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lead free components in leaded process

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#51033

lead free components in leaded process | 13 July, 2007

Hello All.

Can the experts in the lead free field guide me to the articles / data confirming that it is OK to use lead free components in the normal "leaded" (Pb) SMT process. And also if any changes in the process would be required to be made.

Thanks for the help.

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#51042

lead free components in leaded process | 14 July, 2007

While you're waiting for others to respond, search the fine SMTnet Archives.

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#51046

lead free components in leaded process | 16 July, 2007

Yes, you can use lead-free parts in a leaded process. And the other is true as well, no-lead free parts in a leaded process.

BUT, you should not use leaded parts through a non-lead wave solder process and of course, your board will not be RoSH.

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#51048

lead free components in leaded process | 16 July, 2007

Yes you can use no-lead parts in a leaded process. Your solder joints will be weaker than they once were unless you change your solder paste. You can try to improve this by running a hotter reflow temp, but be careful since your flux was not designed to run at these higher temps. Gull wing QFPs are very fragile when running this way. If you have a wave solder process, they probably will come loose there. That was our experience.

Most solder paste mfgers make hybrid pastes that are designed just for this application. Our tests showed the solder joints were stronger than any other sample we tried, even no-lead. I would seriously suggest looking into this.

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#51051

lead free components in leaded process | 16 July, 2007

Ed: We agree with you that leadfree parts can be used with leaded paste.

We disagree that lead part can be used with leadfree paste. Here is link to a previous discussion here on SMTnet on the topic: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=30315

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#51052

lead free components in leaded process | 16 July, 2007

Thanks guys for the suggestions. But, what I am looking for is data, papers, articles to support this process of using lead free parts in leaded process.

Again thanks for any help that you can provide.

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#51054

lead free components in leaded process | 16 July, 2007

D. Hillman, et al., �The Impact of Reflowing a Pb free Solder Alloy Using a Tin/Lead Solder Alloy Reflow Profile on Solder Joint Integrity,� International Conference on Lead-free Soldering, CMAP, Toronto, Ontario, Canada, May 24-26, 2005, http://www.CMAP.org

Jasbir Bath, et al., �Reliability Evaluation of Lead-free SnAgCu PBGA676 Components using Tin-Lead and Lead-free SnAgCu solder paste,� Proceedings of 2005 SMTA International, Chicago, IL, http://www.smta.org.

Pan, et al., �Lead-free Soldering Backward Compatibility�, IPC/JEDEC Pb-free Conference, San Jose, 2006, http://www.ipc.org

Hope this helps, Patrick

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#51055

lead free components in leaded process | 16 July, 2007

#51103

lead free components in leaded process | 19 July, 2007

I took a Lead Free troubleshooting Class at SMTA in Chicago last September taught by Phil Zarrow.

He told us during that seminar that its not a good practice to cross contaminate Leaded and Lead Free components but IF it is necesary than using lead free parts on a leaded assembly is absolutely safe and will build quality PCBs.

The Pb-Free parts are rated for the higher temps necessary to get Pb-Free solder to reflow. Therefore the lower temps needed to reflow leaded paste will not damage the part.

Going the other direction can and will in many cases destroy a leaded component by reflowing it at Pb-Free liquidous temps. Not to mention it would ruin your Pb-Free assembly and then would not be RoHS compliant.

Chris

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#51112

lead free components in leaded process | 19 July, 2007

Chris,

To my knowledge the only difference between leaded and lead-free components is the termination plating. What has changed in the component design that makes them resistant to higher temperatures?

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#51122

lead free components in leaded process | 19 July, 2007

Phil is wrong. In the real world, we know that part mfgers have not changed every one of their parts to make them "high temp". They just changed the plating. Anyone who thinks otherwise, has never run a profile or touched a warm board coming out of a wave. In the real world you can solder these parts using a leaded paste and HASL board. The trick is to obtain proper max temperature without burning off your flux. We had a hell of time doing this until we followed Chunks advise and changed solder paste designed for this process. Now we have no problems. Listen to people who solder for a living, not lecture for a living. There is a BIG difference between the two!

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#51123

lead free components in leaded process | 19 July, 2007

Amen to that Hussman.

The new lead-free world is not based on science or environment it�s all about $$$$$.

And as I said before the promoters of lead-free care less about quality or reliability they just take this great opportunity to double their profits or commission checks hiding behind the RoHS buzz word.

Look at the latest developments, looks like we will wear the lead we once used on our boards. http://www.ban.org/ban_news/2007/documents/weidenhamer_ewastejewelrypreprint.pdf

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#51136

lead free components in leaded process | 20 July, 2007

In passives I dont know if anything changed at all other than the terminal plating.

As for Active components there has been much engineering done to allow for the extra heat needed to liquify say SAC305 or other lead free pastes without damage to the internal circuitry or the part packaging.

Manufacturers of both leaded and lead free parts still make mistakes at times. We have seen this to be true in many cases where I work since around 50% of our products ($36 mil a year in Pb-Free alone) here are Pb-free now. We've gotten some parts from suppliers (no names) where the potting for a leaded part was mistakenly used in the mfg. of a Pb-Free part. Then when we ran the assembly through the Vectra Pb-Free wave the potting oozed out of the housing and all over the pads it was on. NOT GOOD!

There is much more that goes into Pb_free parts (Active) than just the plating on the leads. Check out what I am saying and find out for yourself.

Have a great weekend!

Chris

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#51138

lead free components in leaded process | 20 July, 2007

I agree that it would be crazy to think that every part a company manufactured had to be re-engineered to allow for higher temps. Out of the question and I NEVER implied that at all.

What I said was that Zarrow told us that it was alright to use lead free parts on a leaded assembly and NOT the other way around. Doing that would contaminate your assembly and it wouldnt be RoHS compliant.

Now as far as your opinion on Zarrow versus your expertise. I am not doubting your talent or knowledge so dont take offense, but Phil is very well respected and knows his stuff. He teaches for a living and probably makes ten times what you or I make as techs or engineers.

No harm, no foul.....Thanks for the feedback though!

Chris

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#51143

lead free components in leaded process | 20 July, 2007

I agree with Chris. Not all but SOME components definitely had to change to be able to withstand higher heat. I would watch out for some plastic connectors, possibly some active components, and definitely many electrolytic caps. Older stock components of all of these, that are rated for leaded solder temps, can be sensitive to the new heat extremes that leadfree soldering will see. They can either warp, or ooze, or vent.

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#51148

lead free components in leaded process | 20 July, 2007

You know the old addage, "Those who can't do teach."

From my own experience with some of these "well-known consultants", they know lots of textbook theory, and..they speak in buzzwords and cliches (just like their magazine articles).

I'm not saying you can't LEARN anything from them. It's good to know theory too, but in most cases, consultants like this have no practical experience.

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