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Lead Free and Leaded Process Mix

#35163

Lead Free and Leaded Process Mix | 24 June, 2005

Hi Everyone,

I need everybodys help on this one. We are a company that suppose to be exempt from the Lead-Free world and we were happy untill we find out alot of the Components manufacturers will change their parts to Lead-Free but not their part numbers. This is a big issue for us since we use almost 1945 components and we were not prepared for this. The question is the following. If we received Lead-Free components insted of leaded and we are still running on the old process, will I have soldering issues on the SMT and Thru-hole side of it. Also, If the parts adhere fine can this have the posibillity of failling in the near future or fail on the field. AS I mentioned before we were not prepared for this and I dont know much about Lead-Free. Is there anybody out there running Lead-Free components and regular components mixed trough the same process as before? And if so, what has been your experience?

Please help!!!!!!!!!!!

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Bob R.

#35179

Lead Free and Leaded Process Mix | 27 June, 2005

We've all been soldering Pb free parts for a couple decades. All your surface mount capacitors have probably had a Sn finish for years.

Whenever one of our parts with a SnPb finish converts for Pb free we have the manufacturing site do a small build and inspect the joints against IPC-610 workmanship standards. 99% of the time we have no problems. The few times we've had a problem we've found one of two things: either the site was running a cool profile (around 210C peak) or the supplier messed up the plating. For the first issue we just ask the site to up their peak reflow temp to where they should have been running in the first place. Usually anything above 215C does the trick, sometimes 220C. We allow up to 230C since that's what most of our non-Pb free parts (all the other parts on the board) have been qualified to. The supplier issues have typically been due to the switch to Pb free coinciding with a switch to a low cost manufacturing site leading to poor control of the plating process. In these cases it wasn't the Pb free finish that caused the problem, just poor process control at the new site.

The only real problem we're seeing is some suppliers trying to use bismuth. That's a big no-no in a SnPb process and we won't accept those parts.

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#35183

Lead Free and Leaded Process Mix | 27 June, 2005

Thank's for the information Bob. I have another question, at the moment my peak reflow is at 218c, this means I am above the 210c a lot of companies run off. If I am building boards using SN63/37 solder paste with lead on my process, and using lead free components is there a posibility that I would have continuity issues or the part might fall down.

Reagrds!

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Bob R.

#35189

Lead Free and Leaded Process Mix | 27 June, 2005

If you visually inspect the solder joints of the first dozen or so boards with the Pb free parts and you're meeting workmanship standards then I wouldn't worry about it. When we started getting the first barrage of Pb free parts a couple years ago we would cross-section a few in addition to visual inspection. We were getting strong joints with good intermetallic formation. At 218C you probably won't see any issues and if you do you've still got room to increase the temp. If you get to around 225C and you're still not seeing good joints then it's time to look hard at the components themselves to make sure the finish is properly applied with good solderability. We've had a few issues with suppliers getting the plating too thin, but for the most part having parts switch to Pb free has been painless.

One thing we've had to fight is a communication issue with our remote plants. Component suppliers will tell our manufacturing sites that they need to crank up their reflow ovens to 235-250C. We can't allow that because not all of the components on the board are qualified to those temperatures (at least at their current MSL level). We then have to explain to the sites that the supplier is confusing Pb free parts with a total Pb free process. The suppliers seem to think that everyone who's using their parts magically switched to Pb free solder when the supplier changed to a Pb free surface finish.

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#35191

Lead Free and Leaded Process Mix | 27 June, 2005

We've talked about this previously. Search the fine SMTnet Archives for additional background. For instance: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=30307)

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Jason Fullerton

#35389

Lead Free and Leaded Process Mix | 8 July, 2005

"The only real problem we're seeing is some suppliers trying to use bismuth. That's a big no-no in a SnPb process and we won't accept those parts."

Yes and no. Since the SnPbBi tertiary alloy melts at 96 degC, any product rated for storage above that point should disallow any components with a bismuth finish used with leaded solders. However, if you are like me, and your parts are only rated for storage up to 85 degC I am allowing them on a case by case basis.

Generally, the bismuth parts I've encountered are fine pitch connectors with primary use in Japan, so they are relatively rare. The bismuth is supposed to reduce the probability of tin whiskering.

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#35608

Lead Free and Leaded Process Mix | 18 July, 2005

Francisco, You need to be concerned about "lead-free" BGAs. The SAC balls will not reflow at at standard tin-lead process temps. I have seen many examples where this has been a very big problem. In once case the BGAs just poped-off when the board was flexed!

Joe

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Rob

#35617

Lead Free and Leaded Process Mix | 19 July, 2005

Hi,

On a semi related front, part of our company is a distributor (I'm not going to say who, coz that would be sneaky advertising), and on all components shipped we've added the follwing to the label:

ROHS Compliancy Status(Lead free & plastics etc) PBT (Peak Body Temp - i.e. 250C) MSD level

Is there anything else you lot would like to see on components when they arrive?

Cheers,

Rob.

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GS

#35621

Lead Free and Leaded Process Mix | 19 July, 2005

Yes Rob,

I would like to know the type of metal finisching like JST097 or IPC-1066 or IEC .... suggest to do. I would like to avoid i.e. to get Bismuth finish on components terminals that I still have to solder with alloy containing Pb.

Also to have consistent labelling among all components suppliers we receive.

Tnks

GS

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Rob

#35623

Lead Free and Leaded Process Mix | 19 July, 2005

Hi GS,

Thanks for responding - looks like we already put end termination coating on the label - we just call it "second level interconnect"

There is a specimen label at:

http://www.anglia.com/quality/labels.pdf

Regarding standardising labels accross the field, I think it will only happen if customers demand it from component suppliers. (I don't think they're an altruistic enough bunch to sit down together & do it unless really pushed)

Cheers,

Rob.

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GS

#35625

Lead Free and Leaded Process Mix | 19 July, 2005

any thanks Rob,

te specimen label Anglia is some thing complete and very helpful example.

Hope Comp Suppliers will take care about the needs of Users (mainly if they are small EMS). To know how the terminals/leads are metal finisched is important for those who have to assembly both processes Lead and Lead-Free mainly during the transition period to Rohs compliance.

Best Regards GS

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