Transcript Lead-Free Electronics

Lead-Free
Electronics
Thermal Management of Electronics
San José State University
Mechanical Engineering Department
A Lead-Free Definition
 Lead-free – the assembly of electrical
and electronic packages without the
intentional use of lead in the raw
materials or the manufacturing process
 NOTE: Lead may still exist in the final
product even though it is not intentionally
added
Lead-Free Standards
 JEDEC – Solid-state devices that contain
no more than 0.2% by weight of
elemental lead
 NEMI – Products that have no lead
intentionally added and joints that have
less than 0.2% lead by weight
Lead-Free Driving
Mechanisms
 Environmental Issues
 Legislation
 Ethics
 Public Relations
 Product differentiation
Environment Issues
 Lead in electronics becomes an issue
once deposited into landfills
 Lead oxidizes when it comes into contact
with water
 This contaminated water that may seep into
drink water supplies or out into the
environment
 Consumer electronics constitute 40% of
the lead found in landfills
Legislation
 Legislation has already been passed in Europe
pertaining to a ban on lead in electronics.
Effective July 1, 2006
 Other countries (like US) may not have this ban
but for their products to be marketed globally they
must switch to lead-free
 Lead-Free legislation may also come to other
countries so it is beneficial for all electronics
companies to begin the switch to lead-free prior to
the enactment of these laws
Ethics and Public
Relations
 Knowing that lead is an identified toxin is it
unethical to continue using it when alternatives
exist?
 The public knows that lead is a toxin therefore
any effort by a company to produce lead-free
products will enhance their stature with the
public; this has been esp. important in Japan
Product Differentiation
 Consumers are enticed by the difference
between products
 Lead-free is not necessarily an
improvement performance wise but
environmentally minded consumers will
pay higher prices for lead-free electronics
Lead in Electronics
 Most lead found in electronics is from
lead base solders
 Lead is used because:
 It is abundant and readily available
 It is cheap
 It melts at reasonably low temperature so
when soldering there is no damage to
surrounding electronics; less thermal stress
is induced than it would with other materials
Issues with lead-free
solders
 Finding relatively cheap alloys to use in
place of lead
 Higher reflow temperatures
 Reliability and compatibility issues with
lead-free components
Cost Issues
 Most solders are lead-tin alloys but lead-free
solders are usually some other alloy mixed with
tin
 The alternate alloy is more expensive but can be
comparable in price to lead-tin solder for hightemperature electronics (above 200 degrees C)
 Some alternate alloys include: silver, copper, pure tin,
bismuth, antimony, ect
 There are also cost issues associated with
updating manufacturing processes
Possible Outcomes of Higher
Reflow Temperatures
 Increased hygrothermal expansion
 Increased popcorning
 Component and board warpage
 Component and board delamination
Reliability and
Compatibility Issues
 Intermetallic formations between:
 Component leads and boards
 Lead-free solder and metallization on the
chip, lead, or substrate
 Formation of tin whiskers
 Durability of:
 Leaded and area array packages
 Solder joints
Obsolescence Concerns
 Will lead-based components be
compatible with lead-free components?
 If not, companies will begin to run out of
replacement parts for lead-based
assemblies once the switch to lead-free
technology occurs
IBM Study
 Experiment designed to test the life of
ball grid arrays
 Accelerated thermal cycling used for
operating (0°C to 100°C) and extended
ranges (-40°C to 125°C) were combine with
various cycling up times to 240 minutes
 Reflow temperatures for assemblies were
215°C for tin-lead solder and 235°C for tinsilver-copper and tin-silver bismuth alloys.
IBM Study Results
 Both lead-free assemblies were more
fatigue resistant in the operating range
 Lead assemblies were more fatigue
resistant in the extended range at higher
cycling times
 Reflow temperatures for lead-free solders
were well below the expect 260°C
Nokia Study
 Lead-free solder was used with nickelgold printed circuit board finish, off-theshelf components, ball grid arrays, chip
scale packages, and leadless ceramic
chips
 Reflow temperatures for the leadless
solder were achieved at 245°C
Nokia Study Results
 Reflow temps. were below the expected 260°C
 Moisture sensitive packaging showed more
damage due to the higher reflow
 Popcorn cracks were found
 The components showed a failure rate five
times that of the lead based solder
 Board warpage was minimal
 Lead-free joints out-performed lead based
joints
Nortel’s Lead-Free PCB
Assembly
 Lead-copper solder was used with a reflow
temp. of 242°C
 Assembly was not really lead-free; a mixture of
lead-based and lead-free components were
used
 Approximately ¾ of 200 boards were
assembled on the first reflow and all boards
passed electrical and functional tests
 Demonstrated that components that are leadbased are compatible with lead-free
assemblies
Expections of lead-based
vs. lead-free assemblies
 Most lead-free assemblies have initially proven
to be as good or better than lead-based
solders and are expected to uphold this
equality. Research into prevention of
popcorning must continue.
 There are still reliability issues for long-term
use including: intermetallic growth, creep
deformation, and tin whiskers
 There are still compatibility concerns with leadbase and lead-free assemblies but they should
be mitigated as assemblies prove to be reliable