Extracting opamps from discarded circuit boards

[ve3wwg]

I have occasionally scrounged parts from discarded circuit boards. I recently was given about four audio mixer boards from a large TV production console, through a friend. This was not only a great source of pots and switches, but also had a bonanza of opamps and other associated chips.

I've traditionally extracted parts like this using a propane torch, applied to the solder side while the PCB is held in a vice on the picnic table. You must do this outside, since it is not only very smelly, but the fumes are very bad for your health.  It probably is a good idea to wear a mask. Be prepared to be stopped by your spouse-- it will attach to your clothes, and you'll need a shower afterwards also.

The propane torch approach works very well at getting parts out, since they'll often just drop out once the solder is melted. However, many parts are hooked in and will require some pulling. Chips usually pull out well, and I have a special little IC puller that hooks under each end of the chip. All of this works very well, except for the smell(!)  It is of course, destructive to the PCB.

To avoid all the spousal hassle associated with the smelly process above, I tried out a different process with the remaining pair of boards (I got through the first two with the propane torch).

In the 2nd process, I used a heat gun on high. This requires considerably more patience, since it takes longer to heat up a chip (or a pot) so that all the solder melts. In fact, you may need to do a little gentle rocking etc. to help it come out.
This heat gun process however, does heat the chips considerably more, since the heat is applied longer until the solder begins to melt. Again, you should do this outside, or at least in a well ventilated place like a garage.

I got a lot of good parts extracted this way. What I didn't know until this morning, was whether or not the extra hot chip extractions were successful or not. I managed to test several TL072, NE5523, NE5534 and a pair of LF412 opamps and happy to report that they all seemed to test ok.

To test them, I bread boarded them in unity buffer configuration, for each opamp. I supplied a signal into the non-inverting input and scoped the output to see if it looked like a good sine wave (that was the input).  Someday, I want to design a generalized opamp tester along these lines and add some other fancy tests so that they can be tested without a scope.

Anyway, the point of this post is simply to say that the heat gun extraction of opamps appears to be a successful approach. The chips do get hot, but they seem to survive it ok.  The trick is simply to get in there, get them out, and let them cool off as best as you can manage it.

I also found that by extracting chips in neighbouring groups is helpful, because they already have the starting heat they need (it saves time, and reduces the stress on the chips being extracted).

I've attached a picture of the dining room table as I was sorting out the parts that were extracted (while the wifey was away).

[dislocations]

Great tips........Cheers

[expanoncolin]

I have also heard of people heating up entire circuit boards with a wide flame from a propane torch, then smacking the board upside down so that the components all pop out.  I have never needed to take out tons of components, so I've always just used a "blade" solder tip with some patience.

-Colin

[ve3wwg]

After I posted here, I ended up finding several youtube videos demonstrating their salvaging skills and techniques. I did find at times, by accident, that many components will just fall out when using the propane torch (and sometimes with the heat gun).

But I think the general success of that really depends upon the way the board was assembled. The boards that I had salvaged, had many components with the leads bent over. This pretty much forced a bit of a pull to get them out. The caps proved enough of a hassle, that I just left them and other small stuff like transistors there (they weren't worth the electricity or the propane to get them out!)

One recommendation I saw somewhere was to use a wood chisel to pry component leads straight before heating them for removal. I think this is a very good idea, which I intend to try out next time. You lay the chisel on it's backside, and bend the lead by moving the chisel handle towards the pcb (thus moving the chisel end up and away from the pcb - bending the lead straight). The chisel end gives you that tiny lever you need to force the issue.

[n.d]

What I do, as i´ve read on Pisotones.com, is to apply a cool moist little rag onto the ICs, so that it doesen´t overheat.

http://www.pisotones.com/Articulos/Chatarreo.htm

[ve3wwg]

That is a good idea for special chips being extracted. Keeping them moist is good. I wouldn't cool them after removal though. I'd rather they cool slowly so as not to crack or stress anything as it shrinks with temperature.

I personally find that the process is already complicated by needing three hands and trying not to burn yourself (when using a torch). Also, if you're doing this outside at the picnic table to avoid fumes (as I often do), you have the added complication of not losing the chips as they fall out. 

I know there are a few op amps loose in my backyard.

[n.d]

I´m about to try out this contraption -for lack of a better word- made of two pieces of wood, with a dinge on their opposite sides, in which you put the edge of the boards, to hold them, thus leaving one of your hands free for grabbing the IC, and/or applying the moist cloth. Way better than a third hand, but it doesen´t mean you can´t use its magnifying glass.

I forgot to mention, also, the rag goes BEFORE and DURING the heating part, not aftewards. Good thing you noticed.

(excuse my english, if any errors)

[ve3wwg]

I find the best device for holding the pcb is a iron bench vise of some sort.  Mine is attached to a bench in my work shed in the backyard. For picnic table removals, I have used clamps to the picnic table but this is not nearly as convenient.

The main trick is to get the pcb clamped so that the edge is facing you, so that each hand has easy access to the top and bottom of the pcb. Being right handed, I like to heat the bottom side with my right hand and remove components with a tool in my left.

Yes- I understood that the moist rag was applied during the removal. For special ICs, this would be very useful. But in my opinion it will be too much of a hassle for most parts. Perhaps a lower hassle way to do this is to spray a light atomized spray of water on the top side prior to component removal.