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potting - hot melt gule and two part epoxy
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 |
potting - hot melt gule and two part epoxy
TenTec used hot melt glue in the VCO modules of the Paragon transceiver, so
this glue probably has good RF characteristics (hopefully). The expansion and contraction of this glue over varying temperatures did cause the solder joints to fracture over the years............this was the downfall of the Paragon. I have used epoxy over the years, with good results. That is the direction I would go. Pete "MarkAren" wrote in message ... 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 |
potting - hot melt gule and two part epoxy
Hot melt glue has a basic problem - it melts when it gets hot. It forever
limits where the stuff can go. They must be kept out of a hot car, and the components cannot get hot. I have used epoxy before and it works fine for all sorts of potting projects. You can color it or get it clear. Rf properties are good. Remember, however, that when you encapsulate something, you trap the heat inside - so the temperature rise of the encapsulated components is greater than free air. Colin K7FM |
potting - hot melt gule and two part epoxy
In message , COLIN LAMB
writes Hot melt glue has a basic problem - it melts when it gets hot. It forever limits where the stuff can go. They must be kept out of a hot car, and the components cannot get hot. I have used epoxy before and it works fine for all sorts of potting projects. You can color it or get it clear. Rf properties are good. Remember, however, that when you encapsulate something, you trap the heat inside - so the temperature rise of the encapsulated components is greater than free air. And don't forget, anything you encapsulate becomes a potential shrapnel bomb. I can vouch for this, having had a near miss with more than one device that had been factory potted in epoxy. Colin K7FM -- Clint Sharp |
potting - hot melt gule and two part epoxy
On Dec 18, 12:28 am, 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 The advantage of hot melt glue is it hardens quickly and even if it leaks out of your mold, will stop when cool. On the other hand, 2 part epoxy potting compound when mixed is about as thin as water and will stay that way for a couple of hours. It will leak from even the smallest crack or hole. We use the 2-part epoxy potting compound in custom milled enclosures for motorcycle control units. The enclosure has two connectors that have to be sealed in with RTV before the potting compound is added. This also occurs to me while thinking about our past potting runs. The hot melt glue will NOT fill all the voids in your unit. Air bubbles will be trapped and will not be able to get out. The epoxy we use takes 24 hours to harden at room temp and this allows time for air bubbles to escape. We have to add more epoxy to each unit for the first 10-15 minutes as air escapes. Hope this helps a little. Paul, KD7HB |
potting - hot melt gule and two part epoxy
|
potting - hot melt gule and two part epoxy
" wrote in message
... This also occurs to me while thinking about our past potting runs. The hot melt glue will NOT fill all the voids in your unit. Air bubbles will be trapped and will not be able to get out. Other than appearance, is there a downside to trapped air bubbles? |
potting - hot melt gule and two part epoxy
MarkAren wrote:
Both of these options seem significantly less expensive than standard epoxy potting compound... Any thoughts ? ====================== Hot melt ,when fluid, might have too high a temperature for the components to be encapsulated. Frank KN6WH / GM0CSZ |
potting - hot melt gule and two part epoxy
Keywords:
In article , PhattyMo wrote: wrote: On Dec 18, 12:28 am, 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 The advantage of hot melt glue is it hardens quickly and even if it leaks out of your mold, will stop when cool. On the other hand, 2 part epoxy potting compound when mixed is about as thin as water and will stay that way for a couple of hours. It will leak from even the smallest crack or hole. We use the 2-part epoxy potting compound in custom milled enclosures for motorcycle control units. The enclosure has two connectors that have to be sealed in with RTV before the potting compound is added. This also occurs to me while thinking about our past potting runs. The hot melt glue will NOT fill all the voids in your unit. Air bubbles will be trapped and will not be able to get out. The epoxy we use takes 24 hours to harden at room temp and this allows time for air bubbles to escape. We have to add more epoxy to each unit for the first 10-15 minutes as air escapes. Hope this helps a little. Paul, KD7HB One other concern a few people expressed when I was looking for "alternative" potting compounds- Most epoxies,etc. contract a bit when they harden/cure. This can (and apparently has,in instances?) "sheared" components from the PCB's they were soldered to. The device might work fine,ya pot it,and it works fine..than the epoxy cures,and it doesn't work anymore because of 'sheared' leads,and cracked solder joints. Just something to be aware of. 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. Another thing to watch out for with two-part materials is that the ones that aren't designed for potting can get very hot when they cure. That's one reason you want a very slow curing cycle. A long time ago I potted a bunch of satellite circuitry in an epoxy filled with hollow glass microspheres to make it light. The thermal conductivity was terrible, so you had to be careful to heat sink anything that might get warm. Doug White |
potting - hot melt gule and two part epoxy
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). The expansion and contraction of this glue over varying temperatures did cause the solder joints to fracture over the years............this was the downfall of the Paragon. ====================== In 1991 I bought a second hand TenTec Paragon trx ....still going strong as my main HF transceiver. But tnx for the above .........if VCO ever fails I know what the reason could be. Frank KN6WH / GM0CSZ |
potting - hot melt gule and two part epoxy
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 |
potting - hot melt gule and two part epoxy
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 |
potting - hot melt gule and two part epoxy
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. |
potting - hot melt gule and two part epoxy
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! |
potting - hot melt gule and two part epoxy
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! |
potting - hot melt gule and two part epoxy
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. |
potting - hot melt gule and two part epoxy
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. |
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