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Features Articles

Tim O'Neill With RoHS exemptions set to expire, can SAC 305 hang on?

It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change.
– Leon Megginson

The final steps of RoHS will be phased in over the next 24 months. Once implemented, lead will be virtually eliminated from solder in the electronics assembly supply chain. With the last exemptions applying predominantly to high-reliability applications, materials in use are being scrutinized to determine if they can perform to the mission requirements of high-reliability PCBs.

Concurrent to this material concern is the unrelenting trend in microelectronics: more functionality and performance in smaller spaces. As circuitry becomes denser and more power is inserted into smaller spaces, an inevitable byproduct is heat. These two realities, high-reliability requirements and increased power density, are exposing deficiencies in the de facto lead-free solder alloy, SAC 305. SAC 305 has performed adequately to this point. The processing temperatures are acceptable. It has proved sufficiently durable and is largely compatible with other common materials, albeit at considerably higher cost than the SnPb it replaced. Typically, if an alloy other than SAC is in use, it’s for cost containment rather than solder joint reliability characteristics. But the needs of the industry are evolving based on the aforementioned changes in regulation and reliability requirements. As a result, SAC 305 may fall out of favor, as it has a variety of undesirable inherent characteristics.

Martin Wickham Warping during reflow can leave solder balls distorted.

In cases where pad size, solder paste volume and solder spheres on a BGA are consistent in size, the solder joint size variation shown in FIGURE 1 is typically soldering-related. Modern x-ray systems can measure the joint sizes automatically and output a spreadsheet with the data. It is not uncommon to take these measurements on pre-production prototype builds, when product is working. This provides a permanent record of the ball variation on a satisfactory product. If problems are experienced in volume production, the results can be easily compared.

Peter Bigelow Supply chain separation has made engineering a more expensive proposition.

Based on my sailing experience, I can say with certainty a chain, such as the one that anchors your boat to a secure mooring, is only as strong as its weakest link. In the intangible world of business, however, it can be difficult to see differences between “weaknesses” versus “just another way of looking at things.”

Such was the case recently during a meeting with a large customer – the type of very large customer where they have almost as many global facilities as they do egocentric engineering personalities – when an alleged strength revealed itself to be instead the weakest link in a very long chain. Around a large table sat engineering, manufacturing, and quality gurus revealing their latest, greatest project.

Discussion focused on the “elegant” simplicity, the utilization of the “best available new technology” and of course the “time critical” requirement that all suppliers had to perform to. This was quite the humdinger of a program I am sure was going to make – or break – more than a few careers of those present.

Mike Buetow Jim Raby has been one of my favorite subjects over the years. How could he not be? He lived such a rich and interesting life. How many of us, for instance, can say we started our careers working side-by-side developing rockets with Wernher von Braun?

A legend in electronics soldering, Jim’s backstory is well-known. He spent his entire career in electronics manufacturing. Starting with the Saturn/Apollo Program, he became synonymous with soldering and high-reliability printed circuit assemblies. He is credited for developing the NASA and Navy (the famous China Lake) soldering schools, and was instrumental in developing the IPC soldering certification curriculum, used by the vast majority of the industry today. He initiated the Electronics Manufacturing Productivity Facility (later known as the American Competitiveness Institute). All in all, he trained tens of thousands of engineers and operators.

He was issued patents for wave soldering and embedded components, and initiated the Zero Defect Program for wave soldering. He also was the driver of the Lights Out Factory concept that revolutionized the modern electronics manufacturing facility.

Hom-Ming Chang High- and low-tech ways to ensure parts are correctly placed.

A core element of Lean manufacturing philosophy is the requirement to understand where inefficiencies and waste exist, in order to eliminate them. Even in a factory that thoroughly embraces Lean manufacturing and trains its personnel on all aspects of their jobs, there will be inefficiencies and waste related to operator error, supplier quality issues and process variation. SigmaTron International’s facility in Suzhou, China uses a two-part strategy to address this. At a systems level, it developed a proprietary Manufacturing Execution System (MES) system known as Tango to enhance shop floor control. At a granular level, the team evaluates production operations for areas where tooling or fixtures can minimize process variability and the potential for operator error. This month, we look at some of the common areas where this defect mitigation strategy can be most effective.

SigmaTron’s IT department takes a distributed approach to continuous improvement in its systems by letting teams at individual manufacturing facilities identify specific gaps in shared systems and develop appropriate software tools. These solutions are then tested at the facility that identified the need and later transferred across all facilities. Following development and testing in Suzhou, Tango was deployed to other facilities beginning in 2014.

Mike Buetow Consolidation is the enemy of innovation. Don’t believe me? Look at how, ahem, fast AT&T rolled out changes during its early heydays.

Ma Bell – the colloquial name for the telecom monopoly – took three years of testing (!) before it rolled out touchtone phones (aided by the invention of low-cost transistors, which Bell also patented). That was 1963. And the rotary dial was still the norm when I grew up in the 1970s. It wasn’t until the early ’80s that we made the shift, and even then AT&T was still offering rotary for wall-mounted units.

In 1982, the US government forced the breakup of Ma Bell. Cordless phones were starting to take hold about that time. The breakup unleashed a slew of digital features that to date had been wasting away in research labs. Call waiting was a revelation. Conceived by Western Electric in the 1970s, it was offered an option and hardly commonplace until the mid to late ’90s. Voicemail was invented in 1979.
It was picked up first by businesses and made its way to consumer accounts only as cellphones began their relentless penetration.