To Study the High Temperature Effects on Ball Bonds Using Low K Material in Wire Bond Devices

2007 ◽  
Author(s):  
S. A. Kudtarkar ◽  
R. Murcko ◽  
K. Srihari ◽  
S. Saiyed
Keyword(s):  
High Temperature ◽  
Mechanical Stability ◽  
Semiconductor Industry ◽  
Gold Wire ◽  
Wire Bonding ◽  
Mechanical Stresses ◽  
Wire Bond ◽  
Ball Bonds ◽  
Bond Pads ◽  
Low K

Wire bonding is widely used as one of the main interconnect alternatives. This technique applies significant mechanical stresses on the bond pads along with heat and ultrasonic energy to form a bond. An interconnection of copper plus low k material has been a focus of the semiconductor industry with the goal of reducing interconnection delays. The material is below the wire bond pads and complicates the mechanical stability of the device during wire bonding. The low k materials that are suggested are very sensitive to these mechanical stresses. This generates a significant reliability concern for the underlying metal structures. In addition, the integrity of the bond formed may be negatively impacted from a reliability perspective because of the softer material properties of the dielectric. This research explores the ball bond integrity for die with SiO2 and low k dielectric underlying material respectively, using 0.8 mil thick (20 microns) gold wire. Accelerated tests, such as high temperature storage at 150°C and 175°C, were conducted to assess the reliability of these bonds. The results of this investigation reveal that the ball bond’s strength degrades after high temperature tests due to the occurrence of Kirkendall voids between the gold wire and the aluminum bond pad. The degradation recorded was more severe for regular die than its low k counterpart.

High Temperature Storage and HAST Reliability of Copper-Aluminum Wirebond Interconnects

2014 ◽  
Author(s):  
Pradeep Lall ◽  
Shantanu Deshpande ◽  
Luu Nguyen
Keyword(s):  
High Temperature ◽  
Copper Wire ◽  
Gold Wire ◽  
Wire Bonding ◽  
Remaining Useful Life ◽  
Thermal Resistivity ◽  
Wire Bond ◽  
Trade Offs ◽  
Marquardt Algorithm ◽  
Temperature And Humidity

Gold wire bonding has been widely used as first-level interconnect in semiconductor packaging. The increase in the gold price has motivated the industry search for alternative to the gold wire used in wire bonding and the transition to copper wire bonding technology. Potential advantages of transition to Cu-Al wire bond system includes low cost of copper wire, lower thermal resistivity, lower electrical resistivity, higher deformation strength, damage during ultrasonic squeeze, and stability compared to gold wire. However, the transition to the copper wire brings along some trade-offs including poor corrosion resistance, narrow process window, higher hardness, and potential for cratering. Formation of excessive Cu-Al intermetallics may increase electrical resistance and reduce the mechanical bonding strength. Current state-of-art for studying the Cu-Al system focuses on accumulation of statistically significant number of failures under accelerated testing. In this paper, a new approach has been developed to identify the occurrence of impending apparently-random defect fall-outs and pre-mature failures observed in the Cu-Al wirebond system. The use of intermetallic thickness, composition and corrosion as a leading indicator of failure for assessment of remaining useful life for Cu-al wirebond interconnects has been studied under exposure to high temperature and temperature-humidity. Damage in wire bonds has been studied using x-ray Micro-CT. Microstructure evolution was studied under isothermal aging conditions of 150°C, 175°C, and 200°C till failure. Activation energy was calculated using growth rate of intermetallic at different temperatures. Effect of temperature and humidity on Cu-Al wirebond system was studied using Parr Bomb technique at different elevated temperature and humidity conditions (110°C/ 100%RH, 120°C/ 100%RH, 130°C/ 100%RH) and failure mechanism was developed. The present methodology uses evolution of the IMC thickness, composition in conjunction with the Levenberg-Marquardt algorithm to identify accrued damage in wire bond subjected to thermal aging. The proposed method can be used for quick assessment of Cu-Al parts to ensure manufactured part consistency through sampling.

Nanoindentation Study on Heat Treated Gold Wire Bonding

2016 ◽  
Vol 857 ◽  
pp. 31-35
Author(s):  
Wan Yusmawati Wan Yusoff ◽  
Azman Jalar ◽  
Norinsan Kamil Othman ◽  
Irman Abdul Rahman
Keyword(s):  
High Temperature ◽  
Storage Period ◽  
Gold Wire ◽  
Constant Load ◽  
Wire Bonding ◽  
Nanoindentation Test ◽  
High Temperature Storage ◽  
Gold Ball ◽  
Ball Bonds ◽  
Temperature Storage

The effect of high temperature storage of gold ball bonds towards micromechanical properties has been investigated. Gold wire from thermosonic wire bonding exposed to high temperature storage at 150 °C for 10, 100 and 1000 hours. The nanoindentation test was used in order to evaluate the high temperature storage effect on wire bonding in more details and localized. Prior to nanoindentation test, the specimens were cross-sectioned diagonally. The constant load nanoindentation was performed at the center of gold ball bond to investigate the hardness and reduced modulus. The load-depth curve of nanoindentation for the high temperature storage gold wire has apparent the discontinuity during loading compared to as-received gold wire. The hardness value increased after subjected to high temperature storage. However, the hardness decreased when the storage period is extended. The decreasing in the hardness value may due to the grain size of Au metal which recrystallized after subjected to high temperature storage. The results obtained from nanoindentation is important in assessing the high temperature storage of wire bonding.

Chemical selective coating of nickel / palladium / gold metallization on screen-printed thick film on LTCC and Al2O3 ceramic for high temperature applications

2012 ◽  
Vol 2012 (CICMT) ◽  
pp. 000334-000338
Author(s):  
Jens Müller ◽  
Thomas Mache ◽  
Torsten Thelemann
Keyword(s):  
High Temperature ◽  
Thick Film ◽  
Low Cost ◽  
Gold Wire ◽  
Wire Bonding ◽  
Pure Gold ◽  
Al2o3 Ceramic ◽  
Selective Coating ◽  
Silver Palladium ◽  
Silver Silver

Electroless plating on silver is a low cost alternative to printing of mixed metals or pure gold paste systems on LTCC. It overcomes the necessity to have material transitions from inner to outer layers or from conductor lines to wire bonding- or solder-pads. Since no commercial process and material set for silver thick film conductors has been available on the market a proprietary Ni/Pd/Au coating technology was developed for the use on silver inks for LTCC and Al2O3-ceramic as a base for both soldering and wire bonding. The work included the screening of different chemicals as well as several silver paste systems from two commercial vendors. Conductor adhesion, plating layer thicknesses, plating accuracy, (lead free) solderability and gold wire-bondability were assessed to optimize the process. Layers of about 5 microns Ni, (0.1 to 0.3) microns Pd and (0.05 to 0.15) microns Au were electrolessly deposited. The developed Ni-Pd-Au finish is an economical alternative with only about a quarter of the cost compared to the conventional use of silver, silver / palladium and gold compounds for ceramic substrates. This technology allows coating of the structures down to a fine pad size of 200×200 microns and a minimum line width of 100 microns, without reducing the adhesion mechanism between thick-film metallization and ceramic substrate. By covering of pure conductors with high temperature glass or dielectrics, further material saving is possible. Besides, the process offers also very good coating of structures in cavities.

High Temperature Storage Reliability of Bond Resistance of Palladium-Coated Copper Ball Bonds

2017 ◽  
Vol 2017 (1) ◽  
pp. 000432-000437 ◽  
Author(s):  
Michael David Hook ◽  
Michael Mayer ◽  
Stevan Hunter
Keyword(s):  
High Temperature ◽  
Ball Bond ◽  
Wire Bonds ◽  
High Temperature Storage ◽  
Ball Bonding ◽  
Ball Bonds ◽  
Bond Pads ◽  
Wire Resistance ◽  
Temperature Storage

Abstract Reliability of wire bonds made with palladium-coated copper (PCC) wire of 25 μm diameter is studied by measuring the wire bond resistance increase over time in high temperature storage at 225 °C. Ball bonds are made on two bond pad thicknesses and tested with and without mold compound encapsulation. Bond pads are aluminum copper (Al-0.5%Cu), 800 nm and 3000 nm thick. The wirebonding pattern is arranged to facilitate 4-wire resistance measurements of 12 bond pairs in each 28-pin ceramic test package. The ball bonding recipe is optimized to minimize splash on 3000 nm Al-0.5%Cu with shear strength at least 120 MPa. Ball bond diameter is 61 μm and height is 14 μm. Measurements include bond shear test data and in-situ resistance before and during high temperature storage. Bonds on 3000 nm pads are found to be significantly more reliable than bonds on 800 nm pads within 140 h of aging.

Assessment of 20 Micrometer Diameter Wires for Wire Bond Interconnect Technology

2007 ◽  
Author(s):  
S. Saiyed ◽  
S. A. Kudtarkar ◽  
R. Murcko ◽  
K. Srihari
Keyword(s):  
High Temperature ◽  
Stress Test ◽  
Small Diameter ◽  
Mechanical Tests ◽  
Stress Tests ◽  
Bonding Wire ◽  
Chip Area ◽  
Wire Bond ◽  
Ball Bonds ◽  
The Wire

In the domain of wire bonding technology, the size and pitch of bond pads and ball bonds are shrinking to accommodate the demand for higher I/Os and increased functionality per chip area. This trend serves as a catalyst for bonding wire manufacturers to continuously develop lower diameter bonding wires. One mil (25 μm) diameter bonding wire, used widely in this interconnection technique, is now being replaced by 0.8 mil (20 μm) diameter bonding wire. In keeping with the need for higher operating speeds and higher temperatures for today’s ICs, the reliability of ball bonds formed by small diameter wires is of concern and requires investigation. This study explores the effects of 0.8 mil (20 μm) diameter bonding wire on the wire bond ball joint reliability and compares these effects with 1.0 mil (25 μm) diameter bonding wire. The reliability of the ball bonds was assessed using mechanical tests (wire pull and ball shear) for units subjected to stress tests such as the unbiased highly accelerated stress test and high temperature storage tests. The results of this investigation reveal that both the wire diameters are able to sustain their integrity after moisture testing. But, the bond strength degrades after high temperature tests due to the Kirkendall voiding mechanism occurring between gold wire and the aluminum bond pad.

Reliability Assessment of Cu-Al WB Under High Temperature and High Voltage Bias Application

2020 ◽  
Author(s):  
Pradeep Lall ◽  
Sungmo Jung
Keyword(s):  
High Temperature ◽  
High Voltage ◽  
Galvanic Corrosion ◽  
Copper Wire ◽  
Ionic Transport ◽  
Gold Wire ◽  
Process Window ◽  
Voltage Bias ◽  
Wire Bond ◽  
Wire Bonds

Abstract Electronics in automotive underhood environments may be subjected to high temperature in the range of 125–200°C. Transition to electric vehicles has resulted in need for electronics capable of operation under high voltage bias. Automotive electronics has simultaneously transitioned to copper wire-bond from gold wire-bond for first-level interconnections. Copper has a smaller process window and a higher propensity for corrosion in comparison with gold wire bonds. There is scarce information on the reliability of copper wire bonds in presence of high voltage bias under operation at high temperature. In this paper, a multiphysics model for micro galvanic corrosion in the presence of chlorine is introduced. The diffusion cell is used to measure the diffusivity of chlorine in different pH values and different temperatures. Diffusivity measurements are incorporated into the 3D ionic transport model to study the effect of different environmental factors on the transport rate of chlorine. The tafel parameters for copper, aluminum and intermetallics have been extracted through measurements of the polarization curves. The multiple physics of ionic transport in presence of concentration gradient, potential gradient is coupled with the galvanic corrosion.

Novel Method of Separating Probe and Wire Bond Regions without Increasing Die Size and Reducing Weak Fab-Back End of Line Adhesion Interfaces

2006 ◽  
Vol 3 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Chu-Chung (Stephen) Lee ◽  
Tu Anh Tran ◽  
Bill Williams ◽  
Jody Ross
Keyword(s):  
Yield Loss ◽  
Wire Bonding ◽  
Wafer Fabrication ◽  
Wafer Level ◽  
Silicon Area ◽  
Wire Bond ◽  
Bond Yield ◽  
Fine Pitch ◽  
The Wire ◽  
Bond Pads

The drive for enhanced electrical performance and reduced silicon area has triggered significant changes in wafer fabrication, wafer level testing, and packaging technologies. In the wafer fabrication era, copper is quickly replacing aluminum as the interconnect metal of choice for technologies 0.13μm and below. To overcome the difficulty of wire bonding onto readily oxidized copper bond pads, capping copper bond pads with aluminum has been the industry standard method for wire bonding. In terms of wafer level testing and packaging, the resulting fine pitch geometry has created challenges for both cantilever probe and wire bond processes. Pad damage due to probe marks during probe process has been shown to cause “non-sticks” and “lifted bonds” at the wire bonding process. The wire bond yield loss due to pad damage is aggravated for fine pitch since increasingly smaller bonded ball diameters are formed on top of the same damage area caused by the probe mark. Wire Bond parameter optimization can minimize wire bond yield loss but cannot eliminate the problem. One logical solution is to lengthen the bond pad to create separate regions for probing and wire bonding. However, this method can result in a larger die size. This paper will reveal a unique bond pad structure that provides separate regions but yet results in no impact to the existing die size. This bond pad structure utilizes the aluminum cap layer to create a longer bond pad without changing the size of the underlying copper last metal, resulting in no impact to the existing die size. Evaluations were conducted on 0.13μm CMOS technology, with cantilever probing and wire bonding on 52μm bond pad size. Failure analysis and test methods to detect failures will be discussed. Designs of experiments for probing and wire bonding processes, characterization studies, and reliability results will be presented. Furthermore, a unique Extended Armored Pad (EAP) has been introduced for the purpose of reducing the Ta-Cu interface area under the Aluminum bond pad region because the Ta-Cu adhesion is known to be one of the weakest interfaces for Cu-interconnect BEOL processes.

Evaluation of Secondary Wire Bond Integrity on Ag Plated and Ni/Pd Based Lead Frame Plating Finishes

2009 ◽  
Author(s):  
G. Srinivasan ◽  
R. Murcko ◽  
K. Srihari
Keyword(s):  
High Temperature ◽  
Failure Analysis ◽  
Wire Bonding ◽  
Strength Test ◽  
Lead Frame ◽  
Wire Bond ◽  
Pull Strength ◽  
High Temperature Storage ◽  
The Wire ◽  
Temperature Storage

As the legislatures demand the use of lead (Pb) free plating finishes in lead frame manufacturing, different plating finishes are being offered by the lead frame makers. Lead frames are most often designed with two different Pb free plating finishes, primarily tin and nickel/palladium (Ni/Pd) based. The tin post mold plated lead frames use silver selective plating on the lead fingers for secondary wire bonding whereas the pre-plated Ni/Pd based lead frames use the same Ni/Pd based finish throughout. Enhanced versions of Ni/Pd based plating finishes such as nickel/palladium/gold (Ni/Pd/Au), nickel/palladium/gold-palladium (Ni/Pd/Au-Pd) and nickel/palladium/gold-silver (Ni/Pd/Au – Ag) are now available to further improve the wirebondability, solderability and reliability of the package. The development of a new lead frame finish involves a wide variety of concerns which must be addressed and thus mandates further evaluation of these new structures. Using the common Pb free lead frame plating finish of selectively plated silver (Ag) as the basis, a comparative approach was used to evaluate the secondary wire bond integrity of a 25 micron (1 mil) thick gold wire on Ni/Pd based lead frame plating finishes. The integrity of the secondary wire bonds for different plating finishes was investigated at various assembly thermal exposure stages using the wire pull strength test as the arbiter. Reliability tests, such as High Temperature Storage (HTS) and Unbiased Highly Accelerated Stress Test (UBHAST), were also conducted. Finally, failure analysis was conducted with the help of metallographic cross sectioning, SEM/EDX (Scanning Electron Microscope/Energy Dispersive X-ray) analysis and statistical analysis of the wire pull strength test results. Before wire bonding the lead frames, the plating surface was investigated for its surface integrity with the help of plating quality tests, such as: (i) adhesive tape test, (ii) bend test, (iii) heating test and the (iv) scribing test. Also, since wire pull is a destructive test, a statistical method called a nested gauge R&R study was used to estimate the repeatability and reproducibility of the measurement system. Failure analysis showed that there were silver and copper migrations over the Ag plated lead frame when exposed to a high temperature storage test at 175°C for 1000 hrs, but this did not affect the bond integrity. However, the Ni/Pd based lead frames did not show any metal migration since nickel acts as a barrier against the base metal diffusion.

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