The reflow profile ends with a cool down zone. The cool down zone cannot be so extreme so as to cool the board where the negative temperature gradient may cause brittleness in the solder joint at the end of the process of reflow.

An ultra sound machine operates on the basis of sound waves that are higher in frequencies and therefore the human ear cannot be able to pick them, this is usually above 20 kHz. These sound waves are used to give an image of an object or an organ inside the body or can also be used to measure distance.




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