(Topic ID: 185565)

Best Way to Remove IC Chip on PCB - Williams WPC?

By Elicash

4 years ago


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  • Latest reply 4 years ago by megadeth2600
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    #1 4 years ago

    Hello all, so somehow I fried ULN2803 on the MPU. I adjusted the pop bumpers on my BSD with power off, but could have honestly shorted something before i powered down.

    I have done the research to learn that if Fuse 115 keeps blowing, then I likely shorted said chip and perhaps some of the LM339's. The fuse doesnt blow if i disconnect the driver board from the MPU board, so I understand that to mean the issue(s) is on the MPU.

    I am just a couple steps past 'newb' but have invested in a quality soldering station and de-soldering hand pump, good side cutters, etc. so I want to try to fix this myself (it is a hobby after all, right?).

    I have read alot about carefully removing components so as not to damage 'plated thru holes'. I plan to remove these chips, add a socket, and replace.

    My question - what is best / safest way to do this? Is it better to cut the little legs on the ic chips then desolder? Or should i desolder each hole and try to push the little legs out after all solder has been removed? Anything else to consider on this particular issue?

    #2 4 years ago

    Check out this thread for hints, tips & tricks:

    https://pinside.com/pinball/forum/topic/terrybs-soldering-guide-part-1

    Try any method you wish on your old VCR first before "learning" on your valuable pin's PCB!

    Then you should be able to determine the method that works best for you!

    #3 4 years ago

    Here's where years of arcade collecting come in handy.

    Cut the legs off and discard the old IC.

    Desolder each leg stump individually and clean the through-hole. I always add some solder to the joint when de-soldering so as to create some additional heat bridging, and to add additional mass for the sucker to work against.

    Trying to pull a chip out all at once is a very good way to lift solder pads and traces. Even if it turns out you misdiagnosed the problem, it's not worth saving the cost of a chip to have to run jumper wires or some such kludgey repair.

    Ask me how I learned this...

    #4 4 years ago
    Quoted from Zennmaster:

    Trying to pull a chip out all at once is a very good way to lift solder pads and traces.

    First thing I thought was "how will I know if it was really bad"....

    Quoted from Zennmaster:

    Even if it turns out you misdiagnosed the problem, it's not worth the cost of a chip to have to run jumper wires or some such kludgey repair.

    It's hard to argue with truth.

    #5 4 years ago

    Thanks guys. I am going to cut that little bastard out first. I guess by trying to learn from other people's mistakes has me a little paralyzed to do anything. But I also must know that if i make errors i can learn from them and that is part of the hobby. TerryB's thread has great info too. Going to giver a go.

    #6 4 years ago

    Additional Golden Rule:
    "Any component/surface mounted IC used on on a PCB for a SS pinball game must be properly socketed during replacement after removal in preparation for final repair."

    Do not break this rule, EVER.

    Anyone that states differently has not worked on PCBs to any great extent, and is plain wrong.
    Make sure the trace holes are completely clear, clean, and refluxed if needed in preparation.
    Any trace problems should be corrected before IC socketing.
    Go find and order the IC socket with the correct number of pins, and do not "snip" to make it fit.

    Take your time, and preferably practice on a junk board first, adjusting your skills and knowing the temperature requirements as it sounds like you have never done this before.
    It is more likely you will damage the pads on the traces from overheating and lift them, if you don't practice, leaving a board in worse condition than it originally was overall.

    Best of fortune.

    #7 4 years ago
    Quoted from xTheBlackKnightx:

    Additional Golden Rule:
    "Any component/surface mounted IC used on on a PCB for a SS pinball game must be properly socketed during replacement after removal in preparation for final repair."
    Do not break this rule, EVER.
    Anyone that states differently has not worked on PCBs to any great extent, and is plain wrong.
    Make sure the trace holes are completely clear, clean, and fluxed if needed in preparation.
    Any trace problems should be corrected before IC socketing.
    Go find and order the IC socket with the correct number of pins, and do not "snip" to make it fit.
    Take your time, and preferably practice on a junk board first, adjusting your skills and knowing the temperature requirements as it sounds like you have never done this before.
    It is more likely you will damage the pads on the traces from overheating and lift them, if you don't practice, leaving a board in worse condition than it originally was overall.
    Best of fortune.

    This is definitely among the most golden of golden rules. Sockets are SO cheap and easy, and make future repairs and troubleshooting an absolute breeze.

    Also, since you mentioned temperature, it's worth noting that if in doubt, you're probably safer going hotter than cooler. Counterintuitive? Sure. It's sort of the same principle as trying to cut with a dull knife vs. a sharp one: The dull one is still plenty sharp enough to send you to the ER, but the sharp one is more likely to do what you want it to.

    The hot iron will heat the joint quickly, before the heat travels beyond the area you want heated. A cooler iron will need more time to heat the joint, and in that time heat will travel along traces, leads, etc, and could easily melt something you don't want melted.

    #8 4 years ago
    Quoted from xTheBlackKnightx:

    "Any component/surface mounted IC used on on a PCB for a SS pinball game must be properly socketed during replacement after removal in preparation for final repair."

    Is it possible to socket a transistor? I don't think i have ever seen one.

    #9 4 years ago
    Quoted from Beebl:

    Is it possible to socket a transistor? I don't think i have ever seen one.

    Yes. Same process and principle.
    If a circuit is having continual short circuit issues, and not blowing predrivers, diodes, or resistors, this is a testing and correctional method. They come in different spacings based on requirements.

    1430738229872_sil-3 (resized).jpg

    #10 4 years ago

    Sounds like 700 degrees is ideal temp for pcb work? Good advice Zennmaster about not the dull knife / sharp knife analogy for too little heat. It makes a lot of sense.

    #11 4 years ago
    Quoted from Elicash:

    Sounds like 700 degrees is ideal temp for pcb work? Good advice Zennmaster about not the dull knife / sharp knife analogy for too little heat. It makes a lot of sense.

    The temperature range depends on the solder station type, type of tip used, number of traces in contact, type and size of traces, use or non use of heat sinks for IC protection, and experience. This is why I recommended a junk board so you can find your optimal settings. It will be somewhere between 650-750 F. I am usually around 700-750. Keep in mind you must let the iron properly reheat between use for temp stabilization.

    #12 4 years ago
    Quoted from Elicash:

    Sounds like 700 degrees is ideal temp for pcb work? Good advice Zennmaster about not the dull knife / sharp knife analogy for too little heat. It makes a lot of sense.

    There is no one soldering temperature for board work, the temperature you use is a combination of skill, application, technique, and personal preference. I typically desolder components at 700 degrees, but solder in parts at 650 degrees.

    #13 4 years ago
    Quoted from Elicash:

    Sounds like 700 degrees is ideal temp for pcb work? Good advice Zennmaster about not the dull knife / sharp knife analogy for too little heat. It makes a lot of sense.

    It's a pretty safe place to start, but as Pin_Guy says:

    Quoted from Pin_Guy:

    There is no one soldering temperature for board work, the temperature you use is a combination of skill, application, technique, and personal preference. I typically desolder components at 700 degrees, but solder in parts at 650 degrees.

    I do pretty much everything at 700, and it works for me.

    #14 4 years ago
    Quoted from Elicash:

    Hello all, so somehow I fried ULN2803 on the MPU.

    My question - what is best / safest way to do this? Is it better to cut the little legs on the ic chips then desolder? Or should i desolder each hole and try to push the little legs out after all solder has been removed? Anything else to consider on this particular issue?

    Here's my method. Cut off the chip but leave as much lead as possible. Then reflow the solder for each lead adding a little fresh solder. Using tweezers grap the extra chip lead and reflow/melt the solder again. Using slight pressure pull out the old lead while the solder is melted. Because the solder was already reflowed once this process should be pretty quick reducing the heat exposure to the PCB. Now you can desolder the individual holes. Personally, I desolder the holes with Hakko desolder gun.

    And yes socket the 2803. This chip is a know failure point for WPC MPU. On later versions (WPC95) the chip came socket-ed from the factory.

    Other notes: (1) use good solder. Good solder doesn't require flux. (2) if you have a good solder iron the heat range is 650 to 700. (3) Be carefull using a vacuum pencil to desolder - I find the have more vacuum then my gun and lift traces. Personally, I would use a good solder wick over a vacuum pencil.

    Good luck.

    #15 4 years ago

    Success!

    Thanks to everyone who weighed in. I removed the chip safely. I checked the continuity across both sides of the board and down along the trace paths just to make sure I didnt damage anything. Then I installed the socket. Did the whole thing at 700 degrees. cleaned off any extra flux with isopropyl, inspected my work, and carefully installed the chip into the socket.

    I definitely held my breath when I powered up the game, but everything is back in action.

    A great feeling to fix myself. what a fun hobby.

    #16 4 years ago
    Quoted from xTheBlackKnightx:

    Yes. Same process and principle.
    If a circuit is having continual short circuit issues, and not blowing predrivers, diodes, or resistors, this is a testing and correctional method. They come in different spacings based on requirements.

    Many, many, many years ago when I was younger, I knew everything, and was working on my 2nd or 3rd pin (my first "nightmare" one) I used to scoff at using sockets for transistors while debugging/testing PCBs ... specifically the Williams driver board for "Tri-Zone" ... I think I blew two transistors during debug ... desoldered dead one out, soldered new one in, repeat ... when I put the third one in (the one that was going to fix everything), the coil no longer fired and I was baffled. I remember burning an evening triple checking everything. Turned out I screwed up a trace. Now I use sockets until the repair is finished!!!

    I use a dremmel with a cutting disc to cut out dead ICs ... you have got to be careful, but it gets the job done in a snap once you get the gist of it ... use a mask to prevent breathing in the epoxy dust that flies everywhere the first couple of times you do it, and cut along the top of the IC ... not the sides. After a few tries, you'll only cut the metal and you'll have a lot of consistent area left over to safely extract the IC pins.

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