depopulating cell phone boards

[Geo]

that the good thing and bad thing about stannous chloride.given time in an open container,it will oxidize to tin oxide and fall out of solution. the hcl bath can be used (as a bath) over and over until the acid is depleted or so fouled it will not hold more metal.if it is saturated with tin and the PH is still 1 or 2, let it sit undisturbed and the tin will fall out and you can start over again.tin oxide is resistant to attack by hcl and will not dissolve in hcl.

stannous chloride is actually very cheap to prepare your self.just dissolve a known piece of tin metal in hcl and you have your stannous chloride.i use 95/5 tin/antimony solder and dissolve several grams in 30 ml's hcl at a time.if all the metal dissolves,add a little more metal until no more dissolves.keeping a little metallic tin in your SnCl keeps it active longer.

also,be sure to make a gold standard test solution to test your stannous against.its a solution known to contain gold (AuCl) to test your stannous periodically because it does have a shelf and storage life.once the tin converts to oxide,it will not detect metals in solution.

if you process some metal that you suspect contains precious metal and you test and the test is negative,test the stannous with your gold standard test solution to make sure the stannous is active.

 

[damezbullion]

this worries me, i have just purchased some gold testing stounnous from a jewelers already diluted as it seemed expensive to buy, i wish i just bought a peice of tin now lol and i get why cant use you hcl batch for you stannous now ( it will contain more than just tin ) thanks geo, im just waiting on my equipment now , my hydrochloric is out of stock so had to buy 36% but this should be fine right, my auction for the last of my scarp ends in 10 mins, hope i get a bargain

 

[damezbullion]

Dan i lost them i wasnt paying $170 for 50 ceramics and 70 fibre ceramis, they was all low yeilders to maybe o.25 the highest, so i got 2 more chance at some ceramics i think i will go for, one of them has a Pentium pro in it and a amd k5 pluse plus 4 m2 and 4 cyrex 686 not a bad find , at least now i havnt got to bother with fibre cpu, i really didint wanna bother with them

 

[squarecoinman]

Geo I just wanted to let you know that I am enjoying your videos, soon I will try to built a small incinerator
but for now the weather is still to bad ( Denmark we still have snow )

scm

 

[Geo]

thank you squarecoinman. this is such a great forum that i try to help and contribute when i can. i hope you found the videos helpful.

 

[squarecoinman]

thank you squarecoinman. this is such a great forum that i try to help and contribute when i can. i hope you found the videos helpful.

Geo ; I do find the videos helpful , First I did read Hoke and now i am reading the forum post backwards , but the videos help as sometimes it is so much easyer to see things thanks for that

scm

 

[TheGoldFart]

Hi everyone. This will be my first post on this forum. Glad to meet you all.
I am wondering if there is anything inherently wrong with using a kiln with a digital temp controller for this depopulating application. I do glass blowing so I also do have adequate ventilation.
If this would work @ what temperature does the solder melt? I would probably go 20 or so degree higher than that just to make sure the entire kiln is at a consistent melting temp.

 

[squarecoinman]

Hi everyone. This will be my first post on this forum. Glad to meet you all.
I am wondering if there is anything inherently wrong with using a kiln with a digital temp controller for this depopulating application. I do glass blowing so I also do have adequate ventilation.
If this would work @ what temperature does the solder melt? I would probably go 20 or so degree higher than that just to make sure the entire kiln is at a consistent melting temp.

Melting temp for soft solder is between 90 and 450 Celsius. Putting phone boards in your kiln may work, but I would put sand on the floor so I would not get solder in the kiln, and I am not sure if it will be practical to get the boards in and out of the kiln, then of course I would consider how much will it cost me in electricity.

Since you are new here you should take the guided tour ( Find lazersteve, there is a link in his signature ) and you should also read Hoke you can download that for free at the forum ( use search to find it )

scm

 

[Geo]

consider your heat source. in the video, i am using propane to warm the sand which then warms the components on the board. you really dont want the boards to smoke for a couple of different reasons. the first and most important is safety. the boards contains really,really nasty stuff. it is toxic to breath and can be absorbed through the skin. having these organic vapors enclosed is a very dangerous thing to do. as mentioned before, i had a large squirrel cage blower blowing across the sand bath as we worked blowing down wind. the second reason is the vapors can be explosive. if it creates the right fuel/air ratio with the tiniest ignition source, it will explode whether its contained or not. the third and least important but also the most troublesome reason is you dont want the components to be over heated.these tiny pieces are hard enough to deal with without them crumbling into giblets or powder or the plastic parts melting all over everything.

bottom line is, if the board smokes, you have it too hot.

 

[Smack]

GoldFart, don't use the kiln, find a better method like a stove/oven and set it at 400 or a little over.

 

[TheGoldFart]

@Geo - I did try one cell phone board in the kiln before I came back to your response. Based on your suggestions and my experince I just wanted to come back and state that I will not be using it again. I did not smoke the board however I did find that it just doesnt heat the components evenly across the board. I had to put it back in several times to get all the components off. Probably has to do with the fact that the heat source comes from the sides of the kiln and not from the bottom.

@ squarecoinman - just an FYI regarding electricity use. Its really not that bad. I use my kiln at much higher temps to anneal glass at least 8-10 hrs/week and my electric bill is maybe $10 higher a month. Though it would probably be higher with a fabric insulated kiln rather than the brick kiln I use.

*edit* I just remembered I have a barrel style propane turkey smoker in my shed. Im going to see if I can rig it up similar to your sand bath.

 

[Dwsj65]

Kicking up an older thread here, but one of great interest to me. Geo, I just wondered if you videoed the rest of this process? I am such a visual learner, and the videos in this thread were just the thing for me, but then it seemed to die "mid-process". Thanks

 

[Geo]

actually, the entire process was recorded but only a few of the videos made it to my youtube channel. the camera along with the rest of the videos was stolen from my vehicle a couple of weeks after i posted the sand bath video. it is a shame because there are alot of people that follow my channel and it left a big hole in the process chain.

 

[lysdexic]

Thank you Geo I'm looking forward to watching the videos with sound (My daughter borrowed my earbuds and everyone else in the house is asleep right now).

I was just experimenting with something like this. I have some aluminum alloy plates 1/4" thick and about 8x10" in width and length. I used some steel stands and pieces of fire brick to raise one of the aluminum plates high enough to put a propane torch under it to heat it. It worked fairly well but with boards not being truly flat contact with the heat source wasn't as uniform as it would be with sand and temperature control isn't very precise. I was thinking of making a refractory base that housed a recycled electric heating element and making a copper and aluminum tray to mount above the heat source... I guess I need to test sand out first.

I've been removing all of the MLCCs and flat packs before looking to do a final depopulation. I may still mechanically remove the MLCCs first, is that a waste of time? The Antimony in the solder doesn't effect the functioning of the stannous chloride?

My brain is old and brittle and absorbing Hoke and the processes discussed here is going to take me all winter. I am just now ready to reread and reread, search and read, take notes read some more, etc, etc. Acquiring E Scrap, disassembling and sorting is all I am ready to actually do right now. It gives me something to do and time to think. When I'm ready to begin recovery and refining I'll have my material all ready to go. If posting about this before being ready to discuss chemistry is a problem, please say so. Thank you.

 

[Geo]

actually, depopulating boards is the first step when processing Escrap. whether by mechanical means or thermal, you need to have your game plan ready before you start. like many others, i was using a heat gun to depopulate cell boards because while dealing with my own boards i didnt have enough to use a sand bath. it wasnt until i started processing other peoples scrap that i became aware of the need for greater speed. theres only so many you can do in a days time with a heat gun. the sand bath (my particular sand bath) let me do as many as i wanted to or as many as i had in a days time.

an electrical heat source is not enough heat. if you heat the board too slowly, the board has to stay on the heat longer releasing toxic fumes. you want enough heat to melt the solder quickly so you can get the boards on and off the heat as fast as you can.

you mentioned stannous chloride. i would not recommend using solder from electronics to make testing solution. it is too contaminated with all kinds of metals and may throw the test results off.

 

[lysdexic]

Thank you Geo and sorry to be a pest, I was referring to you mentioning making stannous using tin/antimony solder.

stannous chloride is actually very cheap to prepare your self.just dissolve a known piece of tin metal in hcl and you have your stannous chloride.i use 95/5 tin/antimony solder and dissolve several grams in 30 ml's hcl at a time.if all the metal dissolves,add a little more metal until no more dissolves.keeping a little metallic tin in your SnCl keeps it active longer.

I'm not always as clear as I think I am. I can't imagine trying to sort MLCC's out from other microscopic SMD's once they are off the board. Do you process them all (resisters, mlcc's etc) together?

I experienced what you mean about heating too slowly. I tried before my plate came up to temp, it worked once it was hot enough.

Thank you for your time and knowledge.

- Doug

 

[Geo]

hcl does not dissolve antimony.its left as a black powder after the solder dissolves. antimony does not effect the testing of precious metals. i only collect the largest of the MLCC's as trying to separate the tiny ones doesnt seem to be worth the trouble for me but for someone else, it may be totally worth it.

 

[lysdexic]

Thank you again Geo. I'm guessing the antimony not dissolving in HCL is something I should have known about. I have very little scrap to work with at the moment and I'll need enough palladium to make a stock(?) solution, so it's onward with the tedious task of mlcc removal first.

If I may comment on the suggestions of using asbestos or a kayowool fabric. The insulation (refractory type nature) properties of such materials would defeat the purpose of the process. That's why they are used to protect from flame and/or extreme heat.

Hopefully I'll get to test your method before the weather shuts me down completely. I'm shutting up now.

 

[ahmadbayoumi]

Hello Geo,

I read your posts here over and over as I plan to start my 1st attempt to process cell phone PCBs.

It's really helpful .. Thank you very much

But I have a couple of questions here:

1- Do I need to remove the solder mask 1st with Sodium Hydroxide or HCL bath would be enough ?

2- The 2nd step would be directly go for AP or do I need to go for Nitric bath then AP ?

Thanks in advance

 

[steyr223]

Hello Geo,

1- Do I need to remove the solder mask 1st with Sodium Hydroxide or HCL bath would be enough ?
Thanks in advance

From my experiencewwhich is limited
It takes a while for the hcl to remove the solder mask and i have seen the gold come of with the mask if left in to long

2- The 2nd step would be directly go for AP or do I need to go for Nitric bath then AP ?

Anytime you use nitric you would never go straight to AP or you would most likely make AR and dissolve your values

Incinerate after hno3 bath to assure there is no trace of nitric left
Washing is not enough.

I am just pointing out a couple facts and am in no way telling you this is correct or not as i dont do cell phones

Geo will answer the question or someone will that knows more than i

Hope this helps steyr223 rob