Electronics components can be recycled from discarded gadgets. The problem resides in identifying the parts. The passive components might be labeled like the resistors or resistor networks.
Others might not, like capacitors or ferrite beads but you can easily find out the value measuring them. The active devices can be quite difficult to find and sometimes even impossible, for example if you happen to come across a chip with a custom marking code.
Here I’ll show how I do it using a motherboard as an example.
The big parts (SOIC, TSSOP, TQFP, etc.) are relatively easy to find, just Google the marking on the top of the chip. It doesn’t need to be the complete code name; some of the numbers and the package type or the manufacturer could be enough. The board has several of these big chips but the most useful parts would be:
A29040BL: 512K X 8 Bit CMOS 5.0 Volt-only, Uniform Sector Flash Memory
AS324: LOW POWER QUAD OPERATIONAL AMPLIFIERS
74HCT14D: Hex inverting Schmitt trigger
93C46: Atmel, Three-wire Serial EEPROM
RT9214: 5V/12V Synchronous Buck PWM DC/DC Controller
There are a lot of D-PACK devices. This package is intended for high power dissipation so these might be some sort of transistors or diodes. One of them has the code “09NG” and the ON Semiconductors logo. In this case is a well-known company but in case you find some weird logo there are several sites that might help you identify the manufacturer’s name by the logo. So, we have a code, the package and the manufacturer, anything else? Well, yes. The PCB’s silkscreen has the letters S, D and G around the device and this tells you that the part is a FET (Source, Drain and Gate). After googling all that information that part turns out to be a NTD4909, Single N−Channel Power MOSFET (30 V, 41 A).
The other D-PACK has the code “65A3” and the same letters in the silkscreen so it has to be another FET. This one was somewhat tricky to find but eventually I did, is a CEP65A3 N-Channel Enhancement Mode Field Effect Transistor.
There are also a couple of SOT-223 chips. Whenever I’ve found these parts in the past they usually were some sort of voltage regulator and this is not the exception. The silkscreen is a big giveaway, the pins are labeled I, O and A, that is Input, Output and Adjust and the code number correspond to a AZ1117, 1A LOW DROPOUT LINEAR REGULATOR with adjustable output.
Moving on to the smaller devices you’ll see a lot of SOT-23 parts. For this sort of devices there are a couple of sites that will help you to identify them;
In some cases different devices could have the same or very similar codes, that’s where knowing the package or the possible function pays off.
There is one with the marking code “12W” and the silkscreens shows that it is supposed to be a MOSFET. Looking for the code mark in (1) shows that it is a 2N7002 60 V, 300 mA N-channel Trench MOSFET. There is another part that should be a MOSFET and has the marking “L1”, from (1); SI2301BDS P-Channel 2.5 V (G-S) MOSFET.
A couple of devices have the letters E, C y B around them showing that these are bipolar transistors. The markings code are T06 and T04, form (2) these devices are a PMBS3906 PNP and a PMBS3904 NPN general purpose transistor respectively.
Another part has the letters A, K and AK around the pins but I didn’t realized at first was this might means. I looked for the marking code “A7W” in (1) and found out that is a BAV99 High-speed switching diodes. I searched for the datasheet and the letters made sense, it has two diodes inside with the anode of one connected to the cathode of the other forming that “AK” pin.
I couldn’t find one of this SOT-23 parts in neither of the sites with the “EB2” marking. I recognized the logo on top of the package but only because I saw it a just moment earlier while searching for the “bigger parts”. It is not very clear but that’s the logo of Advanced Analog Circuits (I saw it in the AZ1117 datasheet). So, after doing a search with all this information I found the part; it’s an AN431, adjustable precision shunt regulator.
Well, that’s all. This is all the stuff I managed to desoldered.
I leave several parts on the board and destroyed a few in the process, at one point I lost my patience and increased the hot air gun temperature melting some of the plastic parts and damaging a couple of capacitors. The excessive heat increased the capacitor’s inner pressure and a lot of gas came out of the capacitor valve. It might be a good idea to keep your face away from the capacitor pressure valve while desoldering…now I know that.
Hopefully someone will find some of this useful.