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 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 • 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 tin-silver-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 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 • 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 lead-based 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 lead-base and lead-free assemblies but they should be mitigated as assemblies prove to be reliable

Lead-Free Electronics