• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.40-50
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• 2023

Recently, the number of components of smartphones increases rapidly, while the PCB size continuously decreases. Therefore, 3D technology with a stacked PCB has been developed to improve component density in smartphone. For the s tacked PCB, it i s very important to obtain solder bonding quality between PCBs. We investigated the effects of the properties, thickness, and number of layers of interposer PCB and sub PCB on warpage of PCB through experimental and numerical analysis to improve the reliability of the stacked PCB. The warpage of the interposer PCB decreased as the thermal expansion coefficient (CTE) of the prepreg decreased, and decreased as the glass transition temperature (Tg) increased. However, if temperature is 240℃ or higher, the reduction of warpage is not large. As FR-5 was applied, the warpage decreased more compared to FR-4, and the higher the number and thickness of the prepreg, the lower the warpage. For sub PCB, the CTE was more important for warpage than Tg of the prepreg, and increase in prepreg thickness was more effective in reducing the warpage. The shear tests indicated that the dummy pad design increased bonding strength. The tumble tests indicated that crack occurrence rate was greatly reduced with the dummy pad.

• Science of Emotion and Sensibility
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• v.12 no.1
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• pp.11-18
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• 2009

The purpose of this study was, first, to extract the risk factor by investigating several cases of accident of senile dementia patient at home, and second, based on these results to provide basic information for the determination of monitoring factor for the care of senile dementia patient. Basic and behavioral characteristics, Short form of Samsung Dementia Questionnaire (S-SDQ), Activities of Daily Living (ADL), and cases of accident were investigated with 55 senile dementia patient at home (16 male, 39 female). Based on these questionnaires, risk factors were extracted and frequency, cooccurrence frequency, and occurring place of risk factors, presence or not, region, and degree of injury were investigated. Frequency between risk factors and behavioral characteristics, ADL, and S-SDQ was analyzed by crosstabulation frequency analysis. Results showed that 12 risk factors were extracted, and the frequency of 'going out' was the highest, and risk factors for injury were 'tumble', 'bump', 'slip', and 'fall'. Cooccurrence frequency analysis showed that the occurrence of 'fall', 'going out', 'fire of gas', and 'violence' with other factors was relatively higher than others. The occurring place of risk factor was the highest in home neighborhood, and the region of injury in knee, and the degree of injury with bruise. Crosstabulation frequency analysis showed that factors which had difference in frequency of risk factor were behavioral disorder, disorder of daily living and ADL. Factor which had difference in frequency due to the degree of behavioral disorder and disorder of daily living was 'going out', and factors which had difference in frequency due to the degree of ADL were 'slip' and 'fire of gas'.