Search results

1 – 10 of 11
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 3 July 2007

Mi Jin Kim, Y. (Norman) Zhou and Jae Pil Jung

This paper seeks to decrease the soldering temperature of capacitors using Sn‐Bi plated Sn‐3.5 wt%Ag solder.

407

Abstract

Purpose

This paper seeks to decrease the soldering temperature of capacitors using Sn‐Bi plated Sn‐3.5 wt%Ag solder.

Design/methodology/approach

Sn‐Bi layers were electroplated on Sn‐3.5 wt%Ag solder. As soldering examples, type 1608 capacitors electroplated with Sn, and printed circuit boards (PCBs) with a surface coating of electroless‐plated Ni/Au, were selected. Sn‐3.5Ag foil coupons plated with Sn‐95.7 wt%Bi were inserted as solder between the capacitors and the lands on the PCBs. The samples were reflowed at 220°C, which is below the normal reflow temperatures of around 240 ∼ 250°C used with Pb‐free solders. During heating, Bi in the plated layer diffuses into the Sn‐3.5Ag core solder resulting in a transient decrease in soldering temperature based on the concept of transient liquid phase bonding.

Findings

The joints made with the Sn‐95.7%Bi plated Sn‐3.5Ag solder at 220°C showed good appearance, and evidence of significant Bi segregation was absent in the microstructure. The shear strengths of the capacitor joints bonded with Sn‐95.7%Bi plated Sn‐3.5%Ag solder were approximately 5,000‐6,000 gf. After 1,000 thermal cycles between −40 and +125°C, the shear strengths of the joints decreased approximately 5‐10 percent from the strengths in the as‐reflowed state for all plated solders. This confirmed that the soldered joints were stable and not significantly degraded by thermal cycles.

Originality/value

Reduced temperature soldering using Sn‐Bi plated Sn‐3.5%Ag solder was applied to attach capacitors to PCBs. In a production application, the foil coupons could be replaced by pre‐solder on the PCB pads.

Details

Soldering & Surface Mount Technology, vol. 19 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Article
Publication date: 1 June 2005

Joon Kwon Moon, Y. Zhou and Jae Pil Jung

To investigate fluxless plasma ball bumping and effect of under bump metallization (UBM) thickness on joint properties using lead‐free solders.

386

Abstract

Purpose

To investigate fluxless plasma ball bumping and effect of under bump metallization (UBM) thickness on joint properties using lead‐free solders.

Design/methodology/approach

A fluxless soldering process was investigated in this study using Ar‐10 percent H2 plasma reflow. Balls made from two lead‐free solders (Sn‐3.5 weight percent Ag and Sn‐3.5 weight percent Ag‐0.7 weight percent Cu) were reflowed and, also Sn‐37 weight percent Pb as a reference. In particular, the effects of the UBM thickness on the interfacial metallurgical bonding and joint strength were studied. The UBM (Au/Cu/Ni/Al layers) thicknesses were 20 nm/0.3 μm/0.4 μm/0.4 μm and 20 nm/4 μm/4 μm/0.4 μm, respectively.

Findings

The experimental results showed that in the case of a thin UBM the shear strengths of the soldered joints were relatively low (about 19‐27 MPa) due to cracks observed along the bond interfaces. The thick UBM improved joint strength to 32‐42 MPa as the consumption of the Cu and Ni layers by reaction with the solder was reduced and hence the interfacial cracks were avoided. To provide a benchmark, reflow of the solders in air using flux was also carried out.

Originality/value

This paper provides information about the effect of UBM thickness on joint strength for plasma fluxless soldering to researchers and engineers.

Details

Soldering & Surface Mount Technology, vol. 17 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Article
Publication date: 1 August 2003

Hyeon Hwang, Soon‐Min Hong, JaePil Jung and Choon‐Sik Kang

Sn‐Pb and Sn‐Ag bumps (130 μm diameter, 250 μm pitch) made using an electroplating process were studied. As a preliminary experiment, the effects of current density and plating…

651

Abstract

Sn‐Pb and Sn‐Ag bumps (130 μm diameter, 250 μm pitch) made using an electroplating process were studied. As a preliminary experiment, the effects of current density and plating time on the Sn‐Pb and Sn‐Ag deposits were investigated. The morphology and composition of the plated surface were examined using scanning electron microscopy. The shape and thickness of the solder bumps were also compared. Bump shear testing was performed to measure the adhesion strength between the solder bumps and the under bump metallurgy. In electroplating, the Sn‐Ag plating thickness was proportional to the current density, while plated Sn‐Pb thickness saturated above the limiting current density. The optimal conditions for solder bump fabrication were found at 6 A/dm2 for 3 h in the case of Sn‐Pb bump plating and 6 A/dm2 for 1 h for the Sn‐Ag bump plating. The bump shear strength for Sn‐Ag was found to be higher than that of Sn‐Pb.

Details

Soldering & Surface Mount Technology, vol. 15 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Article
Publication date: 6 February 2009

Kyoo‐Seok Kim, JaePil Jung and Y. Norman Zhou

The aim of the paper is to study the feasibility of direct ultrasonic bonding between contact pad arrays on flexible printed circuit boards (FPCB) and rigid printed circuit boards…

795

Abstract

Purpose

The aim of the paper is to study the feasibility of direct ultrasonic bonding between contact pad arrays on flexible printed circuit boards (FPCB) and rigid printed circuit boards (RPCB) at ambient temperature.

Design/methodology/approach

Metallization layers on the RPCB comprised Sn on Cu while the pads on the FPCB consisted of Au/Ni/Cu. Prepared RPCB and FPCB were bonded by ultrasound at ambient temperature using an ultrasonic frequency of 20 kHz, a power of 1,400 W, and 0.62 MPa of bonding pressure. The bonded samples were cross‐sectioned and the joints and microstructures were observed by Field Emission Scanning Electron Microscopy (FE‐SEM) and Energy Dispersive Spectroscopy (EDS). The soundness of the joints was evaluated by pull testing.

Findings

Robust bonding between FPCB and RPCB was obtained by bonding for 1.0 and 1.5 s. This result has confirmed that direct room temperature ultrasonic bonding of Au and Sn is feasible. At a longer bonding time of 3.0 s, cracks and voids were found in the joints due to excessive ultrasonic energy. The IMC (intermetallic compound) between the Sn layer and pads of the RPCB was confirmed as Cu6Sn5. On the FPCB side, Cu6Sn5 and Ni3Sn4 were formed by contact with the facing Sn coating, and mechanically alloyed Cu0.81Ni0.19 was found within the pads. Meanwhile, the strength of bonded joints between FPCB and RPCB increased with bonding time up to 1.5 s and the maximum value reached 12.48 N. At 3.0 s bonding time, the strength decreased drastically, and showed 5.75 N. Footprints from the fracture surfaces showed that bonding started from the edges of the metal pads, and extended to the pad centers as ultrasonic bonding time was increased.

Originality/value

Direct ultrasonic bonding with transverse vibration at ambient temperature between the surface layers of the pads of FPCB and RPCB has been confirmed to be feasible.

Details

Soldering & Surface Mount Technology, vol. 21 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Available. Content available
Article
Publication date: 6 February 2009

Martin Goosey

310

Abstract

Details

Soldering & Surface Mount Technology, vol. 21 no. 1
Type: Research Article
ISSN: 0954-0911

Access Restricted. View access options
Article
Publication date: 22 March 2019

Tae Wan Kim

The purpose of this paper is to examine regional voting patterns in South Korea using the results from six presidential elections since the 1990s.

152

Abstract

Purpose

The purpose of this paper is to examine regional voting patterns in South Korea using the results from six presidential elections since the 1990s.

Design/methodology/approach

A χ2 test was used to determine the municipalities where a regional voting pattern emerged, and λ correlation coefficients were calculated to examine changes in the regional voting patterns.

Findings

The analyses lead to three key findings. First, voting patterns differ in Yeongnam and Honam: regional voting in Yeongnam is getting weaker, it remains strong in Honam. Second, the tendency to vote along regional lines decreased significantly in the election in which the Honam party fielded a candidate with a Yeongnam appeared identity. Third, regional voting patterns declined but then stabilized at a constant level, regardless of the candidates’ local identity, which was confirmed in “Bu-Ul-Gyeong.”

Originality/value

This paper can empirically verify the manifestation of regional voting pattern and confirm the trend. It is possible to derive a condition for suppressing the regional voting pattern.

Details

Asian Education and Development Studies, vol. 8 no. 3
Type: Research Article
ISSN: 2046-3162

Keywords

Access Restricted. View access options
Book part
Publication date: 9 May 2022

Tobin Im

Abstract

Details

Transformation of Korean Politics and Administration: A 30 Year Retrospective
Type: Book
ISBN: 978-1-80382-116-0

Access Restricted. View access options
Book part
Publication date: 9 May 2022

Tobin Im

Abstract

Details

Transformation of Korean Politics and Administration: A 30 Year Retrospective
Type: Book
ISBN: 978-1-80382-116-0

Access Restricted. View access options
Book part
Publication date: 9 May 2022

Tobin Im

Abstract

Details

Transformation of Korean Politics and Administration: A 30 Year Retrospective
Type: Book
ISBN: 978-1-80382-116-0

Available. Open Access. Open Access
Article
Publication date: 31 August 2014

Seong-Gyu Jeon and Yong Jin Kim

The weapon system of The Navy is the small quantity producing system on multiple kinds. It is consisted of various equipment and the subordinate parts of those which can repair…

293

Abstract

The weapon system of The Navy is the small quantity producing system on multiple kinds. It is consisted of various equipment and the subordinate parts of those which can repair the damaged part. The operating procedure concerning warship's repair parts managed under these systems is as follows. Firstly, if demand of repair parts occurs from warship which is the operating unit of weapon, then the Fleet(the repair & supply support battalion) is in charge of dealing with these requests. If certain request from warship is beyond the battalion's capability, it is delivered directly to the Logistic Command. In short, the repair and supply support system of repair parts can be described as the multi-level support system. The various theoretical researches on inventory management of Navy's repair parts and simulation study that reflects reality in detail have been carried out simultaneously. However, the majority of existing research has been conducted on aircraft and tank's repairable items, in that, the studies is woefully deficient in the area concerning Navy's inventory management. For that reason, this paper firstly constructs the model of consumable items that is frequently damaged reflecting characteristics of navy's repair parts inventory management using ARENA simulation. After that, this paper is trying to propose methodology to analyze optimal inventory level of each supply unit through OptQuest, the optimization program of ARENA simulation.

Details

Journal of International Logistics and Trade, vol. 12 no. 2
Type: Research Article
ISSN: 1738-2122

Keywords

1 – 10 of 11
Per page
102050