P. Alpern

Infineon Technologies, München, Bavaria, Germany

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Publications (32)15.76 Total impact

  • Kheng Chooi Lee, Peter Alpern
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    ABSTRACT: Moisture concentration at the critical material interface is the key parameter as far as moisture sensitivity of a plastic package is concerned. Using a simple 1-D moisture diffusion model, this parameter allowed us to predict the optimal baking time at 125°C for P-DSO14 and MQFP80: 4-16 and 6-24, hours, respectively, depending on the considered material interface. The theoretical predictions agree well with the experimental results. On the other hand, the standard IPC/JEDED J-STD-033C recommends a distinctly longer baking time of 43 hours.
    2014 IEEE International Reliability Physics Symposium (IRPS); 06/2014
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    ABSTRACT: At a given soldering temperature, Ts the delamination initiation between die surface and molding compound of a P-MQFP80 plastic package is determined only by the critical moisture concentration, Ccrit at this interface. In this work, the temperature dependence of critical moisture concentration Ccrit on delaminaton initiation was investigated. Ccrit was found to decrease with increasing soldering temperature.
    Reliability Physics Symposium (IRPS), 2012 IEEE International; 01/2012
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    ABSTRACT: In this article the metallization schemes of output DMOS drivers for automotive SmartPower integrated circuits (ICs) are discussed. In contrast to non-automotive applications the main concern is the thermal-mechanical stability of the metallization during inductive switching which leads to high thermal pulses within the metallization. These pulses can result in junction temperatures above 400°C. Additionally, automotive ICs used in under-hood applications encounter rough and fast environmental changes. Rapid junction temperatures changes between -40°C and 175°C result in high mechanical shear stresses within the metallization so that the dielectrics in the metallization can crack. In both cases the thermal-mechanical properties of the chip metallization can be improved by introducing new materials like 11μm thick copper layers on top of the chip for increasing the thermal capacitance of the DMOS and/or material additions within the aluminum to improve its stiffness.
    Interconnect Technology Conference and 2011 Materials for Advanced Metallization (IITC/MAM), 2011 IEEE International; 06/2011
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    ABSTRACT: Concerning thermomechanically induced failures, such as metal line deformation and passivation cracks, there is a practicable way to achieve the zero-defect limit of plastic-encapsulated power devices. This limit can be reached by evaluating the influence of the major components involved and, consequently, by selecting the appropriate materials and measures. On the other hand, the interdependence between all components must always be kept in mind, i.e., chip and package have to be regarded as an entity. An important finding was that applying simply one improvement step will not necessarily lead to the desired goal. Only the implementation of all improvement steps considering their interdependence is the key for the perfect overall system chip and package. In Part I of this series of papers, the yield stress of the power metallization is shown to play a crucial role for the generation of metal deformation and passivation cracks. Understanding the ratcheting mechanism led to the development of a new layered metallization material with a distinctly increased yield stress, resulting in a considerably reduced failure generation.
    IEEE Transactions on Device and Materials Reliability 07/2009; DOI:10.1109/TDMR.2009.2018299 · 1.54 Impact Factor
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    ABSTRACT: Concerning thermomechanically induced failures, such as metal line deformation and passivation cracks, there is a practicable way to achieve the zero-defect limit of plastic-encapsulated power devices. This limit can be reached by evaluating the influence of the major components involved and, consequently, by selecting the appropriate materials and measures. On the other hand, the interdependence between all components must always be kept in mind, i.e., chip and package have to be regarded as an entity. An important finding was that applying simply one improvement step will not necessarily lead to the desired goal. Only the implementation of all improvement steps considering their interdependence is the key for the perfect overall system chip and package. In Part II of this series of papers, the thermomechanical influence of the molding compound (MC) on the chip, i.e., the root cause of metal deformation and passivation cracks, was studied in great detail. Concerning the generation of these failures, the coefficient of thermal expansion was shown to play a key role. However, for a full understanding of the thermomechanically induced damage, the viscoelastic properties of the MC have to be considered.
    IEEE Transactions on Device and Materials Reliability 07/2009; DOI:10.1109/TDMR.2009.2018655 · 1.54 Impact Factor
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    ABSTRACT: Concerning thermomechanically induced failures such as metal-line deformation and passivation cracks, there is a practicable way to achieve the zero-defect limit of plastic-encapsulated power devices. This limit can be reached by, first, evaluating the influence of the major components involved and, consequently, by selecting the appropriate materials and measures, and, second, by always keping in mind the interdependence between all components, i.e., chip and package have to be regarded as an entity. An important finding was that applying simply one improvement step will not necessarily lead to the desired goal. Only the implementation of all improvement steps considering their interdependence is the key for the perfect overall system chip and package. In Part III of this series of papers, the influence of passivation and die coating materials on thermomechanical damage is investigated. Finally, it is shown that an intelligent chip design, in combination with a stiff Al multilayer, a low-stress molding compound (low coefficient of thermal expansion and high Young's modulus), a new passivation material, and an appropriate polyimide layer, may reduce the thermomechanical damage to zero, even for electronic power devices..
    IEEE Transactions on Device and Materials Reliability 07/2009; DOI:10.1109/TDMR.2009.2018656 · 1.54 Impact Factor
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    ABSTRACT: It is well known that high temperature storage can degrade wire bonding contacts significantly due to interdiffusion of pad metal and bonding wire. Looking at harsh applications such as engine management we notice an additional failure mode caused by the temperature gradient during the pulsed active cycling period. Especially when we aim at components with high temperature capability and we substitute the power aluminium metallisation with power copper in order to avoid the formation of lifetime limiting intermetallics, the degradation of wire bonds (Au, Al, Cu) must be assessed with respect to the electrical pulse width, the dissipated power and the number of active cycles, which can exceed 500 millions in automotive applications. This paper presents experimental data with different temperature stress. The time dependent temperature distribution in the device is determined with an electrothermal simulator (TESI). The calculated temperature gradients will be used to enable a thermal-mechanical simulation (ANSYS). As a result a prediction, which kind of pulses can reduce the lifetime of the components under investigation, should be possible.
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    ABSTRACT: In this paper, a novel mechanism is shown to cause the failure evolution in a metallization system under fast temperature cycle stress. The failure evolution is triggered by the lateral temperature distribution across the device, which causes an accumulating plastic deformation of the metallization. The root cause for the deformation emerges at the position of the maximum gradient in temperature.
    IEEE Transactions on Device and Materials Reliability 10/2008; 8(3-8):590 - 599. DOI:10.1109/TDMR.2008.2002359 · 1.54 Impact Factor
  • Peter Alpern, Kheng Chooi Lee
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    ABSTRACT: By identifying the moisture concentration at the weakest material interface as the critical parameter for the defect onset, the quantitative prediction of moisture-induced delamination between the molding compound and die surface in plastic packages was realized using a simple 1-D diffusion model. As a result, the delamination onset during multiple soak and reflow procedure, as prescribed by customers' specifications, was predicted from the IPC/JEDEC J-STD-020C moisture sensitivity level. For the case studied here, the soldering peak temperature had the most significant influence on the moisture sensitivity of the package. The remaining part of the soldering temperature profile (ramp up and down) was found to have a rather small influence.
    IEEE Transactions on Device and Materials Reliability 10/2008; DOI:10.1109/TDMR.2008.2002340 · 1.54 Impact Factor
  • K.C. Lee, P. Alpern
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    ABSTRACT: By identifying the moisture concentration at the weakest material interface as the critical parameter for the defect onset, the quantitative prediction of moisture induced delamination between molding compound and die surface in plastic packages was realized. As a result, the delamination onset during multiple soak and reflow procedure, as prescribed by customers' specifications, was predicted from the IPC/JEDEC J-STD-020C moisture sensitivity level.
    Reliability physics symposium, 2007. proceedings. 45th annual. ieee international; 05/2007
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    ABSTRACT: During operation double-diffused-MOS (DMOS) transistors are subjected cyclically to severe temperature pulses. The resultant thermo-mechanical stress causes a viscoplastic deformation of the metallization. This increases the local stress on the interlayer dielectric (ILD) beyond a critical limit and results in ILD cracking. The DMOS fails due to electric short-circuits, that are caused by extruding aluminum. Due to its relevance for the DMOS design, the influence of the conductor line width is studied with a special test structure (Nguyen et al., 2002). From the observed failure evolution an effective method to improve fast temperature-cycle reliability is derived.
    Reliability physics symposium, 2007. proceedings. 45th annual. ieee international; 05/2007
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    ABSTRACT: Plastic encapsulated devices that are exposed to Temperature Cycling (TC) tests undergo an excessive mechanical stress due to different Coefficients of Thermal Expansion (CTE) of the various materials used in the system. Especially in the corners of the die, passivation cracks and shifted metal lines can be observed, which demonstrates an increasing mechanical stress from chip center to the corners of the die. This effect has been known for a long time. This paper presents a simple measurement technique to quantify the mechanical shear stress at the chip‐Mold Compound (MC) interface by measuring the deformation of a periodical metal structure. Based on this deformation measurement, we evaluated the stress distribution within the package, and the influence of different parameters such as number of cycles and chip size. Furthermore, these experimental results were compared with FEM simulation, and showed good agreement but could not account in all cases for the total amount of observed shift. © 2006 American Institute of Physics
    02/2006; 817(1):139-144. DOI:10.1063/1.2173543
  • K.C. Lee, A. Vythilingam, P. Alpern
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    ABSTRACT: The moisture concentration at the chip surface is the important parameter for the moisture sensitivity of the P-MQFP80 product considered here. When the critical moisture concentration at the die surface is reached, delamination occurs after soldering shock, e.g at 240°C. This critical moisture concentration, which can be determined by experiments conducted at 30°C/60% relative humidity (RH) followed by soldering shock, allows to predict the product’s moisture performance at other ambient conditions. In the case studied here, prediction was done at a customer use condition of 30°C/85% RH. Furthermore, this work showed that preconditioning of plastic packages not only induces the onset of delamination at the die surface but it appears to weaken the adhesion at this interface as well. As a result, delamination failure starts to occur earlier (i.e. within shorter moisture exposure time) in the devices tested after subsequent thermal cycling stress test. A simple moisture diffusion analytical model is proposed here for predicting the optimal baking schedules for plastic SMD packages.
    Microelectronics Reliability 09/2005; DOI:10.1016/j.microrel.2005.07.079 · 1.43 Impact Factor
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    ABSTRACT: It has already been shown that it is possible to measure the Young's modulus of moulding compounds used for encapsulation of microelectronic devices with the impulse excitation technique at room temperature. For calculations and simulations of the thermo-mechanical stability of microelectronic devices during soldering it is also necessary to know the Young's modulus at higher temperatures up to 260°C. Investigations with the three-point bending method are even more time and material consuming than the measurements at room temperature. Therefore, we built a setup to allow measurements of the Young's modulus in a temperature range from room temperature up to 260°C. Investigations of the Young's modulus of four different moulding compounds are reported and compared with data from three-point bending tests.
    Polymer Testing 04/2005; 24(2):137-143. DOI:10.1016/j.polymertesting.2004.09.009 · 1.82 Impact Factor
  • P Alpern, KC Lee, R Tilgner
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    ABSTRACT: The Pb-free soldering temperature-time profile T(t) in the IPC/JEDEC J-STD-020 specification, which is used in the moisture sensitivity level (MSL) classification of plastic SMD packages, has a wide time range. We found that in a thick package, MQFP-80 the long soldering profile is worse than the short one whereas in a thin package, TSSOP-38 the result is surprisingly the reverse. Because moisture diffusion inside the package is much slower than thermal diffusion, the wide time range in T(t) profile is found to have an effect on the MSL of packages with different geometries. The results suggest a strong need to reduce the width of soldering range in the J-STD-020 specification. Further studies done on A2-coated leadframe packages, namely DSO-20 and MQFP-80, found quite similar MSL performance for both long and short soldering profiles.
    15th European Symposium on the Reliability of Electron Devices, Failure; 09/2004
  • P. Alpern, K.C. Lee
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    ABSTRACT: A simple model for the mode II popcorn effect is presented here for thin packages, e.g. TSSOP, TQFP. A package "stability parameter", relating to its moisture sensitivity, is derived from the popcorn model. It describes the critical factors for a robust package die-attach, mold compound properties and package, die and lead frame design for a given preconditioning and soldering process. Furthermore, nomograms generated from the model enable an easy estimation of the moisture sensitivity level of products with different die sizes for a given die pad size and package configuration for soldering temperatures up to 260°C (Pb-free soldering).
    Reliability Physics Symposium Proceedings, 2003. 41st Annual. 2003 IEEE International; 01/2003
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    ABSTRACT: A simple model for the Mode I popcorn effect is presented here for packages with rectangular die pads (P-DSO). A package "stability parameter," relating to its moisture sensitivity, is derived from the popcorn model. It describes the critical factors for a robust package-molding compound properties and package, leadframe design for a given preconditioning and soldering process. Furthermore, nomograms generated from the model facilitate an easy estimation of moisture sensitivity levels (between 1 and 5) of packages with different die pad sizes and molding compound underpad thicknesses and for different soldering temperatures ranging from 220°C to 260°C (lead-free soldering)
    IEEE Transactions on Components and Packaging Technologies 07/2002; DOI:10.1109/TCAPT.2002.1010021 · 0.96 Impact Factor
  • Mechanical Reliability-Simulation, Characterization and Testing, Fraunhofer Publication Series Micromaterials & Nanomaterials(M&N) edited by Bernd Michel, 05/2002: pages 59-66; Fraunhofer IZM Berlin,., ISBN: ISSN 1619-2486
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    ABSTRACT: Experiments were carried out using P-TQFP-176 packages to study the mode II popcorn effect in thin packages. The doming of the package backside was measured as a function of time and temperature. The measurements were performed using a line projection method. An "accelerated" increase in the doming was found to correlate with the onset of the package crack propagation. It was shown that when a constant critical doming angle is reached, package cracks begin to propagate toward the surface. This critical doming angle was found to be temperature independent between 170°C and 215°C. Furthermore the development of the package doming with time was described by a simple model based on the moisture diffusion from molding compound and die-attach material in combination with a bimaterial plate theory. The water content of the die-attach layer after preconditioning was calculated from the model and it was found to be in good agreement with the results of a three dimensional finite element simulation
    IEEE Transactions on Components and Packaging Technologies 04/2002; 25(1-25):56 - 65. DOI:10.1109/6144.991176 · 0.96 Impact Factor
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    ABSTRACT: Theoretical analysis of the popcorn phenomenon requires the thermo-mechanical and moisture diffusion properties of the polymers in the packages under investigation. Some of these properties, including fracture toughness, are given for the four commercially available epoxy molding compounds (EMCs) used. Fracture toughness measurements with precracked beams as well as analyses based on a simple method to estimate the toughness from bending experiments are used. For the latter investigations, the basic assumption is that the filler particles act as initial flaws. The problem is analytically treated as a beam with a surface crack, and an estimate of the critical fracture toughness can be calculated by a simple formula. By means of 3D-FE analyses the moisture diffusion into a thin quad flat pack (TQFP) package is studied for various standard moisture preconditioning levels. It is shown that the different popcorn failure types correspond to different moisture distributions within the die attach layer depending on the different preconditioning levels
    Polymers and Adhesives in Microelectronics and Photonics, 2001. First International IEEE Conference on; 02/2001