A cost optimisation study of the tin alloy-coated copper ribbons soldered onto the screen-printed... more A cost optimisation study of the tin alloy-coated copper ribbons soldered onto the screen-printed busbars of the crystalline silicon solar cell was performed. The electrical loss, the material cost and the cost for the inactive area, i.e. metal-covered area and the area between the cells, were optimised for a number of different parameters. The electricity loss was valued equal to the cost to produce electricity from a solar module. The optimum number of ribbons per solar cell (156 x 156 mm) was six ribbons in this study. Increased number of ribbons per cell from three (standard today) to six will also enable industrial screen/stencil printing of 40 μm wide and 4 μm thick fingers while reducing the amount of silver by 50%. Further cost reduction can be achieved when the width of the solar cell is included in the optimisation. A reduced width of the solar cell from 156 mm to 39 mm results in a reduction of the optimal cross-section area of the ribbons by 65 %, which will reduce significantly the mechanical stress on the silicon cell and the shadowing of the solar cell.
L'invention concerne un rail de jonction concu pour connecter electriquement les photodiodes ... more L'invention concerne un rail de jonction concu pour connecter electriquement les photodiodes dans un module solaire. Le rail de jonction se compose de deux rangees de segments conducteurs qui sont juxtaposees. En outre, lesdits segments sont isoles electriquement entre eux. Dans un autre mode de realisation du rail de jonction, une ou plusieurs diodes ou un ou plusieurs relais montes en antiparallele, de preference des relais MEMS, et un circuit d'attaque sont places entre les segments afin de court-circuiter une cellule solaire a l'ombre. La longueur d'un segment est concue pour chainer deux photodiodes, ou encore deux groupes de photodiodes montees en parallele. Les deux rangees de segments sont decalees en fonction de l'ecartement des deux photodiodes montees en serie ou des deux groupes montes en serie de photodiodes montees en parallele. Les conducteurs electriques sont fixes, de preference soudes, sur la photodiode et sont connectes aux deux extremites a de...
2017 IEEE International Workshop On Integrated Power Packaging (IWIPP), 2017
In typical press-pack, free-floating packages the thermal contact resistance between chip and sub... more In typical press-pack, free-floating packages the thermal contact resistance between chip and substrate is a major limiting factor for the cooling ability of the power module. We report an introduction of a new, thin Silver interlayer between Molybdenum substrate and chip, and how it improves the thermal contact. The thermal contact resistances were measured with and without a Silver interlayer at different pressures. The surface roughness of the SiC chip and the Molybdenum substrate were characterized. The thermal contact resistances were measured at three different heating power levels. The results show a significant reduction of the thermal contact resistance with only a few micrometer Silver interlayer. The improved cooling effect of a Silver interlayer was also demonstrated with a fluid dynamics type of 3 D simulation comparing temperature distributions with and without a Silver interlayer. These results project a possible thermal improvement in press-pack packages.
2018 IEEE Holm Conference on Electrical Contacts, 2018
Corrosion tests, fretting tests and other environmental endurance tests are performed to provide ... more Corrosion tests, fretting tests and other environmental endurance tests are performed to provide information on performance in use or to demonstrate compliance with standards or specifications. In this paper, pitfalls concerning the use of tests to predict the durability of electrical connectors in the field are discussed. The discussion covers corrosion testing resulting in unrealistic chemistries, fretting tests concentrating on incorrect failure mechanisms, self-healing effects during testing resulting in misleading results, as well as lack of evaluation of effects of testing, such as contact resistance measurements under conditions not revealing surface films formed. Testing under unrealistic conditions or without proper evaluation of results may not only risk not detecting a poor design but also to reject a good one.
The introduction of SiC power devices for automotive applications requires new design of the modu... more The introduction of SiC power devices for automotive applications requires new design of the module in order to utilise the full erformance. The commercial SiC components available today utilises p ...
Wear in forming tools and contact problems between sheet-metal and tool-material are common probl... more Wear in forming tools and contact problems between sheet-metal and tool-material are common problems in manufacturing industries and sheet-metal-parts production. In this paper recent tool material experiences are presented. Quantitative determination of wear has been performed using micro hardness indentions made on the tool surface prior to pressings and thereafter measured. Wear tests are performed with both model tools in a wear test press and in one case study. It is shown in this paper that: VANCRON shows equally good anti-galling properties as VANADIS 4 with TICRON treatment in model tools. VANCRON was successfully used in a production tool (case study) for 1,000,000 pressings without galling problems. The wear is small and production can continue further. VANADIS 4 with TICRON treatment in the same application is recoated before 1,000,000 parts. The method of using micro hardness indentions appears to be a promising way to quantitatively determine wear depths on tool surface...
A comparison between flexforming and conventional forming : A study of semi-industrial components... more A comparison between flexforming and conventional forming : A study of semi-industrial components and real production parts
The purpose of the present work is to compare flexform technique (die-forming) with conventional ... more The purpose of the present work is to compare flexform technique (die-forming) with conventional pressing technique by analyzing the strain state of the components after forming. A double curved co ...
IEEE Transactions on Components, Packaging and Manufacturing Technology, 2019
This paper proposes a novel power module concept specially designed for highly reliable silicon c... more This paper proposes a novel power module concept specially designed for highly reliable silicon carbide power devices for medium-and high-power applications. The concept consists of two clamped structures: 1) a press-pack power stage accommodating silicon carbide power switch dies, and 2) perpendicularly clamped press-pack heatsinks, in which, the heatsinks are in contact with electrically insulated case plates of the power stage. The concept enables bondless package with symmetric double-sided cooling of the dies and allows for an order of magnitude higher clamping force on the heatsinks than what can be applied on the dies. The concept has been evaluated in a first demonstrator (half-bridge configuration with ten paralleled silicon carbide dies in each position). Experimental methodologies, setups, and procedures have been presented. The commutation loop inductance is approximately 9 nH at 78 kHz. The junction-to-case thermal resistance is approximately 0.028 K/W. Furthermore, a simplified 3D finite element thermomechanical model representing the center unit of the demonstrator, has been established for the purpose of future optimization. The accuracy of the simulated temperatures is within 4 % compared to the measurements. Finally, a 3D thermomechanical stress distribution map has been obtained for the simplified model of the demonstrator.
Holm Conference on Electrical Contacts, Sep 16, 1996
... Tag Hammam Swedish Institute for Metals Research Drottning Kristinas v 48 S-II 4 28 Stockhol... more ... Tag Hammam Swedish Institute for Metals Research Drottning Kristinas v 48 S-II 4 28 Stockholm, Sweden ... 1 The tested model contact consists of two parts: one flat stationary sample, and one moving hemisphere with a tip radius of 2mm called rider in the following text. ...
IEEE Transactions on Components, Packaging and Manufacturing Technology, 2017
This paper presents an experimental methodology for the characterization of thermomechanical disp... more This paper presents an experimental methodology for the characterization of thermomechanical displacement and friction properties in a free-floating press-pack structure, and evaluation of the tensile stress on the semiconductor die through simulation of different mechanical and thermal loading conditions. The press-pack structure consists of a single silvermetallized (1 µm) silicon carbide die (400 µm) in contact with rhodium-coated (0.4 µm) molybdenum square plates. The thermomechanical displacements in the press-pack structure have been obtained using the digital image correlation technique, and the mean random error has been ±0.1 µm, which is approximately 10 ppm of the measured length (10.5 mm). The developed experimental method has led to an analytical estimation of friction coefficients on the interfaces' silicon carbidemolybdenum and molybdenum-copper. The results demonstrate that the thin silver layer behaves as a solid film lubricant. A 2-D finite-element model representing the experimental setup has been implemented. The difference in displacement between measurement and simulation is less than 8%. Furthermore, the coinfluence of the design parameters on the thermomechanical performance of the stacked structure has been analyzed through simulations. Finally, design guidelines to reduce the tensile stress on the silicon carbide die have been proposed regarding free-floating press-pack power electronics packaging.
... FRETTING BENCH-TEST Tag Hammam KIMAB Stockholm, Sweden tag.hammam@kimab. com ... Mode III Cir... more ... FRETTING BENCH-TEST Tag Hammam KIMAB Stockholm, Sweden tag.hammam@kimab. com ... Mode III Circumferential relative displacement Figure 1. Schematic figure of the three basic fretting modes in the case of ball-on-flat contact geometry [6]. ...
A cost optimisation study of the tin alloy-coated copper ribbons soldered onto the screen-printed... more A cost optimisation study of the tin alloy-coated copper ribbons soldered onto the screen-printed busbars of the crystalline silicon solar cell was performed. The electrical loss, the material cost and the cost for the inactive area, i.e. metal-covered area and the area between the cells, were optimised for a number of different parameters. The electricity loss was valued equal to the cost to produce electricity from a solar module. The optimum number of ribbons per solar cell (156 x 156 mm) was six ribbons in this study. Increased number of ribbons per cell from three (standard today) to six will also enable industrial screen/stencil printing of 40 μm wide and 4 μm thick fingers while reducing the amount of silver by 50%. Further cost reduction can be achieved when the width of the solar cell is included in the optimisation. A reduced width of the solar cell from 156 mm to 39 mm results in a reduction of the optimal cross-section area of the ribbons by 65 %, which will reduce significantly the mechanical stress on the silicon cell and the shadowing of the solar cell.
L'invention concerne un rail de jonction concu pour connecter electriquement les photodiodes ... more L'invention concerne un rail de jonction concu pour connecter electriquement les photodiodes dans un module solaire. Le rail de jonction se compose de deux rangees de segments conducteurs qui sont juxtaposees. En outre, lesdits segments sont isoles electriquement entre eux. Dans un autre mode de realisation du rail de jonction, une ou plusieurs diodes ou un ou plusieurs relais montes en antiparallele, de preference des relais MEMS, et un circuit d'attaque sont places entre les segments afin de court-circuiter une cellule solaire a l'ombre. La longueur d'un segment est concue pour chainer deux photodiodes, ou encore deux groupes de photodiodes montees en parallele. Les deux rangees de segments sont decalees en fonction de l'ecartement des deux photodiodes montees en serie ou des deux groupes montes en serie de photodiodes montees en parallele. Les conducteurs electriques sont fixes, de preference soudes, sur la photodiode et sont connectes aux deux extremites a de...
2017 IEEE International Workshop On Integrated Power Packaging (IWIPP), 2017
In typical press-pack, free-floating packages the thermal contact resistance between chip and sub... more In typical press-pack, free-floating packages the thermal contact resistance between chip and substrate is a major limiting factor for the cooling ability of the power module. We report an introduction of a new, thin Silver interlayer between Molybdenum substrate and chip, and how it improves the thermal contact. The thermal contact resistances were measured with and without a Silver interlayer at different pressures. The surface roughness of the SiC chip and the Molybdenum substrate were characterized. The thermal contact resistances were measured at three different heating power levels. The results show a significant reduction of the thermal contact resistance with only a few micrometer Silver interlayer. The improved cooling effect of a Silver interlayer was also demonstrated with a fluid dynamics type of 3 D simulation comparing temperature distributions with and without a Silver interlayer. These results project a possible thermal improvement in press-pack packages.
2018 IEEE Holm Conference on Electrical Contacts, 2018
Corrosion tests, fretting tests and other environmental endurance tests are performed to provide ... more Corrosion tests, fretting tests and other environmental endurance tests are performed to provide information on performance in use or to demonstrate compliance with standards or specifications. In this paper, pitfalls concerning the use of tests to predict the durability of electrical connectors in the field are discussed. The discussion covers corrosion testing resulting in unrealistic chemistries, fretting tests concentrating on incorrect failure mechanisms, self-healing effects during testing resulting in misleading results, as well as lack of evaluation of effects of testing, such as contact resistance measurements under conditions not revealing surface films formed. Testing under unrealistic conditions or without proper evaluation of results may not only risk not detecting a poor design but also to reject a good one.
The introduction of SiC power devices for automotive applications requires new design of the modu... more The introduction of SiC power devices for automotive applications requires new design of the module in order to utilise the full erformance. The commercial SiC components available today utilises p ...
Wear in forming tools and contact problems between sheet-metal and tool-material are common probl... more Wear in forming tools and contact problems between sheet-metal and tool-material are common problems in manufacturing industries and sheet-metal-parts production. In this paper recent tool material experiences are presented. Quantitative determination of wear has been performed using micro hardness indentions made on the tool surface prior to pressings and thereafter measured. Wear tests are performed with both model tools in a wear test press and in one case study. It is shown in this paper that: VANCRON shows equally good anti-galling properties as VANADIS 4 with TICRON treatment in model tools. VANCRON was successfully used in a production tool (case study) for 1,000,000 pressings without galling problems. The wear is small and production can continue further. VANADIS 4 with TICRON treatment in the same application is recoated before 1,000,000 parts. The method of using micro hardness indentions appears to be a promising way to quantitatively determine wear depths on tool surface...
A comparison between flexforming and conventional forming : A study of semi-industrial components... more A comparison between flexforming and conventional forming : A study of semi-industrial components and real production parts
The purpose of the present work is to compare flexform technique (die-forming) with conventional ... more The purpose of the present work is to compare flexform technique (die-forming) with conventional pressing technique by analyzing the strain state of the components after forming. A double curved co ...
IEEE Transactions on Components, Packaging and Manufacturing Technology, 2019
This paper proposes a novel power module concept specially designed for highly reliable silicon c... more This paper proposes a novel power module concept specially designed for highly reliable silicon carbide power devices for medium-and high-power applications. The concept consists of two clamped structures: 1) a press-pack power stage accommodating silicon carbide power switch dies, and 2) perpendicularly clamped press-pack heatsinks, in which, the heatsinks are in contact with electrically insulated case plates of the power stage. The concept enables bondless package with symmetric double-sided cooling of the dies and allows for an order of magnitude higher clamping force on the heatsinks than what can be applied on the dies. The concept has been evaluated in a first demonstrator (half-bridge configuration with ten paralleled silicon carbide dies in each position). Experimental methodologies, setups, and procedures have been presented. The commutation loop inductance is approximately 9 nH at 78 kHz. The junction-to-case thermal resistance is approximately 0.028 K/W. Furthermore, a simplified 3D finite element thermomechanical model representing the center unit of the demonstrator, has been established for the purpose of future optimization. The accuracy of the simulated temperatures is within 4 % compared to the measurements. Finally, a 3D thermomechanical stress distribution map has been obtained for the simplified model of the demonstrator.
Holm Conference on Electrical Contacts, Sep 16, 1996
... Tag Hammam Swedish Institute for Metals Research Drottning Kristinas v 48 S-II 4 28 Stockhol... more ... Tag Hammam Swedish Institute for Metals Research Drottning Kristinas v 48 S-II 4 28 Stockholm, Sweden ... 1 The tested model contact consists of two parts: one flat stationary sample, and one moving hemisphere with a tip radius of 2mm called rider in the following text. ...
IEEE Transactions on Components, Packaging and Manufacturing Technology, 2017
This paper presents an experimental methodology for the characterization of thermomechanical disp... more This paper presents an experimental methodology for the characterization of thermomechanical displacement and friction properties in a free-floating press-pack structure, and evaluation of the tensile stress on the semiconductor die through simulation of different mechanical and thermal loading conditions. The press-pack structure consists of a single silvermetallized (1 µm) silicon carbide die (400 µm) in contact with rhodium-coated (0.4 µm) molybdenum square plates. The thermomechanical displacements in the press-pack structure have been obtained using the digital image correlation technique, and the mean random error has been ±0.1 µm, which is approximately 10 ppm of the measured length (10.5 mm). The developed experimental method has led to an analytical estimation of friction coefficients on the interfaces' silicon carbidemolybdenum and molybdenum-copper. The results demonstrate that the thin silver layer behaves as a solid film lubricant. A 2-D finite-element model representing the experimental setup has been implemented. The difference in displacement between measurement and simulation is less than 8%. Furthermore, the coinfluence of the design parameters on the thermomechanical performance of the stacked structure has been analyzed through simulations. Finally, design guidelines to reduce the tensile stress on the silicon carbide die have been proposed regarding free-floating press-pack power electronics packaging.
... FRETTING BENCH-TEST Tag Hammam KIMAB Stockholm, Sweden tag.hammam@kimab. com ... Mode III Cir... more ... FRETTING BENCH-TEST Tag Hammam KIMAB Stockholm, Sweden tag.hammam@kimab. com ... Mode III Circumferential relative displacement Figure 1. Schematic figure of the three basic fretting modes in the case of ball-on-flat contact geometry [6]. ...
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