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Copper wire bonding has gained popularity due to its economic advantage and superior electrical performance. However, copper is harder than gold, and replacing gold wire with copper wire introduces hardness related issues. This article reports investigations of the properties including microhardness of the copper balls bonded using ?25.4-μm copper wire and different combinations of electronic-flame-off (EFO) current and firing time settings with forming gas (5%H2 and 95%N2) as the inert cover gas. FABs with an identical diameter, obtained under different EFO firing conditions, were ball bonded with the same wire bonding parameters established using design of experiments. Microhardness tests were then performed on the cross-section of the bonded balls. The study revealed that ultrasonic generator current is the most significant factor to increase the bonded mashed ball diameter, ball shear and shear per unit area and to decrease the ball height. The microhardness of bonded copper balls is related to the EFO parameters, with FABs obtained by higher EFO current being softer. The lower hardness is attributed to the higher maximum temperature during the FAB melting state. 相似文献
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《Microelectronics Reliability》2015,55(1):201-206
The currently high price of gold wire has led to the development of bonding wire made from palladium-coated-copper as a lower cost alternative. Increasing the uniformity of the Pd distribution in free-air balls, formed by melting the wire end with an electric spark, is of interest as it can influence the uniformity of process and reliability. To study this Pd distribution, free-air balls are made using four distinct electrical flame-off (spark) processes with short and long spark times from wire bonders with fixed and movable electrodes. Elemental analysis of the free-air ball surfaces reveal a higher Pd concentration on the movable electrode free-air balls than on the fixed electrode free-air balls. Elemental analysis of cross-sections show that the Pd distribution in free-air balls made with a fixed electrode has Pd trails flowing from the neck into the Cu ball center. Furthermore, micro- and nano-voids are observed to follow the Pd trails. In contrast, free-air balls made with a movable electrode exhibit less severe voiding and retain a uniform, thin Pd layer along the surface up to the tip of the free-air ball (shorter spark time). This can help to increase process consistency and reliability. 相似文献
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Copper wires are increasingly used in place of gold wires for making bonded interconnections in microelectronics. In this paper, a microstructural study is reported of cross-sectioned free air balls (FABs) made with 23 μm diameter copper bonding wire. It was found that the FAB is comprised of a few columnar grains and a large number of fine subgrains formed within the columnar grains around the periphery of the FAB. It was determined that conduction through the wire was the dominant heat loss mechanism during cooling, and the solidification process started from the wire-ball interface and proceeded across the diameter then outward towards the ball periphery.The microstructure of the Cu ball bond after thermosonic bonding was investigated. The result showed that the subgrain orientations were changed in the bonding process. It is evident that metal flow along the bonding interface was from the central area to the bond periphery during thermosonic bonding. 相似文献
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选取0.2032 mm (8 mil)金线采用热压超声键合工艺进行烧球、拉力和线尾等一系列正交试验,分析各个键合参数对键合质量的影响。研究结果表明,最优的引线键合工艺窗口为键合温度180℃或190℃、键合功率35 mW、键合时间15 ms或20 ms、键合压力0.12 N、烧球电流3200 mA、烧球时间350μs和尾丝长度20μm。在影响键合质量的各因素中,键合功率和键合压力对键合质量的影响显著,过大的键合功率会引起键合区被破坏,键合强度降低,过小的键合功率因能量不足会引起欠键合,键合强度降低。过大的键合压力会引起键合球变形而导致键合强度降低,过小的键合压力因欠键合而导致键合强度降低。 相似文献
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Two capillary solutions for ultra-fine-pitch wire bonding and insulated wire bonding 总被引:2,自引:0,他引:2
K.S. Goh 《Microelectronic Engineering》2007,84(2):362-367
In this article, the new challenges and requirements in wire bonding are discussed, the problems in ultra-fine-pitch wire bonding and insulated wire bonding are analyzed, and then two capillary solutions to the problems are presented. Actual bonding experiments using the new capillaries were carried out and the results were satisfactory. Compared to the standard design, a new capillary design has a larger inner chamfer, a larger chamfer diameter and a smaller chamfer angle. This new capillary design has proved to improve the ball bondability and smaller ball size control for ultra-fine pitch wire bonding. A unique surface characteristic on the capillary tip surface has also been derived. The new finishing process developed creates a new surface morphology, which has relatively deep lines with no fixed directions. Compared to the standard capillary, this capillary has less slipping between the wire and the capillary tip surface in contact, and provides better coupling effect between them and better ultrasonic energy transfer. This capillary has been used to effectively improve the bondability of the stitch bonds for insulated wire bonding. 相似文献
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The ultrasonic wire bonding (UWB) process has been examined using transmission electron microscopy (TEM) and standard wire
pull testing techniques. Al-0.5 wt.% Mg wires 75 μm in diameter were bonded to pure and alloyed Al substrates. The bonding
parameters, surface roughness, and surface contamination levels were variables in the experiments. Cross-section TEM specimens
were made from these samples. TEM analysis was conducted on the wire, wire/substrate interface and substrate. Pull tests showed
that for the Al substrates the surface roughness or the presence of contamination did not effect the bond strength, whereas
for contaminated stainless steel substrates, a three μm surface finish resulted in the highest bond pull strength. The TEM
observations revealed features such as low-angle grain boundaries, dislocation loops and the absence of a high dislocation
density, indicating that the wire and substrate were dynamically annealed during bonding. Based on the width of a zone near
a grain boundary in the wire which was depleted of dislocation loops, it was estimated that local heating equivalent to a
temperature of 250° C for 90 msec was achieved in the wire during bonding. No evidence was found for melting along the bond
interface, indicating that UWB is a solid-state process. Based on the TEM observationsof the bond interface and the pull tests, it is concluded that the ultrasonic vibrations clean the surfaces to be joined to
the extent that a good bond can be obtained by intimate metal-metal contact in the clean areas. 相似文献
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A promising way to control underpad chip damage in IC packaging caused by wire bonding forces would be to use new wire chemistries that produce softer free-air balls (FABs). The number of new wire types that can be tested is limited by the available resources. The conventional FAB hardness characterization method is the microindentation test, a labour intensive and off-line task requiring cross-sectioning of a large number of samples. To accelerate FAB hardness characterization, an innovative on-line method is studied and presented here, enabling the fast comparison of different wire types. Collection of data from an instrumented wire bonder allows comparison of the deformability, i.e. the average amount of FAB deformation under a defined load. Increased deformability implies a softer FAB. The influences have been studied of changes in capillary, bonding substrate metallization and substrate temperature on the results obtained. It is found that these influences need to be held constant during a comparison study. 相似文献
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Wire bonding is one of the main processes of the LED packaging which provides electrical interconnection between the LED chip and lead frame. The gold wire bonding process has been widely used in LED packaging industry currently. However, due to the high cost of gold wire, copper wire bonding is a good substitute for the gold wire bonding which can lead to significant cost saving. In this paper, the copper and gold wire bonding processes on the high power LED chip are compared and analyzed with finite element simulation. This modeling work may provide guidelines for the parameter optimization of copper wire bonding process on the high power LED packaging. 相似文献
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Wire bonding is one of the main processes of the LED packaging which provides electrical interconnection between the LED chip and lead frame.The gold wire bonding process has been widely used in LED packaging industry currently.However,due to the high cost of gold wire,copper wire bonding is a good substitute for the gold wire bonding which can lead to significant cost saving.In this paper,the copper and gold wire bonding processes on the high power LED chip are compared and analyzed with finite element simulation.This modeling work may provide guidelines for the parameter optimization of copper wire bonding process on the high power LED packaging. 相似文献
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This paper presents design, fabrication and evaluation of a wafer level MEMS (Micro Electro Mechanical System) encapsulation using an Au to Au direct bonding with wrinkle patterned layer. For the effective encapsulation, the optimal bonding condition, the bonding temperature 350 °C, the bonding pressure 58 MPa and the duration time 30 min, was developed and used in this paper. We briefly evaluated the bonding strength of test wafers after the bonding test. For RF (Radio Frequency) device packaging, we effectively interconnected Au CPW (Coplanar Waveguide) lines to feedthroughs and measured the RF characteristics. Measured insertion loss of the packaged CPW line was −0.11 dB at 2 GHz. The glass wafer having patterned Au sealing lines was also bonded and has been dipped in the acetone solution for 24 h to examine the leakage of bonding wafer. After 24 h dipping, any leakage point has not been observed at the sealing line and inside the cavity. These results showed that our Au to Au direct bonding method is very reliable and suitable for RF device packaging. 相似文献
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《Microelectronics Reliability》2014,54(11):2555-2563
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 0.6 ml 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. 相似文献
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Development of a thermosonic wire-bonding process for gold wire bonding to copper pads using argon shielding 总被引:2,自引:0,他引:2
To improve the bondability and ensure the reliability of Au/Cu ball bonds of the thermosonic (TS) wire-bonding process, an
argon-shielding atmosphere was applied to prevent the copper pad from oxidizing. With argon shielding in the TS wire-bonding
process, 100% gold wire attached on a copper pad can be achieved at the bonding temperature of 180°C and above. The ball-shear
and wire-pull forces far exceed the minimum requirements specified in the related industrial codes. In a suitable range of
bonding parameters, increasing bonding parameters resulted in greater bonding strength. However, if bonding parameters exceed
the suitable range, the bonding strength is deteriorated. The reliability of the high-temperature storage (HTS) test for Au/Cu
ball bonds was verified in this study. The bonding strength of Au/Cu ball bonds increases slightly with prolonged storage
duration because of diffusion between the gold ball and copper pad during the HTS test. As a whole, argon shielding is a successful
way to ensure the Au/Cu ball bond in the TS wire-bonding process applied for packaging of chips with copper interconnects. 相似文献
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D. Martin Knotter Ingrid A. RinkWim A.P. Claassen Jos H.M. Philipsen 《Microelectronic Engineering》2011,88(12):3452-3458
The impact of fluoride and AlOx contaminants on the quality of wire bonding (Au to Al welding) has been measured. No or minor impact of these contaminants has been found with a standard ball shear test. Despite an accelerated lifetime test, the shear strength remains above the required specification limits. Intermetallic coverage, the percentage of the interface between the bond ball and the bond pad where welding resulted in intermetallic diffusion, gives a better picture of the quality decay, but this method is too elaborate for production control and specification limits are unclear. 相似文献
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介绍了国内外应用市话铜线电缆开发宽带接人网的现状(包括标准化和市场两个方面)及其发展前景对市话铜线电缆的进一步开发和应用进行了分析并提出了一些建议。 相似文献
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《Microelectronics Reliability》2014,54(9-10):1661-1665
This paper describes the use of in-situ High Temperature Storage Life (HTSL) tests based on a four point resistance method to evaluate Cu wire interconnect reliability. Although the same set up was used in the past to monitor Au–Al ball bond degradation, a different approach was needed for this system. Using conventional statistical methods of failure probability distributions and a fixed failure criterion were found to be unsuitable in this case. Besides this, tests usually take very long until a sufficient percentage of the population have failed according to that criterion. A simple physical model was used to electrically quantify ball bond degradation due to the prevailing failure mechanism in a substantially smaller amount of test time. The method enabled the determination of activation energies for a number of moulding compounds and is extremely useful for a fast screening of such materials regarding their suitability for Cu wire. 相似文献