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August 30, 2017

Coating or encapsulating tin-lead solder joints?

I'm doing some SMT board work with only hand soldering stations... my quantities are very small.

I'm concerned with using the 60/40 tin/lead solder and I'm wondering if there is an acceptable way to coat or encapsulate the boards to limit, or eliminate, the dangers of the lead contained within the solder joints?

Or do I need to switch over to the lead free solder that is available?



J. H.

Experts Comments

The dangers of lead free solder do not come into play unless someone is touching the solder joints or in the Waste stream. As you are hand soldering your operators should be using protective gear (gloves) while holding the solder wire.

Conformal coating will help the waste stream as it will prevent water from eroding the lead into the ground water. Conformal Coating however will not get around the RoHS requirements which if you are shipping the material into Europe or any country with RoHS legislation you will still need to have lead free assembly.

Most companies that have gone lead free have moved to SAC305 which has 3 percent Silver and 0.5 percent Copper.

The SAC 305 is a good replacement for Tin Lead Assemblies and most suppliers should have this alloy in stock.

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Doug Dixon
Global Marketing Director
Henkel Electronics
Mr. Dixon has been in the electronics field for over twenty years and is the Global Marketing Director with the electronics group of Henkel. Prior to joining Henkel, he worked for Raytheon, Camalot Systems, and Universal Instruments.

Thank you for an interesting question. The Surface Mount solder joints can be created using either Leaded solder or Lead-Free solder, the option is up to you. If the product is going to Europe then the EU RoHS Directive requires all incoming products to be manufactured with lead-free materials.

The intent of the RoHS directive is to eliminate Lead from electronic products. Conceptually this is to theoretically prevent the leaching of Lead from the Tin/Lead, into the local environment as the units are being disposed in land fill dumps.

Coating the product with any type of material will not prevent this from happening as the Lead still exist within the product. Coated or uncoated, it is the elimination of Lead which is important and needs to be considered when designing and building any electronic products.

The exposure to Lead from handling the solder does exist and can be prevented or eliminated with proper hygiene, such as the washing of the hands.

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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.

There are conformal coating materials that are designed to protect solder joints from corrosion in harsh environments. They were not designed to protect from lead contamination, however, the may help.

Coating or encapsulating a part containing lead may help prevent contamination; however, it does little to meet any of the global lead free initiatives.

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Alan Lewis
Director of Application Engineering
Asymtek
Mr. Lewis worked for The Aerospace Corporation for 6 years before joining Asymtek in 1993. He holds multiple patents in dispensing technology for electronics assembly and packaging. He has a Master's Degree in Mechanical Engineering from University of Missouri-Rolla.
NOTE: Mr. Lewis is no longer working at Asymtek.

If you are not exporting your product, or if you are exempt then you do not need to do anything.

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Edward Zamborsky
Regional Sales Manager
OK International Inc.
Mr. Zamborsky serves as one of OK's technology advisers to the Product Development group. Ed has authored articles and papers on topics such as; Low Volume SMT Assembly, Solder Fume Extraction, SMT Rework, BGA Rework, Lead Free Hand Soldering, Lead Free Visual Inspection and Lead Free Array Rework.
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