Using rosh solder to repair units made Pre rosh?

[pucho812]

I can't find a definitive answer on this.  I searched google but get mixed opinions.

Can you mix solder types?
For example if I don't have lead solder can I use rosh  compliant solder in a unit made with lead solder when doing a repair?  Aside from higher melting temps and such will there be any difference?  Will it bond any differently?

 

[joaquins]

  You should clean the previous solder anyway, I guess the remaining thin layer shouldn't be such a problem. If you are adding a big blob over another big blob of a different metal you might have a problem, but would you?

  I don't have experience as in this world we still use almost as much lead as tin... Usually within 20%. It was usual to do it backwards, as first lead free  GPUs started to fail and reworking them with leaded fixed them, I guess it won't be a problem for your case.

JS

 

[AusTex64]

I understand that ROHS makes a provision for repair of pre-ROHS gear, that it's acceptable to use non  ROHS parts in the course of repair, including the use of leaded solder.

 

[CJ]

soldering lead free pc boards with leaded solder can be a hassle,

so we suck out the non lead stuff and fill it up with good ol kester 44 hi octane because we are going to get hit with a meteorite pretty soon anyway, 

 

[Rob Flinn]

I would guess nobody has ever had an imspector come round to check they used ROHS solder on anything.

 

[pucho812]

well this came handed down from on of the design guys,  can't mix the two. I've never had a problem but I trust his word and unfortunately he works remotely and is hard to get a hold of so I can't get an explanation of why?

I have yet to see any issues, but just wondering. Maybe years down the road the joints won't be as nice but so far so good.

 

[Andy Peters]

well this came handed down from on of the design guys,  can't mix the two. I've never had a problem but I trust his word and unfortunately he works remotely and is hard to get a hold of so I can't get an explanation of why?

The "why" of not mixing lead-based and lead-free solder is simple -- it's the metallurgy.

When doing proper re-work, you remove all of the old solder anyway.

-a

 

[JohnRoberts]

It is probably good discipline to get used to using lead free solder.
=======

I will often apply some fresh lead based solder when doing minor rework on my lead free SMD PC boards (the flux seems more active).

I have both types of solder on my bench and use lead free when practical (for the tiny fraction I ship outside the US).

The old-school solder looks like it works better, but this is purely anecdotal and not scientific (perhaps a personal subjective bias from decades of using leaded solder).

JR

 

[pucho812]

I am used to lead free as I am leaded.  I do have both on my bench. Maybe the practice of not mixing  the two is an an old wives tail....

 

[CJ]

well you want your solder joints to look good in case the customer gets snoopy,

using lead solder on top of unleaded usually forms this textured and discolored mess,

probably nothing wrong electrically but kind of gross looking,

lead free is great if you wave solder, the boards get covered with a good coat of flux, and the solder is at the right temp, and it looks pretty much the same as leaded, but when you go to do touch up, it always looks worse than the wave job,

if you do not drive a car you should be allowed to use leaded solder,

 

[pucho812]

Leaded is still o.k. in the U.S.A. not for the rest of the world.