Motherboard hazards/what's worth saving

[mwaurelius]

Ok, obviously I'm new. I'd like to thank that other self-proclaimed new guy out there who put that WONDERFUL pdf guide to searching on the the forum.

I'm not to the point of doing anything chemical yet, I'm still reading Hoke's. I'm just trying to get enough useful bits to think about a first batch. I've got some of my own old computers in my storage unit here in the building, but I thought I'd start with a really cheap, old tower I saw on craigslist.

So, I'll start by listing the mistakes I already know I've made.

1) Even if it's only $20, spending ANYTHING on a eMachines branded computer is too much. The thing only had one memory stick, one PCI card (dial-up modem) and I don't think the IDE pins or the PCI socket pins have any gold on them at all - I should see something if it's even gold plated, right?

2) If you're going to use a heat gun (like me), torch, or other heat source besides maybe incineration to desolder a motherboard, first remove all the plastic on the board (I was trying to avoid it with the gun) and also, REMOVE ALL THOSE ELECTROLYTE CAPACITORS!!! Those things are filled with a liquid or semi-liquid electrolyte and will explode when they get hot enough. I thought the first pop, which was kind of small, was maybe one of them discharging which didn't make sense. The second one was much too big to miss for what it was. I didn't have any problems from the explosion itself or the hot material, but I've still got a funny taste in my mouth from whatever-it-was inside the cap which was atomized. By the way, I searched (yes, after the fact) for hazards of motherboard stripping, only got 4 results, and they were not relevant.

Now, what I'd like to know is what is worth keeping as well as how to segregate; also, are there any other landmines I haven't found yet?

I have mechanically stripped out everything, have the base metals from the case, heatsinks, cables and what not which I can take to the scrap yard after I have a large enough pile. I cut the fingers off the memory and PCI cards and put them in a ziploc, the mylars from the keyboard and a few bits of ribbon cable from the drives which look like they have silver plated ends are in another, the drive boards are set aside for the moment, the Celeron CPU is waiting desoldering of the pins before I crush it up. I was working on desoldering the MLCC's, SIP's, DIP's, and quads when the minor explosion side tracked me.

The board has onboard graphics and northbridge chips; I assume the bigger one with the part number which matches the number printed on the board is the graphics, right? Both contain gold? ((edit) Found one of patnor1011's posts, so I think I have the question of does it contain gold answered: yes . . . but. The chips each have a round metallic heat sink on the top which means the gold content will be low. BUT the solder on the back of the board is for MLCC's and the like, not pins, so how do I get the thing off? Hammer?)

There are MLCC's (C) and resistors (R), but what is a J? And do they all contain useful metals or just the MLCC's? I don't see a reasonable way to sort them out once they are off the board. What about the SIP's, DIP's, and small quads? On the HDD board are any of the bigger bits worth keeping? I do know to keep the memory chips themselves.

Before anybody mentions it, yes, I know, don't quit my day job. I'm at the experimentation and learning stage so I'll consider the time spent an investment. Maybe it can turn into a profitable venture some day, but if all I do is break even on a hobby, I'll consider it a win.

Oh, one last note. There is a 1 cm2 quad stuck in a plastic socket. Is it worth keeping and how I go about getting it out of the socket?

 

[PlainsScrapper]

mwaurelius,
1) No other landmines I can think of, just try to have a fan or some kind of ventilation, as the solder that keeps components in place can release toxic fumes once heated.
2) The "J" marking stands for a connector, or a jack. Sometimes, a connector with this marking will have gold or silver- flashed coating.
Only remove the mlcc's but not the surface- mount resistors, as they may contain silver, but also Ruthenium, which is highly toxic and carcinogenic.
3) To separate parts, just have multiple containers to hold the different components in, and to remove small SMD pieces, use a pair of tweezers with an angled tip to pick them up, so you can avoid getting other unwanted pieces. To remove them, just put your heat gun on top of the component, wait a few seconds, and pick the MLCC or chip up with the tweezers.
4) To remove surface mount N/S bridge chips, just put your heat gun directly on the chips, as all the connections are underneath the chip, hidden from view. Move the heat gun in a circular motion, and after a while, it will be easily removable with tweezers.
5) Save ALL your chips, as long as it says "IC", or "U", it is a chip. :!:
6) On the hard drive board, remove the chips and MLCCs, the edge connector for SATA and PATA cables, the gold pins at the back, as well as an oscillator, which have gold traces and silver inside. The oscillators can look like a silver or black rectangle, and be marked with a Y, or sometimes X, letter followed by a number. Oscillators are usually located near the main cable connector, or next to a chip. If you are still unsure, you can always look up"surface mount oscillator" on Google images.
7) To remove a quad IC in a socket, carefully inspect the socket the chip is in. You should find that 2 of the 4 corners are open, and have a diagonal silt. Now, get a precision screwdriver set, and get a slotted screwdriver, and stick it diagonally inside the gap. Push the screwdriver down, and the chip should come right out. if it is still stuck, repeat on the other gap.

Also, look for surface mount LEDs, as they contain 2 to 4 percent of their weight in gold. Very little weight, but it will eventually add up. They CAN be found in modems and motherboards.
I hope that is helpful and useful for you. Have a great day.

 

[patnor1011]

........

The board has onboard graphics and northbridge chips; I assume the bigger one with the part number which matches the number printed on the board is the graphics, right? Both contain gold? ((edit) Found one of patnor1011's posts, so I think I have the question of does it contain gold answered: yes . . . but. The chips each have a round metallic heat sink on the top which means the gold content will be low. BUT the solder on the back of the board is for MLCC's and the like, not pins, so how do I get the thing off? Hammer?)

That is not quite correct statement. Gold content of BGA IC with round metallic piece on top will be pretty much the same as the one without.
I have said that in mixed batches this may distort or lower yield. Lets say that 1 kilogram batch of them with heat sinks will have less pieces than 1 kilogram batch of those without heat sinks. Also, this particular type with round piece of metal visible on top is still better (as that metal is fairly light), than some I encountered while ago which had star shaped piece of heavier and thicker metal inside body of chip - not visible before incineration and crushing.

I believe you meant chip like on picture on my avatar - on the right side.

 

[mwaurelius]

PlainsScrapper:

Thanks for the reply.

It's one day short of a month since I first posted and I have not been wasting time on the reading/learning front. I've made some (more) mistakes, but they've been in the category of tossing when I should have kept rather than chemical disasters - well, except for trying to crush a north bridge chip (black and green parts together) by hand without first incinerating; I have that mess stowed away for later.

I can now identify a lot more of the components and I've started saving those stupid electrolytic caps. According to my reading the electrolyte is not toxic and they are made of aluminum. Eventually it will be worth melting them down. Don't worry, I'll read and test and make sure I know what to expect before I try. When I get to that point, I'll run my plan past the forum to see if I've missed any landmines.

I'm pulling out all the connector, slot, and jumper pins for later recovery. I'm not sure I want to try a sulfuric cell as my first chemical process so I might do those in AP when I have a few pounds - which I know will take a lot more AP than fingers.

Ruthenium, hmmm. I've been heating the drive and slot boards and shaking everything into a big, retired frying pan and then pulling out the chips and oscillators for sorting. Since the heat gun uses forced air and only gets hot enough to melt solder on the high setting, picking out parts one at a time won't really work. I was planning on eventually dissolving the entire mess and dropping out the values one at a time. THIS will take more study. LOTS more study. Since I'm doing everything by hand, I could sort the resistors from the rest, maybe there are buyers for that material. I've seen mention of Ru poisoning, hadn't previously appreciated how common it could be. There is a thread, I think under chemicals, where a member goes through the process of dropping everything one at a time until you are left with salt water which can be poured down the drain.

I can tell you that there are a "lot" - ok, the board I have has 10 - of SMD LED's on the little display board of a fire alarm system. I'm also pretty sure the entire board is gold trace; I'll know after I remover the solder mask.

As for sorting, Polar brand fruit jars are $1 at Wally world and come filled with a delicious snack too. :mrgreen:

patnor1011:

You are correct about the type of chip. I'm glad to hear the yield will be in the better category, but you see what I already did with it. Live and learn.

I did find something VERY interesting on the fire alarm display board I mentioned: chips mounted directly to the board which were under epoxy globs with bond wires - I can see the ends with a loupe. Will post more detail on that elsewhere, as well as what I threw out (and shouldn't have . . . again).

Thanks for the info, thanks for having enough here to keep me reading (and NOT mixing acids prematurely), and thanks for and to the forum.