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June 2009

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Subject:
From:
Steven Creswick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steven Creswick <[log in to unmask]>
Date:
Fri, 5 Jun 2009 09:06:24 -0400
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Doug,

I consider an under-fill as an adhesive, and elasto-plastic to be an
adjective describing the underfill's properties.       ....What would an
under-fill be without the ability to adhere to the surfaces involved??

In very quick consideration, I classify an under-fill as:

a material [vs process], 
a polymer [vs metallic/non-organic],
an adhesive [vs a non-adhesive]

As far as the cured properties of the underfill go, I consider them to
properties common to:
a thermoset, thermoplastic, hybrid thermoset/thermoplastic [and would
consider elasto-plastic to be fourth variant possibly most descriptive of
products with a dominant silicone backbone, ... with more property
descriptors sure to follow].

Some simple thoughts for a Friday morning.

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Friday, June 05, 2009 8:24 AM
To: [log in to unmask]
Subject: Re: [TN] Coating, Encapsulation, and Potting

I would agree.  It seems that there is a concensus that "encapsulation" is 
the high level term, with the others being sub terms or lower level, as 
Ben suggests.

I will see if I can distill the inputs a little, let the subconcious work 
on them over the weekend and next week come up with the next round of 
questions.

For now, let me ask this:  would you consider an underfill material as a 
material in the "adhesive" class? 

I was having a conversation this week with Barry Ritchie of Dow Corning 
and he used an interesting term - elastoplastic.  It would seem to me that 
an underfill would be an elastoplastic material.

Doug Pauls
Rockwell Collins



"Gumpert, Ben" <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
06/05/2009 07:02 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Gumpert, Ben" <[log in to unmask]>


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Subject
Re: [TN] Coating, Encapsulation, and Potting






I don't have a suggestion for definitions, just one of organization:

I see all of these terms (potting, coating, underfill) as being
sub-classes to the overall group of encapsulants, with the term
encapsulant being used when the others do not apply.

Ben

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Fjelstad
Sent: Thursday, June 04, 2009 3:04 PM
To: [log in to unmask]
Subject: Re: [TN] Coating, Encapsulation, and Potting

Interesting question Doug
 
1) My mental image is that it is that the term is related to processing

and potting is most often done atmospherically, with occasional vacuum
assist 
and encapsulation under pressure but it is pretty fungible with  lots of

fuzziness between the two. A potted assembly is definitely encapsulated
when 
finished. 
 
2) Likely? Yes but don't know where
 
3) Thickness of the coating seems reasonable but don't know where to
draw 
the line. 250 micron? 100? 500? Perhaps a percentage of total
thickness? 
5%? 10%?
 
4) In neither (or both depending on process). The other  two generally 
provide complete coverage of the device or assembly  underfill is by
definition 
partial. 
 
Joe 
 
 
In a message dated 6/4/2009 11:33:27 A.M. Pacific Daylight Time, 
[log in to unmask] writes:

Good  afternoon all,

All this talk of underfill sparked a reminder of an IPC  action item of 
mine.  Unknownst to most of you , I signed you all up  on some of my 
committees.  There will be a new task group addressing  potting and 
encapsulation, which will meet at the Fall IPC.  We  already have
conformal 
coat task groups. 

So, I wish to initiate a  series of questions and illuminating debate. 
Pardon me if I fall short on  the illumination part (leave it alone
Dewey).

1.  What would you  consider to be a definition of "potting" and a 
definition of  "encapsulation"? 

2.  Are there standard definitions for these  somewhere?  They don't
exist 
in IPC as far as I know.

3.   What would you consider to be the boundary between conformal
coating 
and  "potting or encapsulation"?  I have my own opinions but want to
hear 
yours.

4.  In what class would you consider an underfill to be  in?

That's enough homework for now. 

Doug Pauls
Rockwell  Collins

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