Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Changing a wave over to lead free

Views: 1254

Grant

#41619

Changing a wave over to lead free | 18 May, 2006

Hi,

We are about to change our wave over to lead free solder, and it's a Soltec Deltawave, which uses about 750 KG of solder.

Our supplier is recommending we change the bath over, however that seems a bit extreme. They are concerned we won't get rid of all the old solder.

If we need to reduce contamination below .1% of lead, does that mean I just need to be sure I have less than 750 Grams of solder and I am ok. Then only 63% of the 750 Grams really has the lead in it.

It seems like a lot, and we should be able to get rid of almost all of the old solder, with only a teaspoon amount still there after we clean it.

So with that in mind, does changing the bath seem a bit over the top to everyone? Who's done this?

Regards,

Grant

reply »

Mike Dunn

#41626

Changing a wave over to lead free | 18 May, 2006

What is your bath made out of?

reply »


RDR

#41632

Changing a wave over to lead free | 18 May, 2006

Are you talking a tin purge here?

reply »

#41667

Changing a wave over to lead free | 18 May, 2006

Hi,

The bath is titanium coated, and the machine is only 2 years old, and was designed for lead free, so we know we don't need to change anything.

The reason the supplier gave for suggesting the bath change is "other companies are doing it" and it's the easiest way to make sure the bath is not contaminated with left over lead based solder.

Their other suggestion is to fill the bath with lead free, and then empty it, and fill it again, as a way to cleanse it.

But based on my calculations we would need to have left about 1 KG of lead solder for there to be enough lead based solder remaining in the drained pot to be an issue once it's filled with lead free solder. But we would have much less than that, as we should be able to get almost all the old solder out of the put.

Regards,

Grant

reply »

#41676

Changing a wave over to lead free | 18 May, 2006

We did a tin bath on ours but it was provided for free by Nihon Superior so that is a no-brainer. It was better than taking a risk of having to dump the pot. If you cant get a free tin bath, then you should probably go ahead and fill it half way or so with your solder of choice and have an analysis done, if your OK, keep filling, if not drain it and you should be ok then.

The tin bath we did only filled the pot half way. We have a Vectra and its pretty hard to get every bit of solder out of the impellers and wave ducts on that machine to a level that I would feel comfortable just filling it back up without the tin bath.

reply »

#41677

Changing a wave over to lead free | 18 May, 2006

I don't have any experinence with this, but my concern is that you are limiting the amount of contamination your pot can absorb before you ever run a board through. What I mean is that even if you are able to drain all but about a kg of the old solder out, after you fill your pot you will be right at the limit for contamination. If a little more lead slips in somehow, your whole pot is a loss. I'd go with the tin flush if at all possible.

reply »

#41679

Changing a wave over to lead free | 18 May, 2006

Hi,

The tin flush is a good idea, and better than the suppliers suggestion of filling with lead-free solder which is much more expensive.

I guess we won't be leaving a KG of solder in the bath, but based on your experience, how much remaining solder is still in the bath after draining, as from our bath I don't think it would be very much? I am sure we should be able to get almost everything, as it does not look that complex.

Also, what flux do people use for no clean after changing to lead free, is the same flux ok?

Thanks for the help guys, I don't know where I would be without this community!

Regards,

Grant

reply »

#41681

Changing a wave over to lead free | 18 May, 2006

Hi,

One other thing, and it's weird to be replying to myself, but what's the melting point of tin? Will the wave do that ok? I guess so, if you guys have done it, but just wondering about it.

Regards,

Grant

reply »

Wizard of Oz Tin Man

#41683

Changing a wave over to lead free | 18 May, 2006

"Solder alloy compositions are numerous but the most important are still the tin lead solders which were used by the Romans. Tin melts at around 232�C and lead at about 327�C in the combination 62Sn 38Pb the resulting alloy melts at 183�C. This composition is known as the eutectic. Solders used in electronics account for a significant proportion of tin consumption. Lead free plumbing solder is often tin with about 0.5% copper although many other compositions have been developed."

http://www.carnmetl.demon.co.uk/tin.htm

reply »

Reflow Oven

Used SMT machines