Leaded to Lead-Free Wave Solder Pallets

We have many assemblies moving from leaded to lead free solder. The design change is not changing the PCB layout. Our wave solder pallets are made from Durostone material which can take the increased heat. Can we use the same wave solder pallets, or should they be replaced? Our concern is contamination from residue on the pallets from earlier builds using leaded solder.

D. G.

Expert Panel Responses

I would recommend that you use separate pallets and identify them as such. Tin/lead solder particles and dross can be picked up by the pallet and transferred to your lead free pot or even to the lead free product. Lead can then build up in the solder pot and there wouldbe considerable cost in relpacing the contents of the pot. In addition, it would also be wise to have two sets of maintenance tools to avoid any other potential sources ofcross-contamination.

Bryan Kerr
Principal Engineer - CMA Lab
BAE Systems

Bryan Kerr has 35 years experience in providing technical support to PEC assembly manufacturing. His experience ranges from analysis of materials and components to troubleshooting and optimizing, selecting reflow, cleaning, coating and other associated processes.

Without a doubt, re-use the pallets. Save yourself some money. I'm sure there are some pallet manufacturers who will suggest that there may be some chance of cross-contamination, but the quantity is so small as to be negligible, if any. If in doubt, clean the pallets with any of the very good pallet and oven cleaners on the market today, like the Reflow Oven Cleaner from MicroCare.

Mike Jones
Vice President
Micro Care

Mr. Jones is an electronics cleaning and stencil printing specialist. Averaging over one hundred days a year on the road, Mike visits SMT production sites and circuit board repair facilities in every corner of the globe, helping engineers and technicians work through the complex trade-offs today's demanding electronics require.

If the high temperature (350c) Durostone pallets are in good shape and can be cleaned thoroughly, they should be able to go from the lead, to lead free solder with little or no issues. The material does resist solder contamination. You should not, however, continue to go back and forth between the two. This eventually might cause cross contamination. In the case of a single switchover, they should be ok if cleaned properly. I appreciate the opportunity to reply to your question. Please feel free to contact me at any time.

Rick Fiacco
Global Director of Sales
APS Novastar

Rick Fiacco has 30 years experience in Interconnect Industry with a focus on Product Development/Marketing and Business Development. Fiacco holds two patents in cable and connectors. Presently he is responsible for all solder equipment at APS Novastar.

I have polled a few folks who did the change over and I also contacted a well known tooling company that supplies pallets throughout the industry. The response overwhelmingly is that "Only you can make that determination". However a few technical notes of interest did surface in my investigation.

Have you been washing the pallets on a regular schedule?
1. Provided they are in good shape and not ragged on the bottom you should be fine for a one time change over.
2. If not you should consider washing in part to protect your investment and to avoid any potential defects, etc. on your PCB's.
3. A cleaner process either spray or ultrasonic can easily be adopted just insure you select a wash chemistry that is compatible to the laminate and the aluminum supports and/or fixtures that may be present on your pallets. Repetitive washing in a highly alkaline saponifier like solution will wreak havoc on the aluminum.
You did mention you currently use pallets with Durastone type material.
1. The Durastone is an epoxy based laminate. I was advised that if you have the black material then you may experience rapid delaminating due to the more highly active components in the newer lead free wave flux formulas. The industry is transitioning to a Durapol laminate. This is material is more resilient to the newer active fluxes and stands up well to repetitive higher process temperatures. They claim a life span of 10,000 cycles over the wave with Durapol.

At a worse case scenario it looks like you will likely have to phase in all new pallets going forward. Keep close watch on the integrity of your existing pallets. If you wish to discuss this further do not hesitate to call me.

Charlie Pitarys
Technical Expert Sales Support
Kyzen Corporation

Charlie Pitarys has over thirty years of industry experience and has been with KYZEN for twenty-one years. Charlie is a former Marine and a retired Sargent First Class in the Army Reserves. His previous employers include Hollis and Electrovert. Charlie continues to use his expertise on cleaning processes and machine mechanics to help KYZEN customers and partners improve their cleaning operations.

I do not see an issue with using the samepallets, as long as you've clean them thoroughly. Washing them after each usewill also help with the regular maintenance of the pallets (removing the fluxand solder residues). It has to be said that sharing the pallets for bothleaded and lead free processes is not a healthy practice - so continuingswitching the process has to be avoided.Do not forget to mark them accordingly too.

Georgian Simion
Engineering and Operations Management
Independent Consultant

Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com.

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