Processors

Computer CPU (central processing unit) manufacturers spend a great deal of time and effort on designing chips specifically for the portable market. In desktop systems, cooling fans housed inside the case dissipate CPU heat. There is no room for this solution in a portable system, so manufacturers have addressed this problem in the packaging of the chip itself.

Chip manufacturer Intel's solution to the size and heat problems is the Tape Carrier Package. This method of packaging reduces the size, power consumption, and heat generated by the chip. A Pentium mounted on a motherboard using Tape Carrier Packaging is much smaller and lighter than the pin grid array (PGA) used in desktop systems. The 49-mm square of the PGA is reduced to 29 mm, the thickness to approximately 1 mm, and the weight from 55 grams to less than 1 gram.

The Tape Carrier Packaging processor is bonded to a piece of polyamide film, which is like photographic film, using tape automated bonding (TAB). This is the same process used to attach electrical connections to LCD panels. The film (called tape) is laminated with copper foil etched to form the leads that connect the processor to the motherboard. When the leads are formed, they are gold-plated to protect them against corrosion, bonded to the processor chip itself, and then the entire assembly is coated with a protective resin.

After being tested, the tape is cut to the proper size and the ends are folded into a "gull wing" shape that allows the leads to be soldered to the motherboard while the processor is suspended slightly above it. A thermally conductive paste is inserted between the processor chip and the motherboard, allowing heat to be dissipated through a sink on the underside of the motherboard, keeping it away from the soldered connections. Of course, because Tape Carrier Packaging processors are soldered to the motherboard, they usually cannot be upgraded.

Some manufacturers use standard PGA processors, sometimes accompanied by fans. In addition to having a greatly reduced battery life, these systems can be too hot to touch comfortably. Always check the exact model of processor that is used in a system you intend to purchase, not just the processing speed. You might not want to purchase a non-Tape Carrier Packaging processor for the aforementioned reasons.