The movement to Pb-free soldering will result in solder joints that are significantly stiffer than those made of SnPb. This paper presents the results from the first phase of a two-part study to understand and compare the isothermal mechanical fatigue behavior of tin-silver-copper (SnAgCu) solder to that of tin-lead (SnPb) solder. A combination of experiments and finite element analysis was used to compare and predict the durability of SnPb and SnAgCu surface mount solder joints. The experiments were composed of cyclic four-point bend tests of printed wiring board coupons populated with 2512 sized resistors at 5 and 10 Hz. This configuration was chosen so the test would reflect actual electronic products and still be rapidly modeled using finite element analysis (FEA). This frequency should be sufficiently high to minimize solder creep during the testing. The board level strains were verified with strain gauges and the solder joint failures were detected using a high-speed event detector. Tests were conducted at two board level strain values and then modeled in FEA to determine the strains and stresses developed in the solder joint. This information was then used to determine the appropriate cyclic fatigue relationship for both SnAgCu and SnPb solder. The results indicate that at high board level strains SnPb solder out performs SnAgCu solder. However, at lower board level strains the SnAgCu solder out performed SnPb. The second phase of the study involves bend testing at even lower board level strains to characterize the high cycle fatigue behaviors of the solders.
Topic:
Solder Joint Fatigue
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Electric vehicles are practically computers on wheels. New innovations such as active and passive safety systems, electric propulsion, and semi and fully autonomous vehicles have all contributed to an increase in the usage of electronics in automotive applications. More importantly, automotive designers must still adhere to the same size and packaging constraints to ensure vehicles’ size and weight does not increase. To resolve this dilemma, automotive designers often rely on components being tightly placed on both sides of the Printed Circuit Board (PCB) to ensure the most efficient use of board space.
Topic:
Sherlock Automated Design Analysis,
Sherlock,
Reliability Physics
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Many companies work together to design electronic systems. During the qualification process, there is a lot of back and forth between the final users (mostly OEMs or manufacturers) and the suppliers. In the ideal world, the more information that is shared between both parties, the more likely they are to produce reliable and safe products. In reality, two companies can’t openly share all the design details due to intellectual property considerations. The circuit card designer does not want to share the board details with a prospective customer. Simultaneously, to protect new product ideas, the systems integrator may not want to share use environment details with the board designers. The need for both parties to protect their IP and stay competitive makes it hard to collaborate.
Topic:
Reliability Physics,
Sherlock Automated Design Analysis
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One of the key problems in today’s electronics industry is the constant changes in needs and deliverables. Today’s electronic devices are smaller and faster and are constantly exposed to changing environmental conditions. With more people putting electronics closer to a human body in the form of wearables such as iPhones, Fitbits, or heart monitors, electronics designers and manufacturers need to ensure the safety and reliability of these devices to avoid costly mistakes.
Here, at DfR Solutions we work with hundreds of electronics manufacturers across industries and have noticed an increasing number of companies reporting early life failures in the field or unexpected failures in tests due to solder fatigue. They're noticing that the classic solder fatigue calculation models do not seem to capture all the possible risks of failure.
Topic:
Reliability Physics,
system level effects
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Since the first pedestrian fatality due to an autonomous vehicle in March 2018, there’s been no shortage of discussion and debate over the future of autonomous vehicles and AV testing.
However, as Dr. Craig Hillman discusses in this month’s issue of SAE’s Autonomous Vehicle Engineering, there’s a critical piece missing from that conversation: the interconnected roles of reliability and safety. In many companies, there tends to be a disconnect between the two departments. And because authority and responsibility (i.e., who does what and who reports to whom) can have such a dramatic impact on hardware and software design cycles, keeping these two departments in silos can have negative effects.
