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Encasing in resin.... — Parallax Forums

Encasing in resin....

ArchiverArchiver Posts: 46,084
edited 2001-05-03 01:58 in General Discussion
Believe it or not this is stamp related......

For the advanced electronics gang....

In your opinion....Is there any problem with encasing completed circuits
in polyester resin?

The final product needs to be tamperproof and very moisture resistant
and it seemed like this could be a very good alternative....

Any potential problems with components??

Thanks!!

Rus

--
Bones
"Ghoul-Will Ambassador to the Boneyard"
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"my mind wanders....I'm just along for the ride"

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2001-05-02 20:37
    There are several compounds especially for this "potting".

    Flexane is flexible and we used to use it like coffee around here when we
    used to build instruments that went in the water. If you want to pot with
    something hard they make that stuff too. Years ago we used to use a hard
    plastic potting compound but I can't remember the name. It was by Hysol
    which was bought by Dexter if I recall. Look at
    http://www.dexelec.com/html/electronic_products_-_dexter_h.html

    You want something with very low conductivity and also something that
    doesn't generate very hot temperatures when curing. Shrinking is also a
    problem in some cases.

    We used to buy that stuff by the drum. For small runs look at
    http://www.mgchemicals.com/products/832b.html (about $100 if memory serves).




    At high frequencies the dielectric constant of the compound can become
    important. Also, don't plan on getting back inside. Usually, once they are
    potted, they are in for good. When I worked for Motorola we used to
    decapsulate plastic parts, but it required a mill, a hot plate, fuming
    Nitric acid, and a lot of practice and patience.

    Regards,

    Al Williams
    AWC
    * Expand your Stamp I/O: http://www.al-williams.com/awce/pak3.htm



    >
    Original Message
    > From: Rus Hardy [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=B_5r5UKkt3jWYdixZ8x0H4ECr2P9EB8R7mXebaZ-tloVeDA7NjS2wkNni4wzzaMG3Eu9egmKqIxMWdoPSvtL]rushardy@m...[/url
    > Sent: Wednesday, May 02, 2001 12:26 PM
    > To: Stamp Group
    > Subject: [noparse][[/noparse]basicstamps] Encasing in resin....
    >
    >
    > Believe it or not this is stamp related......
    >
    > For the advanced electronics gang....
    >
    > In your opinion....Is there any problem with encasing completed circuits
    > in polyester resin?
    >
    > The final product needs to be tamperproof and very moisture resistant
    > and it seemed like this could be a very good alternative....
    >
    > Any potential problems with components??
    >
    > Thanks!!
    >
    > Rus
    >
    > --
    > Bones
    > "Ghoul-Will Ambassador to the Boneyard"
    > Atrophies - Ghoulishly Original Awards & Trophies
    > http://www.bluedestiny.com/Atrophies/
    > SpiderBucky & SpiderThrifty - Boney Superheroes
    > http://www.bluedestiny.com/SpiderBucky/
    > Keeper of the Bucky-n-Thrifty Flame
    > http://www.boneyardbargains.com/
    > "my mind wanders....I'm just along for the ride"
    >
    >
    >
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >
  • ArchiverArchiver Posts: 46,084
    edited 2001-05-02 21:12
    The problem may be the curing temperatureof poliester. In some cases
    (large volumes and accelerated resisn) may reach at 180 degrees celsius.
    Many components may not resist. Epoxi adhesives like normal Araldite
    (24h) with slow curing time is more recomended.
    ACJacques


    Rus Hardy wrote:
    >
    > Believe it or not this is stamp related......
    >
    > For the advanced electronics gang....
    >
    > In your opinion....Is there any problem with encasing completed circuits
    > in polyester resin?
    >
    > The final product needs to be tamperproof and very moisture resistant
    > and it seemed like this could be a very good alternative....
    >
    > Any potential problems with components??
    >
    > Thanks!!
    >
    > Rus
    >
    > --
    > Bones
    > "Ghoul-Will Ambassador to the Boneyard"
    > Atrophies - Ghoulishly Original Awards & Trophies
    > http://www.bluedestiny.com/Atrophies/
    > SpiderBucky & SpiderThrifty - Boney Superheroes
    > http://www.bluedestiny.com/SpiderBucky/
    > Keeper of the Bucky-n-Thrifty Flame
    > http://www.boneyardbargains.com/
    > "my mind wanders....I'm just along for the ride"
    >
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
  • ArchiverArchiver Posts: 46,084
    edited 2001-05-02 23:19
    Yes, slow curing time is a must. One thing you might also consider is
    that some epoxies might weaken or damage the insulation around a wire
    due to chemicals in the epoxy. Because of this I would use some sort
    of plug. i.e. SIP HEADERS: If I remember right Digi-Key has a nice
    AUGAT breakaway SIP STRIP with male on one side female on the other
    which makes for nice customized connectors.


    >The problem may be the curing temperatureof poliester. In some cases
    >(large volumes and accelerated resisn) may reach at 180 degrees celsius.
    >Many components may not resist. Epoxi adhesives like normal Araldite
    >(24h) with slow curing time is more recomended.
    >ACJacques
    >
    >
    >Rus Hardy wrote:
    > >
    > > Believe it or not this is stamp related......
    > >
    > > For the advanced electronics gang....
    > >
    > > In your opinion....Is there any problem with encasing completed circuits
    > > in polyester resin?
    > >
    > > The final product needs to be tamperproof and very moisture resistant
    > > and it seemed like this could be a very good alternative....
    > >
    > > Any potential problems with components??
    > >
    > > Thanks!!
    > >
    > > Rus
    Beau Schwabe IC Mask Designer
    National Semiconductor Wired Communications Division
    500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
  • ArchiverArchiver Posts: 46,084
    edited 2001-05-02 23:41
    Rus,

    We have run in to problems with both epoxies and resins trapping moisture
    as they cured. Not a problem for most circuits, but they can cause
    inference (leakage currents) with very high impedance inputs.

    Mike


    At 12:26 PM 5/2/2001 -0500, you wrote:
    >Believe it or not this is stamp related......
    >
    >For the advanced electronics gang....
    >
    >In your opinion....Is there any problem with encasing completed circuits
    >in polyester resin?
    >
    >The final product needs to be tamperproof and very moisture resistant
    >and it seemed like this could be a very good alternative....
    >
    >Any potential problems with components??
    >
    >Thanks!!
    >
    >Rus

    _________________________________
    Mike Walsh
    walsh@i...
  • ArchiverArchiver Posts: 46,084
    edited 2001-05-03 01:51
    Al,

    This is exactly what I was looking for! Thank you for the links.

    Rus

    Al Williams wrote:

    > There are several compounds especially for this "potting".
    >
    > Flexane is flexible and we used to use it like coffee around here when we
    > used to build instruments that went in the water. If you want to pot with
    > something hard they make that stuff too. Years ago we used to use a hard
    > plastic potting compound but I can't remember the name. It was by Hysol
    > which was bought by Dexter if I recall. Look at
    > http://www.dexelec.com/html/electronic_products_-_dexter_h.html
    >
    > You want something with very low conductivity and also something that
    > doesn't generate very hot temperatures when curing. Shrinking is also a
    > problem in some cases.
    >
    > We used to buy that stuff by the drum. For small runs look at
    > http://www.mgchemicals.com/products/832b.html (about $100 if memory serves).
    >
    > At high frequencies the dielectric constant of the compound can become
    > important. Also, don't plan on getting back inside. Usually, once they are
    > potted, they are in for good. When I worked for Motorola we used to
    > decapsulate plastic parts, but it required a mill, a hot plate, fuming
    > Nitric acid, and a lot of practice and patience.
    >
    > Regards,
    >
    > Al Williams
    > AWC
    > * Expand your Stamp I/O: http://www.al-williams.com/awce/pak3.htm
    >
    > >
    Original Message
    > > From: Rus Hardy [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=7KvV6mkFN095Ocq-Qg6F3KAEACfcdPxUq3dsciFDmPIgGb4CoKOl8T9cTx0U6hWZUNcTqVEPjwfMdrgtUvC9]rushardy@m...[/url
    > > Sent: Wednesday, May 02, 2001 12:26 PM
    > > To: Stamp Group
    > > Subject: [noparse][[/noparse]basicstamps] Encasing in resin....
    > >
    > >
    > > Believe it or not this is stamp related......
    > >
    > > For the advanced electronics gang....
    > >
    > > In your opinion....Is there any problem with encasing completed circuits
    > > in polyester resin?
    > >
    > > The final product needs to be tamperproof and very moisture resistant
    > > and it seemed like this could be a very good alternative....
    > >
    > > Any potential problems with components??
    > >
    > > Thanks!!
    > >
    > > Rus
    > >

    --
    Bones
    "Ghoul-Will Ambassador to the Boneyard"
    Atrophies - Ghoulishly Original Awards & Trophies
    http://www.bluedestiny.com/Atrophies/
    SpiderBucky & SpiderThrifty - Boney Superheroes
    http://www.bluedestiny.com/SpiderBucky/
    Keeper of the Bucky-n-Thrifty Flame
    http://www.boneyardbargains.com/
    "my mind wanders....I'm just along for the ride"
  • ArchiverArchiver Posts: 46,084
    edited 2001-05-03 01:58
    it depends on the properties of the resin. you have to be careful if it
    will be subjected to any temperature extremes because the resin will
    expand and shrink and could break components that it seeped into or
    around.
    also, if the resin expands while it solidifies you could have a problem.
    I'd say as long as it has a bit of give you should be ok. just make sure
    to put all your cables through a strain relief inside the resin, so
    there won't be any stress on connections.
    the last thing you need is a bad connection inside there

    Jason

    Rus Hardy wrote:
    >
    > Believe it or not this is stamp related......
    >
    > For the advanced electronics gang....
    >
    > In your opinion....Is there any problem with encasing completed circuits
    > in polyester resin?
    >
    > The final product needs to be tamperproof and very moisture resistant
    > and it seemed like this could be a very good alternative....
    >
    > Any potential problems with components??
    >
    > Thanks!!
    >
    > Rus
    >
    > --
    > Bones
    > "Ghoul-Will Ambassador to the Boneyard"
    > Atrophies - Ghoulishly Original Awards & Trophies
    > http://www.bluedestiny.com/Atrophies/
    > SpiderBucky & SpiderThrifty - Boney Superheroes
    > http://www.bluedestiny.com/SpiderBucky/
    > Keeper of the Bucky-n-Thrifty Flame
    > http://www.boneyardbargains.com/
    > "my mind wanders....I'm just along for the ride"
    >
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

    --
    _______________________________________________
    Jason Lavoie
    jlavoie@e...
    jlavoie@o...
    ICQ#:10604243
    Electrical Engineering III, Carleton University
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