.org/archives Please
>visit IPC web site
>http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
>additional information, or contact Keach Sasamori at
>[log in to unmask] or 847-509-9700 ext.5315
>-----------------------------------------------------
>
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
