• Journal of Welding and Joining
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• v.13 no.2
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• pp.82-95
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• 1995

This paper discusses distribution of thermal stress, strain at near the joint and investigates the reliability of solder joints of electronic devices on a printed circuit board. As Electronic devices are composed of different materials, thermal stresses generate at near the interface, such as solder joints and interface between lC device and lead frame pad due to the differences of thermal expansion coefficients, As results of thermal stress, strain, micro crack often occurs thermal fatigue fracture at the interface of different materials, The initiation and propagation of micro crack depend on the environmental conditions, such as storage temperature and thermal cycling. Finally, this paper experimentally shows a way to suppress micro cracks by using Fe-Ni alloy clad lead frame, and investigates crack and thermal fatigue fracture of TSOP(Thin small outline package) type on printed circuit board.

• Laser Solutions
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• v.2 no.1
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• pp.38-42
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• 1999

As very large scale integration technology has been developed, much more accurate, reliable technology is needed for outer lead bonding. Laser soldering has been researched as an alternative for fine pitch device bonding. This study is focused on how to select optimal laser soldering variables with which solder wets parent material, the microstructural results of laser soldering and the reliability test One of popular packages, QFP100 was soldered successfully with two kinds of solder. The inspection of the joint for reliability was carried out by optical microscope, SEM, EDAX and pull test, which demonstrated the superiority of laser soldering.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.60-67
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• 2014

The ability of electronic packages and assemblies to resist solder joint failure is becoming a growing concern. This paper reports on a study of high speed shear energy of Sn-4.0wt%Ag-0.5wt%Cu (SAC405) solder with different electroless Ni-P thickness, with $HNO_3$ vapor's status, and with various pre-conditions. A high speed shear testing of solder joints was conducted to find a relationship between the thickness of Ni-P deposit and the brittle fracture in electroless Ni-P deposit/SAC405 solder interconnection. A focused ion beam (FIB) was used to polish the cross sections to reveal details of the microstructure of the fractured pad surface with and without $HNO_3$ vapor treatment. A scanning electron microscopy (SEM) and an energy dispersive x-ray analysis (EDS) confirmed that there were three intermetallic compound (IMC) layers at the SAC405 solder joint interface: $(Ni,Cu)_3Sn_4$ layer, $(Ni,Cu)_2SnP$ layer, and $(Ni,Sn)_3P$ layer. The high speed shear energy of SAC405 solder joint with $3{\mu}m$ Ni-P deposit was found to be lower in pre-condition level#2, compared to that of $6{\mu}m$ Ni-P deposit. Results of focused ion beam and energy dispersive x-ray analysis of the fractured pad surfaces support the suggestion that the brittle fracture of $3{\mu}m$ Ni-P deposit is the result of Ni corrosion in the pre-condition level#2 and the $HNO_3$ vapor treatment.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.270-274
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• 2002

We have developed a new COG technique using flip chip solder joining technology for excellent resolution and high quality LCD panels. Using the eutectic Bi-Sn and the eutectic In-Ag solder bumps of 50-80 ${\mu}m$ pitch sizes, a ultrafine interconnection between IC and glass substrate was successfully made at or below $160^{\circ}C$. The contact resistance and reliability of Bi-Sn solder joint showed the superiority over the conventional ACF bonding.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.35-40
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• 2007

The pull strength and fracture mechanism were investigated to evaluate the reliability and compatibility of Sn-8Zn-3Bi joints, the solder paste on lead and lead-free plating under thermal shock conditions. At the Sn-8Zn-3Bi solder joint, no crack initiation was observed during thermal shock test. After 1000 cycles, the strength of the solder joint decreased not sharply but reduced gradually compared with initial conditions. The decrement of strength was affected by ${\gamma}-Cu_5Zn_8$ IMC growth which caused the IMC fracture on the fracture surface and a change in fracture mode and initial crack point. Clearly, the Sn-8Zn-3Bi solder shows good reliability properties and compatibility with lead-free plated Cu LF under thermal shock temperatures between 248K and 423K.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 1999.12a
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• pp.63-85
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• 1999

$\cdot$New CSP using Lead Frame and solder ball techniques. $\cdot$EMC needs high filler content, low CTE and high flexural modulus. $\cdot$Solder Joint Reliability improved by anchor leads. .Uniform inner lead shape would be better at capacitance values. $\cdot$Low Assembly cost CSP.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.222-222
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• 2007

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.69-74
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• 2015

With difficulties during the cleaning of reflow flux residues due to the decrease of the part size and interconnection pitch in the advanced electronic devices, the need for the no-clean solder paste is increasing. In this study, an epoxy curable solder paste was made with SAC305 solder powder and the curable flux of which the main ingredient is epoxy resin and its reflow solderability, flux residue corrosivity and solder joint mechanical properties was investigated with comparison to the commercial rosin type solder paste. The fillet shape of the cured product around the reflowed solder joint revealed that the curing reaction occurred following the fluxing reaction and solder joint formation. The copper plate solderability test result also revealed that the wettability of the epoxy curable solder paste was comparable to those of the commercial rosin type solder pastes. In the highly accelerated temperature and humidity test, the cured product residue of the curable solder paste showed no corrosion of copper plate. From FT-IR analysis, it was considered to be resulted from the formation of tight bond through epoxy curing reaction. Ball shear, ball pull and die shear tests revealed that the adhesive bonding was formed with the solder surface and the increase of die shear strength of about 15~40% was achieved. It was considered that the epoxy curable solder paste could contribute to the improvement of the package reliability as well as the removal of the flux residue cleaning process.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.254-256
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• 2007

In this paper, the effects of the reflow number in the mechanical reliability of flip chip solder joint was investigated by flip chip shear test and thermal shock test. For evaluation mechanical reliability of flip chip, We experiment that specimens were operated 3-times, 6-times, 9-times, 12-times under reflow Process. After shear test and thermal shock test, We measured max shear strength and coming first crack number of thermal cycle. And We observe fracture surface and cross section by using SEM(Scanning Electron Microscope) and optical scope. In the results, the more specimens were operated reflow process, the more decreased maximum shear strength and number of thermal cycle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.209-210
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• 2008