geekhack
geekhack Projects => Making Stuff Together! => Topic started by: alexofthewest on Sun, 22 March 2015, 17:42:15
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in trying to learn to solder and desolder before I mod my poker and das, I took apart a random ten keypad I had and was shocked to learn it was mechanical with cherry browns. I was using a hakko 888d at 750 degrees w/ kester 63/37 and a soldapulit to suck the solder out after heating each one and adding a little solder. I ran into a couple issues that I have questions about.
1-most of my desoldering attempts look a little singed, did I break the pcb with every attempt?
2-Do I have to desolder every switch and those locking plate brackets to remove switches, or can I just desloder 1 switch and pull it out?
3-Related to that, is there a way to do that safely without damaging the pcb?
4-The big metal clips that hold the pcb to the plate are extremely hard to desolder at 750 degrees for some reasons, I managed to get one done, but failed at the other. Any tips?
IMAGES of what I am working on:
top view of the pcb:
http://imgur.com/wuTdk6x
side view of the plate and pcb
http://imgur.com/G8fV0nX
closeup of plate pcb gap 1:
http://imgur.com/AJv8SUj
closeup of gap 2:
http://imgur.com/xHQwD9K
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PCB looks fine. If you're replacing one switch, you can just pull that one switch. The tabs you're talking about are using the plate as a big heat sync, so you'll probably have to keep the heat on longer to get it to let solder melt. Also, that shouldn't have any issues, just be patient.
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1-most of my desoldering attempts look a little singed, did I break the pcb with every attempt?
2-Do I have to desolder every switch and those locking plate brackets to remove switches, or can I just desloder 1 switch and pull it out?
3-Related to that, is there a way to do that safely without damaging the pcb?
4-The big metal clips that hold the pcb to the plate are extremely hard to desolder at 750 degrees for some reasons, I managed to get one done, but failed at the other. Any tips?
1. That's the flux, most likely added when you added some solder (good on you, that's exactly how to do it right) It's just fine.
2. as TJ said, you can pull them out one-by one if you want.
3. What I do is desolder the one switch in question, then get a nylon stick to press in the tabs on the top and bottom, and pull it out from there. I press up on one tab, hold it in place with a fingernail and unclip the other tab, then it pops out.
4. Yes they will be extremely hard to desolder since they are big metal clips they act as a heatsink and have a huge thermal mass. I recommned leaving it as-is if at all possible to avoid PCB damage.
note: some of the switch pins are bent over, You get that sometimes. It's possible to lift it up off the PCB with the soldering iron tip or with a tweezers.
on some of the pads that only have some of the solder removed, put a lot of solder on it and heat it thoroughly, mixing the old and the new: should be very easy to desolder after that.
Poker has plated through holes and is pretty easy to solder and desolder, DAS depends on the generation.
hope this helps.
edit: btw what keypad is that, It's really clean.
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I agree the PCB looks ok. A few scratches won't hurt anything unless they cut the copper traces and the ugly brown stuff will clean off with isopropanol and a stiff brush or some scrubbing with a paper towel.
To expand on dorkvader's comment: anytime I have a lot of components to desolder by hand, espECIALLy if they might have lead-free solder, I take some rosin core solder and glom on a bit of fresh solder on each joint. Even if you are just going to suck the solder off again or clean it right with copper wick, it makes it a lot faster with fresh solder. It helps the initial heat transfer that gets the whole joint heated up. Otherwise, especially with older and lead-free electronics, you might end up rubbing a frustratingly long time at each joint to get the heat flowing.
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Wow thanks a lot you guys. The keypad I believe is a goldtouch keypad with 2 USB ports if I'm not mistaken.
So you said to avoid taking off those heatsink clips, I won't be able to remove the PCB from the plate if I don't. Can you explain the process you mentioned with removing switches without taking the plate off,I didn't understand that process. What is a nylon stick?
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Wow thanks a lot you guys. The keypad I believe is a goldtouch keypad with 2 USB ports if I'm not mistaken.
So you said to avoid taking off those heatsink clips, I won't be able to remove the PCB from the plate if I don't. Can you explain the process you mentioned with removing switches without taking the plate off,I didn't understand that process. What is a nylon stick?
(http://ecx.images-amazon.com/images/I/11D5dXtJvxL.jpg)
Also sometimes called a spudger or "black stick," they can be had online for cheap.
You just use it to press the "tab" on the front of the switch, pull it up a little, then brace it with something (so it doesn't clip back in when you unclip the back one) and push on the "tab" on the back of the switch and lift it out.
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that looks incredibly useful for all sorts of things. thanks!