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:
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• Soldering iron with fine tip • Rosin core solder, as fine as you can get • Rosin flux and brush, or a flux pen • A magnifying glass and your glasses if you need them • Tweezers; the smaller the better • Solder wick |
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 we are getting to the location of the resistors. A diagram is seen in the photo below with the resistor settings highlighted. I draw a map of the location of the resistors on the logic board and indicate the specific resistors I need to move to achieve the new setting (I'll explain this further in just a moment). This helps to keep me orientated in the tiny jungle of components on the logic board. The resistors are indicated in the photo below at the back side of the logic board, between the mounts for the display hinges.
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.
The resistors I need to remove are now off the board. At this point I like to take some acetone and clean the burnt flux and general gunk off the board. After you clean up, use your magnifying glass to inspect the area for “solder trails”, globs of solder that shouldn't be there. Wick up anything you find. The pads you just removed resistors from will be solder-free. (For the most part.) So, if you need to connect a resistor to one of them, (usually the center pad) you will need to “tin” it with a small amount of solder. To do this, first flux the pad and then somewhere other than over the board, melt a small amount of solder on the tip of your iron. Then lightly touch the pad with the drop of solder; this should deposit an adequate amount on the pad.
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!
