This study examined the effect of surface treatment with sandblasting on bracket bonding strength. Extracted human tooth, base metal alloy and porcelain surfaces were treated with sandblasting. The bracket bonding strengths of sandblasted surfaces were evaluated and compared with the controls and etched enamel surfaces. Morphological observation of the treatment surfaces and the failure sites was conducted. Statistical analysis included one-way analysis of variance (ANOVA) and a Scheffe's F-test at the 95% confidence level was performed. The results indicated that mean bond strength values ranged from 3.6 MPa (the untreated control) to 20.4 MPa for the etched enamel surface. No statistically significant differences were determined among the etched enamel, sandblasted metal and sandblasted porcelain surfaces (P > 0.05). Most debonding specimens failed at either the resin-tooth interface or within the adhesive. In conclusion, sandblasting the metal and porcelain surfaces obtained a bracket bond strength comparable with that with the etched enamel surface.
Due to an increasing demand for smaller and higher density packages, Tessera developed pBGA@ technology as a cost-effective solution for chip-size packaging. Many companies including Intel, 3M, Samsung, Amkor, etc. have licensed the technology since 1995. As a current, leading technology for Chip Scale Packaging (CSP), a pBGA@ package typically has a compliant layer between the die and the flex interposer to eliminate strain on solder balls by thermal mismatch of the die and printed wire board (PWB). Historically, a silicone-based encapsulant has been the material of choice for this application. However, for hard disk drive and other applications with zero tolerance of siloxane outgassing, a non-silicone encapsulant having excellent reliability performance is highly desired.A novel 3M epoxy encapsulant with excellent hydrophobicity has been developed for an advanced pBGA@ package platform. The new epoxy encapsulant is designed to meet the requirements of compliancy with good moisture resistance. This new material has demonstrated JEDEC level 1 reliability. During thermal cycling tests, the new encapsulant far surpassed 1000 cycles, both on-and off-board, and survived high temperature aging, as well as 500 hours of pressure cooker testing (PCT). This paper will describe physical properties and reliability performances of the new 3M encapsulant material with emphasis on its hydrophobicity and compliancy. Improvement in reliability trends for pBGA@ technology will also be reviewed.
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