Chunk Jewel Lamp

Discussion in 'Lost wax casting' started by Jason, Feb 3, 2019.

  1. Peedee

    Peedee Silver

    "I wonder what glue is used for attaching copper foil to printed circuit boards"

    FR4 is made by pressing the copper clading onto the substrate while the epoxy is still 'tacky'. With enough heat you can lift copper tracks. No 'glue' is added, I'm not sure if it's the same with the other subtrates.
     

  2. The brand of FR4 I used to use, Kinsten had some sort of matte finish under the copper that I assumed was glue as it would scrub off with scotchbrite to reveal glossy FR4 underneath. I always thought the copper foil came off a roll and had a glue film applied and rolled/pressed onto the blank fibreglass board. You'd think it would be hard to get a a smooth wrinkle free copper layer if the fibreglass was flexible and wet when it was applied.
     
  3. ddmckee54

    ddmckee54 Silver

    Many-many moons ago, 35-40 years, I worked in a plant where this type of boards were made. I doubt that the basic procedures have changed much, other than getting a lot safer.

    Epoxy glass boards are laid up dry. The glass layers are pre-coated with resin and semi-cured as a continuous sheet in an oven. This continuous sheet is then cut to the desired length. If I remember correctly, this was about 40"x120". These pre-cut resin impregnated sheets are laid up to get the desired board thickness and a layer of copper foil is added to the top of the stack. It took two people to handle the sheets. The stacks are placed in between polished stainless steel sheets and everything is pressed together. Everything is this "book" is dry, there was nothing extra added other than a release agent on the stainless steel plates. The resin/glass combination and pressure/temperature/cooling cycle of the press helps give the board the desired characteristics.

    Don
     
  4. That makes sense, in my ignorance I thought they would be laying the fibreglass cloth with liquid resin. Using a semi solid pre impregnated cloth makes much more sense.
     
  5. Peedee

    Peedee Silver

    Never had a sign of a glue finish in the boards I've etched but not sure with the cheapy eastern paper based stuff. None of which helps regarding getting an agent onto the glass that can be wetted.

    In fact in service I think it could be detrimetal to have a bond. Back to expansion. Loose is good ;)
     
  6. I ran a few experiments this afternoon with a basalt rock found in the backyard: I mixed some one component urethane glue with toluene thinner and powdered graphite and painted it on the rock edges. It wasn't conductive enough to copper plate and I couldn't get a reading with an ohmmeter set to 20 Megohms range. After staring at it for a bit I rubbed the glue-graphite mix with powdered graphite and it was conductive enough to copper plate. The rock surface wasn't exactly smooth to begin with so it only plated wherever the graphite was smoothed over and not in all the pits and valleys. It readily soldered with 40%tin-lead solder that I had lying around (not 60-40 electronics solder) using a 200Watt plumbing iron but if the iron dwelled on a particular spot it completely dissolved the copper plate into the solder.

    So the urethane glue withstood intermittent solder heat for seconds at a time without any damage at all and the solder is adhering to the rock very well in spite of there being graphite under the copper plating. I think a smoother chunk of glass would be easier to plate but the plating thickness be enough to withstand copper dissolving, maybe adding 2% copper into the lead being used a bit like Savbit solder alloys would prevent copper loss.

    rock with graphite 1.jpg urethane with graphite.jpg rock plating 1.jpg rock soldered.jpg
     
  7. Jason

    Jason Gold

    That looks really promising Mark! So do you think the glue is necessary and just circling the the piece isn't enough to have the plating hold on tight?
     
  8. Peedee

    Peedee Silver

    Wow, that is impressive!
     
  9. The second attempt failed: the glue-graphite was fully cured and I rubbed the graphite dust on way too thick so the plating came off easily like crumbly flakes. The first time the glue was still soft and I sparingly rubbed on the graphite dust and the plating was thin. I think smoother glass chunks will be easier to coat but I need to thin out the urethane glue. I picked urethane as it should have cross-linker additives that improve heat resistance.

    A conductive glue looks like the way to go as the plating is very thin and not going to have much mechanical strength, I think even the capillary action of molten lead would pull it off, not to mention dissolving the copper. As it is now, the glue grabs the rock, the graphite rubbed into the soft glue surface sticks to the glue and the copper plates onto the graphite (probably the weak point) and the solder alloys to the copper.

    There was so little graphite rubbed onto the glue that you can see in the first photo that the plating started at the wire and slowly spread over the graphite over twenty minutes or so: it was barely enough to do the job.

    Edit: there's a boat hull anti fouling epoxy based on copper powder: once the epoxy cures, you give it a light sand to expose copper metal grains. So it may be possible to mix copper dust with epoxy resin, give it a sand and solder directly to it without all the graphite and electroplating. It should be substantial enough to avoid dissolving in solder.
     
    Last edited: Aug 18, 2019
  10. Jason

    Jason Gold

    hmm.. wondering if I should I hit up the girls on yt and find out what they are using for graphite? One chick told me she soldiers with low temp soldier and it holds onto whatever graphite paint shes using. She even makes her own plating stuff out of rootkill and battery acid.
     
  11. joe yard

    joe yard Silver

    Would copper foil tape be of any use?
    [​IMG]
    Joe
     
  12. Jason

    Jason Gold

    I might have to go that road Joe if the electro forming doesnt pan out.
     
  13. I'm going to make some copper filings and mix with epoxy and try painting that onto a rock and then give it a sanding to expose raw copper. If that solders, it's going to bypass the plating and graphite steps and go straight to soldering. May not be straight away I have other stuff to do to pay the bills first.
     
  14. Jason

    Jason Gold

    No hurry Mark, pay the bills first.;)
     
  15. Interesting discovery: the unused 24 hour cured glue-graphite mix is now measuring as conductive. I'm trying to plate it.
     
    Jason likes this.
  16. Jason

    Jason Gold

    This dude is a major dork, but he's got some good ideas with this stuff.
     
  17. Jason

    Jason Gold

    Alright.. I'm ordering all the crap now to try this...:oops: The chunky crystal worshipping chick on yt has built up some really fat copper layers on her moon rocks.:rolleyes: I kinda see this as a viable option. At the minimum, I can get all the glass pieces tacked together while I flow lead/tin over the joints. From there I can patina the joints to blend better with the bronze. One thing about this chunk jewel, if it's done wrong, it really sticks out like a sore peepee. :D
     
    Mark's castings likes this.
  18. Peedee

    Peedee Silver

    Huh, did you call.. oh peepee ;)

    Do you need a bond with the glass or is there a way to keep things together mechanically?
     
  19. Jason

    Jason Gold

    lol... not peedee, Peepee.. lol

    I dont think a bond directly to the glass is req'd as much as complete encapsulation of the individual pieces is. When they are locked together in thick lead/tin, they shouldnt fall out or rattle around. Its not like its going down the road I guess.

    Trying to find generals powdered graphite. Something happened to that company and a jar is going as high as 200 on fleabay. WTF?:eek::mad::( I guess the one sitting up there for 35bucks looks like a good deal.:rolleyes:
     
  20. Jason

    Jason Gold

    Off to the turtle races. This is one seriously slow ass process so far.

    20190825_211008.jpg
     

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