Here is an interesting turn of events related to the reliability of lead-free (Pb-free) soldering reliability.
I was reminded recently by something Carl Sagan said, or, actually, did not say: Billions and Billions Although this term is strongly associated with him, he never said it. Sagan believed that this term was connected to him because Johnny Carson mimicked him and used the term.
Although not even close to being in Sagan's league, I find that I am now equally unfairly associated with the term, "lead-free solder is a grand success." This came about in an interview by Rob Speigel, which he summarized in a blog post.
In reading Speigel's post, you will see that, "lead-free solder is a grand success," is Rob’s term, not mine. Well, Rob's post resulted in a string of postings on IPC’s Technet .
One person opined:
Irresponsible statements like "lead-free solder is a grand success" should NOT be ignored. Those who make such statements in the face of all of the contrary evidence should be noted, and treated as motivated only by greed. Lead-free soldering certainly has been known for many "thousand$" of successes.
I have learned that it is not even worth the bother to refute such statements with those who make them. It may be a "grand success" for PhDs who contract to solder paste companies, but it certainly has not been a "grand success" to literally thousands of companies dealing with the reliability elephant sitting in the room getting larger by the day, and the associated fallout as a result.
I disagree with the stated and implied affect of RoHS, on PWBs expressed in this article. Lead free assembly reduces reliability by 50%. There can be no doubt about that. There are too many studies that confirm lead free assembly significantly degrades reliability. There are so many studies that demonstrate a reduction in reliability that Rod's contention is almost laughable. We are now faced with increased failures of copper interconnections and dielectric material due to high assembly temperatures. There is an increase in crazing that can support CAF, significant copper dissolution, and cratering in assembly, Switching to lead free in most HDI applications is a significant challenge. Lead free assembly has a profound affect by degrading PWB's organic component (epoxy) due the temperature required and copper interconnection and also the exaggeration of the z-axis expansion of the dielectric.
I have asked for copies of the many reliability studies referred to. No response yet.
Finally someone hit the heart of the matter:
I'm curious if "grand success" were Dr.Lasky's words or Rob Spiegel's editorializing. Lasky does mention the lack of long term results, and Speigel, in the comments, enumerates a number of reliability problems. ISTM that neither truly believes those words.
Here was my response that I posted on Technet:
Pete is correct. I never said lead-free implementation was a grand success. These were Rob's words in his blog post.
I have said repeatedly that adequate lead-free reliability has been demonstrated for consumer products like mobile phones, PCs, portable electronics with service lives less than 5 years. This level of reliability has been demonstrated in numerous studies and more importantly with field data. Vahid Goudarzi, of Motorola, stated that field reliability of lead-free assembled mobile phones has been equal or better than leaded assembly units. His data go back to 2001 (not 2006. Motorola started early for reasons discussed below).
The reason Motorola shipped early with lead-free products is due to the fact that lead-free solder does not spread as well. Because of this poorer spreading, Motorola was able to decrease lead spacings without getting shorts, thus increasing the amount of electrical function in a smaller space. Since increased function in a smaller space is the defining attribute of portable electronics, the importance of this lead-free advantage cannot be overstated. Admittedly, lead-free's poorer wetting is a challenge in other regards, especially hole fill in wave soldering, but the Motorola Droid X2 could not be assembled with leaded solder, there would be too many shorts. Since the packaging density of the iPhone and similar devices is on a par with the Droid X2, I suspect this statement is true for most mobile products.
I have also repeatedly stated that lead-free reliability for long term service, mission critical devices has not been demonstrated. As a result, these types of devices should not consider lead-free solder at this date.
I regularly discuss these topics in my blog (http://blogs.indium.com/blog/an-interview-with-the-professor). The most recent post shows a striking photo of leaded solders spreading -which is too "good" for portable electronics.
The Image is of Carl Sagan's Book Billions and Billions.