Replace Propeller chip on Protoboard USB?
poli275
Posts: 6
Hi everyone, we got 2 Propeller Protoboard USB in our laboratory, unfortunately, we destroyed both of them. The entire board looks good, just that it doesn't light up anymore, so we are pretty sure the chip was burned. So I was wondering, is it possible to buy the QFP from Store and attempt to replace the faulty ones in order to revive them? I know it take some skill to replace surface mount components, but considering if spending 8 bucks can revive them I will say it's money well spent. Thanks for any comment or suggestions.
Comments
http://www.chipquik.com/
I don't se problem do that.
Cut carefully pins around it with fine knife else nippers.
Then You can desolder them separately.
Soldering this chip are not so big problem
Cutting the pins is how I did it once, but you have to be very, very careful not to ruin the pads under the pins.
Quickchip might work. Another way I've done it is to put a lot of solder on all the pins. Then, use 2 soldering irons to juggle between all 4 sides to try to get them all liquid at the same time.
Then, at just the right time, push the chip off... That's a bit of a trick though.
I purchased some based on Leon's recommendation and I thought it worked really well.
Cutting the traces as Sapieha suggests is more difficult IMO. While I've successfully removed Props this way, I've also ruined traces on a board by cutting pins (I wasn't careful enough).
If you try Rayman's method of using a lot of solder, I'd suggest adding a square loop of solder wick so there's a continuous circle of solder and wick around the chip. The solder wick helps transfer the heat from one side of the chip to the other. By running your hot iron around the square of solder and wick it's possible to have all four sides of solder melted at the same time and free the chip.
Personally I think ChipQuik is the easiest method. It's pretty cool stuff (I didn't intend the pun). It has a very low melting temperature so it easily stays liquid as you move around the chip with a soldering iron. Thanks for the suggestion Leon.
One advantage ChipQuik has over other methods is its low temperature. I've ruined several PCBs by applying too much heat for too long on a single trace. I don't think the melting point of ChipQuick is high enough to damage PCB traces. (It was probably a hot iron that damaged the board, I doubt the melting point of normal solder is high enough to damage a trace by itself. QK lets you use a cooler soldering iron setting.)
Are you sure it's the Prop that's bad? When you say "it doesn't light up", do you mean the power LED doesn't go on? Is it a USB board with TX and RX LEDs? I've damaged the FTDI chips a couple of times. Could it be a different chip on your board that's bad?
Do the voltage regulators work? I damaged the 3.3V regulator on one of my boards and had to replace it.
As for the issues mentioned by Duane Degn, green led on both boards does not light up when connected to appropriate power source. I tried connecting one of the board to USB and program failed to find any propeller, so I'm pretty sure Prop destroyed. The other I havent tried but should be similar case because my friend can't program it. I cannot be sure if the regulators are blown, I will test them again when I get back to the lab. If the FTDI chip is blown, technically I cannot replace them right?
The green power LED should turn on whether or not the Prop works. This sounds like a power issure. I'd check the regulators and capacitors first. Replacing the Prop wont fix the board.
Technically you could replace the FTDI chip, but I think it's harder to replace than a Prop chip. A USB Proto board could still be used if the FTDI chip has failed by connecting a header for a Prop Plug and soldering the pins to the correct traces on the PCB (I've done this a couple of times).
You want to make sure the regulators are working correctly before you start replacing any of the other chips on the board.
Thanks for your reply! I will double check everything and report back.