• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.57-61
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• 2021

A formation process of indium bump arrays on micro-pillar structures is proposed. The space to form indium bump on the narrow structures can be secured applying the benzocyclobutene (BCB) planarization and its etch-back process. We exhibit a detailed overview of the process steps involved in the fabrication of 320×256 hybrid camera sensor for short-wavelength infrared (SWIR) detection. The shear strength of the BCB, which has undergone the different processes, is extracted by quartz crystal microbalance measurement. The shear strength of the BCB is three orders of magnitude higher than that of the indium bump itself. The measured dark current distribution of the fabricated SWIR camera sensor indicates the suggested process of indium bumps can be useful for embodying highly sensitive infared camera sensors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1120-1127
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• 2013

In this paper, novel chip-on-chip(CoC) flip-chip bump structures using chip-on-wafer(CoW) process technology are proposed, designed and fabricated, and their microwave frequency responses are analyzed. With conventional bumps of Cu pillar/SnAg and Cu pillar/Ni/SnAg and novel Polybenzoxazole(PBO)-passivated bumps of Cu pillar/SnAg, Cu pillar/Ni/SnAg and SnAg with the deposition option of $2^{nd}$ Polyimide(PI2) layer on the wafer, 10 kinds of CoC samples are designed and their frequency responses up to 20 GHz are investigated. The measurement results show that the bumps on the wafers with PI2 layers are better for the batch flip-chip process and have average insertion loss of 0.14 dB at 18 GHz. The developed bump structures for chips with fine-pitch pads show similar or slightly better insertion loss of 0.11~0.14 dB up to 18 GHz, compared with that of 0.13~0.17 dB of conventional bump structures in this study, and we find that they could be utilized in various microwave packages for high integration density.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.1
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• pp.33-38
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• 2001

We investigate the via-size dependance of as-electroplated- and reflow-bump shapes for realizing both high-density and high-aspect ratio of solder bump. The solder bump is fabricated by subsequent processes as follows. After sputtering a TiW/Al electrode on a 5-inch Si-wafer, a thick photoresist for via formation it obtained by multiple-codling method and then vias with various diameters are defined by a conventional photolithography technique using a contact alinger with an I-line source. After via formation the under ball metallurgy (UBM) structure with Ti-adhesion and Cu-seed layers is sputtered on a sample. Cu-layer and Sn/pb-layer with a competition ratio of 6 to 4 are electroplated by a selective electroplating method. The reflow-bump diameters at bottom are unchanged, compared with as-electroplated diameters. As-electroplated- and reflow-bump shapes, however, depend significantly on the via size. The heights of as-electroplated and reflow bumps increase with the larger cia, while the aspect ratio of bump decreases. The nearest bumps may be touched by decreasing the bump pitch in order to obtain high-density bump. The touching between the nearest bumps occurs during the overplating procedure rather than the reflowing procedure because the mushroom diameter formed by overplating is larger than the reflow-bump diameter. The arrangement as zig-zag rows can be effective for realizing the flip-chip-interconnect bump with both high-density and high-aspect ratio.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.79-85
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• 2007

This study was focused on the feasibility of ultrasonic bonding of Au stud flip chip bumps on the flexible printed circuit board (FPCB) with three different surface finishes: organic solderability preservative (OSP), electroplated Au and electroless Ni/immersion Au (ENIG). The Au stud flip chip bumps were successfully bonded to the bonding pads of the FPCBs, irrespective of surface finish. The bonding time strongly affected the joint integrity. The shear force increased with increasing bonding time, but the 'bridge' problem between bumps occurred at a bonding time over 2 s. The optimum condition was the ultrasonic bonding on the OSP-finished FPCB for 0.5 s.

• Design & Manufacturing
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• v.13 no.4
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• pp.10-16
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• 2019

Semiconductor chip is bonded to the substrate by melting solder bumps. In general, the chip bonding is applied by a Reflow process or a Thermo-Compression(TC) bonding process. In this paper, we introduce a Laser Assisted Thermo-Compression bonding (LATCB) process to improve the anxiety of the existing process(Reflow, TC bonding). In the LATCB process, the chip is bonded to the substrate by irradiating a laser with a uniform energy density in the same area as the chip to melt only the solder bumps and press the chip with a Transparent Compression Module (TCM). The TCM consists of a fused silica header for penetrating the laser and pressurizing the chip, and a piezoelectric actuator (P.A.) coupled to both ends of the header for micro displacement control of the header. In addition, TCM is a structure that can pressurize the chip and deliver it to the chip and solder bumps without losing the energy of the laser. Fused silica, which is brittle, is vulnerable to deformation, so the header may be damaged when an external force is applied for pressurization or a displacement differenced is caused by piezoelectric actuators at both ends. On the other hand, in order to avoid interference between the header and the adjacent chip when pressing the chip using the TCM, the header has a notch at the bottom, and breakage due to stress concentration of the notch is expected. In this study, the thickness and notch length that the header does not break when the external force (500 N) is applied to both ends of the header are optimized using structural analysis and Coulomb-Mohr failure theory. In addition, the maximum displacement difference of the P.A.s at both ends where no break occurred in the header was derived. As a result, the thickness of the header is 11 mm, and the maximum displacement difference between both ends is 8 um.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.67-72
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• 2012

In recent days, the wire width of IC is narrowed and the degree of integration of IC is increased to obtain the higher capacity of the devices in electronic industry. And then the surface quality of FCCL(Flexible Copper Clad Laminate) became increasingly important. Surface defects on FCCL are bump, scratch, dent and so on. In particular, bumps cause low reliability of the products. Even though there are bumps on the surface, if leveling characteristic of plating solution is good, it does not develop significant bump. In this study, the leveling characteristics of additives are investigated. The objective of study is to improve the leveling characteristic and reduce the surface step through additives and plating conditions. The additives in the electrodeposition bath are critical to obtain flat surface and free of defects. In order to form flat copper surface, accelerator, suppressor and leveler are added to the stock solution. The reason for the addition of leveler is planarization surface and inhibition of the formation of micro-bump. Levelers (SO(Safranin O), MV(Methylene Violet), AB(Alcian Blue), JGB(Janus Green B), DB(Diazine Black) and PVP(Polyvinyl Pyrrolidone) are used in copper plating solution to enhance the morphology of electroplated copper. In this study, the nucleation and growth behavior of copper with variation of additives are studied. The leveling characteristics are analyzed on artificially fabricated Ni bumps.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.1
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• pp.47-54
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• 2021

For the bonding of smaller PCB solder bumps of less than 100 microns, an experiment was performed to make up a tin plating solution and find plating conditions in order to produce a bump pattern through tin electroplating, replacing the previous PCB solder bumps process by microballs. After SR patterning, a Cu seed layer was formed, and then, through DFR patterning, a pattern in which Sn can be selectively plated only within the SR pattern was formed on the PCB substrate. The tin plating solution was made based on methanesulfonic acid, and hydroquinone was used as an antioxidant to prevent oxidation of divalent tin ions. Triton X-100 was used as a surfactant, and gelatin was used as a grain refiner. By measuring the electrochemical polarization curve, the characteristics of organic additives in Triton X-100 and gelatin were compared. It was confirmed that the addition of Triton X-100 suppressed hydrogen generation up to -1 V vs. NHE, whereas gelatin inhibited hydrogen generation up to -0.7 V vs. NHE. As the current density increased, there was a general tendency that the grain size became finer, and it was observed that it became finer when gelatin was added.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.10a
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• pp.7-38
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• 2000

Performance, reliability, form factor drive flip chip use. BGAs and CSPs will provide stepping stone to FC DCA .Growing vendor infrastructure - Low cost, high density organic substrates -New generations of fluxes and underfills .Adhesives flip chip technology as a low cost flip chip alternatives -Low cost Au stud or Electroless Ni bumps -Reliable thermal cycling and electrical performance.

• Tribology and Lubricants
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• v.16 no.4
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• pp.295-301
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• 2000

The dynamic simulation of slider in hard disk drive is performed using Factored Implicit Finite Difference method. The modified Reynolds equation with Fukui and Kaneko model is employed as a governing equation. Equations of motion for the slider of three degrees of freedom are solved simultaneously with the modified Reynolds equation. The transient responses of the slider for disk step bumps and slider impulse forces are shown for various cases and are compared for the iteration algorithm and new algorithm.

• Publications of The Korean Astronomical Society
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• v.13 no.1 s.14
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• pp.111-122
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• 1998

Among the sample of red giant stars in the globular clusters M3 and M13 whose CN bands $(3883{\AA})$ have been measured by various authors, the stars on the red giant evolutionary state are selected to have their CN band distributions. It is found that all stars brighter than Mv = 0, are CN-strong in M3, while all stars except IV-29 are CN-strong in M13. It hints that the onset of meridional mixing is related with the RGB bumps of the clusters.