Effects of Bond Pad Thickness on Shear Strength of Copper Wire Bonds

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000068-000073 ◽  
Author(s):  
Subramani Manoharan ◽  
Chandradip Patel ◽  
Stevan Hunter ◽  
Patrick McCluskey
Keyword(s):  
Shear Strength ◽  
Shear Test ◽  
Failure Modes ◽  
High Reliability ◽  
Copper Wire ◽  
Test Method ◽  
Ball Bond ◽  
Wire Bond ◽  
Industry Standards ◽  
Wire Bonds

Abstract Copper (Cu) wire bonding is now widely accepted as a replacement for gold (Au), however, its use in high reliability applications is limited due to early failures in high temperature and humid conditions. The Au to Cu wire transition is mainly driven by cost savings though there are other advantages to Cu such as better electrical and thermal conductivity, slower intermetallic compound (IMC) formation and reduced wire sweep during transfer molding. Some automotive, industrial and aerospace industries are still reluctant to adopt Cu wire bonded products due to perceived risks of wire and bond pad cracks, the potential for corrosion, and some lack of understanding about its reliability in harsh conditions. A wire bond is considered good if destructive sampling qualification tests and periodic monitors pass for the batch. Tests include wire pull strength, wire bond shear, IMC coverage, and thickness of bond pad aluminum (Al) remaining beneath the bond. Nondestructive inspections also verify acceptable ball diameter and Al “splash”. This paper focuses on the bond shear test and its contribution to Cu ball bond reliability assessment, especially when changing Al bond pad thickness. A new revision of the JEDEC Wire Bond Shear Test Method, JESD22-B116B, has just been released, to include Cu wirebonds for the first time. It helps to clarify shear test failure modes for Cu ball bonds. However, there are still questions to be answered through research and experimentation, especially to learn the extent to which one may predict Cu ball bond reliability based on shear test results. Pad Al thickness is not considered in the current industry standards for shear test. Yet bond pad Al thickness varies widely among semiconductor products. This research is intended to contribute toward improved industry standards. In this study, power and time bonding parameters along with bond pad thickness are studied for bond strength. Several wire bonds are created at different conditions, evaluated by optical microscope and SEM, IMC% coverage and bond shear strength. Similar bonding conditions are repeated for bond pads of 4um, 1um and 0.5um thickness.

Shear Ram Height Characterization for Copper Wire Bond Shear Test

2012 ◽  
Vol 229-231 ◽  
pp. 674-677 ◽  
Author(s):  
Z. Sauli ◽  
V. Retnasamy ◽  
A. H. M. Shapri ◽  
N. A. Z. Rahman ◽  
W.M.W. Norhaimi ◽  
...  
Keyword(s):  
Shear Test ◽  
Copper Wire ◽  
Equivalent Strain ◽  
Von Mises Stress ◽  
Stress And Strain ◽  
Strain Response ◽  
Element Analysis ◽  
Ball Bond ◽  
Wire Bond ◽  
Von Mises

The work here investigates the height effect during a shearing process of a copper ball bond in a wire bond. Finite element analysis was used to investigate this analysis.The effects of the shear ram height on the stress and strain response of the copper ball bond were investigated. The results obtained hows there is a significant effect of the shear height to the Von Mises stress and equivalent strain response to the copper ball bond during the shearing simulation.

Shear Ram Speed Characterization for Copper Wire Bond Shear Test

2012 ◽  
Vol 229-231 ◽  
pp. 670-673
Author(s):  
Z. Sauli ◽  
V. Retnasamy ◽  
A. H. M. Shapri ◽  
N. A. Z. Rahman ◽  
W.M.W. Norhaimi ◽  
...  
Keyword(s):  
Finite Element ◽  
Shear Test ◽  
Copper Wire ◽  
Preliminary Investigation ◽  
Von Mises Stress ◽  
Stress And Strain ◽  
Strain Response ◽  
Ball Bond ◽  
Wire Bond ◽  
Ram Speed

This paper presents the evaluation of the stress and strain response of the copper ball bond during wire bond shear test using finite element analysis. A 3D non-linear finite element model was developed for the simulation. The effects of the shear ram speed on the stress and strain response of the copper ball bond were investigated. A preliminary investigation confirms that shear ram speed has a significant effect on the von mises stress and equivalent strain response of the copper ball bond during wire bond shear test

Reliability Evaluation of Cu-Al WB in High Temperature and High Current Applications

2021 ◽  
Author(s):  
Pradeep Lall ◽  
Sungmo Jung
Keyword(s):  
High Temperature ◽  
High Reliability ◽  
Copper Wire ◽  
Planck Equation ◽  
Operating Conditions ◽  
Polarization Curves ◽  
Automotive Electronics ◽  
Wire Bonds ◽  
Chlorine Ions ◽  
Copper Aluminum

Abstract High reliability harsh environment applications necessitate a better understanding of the acceleration factors under operating stresses. Automotive electronics has transitioned to the use of copper wire for first level interconnects. A number of copper wire formulations have emerged including palladium coated copper and gold-flash palladium coated copper. The corrosion reliability of copper wire bonds in high temperature conditions is not yet fully understood. The EMC used to encapsulate chips and interconnects can vary widely in formulation, including pH, porosity, diffusion rate, composition of contaminants and contaminant concentration. To realistically represent the expected wirebond reliability, there is need for a predictive model that can account for environmental conditions, operating conditions, and exposure to EMCs. In this paper, different EMCs were studied in a high-temperature-current environment with temperature range of 60°C–100°C under current of 0.2A–1A. The diffusion kinetics based on the Nernst-Planck Equation for migration of the chlorine ions has been coupled with the Butler-Volmer equation for corrosion kinetics to create a Multiphysics model. Polarization curves have been measured for copper, aluminum and intermetallics under a number of pH values, and chlorine-ion concentrations. Tafel parameters have been extracted through measurements of the polarization curves.

Wire Bond Shear Test Simulation on Sharp Groove Surface Bond Pad

2012 ◽  
Vol 622-623 ◽  
pp. 647-651 ◽  
Author(s):  
Z. Sauli ◽  
V. Retnasamy ◽  
S. Taniselass ◽  
A.H.M. Shapri ◽  
R. Vairavan
Keyword(s):  
Stress Response ◽  
Shear Test ◽  
Copper Wire ◽  
Gold Wire ◽  
Shear Tests ◽  
Groove Surface ◽  
Wire Bond ◽  
Packaging Industry ◽  
Semiconductor Packaging ◽  
Surface Bond

Wire bonding process is first level interconnection technology used in the semiconductor packaging industry. The wire bond shear tests are used in the industry to examine the bond strength and reliability of the bonded wires. Hence, in this study thesimulation on wire bond shear test is performed on a sharp groove surface bond pad. ANSYS ver 11 was used to perform the simulation. The stress response of the bonded wires are investigated.The effects of three wire materials gold(Au), aluminum(Al) and copper(Cu) on the stress response during shear test were examined. The simulation results showed that copper wire bond induces highest stress and gold wire exhibits the least stress response.

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.

Experimental Study on Interlaminar Shear Properties of T300/BMI Composite Laminates

2013 ◽  
Vol 718-720 ◽  
pp. 157-161
Author(s):  
Zong Hong Xie ◽  
Hai Han Liu ◽  
Jian Zhao ◽  
Jun Feng Sun ◽  
Fei Peng ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Shear Test ◽  
Failure Modes ◽  
Shear Failure ◽  
Test Method ◽  
Test Results ◽  
Shear Properties ◽  
Test Fixture ◽  
Iosipescu Shear Test ◽  
Interlaminar Shear

A modified test fixture to measure the shear properties of composite laminates was designed and manufactured based upon Iosipescu shear test method. Tests on interlaminar shear propertis of T300/BMI composite laminates were conducted according to ASTM D 5379 test standard. Interlaminar shear stress/strain curves and shear failure modes were obtained. The test results showed that the modified shear test fixture and test method were effective in measuring the shear properties of composite laminates.

High Performance Etchable RoHS Compliant Thick Film Gold Conductor

2018 ◽  
Vol 2018 (1) ◽  
pp. 000620-000627 ◽  
Author(s):  
Samson Shahbazi ◽  
Gregg Berube ◽  
Stephanie Edwards ◽  
Ryan Persons ◽  
Caitlin Shahbazi
Keyword(s):  
Thick Film ◽  
High Performance ◽  
Failure Modes ◽  
High Reliability ◽  
Film Surface ◽  
Wire Bonding ◽  
Aluminum Wire ◽  
Sem Images ◽  
Lead And Cadmium ◽  
Wire Bond

Abstract The thick film paste manufacturers are expected to produce conductors which are lead and cadmium free, yet have excellent fired film properties and the same performance and properties as the cadmium and lead containing formulations. The fired film surface of these conductors must be defect free (i.e. imperfections, pills, agglomerates) after multiple firing steps and must perform on dielectric as well as substrates from different suppliers. Typically, the thick film gold conductors are used in high reliability applications such as medical devices, military applications, and high frequency circuits, which require robust performance at high and low temperatures, in chemically aggressive environments, or extremely humid conditions. As circuits decrease in size and become more complex, the thick film gold properties become increasingly critical. The challenge is to develop an alternative gold conductor formulation, which can print and resolve fine features (down to 4 mil lines and spaces) as well as have the ability to be etched for higher density circuit designs (down to 1–2 mil lines and spaces). Gold conductors are typically used in conjunction with other high temperature thick films so good performance after multiple firings was also a targeted requirement. Heraeus has been proactive for the past decade in the development of thick film products that are both RoHS (lead and cadmium free) as well as REACH compliant. This paper discusses the experiments that were performed in order to understand the contribution of gold powder, organic and inorganic system to improve the fired film performance. These formulations were compared against existing gold conductors including the high performance gold conductor options as well as other available standard gold conductor options. Thin wire bonding trials including both gold and aluminum wire are used to compare influences of raw materials which includes high volume wire bonding reliability including failure modes and aged wire bond adhesion at elevated temperature exposures (300°C) for extended periods of time. In order to analyze fired film morphology and link this up to wire bond performance, SEM images of the conductor surface and cross sections were conducted. These studies resulted in a newly developed thick film gold conductor paste for use in a wide variety of applications. We present wire-bonding data with gold and aluminum wire and reliability results on both 96% Al2O3 ceramic substrates as well as on top of standard dielectrics.

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