Identifying SMD components - Page 1
Forum section: electronics / beginners

author: HyssSnake
author_rank: Newbie
timestamp: February 21, 2016, 07:48:15 pm
content: I recently obtained several kilos of random electrical components and whilst some had printed information on the packaging most did not.I just wanted to ask the best way to identify some of the tiny components that seem to have come on short strips for a pick and place machine. With a torch, a magnifying glass and my tongue at the right angle I can make out some writing but I couldn't tell the difference between a 0, an O or a D, similarly with 1 or I, or 5 and S.Additionally they seem to just have 3 digit codes with a 1 or 2 digit code vertically printed and i have no idea what they mean.Thank you for your help.Michael

author: Fred27
author_rank: Unknown
timestamp: February 21, 2016, 08:10:03 pm
content: For a start, take one of each tape out so you can read it. Are they 0805/0603/0402 pieces? Generally I've found resistor have a 3 (or 4?) digit code, capacitors are unmarked. You may need to give us a bit more to go on though.

author: Leuams
author_rank: Contributor
timestamp: February 21, 2016, 08:27:32 pm
content: If you have any transistors you may have luck decoding them with a SMD code book or search site. A quick google search gave me the following hit:http://www.marsport.org.uk/smd/mainframe.htmI haven't had much luck identifying SMD transistors.

author: KL27x
author_rank: Super Contributor
timestamp: February 21, 2016, 08:37:59 pm
content: Learn to use the diode test on your DMM.Transistors, you can at least figure out if they ARE trasistors or FETS. And with a scope and a signal generator, you could at least quantify their performance; or with a project, you could find out if they are good enough or not. 3 pin parts can also be diodes. Or voltage regulators. Or voltage detectors. Or.. well, I dunno what else.Anything with four pins, you should maybe at least test to see if it's an optocoupler or an SSR. Optocouplers because they're common. SSR's because they are unreasonably expensive, for some reason. So even if it's a long shot, at least take a crack to see if it's an SSR.Anything with 5-6 pins might be an opamp or a comparator. But good luck with that, since there are several pinouts for those types of parts and testing requires more external components. And dozens of other things they could commonly be.Eight pin IC's I'd at least check for possible FET. They have standard pinout, so easy to test, anyway.

author: HyssSnake
author_rank: Newbie
timestamp: February 21, 2016, 09:44:13 pm
content: Any tips on testing a SOT-23 component with a multimeter, I fear my standard fluke probes are a bit big it keeps escaping when I try to test it. From the sheet Leuams posted it could be a thermistor or a PNP transistor but I can't seem to test well enough to be sure of either.

author: KL27x
author_rank: Super Contributor
timestamp: February 22, 2016, 05:01:04 am
content: Maybe you could solder a sacrificial sample to a piece of stripboard or protoboard for probing and further testing as necessary.

author: JoeN
author_rank: Frequent Contributor
timestamp: February 22, 2016, 06:05:24 am
content: post pics.

author: MSO
author_rank: Contributor
timestamp: February 22, 2016, 07:44:33 am
content: Most of the multi-pin types I've used had pretty good markings. My LCR meter really helps to identify the unmarked two pin SMDs. Even with those unmarked devices I've purchased for a project are double checked just to make sure I grabbed it from the right bin before soldering into place.

author: fra.gherard
author_rank: Contributor
timestamp: February 24, 2016, 07:07:55 pm
content: hithe resistor are simply. 3 digits for 5% and 4 digits for 1%. example: 103= 10000 ohm, 102=1000 ohm, 1002=10000 ohm.if you have 3 digits the third is the number of zero to add at the 2 digits before, if you have 4 digits, the fourth is the number or zero.ceramic capacitors are not marked, tantalum yes.diodes plastic pakage are marked. exampe: T3= bav21wglass package are not marked, they can be zener o normal diodesif you post some foto or marking i can help you, i'm working in a SMD line, so, i know the marking of the components

author: Neilm
author_rank: Super Contributor
timestamp: February 24, 2016, 07:23:58 pm
content: There is also the EIA scheme which is two numbers followed by a letter. The numbers indicate the value, the letter indicates the multiplier. For example a 1k resistor would be 01C.

author: Alex Trofimov
author_rank: Contributor
timestamp: February 25, 2016, 09:00:27 pm
content: I ususally type in google "xxx smd marking", where xxx is the code. If you are uncertain in some characters try every variant. I had pretty decent luck this way)

author: flasonsmts
author_rank: Contributor
timestamp: July 20, 2018, 07:30:09 am
content: Normally the pick and place machine need mark point for each SMD component to identity the position. You said the SMD don't have name on it, I think it''s Can't identify by pick and place machine. The name on the SMD surface not only just a name, it also tell pick and place machine the current direction of the SMD. The solutions for your SMD is to test each SMD direction and print name on it.