Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
WEN-YUNG
Level 3
Level 3
100 sign-ins First like received 50 sign-ins

Dear IFXer,

Normally the junction is not accessible for direct thermal measurement. As a alternative, case temperature based on junction estimation is a reasonable approach. 

Could you help advise the measurement point for PG-HSOF-8 package? and how does different about these measurement point? such as temperature varies.

1. Drain lead

2. Mid of mold center

3. Drain ear

4. Source lead

 

WENYUNG_0-1711028252817.png

 

0 Likes
1 Solution
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

   Thank you for posting on the Infineon community. 

In this case the approximation Ttab = Tcase cannot be done for this package, as the thermal resistance from junction to tab and from junction to case are not the same. This MOSFET part is a bottom cooled one. Hence the drain tab of the MOSFET is connected to the bottom metal pad which is basically cooled by the heatsink on the other side of the PCB. Since this is a metal pin, then temperature of this would flow to the bottom heatsink at a faster rate compared to the plastic case of the MOSFET. Hence if we measure the temperature of this metal tab, it would be less. Hence the case temperature should be measured on the hottest spot on the back metal beneath the dies. A possible way is to drill a hole through the PCB and heatsink to place the thermal couple.
 
Abhilash_P_1-1711097292721.png

 

There are also two factor to affect the measurement.
1. Is the power dissipation accurate enough? 
2. The wires of thermal couple should be as thin as possible for thick wire can cool the surface temperature. Even thin wires also cause error.
 
Regards,
Abhilash P

View solution in original post

0 Likes
3 Replies
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

   Thank you for posting on the Infineon community. 

In this case the approximation Ttab = Tcase cannot be done for this package, as the thermal resistance from junction to tab and from junction to case are not the same. This MOSFET part is a bottom cooled one. Hence the drain tab of the MOSFET is connected to the bottom metal pad which is basically cooled by the heatsink on the other side of the PCB. Since this is a metal pin, then temperature of this would flow to the bottom heatsink at a faster rate compared to the plastic case of the MOSFET. Hence if we measure the temperature of this metal tab, it would be less. Hence the case temperature should be measured on the hottest spot on the back metal beneath the dies. A possible way is to drill a hole through the PCB and heatsink to place the thermal couple.
 
Abhilash_P_1-1711097292721.png

 

There are also two factor to affect the measurement.
1. Is the power dissipation accurate enough? 
2. The wires of thermal couple should be as thin as possible for thick wire can cool the surface temperature. Even thin wires also cause error.
 
Regards,
Abhilash P
0 Likes

Dear Sir, 

thank your for recommended. 
In our product is not available to drill the small hole and use thermal couple to measured. Could you have plan B for this thermal measurement? Thank you!

0 Likes
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

Other method is by using a thermal camera. But if you want to get the same Tj using IR camara and thermal couple, it will be very hard. Maybe you can coordinate the two Tj (e.g. Tj@IR camara=20+Tj@thermal couple), this should be feasible with sufficiently large samples.

Regards,
Abhilash P

0 Likes