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The Laptop Repair Workbook

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Copyright 2010 by Morris Rosenthal

All Rights Reserved

Replace or Upgrade Laptop CPU - Surface Mount vs Socketed CPU

Copyright 2010 by Morris Rosenthal -All Rights Reserved contact info

The printable eBook version of The Laptop Repair Workbook is now available for download anywhere in the world.
Upgrading a laptop CPU rarely makes sense and is often impossible. Laptops are engineered products, with limited clearance and few exchangeable parts. If your laptop CPU works, but you think the laptop is slow, add memory or defrag the hard drive. Even if the CPU is socketed rather than surface mounted (soldered to the motherboard) there will be a very limited range of choices for upgrades, if any at all are available. The upgrade CPU must be explicitly supported by the motherboard or you're wasting your time, not to mention potentially damaging the motherboard. Even if it's possible to install a CPU that's 20% faster, it won't make your laptop 20% faster, and in most applications, you probably won't see any noticeable increase in performance at all. Laptop CPU with active heatsink fan
Removing heatsing from laptop CPU The CPU heatsink in a laptop is just as critical as the CPU itself. Every time you hear the fan come on, it's trying to cool the heatsink metal, which in turn conducts heat away from the CPU. There are nearly an infinite number of designs for heatsinks, but laptops offer a special challenge because the heatsink has to fit in a tight space and promote airflow through the cooling fins. The active heatsink I'm removing above and which is shown to the left is an integrated unit, where the fan is part of the heatsink structure. You can see the vent to the outside right above the CPU, which is covered with a white and blue thermal pad.

To the right, I've stripped the thermal pad off the CPU, and you can clearly see that this Toshiba has a surface mounted CPU. There's no space between the substrate and the motherboard for pins, it's a BGA (Ball Grid Array). Some super ambitious do-it-yourselfers might try to desolder the CPU with a hot air gun, and it might work to remove it, but I wouldn't give good odds for getting a replacement CPU to operate with hot air soldering. Surface mounting the CPU saves the laptop manufacturer money and time in production. The main reason for socketing laptop CPU's is probably to allow for last-minute changes in market targeting as CPU prices come down and the competition heats up. Surface mounted cpu is soldered to motherboard
Heatsink with copper conductor and dual exterior fans The copper pipe and radiator arrangement in the Dell to the left is cooled by dual fans in direct communication with the outside air. The copper pipe is a heat conductor, not an air transfer mechanism. Copper is a terrific heat conductor and efficiently transfers heat over short distances. The end of the pipe is flattened out and attached to the thick metal plated that contacts the CPU. To the bottom left, I'm prying up the spring loaded retainer for the heatsink, and right below, the the screwdriver is in the slotted release mechanism for the CPU socket. Once the spring is released, the cover holding the heatsink in place lifts right up. The heavy heatsink plate is aligned and held from shifting by two metal pins through the motherboard.
Opening CPU retention mechanism for heatsink and processor Heatsink connection with metal plate and copper tube
So the CPU in this Dell can be replaced if it's fried, but you'd have to do your homework for the model family to determine if it can upgraded to a slightly faster unit. All CPU packages come labeled with a little arrow that aligns with the proper corner of the socket (below). They are also keyed with a missing pin, so it's usually impossible to insert a CPU wrong unless you use brute force and bend a pin. The prize for using force is that the CPU will fry. Laptop manufacturers use different methods for thermally connecting the CPU with the heatsink, where DIY types exclusively use thermal paste. If the CPU appears to be coated or blanketed with a permanent thermal substance, I would advise slathering on a new compound unless the CPU arrives with upgrade instructions that instruct you to use thermal paste. Below right you see the field of pins on the bottom of the CPU package along side the holes in the socket. Socket locked by retaining spring released by screwdriver
Underside of CPU module with field of pins next to socket Underside of CPU module with field of pins next to socket
The printable eBook version of The Laptop Repair Workbook is now available for download anywhere in the world.