It's been a little over 100 days since the EU RoHS legislation came
into effect. In a few months China RoHS will come online. The U.S. is
anything but united as independently over a dozen states plan programs,
monitoring methods and deadlines, led by the California RoHS rollout
planned for January. As an industry we are divided. Some companies have
taken the waitand- see approach. Others feel they are outside the scope
of the legislation because they are not selling into the EU or they
make products that are currently exempt. Still others are embracing the
change, learning how best to become compliant and are actively trying
to meet the regulations within their day-to-day operations. And there
are a few who are gathering data, trying to build a case for repealing
the legislation. The "repeal RoHS" groundswell includes logical
arguments for why the elimination of lead from electronics will prove
to be too costly and ultimately less green than originally thought.
Where will it end? I imagine those who are most proactive will emerge
as the winners.
In all this fanfare, there has not been enough attention given to
some of the smaller details that need to be addressed if we are going
to be successful in implementing leadfree processes. We need to spend
more time on the nitty-gritty of getting the PCBs designed,
manufactured and assembled. Yes, the paperwork may kill you, but
nothing snaps at the bottom line harder than a sharp decline in yields.
For those of you on the path to compliance, no doubt every day brings
more questions than answers.
For those who are still on the cusp of grappling with compliance,
you will have the opportunity to learn from the mistakes made by
others. There are certainly technical issues; new ones are brought to
the surface daily. In September at the IPC Works meetings, one problem
garnered top billing - copper dissolution. In a nutshell, copper is
dissolved into solder during wave soldering. This in itself is not
unique to lead-free processing, but the fact is that as a board makes
more passes over the wave more copper is dissolved. The higher the
solder pot temperature, the more copper gets dissolved. More rework,
more copper dissolution. More copper dissolution, less copper in the
barrel of the hole. Combine thin copper in the plated through-hole with
higher soldering temperatures and the result is PTH failures. We need
to rethink some of our guidelines to prevent this type of post-assembly
failure. Even if we don't see immediately identifiable failures, the
underlying problems caused by intermittent thin copper will weigh
heavily on the long-term reliability prospects of many assemblies.
In addition, a serious knowledge gap exists. Designers lack a
reliable tool they can use when making base laminate material
selections for lead-free processing. Yesterday's slash-sheets are
insufficient. Even knowing the Tg, CTE and Td values of the laminate
when building boards over 0.090" in thickness may not be enough. A
board built with the proper Tg / Td material can still end up
delaminating during assembly. So, how does a designer select a laminate
for an 18-layer, 0.250" thick, RoHS-compliant PCB? Based on the
conversations I have had with designers over the past few months, the
industry could really use a fully integrated design tool that takes
into account the impact lead-free assembly processes have on the PCB.
The tool needs to translate these material changes into a set of key
factors that would lead to a data-driven base material selection
procedure. We understand intuitively that the increased temperature and
longer contact times associated with lead-free assembly have an impact
- but the precise extent of this change resides in tribal knowledge and
not in identifiable facts. It needs to be distilled into concrete
modeling tools that everyone can use, provide feedback on, expand and
improve. An opportunity for a new methodology exists, because taken
together, copper dissolution and incorrect laminate selection will
impact assembly yields severely.
We have some serious work to do in the second 100 days if we are
going to get our specifications and guidelines in sync with what's
actually happening to our products. Are you up to the challenge?
