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SMD chips

Discussion in 'Electronic Repair' started by [email protected], Jul 1, 2006.

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  1. Guest

    Hi;

    I could use a bit of direction here. I have a RDA9330H to change, small
    44 pin IC. Now I can get this done, just don't drink too much coffee
    before work. Thing is, I saw other chips on the board with only ½ the
    space between the pins and I am wondering how they are changed.

    I have heard of heat guns, we have a magniying glass, but I need more
    of the nuts and bolts of the process. I have changed a few LSI chips,
    but the technique was less then optimal.

    I cut the leads off the chip with a razor. Broke it off the glue, and
    then painstakingly removed the bits so the new chip would seat
    properly.

    After tacking the new IC at opposite corners I flooded the sides with
    solder, then wicked off the excess. This actually worked a bunch of
    times on like the 44 pin QFP (I think) package of the TDA9330H. I
    remember doing a bunch of them in Hitachi built camcorders. The digital
    servo IC lost the phase lock for the capstan, and handled by the freq
    lock alone caused massive wow and flutter. I had three or four of them,
    after they were in top notch mechanical condition, they still had the
    wow and flutter. It had two different pins for the phase and freq lock,
    and they were not integrated exactly the same into the capstan control
    voltage.

    I did those differently, I used a guitar string for removal. I am not
    worried about changing this 44 pin QFP. I am worried about the other
    ICs on the board. Some of them pins got a mighty fine pitch. What do
    you all do ? is it a hot air gun, or are we destined to become board
    jockeys ?

    Just figuring things out, a heat gun would soften the glue. Enough heat
    would melt the solder and you just lift it off. Then, getting the new
    IC aligned wqith some sort of jig, with downward pressure you should be
    able to make it flow.

    Even if this becomes feasible, we are not talking BGA ICs here. On
    those I simply don't know.

    Thanks in advance.

    JURB
     
  2. Arfa Daily

    Arfa Daily Guest

    Hi;

    I could use a bit of direction here. I have a RDA9330H to change, small
    44 pin IC. Now I can get this done, just don't drink too much coffee
    before work. Thing is, I saw other chips on the board with only ½ the
    space between the pins and I am wondering how they are changed.

    I have heard of heat guns, we have a magniying glass, but I need more
    of the nuts and bolts of the process. I have changed a few LSI chips,
    but the technique was less then optimal.

    I cut the leads off the chip with a razor. Broke it off the glue, and
    then painstakingly removed the bits so the new chip would seat
    properly.

    After tacking the new IC at opposite corners I flooded the sides with
    solder, then wicked off the excess. This actually worked a bunch of
    times on like the 44 pin QFP (I think) package of the TDA9330H. I
    remember doing a bunch of them in Hitachi built camcorders. The digital
    servo IC lost the phase lock for the capstan, and handled by the freq
    lock alone caused massive wow and flutter. I had three or four of them,
    after they were in top notch mechanical condition, they still had the
    wow and flutter. It had two different pins for the phase and freq lock,
    and they were not integrated exactly the same into the capstan control
    voltage.

    I did those differently, I used a guitar string for removal. I am not
    worried about changing this 44 pin QFP. I am worried about the other
    ICs on the board. Some of them pins got a mighty fine pitch. What do
    you all do ? is it a hot air gun, or are we destined to become board
    jockeys ?

    Just figuring things out, a heat gun would soften the glue. Enough heat
    would melt the solder and you just lift it off. Then, getting the new
    IC aligned wqith some sort of jig, with downward pressure you should be
    able to make it flow.

    Even if this becomes feasible, we are not talking BGA ICs here. On
    those I simply don't know.

    Thanks in advance.

    JURB

    Friend of mine had the gear to do ICs like those that you mention. It was a
    proper infra red rework station that heated the board from below, as well as
    training hot air I think on the top, so it was able to handle BGAs as well.
    The chip was removed and repositioned by automatic vacuum pen, the board
    being clamped in the base of the station. Everything was monitored by a
    video camera and a microscope. He packed the business in at the end. As far
    as I know, the station is still sitting in his garage, waiting for him to
    get around to eBay-ing it ...

    I too handle the more 'standard' quad packages in a similar way to you,
    using sometimes a very fine wire, and sometimes a shaped bit on the iron
    that can heat all four sides at once. This is a fairly cheap, and very
    practical way of doing it. Refitting is done using liquid flux, and the same
    flooding technique as you. There are solder bits available that have a
    special 'dent' in the end that holds a resevoir of solder that you can just
    stroke along the pins, and just the right amount is capilliaried out onto
    the joints. I haven't personally used one of these, but the same friend with
    the rework station used to. I have a Roebuck long reach stereo microscope
    that I use for the refitting. With a bit of practice, you can adjust to
    soldering whilst looking through it.

    As far as dealing with those very fine pitch LSIs goes, I think that unless
    you are going to do enough of them to make it worth investing in the proper
    kit, it's best to leave it to the manufacturers, and take the practical, if
    less satisfying view, that in those cases, being a board jockey is the only
    way to cut a profit from the job ...

    Arfa
     
  3. ian field

    ian field Guest

    Hi;

    I could use a bit of direction here. I have a RDA9330H to change, small
    44 pin IC. Now I can get this done, just don't drink too much coffee
    before work. Thing is, I saw other chips on the board with only ½ the
    space between the pins and I am wondering how they are changed.

    I have heard of heat guns, we have a magniying glass, but I need more
    of the nuts and bolts of the process. I have changed a few LSI chips,
    but the technique was less then optimal.

    I cut the leads off the chip with a razor. Broke it off the glue, and
    then painstakingly removed the bits so the new chip would seat
    properly.

    After tacking the new IC at opposite corners I flooded the sides with
    solder, then wicked off the excess. This actually worked a bunch of
    times on like the 44 pin QFP (I think) package of the TDA9330H. I
    remember doing a bunch of them in Hitachi built camcorders. The digital
    servo IC lost the phase lock for the capstan, and handled by the freq
    lock alone caused massive wow and flutter. I had three or four of them,
    after they were in top notch mechanical condition, they still had the
    wow and flutter. It had two different pins for the phase and freq lock,
    and they were not integrated exactly the same into the capstan control
    voltage.

    I did those differently, I used a guitar string for removal. I am not
    worried about changing this 44 pin QFP. I am worried about the other
    ICs on the board. Some of them pins got a mighty fine pitch. What do
    you all do ? is it a hot air gun, or are we destined to become board
    jockeys ?

    Just figuring things out, a heat gun would soften the glue. Enough heat
    would melt the solder and you just lift it off. Then, getting the new
    IC aligned wqith some sort of jig, with downward pressure you should be
    able to make it flow.

    Even if this becomes feasible, we are not talking BGA ICs here. On
    those I simply don't know.

    Thanks in advance.

    JURB


    If you don't have all the gear and have to resort to using regular tools,
    the fine pitch SMD chips can be easily removed by shearing the pins off
    close to the chip body with a sharp blade like a Swan & Morton scalpel -
    very great care is required not to score any print tracks under the pins so
    practice on scrap boards until you're sure you can do it right every time!

    The severed pins can be removed by flowing them off with solder, spread some
    new solder along the row of pins and allow to cool so you can upturn the
    board without running molten solder onto other components. By working the
    board from below you can wipe the solder off the pads, the surface tension
    will gather up all the pins, if you work over the wastebasket you can let
    the blob of solder with all the pins in it drop into the bin.

    The pads can be prepared for the new chip with solder wick braid, once you
    have the new chip tacked by a few corner pins flowing a bead of solder along
    the row of pins with the tip of the iron is the best way of not getting into
    a struggle with it. Once all of the pins are flowed the excess solder can be
    stroked off the pins by working upside down again - but even greater care is
    required at this stage to avoid whiskering and getting solder on the pins of
    other chips nearby! Also use plenty of fresh flux and clean with flux
    remover afterwards so you can inspect for bridged pins!
     
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