DIY Soldered BIOS Repair
Soldered BIOS Repair
A hot air rework station is the easiest method of removing your BIOS or CMOS chip if you have access to one.
With some chips it is possible to remove them by making a wire frame from 2.5 mm copper wire. this can be placed around a PLCC chip and the pins can be flooded with solder. The chip can then be gently removed with tweezers
This article is designed for people that do not have access to a hot air station, or any other expensive equipment, buying this equipment to repair one motherboard is just not viable.
If you do not take care performing this procedure, your motherboard could end up beyond repair. I don't suggest you try this without first practicing on an old board to see where you are going to fail if at all. You can then pay special attention to those area's.
We certainly wont be held responsible for anyone's use of this procedure, use it at your own risk. You may be better of sending your board in and making use of our Soldered BIOS Repair Service.
Care must be taken not to damage or lift the track's on the motherboard surface, and also not to dislodge and adjacent components.
Most damage of this kind occurs through overheating. Even if you have Rework tools to remove the chip care must still be taken. If the board is poor quality then you could still end up lifting the tracks or damaging the board during the removal process.
We can fit surface mount programmed SPI serial flash, PLCC, VSOP and TSOP EEPROM's and PLCC 32 Pin Sockets, EEPROM's.
Soldered BIOS Chip Removal
When removing a soldered BIOS chip the main concern is not to damage the tracks on the mainboard. The CMOS or Flash BIOS chip can always be replaced and is the least expensive of the two.
PLCC EEPROM Removal
One corner of a PLCC chip will be angled at 45 Degrees, you should mark this corner on the board before removing the chip or take a photo. Most boards have a printed outline of the socket on the board surface but not all, some are marked with a few pin numbers pin 1 for example is usually marked but not always.
A scalpel can be used to cut the legs of the EEPROM, I use an oil stone to flatten the cutting edge of the blade at the tip . Its possible to angle the blade so that the cutting edge falls directly on to the top of the next pin as it cuts the preceding pin.
Care must be taken to ensure that you are not hitting the board surface during the process.
The flattened tip helps avoid track damage in the event of a mishap, but direct contact between blade and board surface should be avoided.
The reason for cutting away the old PLCC chip is that the remnants of the pins can easily be removed from the board one by one, without overheating the tracks using a small 15 or 20 watt soldering iron. If you don't have the right tools and you try to de solder the chip without cutting the legs then track damage is very likely to occur.
The remnants of the pins will stick to the iron as you move across them. Do not try to pull them off with tweezers or pliers as you will lift the footprint pads from the board.
This is a good time to re-tin the Pads of the footprint. excess solder can be sucked away or soaked away. At this point a little cleaning will be needed. It is a good idea to thoroughly clean the footprint with some alcohol.
Surgical spirit or Meths is ideal as it dissolves the resin based flux. Remove all the excess flux and solder particles left behind by the tinning process. Also check the tracks for damage.
When you have cleaned the pads , you can then use a no clean (non acidic) flux on the pads and the pins of the SMD socket. The flux used has to be non acidic and should also be designed for electronic use. Flux pens are available for electronic work
Once you have cut the pins and removed the legs and cleaned and fluxed the pads, you can then prepare the replacement socket. I always use a socket as you can replace the BIOS chip easily if you have to without having to solder anything. I start by removing the backing piece and the supports. You can cut the support legs one by one if you are careful from the top of the socket using a scalpel. If you keep the backing piece it can be placed in the base of the socket before refitting the CMOS chip. The socket can also have its legs fluxed a second time in readiness for soldering.
See also Fitting a PLCC 32 SMD socket
DIP EEPROM Removal
These chips can be removed the same way as the PLCC type's above. Once the legs are cut the pins can be de soldered one at a time. In doing so you avoid over heating the tracks.
Alternatively you can use a vacuum type de soldering tool to remove the chip. The first method is my preferred method, the reason being track damage due to overheating is less likely to occur.
Difficult cases
In some instances manufacturers embed the soldered CMOS or BIOS chips in epoxy resin. I've had to do repairs on chips that have been arranged like this. I find the best procedure, is to use a Dremmel or similar hobbyist's rotary tool fitted with a miniature disc cutter or mill, do wear some sort of eye protection. Cut the legs as closely as you can to the edge of the chip.
Work down carefully as close to the board surface as you dare, check first to make sure no other components are embedded within the epoxy. Care must be taken not to go to close to the board surface, or you will damage the tracks. Repeat this process on all four sides of the chip, in some cases the chip can then be gently levered from the board. If necessary more cuts can be made through the epoxy covering to ease removal of the remaining pieces.
I generally use a scalpel then to test how well the remaining epoxy pieces are adhered to the board. If your lucky the pieces will come away clean and easily, without lifting the tracks. At this stage the more channels you have cut through the remaining epoxy the better, as it will ease the removal process.
As long as there are no other components embedded within the epoxy, you can use the disc cutter to carefully remove most of the remaining epoxy resin.
I will attempt repairs to any motherboard, Laptop or control board that has a soldered PLCC 32 CMOS or BIOS chip.