Mobile Processor Packaging
The heat that processors generate has been a concern since the first computer chips were released. In desktop systems, the heat problem is addressed to a great extent by computer case manufacturers. Multiple cooling fans and better internal layout designs can keep air
For developers of portable systems, however, not as much can be accomplished with the case arrangement. So, it was up to the chip manufacturers to address the problem in the design and packaging of the chip. Although most portable systems use special mobile processors designed
Some manufacturers of portable systems use standard desktop processors. Apart from a greatly diminished battery life, systems such as these can sometimes be too hot to touch comfortably. For this reason, before purchasing a portable system, you should determine whether it uses a mobile or desktop processor, and understand the
Most mobile processors include a built-in thermal diode that can be used to monitor CPU temperature. The laptop systems use this to control fan operation and also for processor performance control. Utilities are available that can use this sensor to display the processor temperature information onscreen.
Tape Carrier Packaging
An early solution to the size and heat problems for processors was the tape carrier package (TCP), a method of packaging processors for use in portable systems that
Instead of using metal pins inserted into a socket on the motherboard, a TCP processor is
After the leads are
Figure 4.1. Pentium MMX processor in TCP Mobile Package. ( Photograph used by permission of Intel Corporation. )
Reels of TCP chips are loaded into special machines that stamp-solder them directly to the portable system's motherboard. As such, the installation is permanent; a TCP processor can never be removed from the board for repair or upgrade. Because no heat sink or physical container is directly attached to the processor, the motherboard itself becomes the conduit to a heat sink mounted underneath it, thus using the portable system's chassis to pull heat away. Some faster portable systems include thermostatically controlled fans to further aid in heat removal.
Mounting the TCP to the system circuit board requires specific tooling available from all major board assembly equipment
Finally, a hot bar soldering tool connects the leads on the tape to the circuit board. The completed TCP assembly forms an efficient thermal contact directly from the die to the motherboard, enabling the processor to run within its temperature limits even in such a raw state. Eliminating the package and essentially bonding the die directly to the motherboard saves a significant amount of size and weight.
Figure 4.2 shows the pinout of a typical Pentium processor using TCP packaging.
Figure 4.2. Intel Mobile Pentium tape carrier package pinout.
Another form of processor packaging is called the mobile module, or MMO (see Figure 4.3).
Figure 4.3. Mobile Pentium processors in mobile module versus tape carrier package form. (Photograph used by permission of Intel Corporation.)
The mobile module consists of a Pentium or Pentium II processor in its TCP form, mounted on a small daughterboard along with the power supply for the processor's unique voltage requirements, the system's Level 2 cache memory, and the North Bridge part of the motherboard chipset. This is the
Figure 4.4. Intel Pentium mobile module block diagram.
In many ways, the MMO/MMC is similar to the Pentium II Single Edge Cartridge (SEC) design, but with part of the motherboard included.
The module interfaces electrically to its host system via a 3.3V PCI bus, a 3.3V memory bus, and Intel chipset control signals bridging the half of the chipset on the module to the other half of the chipset on the system motherboard. The Intel mobile module also incorporates a single thermal connection that carries all the module's thermal output to the mobile PC's main cooling mechanisms.
The MMO is mounted with
Figure 4.5. Intel Pentium MMX mobile module, including the processor, chipset, and L2 cache. ( Photograph used by permission of Intel Corporation.)
The mobile module greatly
The Mobile Module Connector 1 (MMC-1) is an integrated assembly containing a Mobile Pentium II processor, 256KB or 512KB of L2 cache, a 443BX North Bridge, and a voltage
Figure 4.6. Intel Mobile Module Connector 1 (MMC-1), including the processor/L2 cache, North Bridge chip, and voltage regulator. ( Photograph used by permission of Intel Corporation.)
The MMC-1 also includes a thermal transfer plate that is used for heat sink attachment, and it incorporates thermal sensors for internal and external temperature sensing with programmable trip points.
The Mobile Module Connector 2 (MMC-2) is an integrated assembly containing a Mobile Pentium II or III processor, 256KB or 512KB of L2 cache, a 443BX North Bridge, and a voltage regulator supporting input voltages from 5V to 21V. The MMC-2 has a 66MHz bus speed and was available in Pentium II versions running at speeds of up to 400MHz, or Pentium III versions up to 700MHz.
The MMC-2 also includes a thermal transfer plate that is used for heat sink attachment, and it incorporates thermal sensors for internal and external temperature sensing with programmable trip points (see Figure 4.7).
Figure 4.7. Intel Mobile Module Connector 2 (MMC-2), including the processor/L2 cache, North Bridge chip, and voltage regulator. ( Photograph used by permission of Intel Corporation.)
By including the voltage regulator module (VRM) and North Bridge
Intel used another package for the Pentium II, called the minicartridge. The minicartridge is designed
Figure 4.8. Pentium II minicartridge package. ( Photograph used by permission of Intel Corporation.)
The minicartridge is approximately 51mmx47mm in size and 4.5mm in height. Overall, the package is about one fourth the weight, is one
BGA and PGA
The newest packaging for mobile processors is called micro-BGA (ball grid array) or micro-PGA (pin grid array). These packages are just processors, without any of the other circuits that were integrated into the previous mobile module designs. BGA packaging is unique in that it uses solder balls (instead of pins) on the bottom of the chip. The BGA design is mechanically stable (no pins to bend) and enables better heat transfer from the device to the board. The micro-PGA uses conventional pins instead of solder balls, allowing a standard socketed connection.
BGA chips can either be permanently soldered in or socketed, whereas PGA versions are almost always socketed. Both Intel and AMD use both BGA and PGA form factors for their newest mobile processors.
The micro-BGA2 package consists of a die placed face down on an organic substrate, with an
Figure 4.9 shows a Pentium III processor in the micro-BGA2 package, which contains 495 balls.
Figure 4.9. Pentium III micro-BGA2 package. ( Photograph used by permission of Intel Corporation.)
The micro-PGA2 package consists of a BGA chip mounted to an interposer with small pins. The pins are 1.25mm long and 0.30mm in diameter.
Figure 4.10 shows a Pentium III processor in the micro-PGA2 package, which contains 495 pins.
Figure 4.10. Pentium III micro-PGA2 package. ( Photograph used by permission of Intel Corporation.)
The micro-FCBGA (flip chip ball grid array) package consists of a die placed face down on an organic substrate, with an epoxy material surrounding the die and sealing it to the substrate (see Figure 4.11). The package uses 479 balls, which are 0.78mm in diameter and normally soldered directly to the motherboard. Unlike micro-PGA, micro-FCPGA includes capacitors on the top side of the package.
Figure 4.11. Pentium III micro-FCBGA package. ( Photograph used by permission of Intel Corporation.)
Micro-FCPGA and FCPGA2
The micro-FCPGA (flip chip pin grid array) and micro-FCPGA2 packages consist of a die placed face down on an organic substrate, with an epoxy material surrounding the die and sealing it to the substrate. The micro-FCPGA2 version includes a heat spreader (metal cap) over the top of the die for additional mechanical strength and thermal management. Micro-FCPGA uses 478 pins, which are 2.03mm long and 0.32mm in diameter. Unlike micro-PGA2, micro-FCPGA and micro-FCPGA2 do not use an interposer board and include capacitors on the bottom side. Even though the package has 478 pins, the socket supports 479 pins.
Figure 4.12 shows a Pentium III processor in the micro-FCPGA package. Note that the mobile Celeron, Pentium 4, and Pentium M use the same packaging and look virtually identical.
Figure 4.12. Pentium III micro-FCPGA package (mobile Celeron, Pentium 4, and Pentium M look similar). ( Photograph used by permission of Intel Corporation.)
Mobile versions of the Pentium III, Pentium 4, and Pentium M processor are all available in micro-FCPGA form. Although they plug into the same micro-479 pin socket (shown in Figure 4.13), the different processors are not pin-compatible or interchangeable. In other words, if your system has a Pentium III, you cannot install a Pentium 4 or Pentium M, even though they would physically fit into the same socket.
Figure 4.13. Micro-479 PGA socket for mobile Celeron, Pentium III, Pentium 4, and Pentium M processors in the micro-FCPGA (flip chip pin grid array) package. ( Photograph used by permission of Intel Corporation.)
Virtually all of the more recent mobile processors have been introduced in Micro-FCPGA and Micro-FCBGA packages. The main reason is cost. These are "flip-chip" packages, which means that the raw processor die sits face down on top of the substrate. It is connected directly to the substrate by very tiny solder balls around the perimeter. This is much less expensive than the old PGA form factors, in which the chip die was inserted into a
By comparison, a flip-chip is much simpler, less expensive, easier to assemble, and easier to cool. The die is on the top, so the heat can be transferred directly into the heat sink without having to go through the substrate material. No wire bonding is needed because the tiny solder balls connect the die to the substrate. A