|Ask the Experts|
December 15, 2017
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?
|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.
Vice President, Technical Director
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.
CEO & Managing Partner
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.
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.
Executive Vice President and CEO
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.
General Manager - Electronic Assembly Americas
|Submit A Comment|
Free Newsletter Subscription
Circuitnet is built for professionals who bear the responsibility of looking ahead, imagining the future, and preparing for it.
Insert Your Email Address