Intro: Harvesting Electronic Components
With stores like Radio Shack disappearing, it is getting hard to find simple electronic components. The web, particularly eBay, has been a great help, but shipping can get costly. Consumer electronics, like VCRs and Microwave Ovens can be a source of parts, but consumer electronics tends to very highly integrated. Many parts are special made, or so specialized they are not useful.
Lately, however, the recycling move has produced a wonderful source of high-grade electronics. Check around you area for electronic recycling centers. These businesses take electronic equipment from companies and take responsibility for bring the material into the recycling stream. They typically disassemble the equipment separating the various metals and other valuable contents into various bins for sale to refiners. The circuit boards get thrown into a large container and are usually shredded for reprocessing.
Commercial equipment is built to a much higher standard than consumer electronics. Cost is not so much a factor, and since the volume of production is lower, they tend to use standard components.
One large recycler in Houston charges about $1 a pound for circuit boards, but quite often just gives then to me when I tell them the boards are for our makerspace. Another place I've been to seems to be glad to see the boards go. He has never charged me for a used circuit board.
Step 1: Selecting Boards for the Harvest
Be picky when selecting boards, remember you will need to dispose of the waste properly. It depends on the type of prototyping you will be wanting to do. You may want only through hole components, or maybe you would like to experiment with some surface mount components. I tend to look for board with a lot of analog circuitry. The board above is excellent. It has some digital logic, but it has quite a few high quality op-amps and trim-pots.
Avoid boards that are conformal coated. These boards have a tough coating both front and back and the part are very difficult to remove. Conformal coating is common in surplus military boards
Step 2: Some Tools You Will Need
A metal tray is great for catching the parts as they come off the board. Since we will be using a good bit of heat, a welding glove is good to have. Other holding tools such as small vises, vise-grip pliers. and board holders come in handy. Don't forget eye protection, the wrap-around safety glasses are best.
Finally, you will need a heat source. I use a small butane torch, big torches are too hard to control. Also a high-temperature heat gun works well.
You need anything that works well at grabbing the parts. Needle-nose pliers, IC pullers, slip-joint pliers, and hemostats work well.
Plan to work outside with a light breeze. You will be hitting the circuit board with a lot of heat, so fiberglass will be burning and smoking a bit. Eye protection is a must. Bit of hot solder will be flying about.
Step 3: Getting Started
Examine each board and plan a strategy for the board. Be sure to remove any fasteners that are securing components. Plan to work on the parts that are easiest to remove first. Many straight legged parts fall right out when heat melts the solder. Some components, such as resistors, are crimped on the board before the board is soldered. It's best the leave these behind.
Step 4: Easy Parts First
Heat the board gently and as evenly as possible under the component you wish to remove. Some components will just fall out of the board once the solder melts. I tap the board against the wooden bloc to help jar part loose. Get as many parts off as possible using the heat and tap technique.
Step 5: Smaller Parts Can Be Removed With the Needle Nose Pliers
Try the needle nose first. Clear out the small capacitors near the ICs. Needle nose pliers also work well on the 8-pin DIP packages.
Step 6: Remove the Larger ICs
Slip-joint pliers work well for pulling ICs off. ICs are usually not crimped, but there leads are bent outward to hold then in the board while being soldered. Wiggle the IC and it will come loose, almost like pulling teeth.
Step 7: Give the SMT Parts the Brush-Off
SMT parts can be removed with a small needle nose. Another way that works well is to brush them off the board with a disposable acid brush. Heat the board from the back and keep the brush moving. As soon as the solder melts, the parts will brush off and fall in the tray.
Step 8: Cleaning Off the Board
After a few minutes, you should have almost all the parts off the board and in the pan. Notice I left the resistors. These were all clinched to the board and simply not worth all the effort it would take to remove them.
Step 9: Big Pile of Parts, Now What?
In the photo you see the result of harvesting two circuit boards. Now it's time to sort the parts and look up those you don't know. Thanks to the Internet, finding data on most of these devices will be easy.
Surface mount ICs can be difficult to catalog. SMT resistors are usually marked, but capacitor are not. I use a DER EE DE-5000 LCR meter to test and sort capacitors. It works great and comes with a tweezers type probe for test SMT componets. They are about $140 from eBay and Amazon suppliers.