De-soldering of flash memory chips: Most chips are packed in a TSOP or micro BGA casing nowadays. This article discusses methods to remove these chips because special de-soldering equipment is needed for de-soldering to prevent damaging of chips and therefore loss of data. Especially chips packed in micro BGA casings need special

* How to remove TSOP chips
A NAND512 from manufacturer ST(SGS-Thomson) is an example of a flash memory chip packed in a TSOP casing. Although not preferred, TSOP chips can be removed from a PCB with a soldering iron. This method is not preferred because a lot of solder has to be applied on the pins of the chip. It takes a long time to clean the chip afterwards. A better way of removing a TSOP chip is with hot air. Figure 9 shows how this method works. Hot air is blown on the edges of a TSOP chip. Therefore the temperature of the chip itself stays lower than the temperature of the solder connections. When the solder is melted a vacuum air gripper pulls the chip off.


* How to remove micro BGA chips
An example of a flash memory chip in micro BGA casing is RD28F6408W18 from manufacturer Intel. This example has 56 balls. Micro BGA chips can be removed with hot air using a rework station. A rework station uses a temperature profile to remove a chip. The temperature has to be hot enough to melt the solder. But be careful: The chip may be damaged if the temperature is too high. The reader is referred to for more information about rework temperature profiles. Especially lead free chips must be handled carefully because lead free solder has a higher melting temperature. The temperature profile is different for each chip and PCB because the convection of heat is subject to many parameters like the thickness of the PCB, the number of layers, the size of the nozzle and the chip size. Always practice on a reference model before removing a chip from an exhibit and use a temperature sensor mounted at the side of the flash memory chip for temperature logging. An example of a rework station is a TF2000 from manufacturer Pace. This rework station can also be used to replace chips.


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