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I made a really stupid mistake at work the other day and ended up blowing up an IC on a one-of-a-kind prototype. :'(
Dying of embarrassment, I decided to try the impossible and replace it before anyone found out what happened. I've soldered surface-mount ICs before, but never any with a PowerPad on the bottom. These are especially tricky to do by hand, since you need to melt the solder under the chip, without making any solder bridges between the pins and the pad. I wasn't sure it was even possible to hand-solder.
(The reason I was able to do this is because there are vias connecting the PowerPad to the other side of the PCB, so that the ground plane on the other side acts as a heatsink. If your design doesn't have these vias, or the holes in the vias are too small for solder to travel through, this method won't work.)
But I was successful! Now no one needs to know my secret shame.
Dying of embarrassment, I decided to try the impossible and replace it before anyone found out what happened. I've soldered surface-mount ICs before, but never any with a PowerPad on the bottom. These are especially tricky to do by hand, since you need to melt the solder under the chip, without making any solder bridges between the pins and the pad. I wasn't sure it was even possible to hand-solder.
(The reason I was able to do this is because there are vias connecting the PowerPad to the other side of the PCB, so that the ground plane on the other side acts as a heatsink. If your design doesn't have these vias, or the holes in the vias are too small for solder to travel through, this method won't work.)
But I was successful! Now no one needs to know my secret shame.
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Signing UpStep 1Remove the old chip
In my case, the old chip was destroyed, so it didn't matter what happened to it. If you want to salvage the old chip, and you don't have a hot-air rework tool, you'll have to figure out something clever and post your own Instructable. That's beyond my skillz.
To remove the busted chip, I first cut all the pins off of it. That way I didn't have to desolder both the pad and the pins at the same time; I could just focus on the pad. I used an exacto knife and pressed it carefully against the pins, one at a time, as close to the chip as possible, until they were all broken off. I ended up cutting into the PCB a little, as you can see in other images, but it didn't harm the layout.
Since the PowerPad-style chips use the PCB as their heatsink, you're supposed to create a bunch of vias right under the IC. This is the key to removing it. If you don't have these vias, I don't know what to tell you. Get a hot-air rework tool, or try to wick solder under the chip from the sides, I guess.
So then I turned my soldering iron up to a higher temperature than normal and held it to the pad/vias on the other side of the board until the solder melted all the way through. The chip came loose and separated from the PCB, and I was then able to get under it to free it the rest of the way.
To remove the busted chip, I first cut all the pins off of it. That way I didn't have to desolder both the pad and the pins at the same time; I could just focus on the pad. I used an exacto knife and pressed it carefully against the pins, one at a time, as close to the chip as possible, until they were all broken off. I ended up cutting into the PCB a little, as you can see in other images, but it didn't harm the layout.
Since the PowerPad-style chips use the PCB as their heatsink, you're supposed to create a bunch of vias right under the IC. This is the key to removing it. If you don't have these vias, I don't know what to tell you. Get a hot-air rework tool, or try to wick solder under the chip from the sides, I guess.
So then I turned my soldering iron up to a higher temperature than normal and held it to the pad/vias on the other side of the board until the solder melted all the way through. The chip came loose and separated from the PCB, and I was then able to get under it to free it the rest of the way.
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The one thing that I do slightly differently is tin the pad on the first pin before soldering it down. That way I get it perfectly in can get it perfectly in place and solder it down at the same time.
Just use plenty of flux and it will probably be fine. Then put a knuckle on the chip and run full power through it. If it gets so hot you can't touch it, then there isn't enough solder. Either that or it needs a heat sink.
Also, taking pictures when disassembling complicated equipment helps later if you don`t know where some part goes.
The spring loaded one? I've never had a problem with damage or dust. It's all sealed and after I'm done with one project I open it and dump everything out. To each his own I guess.
I also forgot to mention that if you heat the solder wick too muchit with pull the coating off the PCB then the whole thing will short. Ifyou're going to solder wick that much stuff you cannot move the wickaround on the board. You have wick and lift straight up
if this happens to you, do yourself a favor and buy a hot air station. you can get them cheap all over. it's the right way to do this. your hair (or lack thereof) looks good on you.
that's a nice comment, and instructive. yay!
*sigh*
yeah, I just tried to explain the problems without using words like "cringe" and I just can't do it. I belive in honesty and treating people like adults - especially if they're resoldering ICs. But if instructables want to treat their users like kindergardeners, then that's their perogative.