Abstract:The effects of bonding forces and reflow process on the failure behaviors of anisotropic conductive film (ACF) interconnections were analyzed. Conventional reflow process was employed with peak temperatures of 220 C for soldering of Sn-37Pb and 260 C for soldering of Pbfree Sn-Ag or Sn-Ag-Cu. Two kinds of main failure mode were detected after double reflows at 220 C: formation of a conduction gap between conductive particles and Ni/Au-plated Cu pad, and delamination of the adhesive matrix from the plated Cu pa… Show more
“…For voltages above 16 kV, the jets broke leading to short segments of polymer fiber.Figure 2.Design space of the hard-to-change factors: PVDF concentration and DMAC/acetone ratio (blue circles). Black squares: parameters that lead to bead-free PVDF fibers according to literature (1: 58 ; 2: 59 ; 3: 60 ; 4: 61 ; 5: 62 ; 6: 30 ).…”
Electrospinning is one of the leading techniques for fiber development. Still, one of the biggest challenges of the technique is to control the nanofiber morphology without many trial-and-error tests. In this study, it is demonstrated that via design of experiments (DoE), response surface methodology (RSM) and machine learning regressions (MLR) it is possible to predict the beads-on-string size, size distribution and bead density in electrospun poly(vinylidene fluoride) (PVDF) mats with a small number of tests. PVDF concentration, dimethylacetamide/acetone ratio, tip-to-collector voltage and distance were the parameters considered for the design. The results show good agreement between the experimental and modeled data. It was found that concentration and solvent ratio play the main roles in minimizing bead size and number, distance tends to reduce them, and voltage does not play a significant role. As an evaluation of the potential of the method, bead-free fibers were obtained through the predicted parameter values. Comparison of the performance of the two methods is presented for the first time in electrospinning research. Response surface methodology resulted much faster, but MLR achieved a lower error and better generalization abilities. This approach and the availability of the MLR script used in this work may help other groups implement it in their research and find information hidden in the data while improving model prediction performance.
“…For voltages above 16 kV, the jets broke leading to short segments of polymer fiber.Figure 2.Design space of the hard-to-change factors: PVDF concentration and DMAC/acetone ratio (blue circles). Black squares: parameters that lead to bead-free PVDF fibers according to literature (1: 58 ; 2: 59 ; 3: 60 ; 4: 61 ; 5: 62 ; 6: 30 ).…”
Electrospinning is one of the leading techniques for fiber development. Still, one of the biggest challenges of the technique is to control the nanofiber morphology without many trial-and-error tests. In this study, it is demonstrated that via design of experiments (DoE), response surface methodology (RSM) and machine learning regressions (MLR) it is possible to predict the beads-on-string size, size distribution and bead density in electrospun poly(vinylidene fluoride) (PVDF) mats with a small number of tests. PVDF concentration, dimethylacetamide/acetone ratio, tip-to-collector voltage and distance were the parameters considered for the design. The results show good agreement between the experimental and modeled data. It was found that concentration and solvent ratio play the main roles in minimizing bead size and number, distance tends to reduce them, and voltage does not play a significant role. As an evaluation of the potential of the method, bead-free fibers were obtained through the predicted parameter values. Comparison of the performance of the two methods is presented for the first time in electrospinning research. Response surface methodology resulted much faster, but MLR achieved a lower error and better generalization abilities. This approach and the availability of the MLR script used in this work may help other groups implement it in their research and find information hidden in the data while improving model prediction performance.
“…If there was less number of captured balls, the contact area should be lower and it could cause the higher contact resistance. [8] Figure 6. Contact resistance of nanofiber/solder ACFs and solder ACF.…”
Nanofiber/solder ACFs are investigated in terms of ball movement and electrical properties depending on their nanofiber polymer types: polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF). For both nanofiber solutions, SAC305 (96.5% Sn, 3% Ag, 0.5% Cu with 217 °C melting point) conductive solder balls were incorporated into nanofibers which were fabricated by electro-spinning method. Then, non-conductive films (NCFs) were laminated on top and bottom of the electrospun nanofibers to fabricate nanofiber/solder ACFs. For the bonding method, ultrasonic (U/S) bonding method was conducted to remove solder oxide which allowed fluxless soldering and reduced bonding time. PAN and PVDF nanofiber/solder ACFs successfully provided limitation of solder ball movement resulting in excellent ball capture rate on electrodes.
“…While Si steel sheet is rolled in the α phase temperature region, the Goss texture is formed near the surface layer of Si steel sheet due to the friction between the steel sheet and rolls at elevated temperatures. The increase in friction between the steel sheet and rolls increases the shear deformation and increases the intensity of the Goss texture [1][2][3][4]. The fabrication process of this Goss texture formation in Si steel sheet is very complex and difficult in steel making industry.…”
The Goss texture, or {110}<001>, shows soft magnetic property due to the <100>. Therefore, it is one of the most important texture in Si steels. The Goss texture is one of the shear deformation texture in steel which has bcc structure. During the asymmetric rolling, shear deformation is imposed on steel sheets. To obtain the Goss texture, the carbon and Si steel sheets were asymmetrically rolled by 50-85% reduction in thickness at room temperature and at 770 °C. The asymmetric rolling of steel sheets gave rise to the well-developed Goss texture to them.
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