lead free solder

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What happens if you use regular solder on something that was originally
lead-free,
or you get the lead free solder on a regular iron?

I understand manufacturers keep separate lines as mixing the two is bad, but
what
about in the repair world?

Does lead free solder mess up good quality tips or anything like that?

Re: lead free solder
I was planning on getting into electronics as a hobby seriously, and I
read that they have or will ban lead solder. Is it already illegal? Is
traditional lead/tin/rosin solder still available to buy? Do we really
need such a ban? I think I should stock up on the traditional solder if
I can because from what I read, lead free solder is terrible,
especially since I want to mainly work on repairing old electronic
equipment. I'm wondering if it will even be possible to be an
electronics hobbyist anymore.


Re: lead free solder

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The situation is complex, and it depends on where exactly you are located.
As far as Europe goes, leaded solder is NOT illegal, and is unlikely to
become so. Supplies are still fairly readily available, although not as
abundantly as they were, as obviously, there is less demand. The directives
regarding the use of lead-free solder, allow for amateur and non-commercial
use of leaded solder, basically without restriction. Any equipment which was
"placed on the market" prior to July 1 2006, can be repaired, commercially,
using leaded solder if you wish. If it was constructed originally using
leaded solder, then the general opinion is that it should be repaired using
leaded solder, as there is considerable controversy as to whether leaded and
lead-free solder alloys mix to produce a joint with long-term stability.

If the item was originally constructed using lead-free, then for the same
reason, use lead-free to repair it. Any item that was placed on the market
after July 1 2006, will definitely be constructed using lead-free solder,
and lead-free components ( the other angle to staying within the terms of
the directive ). If you are a commercial repairer, you MUST use lead-free
solder and direct replacement or compatible lead-free RoHS ( Restriction of
Hazardous Substances ) certified components to perform any repair on this
equipment, and not commit a theoretical criminal offence. I say theoretical
because to date, I am not aware of anyone being prosecuted, or any means
being in place to police the directive.

You are not required to follow the terms of the directive for this
equipment, if you are working on it non-commercially ie for your own
personal purposes. Most commercial equipment has been manufactured in
lead-free for more than 2 years now, and some manufacturers - Sony for
instance - have been insisting for some time that their dealers use only
lead-free solder for carrying out repairs to their equipment, irrespective
of age or original construction materials, so apparently, they don't believe
that there is an issue with mixing alloys.

There is a lot of information on the web about this if you search " RoHS "
directive. Also, there is a lot of valuable information on the major
component suppliers' websites such as Farnell and RS Components. If you can
get hold of a copy of " Technology @ Home " magazine ( last issue ) -
www.technology-at-home.co.uk you can find the more comprehensive article
that I did.

Arfa



Re: lead free solder



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You *need* tin lead solder for repairing old gear and it's still widely
available for that very reason. It's also hugely nicer to use.

There are a number of categories of equipment that are still allowed to use tin
lead solder too. The lead free thing is intended mainly I think to apply in
reality to consumer goods but the legislation in the EU doesn't distinguish as
such.

Graham



Re: lead free solder
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Mixing leaded and lead-free solders can be problematic. Generally if a
device was built using leaded solder then leaded solder should be used
for repair.  For lead free assemblies, of course lead free solder should
be used.  The big question is, how will you be able to tell whether or
not a board was put together using leaded or lead-free solder?
Hopefully some mfrs will mark their boards accordingly but I doubt if
many will.  Just because some components may be marked as being 'lead
free' or 'RoHS compliant' doesn't mean the board was assembled with lead
free solder.  Lead free parts will work fine with leaded solders as well
as lead free solders.

As far as hobby work goes there's nothing wrong with using lead free
solder for hand work.  It's slightly more difficult to work with, but
high silver bearing solders such as SAC305 formulas seem to work the
best.  Using lots of flux is important as well, since a more agressive
flux is needed than with tin/lead solder to ensure proper wetting.  But
if you are a soldering newbie it might be better to start out with some
tin/lead solder until you get the hang of it as it is a little more
forgiving...

-Jeff

Re: lead free solder

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Are there manufacturers that are not marking their boards for lead content?
I thought it was required in Europe and all of the CE vendors that I have
seen in the US are marking the boards.

What is the problem with mixing the solders?  Other than the lead free types
making it harder to rework and needing slightly higher temps, what problems
are there?  What does "problematic" mean in this case?  Is there a real
issue or does it mean that you are not sure and are being conservative?

Leonard


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Re: lead free solder

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Hi Leonard

I have done quite a bit of research into this, and have corresponded with
several experts in the field, and it seems that the jury is still out on
this one. Half of the solder manufacturers say that it's ok to mix leaded
and unleaded, and half say not. Some of the experts that I have spoken to
say definitely not, so make up your own mind. I prefer not to mix them, as
it seems that marginally more people seem to be saying don't than do. As the
solder is still available, I see no reason to risk an unknown long term
compromise in the stability of the joint, and will continue to use like for
like, unless forced by product availability, or legislation, to do
otherwise.

Personally, I think that the whole thing is an ill-conceived and poorly
thought through excuse to justify the existence of an EU department, and the
jobs of those who work in it. And, as I've said before, the avionics
industry, and medical instruments industry, amongst others, have been
granted an exemption, and the American military flatly refuse to use it, so
what are we to make of that ... ?

Arfa



Re: lead free solder
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 From what I've read about the subject, it comes down to metallurgical
issues.  If a part with tin/lead plated leads is used in a lead free
process, the lead will contaminate the joint.  As little as 0.5% lead is
enough to weaken the joint and lead to cracking around the footprint.
What happens is the lead, as it melts at a lower temperature than tin
(we're not talking about alloys here but trace contaminating amounts),
will collect in the joint at the place that cools last, which is the
center of mass, right under the footprint.  (Obviously we're talking
about SMT components here).  This reduces the amount of tin doing the
actual bonding of the lead and can lead to early joint failure.

Boards made with lead free solders have been found to have better
reliability when thermally cycled, one reason the automotive companies
have embraced lead free assembly here in the USA.  Long term reliability
due to tin whiskers is the issue no one wants to talk about however, as
the process of whisker formation is still not well understood.

-Jeff

Re: lead free solder
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   Tin can fracture at low temperatures.


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Re: lead free solder



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Yes, but I gather that the other way round is just fine.

Graham


Re: lead free solder
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   Lenoard, From what I've read you should wick away most of the old
solder and do the repair with eutectic solder


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Re: lead free solder


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I usually do, adding some fresh solder to help it off.

Leonard



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Re: lead free solder
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   Do you leave a tiny bit of saturated braid on the end when you trim
it? It helps conduct the heat to the joint faster and minimizes heat
damage. I try to leave about half the width of the tip when I trim
solder wick, then dip it about 1/4 inch into fresh liquid RMA flux. I've
changed thousands of ICs this way with almost no damage to the PC
boards.

   The few that were damaged were mostly due to other causes, like some
idiot slamming a fist down on the bench while you're working because
they think you're ignoring them, or defective PC boards that have all
kinds of loose foils and pads.  I have to see if my digital camera will
do decent macro shots.  If it does, I'll put some pictures for the new
people on my website.  BTW, How's business?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
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Re: lead free solder



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CL-

One problem occurs if you use leaded solder on surface-mounted
components.  Lead amalgamates with the silver that is "fired" onto these
components, ruining their electrical connection.

I've read that a lead-contaminated solder iron can cause the problem
even if lead-free solder is used.  I've never heard of the opposite case
with lead-free solder.

To be safe, I keep two sets of equipment.

Fred

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Huh? What the devil are you talking about?

Re: lead free solder


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This is not new. Tektronix used to include a bit of silver bearing
solder with their scopes so you wouldn't ruin the plated ceramic
terminal strips if you changed out parts.

Jeff


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Re: lead free solder


On 5/25/2010 8:23 AM Jeffrey D Angus spake thus:

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 >
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Well, it was silver-*bearing*: still mixed with lead, no? (I assume this
is pre-RoHS.)


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Re: lead free solder


snipped-for-privacy@but.us.chickens says...
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I'm sure.  We keep a bunch of 3% Silver along with tin/lead for the
extra wetting it gets on some stuff.


Re: lead free solder



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So adding tin/lead solder to a silver component terminal turns the
connection into what, a non-conductive roofing shingle or something? I'm
pretty sure I would have heard from a customer or two if the thousands
of RoHS components I've soldered with 63/37 weren't conducting
electricity.

Re: lead free solder



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The metalurgical wisdom is that leaded and lead-free solders should not be
mixed in the same joint, as the mixing can, apparently, compromise the
long-term integrity of the joint. I don't know whereabouts in the world you
are, but across Europe, strictly speaking, it is actually illegal to use
leaded solder, or non RoHS components, to repair anything manufactured in
lead-free after implementation of the RoHS directive, which was June 2006 (I
think) in the UK. Prior to that time, some manufacturers, notably Sony, were
already manufacturing in lead-free, and insisting that their dealers used
*only* lead-free to effect repairs to all of their equipment, irrespective
of whether it was originally manufactured in lead-free or leaded solder.
This actually flew in the face of expert advice which recommended using only
the type of solder that the equipment was originally manufactured with.
There was no legal mandate to use lead-free solder for repairs to any
equipment manufactured prior to RoHS implementation, whether it was
manufactured with lead-free, or not. There is still no legal requirement to
use lead-free solder to repair any equipment originally built with leaded
solder.

As to whether lead-free damages tips, that's a bit of a grey one. If you are
using iron-clad tips, then yes, it does rot them much quicker than leaded
solder does. The reasons for this appear to be threefold. According to
Cooper Tools, who manufacture Weller soldering equipment, the composition of
lead-free solder has a tendency to 'leach' iron from the tip coating,
resulting in it failing quite quickly, and exposing the underlying copper,
which then rapidly burns away. Secondly, because lead-free solder does not
wet joints as well as leaded solder did, much more aggressive fluxes have to
be used, and again, these have a detrimental corrosive effect on the iron
tip coating. Thirdly, the temperatures required for lead-free hand soldering
are typically 30 deg C higher than those required by leaded solder. These
higher tip temperatures tend to exacerbate tip degradation. My experience
with Weller iron clad tips, would tend to bear out the contention that
lead-free solder destroys them much quicker than leaded did.

That said, a few months back, Antex changed their tips back to being what
looks like chrome plated, as they used to be 30 years back. This seems to
have produced a significant improvement in the life of their tips, and I
wonder if they have done it to combat the negative effects on tip life that
lead-free has given us.

As to mixing leaded and lead-free on the same tip, unless you are going to
keep completely separate irons burning all the time, I think that it's
pretty much unavoidable in a typical workshop environment, dealing with many
types and ages of equipment. If you keep a wet sponge on your iron's stand,
and get into the habit of giving the tip a wipe every time you pick the iron
up, then I don't think that any residual quantities of either type left on
the tip, will be enough to cause any problems.

Arfa



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