Hi guys ,i want to know why does mosfet (150n03)shorted after desoldering it from the board with soldering iron (350°) !!
I test the mosfet before removing it from the board the test is OK, but after removing and discharging the electrostatic from the mosfet it become damaged !!

 

Are you leaving the gate open when testing? It could look shorted in that case. Discharging is not enough. Put a resistor between the source and gate and check for the short again.

 

Are you leaving the gate open when testing? It could look shorted in that case. Discharging is not enough. Put a resistor between the source and gate and check for the short again.

How can i leave gate open ?

 

How can i leave gate open ?

That means it's not connected to anything.

 

Lets try wording it this way: With the MOSFET removed from the board, put a resistor between the source and gate and check for the short again between drain and source. You may have been charging the gate with your ohmmeter depending on sequence of tests. Also the 150N03 is a N-Channel MOSFET and the body diode between source and drain will conduct depending on meter probe polarity. So when testing source to drain, test it as if its a diode. What you think is short may actually be body diode.

 

Certainly "body diodes" can be misleading!! The check for a shorted device needs to use a low enough voltage to not forward bias the diode. REversing polarities should give two different resistance readings if the device is not shorted. Usually!!