Why can't you buy TO247 standard diodes with low Vf?

[cupoftea]

Hi,
We are doing 4kW PSU from 100-265VAC.

We want to use a mains input diode bridge where each “leg” is made of two GBJ5010’s each back to back on the same heatsink. The four upper and four lower diodes will be paralleled. (on same heatsink so share current well)
The other “leg” will be the same. So four GBJ5010’s will make up one diode bridge.

However, no offtheshelf heatsink (less than £10) has room/shape to screw a GBJ5010 to front and back….

….Therefore, we looked into doing it with TO247 diodes instead……(ie, TO247 diode screwed to front and back of heatsink)….and just live with the fact that this will halve the number of diodes used.
However, there are no TO247 standard diodes offtheshelf which have Vf anywhere near as low as the GBJ5010 type diode bridge diodes.

Why is this? Why cant you buy a Low Vf TO247 standard diode?

GBJ5010

https://www.mouser.co.uk/datasheet/2/258/GBJ50005_7eGBJ5010_GBJ_-2510579.pdf

 

[Easy peasy]

because that package for one or two diodes max, is expensive and hence used for better diodes, the classic 1kV 35V SIL bridge has 4 diodes in a pretty crappy thermal plastic - but easy mount to a heatsink with just a bit of goo.
The STTH6004 is the nearest equivalent for Vf - but only 400V

put 2 x 600V 35A or 50A SIL's in parallel on the same sink - works fine - lots of goo ...

at 80 deg C the Vf will be about 0.75V per diode, giving about 15W per 10 amps ....

--- Updated May 4, 2022 ---

https://www.vishay.com/docs/84809/pb5006.pdf