It seems clear that reflow temperatures for virtually all the lead free solder options are increasing dramatically. What are the implications for my current cleaning processes?

Great question. Typically there are three different “genres” of cleaning in the electronics assembly industry today: board cleaning, stencils & misprints, and hand, touch up cleaning.

It is important to bear in mind, that with more than a dozen solder technology companies active in the global market broad generalizations can be misleading.

It is safe to say that many of the older, time-honored technologies that have been cleaning RMA tin-lead materials for years will have real challenges with many of the new lead free materials.

The higher temperatures of the lead free reflow & wave processes will make the residues more difficult to remove ~ no ambiguity here. So board cleaning post reflow & wave will at best be more challenging. Your existing materials will continue to be effective in some cases, mostly you will need to consider new technology. It is also important to recognize the significant changes going on with these new soldering materials. As the old saw goes, “these are not your father (or mother’s) solder pastes and fluxes. The technology leaders are taking full advantage of modern polymer technology to deliver the critical performance characteristics their customers (that would be you) demand.

Often, these new technologies must be cleaned with equally modern cleaning products developed in the last few years. Quality cleaning suppliers are doing the lab work to provide benchmark data on all these new materials. Keep in mind those 10+ solder manufacturers have many products available, so be sure your supplier has looked at several dozen materials recently. Otherwise, they are just guessing.

Regarding stencils & misprints, the picture is a bit brighter. Stencil cleaning should not be significantly affected. Your current process should continue to work. A-side misprints should be similar to stencil, just fine. B-side misprints will be similar to fully assembled boards, discuss your process in detail with your current supplier to make sure their products have been tested on the modern solder materials you are considering.

Touch up and hand cleaning will most likely fall somewhere in between. Often tip temperatures are far in excess of typical reflow profiles, so they may not actually increase very much after the move to lead free. Once again review the data available from your suppliers, and validate that data in your own process.

So you can see, for those that are cleaning, there will most likely be some process adjustments required that may include changes in the cleaning materials currently used.

Now, for those who don’t understand question #1, Why on earth would any ISO9000 quality assembly operation clean their products?

Once upon a time, back in the 80’s and part of the 90’s almost all electronic assemblies were cleaned. Granted some of that cleaning was straight water cleaning O/A materials, but the lion’s share was some sort of solvent cleaning mostly RMA materials.

When no clean made its debut in the mid 90’s the question began to change from How do you clean assemblies? to Do you need to clean your assemblies?

It was a pivotal question, because many high reliability devices have continued to be cleaned ever since. However, we also know that most electronic assemblies are not necessarily high reliability devices, and the vast majority of them have not been cleaned for some time.