Tag Archives: Pb-free

Toward a Pb-Free Consensus

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Folks,

Some time ago, I mentioned that I was working on a consensus of the status of Pb-free/RoHS-compliant assembly. My hope is to find data and facts that will support the consensus. I am making progress, but at this time I would like to share the subtopics in the consensus. Look them over and see what you think:

1.       Was/is lead-free electronics/RoHS needed to protect the environment?

2.      Is Pb-free solder easier and safer to recycle than Pb-containing solder?

3.      How has the increased use of tin and silver affected their supply and price?

4.      How much did it cost to implement Pb-free/RoHS-compliant electronics?

a.      What is the cost adder to a typical Pb-free product?

5.      What are the process challenges of Pb-free assembly? Are these challenges being addressed? If so, how?

6.        What is the reliability of Pb-free vs, leaded electronics for commercial applications (e.g., 0°C to 100°C thermal cycle, drop shock, etc.)?

7.        What is the reliability of Pb-free vs leaded electronics for harsh environment/military applications (e.g., -55°C to 125°C thermal cycle, other Mil stress tests)?

8.      What is the threat of tin whiskers, tin pest and other similar Pb-free related reliability phenomena?

9.      What is the status and need for halogen-free assembly?

Help me by suggesting topics that I have left out.

Best wishes,

Dr. Ron

Pluses and Minuses of Pb-Free Solder

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Folks,

I thought I would take a stab at listing the minuses, pluses, and “it’s a wash” aspects of assembling with lead-free (LF) solder. Here are my first thoughts. Please tell me what I missed or disagree.

Minuses

1.    Pb-Free requires higher reflow temperatures
The Tm for LF solders, in the 217-229C range, has created numerous challenges:

a.      PWB warpage and damage

b.      Component damage

c.      New defect modes such as graping and head-in-pillow defects (although concurrent reduction in solder paste deposit sizes for 0201 and 01005 passives and 0.3 mm CSPs also exacerbate these defects)

d.      Defects related to increased oxidation

e.      Increases in voiding

f.       Increases in tombstoning

2.      The higher cost of LF solder, mostly for wave soldering

a.      It’s not just the silver, tin is much more expensive than lead

3.      Poorer wetting of LF solders, creating the most significant challenges in wave soldering

4.      More rapid copper pad dissolution on PWBs in wave soldering

5.      LF solder attack of wave solder machine components

6.      LF reliability in harsh thermal cycle testing appears poorer than SnPb solders

7.      Tin Whiskers

It’s a Wash

1.      Short-term reliability in consumer product-type environments

2.      Protection of the environment if discarded products are improperly disposed of

a.      Lead in electronics has never been shown to cause a problem in land fills

3.      Since July 2006, about $3 trillion of products have been manufactured with LF solder, with no “the sky is falling”-type of problems

Pluses

1.      LF solder’s poor wetting enables finer lead spacings (see photo courtesy of Motorola)

a.      It may be argued that some modern electronic products (e.g., smartphones) could not be made with SnPb solder

2.      It is safer to recycle LF solders, especially if performed in a non-controlled environment
OK — your turn. Please comment.

Best Wishes,

Dr. Ron