Just a short word here on salvaging parts.
For some parts, the old soldering iron or soldering gun works well. For some parts that have their leads bent over this is alsmost mandatory to free them from the board. The usual precautions apply to avoid burned fingers, etc.
For some boards it is easiest to break the board up and peel the leads free.
For some old chassis TV sets, radios and test equioment, the diagonal cutters serve well for efficiency.
For many of the newer devices you may be salvaging parts from, the newer RHoS solders are often a silver and tin alloy, these require higher temps to get the solder to flow and flux is crucial for a good solder joint due to the high surface tension these solders exhibit. This last detail is one that can be exploited. Using an industrial heat gun will speed up many dismantling chores.
Over the years I had known specialized heat guns had been used in repairs, and I had used a cheap on once for removing paint from a car door. It did not take long for the handle of the heat gun to become uncomfortable. When I had accumulated a fair sized pile with a great deal of parts desirable to salvage, I began the process as I always had with a solder gun because it was fastest to heat, but they have a duty cycle, and that adds time to the process. The pile I had started with, I began by removing the easy to remove electrolytic capacitors, after pulling leads out of 2, I decided to try the heat gun approach again.
I had just recently acquired a heat gun with a burned out element, which is not as bad as it sounds. I had opened it up, oiled the motor out of normal routine, then located the break- turned out there were 2 of them- the gun must have been dropped while hot. No matter of concern. I simply stretched the element slightly so the heating element would overlap the breaks. Usually it is best practice with a heat gun that is in use that the heating element should be switched off and the fan let to run until cool to keep the heating elements in position.
Because the heat can be great enough to melt solder- it can cause grievous bodily harm if you are not careful- or worse cause a fire. Now the overlapped areas of the heating element I could not crimp a collar to in a manner I would have liked, so they were entwined so they would not come apart easily.
Just a quick note: When the solder is molten, if you give the board light tap on something, many of the pushed through parts will fall out. Some will require a little incentive- be quick and use a suitable tool to grasp and gently pull or pry.
Repackaging the heat gun back together was simple enough, it went back together in the manner it came apart and the mica insulation was indexed both to anchor it and to align the assembly.
Most importantly- wear eye protection at all times. A dropped gun can blast very hot air into your eyes and even burn the cornea, but the other more likely event is some dislodged solder coming off the board and landing in your eye- burning the cornea- this is not good. Wear the eye protection.
The initial tests were good with the air window open. I had not tried it at full heat until I dismantled the boards, so it was the perfect time to answer a few questions. The pile took about an hour to get the parts I wanted, the computer motherboard took the most time as it’s solder had the highest silver content. The pile was comprised of an assortment of computer power supplies, test equipment and a computer motherboard.
Needless to say, I was able to salvage the parts I wanted to save, and then some. Normally the time it would have taken for that pile would have been longer than I want to think about, Normally I would do it when tired, so it was not wasting time where I could be doing other things. so this test being done near lunch time, was a time when I would be doing other things- but wanting to answer questions on cost effectiveness- I wanted to be awake, and I also wanted be alert so I would not anything on fire. Nothing burned, I did not get burned, and I estimate in the hour I spent performing the test and developing the learning curve for best techniques that even though I was learning the nuances- it was cost effective.
It was cost effective from the standpoint that for power consumed, plus my investment on the gun and an estimated value of parts amortized over one hour was worthwhile (no excel spreadsheet for those wishing to see the documentation, but I suggest trying it yourself.), versus the power consumed to attempt removal, the power required, etc- the heat gun won by a landslide. If I had wanted to strip the motherboard completely- I could have done so. That is how effective the heat gun is. Some of you reading this may already know that. Some of you may have used it selectively, as had I.
However- in an industrial setting, it might be at best a break even proposition unless mechanization is introduced, but for those considering such a method of deconstruction; as there will be a market for those skills as there IS a demand for those who know how to dismantle in such a manner over in cities in China where their approach to E-Recycling and E-scrap is much different than what is offically practiced in the US and much of the EU; for now it will just need to be one of those “cottage” industries.
The good news for those concerned about the off gassing- the RHoS standards have been in place in general for over a decade, almost 2 decades in fact for some aspects. If you do the work in a well ventillated area- you are fine. If you dismantle the older boards from TV sets, there is some risk of off gassing, but careful attention to what you are doing will minimize that. Modern fire resistant boards that are RHoS compliant do not stink up the house if you do the work over the stove where you have an exhaust fan- although make sure yours vents outside before you do any old boards.
Solders are potentially a concern, but ventillation and good sense minimize that risk. Collecting your solder in a pan, should be a first plan. Artisans in stained glass may find the solder balls you collect off the tin and lead soldered boards to be useful for repairs or new work- so you have a place to “get rid of”/recycle that material that will soon to be difficult to sell.
The newer silver solders can be collected and sold at a metal recycler if you get enough of it, otherwise someone doing copper or brass work (not potable water plumbing) can make use of that solder scrap too, such as for pre tinning.
You do not want to use it in plumbing as some of it may contain antimony, which is no longer accepted as code in some parts of the world. Antimony also crumbles after a while on exposure to air and it’s various constituents- it is one reason so many die cast pieces become brittle or just crumble. It was used in die casting because it would expand upon cooling thus ensuring a nice clean casting. Little solace for those with Saba radios who have had to replace the driving piece on the tuning shaft, or the Radiola owners who have had to replace dials.
So in short- using a heat gun is potentially a sound alternative to salvaging parts “en masse” because many parts you never thought about are now falling off those boards with the parts you were after. It is not a complete solution as the airflow may generate static enough to destroy early CMOS IC’s, and some modern ones too- but it at least gives you a viable option. You do need to have situational awareness about what you are doing as the air flow out is enough to melt plastic even when it is deflected by the board. This is how you avoid starting fires, and how you avoid injuring yourself.
Again- if you choose to try thees things- you do so at your own risk. Avoidable tragedies are often avoided by practicing situational awareness and common sense- these cannot be taught, you develop them yourself or you refine them yourself. Be mindful of the fact other people do not always have either one, and they are dangerous to work around- they are danger to themselves as much as they are a danger to others.
If I were to develop machinery to do this type dismantling in an industrial setting, I would make in a manner of quickly adjustable jaws that clamped the board on the edge, but also had tabs to lock the board from movement in relation to the jaws. I would incorporate 2 vibration mechanisms, one in the vertical- does not take much, a millimeter is enough travel distance in vibration mode. Plus I would have one horizontal- not towards the operator. In short the motion would be along the “Z” axis and “X” axis and the operator would be on the “y” axis. The heat could be from an oven, an oven blast or heat gun. With a protective view shield and remote control of the heat nozzle, plus a means of straightening leads that some systems bend over in manufacturing can be straightened. Such a system could operate continuously.
The ventillation could transfer the exhaust heat back to the work space for cold climates, or just exhausted in hot climate. The bare boards can then be shredded and processed electrochemcially or the conventional incindiary method in use in many countries. It is a far cleaner process than many might think- Since there are precious metals involved, the exhaust is often using the same scrubber technology in use in coal plants in the US and Canada. The collected materials are then electrochemically isolated.
This is not to deny that many boards get burned in open flames in poor countries where a great deal of E-scrap has been sent. No western country can claim innocence on that matter- but that is not something I am going to cover here.