Two MOSFETs placed swiched with common Heat sink

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cross mob
babum
Level 1
Level 1
10 sign-ins First reply posted First like received

Hi all,

 

We are using IMZA120R007M1H Sic Power MOSFET in our Design.

  1. we are switching Two MOSFETs Simultaneously, those two MOSFETs fixed to a common Base plate, in this condition how the temperature will rise between the MOSFETs.
  •  

mosfet.png

  • Like above shown in image MOSFETs are placed in base plate (75mmX90mmX15mm).
  1. By placing two MOSFETs in one base plate, weather the temperature of two MOSFETs will add increase the temperature or it will separate the temperature.
  2. In IMZA120R007M1H Data sheet Rth(j-a)=62K/W and Rth(j-c)=0.20K/W.
  3. How to convert this K/W to °C/W, please suggest any formula is available.

 

1 Solution
Santhoshkumar
Moderator
Moderator
Moderator
25 solutions authored First like given 50 replies posted

Dear @babum ,
Greetings from Infineon,

1. We cannot provide the exact temperature rise via calculation in this case because thermal analysis is necessary to estimate the the temperature rise. 
2. In my opinion it will create a hotspot at a centre of both mosfets, and the heat sink doesn't seem to be enough for 50W of loss. 
3. 0 degree Celsius equals 273.15 k, but a one degree rise in Celsius is exactly equal to a rise of one kelvin on the Kelvin scale. so K/w=degC/W no need of conversion.

Suggestions:
If you do not have an access to the thermal simulation software then its better to go with the oversized heat sink and keep the devices at least 20-25mm apart from each other and mount it horizontally as shown in below picture and attach heatsink on top of the devices, add a small BLDC fan for further cooling. 
 
 
 
 
 
 

Best regards,
Santhosh Kumar

View solution in original post

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3 Replies
Santhoshkumar
Moderator
Moderator
Moderator
25 solutions authored First like given 50 replies posted

Dear @babum ,
Greetings from Infineon,
Thank you for posting your query in Infineon Community.

  1. By placing two MOSFETs in one base plate, weather the temperature of two MOSFETs will add increase the temperature or it will separate the temperature.
    The losses of the two MOSFETs will add up and will eventually increase the temperature based on the thermal resistance of the base plate.
  2. In IMZA120R007M1H Data sheet Rth(j-a)=62K/W and Rth(j-c)=0.20K/W. How to convert this K/W to °C/W, please suggest any formula is available

    1 K/w = 1 °C/W
    Hence, to convert Kelvin/Watt to Celsius/Watt, we just need to multiply the number by 1.

kindly let us know if you have any further queries.

Best regards,
Santhosh Kumar

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Dear Santhosh Kumar,
 
 
  • We are planning to operate each MOSFET at 25W power dissipation for continuous power ON for 30min.
  • In Data sheet of IMZA120R007M1H the Rth(j-a) is 62K/W. 
  • For 25W power dissipation how much temperature will raise on Both MOSFETs?
  • We are calculating temperature raise based on  ΔT = Rth(j-a)°C/W  X PowerDissipation
              •   Ex.           ΔT = 62°C/W X 2W  (for 2W power dissipation)   
                                    ΔT= 124°C.
                 
  • Please let me know how to calculate the raise in temperature on the MOSFETs.
0 Likes
Santhoshkumar
Moderator
Moderator
Moderator
25 solutions authored First like given 50 replies posted

Dear @babum ,
Greetings from Infineon,

1. We cannot provide the exact temperature rise via calculation in this case because thermal analysis is necessary to estimate the the temperature rise. 
2. In my opinion it will create a hotspot at a centre of both mosfets, and the heat sink doesn't seem to be enough for 50W of loss. 
3. 0 degree Celsius equals 273.15 k, but a one degree rise in Celsius is exactly equal to a rise of one kelvin on the Kelvin scale. so K/w=degC/W no need of conversion.

Suggestions:
If you do not have an access to the thermal simulation software then its better to go with the oversized heat sink and keep the devices at least 20-25mm apart from each other and mount it horizontally as shown in below picture and attach heatsink on top of the devices, add a small BLDC fan for further cooling. 
 
 
 
 
 
 

Best regards,
Santhosh Kumar

0 Likes