Basic requirements prior to beginning the soldering process :
There are three possiblities to solder a bios chip on the board:
With a BGA rework station, a hot air station or a soldering iron.
Soldering with a BGA rework station:
You can do this only in an industrial or a bigger repair workshop, seeing the fact that a good rework station costs several thousand euros.
The repair usually consists of the following steps:
The repair process runs according to the following steps:
The components and plastic parts surrounding the chip are, if needed, masked with protective film. To avoid board buckles the motherboard is heated on a hot plate over a large area and from below. The chip is unsoldered / soldered by means of an IR heater from above. The temperature curve (heating- up phase, holding phase, cool-down phase) priorly adapted for the component and the board provides here an optimal reproducible soldering result.
Picture: Rework workstation
Soldering with soldering iron
-Soldering station: The soldering tip temperature should be adjustable. The soldering station should have enough reserves to heat the solder joint very quickly and complete the soldering process after maximum one second. Contrary to many opinions that circulate on internet, it is necessary to use a wide soldering tip to solder or unsolder the Bios Chips.
-soldering tin: it is preferable to use a thin SMD soldering tip with soldering flux.
-soldering flux: provides good flow properties and joints. Can partly be used to remove solder straps.
-tweezers: for placing and aligning the Bios chips it is necessary to use secure closing and stable holding tweezers.
-desoldering braid: to remove the residual soldering tin you need desoldering braids.
-magnifier: needed to check the solder joint.
Replacement of Bios Chips:
The motherboard must be well fixed during the soldering process to prevent slipping out of position while soldering.
Bios Chips repair work is usually performed according to the following steps:
-Original Bios Chip is unsoldered
-Residual solder tin is removed
-Soldering joint is prepared
-Reprogrammed Bios Chip is placed, adjusted and soldered
-Final check with magnifier
-The board is cleaned.
Unsolder the Bios Chip:
This is the most difficult part of the work, because here you must be particularly careful not to damage ( break down) the solder pads (joint plane). This method is suitable only for experienced hands, not for beginners. It is particularly important to have a tip which is at least as wide as all the pins on the side of a Bios chip. The pins on the Bios chip shoud be bridged on one side with solder tin. Heat all pins simultaneously with the wide soldering tip and using some tweezers slightly and very carefully lift the Bios chip until all pins on thie side come loose from the connection points. Then you repeat the procedure for the other side of the chip.
Alternatively, you can heat all pins on Chip individually and lift them with tweezers or a fine screwdriver from the chip. After having unsoldered the Bios chip remove the excess solder using desoldering braids and re-tin the pads with solder.
How to solder Bios Chips:
First, the pads (solder pads) are equiped with flux. Then, the chip is put and aligned in the correct position on the solder pads ( Please note polarity and marking). Next, two diagonally opposite pins are solidly soldered. After having assured yourself that the chip is placed in the exact position and aligned, solder the other pins. Finally check with the magnifier if all required connections really exist and make sure that you did not solder a short circuit between the adjacent pins.
Picture: Bios Chip and iron tool
Soldering with hot air station:
-Hot air station ( temperature and airflow rate should be controllabel/ adjustable)
-Nozzles ( proper size is important)
-Tweezers or vacuum pipette
First of all, the pins at Bios Chop are moistened with flux. After that, the chip is heated with the hot air station and is carefully lifted with tweezers or a vacuum pipette. To avoid overheating or shift of the components you must pay attention to the right temperature and to the right airflow rate. If sensitive components or plastic parts are in the immediate proximity, they must be first masked off with Kapton tape.
To resolder the Bios chip is as simple as to unsolder it. The connection pads are moistened with flux or solder paste. The Bios chip is placed and aligned with the aid of tweezers (Please here also note the mounting direction!). The Bios chip and the motherboard are heated with the hot air blower and soldered. Finally, the solder joint should be checked with a magnifier.
Picture: Hot Air soldering