Rita Mohanty - Academia.edu (original) (raw)

Papers by Rita Mohanty

IMAPSource Proceedings

Thermal interface material (TIM) is used in between a heat generating component (e.g., microelect... more Thermal interface material (TIM) is used in between a heat generating component (e.g., microelectronic packaging) and a heat spreading component (e.g., heatsink or cooling plate) to create an effective path for the heat (Phonon) to travel. Standard heatsink and heat generating component surfaces are generally uneven and rough. Actual metal to metal contact is no more than 10%. These surface imperfections allow air to get trapped in between the two surfaces. Air, being a thermal insulator, prevents the heat from dissipating and thus the device/system fails to maintain the required operating temperature to meet the reliability and functionality needed. Replacing the air with the “right” thermal interface material is the focus of this research. TIM is a composite of thermally conductive fillers dispersed in a polymer matrix. A higher filler loading causes a higher bulk conductivity. Common practice among design engineers is to utilize output from thermal modelling & simulation to speci...

2009 4th International Microsystems, Packaging, Assembly and Circuits Technology Conference, 2009

The widely recognized industry standard IPC-7525 has been used as the starting point for an exper... more The widely recognized industry standard IPC-7525 has been used as the starting point for an experimental program that explores the effect of varying the keep out distance for 0201 and 0402 chip components, CSP and SOP with pitches down to 0.4mm, and larger components represented by CCGA. Other variables that were included in the experimental program to determine if they had an effect on the sensitivity of paste transfer to keep-out distance included stencil type, step height and solder type. In the first stage of the project the printing to each pad was measured with automated 3D SPI systems and optimum combinations of parameters identified by statistical analysis. In this paper the authors will explain the methodology chosen to achieve the project objectives and indicate the direction of likely future work. Early results indicate that a key objective of the project, to provide evidence to support the case for a reduction in the keep out distances below the current industry standard, might be achievable.

Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced ... more Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced packaging, including MEMS, where lower cost, cavity style packages are required. Thermoplastics, like LCP, PPS and PEEK, can withstand exposure to over 300oC thus assuring lead-free solder capability. Many polymers offer superior moisture resistance, can be formed into micro-precision packages in just seconds, and are easily recycled. Epoxies, the non-hermetic package standard for more than 50 years, can’t be remelted for reuse, have unremarkable moisture properties, and typically contain elements, like bromine, that put them on the environmental target list. Some halogen compounds have already been banned. Fortunately, several modern high-performance halogen-free thermoplastics are inherently flame retardant and these nontoxic materials have an excellent record of use in telecommunications, medical, and automotive fields. This paper will describe advances in thermoplastic packaging prod...

The Surface Mount Technology (SMT) industry has overcome many challenges in the last 30 years, si... more The Surface Mount Technology (SMT) industry has overcome many challenges in the last 30 years, since its introduction in the 1980’s. One recent challenge has been the lead-free assembly. People have been working for more than ten years to address this challenge. While the industry is finally getting a good handle on the lead-free assembly process, another significant challenge has begun to surface. The most current challenge is the adoption of miniature components assembly process. Miniature components used today includes 01005, 0201 passives to 0.3 mm-0.4 mm CSP and BGA. By itself, miniature components have their own challenges, but when combined with larger components on the same board, the challenges multiply by several fold. To make matters worse, the design and functionality demanded by consumers require the placement of miniature passives next to larger, castle-like components. This creates a fundamental challenge in satisfying the solder paste need for both small and large co...

Reflow solder connection of electronic components to a substrate, the apparatus comprising: a ref... more Reflow solder connection of electronic components to a substrate, the apparatus comprising: a reflowing chamber; a conveying device for conveying a substrate into the chamber; at least one heating element to provide heat for melting solder on the substrate, and at least one filtration system for the removal of impurities produced by the Aufschmelzlotmittel, wherein the at least one filtration system coupled to the chamber for the passage of a flow of steam from the chamber through the filtration system, wherein the at least one filtration system comprising a primary unit including a cooling device and a filter device which is arranged adjacent to the cooling device, the cooling device comprises a plurality has cooling fins to cool the vapor stream that enters the primary unit, the arrangement being such that impurities in the vapor stream condense on the cooling fins, when the vapor stream is passed over the cooling fins, and are trapped by the filter device.

Stencil printing is a critical first step in surface mount assembly. It is often cited that the s... more Stencil printing is a critical first step in surface mount assembly. It is often cited that the solder paste printing operation causes about 50%-80% of the defects found in the assembly of PCBs. Printing is widely recognized as a complex process whose optimal performance depends on the adjustment of a substantial number of parameters. It is not uncommon to hear that stencil printing is more of an “art” than “science”. In fact, the process is so complex that sub-optimal print parameters usually end up being used. In addition, stencil printing produce relatively noisy data, which makes the print process extremely difficult to control. Ideally, minimizing the variance of the deposited location and volumes will improve the quality of the process and produce more reliable solder joints. In general, there are two critical aspects to a printing process. The goal of solder paste printing is to put down the right “volume” of paste on the right “spot”. In another words, we not only have to mo...

The solder paste deposition process is viewed by many in the industry as the leading contributor ... more The solder paste deposition process is viewed by many in the industry as the leading contributor of defects in the Surface Mount Technology (SMT) assembly process. As with all manufacturing processes, solder paste printing is subject to both special and common cause variation. Just like using graduated cylinders from distinctly different manufacturing processes to measure a volume of liquid, using different blades types can contribute significant special cause variation to a process. Understanding the significant differences in print performance between blade types is an important first step to establishing a standard blade for an SMT process. Over the last 30 years, the SMT assembly process has become increasingly more sophisticated. There are two primary methods of applying solder paste to a circuit board using a stencil printer: squeegee blade printing and enclosed head printing. While each method has its advantages and disadvantages, this study focuses on the squeegee blade prin...

For some years now, an area ratio of 0.66 or greater has been the criterion for stencil apertures... more For some years now, an area ratio of 0.66 or greater has been the criterion for stencil apertures to achieve acceptable volume control in the printed solder paste “brick,” for small apertures Meeting this criterion, in the stencil printing process, has been a constant concern as the volume consistency of the solder paste brick is among the most critical metrics in determining high yields in the assembly process. With the advent of 0201 and most recently 01005 passives components, meeting the area ratio target of 0.66 is a challenging task; especially with a 5 mil thick stencil and a Type 3 powder solder paste. These tiny passive technologies and minimalist IC packages like 0.4mm CSPs have created a need to re-evaluate the area ratio criterion of 0.66 and other related issues. In light of this need, we developed a series of designed experiments (DOEs) evaluating Type 3 and Type 4 solder pastes, varying aperture designs for 0201, 01005 and 0.4 mm CSPs, and 3 and 4 mil thick laser cut ...

A melting device (10) for solder connection of electronic components to a substrate has a reflow ... more A melting device (10) for solder connection of electronic components to a substrate has a reflow chamber, a conveying device, at least one heating element and at least one system to remove by the Aufschmelzlotmittel (44) produced impurities. The system is coupled to the chamber for the passage of a flow of steam from the chamber through the system. The system has an impurity collecting unit with a pipe coil (88) and a collection container (90). The coil is designed to receive cooled gas therein and condense impurities in the vapor stream on the coil, and if the introduction of cooled gas is terminated in the coil, are released impurities in the vapor stream from the coil and collected in the collection container. Other embodiments for the removal of impurities further disclose another cooling device having a plurality of cooling fins (58) to cool the vapor stream entering into the device. The system for the removal of the impurities also includes a filtration system with a filter (68).

International Symposium on Microelectronics, 2017

In today's high-tech world, we heavily depend on electronics for our health, safety, mobility... more In today's high-tech world, we heavily depend on electronics for our health, safety, mobility and economic welfare. When they fail, the results can be as minor as consumer annoyance to as severe as loss of life. Not to mention a significant financial penalty to the producer in the form of warranty cost. In the electronics industry, especially in the consumer electronics segment, warranty expense cost can be 1% - 2% of the total revenue1. As an example, for a 1Bcompany,thiscanimpactthebottomlineby1B company, this can impact the bottom line by 1Bcompany,thiscanimpactthebottomlineby10M–$20M. For this reason, reducing warranty cost through increased product reliability is not only necessary for survival but also smart. However, achieving product reliability in today's environment with limited development resources and demand for reducing product development cycle time creates a special challenge. In addition, many small to medium size organizations struggle to understand the basic concepts behind reliability engineering, often confusing it with qualit...

Circuits Assembly, Apr 1, 2008

MRS Proceedings, 1994

We have experimentally demonstrated that the interface between ITO and Si or Si0.85Ge0.15 is meta... more We have experimentally demonstrated that the interface between ITO and Si or Si0.85Ge0.15 is metastable, with silicon reducing ITO to form an amorphous oxide layer and In metal. A 400nm-thick ITO layer was deposited on two types of substrates: p-type, <100> silicon wafers and a silicon wafer with a 400nm-thick layer of Si0.85Ge0.15 grown by CVD. Annealing of the ITO/Si system resulted in the growth of a 5nm-thick planar, interfacial SiO2 layer and the formation of In metal in the ITO above the SiO2 layer. In contrast, annealing of the ITO/Si0.85Ge0.15 system produced an interfacial Si0.85Ge0.15O2 layer that was non-uniform in thickness and which had a non-planar surface morphology. As-deposited and annealed samples were characterized by HREM, EDS, and C-V measurements. Thermodynamic and kinetic arguments predicted both of the different reaction paths that were observed in the two systems.

Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced ... more Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced packaging, including MEMS, where lower cost, cavity style packages are required. Thermoplastics, like LCP, PPS and PEEK, can withstand exposure to over 300oC thus assuring lead-free solder capability. Many polymers offer superior moisture resistance, can be formed into micro-precision packages in just seconds, and are easily recycled. Epoxies, the non-hermetic package standard for more than 50 years, can't be remelted for reuse, have unremarkable moisture properties, and typically contain elements, like bromine, that put them on the environmental target list. Some halogen compounds have already been banned. Fortunately, several modern high-performance halogen-free thermoplastics are inherently flame retardant and these nontoxic materials have an excellent record of use in telecommunications, medical, and automotive fields. This paper will describe advances in thermoplastic packaging...

In this rapidly moving electronics market, fast to market with new products is what separates top... more In this rapidly moving electronics market, fast to market with new products is what separates top performing companies from average companies. A survey conducted by Arthur D. Little (ADL)[1]revealed that “New-Product Development (NPD) productivity in atop performing company is five times what it is in the average company. The top performer gets five times as much new product output for the same investment.” What do they know that the rest of us do not? One winning factor is the use of the Robert Cooper process[2]. Since its introduction in the early 1980’s, it has gone through many modifications to make it more lean and effective for today’s business climate. Many larger organizations already practice this method. However, for small to medium size organizations, a dedicated New Product Development (NPD) process may appear to be a daunting task. This is due to the perception of the complexity of the Stage Gate process. This paper will present a Lean Six Sigma approach to “right sizin...

IMAPSource Proceedings

Thermal interface material (TIM) is used in between a heat generating component (e.g., microelect... more Thermal interface material (TIM) is used in between a heat generating component (e.g., microelectronic packaging) and a heat spreading component (e.g., heatsink or cooling plate) to create an effective path for the heat (Phonon) to travel. Standard heatsink and heat generating component surfaces are generally uneven and rough. Actual metal to metal contact is no more than 10%. These surface imperfections allow air to get trapped in between the two surfaces. Air, being a thermal insulator, prevents the heat from dissipating and thus the device/system fails to maintain the required operating temperature to meet the reliability and functionality needed. Replacing the air with the “right” thermal interface material is the focus of this research. TIM is a composite of thermally conductive fillers dispersed in a polymer matrix. A higher filler loading causes a higher bulk conductivity. Common practice among design engineers is to utilize output from thermal modelling & simulation to speci...

2009 4th International Microsystems, Packaging, Assembly and Circuits Technology Conference, 2009

The widely recognized industry standard IPC-7525 has been used as the starting point for an exper... more The widely recognized industry standard IPC-7525 has been used as the starting point for an experimental program that explores the effect of varying the keep out distance for 0201 and 0402 chip components, CSP and SOP with pitches down to 0.4mm, and larger components represented by CCGA. Other variables that were included in the experimental program to determine if they had an effect on the sensitivity of paste transfer to keep-out distance included stencil type, step height and solder type. In the first stage of the project the printing to each pad was measured with automated 3D SPI systems and optimum combinations of parameters identified by statistical analysis. In this paper the authors will explain the methodology chosen to achieve the project objectives and indicate the direction of likely future work. Early results indicate that a key objective of the project, to provide evidence to support the case for a reduction in the keep out distances below the current industry standard, might be achievable.

Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced ... more Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced packaging, including MEMS, where lower cost, cavity style packages are required. Thermoplastics, like LCP, PPS and PEEK, can withstand exposure to over 300oC thus assuring lead-free solder capability. Many polymers offer superior moisture resistance, can be formed into micro-precision packages in just seconds, and are easily recycled. Epoxies, the non-hermetic package standard for more than 50 years, can’t be remelted for reuse, have unremarkable moisture properties, and typically contain elements, like bromine, that put them on the environmental target list. Some halogen compounds have already been banned. Fortunately, several modern high-performance halogen-free thermoplastics are inherently flame retardant and these nontoxic materials have an excellent record of use in telecommunications, medical, and automotive fields. This paper will describe advances in thermoplastic packaging prod...

The Surface Mount Technology (SMT) industry has overcome many challenges in the last 30 years, si... more The Surface Mount Technology (SMT) industry has overcome many challenges in the last 30 years, since its introduction in the 1980’s. One recent challenge has been the lead-free assembly. People have been working for more than ten years to address this challenge. While the industry is finally getting a good handle on the lead-free assembly process, another significant challenge has begun to surface. The most current challenge is the adoption of miniature components assembly process. Miniature components used today includes 01005, 0201 passives to 0.3 mm-0.4 mm CSP and BGA. By itself, miniature components have their own challenges, but when combined with larger components on the same board, the challenges multiply by several fold. To make matters worse, the design and functionality demanded by consumers require the placement of miniature passives next to larger, castle-like components. This creates a fundamental challenge in satisfying the solder paste need for both small and large co...

Reflow solder connection of electronic components to a substrate, the apparatus comprising: a ref... more Reflow solder connection of electronic components to a substrate, the apparatus comprising: a reflowing chamber; a conveying device for conveying a substrate into the chamber; at least one heating element to provide heat for melting solder on the substrate, and at least one filtration system for the removal of impurities produced by the Aufschmelzlotmittel, wherein the at least one filtration system coupled to the chamber for the passage of a flow of steam from the chamber through the filtration system, wherein the at least one filtration system comprising a primary unit including a cooling device and a filter device which is arranged adjacent to the cooling device, the cooling device comprises a plurality has cooling fins to cool the vapor stream that enters the primary unit, the arrangement being such that impurities in the vapor stream condense on the cooling fins, when the vapor stream is passed over the cooling fins, and are trapped by the filter device.

Stencil printing is a critical first step in surface mount assembly. It is often cited that the s... more Stencil printing is a critical first step in surface mount assembly. It is often cited that the solder paste printing operation causes about 50%-80% of the defects found in the assembly of PCBs. Printing is widely recognized as a complex process whose optimal performance depends on the adjustment of a substantial number of parameters. It is not uncommon to hear that stencil printing is more of an “art” than “science”. In fact, the process is so complex that sub-optimal print parameters usually end up being used. In addition, stencil printing produce relatively noisy data, which makes the print process extremely difficult to control. Ideally, minimizing the variance of the deposited location and volumes will improve the quality of the process and produce more reliable solder joints. In general, there are two critical aspects to a printing process. The goal of solder paste printing is to put down the right “volume” of paste on the right “spot”. In another words, we not only have to mo...

The solder paste deposition process is viewed by many in the industry as the leading contributor ... more The solder paste deposition process is viewed by many in the industry as the leading contributor of defects in the Surface Mount Technology (SMT) assembly process. As with all manufacturing processes, solder paste printing is subject to both special and common cause variation. Just like using graduated cylinders from distinctly different manufacturing processes to measure a volume of liquid, using different blades types can contribute significant special cause variation to a process. Understanding the significant differences in print performance between blade types is an important first step to establishing a standard blade for an SMT process. Over the last 30 years, the SMT assembly process has become increasingly more sophisticated. There are two primary methods of applying solder paste to a circuit board using a stencil printer: squeegee blade printing and enclosed head printing. While each method has its advantages and disadvantages, this study focuses on the squeegee blade prin...

For some years now, an area ratio of 0.66 or greater has been the criterion for stencil apertures... more For some years now, an area ratio of 0.66 or greater has been the criterion for stencil apertures to achieve acceptable volume control in the printed solder paste “brick,” for small apertures Meeting this criterion, in the stencil printing process, has been a constant concern as the volume consistency of the solder paste brick is among the most critical metrics in determining high yields in the assembly process. With the advent of 0201 and most recently 01005 passives components, meeting the area ratio target of 0.66 is a challenging task; especially with a 5 mil thick stencil and a Type 3 powder solder paste. These tiny passive technologies and minimalist IC packages like 0.4mm CSPs have created a need to re-evaluate the area ratio criterion of 0.66 and other related issues. In light of this need, we developed a series of designed experiments (DOEs) evaluating Type 3 and Type 4 solder pastes, varying aperture designs for 0201, 01005 and 0.4 mm CSPs, and 3 and 4 mil thick laser cut ...

A melting device (10) for solder connection of electronic components to a substrate has a reflow ... more A melting device (10) for solder connection of electronic components to a substrate has a reflow chamber, a conveying device, at least one heating element and at least one system to remove by the Aufschmelzlotmittel (44) produced impurities. The system is coupled to the chamber for the passage of a flow of steam from the chamber through the system. The system has an impurity collecting unit with a pipe coil (88) and a collection container (90). The coil is designed to receive cooled gas therein and condense impurities in the vapor stream on the coil, and if the introduction of cooled gas is terminated in the coil, are released impurities in the vapor stream from the coil and collected in the collection container. Other embodiments for the removal of impurities further disclose another cooling device having a plurality of cooling fins (58) to cool the vapor stream entering into the device. The system for the removal of the impurities also includes a filtration system with a filter (68).

International Symposium on Microelectronics, 2017

In today's high-tech world, we heavily depend on electronics for our health, safety, mobility... more In today's high-tech world, we heavily depend on electronics for our health, safety, mobility and economic welfare. When they fail, the results can be as minor as consumer annoyance to as severe as loss of life. Not to mention a significant financial penalty to the producer in the form of warranty cost. In the electronics industry, especially in the consumer electronics segment, warranty expense cost can be 1% - 2% of the total revenue1. As an example, for a 1Bcompany,thiscanimpactthebottomlineby1B company, this can impact the bottom line by 1Bcompany,thiscanimpactthebottomlineby10M–$20M. For this reason, reducing warranty cost through increased product reliability is not only necessary for survival but also smart. However, achieving product reliability in today's environment with limited development resources and demand for reducing product development cycle time creates a special challenge. In addition, many small to medium size organizations struggle to understand the basic concepts behind reliability engineering, often confusing it with qualit...

Circuits Assembly, Apr 1, 2008

MRS Proceedings, 1994

We have experimentally demonstrated that the interface between ITO and Si or Si0.85Ge0.15 is meta... more We have experimentally demonstrated that the interface between ITO and Si or Si0.85Ge0.15 is metastable, with silicon reducing ITO to form an amorphous oxide layer and In metal. A 400nm-thick ITO layer was deposited on two types of substrates: p-type, <100> silicon wafers and a silicon wafer with a 400nm-thick layer of Si0.85Ge0.15 grown by CVD. Annealing of the ITO/Si system resulted in the growth of a 5nm-thick planar, interfacial SiO2 layer and the formation of In metal in the ITO above the SiO2 layer. In contrast, annealing of the ITO/Si0.85Ge0.15 system produced an interfacial Si0.85Ge0.15O2 layer that was non-uniform in thickness and which had a non-planar surface morphology. As-deposited and annealed samples were characterized by HREM, EDS, and C-V measurements. Thermodynamic and kinetic arguments predicted both of the different reaction paths that were observed in the two systems.

Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced ... more Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced packaging, including MEMS, where lower cost, cavity style packages are required. Thermoplastics, like LCP, PPS and PEEK, can withstand exposure to over 300oC thus assuring lead-free solder capability. Many polymers offer superior moisture resistance, can be formed into micro-precision packages in just seconds, and are easily recycled. Epoxies, the non-hermetic package standard for more than 50 years, can't be remelted for reuse, have unremarkable moisture properties, and typically contain elements, like bromine, that put them on the environmental target list. Some halogen compounds have already been banned. Fortunately, several modern high-performance halogen-free thermoplastics are inherently flame retardant and these nontoxic materials have an excellent record of use in telecommunications, medical, and automotive fields. This paper will describe advances in thermoplastic packaging...

In this rapidly moving electronics market, fast to market with new products is what separates top... more In this rapidly moving electronics market, fast to market with new products is what separates top performing companies from average companies. A survey conducted by Arthur D. Little (ADL)[1]revealed that “New-Product Development (NPD) productivity in atop performing company is five times what it is in the average company. The top performer gets five times as much new product output for the same investment.” What do they know that the rest of us do not? One winning factor is the use of the Robert Cooper process[2]. Since its introduction in the early 1980’s, it has gone through many modifications to make it more lean and effective for today’s business climate. Many larger organizations already practice this method. However, for small to medium size organizations, a dedicated New Product Development (NPD) process may appear to be a daunting task. This is due to the perception of the complexity of the Stage Gate process. This paper will present a Lean Six Sigma approach to “right sizin...