As one might expect the Might Mouse top is electrically connected to the base plate to support the capacitive touch sense functions of the mouse. This capacitive interface is made with a green flex circuit consisting of 5 conductors. The flex circuit terminates at a 6 terminal connector on the main PCB of the mouse. The scroll and click button is also attached to the top of the mouse and has its own flex circuit connecting it to the main PCB. This flex circuit is gold in color with 8 conductors terminating again at the main PCB.

WARNING: I started taking apart my Mighty Mouse knowing that it may never work again. Do not take apart yours unless you are willing to accept that yours may never work again.

I had hoped the scroll and click button would use a new transducer mechanism and therefore was surprised to learn that the scroll and click button is basically a classic mouse roller ball mechanism protruding through the top of the mouse rather than the bottom. Even so the scroll and click button is interesting in its own right if only for the precision that the manufacturing process must have to produce such a small mechanical device.

I decided not to disassemble the scroll and click button in the hopes of bring my Mighty Mouse back to life. Even so I've gotten a good idea of how the little assembly works. The button, as one might expect, is actually a ball enclosed in a small cage. Nearly half of the ball is exposed when the assembly is handled by itself. However, when the scroll and click button is inserted in the mouse top it seems that only about 30 percent of the ball pokes though. I noticed when handling the assembly out side of the mouse that it felt much more responsive with nearly 50 percent of the ball's radius available to sink into my finger tip. Hopefully Apple will find a way to allow more of this little ball to poke though the top of the mouse in later revisions.

Looking closely at the scroll and click button assembly one can see four rollers. These rollers are what make the mouse so similar to a classic roller ball mouse. However, in a classic roller ball mouse there are two rollers that are in constant contact with ball. These rollers encode the mouse's travel in the X and Y direction. Since the ball is in constant contact with both rollers both X and Y movement can be measured at the same time allowing movement to be recorded in any direction of travel. In the Mighty Mouse's case the four rollers allow the ball to have some travel to give your finger the feeling that you are engaging the ball in one of four directions. I have to assume that these rollers are also rotary encoders of some type allowing the mouse to record your movement. It is not clear if these rollers are optical encoders or use some other mechanism. However, it is possible to get the ball to engage two rollers at the same time. This seems to indicate that vertical, horizontal, and diagonal scrolling should be possible.

One very interesting feature of the scroll button is that it has a very subtle tactile feedback. The feeling is difficult to describe. Unlike a car stereo volume knob or the scroll wheel of a typical mouse that has a very course bump-bump-bump feeling the scroll button feels more like the sensation you get when you run your own finger nail across the ridges in the skin of your finger tips.

The click button in the scroll and click button appears to be a dome switch of some kind. It is not clear if this dome switch is what gives the ball its bounce. Unlike the scrolling feature of the button there is no tactile feedback from the switch potentially leaving nothing but a quick response of the operating system as the only indication that you have pressed the button. But, the Apple engineers were a little more creative than that because the clicking of the scroll button actually involves the primary click button on the PCB. I'll describe more about the user experience later.