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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

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lead free electronics

Lead-Free Electronics

Thermal Management of Electronics

San José State University

Mechanical Engineering Department

a lead free definition
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
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
Lead-Free Driving Mechanisms
  • Environmental Issues
  • Legislation
  • Ethics
  • Public Relations
  • Product differentiation
environment issues
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 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
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
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
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
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
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 high-temperature 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
Possible Outcomes of Higher Reflow Temperatures
  • Increased hygrothermal expansion
  • Increased popcorning
  • Component and board warpage
  • Component and board delamination
reliability and compatibility issues
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
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
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 tin-silver-copper and tin-silver bismuth alloys.
ibm study results
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
Nokia Study
  • Lead-free solder was used with nickel-gold printed circuit board finish, off-the-shelf 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
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
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 lead-based are compatible with lead-free assemblies
expections of lead based vs 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 lead-base and lead-free assemblies but they should be mitigated as assemblies prove to be reliable