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.

1. 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.
2. 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.

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.

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.

If the carrier can hold the heat the no problem to use the same carrier for lead free and leaded allow.

The risk of contermination from the carrier material.

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.

I agree with Brian Kerr. The only "clean path" to proove no risk of contamination is to use seperate pallets.

1. Use the correct solvent to clean the flux.This information should be available from your flux supplier, or contact Zectron (www.zestron.com).
2. The pallet should be cleaned ultrasonically. Zestron also offers this equipment.