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Outlook and Trends 2011: A Perspective
January 3, 2011 |Estimated reading time: 3 minutes
Smaller, Faster, Lighter, Less Expensive
The mantra of smaller, faster, lighter, cheaper will continue unabated. This trend has been unyielding now for nearly a generation. The demand created is well satisfied by breakthrough products like Apple’s iPad and iPhone. These devices have achieved unprecedented packaging density, with the iPhone 4’s PCBs having a silicon area/PCB area of 1.52 (Reference 1), meaning that the area of the silicon die is 52% greater than the area of the PCB. This tremendous density is accomplished by package-on-package (PoP) technology, in addition to 0201 and even 01005 passives and 0.3mm CSPs. Small passives like 01005 have been slower to arrive than first thought, most likely due to the difficulty in assembling them. Perhaps 2011 will be the year they become more widely established.
Most of the above improvements are evolutionary, but a revolutionary technology change is slated to emerge in 2011, 3D wafer stacking (http://www.tezzaron.com/about/about.html). This technology connects wafers directly, avoiding the additional PoP.
Lead-free Reliability will Become Accepted as Reasonable for Consumer Products
Two papers (Reference 2 and 3) at SMTAI in October last year demonstrated that lead-free reliability exceeds that of lead-containing solder in both drop shock testing and thermal cycling from 0 to 100°C. In addition, some lead-free assembled products were introduced in the late 1990s with no significant yield or field reliability problems. Adding these two facts together, it is time to accept that reasonable lead-free reliability for consumer products with something like a three to five year service life has been established.
The more harsh requirements of automobile and military environments, evaluated at thermal cycling regimes of -55°C to 125°C, for greater than five years do not look as promising for lead-free reliability. I expect that products in these types of environments will have lead-containing solder exemptions for years to come.
Convergence of Lead-Free Alloys will be Elusive
There are numerous “flavors” of lead-free alloys in use. SAC305 (3.0% Ag, 0.5% Cu, the balance Sn, followed by SAC105 and the tin-copper alloy (99.3% Sn, 0.7% CU with traces of Ni and Ge) ) is most commonly used in wave soldering. In the mid-2000s, it appeared that SAC305 would be the alloy of choice; however, SAC105 was shown to have superior drop shock performance, which is a great benefit to portable devices. In addition, work by Lee (Reference 4) has shown that additions of about 0.1% of Mn and other elements to SAC105 can increase its drop shock performance by as much as a factor of ten. The downside of SAC105 is that its melting temperature is about 6-8°C higher than SAC305. The tin-copper alloy is used in wave soldering because of its much lower cost. All of these things taken together suggest that it is highly unlikely that lead-free assembly will converge on one alloy.
Counterfeit Components: Scourge of the Era
With the advent of recycling and short product life cycles, counterfeit components will likely be the biggest electronics assembly concern for the foreseeable future. It is already an “industry” value in multiple of $10s of billions of dollars, with 10s of thousands of highly motivated people, in numerous third world countries. Some analysts suggest that more than 10% of all components assembled are counterfeits. Expect to see continued efforts to develop technology-based strategies to combat this crisis. In an era where computer memory is almost free, it wouldn’t be surprising for each component to be registered in a data base and checked by placement machines during assembly.
References
- David Carey, 3D Packaging Continues Electronics Footprint Reduction, SMTA Expo Austin, TX October 2010.
- Coyle, Richard, etal, The Effect of Silver Content on the Solder Joint Reliability of a Pb-free PBGA Package, SMTAI, Orlando, FL, Oct 2010
- Henshall, Greg, etal, Low Silver BGA Sphere Metallurgy Project Phase II – Reliability Assessment Sixth Report: Thermal Cycling Results for Unmixed Joints, SMTAI, Orlando, FL, 2010.
- Liu, Weiping and Lee, Ning-Cheng, Novel SACX Solders with Superior Drop Test Performance, SMTAI, Chicago, IL, September, 2006.