Are you Ready for Lead-Free
Solder?
Major changes will soon affect nearly
everyone who makes or uses electronic equipment, including
amateur scientists. The changes are a result of serious
concerns about the toxicity of certain materials used
in the manufacture of electronic components and equipment.
Fluorescent tubes contain mercury. Electronic circuit
boards and the glass used to make cathode ray tubes
contain lead. Various electronic components and batteries
contain cadmium.
The European Union has passed a directive
that effectively bans many materials commonly used to
manufacture electronic components and systems. Because
of the international nature of electronics commerce,
the ban will affect many countries outside the European
Union.
There is good reason to be concerned
about the sweeping nature of the ban. For example, cadmium
sulfide photoresistors are used as light sensors in
a wide variety of applications. Cadmium sulfide is also
used to make solar cells. Nickel cadmium rechargeable
batteries contain cadmium. Cadmium coatings provide
important corrosion resistance for various electronic
components. Yet the EU directive effectively bans these
and other applications for cadmium and various other
materials: "Member States shall ensure that, from
1 July 2006, new electrical and electronic equipment
put on the market does not contain lead, mercury, cadmium,
hexavalent chromium, polybrominated biphenyls (PBB)
or polybrominated diphenyl ethers (PBDE)."
The ban on lead will have an especially
broad impact. Consider the solder that secures electronic
components to circuit boards and provides mechanical
strength and excellent electrical conductivity.
The impact on the ban on lead in solder
has been addressed by Dr. Craig Hillman of DfR
Solutions in "Long-term
reliability of Pb-free electronics" in Electronic
Products magazine. The subtitle of Dr. Hillman's
article is, "Will the field return rate of your
product be going up after Pb-free conversion?"
Figure 1 illustrates the importance of this question,
for traditional tin-lead solder provides significant
mechanical shock resistance for electronic circuit boards.
Switching to non-lead solder may greatly reduce the
long-term reliability of electronic systems.
Dr. Hillman also discusses other problems
with lead-free solder, including the formation of tin
whiskers that can caused short circuits between conductors
on circuit boards.
Amateur scientists can learn more about
the coming ban on many common electronic materials by
visiting the compliance
page at the Newark Electronics web site. This site
features many relevant links. Especially important is
the link to the latest 2005
exemptions. This site lists new exemptions and those
under appeal. Note the request to exempt cadmium sulfide
photocells.
Citizen scientists are invited to send
comments about this issue to "Backscatter."
Please type "Lead Ban" in the subject line.
Forrest M. Mims III 
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