Hello,
in my latest psu design which finally worked as intended, I needed to put more bulk caps on 3.3v rail output. long story short: space is small and eventually required 3x2200uF (besides 2x470u polymer + 22uF 1210 ceramics).
I previously used just SMD caps while the board already has some through hole components. I figured out why not see elec. caps which are through hole. I decided to use Lelon caps due to performance vs price.
I came to the following foundings:
1- through hole caps are better in terms of ESR, I figured maybe due to SMD base leads having more resistance and inductance. mostly they are 2 times better.
2- through hole caps are cheaper, not always cheaper and not always by big margin.
here is a simple example of directly comparable caps... specs -> 470uF, 16v, diameter of 8mm, rated for 5000 hours:
TH (
RXW471M1CBK-0811): price is 49.7$ for 1k quantity, ESR is 85 mOhm.
SMD (
VZH471M1CTR-0810): price is 63.8$ for 1k quantity, ESR is 170 mOhm.
but for my design I went with
RXW222M1ABKF1020 which has 35 mOhm which is the cheapest of RXW series (low ESR series) of about 134$ for 1k, cheapest SMD low ESR VZH series is
VZH222M1ATR-1316 which has 60 mOhm and its size is bigger + 243$ for 1k.
adding to that, most teardowns I see of PSU equipment especially high end ones always use through hole, power modules like Recom and meanwell use through hole.
as for polymer caps... through hole Lelon 6.3v 330uF cap has 8 mOhm ESR vs 15 mOhm SMD counterpart while through hole is a bit cheaper.
are my findings correct?
what is your opinion and choices for this?
what drives designers to using through hole vs smd?