(OT) Electronics injection moldable material

[Mook Johnson]

I'm looking for a light injection moldable (or pourable) material that has
these properties.

1) dielectric and non shielding to RF signals

2) non corrosive to electrical components (electronics can be conformal
coated if this can't be met)

3) Floats on water when cured (light weight)

4) curing process does not damage SMT electrical components (not extreme
high temperatures etc.)

thanks

 

[Rich Grise]

On Sat, 16 Apr 2005 12:43:38 +0000, Mook Johnson wrote:

I'm looking for a light injection moldable (or pourable) material that has
these properties.

1) dielectric and non shielding to RF signals

2) non corrosive to electrical components (electronics can be conformal
coated if this can't be met)

3) Floats on water when cured (light weight)

4) curing process does not damage SMT electrical components (not extreme
high temperatures etc.)

http://www.google.com/search?q=polyurethane+foam

Good Luck!
Rich

 

[Mook Johnson]

A few more requirements to narrow it down.

5) It should be rubbery and not rigid since it will be handled a lot and
should not be dented when it is slightly pinched or bumped into metal sharp
objects

6) should not soak up water

7) should not melt or get gooey when exposed to gasoline, oil or alcohol.

did I mention it still has to float?


thanks

I looked at the polyurethane foam and while it meet my original posted
requirements I don't think it will be rugged enough for continuous handling
and bumps and dings.

This guy will be velcroed to a vibrating and buzzing R/C boat (hence the
fuel and oil exposure) and may fly off and land in the water from time to
time (must float, and not soak in water).

The handling is folks dropping it on the cement launch pad, tossing it in
their field box with pliers, screwdrivers, etc bumping/rubbing against it.

I'm thinking something more like an RTV with microbaloons in it. or similar.



"Mook Johnson" <mook@mook.net> wrote in message
news:_L78e.3326$h6.2052@tornado.texas.rr.com...

I'm looking for a light injection moldable (or pourable) material that has
these properties.

1) dielectric and non shielding to RF signals

2) non corrosive to electrical components (electronics can be conformal
coated if this can't be met)

3) Floats on water when cured (light weight)

4) curing process does not damage SMT electrical components (not extreme
high temperatures etc.)

thanks

 

[John Woodgate]

I read in sci.electronics.design that Mook Johnson <mook@mook.net> wrote
(in <1vb8e.3356$h6.2019@tornado.texas.rr.com&gt about '(OT) Electronics
injection moldable material', on Sat, 16 Apr 2005:

I looked at the polyurethane foam and while it meet my original posted
requirements I don't think it will be rugged enough for continuous
handling and bumps and dings.

Shrink wrap it over the PE foam. You could drop it from the Moon and it
would bounce.(;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Richard H.]

Mook Johnson wrote:

A few more requirements to narrow it down.

5) It should be rubbery and not rigid since it will be handled a lot and
should not be dented when it is slightly pinched or bumped into metal sharp
objects

6) should not soak up water

7) should not melt or get gooey when exposed to gasoline, oil or alcohol.

I've previously explored a similar project, and you're headed down the
right path using a soft material. A hard casting material will break
the solder joints during thermal cycling.

You'll find loads of educational info at this site about resins, Shore
hardness (one scale for solids, one for pliables), casting, and other
accessories. They sell a wide range of types and colors, and you can
get small sample kits; however, they have zero info on their electrical
properties, so you'd need to test for yourself.
http://www.smooth-on.com/Default.htm

These guys are targeted at the electronics space:
http://www.electrolube.co.uk/docs/resins.html
http://www.masterbond.com/

I also found a couple Yahoo forums on casting that were good for general
tips (degassing, etc.)

I looked at the polyurethane foam and while it meet my original posted
requirements ...

Including gasoline tolerance?

Good luck,
Richard

 

[Mook Johnson]

thanks for the reply.

I didn't list gasoline in the original post which is why I supplemented it
with this one.

the poly foam with adhesive lined Polyolefin heat shrink tubing is an
interesting option. Doesn't look professional though.....hmmmm

good for prototypes though.






"Richard H." <rh86@no.spam> wrote in message
news:9bi8e.303$Zi.59@fed1read04...

Mook Johnson wrote:
A few more requirements to narrow it down.

5) It should be rubbery and not rigid since it will be handled a lot and
should not be dented when it is slightly pinched or bumped into metal
sharp objects

6) should not soak up water

7) should not melt or get gooey when exposed to gasoline, oil or alcohol.


I've previously explored a similar project, and you're headed down the
right path using a soft material. A hard casting material will break the
solder joints during thermal cycling.

You'll find loads of educational info at this site about resins, Shore
hardness (one scale for solids, one for pliables), casting, and other
accessories. They sell a wide range of types and colors, and you can get
small sample kits; however, they have zero info on their electrical
properties, so you'd need to test for yourself.
http://www.smooth-on.com/Default.htm

These guys are targeted at the electronics space:
http://www.electrolube.co.uk/docs/resins.html
http://www.masterbond.com/

I also found a couple Yahoo forums on casting that were good for general
tips (degassing, etc.)

I looked at the polyurethane foam and while it meet my original posted
requirements ...

Including gasoline tolerance?

Good luck,
Richard

 

RTV sucks up solvents like a sponge. Epoxy with microballons?
Exotherm might be problem in a large mass.


On Sat, 16 Apr 2005 12:43:38 GMT, "Mook Johnson" <mook@mook.net>
wrote:

I'm looking for a light injection moldable (or pourable) material that has
these properties.

1) dielectric and non shielding to RF signals

2) non corrosive to electrical components (electronics can be conformal
coated if this can't be met)

3) Floats on water when cured (light weight)

4) curing process does not damage SMT electrical components (not extreme
high temperatures etc.)

thanks