wiped disk - no longer bootable

[Mike Marchywka]

On Wed, Jul 10, 2019 at 02:15:34PM +0200, Ralf Mardorf via ubuntu-users wrote:
> On Wed, 10 Jul 2019 10:28:54 +0000, Mike Marchywka wrote:
> >On Wed, Jul 10, 2019 at 11:45:05AM +0200, Ralf Mardorf via
> >ubuntu-users wrote:
> >> On Wed, 10 Jul 2019 07:56:20 +0000, Mike Marchywka wrote:  
> >> >On Wed, Jul 10, 2019 at 09:08:35AM +0200, Ralf Mardorf via
> >> >ubuntu-users wrote:  
> >> >> On Tue, 9 Jul 2019 19:08:21 -0400, Gene Heskett wrote:    
> >> >> >That mobo was simply not repairable because my hot air tools were
> >> >> >burning the foil off the board on one side while trying to
> >> >> >telegraph enough heat to the other, inaccessable side of the
> >> >> >board to free the defective caps.    
> >> >> 
> >> >> It's possible to heat both sides, unfortunately the VIAs of
> >> >> multilayer PCBs tend to be allergic to too much heat, so it's a
> >> >> game of pure chance.    
> >> >
> >> >Did these guys go lead free or you know the alloy/ melting point?
> >> >How hard is it to get to both sides?
> >> >I guess you could hack up the caps, maybe just with pliers,  leaving
> >> >just wire and through the holes but that would be a huge mess. Then
> >> >just grab the remaining wire with needle nose pliers and
> >> >pull it while heating.    
> >> 
> >> The heat isn't evenly spread. Even if you try to vacuum of the solder
> >> with a professional unsoldering station, you probably would pull the
> >> remaining wire and the VIA or as Gene already mentioned, you burn
> >> the  
> >
> >Unsoldering a ground plane may be a problem but it gets worse if the
> >melting temp of the solder has increased- curious what
> >they wave solder these days. Eutectic Pb/Sn would be great but
> >the new alloys may even have issues with their interactions
> >with the board metal- maybe making them more prone to rip on
> >desoldering. For that matter maybe even the flux chemistry matter.
> >Even with tight tolerances the facotry inserted leads should be
> >pretty straight and allow solder to flow in and then pull the thing
> >out. 
> >I guess if it is a really odd solder chemistry maybe there is a
> >selective etch that won't wreck everything nearby.
> 
> I don't know anything about the reputation of Liam's friend, but I know
> a lot about Gene's and my own reputation. It doesn't matter that much,
> since the friend I mentioned, is the kind of technician high-tech
> companies likely would hire to unsolder the components from the crashed
> space craft they hide in Area 51. Actually he was able to unsolder the
> cpas from my power supply. However, he mentioned that it wasn't easy to
> unsolder the caps. Btw. the friend told me that the odd
> lead-free solder we know from the end of the 90th improved a lot. When
> I was forced to use the first lead-free solder working for a studio
> audio gear company I was p????d off. It was comparable to using good
> solder, but using a 10 Deutsche Mark soldering gun from the
> do-it-yourself store. We had solder on our hands, in our faces, but got
> unacceptable solder joints.

Lead is a great material for solder but there is no single 
"lead free" product. At least with plumbing, which is  
copper to copper, Sn/Sb is popular and some Bi alloys
were thought to be unreliable. Ag alloys often having higher
temps and Cu may be better able to interdiffuse. And then
there are changes in fluxes. No sure if rosin core is compatible
with everything now.  I did notice the last time I watched a plumber
he was soldering with MAPP gas, much hotter than propane. 

No one is drinking circuit boards so I thought they kept the 
lead there. If you look at overall junk creation by
making repair impossible you can see even with green
technologies there are a lot of tradeoffs... 




> 
> >> PCB and you might damage the conductor path. I tried to solder out
> >> borked caps of my mixing console's SMPS with my less good equipment,
> >> a friend tried at home with a professional unsoldering station from
> >> Weller, it didn't work. At work the friend could use very good
> >> professional hot air equipment and he was able to replace the caps,
> >> but it wasn't easy to do.
> 
> 
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-- 

mike marchywka
306 charles cox
canton GA 30115
USA, Earth 
marchywka at hotmail.com
404-788-1216
ORCID: 0000-0001-9237-455X