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The interfacial reaction between eutectic Sn-3.5wt.%Ag solder and Ni substrate resulted in the formation of Ni3Sn4 intermetallic compound (IMC) layer. After formation of the Ni3Sn4 IMC, its grain coarsened and faceted continuously in a prolonged reflow reaction. The thickness of the IMC layer increased with reflow time. On the other hand, the brittleness of the joints increased with increasing reflow time, and the fracture occurred at the interface. The deterioration of the shear strength was found to be predominantly caused by the formation of the thick Ni3Sn4 IMC layer.

The interfacial reaction and morphology change of intermetallic compound (IMC) between the Sn–0.4 wt.% Cu solder and two different kinds of substrates (Cu and electroless nickel-immersion gold (ENIG)) during reflow at 255 °C for up to 60 min were studied. Until the reaction time of 1 min, only Cu 6 Sn 5 IMC was formed on the Cu substrate. After reflow for 5 min, the solder/Cu interface exhibited a duplex structure of Cu 6 Sn 5 and Cu 3 Sn. According to the top view observation, the Cu 6 Sn 5 IMC formed on the Cu substrate had a well-known morphology of a round or scallop shape. In the case of the ENIG substrate, the reaction between molten Sn–0.4Cu solder and electroless Ni–P layer resulted in the formation of a (Ni,Cu) 3 Sn 4 layer at the interface. Until the reaction time of 10 min (Ni,Cu) 3 Sn 4 IMC layer was formed and attached well on the electroless Ni substrate. And, the Cu content in the (Ni,Cu) 3 Sn 4 IMC layer increased with increasing reaction time. From the top view micrograph of the interface, it was known that three types (needle-type, boomerang-type and chunk-type) of (Ni,Cu) 3 Sn 4 IMC were formed. Also, P-rich Ni (Ni 3 P) and Ni–Sn–P layers were observed between IMC layer and electroless Ni–P layer. On the other hand, the reaction for 60 min resulted in the formation of two IMCs, a relatively thin and continuous (Ni,Cu) 3 Sn 4 and a relatively big discontinuous (Cu,Ni) 6 Sn 5 , at the interface. After reflow for 60 min, the electroless Ni–P layer in some parts of the sample was completely consumed by reaction between molten solder and substrate.

The interfacial reaction, morphology of intermetallic compound (IMC) and shear strength between the Sn–3.5Ag–0.7Cu (in wt.%) solder and Ni ball grid array (BGA) substrates during reflow at 255 °C for up to 20 min were investigated. The reaction between the molten solder and Ni layer resulted in the formation of two IMCs such as (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4 at the interface. The (Ni, Cu)3Sn4 IMCs were needle-like type, while the (Cu, Ni)6Sn5 IMCs were cylinders with a hexagonal cross-section and pointed tips. Compared to the quenched sample, the (Cu, Ni)6Sn5 IMCs nucleated heterogeneously on the (Ni, Cu)3Sn4 layer during the solidification of the solder. In the ball shear test, the shear strength value did not change much as a function of reflow time. In all samples, the fracture occurred in the bulk solder. The results of interfacial reaction and shear test in this study show that the Sn–Ag–Cu/Ni BGA solder joint has a desirable joint reliability.

The interfacial reactions and growth kinetics of intermetallic compound (IMC) layers formed between Sn–0.7Cu (wt.%) solder and Au/Ni/Cu substrate were investigated at aging temperatures between 70 and 170 °C for up to 100 days. After reflow, the IMC formed at the interface was (Cu,Ni)6Sn5. In addition, only this (Cu,Ni)6Sn5 layer was observed in the samples aged at temperatures between 70 and 150 °C. On the other hand, after isothermal aging at 170 °C for 50 days, the solder/Ni interface exhibited a duplex structure of (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. The time exponents (n) determined at temperatures below 150 °C were about 0.2. The determined n values are presumably related to a grain boundary diffusion-controlled mechanism. In the ball-shear tests, the shear strength significantly decreased after aging for initial 1 day, after which it remained nearly unchanged through further prolonged aging. In all samples, fracture occurred in the bulk solder.

The interfacial reactions and joint reliabilities between Sn-9 mass%Zn solder and an electroless nickel-immersion gold (ENIG) plated Cu substrate were investigated during reflow and isothermal aging at temperatures between 343 and 423 K for aging times of up to 2400h. After reflowing and aging, the intermetallic compound (IMC) formed at the interface was found to be AuZn 3 . No Ni-containing reaction products, such as Ni-Zn, Ni-Sn and Ni 3 P, were observed to form at the interface. The interfacial microstructure and shear strength remained nearly unchanged, irrespective of the reflow time, and the fractures occurred in the solder matrix. In the ball shear tests conducted after aging treatment, the shear strength of the samples decreased during the initial 100h of aging and then remained constant with prolonged aging. The interfacial reaction between the Sn-Zn solder and the Ni-P plating layer was found to be suppressed by the formation of a layer-type Au-Zn IMC layer, resulting in the desirable interfacial reaction. Compared to the fast interfacial reaction between the Sn-9Zn solder and Cu substrate, the Sn-9Zn/ ENIG solder joint was considered to have a superior joint reliability.

The interfacial reaction and shear strength between the eutectic Sn–0.7 wt.% Cu solder and two different kinds of ball grid array (BGA) substrates (Cu and Au/Ni–P/Cu) during reflow at 255 °C for up to 30 min were studied. With the solder joints between the Sn–0.7Cu solder and Cu substrates, a Cu 6 Sn 5 intermetallic compound (IMC) was formed at the interface. In the case of the electroless Ni–P substrate, the IMC formed at the interface was mainly (Cu, Ni) 6 Sn 5 . Also, a P-rich Ni (Ni 3 P) layer was observed as a by-product of the Cu–Ni–Sn reaction. The Ni 3 P layer was between the (Cu, Ni) 6 Sn 5 IMC and the electroless Ni–P layer. The thickness of the Cu 6 Sn 5 , (Cu, Ni) 6 Sn 5 and Ni 3 P layer was found to increase with the reaction time. The growth of the Cu 6 Sn 5 IMC layer for Cu substrate was faster than that of the (Cu, Ni) 6 Sn 5 IMC layer for electroless Ni–P substrate. The Ni content in the (Cu, Ni) 6 Sn 5 IMC layer formed at the interface increased with increasing reaction time. In the ball shear tests, the shear strength value did not change much as a function of reflow time. In all samples, the fracture mainly occurred in the bulk solder. However, for the Sn–0.7Cu/electroless Ni–P joint reflowed for 10 min, the fracture occurred in ductile and slightly brittle mode.

The interfacial reactions between two Sn-Cu (Sn-0.7Cu and Sn-3Cu, wt.%) ball-grid-array (BGA) solders and the Au/Ni/Cu substrate by solid-state isothermal aging were examined at temperatures between 70°C and 170°C for 0 to 100 days. For the Sn-0.7Cu solder, a (Cu,Ni)6Sn5 layer was observed in the samples aged at 70–150°C. After isothermal aging at 170°C for 50 days, the solder/Ni interface exhibited a duplex structure of (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. For the Sn-3Cu solder, only the (Cu,Ni)6Sn5 layer was formed in all aged samples. Compared to these two Sn-Cu solders, the Cu content in the (Cu,Ni)6Sn5 layer formed at the interface increased with the Cu concentration in the Sn-xCu solders. And, the shear strength was measured to evaluate the effect of the interfacial reactions on the mechanical reliability as a function of aging conditions. The shear strength significantly decreased after aging for 1 day and then remained nearly unchanged by further prolonged aging. In all the samples, the fracture always occurred in the bulk solder. Also, we studied the electrical property of Cu/Sn-3Cu/Cu BGA packages with the number of reflows. The electrical resistivity increased with the number of reflows because of an increase of intermetallic compound (IMC) thickness.

The morphological and compositional evolutions of intermetallic compounds (IMCs) formed at three Pb-free solder/electroless Ni-P interface were investigated with respect to the solder compositions and reflow times. The three Pb-free solder alloys were Sn3.5Ag, Sn3.5Ag0.75Cu, and Sn3Ag6Bi2In (in wt.%). After reflow reaction, three distinctive layers, Ni3Sn4 (or Ni-Cu-Sn for Sn3.5Ag0.75Cu solder), NiSnP, and Ni3P, were formed on the electroless Ni-P layer in all the solder alloys. For the Sn3.5Ag0.75Cu solder, with increasing reflow time, the interfacial intermetallics switched from (Cu,Ni)6Sn5 to (Cu,Ni)6Sn5+(Ni,Cu)3Sn4, and then to (Ni,Cu)3Sn4 IMCs. The degree of IMC spalling for the Sn3.5Ag0.75Cu solder joint was more than that of other solders. In the cases of the Sn3.5Ag and Sn3Ag6Bi2In solder joints, the growth rate of the Ni3P layer was similar because these two type solder joints had a similar interfacial reaction. On the other hand, for the Sn3.5Ag0.75Cu solder, the thickness of the Ni3P and Ni-Sn-P layers depended on the degree of IMC spalling. Also, the shear strength showed various characteristics depending on the solder alloys and reflow times. The fractures mainly occurred at the interfaces of Ni3Sn4/Ni-Sn-P and solder/Ni3Sn4.

Intermetallic compound (IMC) growth during solid-state isothermal aging at temperatures between 100 and 200°C up to 60 days for Sn-3.5Ag-0.75Cu solder on Cu substrate was investigated. A quantitative analysis of the IMC layer thickness as a function of aging time and temperature was performed. Diffusion couples showed a composite IMC layer comprised of Cu6Sn5 and Cu3Sn. After isothermal aging at temperature over 120°C, the solder/Cu interface exhibited a duplex structure of Cu6Sn5 and Cu3Sn intermetallics. The growth of IMCs followed diffusion-controlled kinetics and the layer thickness reached 13 μm after 60 day of aging at 170°C. The apparent activation energies calculated for the growth of the total IMC (Cu6Sn5 + Cu3Sn), Cu6Sn5 and Cu3Sn intermetallic are 62.6, 49.1 and 80.1 kJ/mol, respectively.

The growth kinetics of intermetallic compound (IMC) layers formed between Sn-3.5Ag-0.75Cu BGA (ball grid array) solder and electroless Ni-P/Cu substrate by solid state isothermal aging were examined at temperatures between 70 and 170°C for 0 to 100 days. In the solder joints between the solder ball and electroless Ni-P/Cu pads, the IMC layer was (Cu,Ni)6Sn5. Also, a P-rich Ni layer formed at the interface between (Cu,Ni)6Sn5 and original Ni-P deposit layer because of the phosphorous accumulation. These IMC layer thicknesses increased linearly with the square root of aging time and the growth was faster for higher aging temperatures. On the contrary, the shear strength decreased with the increasing temperature and time. The growth of IMC layer was mainly controlled by diffusion-controlled mechanism over the temperature range studied. The apparent activation energy calculated for the growth of the (Cu,Ni)6Sn5 IMC was 69.75 kJ/mol.

The growth kinetics of intermetallic compound (IMC) layers formed between Sn-3Ag-6Bi-2In ball-grid-array (BGA) solder and Au/Ni/ Cu substrate by solid-state isothermal aging were examined at temperatures between 343 and 443 K for 0 to 100 days. A quantitative analysis of the IMC layer thickness as a function of time and temperature was performed. The intermetallic layer exhibited a parabolic growth at the given temperature range. Because the values of the time exponent (n) are approximately 0.5, the layer growth of the IMC was primarily controlled by diffusion over the temperature range studied. The apparent activation energy value calculated for the Sn-Ag-Bi-In/Au/Ni/Cu BGA joint was 64.8 kJ/mol. Also, the reliability of the solder ball attachment was characterized by mechanical ball shear tests. The brittleness of the solder joints increased with increasing aging temperature and time, and the fracture occurred within the IMCs and Ni layer. The deterioration of the solder ball shear strength was found to be predominantly caused by the formation of the IMC layer.

Growth kinetics of intermetallic compound (IMC) layers formed between the Sn-3.5Ag-5Bi solder and the Cu and electroless Ni-P substrates were investigated at temperatures ranging from 70°C to 200°C for 0–60 days. With the solder joints between the Sn-Ag-Bi solder and Cu substrates, the IMC layer consisted of two phases: the Cu6Sn5 (η phase) adjacent to the solder and the Cu3Sn (e phase) adjacent to the Cu substrate. In the case of the electroless Ni-P substrate, the IMC formed at the interface was mainly Ni3Sn4, and a P-rich Ni (Ni3P) layer was also observed as a by-product of the Ni-Sn reaction, which was between the Ni3Sn4 IMC and the electroless Ni-P deposit layer. With all the intermetallic layers, time exponent (n) was approximately 0.5, suggesting a diffusion-controlled mechanism over the temperature range studied. The interface between electroless Ni-P and Ni3P was planar, and the time exponent for the Ni3P layer growth was also 0.5. The Ni3P layer thickness reached about 2.5 µm after 60 days of aging at 170°C. The activation energies for the growth of the total Cu-Sn compound layer (Cu6Sn5 + Cu3Sn) and the Ni3Sn4 IMC were 88.6 kJ/mol and 52.85 kJ/mol, respectively.

The growth kinetics of intermetallic compound layers formed between Sn–5Bi solder and Cu substrate by solid state isothermal aging were examined at temperatures between 343 and 473 K for 0–30 days. In the solder joints between the Sn–5Bi solder and Cu substrate, the intermetallic compound layer was composed of two phases: Cu 6 Sn 5 (η-phase) adjacent to the solder and Cu 3 Sn (e-phase) adjacent to the copper. As a whole, because the values of the time exponent ( n ) are approximately 0.5, the layer growth of the intermetallic compound was mainly controlled by a diffusion-controlled mechanism over the temperature range studied. The intermetallic compound layer thickness reached 2.16 μm after 30 days of aging at 393 K. The apparent activation energies for growth of total Cu–Sn (Cu 6 Sn 5 +Cu 3 Sn), Cu 6 Sn 5 and Cu 3 Sn intermetallic compound layers were 107.1, 98.35 and 90.5 kJ/mol, respectively.

The growth kinetics of intermetallic compound layers formed between Sn–5Bi–3.5Ag solder and Cu substrate were investigated at temperatures between 70°C and 200°C for 0 to 60 days. A quantitative analysis of the intermetallic compound layer thickness as a function of time and temperature was performed. Diffusion couples showed a composite intermetallic layer comprised of Cu6Sn5 and Cu3Sn. The growth of intermetallic compounds followed diffusion controlled kinetics and the layer thickness reached only 10 μm after 60 days of aging at 150°C. The apparent activation energies calculated for the growth of the total intermetallic compound (Cu6Sn5 + Cu3Sn), Cu6Sn5 and Cu3Sn intermetallic are 88.6, 84.3 and 70.28 kJ mol-1, respectively.

The growth kinetics of intermetallic compound layers formed between Sn–3Ag–8Bi – 5In solder and (Cu, electroless Ni – P/Cu) substrate were investigated at temperatures between 70 and 170 °C for 1 to 60 days. The layer growth of the intermetallic compounds in the Sn–Ag– Bi – In/Cu and Sn–Ag –Bi – In/electroless Ni –P systems satisfied the parabolic time law. As a whole, because the values of time exponent have approximately 0.5, the layer growth is mainly controlled by diffusion. The apparent activation energies for the growth of the Cu6Sn5 and Ni3Sn4 intermetallic compounds are 81.4 and 67.1 kJ/mol, respectively.

The growth kinetics of intermetallic compound layers formed between Sn-3.5Ag solder and Cu substrate were investigated as a consequence of solid-state isothermal aging. Isothermal aging was carried out in a temperature range between 70°C and 200°C for 0 to 60 days. A quantitative analysis of the intermetallic compound layer thickness as a function of time and temperature was performed. The diffusion couples showed a composite intermetallic layer comprised of Cu6Sn5 and Cu3Sn. The growth of intermetallic compounds followed diffusion-controlled kinetics and the layer thickness reached only 9 μm after 60 day of aging at 150°C. The apparent activation energies were calculated for the growth of the total intermetallic compound (Cu6Sn5+Cu3Sn); Cu6Sn5 and Cu3Sn intermetallic are 65.4, 55.4 and 75.7 kJ/mol, respectively.

The reaction diffusion between indium solder and Au deposited (Ni and Cu) substrates was investigated. For the identification of intermetallic compounds, both Scanning Electron Microscopy (SEM) and X-Ray Diffractometry (XRD) were employed. Experimental results showed that the intermetallic compounds, such as Cu11In9 and In27Ni10, were observed for different substrates, respectively. Additionally, the growth rate of these intermetallic compounds was increased with the reaction temperature and time. We found that the growth of the intermetallic compound followsthe parabolic law, which indicatesthat layer growth of the intermetallic compound wasmainly controlled by volume diffusion over the temperature range. The apparent activation energies for intermetallic compound growth were 37.06 kJ/mol for Cu11In9 and 86.14 kJ/mol for In27Ni10, respectively.

The growth kinetics of intermetallic compound layers formed between eutectic Sn–58Bi solder and (Cu, electroless Ni–P/Cu) substrate were investigated at temperature between 70 and 120◦C for 1 to 60 days. The layer growth of intermetallic compound in the couple of the Sn–58Bi/Cu and Sn–58Bi/electroless Ni–P system satisfied the parabolic law at given temperature range. As a whole, because the values of time exponent (n) have approximately 0.5, the layer growth of the intermetallic compound was mainly controlled by diffusion mechanism over the temperature range studied. The apparent activation energies of Cu6Sn5 and Ni3Sn4 intermetallic compound in the couple of the Sn–58Bi/Cu and Sn–58Bi/electroless Ni–P were 127.9 and 81.6 kJ/mol, respectively.

In this study, the interfacial reactions of In–48Sn solder balls on an electroless Ni/immersion Au (ENIG) ball grid array (BGA) substrate during reflow at 170 °C for up to 1800 s were investigated using SEM, transmission electron microscope (TEM) and energy dispersive X-ray spectroscope (EDS) analyses. During the initial 10 s of the reflow process, AuIn2 cubes and a continuous Ni3(Sn,In)4 intermetallic compound (IMC) layer were formed at the interface between the solder and the substrate. The thickness of the Ni3(Sn,In)4 layer was found to increase from approximately 140 nm to 1 µm, as the reflow time increased from 10 to 1800 s, respectively. The transformation of Ni to form the Ni3(Sn,In)4 IMC led to the formation of a P-rich Ni (hereafter Ni3P) layer between the Ni3(Sn,In)4 IMC and the ENIG substrate, whose thickness increased with increasing the reflow time. Copyright © 2006 John Wiley & Sons, Ltd.

Growth kinetics of intermetallic compound (IMC) layers formed between Sn-3.5Ag solder and electroless Ni-P/Cu substrates were investigated at temperatures ranging from 100 to 170°C for 0 to 60 days. The IMC formed at the interface was mainly Ni 3 Sn 4 , and a P-rich Ni (hereafter Ni 3 P) layer was also observed as a by-product of Ni 3 Sn 4 formation, that was localized between the Ni 3 Sn 4 IMC and the electroless Ni-P deposit layer. This Ni 3 P layer formed because of the phosphorous accumulation at the interface between the electroless Ni and the IMC layer. It was found that both the Ni 3 Sn 4 1 IMC and the Ni 3 P layer were formed due to the solder reaction-assisted crystallization. Also, another layer with Ni-Sn-P was observed between the Ni 3 P layer and the Ni 3 Sn 4 IMC layer. The layer thickness of Ni 3 Sn 4 and Ni 3 P were approximately 1.83 and 1.56 μm after 50 days of ageing at 150 °C, respectively.

A novel packaging method for high power modules based on one-step sintering process using a proper jig and nano silver paste is described. First, using Ansoft Q3D Extractor, electromagnetic simulation is carried out to design the best chip array and DC bus connection, which giving the lowest stray inductance. A die-bonder is used for a precise die attachment, which provides high placement accuracy (< 25 µm). One step sintering process between Si chip to DBC and DBC to baseplate was established under a low temperature (< 260 °C) and low pressure (< 10 MPa). In addition, the relation of the porosity and pressure on the adhesion of sintered silver layers was investigated. Finally, thermal performance of the proposed package and cooling is then evaluated with both FEA (finite element analysis) simulation and experiments. The simulation and experimental results, which show the lowest value (

In this study, the electrochemical performance of an electroless nickel/immersion gold (ENIG) surface finish was evaluated as a function of the Au immersion time by the water immersion migration test. As the Au plating time increased, the electroless nickel phosphorous (EN-P) changed from amorphous to crystalline and then increased in crystallinity. X-ray diffraction (XRD) was used to evaluate the crystallinity of the plating layer. The electrical resistance of the electrodes was tracked as the sample was immersed in water with a 5 V bias. The microstructures of the electrodes after the electrochemical migration test were observed by using secondary electron microscopy (SEM) and energy dispersive spectroscopy (EDS). As the Au immersion time increased, the EN-P's crystallinity and Au thickness increased. This enhanced the electrochemical migration protection of the surface finish layer.

In this study, the electrodes on the flexible printed circuit board (FPCB) and rigid PCB (RPCB) were bonded by a thermo-compression bonding. The surface finishes on Cu electrodes of RPCB and FPCB were electroless Ni/immersion Au (ENIG) and electroless Ni/electroless Pd/Immersion Au (ENEPIG), respectively. In order to determine the optimum bonding conditions, a 90° peel test of the FPCB-RPCB joint was conducted. The optimum bonding pressure and time were 2.04 MPa and 5 s at 260°C, respectively. Thin and uniform (Ni,Cu) 3 Sn 4 intermetallic compound (IMC) layers formed at both ENEPIG(FPCB)/Sn-3.0Ag-0.5Cu/ENIG(RPCB) interfaces. We successfully accomplished the thermo-compression bonding for a reliable FPCB-RPCB connection by using a Pb-free Sn-3.0Ag-0.5Cu interlayer.

Background: A correlation between a T-type voltage activated calcium channel (VACC) and pain mechanism has not yet been established. The purpose of this study is to find out the effect of ethosuximide and mibefradil, representative selective T-type VACC blockers on postoperative pain using an incisional pain model of rats. Methods: After performing a plantar incision, rats were stabilized on pl astic mesh for 2 hours. Then, the rats were injected with ethosuximide or mibefradil, intraperitoneally and intrathecally. The level of withdrawal threshold to the von Frey filament near the incision site was determined and the dose response curves were obtained. Results: After an intraperitoneal ethosuximide or mibefradil injection, the dose-response curve showed a dose-dependent increase of the threshold in a withdrawal reaction. After an intrathecal injection of ethosuximide, the threshold of a withdrawal reaction to mechanical stimulation increased and the increase was dose-dependent. After an intrathecal injection of mibefradil, no change occurre d in either the threshold of a withdrawal reaction to mechanical stimulation or a dose-response curve. Conclusions: The T-type VACC blockers in a rat model of postoperative pain showed the antihyperalgesic effect. This effect might be due to blockade of T-type VACC, which was distributed in the peripheral nociceptors or at the supraspinal level. Further studies of the effect of T-type VACC on a pain transmission mechanism at the spinal cord level would be needed. (Korean J Pain 2007; 20: 92�� 99)

We studied the influence of a thin GaAs insertion layer (5–10 monolayers) on the optical properties of InAs QDs grown by metalorganic chemical vapor deposition. The insertion of a 10 monolayer (ML) thick GaAs layer on the InAs QDs led to significant photoluminescence blueshifts of 54 and 111meV when they were grown on InGaAs and InP, respectively. In addition, a narrowing of full width at half maximum was observed when the thicker GaAs insertion layers and higher overgrowth temperature for the top capping layer were used. These results can be applied for tuning the emission wavelength around 1.55μm for optical fiber communication.