[HN Gopher] Superlattices Could Make Bulky Capacitors Obsolete
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       Superlattices Could Make Bulky Capacitors Obsolete
        
       Author : rbanffy
       Score  : 41 points
       Date   : 2022-08-11 13:59 UTC (2 days ago)
        
 (HTM) web link (spectrum.ieee.org)
 (TXT) w3m dump (spectrum.ieee.org)
        
       | wildzzz wrote:
       | Lead is no problem for RoHS-exempt components. If they can use
       | these superlattice caps to replace tantalum caps, I'm all for it.
       | Those suckers take up so much space in small designs that you
       | sometimes have to forego the recommended decoupling caps just to
       | get the design to fit on the board.
        
         | kennywinker wrote:
         | What's an application that needs to be super small, but doesn't
         | risk getting lead into people's bloodstream and the
         | environment? I can't think of many...
        
         | lightedman wrote:
         | The problem is that most electronic components are RoHS today.
         | So getting these into other devices will mean loss of RoHS
         | certification, and that is something a lot of companies don't
         | want right now due to the environmental movement. Many use that
         | as a selling/marketing point.
         | 
         | I'm hoping for other superlattice materials to become
         | available.
        
           | [deleted]
        
           | adammunich wrote:
           | Lead is exempt when used in ceramic capacitors
        
             | lightedman wrote:
             | Didn't that exemption expire some time before 2010? I know
             | there were some time-based exemptions.
        
           | GekkePrutser wrote:
           | But RoHS permits lead if there's no reasonable alternative.
           | One example is lead acid batteries which contain a lot of
           | lead. A similar exemption could be made for these I guess if
           | they're really that promising.
        
         | jleahy wrote:
         | Out of interest, why do tantalums get used so much over
         | ceramics (or electrolytics even) for bulk decoupling? DC bias
         | can be a pain I know, but I always thought of ceramics as
         | cheaper / less fiery alternatives.
        
           | wiml wrote:
           | They were more compact than alternatives at the time, and had
           | lower ESR. This made them especially desirable for supply
           | decoupling in digital logic, whose random fast edges means a
           | lot of broadband noise to shunt -- you can't just design to a
           | particular frequency range like you can with most analog
           | circuitry.
           | 
           | Digital was also the new expensive hotness, and putting in a
           | tant wasn't going to be a big fraction of BOM cost.
           | 
           | These days my understanding is that ceramics and non-tantalum
           | electrolytics have gotten good enough to replace most
           | tantalum uses, and between that, the expense, the slavery,
           | the exploding, and the environmental damage, they're less
           | common than they once were.
        
           | nousermane wrote:
           | > why do tantalums get used so much over ceramics for bulk
           | decoupling?
           | 
           | higher energy density
           | 
           | > (or electrolytics even)
           | 
           | no risk of drying up. Also, higher energy density, especially
           | for small parts.
        
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       (page generated 2022-08-13 23:01 UTC)