RoHS
By Ed Kanegsberg
The RoHS deadline has arrived! What does this mean?
RoHS is an acronym for “Restriction
of the use of certain Hazardous Substances”, a directive of the European
Union (EU) that restricts the use of six substances in most electrical
and electronic equipment placed on the market after 1st July 2006. Although
the
primary focus in the electronics industry has been on elimination of lead
from solders, the RoHS directive applications using Cadmium (Cd), mercury
(Hg), hexavalent chromium (Cr (VI)), polybrominated biphenyls (PBBs) and
polybrominated diphenyl ethers (PBDEs) as well as lead (Pb).
RoHS is a European directive. I’m in the US. Why does it
affect me?
If you sell any equipment in any of the EU states or are an OEM of equipment
that might be incorporated into systems sold in the EU, such equipment
will need to comply with RoHS. However, even if your market is totally
within
the US, you will be affected. By January 1, 2007, some electronics
sold in California will need to be RoHS compliant (please
see accompanying article). Many other states and
countries have either enacted or are considering similar legislation.
How Does RoHS Affect Cleaning?
The greatest impact of RoHS on electronic manufacturing is the conversion
to lead-free solder. As with any process change, if the materials
of construction change, the processes, including cleaning, need to adapt
to new conditions.
Lead-free solder technology is still evolving. Some aspects of the technology that are evolving include solders, fluxes and reflow temperatures. These changing parameters mean that there will also need to be changes in both cleaning agents and processes. These modifications are likely to be application-specific. Other electronics assembly processes that will impact lead-free conversion include flipchip, BGA, and miniaturization. It is not sufficient just to adopt lead free solder. It is necessary to consider the total impact of all process changes.
Manufacturers worry about process change. Cleaning is costly due
to capital outlay, process maintenance and labor requirements.
Small changes
can
impact performance. In addition there are regulatory implications
including ambiguous,
conflicting rules. Employee safety/liability is always an issue.
The manufacture needs a robust process to maintain or improve customer
satisfaction and
for improved profitability.
Cleaning with Lead-free Solders
Some testing by aqueous cleaning suppliers has been reported for
cleaning lead-free solders. “No-clean” fluxes tend to leave residue if
not cleaned [Bivens et. al (2000), Lee & Bixenman (2001)]. They found
that the fluxes clean well with saponified aqueous processes but are not
well cleaned by solvent degreasing.
Some issues with newer fluxes are that a higher reflow temperature
has a higher oxidation rate, greater flux activity is needed
to boost wettability
and that higher tin content leads to more salts, that are harder
to clean.
So, What should you do?
Changes with critical evaluation can be positive. Treat cleaning
as a critical part of the overall process. Do not assume that
the new
fluxes
will clean
the same ways as the old. Understand the materials and what
it takes to clean them
• TEST on your equipment
• TEST on your products
(Adapted from a presentation at the 2006 Del Mar (CA) Electronics Show.
The presentation is available from BFK Solutions upon request).
References:
B.A. Bivins, A.A. Juan, B. Starkweather, N.C. Lee, and S. Negi, “Post-Solder
Cleaning of Lead-Free Solder Paste Residues”, SMT International 2000,
Chicago, IL, September, 2000.
N.C. Lee, and M. Bixenman, "Flux Technology For Lead-Free Alloys & Its
Impact On Cleaning," 2001 Advanced Packaging Technology Conference Proceedings,
Boston, 2001.
