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| Soldering Part 3 |
| Written by David Jackson | |||||
| Tuesday, 01 August 2006 | |||||
Try not to fry it
 Having dealt with the basics of soldering, including your average soldering uses, it's time to move onto some more difficult challenges like soldering with surface mount components. This proves to be useful when you when you need to overclock your Mac and messing with resistors is the only way you're going to get a jump in speed. To help prepare you for that inevitability, I'm going to use my iBook Clamshell 366 and kick it up a notch. If you don't have this iBook model or simply don't want to overclock it, don't worry; what I'm going say here is mostly universal. Below is a list of tools you'll need:
To access the the resistors where we'll be working, you need to remove the battary, optical drive, keyboard, modem, Airport card, display hinges and the EM shield covering the logicboard. This is not as difficult as it sounds, so don't panic. If you would like step by step instructions on how to do this, Ifixit has an excellent guide to get to this point. However, I will remind you that the optical drive covers a screw that helps hold the top cover on, so be sure you eject before you shut down to disassemble. Below shows the screw and a view with the top cover and keyboard off. The Em shields are still in place. The resistors we are looking for are under there. 
Now understand, these resistors are small. So small in fact, if you look at the comma (“,”) on your keyboard, that would be the size of two resistors end to end. The graphic below left represents the resistors as they are seen on the logic board. The rectangular figures are the “pads” and the six sided figures represent the resistors themselves. The top row would be toward the back of the logic board. You will notice the pads in the middle have no label, so if we say solder R7, then you know to solder a resistor from R7 to the center pad. Below right you see the actual resistors, close to the back of the board. We are looking for R7 through 14. 
You can see on the resistor configuration in the chart below it. It covers 300MHz to 666MHz, but understand if you have a 366 iBook don't expect 666MHz. You'll most certainly fry your processor. The column on the left shows the processor speed, current or desired. The next column shows the clock multiplier. The next eight columns show the resistor settings for each speed. Simply find the speed you want to go to in the left column and go to the right to see what resistors need to be where. If the box is black then a resistor is at that location on the board, white is empty, or no resistor is there. 
Having located the resistors on the board, it's time to fire up the iron and grab the solder wick. Solder wick is basically braided copper wire, and with some flux it will “soak up” melted solder like a sponge. The technique is to flux the solder on the board holding the component you need to remove. Flux the piece of solder wick, place the wick on one solder joint and apply the iron to the top of the wick. As the solder melts it will be pulled into the wick. It's important to remove the iron and the wick at the same time, otherwise you will have soldered the wick to the board. After wicking the solder, the resistor will still be stuck to the board by the remaining solder underneath. This is where the tweezers are brought into play. You apply more flux to the resistor. Remember, flux is your friend. Using your tweezers, try to get a grip in the middle of the component. Apply heat to the solder joints on either end, and work the part free. This can be a bit challenging when working with micro sized components. I have found that if I can push the resistor off the “pads” with my iron, I can then pick it up with the tweezers and set it aside. You can see this process below. You'll notice that this isn't the same board as shown above. This is because I tried taking details pictures of the iBook's resistors while I was working, but because of how they're positioned, detailed photographs were very difficult to obtain. Instead, I pulled out some old electronics and demonstrated the same exact process using those. Because the process and not the actual board is what's important, you should still be able to follow along without any problems. 
Clean and then flux the first location, and position the resistor on the pads, (the black side up) and while holding it in place with the tip of your tweezers or perhaps a toothpick, touch the iron to each end for a second. Depending on how hot your iron is, the solder on the pad should melt quickly and bond your resistor in place. Repeat on the other end. After all components are moved, clean the board again with the acetone. Be very careful when moving the resistors. If you drop one on the floor I guarantee you will not find it. As for my over-clocking adventure, I soldered R11, R14, R10 and R8 for 466MHz, a 100 MHz increase. I reassembled the iBook and hit the power; that’s when my old enemy Colonel Panic launched his attack. I disassembled the iBook and started again, this time moving the resistors for 433MHz. kernel panic again. So I tried 400MHz. . . success! Not much of an increase, but hey, it's nice and stable, and every little bit helps. That about covers surface mount soldering. These techniques can be applied to most surface mount components. I wouldn't try to replace a processor this way, but resistors, transistors and diodes are all possibilities. Whatever it is, try not to fry it! So give it a try, and good luck!
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