# Fire alarm control and display board



## mwaurelius (Feb 15, 2015)

Hey,

A while ago I mentioned posting something about what I found on a fire alarm system. Now that I have full internet access again and can take the pictures from my phone and post them I thought I'd follow up.

Pictured below is the control and display board from an old fire alarm system demo'd out of the building next door and tossed aside. I might post about the main board another time but this control board has the interesting bits. You can see that there are epoxy blobs on the board and, since there is gold plate on the board, I want to remove the solder mask to get at all of it so I was using a heat gun to degrade the epoxy and remove it. I figured there would be small 8-pin chips under the epoxy. What I found under the epoxy was the silicon die itself and I can see the ends of bond wires in the epoxy mass with my 20x loupe. :shock: Sorry, I can't get pictures of that. There are also a number of SMD LED's on the other side which PlainsScrapper told me are 2-4% Au.

What I DON'T have - because I didn't know any better at the time - is the soft composite strips which were wedged between the 1"x 4" LCD. I tossed the LCD after I dropped it and compromised the seal (was that a mistake?) and I also tossed the strips because I couldn't see what their function was and I hadn't removed the epoxy and discovered the bond wires in it. After I knew about the epoxy blobs, I looked closer at where the composite had been on the board and I suspect it too contained bond wires to operate the LCD.

I know it's gone, but am I correct about gold bond wires or would they have been copper?

Mark


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## Smack (Feb 15, 2015)

Don't know about what you tossed, can't see it. LED's will have a small gold bonding wire in them, 2-4% gold by weight? I doubt that. That would be saying 1000 lbs. of led's would yeild 20 lbs. on the low side. Bonding wires will be either gold or aluminum and will be in the black epoxy in the picture above.


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## mwaurelius (Feb 15, 2015)

Smack said:


> Don't know about what you tossed, can't see it. LED's will have a small gold bonding wire in them, 2-4% gold by weight? I doubt that. That would be saying 1000 lbs. of led's would yeild 20 lbs. on the low side. Bonding wires will be either gold or aluminum and will be in the black epoxy in the picture above.


The 2-4% figure is not something I know myself, just a response to my first ever (I should have done more reading first) post. We are talking 2-4% of 10 LED's which I would guess have a combined mass of _maybe_ 2g. We'd be talking milligram range for what is there. PlainsScrapper's point was to sort them separately on those occassions when you find them.

As for the bonding wires, I can tell from looking at the underside of the epoxy that they are gold and not aluminum, the color makes that clear. I'll just pyrolyze it with chips later.


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## patnor1011 (Feb 15, 2015)

mwaurelius said:


> Smack said:
> 
> 
> > Don't know about what you tossed, can't see it. LED's will have a small gold bonding wire in them, 2-4% gold by weight? I doubt that. That would be saying 1000 lbs. of led's would yeild 20 lbs. on the low side. Bonding wires will be either gold or aluminum and will be in the black epoxy in the picture above.
> ...



*incinerate
Probably my mistake in starting and promoting to use this term some time ago.
I doubt if any member here do have hardware capable of pyrolysis.


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## goldsilverpro (Feb 15, 2015)

Bonding wires range from 5.5 - 11 cents per foot = .46 - .92 cents per inch = .11 - .22 cents per 1/4" (1/4" is about the average length per connection). That's about 5 to 10 wires per penny. Is it worth it?


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## Harold_V (Feb 16, 2015)

goldsilverpro said:


> Bonding wires range from 5.5 - 11 cents per foot = .46 - .92 cents per inch = .11 - .22 cents per 1/4" (1/4" is about the average length per connection). That's about 5 to 10 wires per penny. Is it worth it?


Numbers like this are a great example of why much of escrap is best processed in bulk, where minute traces of values are recovered as a matter of routine. Seems incineration and furnace recovery are in keeping with the only logical way to process. 

Harold


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## mwaurelius (Feb 16, 2015)

I'm not thinking there is any great deal of gold on this one board. I found it interesting because I could SEE the bond wires and it was a lot more than eight of them. I've read and seen enough to know recovery is a matter of how much bulk you can get and I did say I would pyrolyze (OK, incinerate) WITH chips later.

By GSP's estimate, the conservative end, the 80-90 wires per chip would be 8-9c per chip, maybe less because I'm not sure the wires are even 1/4" long.

I'm LEARNING. I'm processing by HAND. Some day I'll have a better setup, but right now my main ROI is educational. By doing this I'll know better what to do and look for. I'm still excited by small things. I'm also doing this in motel rooms (I'm an electrician: Have tools, will travel) and my apartment with LITTLE kids. I am seriously constrained in what I can do at this point without endangering others. NO chemistry. Read yes, do no.

Yep, you're right, Harold, best done in bulk. But we start with baby steps. I also collect the chip packages from the Brady label maker cartridges at work and they can't have more than 2-3c per package, but when the cartridge is spent and it only takes me a moment to pry out the package before I toss the cartridge, well . . . why not? I ain't gonna get rich, but it's a cool way to inject some wonder into my jaded life . . . and frittering away my time on this means I'm not out spending.

Isn't learning one of the main aims of the forum? Oh, and thanks for the value estimate on the bonding wires, GSP, very useful.


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## shmandi (Feb 17, 2015)

Smack said:


> Don't know about what you tossed, can't see it. LED's will have a small gold bonding wire in them, 2-4% gold by weight? I doubt that. That would be saying 1000 lbs. of led's would yeild 20 lbs. on the low side. Bonding wires will be either gold or aluminum and will be in the black epoxy in the picture above.



I don't know about 2-4% but some LEDs usually found in cellphones have lot of visible gold. But they are so tiny that you need thousands of them.
Everything in LEDs on photo is plated with gold.


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## kurtak (Feb 17, 2015)

Harold_V said:


> goldsilverpro said:
> 
> 
> > Bonding wires range from 5.5 - 11 cents per foot = .46 - .92 cents per inch = .11 - .22 cents per 1/4" (1/4" is about the average length per connection). That's about 5 to 10 wires per penny. Is it worth it?
> ...



Investing in a couple furnaces to do smelting is one of the best investments I have made - smelting the metals out of ash & then doing the chem work on "metal" is the only way to go in my opinion --- I will never go back to leaching metal from ash & then trying to wash/filter all the leach out

Smelting = far less chem = far less waste

Kurt


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## MarcoP (Feb 17, 2015)

kurtak said:


> Harold_V said:
> 
> 
> > goldsilverpro said:
> ...


I already have 15Kg+ of IC to process, my incineration method is not yet ready and I'm currently working on this and I'm also thinking, ahead, about the separation from the hashes.

Blue bowl. I almost made one, last try and I'm sure I'll come up with a decent home made blue bowl.

Sonicator. Interesting idea, it seems very promising but looks like it doesn't work for everyone. Different working frequency?

Panning. Would take to long for such quantity.

Furnace smelting. Seems the smartest. I've read little, yet, about smelting but it has never been used for incinerated IC chips. Is there any particular reason why incinerated ICs hasn't been smelted?

Marco


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## kurtak (Feb 17, 2015)

MarcoP said:


> Furnace smelting. Seems the smartest. I've read little, yet, about smelting but it has never been used for incinerated IC chips. Is there any particular reason why incinerated ICs hasn't been smelted?
> 
> Marco



Smelting is how I recover the gold (bonding wires) from incinerated IC chips - you still need to concentrate the ash down (panning, blue bowl etc.) which is why I sent the last batch of IC ash off to Mount Baker Mining & Metals https://www.youtube.com/watch?v=tP2_l7SnyVo to run on their shaker table to see how it worked (hope to get one in the near future)

Due to below zero weather here I have not yet done the smelt yet - hopefully in a couple weeks we will see higher temps so I can run the furnace & do the smelt

I have had a few days that I was able to run the furnace since I got the ash back but had to use those days to do work for clients I do work for (so my stuff goes to the back of the line) I hate winter

Kurt


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