Technical Library | 2014-06-12 16:40:19.0
Occurrence of popcorn in IC packages while assembling them onto the PCB is a well known moisture sensitive reliability issues, especially for surface mount packages. Commonly reflow soldering simulation process is conducted to assess the impact of assembling IC package onto PCB. A strain gauge-based instrumentation is developed to investigate the popcorn effect in surface mount packages during reflow soldering process. The instrument is capable of providing real-time quantitative information of the occurrence popcorn phenomenon in IC packages. It is found that the popcorn occur temperatures between 218 to 241°C depending on moisture soak condition, but not at the peak temperature of the reflow process. The presence of popcorn and delamination are further confirmed by scanning acoustic tomography as a failure analysis.
WASET - World Academy of Science, Engineering and Technology
Technical Library | 2023-05-02 19:06:43.0
As 0402 has become a common package for printed circuit board (PCB) assembly, research and development on mounting 0201 components is emerging as an important topic in the field of surface mount technology for PWB miniaturization. In this study, a test vehicle for 0201 packages was designed to investigate board design and assembly issues. Design of Experiment (DOE) was utilized, using the test vehicle, to explore the influence of key parameters in pad design, printing, pick-andplace, and reflow on the assembly process. These key parameters include printing parameters, mounting height or placement pressure, reflow ramping rate, soak time and peak temperature. The pad designs consist of rectangular pad shape, round pad shape and home-based pad shape. For each pad design, several different aperture openings on the stencil were included. The performance parameters from this experiment include solder paste height, solder paste volume and the number of post-reflow defects. By analyzing the DOE results, optimized pad designs and assembly process parameters were determined.
Technical Library | 2020-12-10 15:49:40.0
Electronic assemblies should have longer and longer service life. Today there are partially demanded 20 years of functional capability for electronics for automotive application. On the other hand, smaller components, such as resistors of size 0201, are able to endure an increasing number of thermal cycles until fail of solder joints, so these are tested sometimes up to 4000 cycles. But testing until the end of life is essential for the determination of failure rates and the prognosis of reliability. Such tests require a lot of time, but this is often not available in developing of new modules. A further acceleration by higher cycle temperatures is usually not possible, because the materials are already operated at the upper limit of the load. However, the duration can be shortened by the use of liquids for passive tests, which allow faster temperature changes and shorter dwell times because of better heat transfer compared to air. The question is whether such tests lead to comparable results and what failure mechanisms are becoming effective. The same goes for active temperature cycles, in which the components itself are heated from inside and the substrate remains comparatively cold. This paper describes the various accelerated temperature cycling tests, compares and evaluates the related degradation of solder joints.
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