Sciencemadness Discussion Board - Reclaiming Chemicals from Electronic Components

Reclaiming Chemicals from Electronic Components

99chemicals - 20-8-2012 at 12:56

I have a large stash of circuit boards from everything that I have taken apart in the last 5 years.

I am wondering if there are any usefull chemicals that can be gotten from certain PCB mounted components like resistors, capacitors, MOVs, or other various components.

(I know about palladium from monolithic ceramic caps. That has been discussed and I am not asking about it. I am not asking about gold refining!)

I am wondering what the resistive material in resistors is. I have some large ceramic 5w ceramic resistors pictured below.

I also have a handful of these red capacitors pictured below. Does anybody know what chemicals are inside one of them? I accidently broke one of the leads of one when removing from a board the inside looked metallic. What type of capacitor are these?

Any help would be appreciated.

Rogeryermaw - 20-8-2012 at 14:16

the red caps may be tantalum. it is very commonly used in capacitors and has quite interesting properties.

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

phlogiston - 20-8-2012 at 16:30

Some types of resistors do contain interesting elements, but in tiny quantities.
The following quote is from wikipedia, on thin/thick film resistors:

Quote:

The type of material is also usually different consisting of one or more ceramic (cermet) conductors such as tantalum nitride (TaN), ruthenium oxide (RuO2), lead oxide (PbO), bismuth ruthenate (Bi2Ru2O7), nickel chromium (NiCr), or bismuth iridate (Bi2Ir2O7).

Open one of yours up to see how they are constructed.

Twospoons - 20-8-2012 at 17:49

The resistors: most likely contain Nichrome wire or film, that value could also be carbon film .
The capacitors are not tantalum. They look like a plastic film capacitor, most likely metalised polyester (aluminium and PET).

woelen - 20-8-2012 at 23:59

Tantalum capacitors look different, they have the shape of a raindrop with two little legs. Tantalum capacitors have high capacity for small volume and have low leakage, but they are only available for the lower voltage ratings (at most a few tens of volts, but many of them have a voltage rating less than 10 V).

froot - 21-8-2012 at 01:06

Those resistors are the higher wattage pc board mount type, from my experience they are either resistive wire or carbon film type. I'm not aware of any interesting elements in them.

The caps in the photo look like what we call polypropylene capacitors or 'polyprops'. As mentioned they are a roll of dielectric with a metal film, most likely aluminium film.

Arthur Dent - 21-8-2012 at 04:26

The most interesting components are found on vintage electronics boards. Especially semiconductors! Old diodes, transistors and ICs often have a thicker gold plating than recent semiconductors, Tantalum caps are easy to spot but it's a mess to try to extract the tantalum from them.

It especially applies to computers, the older they are, the more gold there is in them, in particular the processor and the connector edges. A quick visit inside derelict computers can often get you 3 or 4 components that contain most of the precious metals in the whole thing.

More recent components like SMDs can be scraped-off boards with a chisel, then crushed to a fine dust, and chemically dissolved to extract the goodies. I rememeber there was a thread on how to salvage valuable metals from electronic components a while ago.

Robert