High Temperature Storage Test Research Articles

Pressure-less AgNP Sintering for High-power MCM Assembly for Extreme Environment Applications

Silver nano-particle (AgNP) sintering has been a promising bonding material for high-temperature applications. There is an increasing demand for designs implemented as multi-chip module (MCM) in the high-temperature markets, like the oil and gas industry, primarily because of MCM's smaller size, higher-performance capability, and higher overall reliability when compared to traditional high Tg printed circuit boards. In this work, pressure-less AgNP sintering paste was used in the assembly of multi-chip modules. The assemblies included die-mounted on aluminum nitride and alumina substrates that were metallized with various thin and thick films. Sintered silver nano-particle attachments were also attempted for surface-mounted technology (SMT) chip components. Different assembly parameters such as bonding line thickness and sintering profiles were evaluated to discover the optimal assembly process window that would yield acceptable reliability for 250°C and higher ambient temperature applications. The assemblies were subjected to various tests including thermal cycling, high-ramp rate thermal shocks, and high-temperature storage tests. Shear strength measurements and analysis of the cross sections and fracture surfaces were performed to understand failure mechanisms. One of the findings was a certain and unique failure mode associated with bonding of thin-film gold metallized surfaces using pressure-less silver nano-particles sintering. That failure mode begins after a short exposure to temperatures of 200°C and higher. However, silver nano-particle sintering on substrates metallized with thin-film silver and some thick-film formulations yields dramatically better results.

Low Temperature, Fast Sintering of Micro-Scale Silver Paste for Die Attach for 300°C Applications

With an increasing demand for SiC and GaN high power devices that operate at high temperature, traditional solder materials are reaching their limitations in performance. In addition, there is a strong desire to eliminate high lead containing solders in Si power device packaging for use over conventional temperature range. Low temperature Ag sintering technology is a promising method for high performance lead-free die attachment. In a previous study, a pressureless sintering process and suitable metallization were demonstrated to provide high reliability die attach by using micro-size Ag sintering. The resulting die attach layer had approximately 30% porosity. In this work, a low temperature pressure-assisted fast sintering process was examined. The porosity was decreased from 30% to 15% with application of a low pressure (7.6MPa) during a one minute sintering process. The shear strength for a 3 mm × 3 mm die was 70 MPa and the 8 mm × 8 mm die could not be sheared off due to a 100 kg shear module force limit. Both the Ag and Au metallization (die and substrate) were studied. Furthermore, a new substrate metallization combination was found that allows the use of Au thick film metallized substrates. High temperature (300 °C) storage tests for up to 2000 hours aging were conducted and results are presented.

Microstructural Characterization and Mechanical Performance of Wafer-Level SLID Bonded Au-Sn and Cu-Sn Seal Rings for MEMS Encapsulation

Special applications, such as microelectromechanical systems (MEMS), often require hermetic sealing in order to achieve a desired operation. Solid–liquid interdiffusion (SLID) bonding is an attractive method for encapsulating MEMS devices at the wafer-level, providing, e.g., high re-melt temperatures and tolerance for topographical variations. Several different SLID bond solutions have been investigated; however, there are only a limited number of published reliability studies available. In this paper, wafer-level Au-Sn and Cu-Sn SLID seal rings were mechanically characterized with shear and tensile tests. The evolution of bond microstructures and consequent effects on mechanical reliability were evaluated with a mixed flow gas test, a high temperature storage test and a thermal shock (TS) test. Virgin samples showed high mechanical strength. The Au-Sn system, with a thin Ni layer between the TiW adhesion layer and the bond, demonstrated a shear strength of 170 MPa. Cu-Sn, with a Cu-Cu3Sn-Cu structure, exhibited a shear strength of 275 MPa. Statistically significant decreases in strength were identified after reliability tests. The shear strength of the Au-Sn bond with an (AuSn + Au5Sn)eut structure decreased 40% in a corrosive environment. After 3000 TS cycles, the tensile strength of the Cu-Sn bond reduced by 45%. Fracture surface analysis revealed through-bond failures that were not observed previously. In cross-sectional analysis, vertical cracks were observed, which may contribute to the decrease in tensile strength.

Surface Tailored Acetylene Black for High Voltage Lib Application

(Introduction) In recent years, high voltage Lithium-ion secondary batteries (LiB) has been attractive energy storage system especially for electric vehicles due to its high energy density compared to commercialized LiB.In high voltage LiB system, although there are still a lot of obstacles for practical use, most serious problem is that gas generation during charging. [1] This gas generation is induced from decomposition of electrolyte on the surface of composed materials such as positive electrode active materials, binder, and also conductive additive, as we call it conductive agent which could improve cell performance as well as other components do. The decomposition of electrolyte on the surface of conductive agent is tend to depend on its specific surface area (SSA). Furthermore, surface functional groups, crystalline and crystal defects of conductive agent could related to the decomposition of electrolyte in previous research by X-ray Photoelectron Spectroscopy, Raman and Electron Spin Resonance (ESR) [2,3]. Therefore, the surface condition of conductive agent is important to suppress the gas generation for high voltage LiB application. In this research, we modified the surface of conductive agent to reduce surface functional groups or defects that are the factors related to decomposition of electrolyte. Then we evaluated the amount of generated gas and cell performances of the electrode consisted of surface tailored conductive agent at high voltage. (Experimental & Results) Acetylene Black (AB) was prepared as conductive agent (Particle size: 48 nm and SSA: 39 m2/g) and Tailored-AB, which is coated AB with inactive chemical materials such as SiO2 by sol-gel method [4,5]. The fundamental electrochemical performance was evaluated with simple half cell (2032type coin cell) by cyclic voltammetry (CV), and the amount of generated gas at high voltage (about 5.0 V) was evaluated with pouch cell by high-temperature storage test. The electrodes for electrochemical performance were made from AB and PVdF and the mass ratio was set to AB:PVdF=1:1.The electrode for high-temperature storage test was made from LiNi0.5Mn1.5O4 (NMS), AB and PVdF and the mass ratio was set to NMS:AB:PVdF= 90:5:5. This fabricated positive electrode and negative electrode which is mainly composed of natural graphite were paired in a pouch cell. At all test, 1 mol / dm3 LiPF6 in ECFDEC1F2 [vol %] was selected as electrolyte. The amount of generated gas was evaluated by measurement of cell volume after storage for 72 hours at 60oC under full charged state. Crystal defects were measured by Electron Spin Resonance (ESR). Crystal defects detected by ESR are assigned as conductive electron spin (CES) and localized electron spin (LES). LES are corresponding to crystal defects on the surface of AB, because almost all spins of carbon are present on the surface of carbon blacks [6,7,8]. Figure shows SEM images (BSE, Back Scattered Electron) of (a)pristine AB and (b)Tailored-AB. In this figure, the contrast of SiO2 was brighter than that of carbon. It was found that Tailored-AB was partially coated by SiO2. According to our results, Tailored-AB could have much potential to suppress the decomposition of electrolyte and gas generation compared with pristine AB. The results of ESR measurement which is a representative index of defects might indicate that defects of Tailored-AB decreased by chemical modification. In this presentation, further discussions about more detail results, other chemical modification and the analysis method will be presented (Reference) (1) H. Wang, et al., Anal. Chem., 86, 6197, (2014). (2) M. Nishikawa, et al., 55th battery discussion, 2B04, (2014). (3) T. Sonoda, et al., 41st carbon material Society, 1A08, (2014). (4) W. L. Zhang, et al., American Chemical Society, 28, 7055, (2012). (5) T. Sonoda, et al.,7th Lithium Battery Discussions, to be presented at the end of June in 2015 (6) S. Morozowski, et al., Carbon, 9, 97 (1971). (7) S. Ishii, et al., Physica E, 19, 149 (2003). (8) K. Fujimoto, et al., J. S. Rubber Industry, 46, 3 (1973). Figure 1

Development of chip-on-flex bonding using Sn-based bumps and non-conductive adhesive

We developed a reliable and low cost chip-on-flex (COF) bonding technique using Sn-based bumps and a non-conductive adhesive (NCA). Two types of bump materials were used for the bonding process: Sn bumps and Sn–Ag bumps. The bonding process was performed at 180°C for 10s using a thermo-compression bonder after dispensing the NCA. Sn-based bumps were easily deformed to contact Cu pads during the bonding process. A thin layer of Cu6Sn5 intermetallic compound was observed at the interface between Sn-based bumps and Cu pads. After bonding, electrical measurements showed that all COF joints had very low contact resistance, and there were no failed joints. To evaluate the reliability of COF joints, high temperature storage tests (150°C, 1000h), thermal cycling tests (−25°C/+125°C, 1000 cycles) and temperature and humidity tests (85°C/85% RH, 1000h) were performed. Although contact resistance was slightly increased after the reliability test, all COF joints passed failure criteria. Therefore, the metallurgical bond resulted in good contact and improved the reliability of the joints.

Solid-State Interfacial Reaction between Eutectic Au−Ge Solder and Cu/Ni(P)/Au Metalized Ceramic Substrate and Its Suppression

Eutectic Au−12Ge solder was employed to bond the SiC power devices to a Si3N4/Cu/Ni(P)/Au multi-layered substrate. The high-temperature reliability of the bond was investigated in detail at 200, 250, 300 and 330 °C, respectively. NiGe and Ni5Ge3 intermetallic compounds (IMCs) were identified at the Au−12Ge/Ni(P) interface by micro X-ray diffraction (μXRD) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX). The growth of the Ni−Ge IMCs was dominated by Ni5Ge3 layer, which formed at the Ni5Ge3/NiGe interface by outward diffusion of Ni from the Ni(P) layer. The activation energy of the total Ni−Ge IMCs growth was 66 kJ/mol. The shear strength of the bond was tested at both 25 °C and the aging temperatures, respectively. The shear strength decreased slightly after aging at 200 and 250 °C. The shear strength tested at 250 °C was 46 MPa after aging at 250 °C for 3000 h. The shear strength aged at 300 and 330 °C rapidly decreased with aging time due to the rapid growth of the Ni5Ge3 IMC. To slow down the interfacial reaction between the high temperature solder and the Ni(P) layer, an approximately 200 nm-thick Ta/TaN/Ta new diffusion barrier (DB) was deposited on the substrate. Analysis by transmission electron microscopy (TEM) equipped with EDX, reveals that the Ta/TaN/Ta DB was bonded well to the Ni(P) layer and the solder. High temperature storage test at 330 °C for 1500 h reveals that the bond of the SiC devices maintained its high shear strength of approximately 56 MPa without decrease. The new DB effectively suppressed the interfacial reaction between the Au−12Ge solder and the Ni(P) layer of the substrate.

Effect of the Silver Content of SnAgCu Solder on the Interfacial Reaction and on the Reliability of Angle Joints Fabricated by Laser-Jet Soldering

The silver content of lead-free solders affects their microstructure, the interfacial reaction, and the performance of the joints in reliability tests. In this study, Sn3.0Ag0.5Cu (wt.%, SAC305) and Sn1.0Ag0.5Cu (wt.%, SAC105) solder balls of diameter 55 μm were reflowed on gold surface pads by laser-jet soldering. It was found that four types of layered intermetallic compound (IMC) were formed at the interfaces; these were Au5Sn/AuSn, AuSn, AuSn2, and AuSn4 from the pad side to the solder matrix. The Au5Sn/AuSn eutectic region, thickness 400 nm, formed because of the high cooling rate induced by the laser-jet soldering. During high-temperature storage tests, the silver became segregated at the interfaces between the Au–Sn IMC and the solder matrix, resulting in inhibition of IMC growth in SAC305 joints, the shear strengths of which were higher than those of SAC105 joints. In mechanical drop tests, however, percentage failure of the SAC305 joints was twice that of the SAC105 joints.

Comprehensive transmission electron microscopy study on Cu–Al intermetallic compound formation at wire bond interface

Abstract

Ultra-fine pitch palladium-coated copper wire bonding: Effect of bonding parameters

Copper (Cu) wire bonding has become a mainstream IC assembly solution due to its significant cost savings over gold wire. However, concerns on corrosion susceptibility and package reliability have driven the industry to develop alternative materials. In recent years, palladium-coated copper (PdCu) wire has become widely used as it is believed to improve reliability. In this paper, we experimented with 0.6ml PdCu and bare Cu wires. Palladium distribution and grain structure of the PdCu Free Air Ball (FAB) were investigated. It was observed that Electronic Flame Off (EFO) current and the cover gas type have a significant effect on palladium distribution in the FAB. The FAB hardness was measured and correlated to palladium distribution and grain structure. First bond process responses were characterized. The impact of palladium on wire bondability and wire bond intermetallic using a high temperature storage test was studied.

Effects of silver addition on Cu–Sn microjoints for chip-stacking applications

The solid-state reactions under confined space between Cu substrate and Sn and Sn–Ag solders are systematically investigated, with the objective of providing fundamental data that are critical to the design of robust microjoints for chip-stacking applications. Sandwich structures of Cu/Sn/Cu and Cu/Sn3.5Ag/Cu are prepared by thermal compression bonding. The thickness of Sn and Sn3.5Ag layer is controlled at 10μm. High temperature storage tests are conducted at 120°C, 150°C, 180°C, and 200°C for different time periods. Unlike the well-known void formation in the Ni/Sn/Ni system, there is no such void at all in the Cu/Sn/Cu system. The addition of Ag consistently slows down the growth kinetics of intermetallics. The time-to-impingement of intermetallics is established for the first time for both systems under solid-state reactions.

Reliability of Cu to Cu Joints Fabricated Using SnAg Capping Layer for 3D TSV Applications

Chip to Chip bonding technology using Cu bumps with solder capping layer has been widely investigated for 3D chip stacking applications. We studied the reliability of the Cu joints. Cu bumps capped with Sn-Ag solder layer were joined to bare Cu pads or Au/Ni electroplated Cu pads at 300°C for 10 sec after dispensing non-conductive paste (NCP). After joining, there were no failed joints and the contact resistance of the joints was very low in all specimens. High temperature storage (HTS) test (120°C, up to 2000 hrs) results demonstrated that the reliability was good in all specimens, while thermal cycling test (-55°C /+125°C, up to 2500 cycles) results showed that the contact resistance of the joints increased quickly after 2000 cycles which was attributed the crack formation in the joint interfaces.

Characterization of AgBiX™ Solder Paste on Thick Film for 200°C Applications

AgBiX™ (Indium Corporation) solder paste has a solidus temperature of ∼262°C after reflow, which is suitable for passive component, semiconductor and power die attach for 200°C applications. In this work, the paste has been used to assemble SiC die with Ti/Ni/Ag thin film metallization to Ag and PdAg thick film substrates. High temperature storage testing (200°C) was preformed to characterize the reliability of the assemblies. Surface mount chip resistors attached to thick film substrates were also subject to high temperature storage. Comparisons of the performance of die attach and resistor attach on Ag substrates and PdAg substrates are made. EDX and failure analysis was used to understand the role of Pd on the failure mode and lower aged shear strengths with the thick film PdAg conductors.

Characterization of Reliability of Printed Indium Tin Oxide Thin Films

Recently, decreasing the amount of indium (In) element in the indium tin oxide (ITO) used for transparent conductive oxide (TCO) thin film has become necessary for cost reduction. One possible approach to this problem is using printed ITO thin film instead of sputtered. Previous studies showed potential for printed ITO thin films as the TCO layer. However, nothing has been reported on the reliability of printed ITO thin films. Therefore, in this study, the reliability of printed ITO thin films was characterized. ITO nanoparticle ink was fabricated and printed onto a glass substrate followed by heating at 400 degrees C. After measurement of the initial values of sheet resistance and optical transmittance of the printed ITO thin films, their reliabilities were characterized with an isothermal-isohumidity test for 500 hours at 85 degrees C and 85% RH, a thermal shock test for 1,000 cycles between 125 degrees C and -40 degrees C, and a high temperature storage test for 500 hours at 125 degrees C. The same properties were investigated after the tests. Printed ITO thin films showed stable properties despite extremely thermal and humid conditions. Sheet resistances of the printed ITO thin films changed slightly from 435 omega/square to 735 omega/square 507 omega/square and 442 omega/square after the tests, respectively. Optical transmittances of the printed ITO thin films were slightly changed from 84.74% to 81.86%, 88.03% and 88.26% after the tests, respectively. These test results suggest the stability of printed ITO thin film despite extreme environments.

Bendable 임베디드 전자모듈의 손상 메커니즘

A bendable electronic module has been developed for a mobile application by using a low-cost roll-to-roll manufacturing process. In flexible embedded electronic module, a thin silicon chip was embedded in a polymer-based encapsulating adhesive between flexible copper clad polyimide layers. To confirm reliability and durability of prototype bendable module, the following tests were conducted: Moisture sensitivity level, thermal shock test, high temperature & high humidity storage test, and pressure cooker tester. Those experiments to induce failure of the module due to temperature variations and moisture are the experiment to verify the reliability. Failure criterion was 20% increase in bump resistance from the initial value. The mechanism of the increase of the bump resistance was analyzed by using non-destructive X-ray analysis and scanning acoustic microscopy. During the pressure cooker test (PCT), delamination occurred at the various interfaces of the bendable embedded modules. To investigate the failure mechanism, moisture diffusion analysis was conducted to the pressure cooker's test. The hygroscopic characteristics of the encapsulating polymeric materials were experimentally determined. Analysis results have shown moisture saturation process of flexible module under high temperature/high humidity and high atmosphere conditions. Based on these results, stress factor and failure mechanism/mode of bendable embedded electronic module were obtained.

Initial Success on Aluminum Circuit Board Technology

In this paper, aluminum circuit boards (ACBs) were designed, fabricated, and tested to demonstrate the possibility and advantages of the ACB technology. Processes were developed to grow high quality alumina <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$({\rm Al}_{2}{\rm O}_{3})$</tex></formula> on Al boards and coat thick copper (Cu) layer over the alumina to produce an Al/alumina/Cu structure. The measured resistance and breakdown voltage of the as-formed 50 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> alumina layer is <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${&gt;}{\rm 40}~{\rm M}\Omega$</tex></formula> and 600 VDC respectively. In this design, heat generated by a high power circuit component attached to the Cu layer can conduct through the alumina layer and reach the Al base. Alumina has much higher thermal conductivity than epoxy-glass insulating layer of the popular FR-4 printed circuit boards. The quality of the boards produced in this paper was evaluated rigorously using scanning electron microscope. To test the reliability of the boards, they were put through 500 cycles of thermal cycling test between <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${-}{40}^{\circ}{\rm C}$</tex></formula> to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${+}{85}^{\circ}{\rm C}$</tex></formula> and 100 h of high temperature storage test at 250 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> . To ensure its compatibility with soldering operations, 10 mm <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times\,$</tex></formula> 12 mm Cu substrates were bonded to the Al boards using a fluxless tin process. The thickness of the joint is 9.4 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> including the intermetallic layers. Despite significant coefficient of thermal expansion mismatch of the structure and large Cu size, the bonded samples show no sign of cracks, breakage, or degradation.

Long term storage reliability of antifuse field programmable gate arrays

Field Programmable Gate Arrays (FPGA) with antifuse elements are preferred in aerospace applications due to their non-volatility and demonstrated radiation hardness. Because aerospace applications typically involve long operating life, there is a requirement to store un-programmed antifuse FPGA parts for long periods and program them when necessary to support the system. No study on the long term reliability of un-programmed antifuse FPGAs in the storage environment is reported in literature. In this paper, antifuse structures, programming process, and failure mechanisms of antifuse FPGAs are discussed. A failure modes, mechanisms and effects (FMMEA) analysis was performed for storage conditions and critical failure mechanisms were identified. High temperature storage tests of a select number of antifuse FPGAs were performed to accelerate the identified failure mechanisms. These parts were subsequently programmed and yield data was analyzed to determine the effects of high temperature storage.

Joint reliability evaluation of thermo-compression bonded FPCB/RPCB joints under high temperature storage test

In this study, electrodes on a flexible printed circuit board (FPCB) and rigid printed circuit board (RPCB) were bonded by a thermo-compression bonding. Pb-free Sn–3.0Ag–0.5Cu solder was used as an interlayer. In order to determine the optimum bonding conditions for bonding pressure and time, a 90° peel test of the FPCB–RPCB joint was conducted. The relationships between the bonding conditions, interfacial reactions, and peel strength were investigated. The optimum bonding pressure and time were 2.04MPa and 5s at 260°C, respectively. Thin and uniform (Ni,Cu)3Sn4 intermetallic compound (IMC) layers formed at both FPCB/Sn–3.0Ag–0.5Cu/RPCB interfaces. In a high temperature storage (HTS) test of 125°C, the peel strength decreased as the aging time increased. After the HTS test, brittle interfaces formed in the PCB joints, resulting in the switching of the failure mode from a polyimide–electrode failure to a brittle IMC failure.

Molding Compounds Adhesion and Influence on Reliability of Plastic Packages for SiC-Based Power MOS Devices

Adhesion and interface compositions of epoxy phenolic molding compounds (EMCs) for high-temperature plastic packages are studied. Interfaces are obtained by molding two EMCs onto aluminum oxide-hydroxide surfaces (oxide onto thin film of AlSiCu) and two die passivation layers consisting of fluorinated polyimide and cyclotene. One compound (A) is a “green” type, containing organic phosphorous-based flame retardant, and the other compound (B) is a conventional type containing antimony (III) oxide and bromined resin flame retardants. A high-temperature storage test at 250 °C is employed to study chemical modifications occurring at the previously mentioned interfaces. A high-temperature reverse bias test at 225 °C is employed to study the influences of the EMC chemical formulations on the reliability of plastic packages for SiC-based power MOS devices. Green compound A shows poor adhesion onto Al oxide and high adhesion strength onto both polymer passivations. The failure mechanism is mainly cohesive on the polymer passivations. The conventional compound B shows a high degree of delamination because of poor adhesion compared with the green compound. SiC-based power MOS devices assembled in plastic packages with compound A show better reliability under HTRB test at 225 °C compared with compound B.

Mechanical characterization of nickel plated copper heat spreaders with different catalytic activation surface treatment techniques

This paper studied the effects of different catalytic activation processes towards intermetallic diffusion and mechanical properties on nickel plated heat spreader after high temperature storage (HTS). Heat spreader performs as medium to dissipate heat from silicon die towards heat-sink and is normally made by copper that is plated with nickel to improve wear resistance and prevent oxidation of copper. Two types of heat spreader that using galvanic initiation and thin nickel-copper electrodeposition surface treatment technique had been studied on their hardness and moduli by using Micro Tester and Nano-indenter. Besides, HTS tests were performed to investigate intermetallic diffusion between the nickel and copper layers. Young’s moduli of the heat spreaders which were plated by galvanic initiation and thin nickel-copper strike electroless nickel plating catalytic activation techniques were 45 to 65 GPa and 60 to 80 GPa, respectively. The results found that thin nickel-copper electrodeposition technique gave a higher modulus for the heat spreader and this also increased the mechanical strength of heat spreader. Diffusion also took place with a very slow rate in nickel-copper layer. Key words: Heat spreader, electroless nickel plating, galvanic initiation, thin nickel-copper electrodeposition, high temperature storage.

Palladium-Coated and Bare Copper Wire Study for Ultra-Fine Pitch Wire Bonding

There is growing interest in copper (Cu) wire bonding due to its significant cost savings over gold wire. However, concerns on corrosion susceptibility and package reliability have driven the industry to develop alternative materials. Recently, palladium-coated copper (PdCu) wire has become widely used as it is believed to improve reliability. In this paper, we experimented with 0.6 mil PdCu and bare Cu wires. Palladium distribution and grain structure of the PdCu Free Air Ball (FAB) were investigated. It was observed that Electronic Flame Off (EFO) current and the cover gas type have a significant effect on palladium distribution. The Free Air Ball (FAB) hardness was measured and correlated to palladium distribution and grain structure. First bond process responses were characterized. The impact of palladium on wire bondability and wire bond intermetallic using a high temperature storage test was studied. These results for PdCu wire were compared with bare Cu wire.