Byunghoon Lee

A Study on the Bonding Process of Cu Bump/Sn/Cu Bump Bonding Structure for 3D Packaging Applications

This study reports the kinetics of the bonding process of a Cu bump/10 μm thick Sn bonding layer/Cu bump bonding structure, popularly adopted for three-dimensional (3D) packaging, and the mechanical properties of the joints. Characterizing the bonding morphologies of the joints using scanning electron microscopy disclosed that a drastic intermetallic phase transformation occurred around the melting temperature of Sn in a manner similar to the wetting process of SnPb solder on Cu. We also delved into the mechanical behavior of the joints using lap-shear testing to illuminate that a unique feature of the joints is a lack of ductility. In addition, the samples exhibited a sensitive dependence of the joint strength on the bonding conditions (temperature and pressure).

Infrapatellar fat pad preservation reduces wound complications after minimally invasive total knee arthroplasty

IntroductionThe aim of this study was to determine whether pain intensity and wound complication rates differ between patients with and without preservation of the infrapatellar fat pad (IPFP) after minimally invasive total knee arthroplasty (TKA). The authors also sought to determine whether IPFP preservation affects operation time.Materials and methodsThis retrospective study included 448 knees with primary TKA. The IPFP was totally resected in 201 knees (IPFP-R group), and was preserved in 247 knees (IPFP-P group). Pain score was determined using the visual analog scale during the first 72xa0h after surgery. Wound complication rates and operation times were also evaluated. A wound complication was defined as persistent wound drainage for three or more days after surgery.ResultsThere was no difference in pain levels between the two groups. However, there were fewer wound complications in the IPFP-P group (3xa0%) than in the IPFP-R group (13xa0%). The operation time was longer in the IPFP-P group than in the IPFP-R group (70 vs. 64xa0min, respectively).ConclusionsAlthough IPFP preservation delayed operation time, it decreased wound complications after MIS TKA. These findings are important to consider when deciding whether or not to resect the IPFP. Whenever possible, IPFP preservation is probably the preferred technique to reduce wound complications.

A Study on the Breakdown Mechanism of an Electroless-Plated Ni(P) Diffusion Barrier for Cu/Sn/Cu 3D InterconnectBonding Structures

This study examined the thermal stability of an electroless-plated Ni(P) barrier layer inserted between Sn and Cu in the bonding structure of Cu/Sn/Cu for three-dimensional (3D) interconnect applications. A combination of transmission electron microscopy (TEM) and scanning electron microscopy allowed us to fully characterize the bonding morphology of the Cu/Ni(P)/Sn/Ni(P)/Cu joints bonded at various temperatures. The barrier suppressed Cu and Sn interdiffusion very effectively up to 300°C; however, an interfacial reaction between Ni(P) and Sn led to gradual decomposition into Ni3P and Ni3Sn4. Upon 350°C bonding, the interfacial reaction brought about complete disintegration of the barrier in local areas, which allowed unhindered interdiffusion between Cu and Sn.

Prevention of pseudo-patella baja during total knee arthroplasty

AbstractPurposePseudo-patella baja (PPB) is a surgical complication that can arise from total knee arthroplasty and occurs when the patella tendon is not shortened but the level of the femorotibial joint line is elevated. The goal of this study was to assess the performance of a technique specifically designed to prevent the occurrence of PPB and its radiological results.MethodsNinety-nine patients undergoing total knee arthroplasty were included. Patients were divided into a non-correction group and a correction group. The correction group were applied an additional metal block in order to reduce the excess resection of the distal femur. To evaluate PPB, the change in the pre- and postoperative joint line was measured using the modified Blackburne–Peel Index (BPI).nResultsIn the non-correction group, 68 of 74 cases showed an occurrence of PPB (92xa0%), in the correction group, 6 of 57 cases showed an occurrence of PPB (11xa0%). The preoperative-modified BPI of the non-correction group was not significantly different from that of the correction group (0.6xa0±xa00.1 vs. 0.6xa0±xa00.2). The modified BPI decreased significantly in the non-correction group after TKA (0.6xa0±xa00.1 vs. 0.2xa0±xa00.1, pxa0<xa00.05). However, the modified BPI did not change significantly in the correction group after TKA (0.6xa0±xa00.2 vs. 0.6xa0±xa00.2).ConclusionThe comparison of preoperative and postoperative radiological results showed that our intervention maintained the joint line without elevation. We proposed an effective method to prevent various complications due to the joint line elevation that occur in PPB.Level of evidenceIII.

Soft tissue laxity should be considered to achieve a constant polyethylene thickness during total knee arthroplasty

IntroductionIn total knee arthroplasty (TKA), the gap expansion effect by soft tissue laxity and bone resection amount influence directly on the proper gap size and ideal polyethylene insert thickness. In this study, we hypothesized if bone resection level could be controlled lesser as gap expansion effect resulted in the effects on gap expansion of the collateral release and lax lateral structure, appropriate gap size would be attained without extensive medial soft tissue release even in severe varus deformed knee. The purpose of this study was to show the usefulness of preoperative calculation of soft tissue laxity for determining the appropriate gap size for the targeted PE thickness in TKA.MethodsThe preoperative varus stress view was used to estimate the effect of soft tissue release on extension gap expansion after primary bone resection. The amount of bone resection was determined with a parallel bone resection device used in our institution. Lateral laxity amount was applied into the device. This study was a retrospective review of 850 TKAs [451 with <10º varus deformity of the mechanical femoro-tibial angle (group 1); 399 with ≥10º varus deformity (group 2)] with a minimum follow-up of 1xa0year. We compared the range of motion (ROM), the knee society score (KSS), and the incidence of surgical complications at postoperative 1xa0year between the two groups.ResultsThe mean PE thickness was 10.8xa0±xa01.1 in group 1 and 10.9xa0±xa01.1 in group 2. The proportion of patients with appropriate PE thickness (i.e., 10–12xa0mm) was 97.6xa0% in group 1 and 97.2xa0% in group 2. The ROM and KSS did not differ significantly between groups.ConclusionThis study showed the usefulness of preoperative calculation of soft tissue laxity for appropriate gap size for targeted polyethylene thickness and possibility to attain constant extension gap regardless of preoperative varus deformity.

Disparate Postoperative Results in the First and Second Knees on Simultaneous Bilateral Total Knee Arthroplasty

We hypothesized that the circumstances of the two consecutive operations of a simultaneous bilateral total knee arthroplasty (TKA) are different, and could lead to different outcomes of overlapping bilateral TKAs. Both knees of 420 subjects were evaluated in the current study. In the second TKA, there were more incidence rates of outlier in mechanical femoro-tibial angle (16.2% vs. 9.0%), more blood loss (735 vs. 656 mL), and longer operation time (61, 58 minutes respectively), as compared to the first TKA, while no significant differences in clinical outcomes. In conclusion, there were no significant differences in the clinical outcomes even though few distinct outcomes due to different circumstances of the surgery. Awareness of these findings can help the continued success of bilateral TKA in an increasing patient population.

HV PMOSFET Vth (threshold voltage) shift caused by HEIP after HTOL

After PLR(product level reliability) HTOL(high temperature operating lifetime) test of HV PMOSFET, Vth (threshold voltage) shift is observed to increase due to PMOSFET leakage current, which is caused by Hot Electron Induced Punch Through(HEIP). Generally, LCD display driver IC requires high voltage of more than 10V and adopts MTI(middle trench isolation) scheme which is deeply trenched to get isolation characteristics on the high voltage according to chip shrinkage. It was found that electron trapping at interface between sidewall oxide and nitride liner in middle trench isolation(MTI) induces channel shorting at the corner of transistor, thereby resulting in the leakage current. In this paper, we propose the optimized sidewall thickness and the effectiveness of additional annealing process which have strong resistance against hot electron induced punch through regarding that offset leakage current is increased after HTOL(high temperature operating lifetime) stressing test for devices prepared with MTI processing scheme and it might be improved by the optimization of sidewall oxide thickness. Therefore, the threshold voltage(Vth) shift is seriously reduced due to the increase of immunity on the hot electron induced punch-through(HEIP) according to the increase of the sidewall thickness and adding annealing process as the thermal oxide layer of high temperature.

Microstructure evolution of Cu/Sn/Cu bonding stacks impacts on their mechanical properties

We examined the effects of the bonding temperature on the bonding morphology, electrical resistance and mechanical properties of a Cu/Sn/Cu bonding structure. By carefully characterizing the bonding morphology using several analytical methods (SEM, TEM, and EDS), we successfully unravelled that bonding the samples under various bonding temperatures produced greatly different bonding morphologies — and different prevailing phases in the bonded layer. Mechanically testing the samples bonded under different conditions generates the joint strength data of the samples, which confirm a sensitive dependence of the joint strength on the bonding conditions. In general, the samples bonded at the higher temperatures show a higher bonding strength and the strength escalates with the bonding temperature increasing. Connecting the mechanical data with the SEM analysis results reveals an intimate process-microstructure-property interrelationship that bonding samples under various process conditions produce different microstructures, which, in turn, lead to much different joint strengths.