Homebrew PCBs

Stefan,

You shouldn't see whiskers on the solder.  Three percent lead in the 
solder is sufficient to prevent whiskers. One of the problems with 
whiskers is that you can have two samples from the same batch, where one 
will develop whiskers, while the other does not. The parts don't have to 
be old to have whiskers.  Parts with newer finishes don't include tin, 
so they are immune.


On 7/30/2016 10:42 PM, Stefan Trethan stefan_trethan@... 
[Homebrew_PCBs] wrote:
>
> That's not been my experience.
> I haven't seen any whiskers on solder, but since I look I often see
> them on plated metal parts (relay housings, shielding boxes, brackets,
> switches, etc.) and also some components leads of ICs and such.
> This has always been in very old equipment 30 years+, well pre-ROHS. I
> have never found whiskers in modern or leadfree soldered equipment
> myself, but don't doubt others might have.
> Perhaps it is just that the old whiskers are much longer, and can be
> spotted with the naked eye, but I have always considered this a legacy
> problem from before they knew to avoid bright tin plating. I think in
> many situations they would just burn away, they are very thin.
>
> >From what I understand it's mostly the bright (pure) tin plating
> that's the problem, and most alloy solders are fine, even if it is
> just small amounts mixed in. It's also a factor how thick the plating
> is (galvanic or hot dipped) but don't recall which is worse.
>
> ST
>
> On Sun, Jul 31, 2016 at 12:35 AM, Harvey White madyn@...
> > From what I know, regular tin plating is not a problem. Mostly tin
> > solder is. How long this whisker growth takes I do not know, a rough
> > suspicion (and that's all it is) says 3 to 5 years regardless of what
> > you do.
>
>