Wireless connectivity is a critical component of the ThinkPad experience. I can barely remember the last time I connected using a modem, or for that matter an ethenet cable. I'm a total slave to wireless. ThinkPad wireless connectivity takes the concept to a totally new level. Our engineers ensure we have the best radio performance imaginable. At the top edge of every ThinkPad is an array of wireless antennas that boggles the mind. The most critical antenna, from a performance perspective, is the WAN antenna. Performance for WAN must be certified by carriers, who have very stringent connectivity criteria.
So what does this all have to do with design? First it means that the antennas need to be located at the top edge of the display. Having a WAN antenna in the base is a recipe for failing the certification test. Higher is better for any antenna, just look at the roofs of buildings in any city. Additionally, metal, and carbon fiber computer enclosures are the enemy when it comes to radio wave transparency. Both of these materials block the critical radio signals. Manufacturers who use aluminum sheet, milled aluminum, titanium, or carbon fiber must create a sort of radio transparent "window" for the waves to eminate from. This is why you see so many split lines on the top surface of notebook computers. Typically, a narrow band of plastic that is radio friendly is butted to the more exotic material solving the engineering problem. Sadly, it creates an aesthetic design problem that I just can't live with.
Adding such a split line to the top of a ThinkPad is not something I enjoy. The top surface of a ThinkPad was conceived to be the simplest expression possible. A black rectangle with the jaunty angled logo stamped on the corner. I don't want to disturb this impression with a seemingly arbitrary split line. It's kind of like adding a mustache to the Mona Lisa. Would Leonardo da Vinci have painted this masterpiece in two sections and glued them together? I don't think so. So how do we avoid the line on our carbon fiber reinforced ThinkPad covers? It's not easy.
Closeup of the finger-jointed intersection
We invented a way to marry the radio transparent plastic "window" with the carbon fiber cover as a single part. No visible line and superior WAN antenna performance! I love this. The two dissimilar materials are joined during the injection molding process. The technique is commonly called insertion molding. The two materials can be clearly seen from the back side connected using a shape similar to a finger joint. Once painted with our rubberized ThinkPad paint, this irregular line makes it nearly impossible to see any trace of the molded intersection. This also makes the overall cover assembly very strong.
If you want to use exotic materials and avoid the line, you need to go the extra design mile like we do for ThinkPad. As an alternative, I suppose you could just assume people don't need WAN connectivity. If you leave out the antennas, you avoid the problem entirely. For ThinkPad, I don't think so.