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How to choose heatsink
ⅠThe basic rules
1 Basis
First is the thermal resistance of power semiconductor devices (junction to case thermal resistance and thermal contact resistance) and power dissipation, the second is the highest junction temperature and the temperature of the cooling medium.
2 Determination of fastening force
Fastening force(torque) is an important parameter of indispensable connection device and the heatsink, the correct determination and use it, to ensure the long-term stability and reliability of devices. When no given a fastening force, please use the fastening force 1.3-1.6kN/cm2.
3 The conditions of cooling
Natural cooling: The ambient air temperature is not higher than 40°C, air natural convection wind speed less than 0.5m/s.
Air cooling:Entrance air temperature is not higher than 40°C, wind entrance is 6m/s
Water cooling:Entrance water temperature is not higher than 35°C, water flowis 4L/min.
4.The general principle of -
Main parameters and their meanings of Thyristor diode
1.Positive average current IF(AV) (rectifier)/ Average on state current IT(AV) (SCR) is the maximum half sine wave current average value at heat sink temperature(THS ) or package temperature( TC). At this time, the junction temperature of device will be allowed to maximum.
2. Positive RMS current IF（RMS）(rectifier)/On state RMS current IT（RMS）(thyristor) is the maximum effective current value at heat sink temperature(THS ) or package temperature( TC). Users in the use, shall ensure that in any condition, the effective value of current flowing through the device does not exceed the root mean square current corresponding package temperature value.
3． Surge current IFSM(rectifier)/ ITSM(thyristor)
In exceptional circumstances, device can be bear the maximum instantaneous overload current value. Surge current value is 80% VRRM of device in the maximum allowable junction temperature.
4． Non repetitive peak off state voltage VDSM/Non repetitive peak reverse voltage VRSM
Means Thyristor or rectifier can be withstand in maximum turning off state voltage, generally use single pulse to test and prevent device damage.
5． Repetitive peak off state voltage VDSM/Repetitive peak reverse voltage VRRM
In the condition off state, off state and reverse can bear max repetitive peak voltage, generally equal to 90% non-repeat voltage of the devices
6． Repetitive peak off state (leakage) current IDRM/Repetitive peak reverse (leakage) current IRRM
In the condition of off state, the current will pass through thyristor which applied with VDSM / VRRM.
7． VTM=VTO+rT*ITM VFM=VFO+rF*IFM
On State peak voltage V (thyristor)/Peak forward voltage VFM(rectifier)
Means peak voltage of device which through the peak forward current IFM (rectifier) or on State peak current of I TM (thyristor). This parameter reflects directly the conduction loss characteristics of the device, influences on state current rating. The threshold vo -
What will effect on the rate of migration at high
The mobility rate bill be effected by transverse and longitudinal electric field in MOS. When Vd increases, the transverse electric field increases, the mobility increase. When Vg increases the longitudinal electric field increases. When the rate of migration effected by longitudinal electric field more than transverse electric field, Migration rate decreased.
