I was going to comment only on #3, but curiosity won and I had to pick up
some books.
1. When I think of potting, I think of electrical ballasts (like
mentioned a couple days ago, trying to remove the tar/pitch). Potting
materials encapsulate, but I don't consider encapsulants as potting
materials. Potting is more a 'gross' application, such as dispensing
grams of material to fill up a housing. Encapsulants are finer controlled
dispensing material in only specific isolated areas.
2. I'm not aware of any IPC definition. But, in Plastics Materials and
Processes by Charles Harper and Edward Petrie the section on Encapsulation
starts with "Encapsulation (also called potting) ...".
In another book by Charles Harper, Electronic Packaging and
Interconnection Handbook, encapsulation is defined as "Completely
enclosing a component in a coating of a viscous resin system by dipping,
spraying, or embedding with or without a mold. The coated component is
usually irregular in shape." Potting is defined "Similar to embedding,
except the mold (can or case) remains a part of the system." Embedding is
defined as "Surrounding a part or component positioned in a mold with a
liquid resin system, curing the resin, and removing it for use."
3. If the thickness is greater than that specified in IPC-CC-830 (or
MIL-I-46058C), then I'd move from the conformal coating group to the
encapsulant group. For example, 8 mil of a silicone could still be
considered a conformal coating, 10 mil would be an encapsulant.
4. Underfills are outside my area of expertise. But, I don't see how
they could be classified as any of the mentioned. I saw underfills
referenced in Plastics Materials and Processes as an electronic plastic.
Lamar
Douglas Pauls <[log in to unmask]>
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06/04/2009 02:33 PM
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[TN] Coating, Encapsulation, and Potting
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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