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Repairing a surface mount resistor?


Seshan
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So I broke my phone. Replaced the LCD and it still didn't work, so I figured it must be something on the circuit board. Well I found it, a tiny resistor. One end was broken from the solder and bent up, I pushed it down and it stayed attached, now how do I repair it? I don't have a hot air soldering gun thing. Anyone have some suggestions? Also in case I end up destroying the resistor does anyone know how to tell what kind it is so I can try and get a replacement? I don't know how to tell what these little resistors are.

20100117-mh4fdgwyq8fcnws3r7rkjj8dej.jpg

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So I broke my phone. Replaced the LCD and it still didn't work, so I figured it must be something on the circuit board. Well I found it, a tiny resistor. One end was broken from the solder and bent up, I pushed it down and it stayed attached, now how do I repair it? I don't have a hot air soldering gun thing. Anyone have some suggestions? Also in case I end up destroying the resistor does anyone know how to tell what kind it is so I can try and get a replacement? I don't know how to tell what these little resistors are.

20100117-mh4fdgwyq8fcnws3r7rkjj8dej.jpg

First get a multimeter and check the resistor it may not be bad. Then again it could be a capacitor but more then likely it's a reistor. Unfortunately it looks to be a 0610 in size which is too small to screen print the value on. Usually resistors in this size are black and capacitors are beige/white/brown.

If you've got a decent soldering iron like (weller wtcpt) and a steady hand you may be able to do it by hand. Place that pin in the middle of the SMD to hold it down. Apply heat to the side that is currently attached and get the solder to flow, now wait a second and then apply heat to the other end. It should only take a couple seconds to get the solder to flow. If you apply heat too long you'll end up lifting the trace from the board.

Another option would be to put it in the toaster oven and re-flow the whole board. You can search Google about this. If there's chips on both sides don't do this.

You can get another resistor from digikey but you'll probably end up buying a reel of 100 or more. Search for surplus or samples from a manufacturer.

You may want to hit up the local VoTech or technical college to see if they have an SMD class/lab. Most would have the equipment to do this and maybe offer to give you a quick lesson.

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BIG FAT DISCLAIMER. These comments are coming from an experienced person. I've hand soldered 0610 and up with two soldering irons. I went through a 40HR course to learn how to solder the right way. It's not for the faint of heart, more then likely the chip will end up sticking to the end of your iron and then you're screwed.

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Thanks for the info. After poking around I notice that the other one beside it is also broken, but it appears that the circuit board has multiple layers and that it had broken right down to the next layer, so I don't think I will be able to fix it. I'll see what I can do, but I think it's time for a new phone :(

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Funny I saw this thread. I was reading through some smd solder/desolder/repair tutorials earlier.

check this out. Dunno if it will help since you broke multiple layers but hell, who knows. *actually you surely scored the other layers so yah.. most probably borked, but hey it's a learning experiance!*

http://www.sparkfun.com/commerce/tutorial_...tutorials_id=36

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Well it can be fixed but it'll take more time and skill. What you'd have to do is trace the circuit to a via and solder a wire there. A via is basically a connection through all layers of the board, it looks like a hole to the naked eye. However, looking at the picture it doensn't look like there are any via and that circuit goes from the pad and the other side to the capacitor.

That's probably a 4 layer board with top/bottom populated with components an inner layer for circuit runs and then a ground plane in between the two.

I've fixed 6 layer boards where the FET literally burned a hole through the board. It wasn't pretty. Of course I have full schematics and layer drawings. In the end I had to repair about a dozen circuits and the board ran when I was done. Which was good since it was the last prototype we had.

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