Z.W. Zhong, T.Y. Tee and J‐E. Luan
This paper seeks to review recent advances in wire bonding, flip chip and lead‐free solder for advanced microelectronics packaging.
Abstract
Purpose
This paper seeks to review recent advances in wire bonding, flip chip and lead‐free solder for advanced microelectronics packaging.
Design/methodology/approach
Of the 91 journal papers, 59 were published in 2005‐2007 and topics related to wire bonding, flip chip and lead‐free solder for advanced microelectronics packaging are reviewed.
Findings
Research on advanced wire bonding is continuously performed for advanced and complex applications such as stacked‐dies wire bonding, wire bonding of low‐k ultra‐fine‐pitch devices, and copper wire bonding. Owing to its many advantages, flip chip using adhesive has gained more popularity. Research on the reliability of lead‐free solder joints is being conducted world‐wide. The new challenges, solutions and new developments are discussed in this paper.
Research limitations/implications
Because of page limitation of this review paper and the large number of the journal papers available, only a brief review is conducted. Further reading is needed for more details.
Originality/value
This review paper attempts to provide introduction to recent developments and the trends in terms of the topics for advanced microelectronics packaging. With the references provided, readers may explore more deeply, focusing on a particular issue.
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Keywords
Fang Liu, Guang Meng and Junfeng Zhao
The purpose of this paper is to propose an alternative test board design with only one loading condition and sufficiently large sample size, which is more suitable for the…
Abstract
Purpose
The purpose of this paper is to propose an alternative test board design with only one loading condition and sufficiently large sample size, which is more suitable for the statistical package qualification. With the exception of the board shape and size and package component layout, all other aspects of the design strictly follow the JEDEC standard so that the board design can be easily implemented.
Design/methodology/approach
A test board in a round shape was introduced. First, drop tests were carried out. Then, the dye stain test and metallurgical analysis were performed in order to study the failure mechanism of lead‐free solder joint under drop impact.
Findings
The test results indicate that the combined effect of mechanical shock and PCB bending vibration is the root cause of solder joint failure under drop impact, and that the maximum peeling stress of the critical solder joint could be considered to be the dominant failure factor. On the other hand, the fracture of BGA lead‐free solder joints occurs at intermetallic compound (IMC) interface near the package side, and failure mode is brittle fracture.
Originality/value
These results are the same as those of JEDEC standard test board. Furthermore, the solder joint loading conditions in this design are simplified from six to one. The round test board can take the place of JEDEC standard test board to carry out drop test and to enable good solder joint life prediction and statistical analysis.
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Ping Zhu, Liang You Wang, Guang Ren Qian, Tie Hua Cao and Ming Zhou
The purpose of this paper is to investigate the electrodeposition of copper coatings directly onto AZ31 magnesium alloy, considered as a substrate of electroplating nickel. The…
Abstract
Purpose
The purpose of this paper is to investigate the electrodeposition of copper coatings directly onto AZ31 magnesium alloy, considered as a substrate of electroplating nickel. The additive, pH, complexing agent, current density, time, and temperature of electrolytic bath were studied to understand electrodepositing copper coating on AZ31 magnesium alloy.
Design/methodology/approach
Electrodeposition of copper was carried out in an aqueous solution containing copper hydroxide, citrate, and fluorine ion, which avoids the replacement or corrosion of the magnesium alloy. The morphology, structure, and interface of the electrodeposited copper coating were investigated by a scanning electron microscope (SEM).
Findings
The copper coating was dense, and there was good adhesion of the copper coating on the AZ31 magnesium alloy. This suggests that successful deposition of copper using an electroplating process could decrease the cost of coating AZ31 magnesium alloy.
Practical implications
This paper will be helpful for the development of coating on magnesium alloy using electroplating processes.
Originality/value
Copper hydroxide and citrate were the main compositions of the electrolyte, combined with sodium poly dipropyl (SP) and polyethylene glycol (PEG) as brightening agents and can be used to electrodeposit copper directly onto AZ31 magnesium alloy.
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Keywords
This paper attempts to review recent advances in wire bonding using copper wire.
Abstract
Purpose
This paper attempts to review recent advances in wire bonding using copper wire.
Design/methodology/approach
Dozens of journal and conference articles published recently are reviewed.
Findings
The problems/challenges such as wire open and short tail defects, poor bondability for stitch/wedge bonds, oxidation of Cu wire, strain‐hardening effects, and stiff wire on weak support structures are briefly analysed. The solutions to the problems and recent findings/developments in wire bonding using copper wire are discussed.
Research limitations/implications
Because of page limitation of the paper, only a brief review is conducted. Further reading is needed for more details.
Originality/value
This paper attempts to provide introduction to recent developments and the trends in wire bonding using copper wire. With the references provided, readers may explore more deeply by reading the original articles.
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Keywords
The purpose of this paper is to review recent advances in fine and ultra‐fine pitch wire bonding.
Abstract
Purpose
The purpose of this paper is to review recent advances in fine and ultra‐fine pitch wire bonding.
Design/methodology/approach
Dozens of journal and conference articles published recently are reviewed.
Findings
The problems/challenges such as possible wire sweep and decreased bonding strength due to small wire sizes, non‐sticking, metal pad peeling, narrow process windows, wire open and short tail defects are analysed. The solutions to the problems and recent findings/developments in fine and ultra‐fine pitch wire bonding are discussed.
Research limitations/implications
Because of the page limitation, only brief discussions are given in this paper. Further reading is needed for more details.
Originality/value
This paper attempts to provide an introduction to recent developments and the trends in fine and ultra‐fine pitch wire bonding. With the references provided, readers may explore more deeply by reading the original articles.
Details
Keywords
Fang Liu, Guang Meng and Mei Zhao
The purpose of this paper is to investigate the mechanism of ball grid array (BGA) lead‐free solder joint failure under board‐level drop impact.
Abstract
Purpose
The purpose of this paper is to investigate the mechanism of ball grid array (BGA) lead‐free solder joint failure under board‐level drop impact.
Design/methodology/approach
A round shaped test board was used. First, drop tests at three different heights were carried out. Then, dye stain testing and metallurgical analysis were performed in order to study the failure mechanism of lead‐free solder joints under drop impact.
Findings
The test results indicate that the combined effect of mechanical shock and printed circuit board bending vibration is the root cause of solder joint failure under drop impact. On the other hand, the fracture of BGA lead‐free solder joints occurs at the intermetallic compound interface near the package side, and the failure mode is brittle fracture.
Originality/value
These results are the same as those for JEDEC standard test boards. The round test board could take the place of the JEDEC standard test board when conducting drop testing.
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Keywords
Chang Dong, Jianlin Sun, Zixuan Cheng and Yuqing Hou
The purpose of this paper is to synthesize a microemulsion and investigate its tribological properties as lubricant. Magnesium alloy warm rolling experiments were conducted…
Abstract
Purpose
The purpose of this paper is to synthesize a microemulsion and investigate its tribological properties as lubricant. Magnesium alloy warm rolling experiments were conducted. Surface morphology was observed and wear form was summarized. The composition of surface residues was analyzed, which sheds light on the lubrication mechanism of microemulsion.
Design/methodology/approach
A microemulsion was prepared with a proper amount of oil, surfactant, cosurfactant, water and other additives for magnesium alloy strip warm rolling. Tribological properties, such as maximum non-seizure load (PB), friction coefficient (μ) and wear scar diameter (D) of the microemulsion were measured and compared with those of emulsion and rolling oil on an MR-10A four-ball tribotester. The extreme pressure anti-wear coefficients (O) were calculated and compared. Warm rolling experiments were carried out on a Ф 170/400 × 300 mm four-high rolling mill at 240°C to compare the finish rolling thickness and surface quality of rolled AZ31B magnesium alloy strip under four lubrication states, namely, no lubrication, rolling oil, microemulsion and emulsion. The surface morphology after warm rolling was observed with confocal laser scanning microscope and scanning electron microscope, respectively. The composition of surface residues was analyzed with energy dispersive spectrometry and X-Ray photoelectron spectroscopy.
Findings
Surface morphology indicated that pitting wear, adhesive wear and ploughing wear were three main forms of wear in magnesium alloy warm rolling. Microemulsion had excellent lubrication properties with less residual oil remaining. Two types of adsorption layers formed on magnesium alloy strip surface were responsible for lubrication properties. MgSO4 and magnesium stearate in the reaction layer played a key role in anti-wear and friction-reduction in warm rolling.
Originality/value
The study is original and gives valuable information on lubrication mechanism of microemulsion in warm rolling of magnesium alloy strips.
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Jian‐Rui Liu, Yi‐Na Guo and Wei‐Dong Huang
The purpose of this paper is to investigate a chromium‐free conversion coating treatment for magnesium with phytic acid solution.
Abstract
Purpose
The purpose of this paper is to investigate a chromium‐free conversion coating treatment for magnesium with phytic acid solution.
Design/methodology/approach
Pure magnesium was selected for the tests. Phytic acid solution was used as the conversion solution of surface treatment. The samples of magnesium were immersed in the solution under certain conditions to form a conversion coating on the surface of magnesium. The formation process of phytic acid conversion coating was studied by detecting the open circuit potential (OCP) and weight change of the pure magnesium for different conversion treatment times. Scanning electron microscopy (SEM) and electron energy spectrum (EDS) were used to examine the morphologies and compositions of the coatings, respectively.
Findings
The experimental results showed that the conversion coating had a multideck structure with netlike morphology, which is similar in nature to chromate conversion coatings, and was composed mainly of Mg, P, O and C. The contents of C and P and the size of the cracks in different conversion layers decreased from the external layer to the inner layer. The thickness of the conversion coating varied from 1.0μm to 15μm according to the processing parameters. The hydroxyl groups and phosphate carboxyl groups in the coating, which have similar properties to an organic paint coat, are beneficial to the combination of substrate and organic paint coating. The formation mechanism and thickness variation of the conversion coatings also are discussed.
Originality/value
The paper shows that phytic acid conversion coating could improve the electrochemical properties of magnesium and provide effective protection, which can improve the corrosion resistance of magnesium.
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Abstract
Purpose
The purpose of this paper is to investigate the effect of high-intensity pulsed ion beam (HIPIB) intensity on the structure and corrosive properties of microarc oxidation (MAO) films on AZ31 magnesium alloy and explore the mechanism for modified anti-corrosion properties of irradiated films.
Design/methodology/approach
The energy deposited on the coating surface influences the remelting process of the MAO coatings significantly, which was closely related to the intensity of HIPIB; therefore, HIPIB with various intensities of 100-350 A/cm2, was selected to modify the MAO films on AZ31 magnesium alloy. The changes in film structure and phase structure of modified films were characterized by scanning electron microscopy and X-ray diffractometry (XRD) with CuKα, respectively. The corrosive behavior of the MAO films was featured with polarization curves and electrochemical impedance spectrum in 3.5 per cent NaCl solution on a PAR 2273 electrochemical workstation.
Findings
The results clearly show that a dense, continual and remelted layer with a few micrometers in thickness was obtained on the irradiated surface at 200 A/cm2, which are mainly responsible for the modified and optimal anti-corrosion property of MAO films by suppressing/retarding the process of the corrosive electrolyte infiltration into magnesium substrate surface.
Originality/value
The paper reveals that HIPIB irradiation could modify the corrosion resistance by producing a remelted compact layer on the MAO film surface at a suitable irradiation parameter and explored the modified mechanism of MAO films.
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Juliána Drábiková, Stanislava Fintová, Jakub Tkacz, Pavel Doležal and Jaromír Wasserbauer
The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy.
Abstract
Purpose
The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy.
Design/methodology/approach
The chemical reaction of AZ61 with 38 wt.% hydrofluoric acid (HF) for 24 h was used as a conventional way of fluoride conversion coating preparation. The unconventionally prepared coating was created in Na[BF4] salt melt at 450°C for 2 h. Morphology and chemical composition of prepared fluoride conversion coatings were studied with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Electrochemical corrosion characteristics of the coatings were analyzed in Hank’s solution using potentiodynamic tests.
Findings
Both the coating preparation ways resulted in the creation of uniform conversion coatings with the same thickness (1.3 ± 0.1 μm). Some defects were observed on the coatings surface; however, the defects did not reach the AZ61 surface. Electrochemical tests performed in Hank’s solution at 37°C showed an improvement of corrosion resistance of AZ61 treated with fluoride conversion coatings when compared to the untreated material. Unconventionally prepared coating reached better electrochemical corrosion characteristics when compared to the conventionally prepared coating.
Originality/value
Electrochemical corrosion characteristics of AZ61 magnesium alloy can be improved with fluoride conversion coatings. Two methods are used in the literature for the coatings preparation. The conventional method is based on dipping of the coated material to the HF, and the unconventional method lies in dipping of the sample to the Na[BF4] salt melt. The main purpose of the present study is to analyze the conventionally and unconventionally prepared coatings in terms of chemical analysis, morphology and material corrosion protection (electrochemical corrosion characteristics), while the data are not provided in the literature, according to the authors’ knowledge. Very similar coatings were prepared using both the methods from the morphological and chemical composition point of view. However, unconventionally prepared coating created in Na[BF4] salt melt reached better electrochemical corrosion characteristics compared to the coating prepared in HF.