[sdiy] Transition to Lead-Free Hand Soldering

Tristan tu at alphalink.com.au
Fri Aug 20 09:29:54 CEST 2021


Is leaded SMT assembly still a widely available process? Apart from military and certain other specialist 
applications pretty much all commercial assembly should now be for RoHS compliant products. Legacy 
products were given a special exemption but there are probably not too many products still being 
manufactured unchanged 20 years on. 

/Tristan

On Fri, Aug 20th, 2021 at 4:47 PM, cheater cheater <cheater00social at gmail.com> wrote:

> Why not use leaded solder paste?
> 
> On Fri, Aug 20, 2021 at 6:54 AM Tristan <tu at alphalink.com.au> wrote:
> >
> > Well, if I was going to do all SMT I would be going with RoHS solder paste
> and hot air reflow. If I needed
> > to mount some TH components as well then it makes sense to me to keep the
> entire board lead-free
> > rather than mixing solders on the same board. While it would be possible to
> sneak some leaded solder in
> > there, from a long term maintenance perspective I think it is better to be
> consistent.
> >
> > /Tristan
> >
> > On Fri, Aug 20th, 2021 at 11:49 AM, cheater cheater
> <cheater00social at gmail.com> wrote:
> >
> > > > if I started doing surface mount then it would probably make more sense
> to
> > > use lead free solder in those projects.
> > >
> > > Why? What's the point? smt devices work perfectly well with leaded.
> > >
> > > On Fri, Aug 20, 2021 at 3:10 AM Tristan <tu at alphalink.com.au> wrote:
> > > >
> > > > I am still using leaded solder for new projects and maintenance of
> older
> > > gear. Almost all of it is TH but if I
> > > > started doing surface mount then it would probably make more sense to
> use
> > > lead free solder in those
> > > > projects. At present I only use lead free solder for work on RoHS
> compliant
> > > gear or if required for specific
> > > > component compatibility.
> > > >
> > > > Lead free solder joints are known to be more brittle than leaded
> solder
> > > joints as well as being more prone
> > > > to developing tin whiskers. That is probably why you are seeing an
> increase
> > > in broken joints on jacks and
> > > > pots etc. Some lead free solder formulations have been developed in an
> > > attempt to get around these
> > > > issues but for me continuing with leaded solder is the simplest
> solution.
> > > >
> > > > For new designs it would be worth creating them in such a way that
> > > components such as connectors,
> > > > jacks, pots and switches are directly secured to the case or panel and
> do
> > > not place mechanical stress on
> > > > their solder connections to the PCB. Creating small I/O boards which
> > > connect to the main board via a
> > > > cable could also be used to help isolate the stresses.
> > > >
> > > > /Tristan
> > > >
> > > > On Fri, Aug 20th, 2021 at 10:02 AM, Kenneth Balys <kenny at beatkamp.com>
> > > wrote:
> > > >
> > > > > I use lead on that which is leaded. Using fancy new Pb'less solder on
> a
> > > 70's
> > > > > era synth seems wrong.,
> > > > > -------- Original message --------From: cheater cheater via
> Synth-diy
> > > > > <synth-diy at synth-diy.org> Date: 19/08/2021  19:59  (GMT-05:00) To:
> Mike
> > > > > Beauchamp <list at mikebeauchamp.com> Cc: synth-diy at synth-diy.org
> Subject:
> > > Re:
> > > > > [sdiy] Transition to Lead-Free Hand Soldering Honestly, go back to
> > > leaded.
> > > > > There's no good reason for you to uselead free. You're not saving
> the
> > > > > environment or anyone's health(including yours) and you're just
> making
> > > work
> > > > > more difficult foryourself.If your flux is sputtering, use
> (genuine!!!)
> > > > > AmTech 599 tacky flux.This is the best flux I have and it keeps for
> ages
> > > even
> > > > > just left onthe shelf.On Thu, Aug 19, 2021 at 9:50 PM Mike Beauchamp
> > > > > <list at mikebeauchamp.com> wrote:>> I've recently started
> transitioning
> > > into
> > > > > Lead-Free solder for all of my> projects. Now that surface-mount
> assembly
> > > is
> > > > > affordable in small> quantities, it's very easy to get boards made
> using
> > > > > lead-free finishes> and solders but the hand-soldering is a more
> > > difficult
> > > > > transition.>> After a conversation with Kester on the telephone
> (it's
> > > amazing
> > > > > how> helpful companies can be over the phone), they suggested a few
> > > products>
> > > > > for me to try and I've now gone through a few rolls to give some
> > > opinions.>>
> > > > > For Water-Soluble flux, I am using Kester Part # 24-9574-6403> which
> is
> > > a
> > > > > .031" K100LD solder with the Organic 331 Flux.>> For No-Clean solder,
> I
> > > am
> > > > > using Kester Part # 24-9574-7618> which is a .031" K100LD solder
> with
> > > 3.3%
> > > > > Mildly Activated Rosin 275 Flux.>> K100LD is described as "a
> eutectic
> > > > > Tin/Copper alloy with controlled> metallic dopants  to control the
> > > > > grainstructure  within  the  solder> joint,  and  to  minimize  the
> > > > > dissolution  of  copper  into  the> solder  pot.    K100LD
> > > > > virtually  eliminates  the  occurrence  of> common  defects  such
> > > > > as  icicling  and  bridging.    The  improved> grainstructure also
> > > > > results in shinier solder joints than traditional> lead-free alloy
> > > > > alternatives".>> I'm not sure what all of that means, but it's a
> cheaper
> > > > > alternative to> SAC305 at less than half the price for a roll and
> seems
> > > to be
> > > > > designed> with hand-soldering thru-hole components in mind.>>> In
> use,
> > > both
> > > > > solders are "OK". I increased my tip temperature to those>
> recommended
> > > by
> > > > > Kester right away, but was still noticing that the> lead-free solder
> > > remains
> > > > > "goopier" and doesn't wet and flow into gaps> nearly as fast, or
> > > sometimes at
> > > > > all. As I continued to increase the tip> temperature, this did change
> and
> > > the
> > > > > solder started acting more like the> Lead I've used for 20 years.>>
> I
> > > now
> > > > > have my Hakko 936 set to 800 degrees and things are mostly> working,
> but
> > > not
> > > > > getting great flow on TH components that are being> attached to the
> > > ground
> > > > > plane (even with thermal reliefs on the board).> Also at this
> > > temperature
> > > > > both solders, especially the 275 Flux is> spattering pretty crazy
> and
> > > eye
> > > > > protection is probably recommended. The> flux residue from this
> solder
> > > has
> > > > > also completely gummed up my fume> extraction tube as well, so that
> is
> > > also
> > > > > something to look out for and> to be changing pre-filters often. I'm
> > > also
> > > > > noticing that soldering pins> of cheap plastic IDC headers, it's
> very
> > > easy to
> > > > > melt the plastic with> the 800F heat, so I don't dwell on them for
> long
> > > at
> > > > > all. Maybe better> parts have higher heat tolerance?>> These solders
> > > work
> > > > > good enough to get the job done the first time, but> if you try to
> > > rework
> > > > > something or correct a mistake, the solders will> suddenly change to
> > > sticky
> > > > > goo so I usually just suck the solder off> completely and start with
> new
> > > > > solder.>>> Kester has a good PDF to troubleshoot lead free hand
> > > soldering
> > > > > issues:>
> > > > >
> https://www.kester.com/Portals/0/Documents/Knowledge%20Base/Lead-free-
> > > > Handsoldering.Final_.4.19.06.pdf>>>
> > > > > So there's definitely a compromise, but those two Kester parts are
> a>
> > > good
> > > > > substitute for the leaded versions I was previously using (as>
> suggested
> > > by
> > > > > Paul S. on here years ago). Next time I redesign my PCBS,> I'm going
> to
> > > use a
> > > > > more aggressive thermal relief on ground plane> thru-holes and I
> think
> > > the
> > > > > tip temperature should be adjusted based on> the physical dimensions
> of
> > > the
> > > > > parts being soldered.>> I'm not sure about the long-term reliability
> of
> > > > > Lead-Free solder. In my> repair shop, I get a lot of music gear
> coming
> > > in
> > > > > with broken solders on> PCB-mounted jacks, pots, tube sockets, etc
> and I
> > > > > can't help thinking> that the lead-free solder is more brittle and
> prone
> > > to
> > > > > failure in these> applications.>>> Have you converted to lead-free
> in
> > > your
> > > > > hobby as well? I'm curious to> hear others' suggestions and
> > > experiences.>>
> > > > > Mike>>>>>>>>>>>>>>>>
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