[AMPS] 8877 rectifier board considerations

[2]

>
>Hi Paul,
>
>There's no 6A equivalent part to the JTX1N5554.  Problem is, JAN parts must
>be hermetically sealed by spec, and to make a 6A glass or ceramic dual-plug,
>metalurgically-bonded part is nearly impossible because the slug diameter
>gets to be too large, so the small mismatch in the thermal coefficient of
>expansion between the die, the slugs and the glass or ceramic body can cause
>cracking under surge conditions.  It's been tried for decades without
>success.
>
>So, "we" use paralleled 3A hermetic parts like the 5554's previously
>described to provide lower Rthj-L and ~6A rectified current rating and ~250A
>Ifsm surge rating, or go to non-hermetic parts which do not suffer the
>coefficient mismatch problems, or go to custom power hybrid modules (thick
>film hybrids using large dice eutectically bonded to a CRS case).  Problem
>with the hybrids is they get very, very expensive and it's difficult to
>assemble them so they'll stand off more than a few kV, because the die to
>metal substrate (or pin seal) dimension is so small.
>
>Heatsinking does help the K2AW assemblies.  

Add a heatsink, and the perfboard version takes up less volume.  

-  R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.  
end


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