Author Topic: silver epoxy for microwave frequencies?  (Read 1687 times)

0 Members and 1 Guest are viewing this topic.

Offline CopperConeTopic starter

  • Super Contributor
  • ***
  • Posts: 1415
  • Country: us
  • *knock knock*
silver epoxy for microwave frequencies?
« on: September 06, 2017, 08:27:07 am »
Can you use silver epoxy for very high frequencies, like 20GHz? I was looking to join the center pin of a waveguide antenna SMA adapter to a IC (GaN power amplifier). It seems to be used in RF applications, according to microwave 101, but is it appropriate for direct signal path use? At power levels of >10 watts

I ask this because it is relevant to my other thread, https://www.eevblog.com/forum/rf-microwave/gan-amplifiers-home-implementation/ , but I feel that it deserves its own topic, because it is relevant to RF repair and possibly RF manufacturing.

I have used it before to fix a isolator (only for 1-2 GHz), which had a very unrepairable bent SMA thread. I got a new SMA to waveguide adapter thingy, but getting the center pin to solder in the waveguide was very difficult, it would require a long thin soldering iron and four hands. I'm not sure how they put it together actually, the time constants of the thermal masses appropriate for soldering inside of that thing are tiny... you would need some kind of laser to melt the solder and a mechanical jig to clamp them together... or be a ninja. I have yet to test this repair as it is still curing... but anyway lacking a good VNA or test subject.

I have this product:
http://www.mgchemicals.com/products/adhesives/electrically-conductive-adhesives/silver-conductive-epoxy-slow-cure-high-conductivity-8331s


I considered using hot air, but I noticed if you heat those coaxial connectors too much the dielectric tends to get distorted. Other options also include some kind of special hot air pencil (perhaps heating a needle passing air with a gas torch) and low temperature solder paste...
« Last Edit: September 06, 2017, 08:49:47 am by CopperCone »
 

Offline CopperConeTopic starter

  • Super Contributor
  • ***
  • Posts: 1415
  • Country: us
  • *knock knock*
Re: silver epoxy for microwave frequencies?
« Reply #1 on: September 07, 2017, 08:20:04 am »
the repaired connector on the isolator reads less the 0.001 ohms of DC resistance. I will maybe try to make a piece of hardline with silver epoxy on the connector and see what the before and after is on the spectrum analyzer with a 10GHz signal.

The connection style I made in the repair will be very similar to the connection style I want to make in my amplifier.

It should be noted that this arrangement had some mechanical tension on the center pin of the coaxial connector and the conductor inside of the isolator. I might be measuring that instead of the actual epoxy resistance, but so long the mechanical tension is maintained and the epoxy forms a shell over it, I guess it should be ok.

I would need to make special adapters to properly connect a 6.5 digit meter to the device with a kelvin connection... but I am not really too worried about DC resistance. What I am worried about is the dielectric epoxy 'sponge' that forms around the conductive particles...
« Last Edit: September 07, 2017, 08:29:16 am by CopperCone »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf