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This paper describes methodologies on how to enhance solder joint reliability in electronic automotive modules to meet harsh field environments. The reliability enhancement of a QFN component has been investigated and results are presented. The first step is to optimize the PCBpad including dividing center pad areas underneath the package. The second aspect is to use corner bond or underfill. Several types of glue materials have been tested and the effectiveness of the reliability enhancement has been demonstrated. A new way to solve the reliability issue is presented which uses organic substrate as base for QFN. The reliability test by thermal cycling was performed and finite element analysis (FEA) has been employed to understand the mechanism of those design changes. The results show that corner bond material is very effective in reliability enhancement.

This paper describes solder joint reliability studies for DDR memories using single side and double side mount modules in the application of consumer and automotive fields. The types of DDRs include LPDDR4 and GDDR5. The components are from well-known memory manufacturers. Both experimental work and numerical simulation are employed to understand the reliability and failure mechanisms. It is found the reliability of DDRs changes with different DDR types as well as suppliers. LPDDR4 has much lower reliability as compared to that of GDDR5. The reason is the low ball profile which has increased the thermal stress for LPDDR4. However, the most critical factor is the double side mount vs. single side mount configuration. Both experimental and FEA results show corner fill may be a better choice in handling both mechanical and thermal stresses. To enhance the solder joint reliability, one effective way is to employ corner fill, edge bond or underfill. However, in order to get better reliability, corner fill and underfill are normally recommended.

Several types of glues are applied to fcBGA on the board level in order to enhance the reliability of PCB assembly to meet harsh automotive conditions. This paper describes a series of mechanical and thermal stress tests using a printed circuit board (PCB) for automotive applications. FEA and experimental results show that corner fill may be a better choice in handling both mechanical and thermal stresses. All glues tested have shown improvement on the mechanical stress but not every glue can improve the thermal cycling reliability of solder joints. Results also show that underfill may not have the same performance as compared to corner fill for this application and is hereby not recommended.

This paper describes a road test using a printed circuit board (PCB) used for automotive applications. In order to characterize the vibration stresses, a series of road tests were conducted which included different automobiles and road conditions such as city and highway. During the road tests, a comprehensive data acquisition system was used which can record temperature, acceleration, driving speed, strain, etc. Strain sensors are mounted on the PCB module close to a major IC component. Experimental results show a clear correlation between acceleration, speed and road conditions. The stresses obtained from vibration during the road tests are generally much smaller compared to the lab tests on a vibration table. However, the maximum board strain may be significant and worthy of further studies. The objective is to assess the fatigue risk of solder joints during field use to warranty operation of 10k hours in 15 years.

High reliability at the board level is challenging for a large flip chip ball-grid-array (fcBGA) where large die and stiff substrate are used. For those BGA solder joints, the difficulty is to achieve high reliability in both thermal cycling and mechanical dynamic tests. This paper presents experimental work on an fcBGA with a die size of 25×15mm, a body size of 40×40mm and over 1700 ball count. The reliability tests include thermal cycling from -40C to 85C up to 7,500 cycles, mechanical drop at 1500G and 9-point cyclic bending test run to failure. To develop a good reliability model, the integrity of both the solder joint and substrate copper traces are monitored using in-situ resistance measurement in combination with frequent cross-sectioning and dye-and-pry (DnP) to understand the progression of cracking in the solder joints. Using Finite Element Analysis (FEA), the solder joint failure mechanism was verified and a new failure mode in mechanical reliability testing has been confirmed.