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Re: Diode Rectifier Differences (Repost)



Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

Hi Bert, Dave, All,

        The manufacturer of all three variations of this diode is Diodes 
Inc. and the vendor is DigiKey. The cases are all type DO-41. Since my TCs 
spend the winter in an unheated, detached garage, it seems the glass 
passivated diodes may be better, but I'm not sure they are  worth twice the 
price.

Thanks for the insight,
Matt D.

In a message dated 1/1/03 1:03:01 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:


><bert.hickman-at-aquila-dot-net>
>
>Hi Matt,
>
>"Glass passivation" is a process that adds a protective layer of glass
>above the PN junction (and sometimes the entire silicon die) to prevent
>parameter changes or other degradation of the device under high humidity or
>high temperature conditions. Glass passivated devices are commonly
>specified where either high reliability or reliable operation under harsh
>environmental conditions is needed, such as automotive, aerospace,
>military, and telecommunications.
>
>Using industry standard part designations, the 1N5408 is unpassivated while
>the 1N5408G is the same root device with glass passivation. For indoor
>Tesla Coiling, either type can be used. From a performance standpoint, the
>unpassivated device may be a bit more robust, since most vendors spec it
>with a higher forward surge current rating. However, if your system will be
>housed in area that's not temperature/humidity controlled (such as an
>unheated porch or a pole barn), go with the 1N5408G device.
>
>The 1N5408-T and 1N5408G-T devices you have found are NOT industry standard
>part designations, and I was unable to find ANY spec sheets that covered
>them. While the latter part is _most likely_ glass passivated, it's not
>clear that the 1N5408-T is (regardless of the seller's description). I'd
>recommend using a different vendor and going with industry standard parts
>so that you know exactly what you're buying.
>
>Good luck and best regards,
>
>-- Bert --
>--
>Bert Hickman
>Teslamania, from Stoneridge Engineering
>"Electromagically" (TM) Shrunken Coins
>http://www.teslamania-dot-com


<dave-at-davidspeckmd-dot-org>


 >Matt,
 >My Dad used to make power semiconductors for GE, (which later became 
Powerex).

 >All the power semiconductors that they made were glass passivated --
 >passivation indicating a treatment of the edges of the semiconductor dice
 >to reduce hot spots caused by local differences in current flow.

 >I believe that this is standard practice on all such devices, so you
 >probably would not find any significant difference in performance between
 >these three devices.  Were the prices all from one seller, or from
 >different sellers?  They may also indicate differences in package types, or
 >in guaranteed operating temperature ranges. or in permissible reverse
 >leakage currents.

 >HTH,
 >Dave Speck

 >>Hi Y'All
 >>        Could some knowledgeable person explain the difference/advantage
 >> between these diodes (if any) as applies to rectified TC supply?
 >>
 >>      1N5408        3A 1000V silicon rectifier  -at- $16.80/100
 >>      1N5408-T     3A 1000V silicon and glass passivated rectifier  -at-
 >> $19.24/100
 >>      1N5408G-T  3A 1000V glass passivated rectifier -at- $30.30/100
 >>
 >>Thanks,
 >>Matt D.