Methods of depopulating PCB's

Barren Realms 007

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Scott_Hawley said:
badastro said:
Method 9: Hot acid bath
Remove ferrous materials. Place boards in a bath of straight or diluted muriatic acid in a crock pot. Do not boil and keep it covered. The acid will attack all solder and leave gold and copper intact. The process should be over in less than an hour.

Pro: Method 9 is fast and efficient. It only dissolves the solder leaving behind components, a clean board, and dirty acid solution. Some people crock pot pins anyway...
Con: It can produce acid fumes. Hot acid is dangerous. The spent acid is very toxic. It is difficult of an average person to scale up.

I am interested in using this method to depopulate tons of boards, but what does ths person mean it will be difficult to "scale up?"

On a commerial scale with tons of boards as you have said you have it is not a viable option because of the amount of acid that is required. A way to heat the acid on a large scale. And disposal of the spent acid when this is done is costly. You would be better off finding a commercial buyer for your boards.
 

Claudie

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I like the way each process is spelled out to make it easy to understand.
 

butcher

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Remember you guy's heating the circuit boards that those electrolytic capacitors (the can type) they can explode, remove them first.
 

samuel-a

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butcher said:
Remember you guy's heating the circuit boards that those electrolytic capacitors (the can type) they can explode, remove them first.

Yup

This an important safety note.
Also the yellow/black tantalum cap's tends to pop quite violently...
 

CaptnCaveman

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patnor1011 said:
jevaud said:
Now next will be finding something to dissolve the green film that cover the other trace metals on the board...

not worth, as there is mostly copper and if gold then only traces.



I watched a video on lasersteves site that shows a process of removing solder mask from small board. I was thinking of using Method 5 (sand in a pan on a hot plate) to remove components and then try to remove the solder mask with the method he showed in the video, and then figure out the process to remove the gold traces from the board later(Im a noob learning).

I am disappointed to hear it will mostly be copper under there. Would it still be good for me as a begineer to go thru this whole process to see the results or will I be very disappointed to find that 20 or so motherboards results in no visible product? If boards arent generally worth processing, what do you do with the cleaned off boards patnor..sell them in bulk to someone? I have your guide on how to process black surface mount chips and flatbacks...very appreciated!!
 

patnor1011

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I would not bother with 20 motherboards. If you want to see some powder then try that method on some military grade or at least telecommunications equipment boards. Or some older network cards, soundblaster sound cards. Not many motherboards are gold plated under solder mask.
You have to ask around for price of cleaned boards, they can be sold generally as low grade boards but yes they are still valuable and sell-able for their copper content.
 

glondor

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I just posted this in another thread and then saw this one. Fits right in!

The best way I have found for depopulating is a reciprocating saw like a sawzall. Make a jig for your boards, get a scraper blade for the saw and go to town. I see the blades now are available up to 3 1/2 inches wide. Stuff flies everywhere!!. I just do it in a clean area and sweep up all the stuff after. I use various size sieves to sort it after. Some times I just buzz off certain parts then go after other parts later. With the right jig to hold the board you can spend more time switching boards than cleaning them off it is that fast. Watch out for kickback....Did 130 pounds of ram once in 2 days with just a 1 inch wide broken blade. 8)
 

kjavanb123

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Great post, I am dealing with 50kg worth of boards weekly, so I am curios with that amount, what do you guys think would be the economical methods of depopulating the boards? I read this post but still can't find the optimum methods used by most people.

Regards,
Kevin
 

kjavanb123

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All,

I used a steel sheet topped with some sands, placed the board solders on the sand, heat it up, and in less than 15 mins parts started to come off like a cake. even MCCs come off easily. without disturbing the plastic part of the board. Incredible advise from you all. Thanks
Here are some pics.
board after most of its components removed.jpg
hotplate and a PCI card.jpg

Thanks
Kevin
 

kjavanb123

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All,

After I removed the components off the board that contained PMs, I tested one of them believe is called a PCI socket, and put it in a 50/50 nitric / water solution and turned blue and after few mins the gold foils started to float around. Once the reaction stopped, I decant the blue solution, rinse with water few times till it becomes clear, decant, then dissolve the remain ( gold foils and some brown stuff ) in hcl / cl tablets, and immediately dissolved the gold foil at room temperature, heated it a little bit to get rid of chlorine, and gold dropped by addition of smb.

Tried the same component using hcl and nothing happened.

Regards,
Kevin
 

malfeces

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Oh my god.....so many of my questions answered in one post!!! This forum ROCKS!!! Now I just need to find the thread that has a list a description (pics maybe) of the componants that are worth keeping!!! Thanks Lazersteve!!!!
 

etack

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just about everything but the Al caps have value even the Al caps they can be put in breakage.

lots of threads on this.

old but good lots of link to more threads http://goldrefiningforum.com/phpBB3/viewtopic.php?f=33&t=6148

Eric
 

malfeces

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Just to clarify, Method 7, the one that is not details, is it really incineration? There are many threads that talk about incinerating or "pyrolysis" method used on flatpacks and IC's. What componants become so illegally toxic? I only ask because I want to make sure I know what to avoid and why. Many thanks
 

Geo

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malfeces said:
Just to clarify, Method 7, the one that is not details, is it really incineration? There are many threads that talk about incinerating or "pyrolysis" method used on flatpacks and IC's. What componants become so illegally toxic? I only ask because I want to make sure I know what to avoid and why. Many thanks

all Escrap is considered toxic waste. once the equipment is broken down, it is Escrap. the EPA is lax on enforcing certain codes and strict on others. if you recycle the Escrap, theres little to no problem.if you start digging holes and burying it,big problem. anytime you heat PCB's (printed circuit boards) in the process of reclaiming metals, it releases phenols and other organic compounds that are considered toxic,harmful or cancer causing. if you do this on a small scale, like one or two at a time theres little to no problem.if you pile up a truckload and set it on fire,big problem.

if this is a hobby for you, stay small.if you want to start a business, go big, but be sure to stay within the law because the cost of cleaning up a toxic waste site will cost you everything and more and even put you in jail.
 

malfeces

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Thanks Geo, knowledge IS power. This is just a hobby for me. This will remain small as I simply do not have the time or space to get any bigger and having two kids with special needs I need to keep a day job that has good health bennies. I do recycle everything. All the plastics I get from electronics get crushed and sent to a local single sort recycling facility. All the metals get sold to a almost local scrap yard. And all the other circuit boards were, until recently, going to the scrap yard for 10 cents a lb.... That is kind of my schtick, I place free ads here and there looking for broken computers and electronics and advertise that i specialize in destruction of all personal information on devices like cells, pcs, etc. I also let the people who give me scrap know that less than 2% of what I take in is sent to a landfill. Now a days there is a recycler for just about everything. I think it is very important that we all make out best effort to be environmentally friendly.
Thanks again Geo!
 

cejohnsonsr

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Hello all. I'm rather new to this, but have been doing a lot of study, including how to depopulate boards. I'm pretty sure I'd like to use the sand bath method. I saw a YouTube video of (I think) geo doing this with cell phone boards. Looked like a very efficient process. My question is, how hot do I need the sand bath to be? At what temp does the solder begin to melt? Thanks for any help & thanks so much to lazersteve & a few others who contribute so much here.

Ed
 

Geo

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from wiki : Soft solder is typically thought of when solder or soldering is mentioned, with a typical melting range of 90 to 450 °C (190 to 840 °F). [3] It is commonly used in electronics, plumbing, and assembly of sheet metal parts. Manual soldering uses a soldering iron or soldering gun. Alloys that melt between 180 and 190 °C (360 and 370 °F) are the most commonly used. Soldering performed using alloys with melting point above 450 °C (840 °F) is called 'hard soldering', 'silver soldering', or brazing.

http://en.wikipedia.org/wiki/Solder

my sand bath has a needle valve so i can adjust the heat and "hopefully" get the board hot enough to melt solder but not so hot as to make the board smoke. BE WARNED, even if the board isnt smoking, it is still evolving hazardous vapors that are toxic. in the video, i was demonstrating the bath but normally, i have a large squirrel cage fan blowing across my work.the fan was off because if it had been on, you couldnt hear what i was saying.
 

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