Soon-Min Hong

Presence of Porphyromonas gingivalis and plasma cell dominance in gingival tissues with periodontitis

OBJECTIVE Porphyromonas gingivalis can invade and survive within its host epithelial cells. The aim of this study was to test our hypothesis that persistent presence of intracellular periodontal pathogens in gingival tissue causes the chronic inflammation and that an inappropriate immune response is a risk factor for periodontitis. METHODS Together with the presence of P. gingivalis, the distribution of B cells, plasma cells, and CD4(+), CD8(+), and FOXP3(+) regulatory T cells was evaluated in gingival tissues from healthy (n = 7) and periodontitis (n = 8) sites by in situ hybridization and immunohistochemistry, respectively. RESULTS Porphyromonas gingivalis was detected in proximity to inflammatory infiltrates in three and seven biopsies from the healthy and periodontitis sites, respectively. Compared with healthy sites, periodontal lesions contained a significantly increased number of each immune cell studied with a relative dominance of plasma cells over T cells. CONCLUSIONS Persistent bacterial invasion of gingival tissues in combination with a plasma cell-dominant immune response may be involved in the pathogenesis of periodontitis.

Fluxless wetting properties of one-side-coated under bump metallurgy and top surface metallurgy

The wetting balance test was performed in an attempt to estimate the fluxless wetting properties of under bump metallurgy (UBM)-coated Si-wafer and top surface metallurgy (TSM)-coated glass substrate to SnPb solder. The wetting curves of the single-and double-side-coated UBM had a similar shape and the parameters characterizing the curve shape showed a similar tendency as a function of temperature. Wetting property estimation was possible with the new wettability indices from the wetting curves of one side-coated specimens; Fmin, Fs, and ts. Au/Cu/Cr UBM was better than Au/Ni/Ti UBM from the point of wetting time. For TSM, it was more effective to use Cu as a wetting layer with Au as a protection layer than to use Au as a wetting layer alone. The contact angle of one-side-coated Si-plate to SnPb solder can be calculated from the force balance equation by measuring static state force and tilt angle. The contact angles of Au/Cu/Cr and Au/Ni/Ti UBM of Si-wafer to SnPb solder were 59.9° and 63.9°, respectively. The contact angles of Au/Cu/Cr and Au/Cr TSM of glass to SnPb were 78.9 and 76.1°, respectively.

Fluxless solder bumping in flip chip package by plasma reflow

A new fluxless reflow process using Ar+10%H/sub 2/ plasma was investigated for application to solder bump flip chip packaging. The 100 /spl mu/m-diameter Sn-3.5wt%Ag solder balls were bonded to 250 /spl mu/m pitch Cu/Ni under bump metallurgy (UBM) pattern by laser solder ball bumping method. Then, the Sn-Ag solder balls were reflowed in Ar+H/sub 2/ plasma. Without flux, the wetting between solder and UBM occurred in Ar+H/sub 2/ plasma. During plasma reflow, the solder bump reshaped and the crater on the top of bump disappeared. The bump shear strength increased as the Ni/sub 3/Sn/sub 4/ intermetallic compounds formed on initial reflow stage but began to degrease as coarse (Cu,Ni)/sub 6/Sn/sub 5/ grew at solder/UBM interface. As the plasma reflow time increased, the fracture within solder bulk decreased and the fracture along solder/UBM interface increased. The off-centered bumps self-aligned to UBM pattern during plasma reflow. The solder ball defect occurred in high power and a long time plasma reflow.