MarkAren wrote:
Hi All,

Has anyone attempted to use good old fashioned hot melt glue as an
encapsulant for modules ?

Probably needs melting in a pot over a flame (with appropriate care).

A mould could me made out of Plexiglass with appropriate draft
(angles) and high temperature release agent.

A second thought is to use standard two part fiberglass mix, obviously
a lot more rigid, but potting boxes are likely to be needed also.

I guess I could use thin walled pipe to house a long rectifier stack
and associated capacitors.

Both of these options seem significantly less expensive than standard
epoxy potting compound...

Any thoughts ?

Mark
Watch out for resins or epoxy. There are big stains put on the parts
when it sets, and again over temperature changes. I've tried it, and had
parts break in two inside the resin. The potting has to have some give.

Jim

On Tue, 18 Dec 2007 00:28:58 -0800, MarkAren wrote:

Hi All,

Has anyone attempted to use good old fashioned hot melt glue as an
encapsulant for modules ?

Probably needs melting in a pot over a flame (with appropriate care).

A mould could me made out of Plexiglass with appropriate draft (angles)
and high temperature release agent.

A second thought is to use standard two part fiberglass mix, obviously a
lot more rigid, but potting boxes are likely to be needed also.

I guess I could use thin walled pipe to house a long rectifier stack and
associated capacitors.

Both of these options seem significantly less expensive than standard
epoxy potting compound...

Any thoughts ?

Mark

Im suprised nobody has bothered to ask this....

What is the potting being used for? Moisture, vibration, HV isolation ??

Depending on the use, the 'good enough' alternative might vary
considerably.

--Teh

On Dec 18, 7:28 pm, MarkAren wrote:
Hi All,

Has anyone attempted to use good old fashioned hot melt glue as an
encapsulant for modules ?

Probably needs melting in a pot over a flame (with appropriate care).

A mould could me made out of Plexiglass with appropriate draft
(angles) and high temperature release agent.

A second thought is to use standard two part fiberglass mix, obviously
a lot more rigid, but potting boxes are likely to be needed also.

I guess I could use thin walled pipe to house a long rectifier stack
and associated capacitors.

Both of these options seem significantly less expensive than standard
epoxy potting compound...

Any thoughts ?

Mark

Epoxy, as described by others, tends to stress the components - one
notable job I had was the vco in a Yaesu FT480R - took AGES to chip
away with a fine wood chisel after using a blowtorch to open up the
brass enclosure.....one of those "personal challenge" jobs.

I use good old fashioned beeswax. Good rf properties, easy to use,
easy to dig out if needed. Bugger all mechanical strength, but ideal
for vibration damping ie oscillators etc. Repotted the Yaesu VCO, no
reported problems after 3 years....

Andrew VK3BFA.

Epoxy, as described by others, tends to stress the components - one
notable job I had was the vco in a Yaesu FT480R - took AGES to chip
away with a fine wood chisel after using a blowtorch to open up the
brass enclosure.....one of those "personal challenge" jobs.

Several notes re epoxy for encapsulation:

- Epoxy formulations vary a lot in their hardness and rigidity,
viscosity when fluid, cure rate, and rapidity of heat release
during cure. Most of the big epoxy companies seem to make at least
one variety which is specifically intended for use when
encapsulating electronic components. These formulas seem to be
more flexible when cured, and some of them are being advertised as
providing shock and thermal-stress protection.

- Other commercial electronic-gear encapsulants seem to be based on
urethane, or on two-part silicone rubber formulas.

- I've had some success in doing small encapsulating projects by using
a mixture of a low-viscosity slow-cure epoxy (one of the TAP
Plastics formulas) and fine white sand, mixed up in a thick slurry.
This mix is a good deal less expensive than using straight epoxy
resin, it has much less shrinkage, and should have rather better
thermal conductivity. When it's poured into a mold, the sand tends
to settle to the bottom before the epoxy hardens, leaving the top
layer in the mold as nearly-pure resin (a nice smooth surface).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

I had occasion to pot very high impedance circuit in 2 part black
potting compound, when apparently set it failed to function correctly,
after 2 days all was ok.
my conclusion was that the chemical reaction was generating conducting
ions and conduction ceased when the reaction finished.

Dave Platt wrote:

Epoxy, as described by others, tends to stress the components - one
notable job I had was the vco in a Yaesu FT480R - took AGES to chip
away with a fine wood chisel after using a blowtorch to open up the
brass enclosure.....one of those "personal challenge" jobs.

Several notes re epoxy for encapsulation:

- Epoxy formulations vary a lot in their hardness and rigidity,
viscosity when fluid, cure rate, and rapidity of heat release
during cure. Most of the big epoxy companies seem to make at least
one variety which is specifically intended for use when
encapsulating electronic components. These formulas seem to be
more flexible when cured, and some of them are being advertised as
providing shock and thermal-stress protection.

- Other commercial electronic-gear encapsulants seem to be based on
urethane, or on two-part silicone rubber formulas.

- I've had some success in doing small encapsulating projects by using
a mixture of a low-viscosity slow-cure epoxy (one of the TAP
Plastics formulas) and fine white sand, mixed up in a thick slurry.
This mix is a good deal less expensive than using straight epoxy
resin, it has much less shrinkage, and should have rather better
thermal conductivity. When it's poured into a mold, the sand tends
to settle to the bottom before the epoxy hardens, leaving the top
layer in the mold as nearly-pure resin (a nice smooth surface).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Pete KE9OA wrote:

TenTec used hot melt glue in the VCO modules of the Paragon transceiver, so
this glue probably has good RF characteristics (hopefully).

A way to test hot melt glue would be to place a small piece on a paper
plate in the microwave oven, along with a cup of coffee to the side (as
a dummy load to keep the oven happy). See if it gets warm.

Has anyone attempted to use good old fashioned hot melt glue as an
encapsulant for modules ?

Probably needs melting in a pot over a flame (with appropriate care).

A double boiler set up may be better for that.




Both of these options seem significantly less expensive than standard
epoxy potting compound...

I suppose an advantage of hot melt glue is that you could de-encapsulate
stuff easier if you ever needed to.

Some "pro" potting compounds are 2-part RTV rubber. This presumably has
a bit more "give" than a rigid epoxy & is less likely to rip parts off a
board.

Kenwood used something like that in the TS440SAT transceiver, on the VCO
if I recall correctly. Seems the stuff would sometimes corrode some of
the circuitry after several years.