In 2002, the European
Parliament promulgated what we at CineMag anticipate to be
the first of a number of regulations to drastically reduce
or eliminate certain substances which may be hazardous in
the environment. They are known as 2002/95/EC or
RoHS regulations. RoHS stands for Reduction of
Hazardous Substances. These rules severely lmit the
amount of lead, mercury, cadmium, hexavalent chromium,
polybrominated biphenyls (PBB) and polybrominated diphenyl
ethers (PBDE) in most products sold in European Union
countries. Because of our customers’ need to meet
these ever-growing environmental regulations, CineMag has
committed to conversion of most of our production to the
CineMag will provide written
certification of RoHS compliance upon request when
purchase orders are placed. Please be sure to
specify this in your PO. If your application demands
that it not comply with RoHS, mostly that
lead-containing solders be used, be sure to specify this
prominently and in writing.
There are a number of
significant challenges which you will face if you use a
lead-free solder to connect to our transformers and
inductors, which you must do in order to maintain the RoHS
standard. Use of a solder containing lead will
obviously contaminate the product and it will no longer
meet the RoHS standards.
Lead-free solders work
at a higher temperature than the tin-lead alloys
than you may be used to. This working
temperature will be about 50 C higher than for
Tin-Lead alloy solders. We recommend that you
now maintain a soldering iron tip temperature of 335
C (about 665 F). This temperature can not be
applied for more than 5 seconds to any pc bobbin pin
without risking destruction of the device.
Wire leads, similarly, will experience insulation
breakdown if adequate care is not taken. The
use of wave soldering or solder pots on pc pins is
not recommended and will void all warranties.
The lead-free solders are less ductile.
Solder joints will fail more readily when subjected
to deformation which can occur with vibration or
Solder joints will not have the same bright
finishes that lead-tin alloys afford and may look
granular. You should become proficient with
what to expect and how to successfully solder with
these lead-free alloys prior to soldering up your
CineMag transformer or inductor. Otherwise,
you can readily over-work the joint causing both a
poor solder connection and damage to the part.
Solder whiskers are now a major concern in the
electronics industry. They were virtually eliminated
by the 1960s with the advent of modern lead-tin solders.
With the advent of RoHS, these reliability issues have
returned. By the time this Application Note is
published it is expected that a number of US jurisdictions
will undertake to enact similar hazardous substances
Generally, because of relatively large geometries and
construction methods, transformers themselves should
not experience major problems with whisker growth.
However, CineMag does not recommend that RoHS
compliant transformers be used where maximization of
mean time between failures (MTBF) is critical.
Whiskers can grow to be many millimeters long.
It is a good idea to keep this in mind when designing
your product. Use of solder masks on pc boards may
have some benefit but the whiskers are capable of
undercutting or piercing weak areas in the mask.
Keeping tin coated areas well separated as well as
conformal coated may be helpful.
NASA reports that a number of satellites have failed
because of Tin (Sn) whisker phenomena. Note that
tin-lead solders significantly reduce this problem, as
shown in these NASA photomicrographs.
Note that whisker growth is most aggressive at
the bend in the leads
coming from the crystal. Stress of Tin (Sn)
accelerates whisker growth. Whisker growth is
not limited to strained areas.
On April 17, 2005, the Millstone Power Station
Unit 3 nuclear reactor located in Connecticut was
automatically shut down when a tin whisker caused a
short on a computer card. This gave the false
indication that there was a major steam leak.
This failure caused an automatic safe shutdown.
It is feasible that a short could have disabled an
automatic safety system and contributed to a
“significant” reactor failure.
Whisker growth is not limited to Sn. Zinc (Zn)
whiskers have shut down a major computer center before.
Cadmium (Cd) and Silver (Ag) whisker growth in
electronics have been well documented. Sn, though,
is significantly more prone to developing whiskers.
Research indicates that Sn whiskers seem to erupt as a
result of the release of inter-crystalline stresses.
RoHS solders typically are an alloy of Sn, Copper (Cu)
and Silver (Ag). These solders are very
chemically active and dissolve Cu away much more
rapidly that the Lead (Pb) based solders did.
The rate materials are dissolved is a function of
temperature. Be careful to regulate your working
temperatures to the minimum which is practical thereby
reducing the potential of damage to the component or
Again, do not be lulled into complacency
because the Sn covered area has been conformal coated
or because the most critical point is not a bent wire.
Sn whiskers can undercut or pierce through weaknesses
in conformal coatings. The conformal coating may
enhance the MTBF rating, but this will not eliminate
this failure mode. Sn whiskers will erupt
anywhere there is Sn. Strain only accelerates
Work by Boettinger, Johnson, Bendersky, Moon,
Williams and Stafford at the NIST in 2005 establish that
these stresses result in the eruption of microscopic
conical hillocks on the surface of the joint. Out
of these hillocks are extruded very fine Sn whiskers.
The following photomicrographs are of cantilevers upon
which were electrodeposited a Sn-Cu alloy and
Close-up of the whisker in Figure 1
Growth of a hillock over the time period of less than 12
hillock. Note whisker erupting.
CineMag uses mu-metal alloys in most of its
transformers as well as all of its shielding cases which
are alloys containing a large proportion of Nickel (Ni).
While not yet an issue with RoHS, Ni is not approved for
extended contact with skin or tissues under the Joint
Industry Guide JIG-101, as approved by the JEDEC Board of
March 29, 2006
Canoga Park, CA 91304
Tel (818) 993-4644
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