Cleaning Tin-lead and Lead-free Boards

We are creating our first lead-free SMT assembly line and have new equipment for this area and expect low volume to start. We had not planned on buying new board cleaning equipment. Can we use the same cleaning equipment for tin-lead and lead-free boards?

T.A.

Expert Panel Responses

Can the same equipment be used to clean Lead-free types of fluxes? The answer is yes, but the process parameters will have to be checked to make sure the residues are in fact removed with the new chemical lead-free process. The cleaning process will have to be evaluated to make sure the soak time, rinse time and dry time are defined to clean off the new flux residues. Cleaning tests could include either the dynamic or static ionic cleanliness tester, but I would recommend using a Surface Insulation Resistance Test (SIR) to verify the goodness of the cleaning process in removing the processed flux residues.

Leo Lambert
Vice President, Technical Director
EPTAC Corporation

At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.

I think the cleaning guys will say no, but you can run a number of tests to confirm the effectiveness of the old equipment. They would include ion chromatography per IPC-TM-650, a surface insulation resistance (SIR) / electrochemical migration (ECM) type test on a test coupon (such as IPC-B-25), and a final confirmation through temperature/humidity testing of the actual product. With product testing, I often recommend a modified THB test, consisting of two conditions (40/93 and 65/88) for three to five days each. Of course, if you conformally coat or this is a risk of condensation, different tests are required.

Dr. Craig D. Hillman
CEO & Managing Partner
DfR Solutions

Dr. Hillman's specialties include best practices in Design for Reliability, strategies for transitioning to Pb-free, supplier qualification, passive component technology and printed board failure mechanisms.

The answer depends entirely on the specific cleaning system you are currently using. Lead free is more difficult to clean than lead alloys. To overcome the increased difficulty, more cleaning power is utilized. Power is defined as "impact pressure", "water particle diffusion angles", "heater wattage", etc. Older defluxing systems most likely lack sufficient power to handle the increased "metal salts" created by the elevated temperature profiles required by most lead free alloys. The result may be increased white residue and flux left on the board's surface. Additionally, some chemical companies have recently introduced advanced chemical formulations specifically designed for lead-free residue removal. These advanced chemicals may or may not be compatible with older defluxing systems. Check with the equipment's manufacturer to brand-specific advice.

Mike Konrad
President
Aqueous Technologies

Mr. Konrad has been in the electronic assembly equipment industry since 1985. He is founder and CEO of Aqueous Technologies Corporation, a manufacturer of automatic de-fluxing equipment, chemicals, and cleanliness testing systems.

You can use the same equipment for eutectic and lead free, given that the chemistry you choose has the capability of separating tin-organic compounds from the cleaning bath. We recently published a paper on exactly this problem, and you can find that on our website.

Dr. Harald Wack
Executive Vice President and CEO
Zestron America

Harald Wack hsa a doctoral degree in organic chemistry, an author of 10+ published scientific articles in organic chemistry as well as numerous publications within the electronics industry. He is currently the Executive Vice President and CEO of Zestron America.

The only thing that would force a user into unique cleaners for leaded and lead-free assemblies would be if the lead from the leaded cleaning process could somehow contaminate the lead-free assemblies. Since the level of lead leached into the water is extremely low (and could be filtered out), there should be no issue with using the same cleaning equipment for leaded and lead-free assemblies. There is no chance that lead contamination from the cleaning process could elevate a lead-free board up to the 0.1% RoHS limit for lead-free assemblies.

Brian Smith
General Manager - Electronic Assembly Americas
DEK International

Mr. Smith has been supporting customers in the electronics assembly industry since 1994. His expertise is focused on solder paste printing and reducing soldering defects. He holds a BS in Chemical Engineering and an MBA in Marketing. He has authored several papers in trade magazines and at industry conferences. He is an SMTA Certified Process Engineer.

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