I am just as curious too where and how dendrites appeared from. Well, there are many unexplained phenemonena out in
nature that is difficult to explain.
My guess . . .
Dendrites may not seems "alive" however, under the right condition (the presence of the right "nutritions", it become
"alive". If moisture is the main ingredient, then whatever is in this mositure droplets is the "catalysts" to bring
dendrites "alive." The surface on which the dendrites grow would be of difference level of resistance. Hence, it forms
fern-like structures instead of a straight row or line.
I am be talking nonsense as it is 7:30am in the morning, still half-awake.
Regards,
Wee Mei
[log in to unmask] wrote:
> Hi, Wee Mei,
>
> Dendrites can be (and usually are) on top of Solder mask but underneath
> conformal coating. Solder mask, of course, leaves exposed metal where
> components are soldered, test pads are located, etc. It just takes a bias
> voltage to make microscopic "seeds" of ionic contamination on the surface
> grow between the points of differential voltage.
>
> On top of conformal coating, if dendrites happen at all, it doesn't matter.
> The metal they would short to is on one side of the coating and the
> dendrites would be on the other side, so they never come into contact.
>
> I've always been curious to know, though - where do these beautiful and
> quite substantial fern-like growths get all the material from to grow like
> that? Their botanical look-alikes draw nutrition from the soil they grow in
> - what do dendrites draw on to grow? It's not like they're "alive" or
> anything. What are dendrites composed of (in general terms, not specific
> chemical analysis, which will differ from specimen to specimen)?
>
> Peter
>
> Lum Wee Mei <[log in to unmask]> 06/02/2003 07:22 AM
> Sent by: TechNet <[log in to unmask]>
>
> Please respond to "TechNet E-Mail Forum."; Please respond to Lum Wee Mei
>
> To: [log in to unmask]
> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
> Subject: Re: [TN] Dendrites
>
> Susan,
>
> I am not a reliability gal but curious to learn. While it is understandable
> that dendrites can formed under moisture condition between conductive
> patterns, how dendrites can be present on top of solder mask or conformal
> coating? Just my curiousity?
>
> Regards,
> Wee Mei
>
> [log in to unmask] wrote:
> It would be good to know where the dendrites are located. You might
> be able
> to determine this with stereo microscropes. You need to determine if
> they are under the solder mask or on top of the solder mask.
>
> The main way to get the dendrites to grow would be to add moisture
> and a bias.
>
> Are the assemblies conformally coated? Have you done a simple ionic
> cleanliness test?
>
> Susan Mansilla
> Robisan Lab---------------------------------------------------
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