Skills for hand welding of SD NAND chip

Recently, we have received many customers' feedback about using SD NAND: When the customer welds the SD NAND to the board by hand, the chip cannot be recognized. And then we blow the chip off the board, the chip also cannot be recognized by the computer.

  Regard this situation, we will explain how to use and it’s characteristics of CS SD NAND in this article.

For the hand welding, different customers use different tools. Some use electric iron, and some use hot air guns.

Some customers feedback that after they welding the SD NAND, the chip can’t be recognized by the computer. But this problem was not found during mass production. Why?

After checking with these customers that all these SD NAND can’t be recognized are all weld by hand, and the temperature used in the welding process is 390 ℃, even more than 400 ℃ .The temperatures are far higher than the temperature of the SMT automatic chip mounting machine in the factory. The maximum temperature for SMT in the factory is about 250 ℃ (which is why such problems do not occur in mass production), and the chip mounting speed is fast, The chip will not be kept at the high temperature for a long time.

There are two points caused the problem when hand-welding:

1. As we know IC is a humidity sensitive product, when customers weld the samples by hand, the samples are basically exposed to the air for a long time. The chip surely be absorbed some water vapor. (That is why the patch factory stipulate that if the chip is exposed to the air for a period of time, it must be baked for a period of time before it can be put online.) Before made the hand welding, they will not bake the chip.

2. In addition, the welding time is different for different workers. So it is suggest that the temperature during sample welding should be controlled within 300 ℃, whether it is electric iron or hot air gun. The welding method must be fast and accurate. You can image even if a piece of iron is welded at a temperature of several hundred degrees for a long time, it will be unbearable.

CS SD NAND is a special form of NAND Flash, which includes an SD controller and NAND Flash. It is characterized by small package and convenient use. At present, the capacity of CS SD NAND mainly includes 1Gb, 4Gb, 32Gb,64Gb etc. The package is LGA-8. It is widely used in the toy and audio headset market, as well as in aerospace, vehicle, rail transit, water conservancy inspection and other industries. For customers, SD NAND FLASH simply is a patch SD (TF) card to store some data, pictures or audio. Or it also can be a miniaturized eMMC which is convenient for welding, eliminating the trouble of ECC verification and bad block management in your program.