desoldering through hole pads to ground, PLCC sockets, fine pitch

Discussion in 'General Electronics Chat' started by relicmarks, Nov 11, 2008.

  1. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    I'm trying to desolder nodes/pads/vias through hole that are tied to ground
    i keep cranking up the heat on the soldering iron and using the solder sucker but its just not working because its a through hole pad tied to grounds.

    how do u guys get solder out of these through holes tied to grounds?

    How do u guys solder PLCC Sockets? and remove PLCC sockets?
    is it with solder paste? because the plastic socket is covering the leads and there is no holes on the other side the PCB to solder the PLCC socket to, so i don't get it

    I need to practice soldering Fine Pitch IC chips , but the Fine pitch IC chips are alittle pricey

    Where can i get a cheat Fine pitch PCB and fine pitch IC chips so i can practice on to get better and faster?

    Desoldering Tool with vacuum pump, how do u guys use these desoldering tools?

    You put the desoldering tool to the node/pad , heat it up and than the vacuum pump is suppost to suck up the solder on SMT or SMD components

    On SMT or SMD components sometimes the pads lift up , What kind of fine wire gauge can i use to Fix the pad to the trace?

    There is SMT op-amps surrounded by molex connects on both sides , i can't get a desoldering tool inbetween cause its a tight fit, and if i use a Hot Air station to remove the SMT op-amps it just Melts alway at the molex connects

    How would u guys remove SMT components in very Tight FIT places?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    For the through holes, use a higher wattage iron and solder wick. You may have to add a bit of solder to the hole before it wicks out. I'm amazed that your solder sucker doesn't get it.

    As far as the op amp goes - can you pull the Molex connectors first? i would want to be very sure the device was bad before going to all that trouble.
     
  3. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    No i can't pull off the molex connectors because there is to many surrounding each IC surfacemount chip

    Ya the solder wick or sucker just won't get the solder out of the through hole
    because the through hole pad is tied to ground so its sucking alot of the heat from it

    Thats why i think u have to use a desoldering station with a vacuum pump to suck these holes out
     
  4. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    I use a hot air station with an "IC Popper" or vacuum suction cups to remove the ICs. You should use a heat-shield to focus the air underneath and to protect surrounding components. Then, I will clean up the pads with flux and solder braid.

    To re-solder, I typically do it manually. For leadless packages, I apply a very slight coat of solder with a wetted-tip, flux it, then apply hot air to the top of the IC at 2" distance. The IC should sink downwards and align itself to the pads.

    Steve
     
  5. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    "IC Popper" or vacuum suction cups to remove the ICs.

    What is this IC popper? ya its hard to find those suction cups tools

    You should use a heat-shield

    Where do u find these heat shields to protect the other PLASTIC components?
     
  6. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    Xytronic 490 IC Popper

    Ya i just use "Filing Clips" and bend them like a IC popper

    Ya its hard to find them you have to order them
     
  7. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    Heat shields :

    I tried using Tin or aluminum foil to act like a heat shield cause its flexible and can fit in tight fits but its still risky

    What would u guys use for Heat shields to protect the plastic parts surrounding SMT parts when using the hot air gun?
     
  8. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    i went to the hardware store and got some really thin sheet metal, so i cut it up to different shapes to put over plastic components to protect them from the HEAT GUN

    I still don't know how to solder a PLCC socket do you guys know ?

    Where to get "magnifying glasses" for fine pitch soldering?

    I went to the local drug stores and hardware stores but they only had reading glasses , i need glasses that are like microscopes
     
  9. EricB

    New Member

    Jul 29, 2008
    2
    0
    Here's an alternative to a microscope.

    If you have a digital camera, or a digital video camera, and a small tripod you can set up the camera as though you are going to take a photo of the work in question. Turning on the macro feature of your camera, if it has one, will help you get close in on your work. Then proceed with your soldering, but instead of looking at the board you look at the screen on the camera.

    This is how I have been soldering smd work, at home, for some time now. At work I have access to a microscope but not at home.

    If you are able to connect your camera to a computer monitor this is a nice way to work. It might seem a little excessive but it is a nice set up.

    Eric
     
  10. mhean_ee

    Member

    Aug 25, 2008
    10
    0
    Use PLCC socket so you will not directly soldered it on your board.
     
  11. Externet

    AAC Fanatic!

    Nov 29, 2005
    763
    57
    In simple words, to clear a tru-hole on heavy heat sink layer, I pull the lead while heating the joint and then drill by hand the remaining solder in the hole with a smaller than hole size bit.
    It works well with me. At my work place they come to me for that 'technique' when others cannot.

    To remove inaccessible joints, destroying the socket/part with cutters frees access, but you need a new socket/part to rework.

    I do have a lipstick video camera (16mm lens) with a ntsc to vga converter to display a ~150X image on a dedicated monitor. Superb! ; allows 10cm clearance for hands and tools while working watching the monitor ----> (attached image)

    Sometimes removing surrounding components is the best way to desolder tight fits.

    Filling with solder fine pitch pin gaps to make a whole blob and heating the blob allows to lift one side of an ic at once.
    Clipping the leads and removing the bad chip works well too.

    A tiny soldering tip is not that convenient, a 3mm chisel tip works well even for tiny pitch leads.

    You can solder a new fine pitch chip by using proper flux and slide surprisingly fast -and gently- the chisel tip.

    A discarded cell phone yields plenty of training opportunities in desoldering.

    I prefer manual vacuum pump to desolder, with a trick: a notch in the tip that fits the soldering tip and keeps vacuum from leaking. It really sucks!

    Some PLCC sockets are meant to have the bottom plastic 'plate' removed for manual soldering

    Lifted pads are better reworked by soldering a wire directly from the pin to the next node, if you do not have tiny teflon wire for the purpose. A single strand of braid is small enough to use.

    Smile, unleaded solder is really trickier.

    Miguel
     
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  12. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    1.) to clear a tru-hole on heavy heat sink layer, I pull the lead while heating the joint and then drill by hand the remaining solder in the hole with a smaller than hole size bit

    Dilling out a thru hole , Won't this mess up the copper plating thur hole ? thats risky

    2.) a lipstick video camera (16mm lens)

    Where do you get these lipstick video camera? and u have a moving stand hookedup to it , how did u go that?

    3.) manual vacuum pump to desolder, with a trick: a notch in the tip that fits the soldering tip and keeps vacuum from leaking.

    How do u make this NOTCH on the tip of the manual vacumm pump?

    4.) PLCC sockets are meant to have the bottom plastic 'plate' removed for manual soldering

    Ya i just pulled on the PLCC socket and it doesn't lift up , and there is NO holes on the other side of the PCB to solder the leads to , its a weird technique
     
  13. Externet

    AAC Fanatic!

    Nov 29, 2005
    763
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    Hello relicmarks.
    Have had no problems with the plating using a drill bit the size of the lead that will be inserted.

    I bought half a dozen of those cameras at Polaris.com and installed at every technician's bench. You MUST tell them you want a lens that will allow magnification to see the image of a dime at least filling the entire screen from 10 cm distance. That allows clearance to work under the lens.
    The movable arm were it is installed is canibalized from a lens/lamp assembly like the white one partially seen retracted on the left of the picture, lens and lamp removed. These clamp to bench edges and stay out of the way until needed. Sometimes available at KMart for desk/drawing table illumination:
    http://g-ec2.images-amazon.com/images/I/31QJTK84FHL.jpg

    A 'halfmoon' shape notch is made with cutter pliers to the teflon tip, allows the iron tip to stay in contact with the melting soldering while hermetically positioning and triggering the sucker.

    See the black sockets in the picture :
    http://www.andonelect.com/secure/ImagesClientUpload/plcc.jpg
    Cut the plastic bottom plate out all around to get access to solder joints. Works great.

    Hope it helps,
    Miguel
     
  14. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    See the black sockets in the picture :
    http://www.andonelect.com/secure/Ima...pload/plcc.jpg
    Cut the plastic bottom plate out all around to get access to solder joints. Works great.

    Yes but than how to SOLDER the new one in ? , because there is not through holes or no pads on the other side of the PCB

    Do you Solder in a PLCC socket ? for each one of them please ? how do u do it ?


    So you Modified a lens/lamp assembly? to fit that Lip stick camera?

    If i take out my lens/lamp assembly , what did you use as a holder/clamp to fit that lip stick camera?
     
  15. Externet

    AAC Fanatic!

    Nov 29, 2005
    763
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    Well, am not familiar with which PLCC carrier socket you are having problem; the ones in the link are the ones that have surface mount pins and am familiar with; their internal plastic 'plate is meant to be held by robot positioning with suction cups; to be removed for manual soldering.
    The other side of the pcb has nothing to do here. The manual soldering is done pin by pin all around.

    Yes, I threw away the lamp/lens to use it as sole camera support with a piece of drilled wood with a screw that fits the camera thread.
    You can see on the top the screw head, the 1/4"? screw goes inside the wood down to the camera holding thread on the bottom. ---> picture attached.

    In some benches I attached the camera to the untouched lens assembly when there was room to do it, without removing anything, leaving illumination+lenses+camera on the movable arm end.

    Miguel
     
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  16. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    which PLCC carrier socket you are having problem; the ones in the link are the ones that have surface mount pins and am familiar with; their internal plastic 'plate is meant to be held by robot positioning with suction cups; to be removed for manual soldering.
    The other side of the pcb has nothing to do here. The manual soldering is done pin by pin all around.

    1.) All kinda of PLCC sockets i have problems with, the ones in the pictures you sent , i have problems with all 3 of them

    2.) So you need a special suction cup tool for this?

    3.) yes i see the pins inside the PLCC socket but my soldering iron would just melt the platic inside the PLCC socket to solder them
     
  17. Externet

    AAC Fanatic!

    Nov 29, 2005
    763
    57
    Hi.
    1) Destroy the socket to pieces with cutting pliers.

    2) No, the robots that place them in manufacturing use suction cups and may handle them attaching to the surface inside. For manual soldering, that bottom surface is discarded.

    3) That is a place to solder with a ~1mm tip iron.

    Miguel
     
  18. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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  19. Externet

    AAC Fanatic!

    Nov 29, 2005
    763
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    If I did not lose your train of thought, apply solder flux to all the pads, remove the bottom plate of the new socket

    http://www.smtnet.com/express/200106/pcb_assembly/plcc-skt-w.jpg

    to gain access to its leads:

    http://www.twyman.org.uk/PCB-Techniques/plcc-skt-wo.jpg

    and solder them one by one by hand. Then insert the chip.

    I do not understand why you wanted to remove the socket; was it damaged, corroded, were the contacts unreliable ?

    In manufacturing, some plcc's that were giving contact problems were soldered direct to the pcb pads with no socket in some cases and unreliability problems vanished.

    http://images.google.com/imgres?imgurl=http://curiousinventor.com/images/guides/smt/plcc_starting_to_solder.jpg&imgrefurl=http://curiousinventor.com/guides/Surface_Mount_Soldering/PLCC&usg=__F96BOUC-h6E_9jfaulbgUze0d-w=&h=207&w=500&sz=36&hl=en&start=15&um=1&tbnid=MhnicjzBSzamnM:&tbnh=54&tbnw=130&prev=/images%3Fq%3Dsoldered%2Bplcc%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26rls%3Dcom.ubuntu:en-US:eek:fficial%26sa%3DN
    Miguel
     
    Last edited: Nov 22, 2008
  20. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    The PLCC socket was broken from using the extraction tool alot of times , thats why it needs replacing

    Using the extraction tool to pull out the IC chip alot of times wears out the socket leads or damages them , thats why i have to replace them alot

    How do u remove the bottom plate of the new socket? do u use a certain tool ? i'm just using a small flat head screw driver and just push on it

    So you use liquid water base clear flux and 1mm tip iron?


    When your soldering Fine pitch IC chips , what kind of solder and iron tip do u use? plus how do you not make solder bridges because the fine pitch IC pins are hair thin very very small and close together

    I try to use very thin solder , liquid water base clear flux and use a hoof tip

    I don't like using Rosin flux cause its very sticky and lifts the pads and its messy

    I don't like No Clean cause its very salty and leaves a white corrision on the
    PCB

    So i just like liquid water base clear flux

    any tips on how to not solder bridge when doing hair thin fine pitch IC chips


    Thanks alot Miguel for the information it means alot to me
     
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