Query: Reliability Enhancement of a Power Semiconductor With Optimized Solder Layer Thickness

Candidate papers:

abstract: This article deals with the reliability of a power semiconductor exposing to the severe thermal stresses. The importance of solder joint thickness on the power semiconductor's useful lifetime is demonstrated in this article. Solder layer thickness has knock on effects both on the creep accumulated strain and thermal characteristics of the power semiconductors. Since, these effects are in contradictory of each other, a trade off seems to be essential to optimize the solder layer thickness. Thereby, thermo mechanical behavior of a discrete power semiconductor under the thermal mission profile was simulated and the results were integrated to the actual conditions. The simulation results reveal that after thermal cycling, some creep strain is produced in the solder layer especially at the corners. The thinner the solder joint was, the greater accumulated creep strain was observed leading to the faster degradation. On the contrary, the thicker the solder layer was, the larger thermal resistance was observed leading to the higher junction temperature. Accordingly, the article is concentrated on optimizing the solder layer thickness based on these two issues. The scanning electron microscope micrographs, the EDS maps and X ray diffraction analysis were also taken to indicate the solder layer thickness effects on the number of voids and their propagations in the different solder layer thicknesses. The experimental tests validate the expected results in the extracted simulations.
author_names: Elakkiya R

G Kavithaa

Vahid Samavatian

K Alhaifi

Alireza Kokabi

Hossein Moayedi
title: Reliability Enhancement of a Power Semiconductor With Optimized Solder Layer Thickness
venue: IEEE Transactions on Power Electronics
year: 2020

abstract: Fundamentals of Power Semiconductor Devices provides an in depth treatment of the physics of operation of power semiconductor devices that are commonly used by the power electronics industry. Analytical models for explaining the operation of all power semiconductor devices are shown. The treatment focuses on silicon devicesandincludes the unique attributes and design requirements for emerging silicon carbide devices.
author_names: B Jayant Baliga
title: Fundamentals of Power Semiconductor Devices
year: 2008

abstract: A questionnaire survey was carried out to determine the industrial requirements and expectations of reliability in power electronic converters. The survey was subjective and conducted with a number of high profile semiconductor manufacturers, integrators, and users in the aerospace, automation, motor drive, utility power, and other industry sectors. According to the survey, power semiconductor devices ranked the most fragile components. It was concluded that main stresses were from the environment, transients, and heavy loads, which should be considered during power electronic system design and normal operation. This paper has also highlighted that there is a significant need identified by the responders for better reliability monitoring methods and indicators.
author_names: Shaoyong Yang

Angus T Bryant

Phil Mawby

Dawei Xiang

Li Ran

Peter J Tavner
title: An Industry Based Survey of Reliability in Power Electronic Converters
venue: IEEE Transactions on Industry Applications
year: 2011

abstract: Power cycling capability is one of the most important reliability items in application semiconductor modules. This paper describes the mechanism of power cycling by analysis of the structure of lead based solder and joint failure due to fatigue was studied to ascertain improvement in the power cycling lifetime. Lead based solder has a relatively weaker yield strength which means that plastic deformation leads to deterioration. Therefore, tin silver based solder was selected as a higher yield strength material, and a new composition which has both excellent mechanical properties and wettability was developed. Concerning the failure mechanism of power cycling for this newly developed solder material, solder joint failure and aluminum wire bond failure were clearly distinguished, and the lifetime prediction curve was clarified by FEM analysis and detailed failure analysis. Furthermore, it was proved that the deterioration of new tin silver based solder is caused by thermal fatigue with the grain growth of tin. Thus, longer power cycling capability is achieved by using this newly developed solder instead of conventional lead based solder.
author_names: Akira Morozumi

K Yamada

T Miyasaka

Yoshio Seki
title: Reliability of power cycling for IGBT power semiconductor modules
venue: Conference Record of the 2001 IEEE Industry Applications Conference. 36th IAS Annual Meeting (Cat. No.01CH37248)
year: 2001

abstract: In this work, we show that how solder thickness can affect the IGBTs' useful lifetime. Hence, the thermo mechanical response of joints in IGBT discrete with different solder thickness under thermal cycling were simulated and the results were merged to conditions of IGBTs in actual environment. The simulation results demonstrated that after thermal cycling, some creep strain is produced in the solder layer especially at the corners. This type of strain is accumulated in the volume of solder as stored energy. Accordingly, the decrease in solder thickness leads to the enhancement of stored energy per volume and as a result, the fatigue life of joint falls to shorter times. The SEM micrographs indicates that with the decrease of solder thickness, the number of voids and their concentration enhance across in the joint zone. The higher strain energy in thinner solder layers leads to the connection of voids and the formation of more concentrated defects. The EDS results also show that the diffusion of elements such as Si, Cu and Ag considerably increases across the joint zone after thermal cycling.
author_names: Aravindhan Surendar

Vahid Samavatian

Andino Maseleno

Aygul Z Ibatova

Majid Samavatian
title: Effect of solder layer thickness on thermo mechanical reliability of a power electronic system
venue: Journal of Materials Science: Materials in Electronics
year: 2018

abstract: Power Semiconductor Devices Key Components for Efficient Electrical Energy Conversion Systems. Semiconductor Properties. pn Junctions. Short introduction to power device technology. pin Diodes. Schottky Diodes. Bipolar Transistors. Thyristors. MOS Transistors. IGBTs. Packaging and Reliability of Power Devices. Destructive Mechanisms in Power Devices. Power Device Induced Oscillations and Electromagnetic Disturbances. Power Electronic Systems. Appendix. Index.
author_names: Josef Lutz

Heinrich Dr Schlangenotto

Uwe Scheuermann

Rik W De Doncker
title: Semiconductor Power Devices: Physics, Characteristics, Reliability
year: 2011

abstract: For decades soldering has been the technology of choice in die bonding. However, due to worldwide health regulations, the most common solder alloys, which contain lead, have been banned. Furthermore, standard solders cannot fulfil the reliability requirements of future power electronic devices. New interconnection technologies have to be developed. One of them is pressure sintering of silver flakes, which forms a highly reliable, highly thermally conductive bond. However, the level of pressure needed (30 50 MPa) requires a powerful pressing equipment and can lead to cracking of the devices and ceramic substrates. A promising development is the use of nano scaled silver particles, which can be sintered using less pressure due to their superior sintering properties. Preceding thermogravimetric and calorimetric analyses showed that the presence of oxygen eases the sintering of silver nanoparticles. In order to grasp the sintering characteristics of interconnection layers consisting of nano scaled silver, sintering experiments were conducted in both air and nitrogen. Scanning electronic microscope pictures and density measurements with a laser profilometer show that sintering of the nano scaled silver in air but under a chip, the case of real interest, is closer to uncovered sintering in nitrogen than in air. Densities remain lower and the microstructures more fine grained. This is due to limitation of diffusion of organics out of and oxygen into the layer. The application of pressure can make up for this in terms of density. Hence, the increase in density of stencil printed layers of nano silver when sintering at temperatures ranging from 200 to 300degC, pressures between 0 and 30 MPa, and for a time of up to 1800 s was measured. The density can be set to any value between 60% and 90% of bulk silver by adjusting sintering time and the levels of temperature and pressure. Samples for shear tests were built using dummy chips made of silver coated copper. They show that after 60 s of sintering at 275degC and 5 MPa a good shear strength of 40 MPa had been established. If the remaining parameters are set correctly, even 5 s of sintering, a temperature of 225degC, or a pressure as low as 2 MPa is sufficient to generate bonds comparable to solder and high pressure sinter joints.
author_names: Matthias Knoerr

Andreas Schletz
title: Power semiconductor joining through sintering of silver nanoparticles: Evaluation of influence of parameters time, temperature and pressure on density, strength and reliability
venue: 2010 6th International Conference on Integrated Power Electronics Systems
year: 2010

abstract: Electronic devices using semiconductors such as insulated gate bipolar transistors, metal oxide semiconductor field effect transistors, and diodes are extensively used in electrical traction applications such as locomotive, elevators, subways, and cars. The long term reliability of such power modules is then highly demanded, and their main reliability criterion is their power cycling capability. Thus, a power cycling test is the most important reliability test for power modules. This test consists in periodically applying a current to a device mounted onto a heat sink. This leads to power loss in the entire module and results in a rise in the semiconductor temperature. In this paper, the different kinds of semiconductors and power modules used for traction applications are described. Experimental and simulation methods employed for power cycling tests are presented. Modules' weak points and fatigue processes are pointed out. Then, a detailed statistical review of publications from 1994 to 2015 dealing with power cycling is presented. This review gives a clear overview of all studies dealing with power cycling that were carried out until now. It reveals the principal trends in power electronic devices and highlights the main reliability issues for which an important lack of knowledge remains.
author_names: C Durand

Markus Klingler

Daniel Coutellier

Hakim Naceur
title: Power Cycling Reliability of Power Module: A Survey
venue: IEEE Transactions on Device and Materials Reliability
year: 2016

abstract: A figure of merit (the Baliga high frequency figure of merit) is derived for power semiconductor devices operating in high frequency circuits. Using this figure of merit, it is predicted that the power losses incurred in the power device will increase as the square root of the operating frequency and approximately in proportion to the output power. By relating the device power dissipation to the intrinsic material parameters, it is shown that the power loss can be reduced by using semiconductors with larger mobility and critical electric field for breakdown. Examination of data in the literature indicates that significant performance improvement can be achieved by replacing silicon with gallium arsenide, silicon carbide, or semiconducting diamond.<ETX>
author_names: B Jayant Baliga
title: Power semiconductor device figure of merit for high frequency applications
venue: IEEE Electron Device Letters
year: 1989

abstract: Low temperature Ag sintering provides a lead free die attachment method that is compatible with high temperature (300 degC) power electronics applications. The reliability of sintered Ag die attach for Si and SiC die has been studied on both thick film substrates for lower current power applications and direct bond copper (DBC) substrates for higher current power applications. Pressureless and low pressure sintering were evaluated. Sintering with low pressure yielded lower porosity (15 17% versus pressureless sintering ~30% Reliability was evaluated with thermal aging (300 degC) and thermal cycling 55 degC to 300 degC) tests. Reliable Ag sintered die attach was achieved with assemblies having Ag bearing surface finishes on both the die and the substrate. In contrast, the shear strength after 300 degC aging was greatly reduced when Au metallization was used either on the die or on substrate surface. In some cases, low pressure sintering delayed the failure of the sintered Ag die attach to Au surfaces when aged at 300 degC compared to the pressureless sintering. The reliability with Pd containing substrate metallizations was intermediate between Ag and Au metallizations. The thermal cycle reliability on DBC substrates was limited by failure at the Cu to alumina interface over the wide temperature range, while on the thick film substrates high adhesion was maintained after 1000 thermal cycles.
author_names: Fang Yu

Jinzi Cui

Zhangming Zhou

Kun Fang

R Wayne Johnson

Michael C Hamilton
title: Reliability of Ag Sintering for Power Semiconductor Die Attach in High Temperature Applications
venue: IEEE Transactions on Power Electronics
year: 2017