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Lead manufacturing to lead free transisition

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#47870

Lead manufacturing to lead free transisition | 21 February, 2007

Hi all,

What are some of the must do, cannot go without changes to our process and equipment before we adopt a lead free process? Would we have to completely change out our ovens? I thought I read that using old ovens was a no-no. I just began scratching the surface on this subject. Thanks for any input.

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#47874

Lead manufacturing to lead free transisition | 21 February, 2007

Hi, Bill,

Lead-free solder and paste manufacturers will be a great resource for you during the transition; they've tested their products extensively, and their application groups have been able to help me through the biggest changes.

There are a few things you'll need to consider as you're transitioning. The biggest consideration is that lead-free solder/paste requires higher reflow temperatures than tin-lead solder.

1. Reflow Oven. Sounds like you've already looked at this. Do you have to jump into a new oven right away?? Probably not...but, it'll depend on the boards you're processing, and the capabilities of your current ovens. If you have older 5-zone or less ovens, with blowers not capable of running to 350 degrees, you could encounter issues. This doesn't mean you can't run low heat-load boards (we did it with a 15 year old 4-zone heller); just means that some higher heat-load boards will not solder well.

The additional zones give you, of course, more control over the process window. The TAL window is tighter with lead-free pastes than it was with tin-lead pastes.

2. Wave solder. This is completely dependent on the types of assemblies that you're running. To date, I haven't invested in a pb-free wave, because I haven't run enough volume to warrant it. I'm running with a pb-free solder pot. Existing wave machines can be upgraded to lead-free capabilities. The pot is coated with a special substance that prevents the pb-free solder from corroding it; and the lines have to be cleaned out. If you're completely converting to lead-free, this might be a more economical method than buying a new lead-free machine.

3. Board finish. We've experienced the best results from ENIG finishes. I haven't had a lot of luck with white-tin finishes to date. However, your mileage may vary.

4. Solderer skills. This is one that can be tough to overcome, depending on the attitudes of your personnel. Lead-free solder joints look different than tin-lead joints. Compared to the old standards, they resemble cold-solder joints. I've had a heck of a time convincing people that IPC accepts lead-free solder joints that look like this. If you can provide lead-free solder training for your people, it'd be beneficial. I've also had a heck of a time getting people to turn their irons down. Lead-free does flow at a higher temperature than tin-lead solder, but my people are turning their irons up to 800 degrees in some instances, and that's not necessary.

5. Soldering equipment. Because of the higher temperatures, and the lack of lead, the lead-free solder tends to corrode soldering iron tips much faster than tin-lead solder ever did. This caught me by surprise; the additional expense of replacement tips, and the time-frames involved in replacing the tips.

cheers, ..rob

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#47878

Lead manufacturing to lead free transisition | 21 February, 2007

you may need to change ovens since you were running lead in there. you probbly have some lead dust still blowing around in there

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Bernard Mulcahy

#47898

Lead manufacturing to lead free transisition | 22 February, 2007

Hi Larry,

Changing an oven because of Lead-dust ???

What your experience in this area?

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#47993

Lead manufacturing to lead free transisition | 27 February, 2007

Larry has lots of experience, if you have been around the forum for a while you may remember some of his other suggestions.

Now I wish I had asked the question before jumping in to Pb-free 1 1/2 years ago. We've been using the same ovens to run both Pb and Pb-free this whole time!

The boss is going to flip when I tell him we need a couple more ovens.

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#47998

Lead manufacturing to lead free transisition | 27 February, 2007

hahaha! LISTEN, everyone knows that oven get dirty. They need periodic cleaning. So if you run lead boards thru your oven you will get lead dust and residue in you're oven. If you want to be truely lead free you need to get all the lead outta of your ovens. SO how can you do that? You'll never get it all, so that would mean there is lead still in your process which could get to the baord and your customers would not like that or even chance it happening in the beginineg would they? Maybe you guys rubbed a potatoe inside your ovens to get the lead! Haha! Now thats some funny stuff there rubbing a potatoe around to get rid of the lead.

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RDR

#47999

Lead manufacturing to lead free transisition | 27 February, 2007

Boy it is good to see the wave master back in action! I mean really guys, is Larry the only one here who knows that the lead turns into vapor in the oven and then in the cooling zones it falls back onto the board and creates the solder joints?

P.S. Larry, keep up the good work, you make my job so much easier. Process issues are not so serious when you are laughing your butt off!!!

Russ

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#48001

Lead manufacturing to lead free transisition | 27 February, 2007

Thanks Russ. Everyone knows that when you clean your wave you wear a dust mask. Well that tells ya the lead is flying around. So same goes fr your oven. Hot solder paste turns into the lead. And like a wave it is very hot. Hot stuff vaporizes like in youre ovens. Thus the oven has lead deposites that make it risky to run run a no leaded rpoduct through. Then again Russ, some of these "enigneers' feel that rubbin spuds thru wave will clean right up! What kind a patatoe would they use? A RoHus patatoe? Get it - that's some funny stuff there!

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#48002

Lead manufacturing to lead free transisition | 27 February, 2007

How's the weather over in Idaho, eh, Larry?

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#48004

Lead manufacturing to lead free transisition | 27 February, 2007

Wow, how did you know?

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#48006

Lead manufacturing to lead free transisition | 27 February, 2007

I don't know whether to laugh or cry.

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#48011

Lead manufacturing to lead free transisition | 27 February, 2007

Actually the weather here is pretty fair for this time of year. This weekend we plan to do some squirrel hunting since its so nice and they'll be out. Hard to kill but easy to track.

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#48022

Lead manufacturing to lead free transisition | 27 February, 2007

WML Excuse us for confusing things with facts, but lead vaporizes around >1300*C. We didn't realize that components and boards would stand temperatures as high as that.

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KEN

#48024

Lead manufacturing to lead free transisition | 27 February, 2007

Hmmm.... I had Intel survey my process on a mixed alloy line for 2 days. They periodically removed boards from all stations on the line (including post reflow). Boards were "crushed" and spearated into constituent plastic, ceramic and metals. All samples passed with lead below 1K PPM.

I had no idea they were fudging their test results to sell more mother boards in europe? Thanks Larry for opening my eyes!

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#48031

Lead manufacturing to lead free transisition | 28 February, 2007

you mean to tell us you actually know who larry is, Steve? So he would be an actual real living human beeing, that's quiete frightening!

Well, I dont work in Idaho, so I guess I have nothing to worry about.

Not excuse me as I go sniff some more lead-dust out of our leadfree oven.

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J.R.

#48101

Lead manufacturing to lead free transisition | 1 March, 2007

Let's talk pin holes and blow holes. I've been here since the transistion of leaded to lead-free process started for our company and we purchased a wave machine just to keep up with our lead-free orders. we put out 500-1000 boards a day both leaded and lead-free combined. when one day I got a batch of boards that for the life of me i could not get rid of the pin holes and blow holes. i went from one extreme to the other on temps,speeds,conveyor angles and every thing else i could think of. Nothing help. after falling back on all my notes and documentation every thing pointed to the board and the epoxy laminate being uncured. and sure enough after some long and not so pleasant conversations with the board house I got them to addmit that they had reduced the curing time process and it was thier fault. I would love to tell the world which board house this is because my company just got another shippment of 650 boards in last week from the same manufacture and we are having the same problems, but for leagal reasons I'll leave their name out. so just to save some of you from some very long nights and major headaches, when you start to see excessive amounts of blow hole and pin holes, it could be from too low of preheats but if that doesn't help after ajusting start looking at the board it self. one easy way to tell this is after it's been waved is when your touch-up people have the solder joint start popping and they can't fill the hole and they tell " I keep adding more solder but it won't fill the hole". Stop right there and call up your board house.

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