On 12 August Edward Boucher wrote:

From: Edward Boucher <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 12 August 1998 22:04
Subject: [TN] The ideal eletronic encapsulation material?


> Does anyone know of a encapsulating material for electronics, which can
>meet  the majority of these parameters?  We have been searching for about a
>year and have had little success.
>
>The Ideal Encapsulation Material
>
>a.  low toxicity
>b.  low moisture permeability
>c.  no or very low ionic content
>d.  low viscosity
>e.  low linear shrinkage
>f.  low glass transition temperature (Tg)
>g.  low Coefficient Of Expansion (CTE)
>h.  low embedment stress
>i.  high tensile strength
>j.  high thermal conductivity
>k.  void free
>l.  electrical insulation properties
>m.  thermal cycling stability
>n.  high thermal shock resistance
>o.  wide temperature range -55 to 95 degrees C
>p.  good chemical and solvent resistance
>q.  good adhesion
>r.  low cost
>s.  ease of processing (application and clean up)
>t.  no formation of water
>u.  non-corrosive
>v.  easily repairable


Is that all?? How about x y and z and then maybe you could have gone alpha
numeric?

However, the good news is that we can provide you with a material that will
meet pretty much the whole of your considerable "Wish List".

For the record, your Wish List featured in the requirements of the US Auto
industry around 10 years ago and everyone said: "Yeah! Dream on!" We just
got on with it and produced:

Single component SolventLESS silicone conformal coatings. These comply with
your Wish List as follows:

a thru h, no problem.

i   High tensile strength: I assume you mean something that won't tear
easily during any de-mask operations? Or do you mean something else? Please
advise.

j   High thermal conductivity: As conformal coatings are applied at an
average thickness of 3 mils (0.003 inches) their thermal conductivity will
be pretty good - in other words, they are not good thermal insulators. You
should find that the efficiency of any heat sinks will be minimally
influenced.

k thru p: no problem. Note that thermal shock we easily pass -65 deg C to
+200 deg C over 1000 cycles.

q  Good adhesion: Ah! That perennial favourite of mine. Please see my
earlier posting on this topic: "Adhesion and Reliability." Remember that a
silicone will not really allow anything to stick to it so any form of
adhesion test it will pass easily - but for the wrong reasons! However,
these materials do exhibit excellent mar resistance and are becoming the
first choice in the Auto industry.

r   Low cost: Well of course! All things are relative - and these are
relatively expensive! Depends upon your production volume. The Auto industry
hates high cost and they use the product! If you are buying 100's of tons
per year - yeah! Low cost.

s thru u: No problem.

v   Easily repairable: We have new silicone digesters that make repair
simple - soak and wash! However, you can imagine that anything that will
dissolve a silicone will not necessarily be a product you put on your
wheaty-bangs!

Anything else? Well, they FULLY cure in around 10 minutes and they contain
NO SOLVENTS!

Interested in more info? Call me:

Regards, Graham Naisbitt

[log in to unmask]

Concoat Ltd             Phone: +44 1276 691100
Alasan House          Fax:      +44 1276 691227
Albany Park
CAMBERLEY
GU15 2PL UK

Any opinions expressed are those of this employer.

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