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SMD Reference Book

jw0752

Tonight I was researching a circuit board which was populated with many surface mount devices. I decided to try to identify some of the devices using the meager markings supplied coupled with test procedures. Here is the board:

 

image

 

Once I got to searching the internet I came across this publication that really helped me identify many of the components. If you work with SMDs and haven't come across the SMD Code Book before check out this link. I have down loaded it and even though it is 80 pages I have printed it as I related better to paper than computer screens. Not only does it identify semiconductors but also resistors and capacitors. I was able to ID several of the semiconductor devices on the board in just a few minutes.

 

http://www.sphere.bc.ca/download/smd-codebook.pdf

 

John

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  • John,

     

    This is a pretty good list.  Although it is limited, there is a lot of good data here.  I have always wished for a complete list, but alas, some device manufactures do not even list their codes on the specification sheets.

     

    I once had a incorrectly bagged and labeled part delivered from a distributor.  The part had the correct number of pins, so I did not suspect anything, so I mounted it on to the board.  I spent days trying to understand why the circuit was not working, trying several different firmware variations, but nothing worked.  I finally checked the markings and noticed that it did not match.  I contacted the distributor and they sent out the correct part, which of course worked on the first try.  I have always wished that the distributors would mark the bags with the part markings, so you could do a visual inspection prior to assembly (without having to find the code in the specification).  The other issue that I have had, is that the silicon versions are not listed on the labels, nor are they listed on the distributor's websites.

     

    Thanks for posting!

    Gene

  • in reply to genebren

    Hi Gene,

    I doubt that they will be able to bring order to SMD markings. For one thing the technology is changing so fast there is not time nor incentive to put the work in. I was surprised to find a list as complete as this one is. I always learn things when I go exploring. Last night I learned from the list that some of the little 3 leg SOT 23 that I assumed were transistors are actually 1N4148 diodes and the third leg is NC.

    John

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  • in reply to genebren

    Hi Gene,

    I doubt that they will be able to bring order to SMD markings. For one thing the technology is changing so fast there is not time nor incentive to put the work in. I was surprised to find a list as complete as this one is. I always learn things when I go exploring. Last night I learned from the list that some of the little 3 leg SOT 23 that I assumed were transistors are actually 1N4148 diodes and the third leg is NC.

    John

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  • in reply to jw0752

    Hi John,

     

    Interesting that they would put a diode into a 3-pin package, but then again, it does make assembly a little easier as you don't have to worry about orientation.  I always like placing parts with an odd number of leads, as there is one less thing to check.

     

    Gene

  • in reply to jw0752

    Hi John,

     

    Useful document!

    I used to have a sheet with old (e.g. obsolete) manufacturer logo markings for ICs, e.g. Signetics, Ferranti, etc, but I can't find it now. I'll post it if I can locate it.

     

    Regarding SOT-23 diodes a popular one is BAT54, which is a single schottky diode, but also available with three suffixes, which cover all the combinations of two diodes with a common node (e.g. both anodes connected, or both cathodes connected, or anode to cathode connected). Quite handy sometimes. For a single general purpose diode, BAS16 is popular, it is like a SMD alternative for an IN4148 almost (some differences).

  • in reply to shabaz

    Hi Shabaz,

    Yes if you find that sheet of symbols I would be most interested in a copy.

    John