rus
Issue #5/2016
A.Kondrashin, A.Lyamin, V.Sleptsov
4D-technologies for production of three-dimensional integrated circuits
4D-technologies for production of three-dimensional integrated circuits
The third part of the paper is dedicated to analyses the state and prospects of development of 3D MID technology.
Теги: 3d mid technologies 3d-mid-технологии 3d-photoimaging 3d фотолитография jet sputtering laser direct structuring лазерное структурирование струйное распыление
Interest in the 3D-MID technology, which has grown in recent years, led to the development of appropriate technologies and equipment. With the use of 3D-MID are already available or ready for serial production devices with up-to-date element base: leds, unpacked chips, integrated circuits with tabs etc.
4. ANALYSIS OF STATE
IN 3D MID-TECHNOLOGIES
Products based on the 3D-MID technology are currently used in the following areas (Fig.1):
Antennas for mobile and telecommunication devices, such as phones, smartphones, PDAs etc. For example, with use of 3D-MID technology antenna for mobile communication networks (GSM, LTE), radio data transmission (Bluetooth and Wi-Fi) and satellite navigation systems (GPS, GLONASS) can be manufactured on one compact base;
Automotive electronics. Interest in 3D-MID technology in this area is associated with a constant increase in the number of electronic components in vehicles, which are subject to more stringent requirements from reduction of the number of parts (cables, connectors, etc.) to reduction of the cost, acceleration and simplification of assembly, improving reliability;
Medical equipment, for example, in the manufacture of hearing aids, devices for the early detection of caries, pacemakers, artificial kidney apparatus, etc. Replacement of traditional printed circuit boards in medical equipment can significantly reduce its size, simplify the design, to abandon the use of cables and to extend the functionality;
Means of radio frequency identification (RFID/NFC tag) containing an antenna and a chip in which data is stored. RFID is a system for unidirectional communication in which the data is transmitted from the tag to the contactless reader. In NFC (Near Field Communication) to the read function, which duplicates the RFID technology, the two modes are added, which provide dynamic bidirectional communication between the tags for read and write. The first mode is "NFC card emulation" (recording the information on a smart card or other compatible device and read from these devices). The second mode is P2P (peer to peer), where smartphones and other NFC-enabled devices come into radio communication and each node (peer) is both a client and performs the functions of the server. Radius of action of NFC does not exceed 10 cm, which is much smaller than that of the RFID technology. Predicted sales of only RFID/NFC tags will grow by 2020 more than twice (tab.1).
In Russia attention is paid to the development and introduction of new types of 3D-MID technology. In particular, in 2015, a basic technology of multichip assembly of super large scale integration circuits based on the methods of 3D integration called "Krutizna" was developed [2]. This technology is intended for creation of a miniature on-board modules for compute and control devices for aerospace. According to experts, only due to reduction of the length of electrical connections, the introduction of this technology allows to reduce the size of the device and its weight and dimensions by 3–4 times.
Active introduction of 3D MID technology in the manufacture of electronic products is caused by their following advantages in comparison with traditional technologies:
miniaturization of products (reduction in mass and linear dimensions) due to the optimal use of three-dimensional space: of an internal or external load-bearing structural surfaces, and volumes of end-products;
an increase in the degree of integration of printed circuit boards by reducing the space occupied by paths, pads, etc.;
high design flexibility thanks to the use of substrates of various shapes and sizes;
increased reliability of end product due to the exclusion of external components (cables, connectors, etc.);
reduction of consumption of materials for production;
increased production volumes of finished products due to parallel execution of operations of assembly and packaging;
wide range of materials for bases (substrates) and functional layers.
A comparative analysis of capabilities of different 3D MID-technologies in manufacturing of three-dimensional electronic devices (Fig.2) revealed that from the point of view of resolution of the images (minimum size of the structure element) the use of jet sputtering, aerosol jet, laser direct structuring and 3D photolithography is preferably (Fig.2a).
In terms of possible thickness of formed per cycle functional layers (Fig.2b), 3D MID-technologies can be divided into three groups:
thermo-active technologies with the thickness of layers from 100 to 200 microns (insert molding and two step molding);
thick-film technologies with the thickness of layers from 10 to 200 microns (laser structuring and 3D photolithography);
thin-film technologies with the thickness of layers less than 10 microns.
Depending on the speed of formation of the functional layers during one cycle (Fig.2c), technologies can be divided into two groups:
volume forming technologies with the speed of the formation of structures from 0.5 to 60 mm/min (insert molding and two step molding);
film technologies with the speed of the formation of structures of less than 0.5 mm/min.
From the point of view of the range of the used materials (table.2) all currently known technologies can be divided into the following groups:
"versatile" technologies that enables deposition of almost any material to almost any kind of substrates without restrictions on the types of materials and structures. This group includes plasma technologies of atmospheric pressure (flamecon and plasma dust);
"specialized" technologies that can be divided into technologies of "free substrate", which allows to use almost any type of substrates without restrictions on the types of materials and structures (jet sputtering and aerosol jet), and technologies of "free functional", which allows to use virtually any type of functional materials or even devices with certain types of substrates (insert molding);
"highly specialized" technologies, which use only certain types of functional materials associated with a particular type of substrate (two step molding, laser structuring and 3D photolithography).
Thus, the choice of a particular 3D MID-technology is determined by the parameters of products, materials and production volume.
Of course, the 3D-MID technologies have a number of disadvantages, as it does not solve several basic problems associated with the formation of 4D-elements of TEU:
need to use materials of TEU that can withstand a sufficiently high temperature during soldering (up to 260°C), so the widespread introduction of 3D MID-technology is limited by high cost of operating and supporting materials;
need to use at least two different processes and route cards, that is, the inability to create a TEU in a single technological cycle;
difficulties with the mounting of electronic components to the substrate, which requires precision three-dimensional system of electronic assembly on several axes with complex optical systems;
impossibility of making a full-fledged 4D-parts of TEU using as functional elements of all free faces, edges, and volume (or the entire thickness of the walls).
Based on a comparative analysis of different methods of creating a quasi-4D products using the 3D-MID technology it can be concluded that the following solutions are necessary for their further development and introduction into production:
systems of high performance multi-function facilities, allowing in the same industrial building (premises), to obtain the finished product, using entirely different technologies (from laser structuring to the galvanic deposition of metals) combined in a single technological process;
system of high-performance hybrid equipment, which allow to combine several different methods of processing or deposition of various types of materials in a single method. For example, to increase productivity and expand the range of materials that are deposited by aerosol jet it is necessary to create installations with a matrix of heads (nozzles) with an independent supply system (injection) of materials. Such a matrix should allow high-speed deposition of one material and the deposition of various types of materials, for example, with different melting point;
networks of continuous control of product parameters with use of camera systems, sensors, 3D scanners for non-destructive testing,which allows to carry out the culling of products at all stages of production, including the earliest;
wired and wireless connection of sensors and blocks to automated control system;
new principles of formation of functional structures and materials, particularly for manufacture in micron and submicron ranges.
5. PROSPECTS OF DEVELOPMENT OF 3D TECHNOLOGIES FOR TEU
The ultimate goal of the development of modern 3D technology is the development of industrial solutions, allowing to create 4D objects of TEU (table.2). But this goal is too complicated to implement in one generation of technology, so, from our point of view, it is appropriate to highlight the main challenges of the current stage of development:
creation of "hollow" 4D objects of TEU on the basis of cases of elements;
creation of a "monolithic" three-dimensional IC with their subsequent installation into the "hollow" 3D cases of TEU (for example, made using the 3D-MID technology);
creation of a "monolithic" three-dimensional integrated devices.
Since these tasks can be solved in parallel, it is necessary to introduce the concept of "generations" (Fig.3) in the classification of TEU.
4D-objects of the first generation are formed layer by layer using only the wall thickness of structural elements as functional elements. For example, the entire volume of the case of the electronic device can be used for the formation of the conductor layers and electrical circuits consisting of discrete resistors, capacitors, etc.
In uncased 4D-objects of the second generation the layer-by-layer formation of a monolithic three-dimensional integrated circuits (3D IC), consisting of interconnected layers of electrical conductors and circuits that include integrated resistors, capacitors, etc. is implemented. Subsequent operation of manufacture of a TEU is a encapsulation of monolithic 3D IC and their subsequent wiring.
For monolithic 4D-objects of the second generation is typical the layer-by-layer formation of three-dimensional devices consisting of a "built-in" external protective case with the corresponding external connections and of monolithic 3D IC on the basis of both integral and discrete resistors, capacitors, etc.
4D objects of the third generation are packaged and unpackaged plastic (flexible) devices consisting of several interconnected plastic objects. For example, shockproof mobile phone, includes the following components:
flexible multilayer printed motherboard manufactured with use of technology of unpackaged 4D-objects of the second generation;
multilayer ultrathin (about 1 mm) plastic flexible polymer display, obtained according to the OLED or PLED technology [3, 4], which is characterized by low power consumption, high resolution (UHD 4K or 8K), high dynamic contrast and wide color gamut;
environmentally friendly ultra-capacious flexible polymer power source (battery) [5];
flexible plastic case [6].
As an example of 4D-object of the second generation it is possible to compare standalone VHF-transmitters, one of which is made by up-to-date technology of printed circuit boards with components mounted on the surface, and another is made using promising technology, based on 3D tracing.
The device (Fig.4) consists of three VT-bipolar transistors, 11 capacitors, five resistors, two inductors, microphone, antenna and battery. The generator of the RF signal is assembled at the base of the VT2 transistor using the known three-point scheme. Circuit is tuned to the frequency of 96±5 MHz. Currently, this electrical circuit mounted on a printed circuit board using SMD components, has overall dimensions of 15 × 25 × 15 mm (Fig.5).
The design of the device in SolidWorks using the 3D tracing of the object with replacing a part of the circuitry (Fig.6), testifies to a possibility of manufacture of this device with dimensions 6 × 6 × 5 mm, that is reduction of his size by 30 times.
Comparative analysis of modern (mid-2016) technologies for creating 4D objects of TEU (table.3) allows to draw three main conclusions.
First, currently are developed only certain 3D manufacturing technologies of TEU, which are essentially allowing to obtain the integral structure of micron range. So, for example, by insert molding it is possible to manufacture a quasi 3D or 4D functional cell of products and further, using laser structuring and galvanic deposition, it is possible to create a passive part of the product.
Second, none of the existing technologies allows to create integrated single-level and multilevel quasi-4D objects of TEU in a single cycle, therefore, the immediate prospect of development is associated with the integration of different types of technologies in a single production line. It is necessary to develop equipment that meets the following requirements:
TEU should be made on the basis of three-dimensional computer models created by CAD tools;
the elements of the electronic circuit should be formed by different blocks of functional heads on all the free edges (possibly simultaneously) and in volume (or across the wall thickness) of the product;
creation of the TEU should occur in a continuous process cycle in a single 3D robotic system;
manufacture or installation of both passive and active elements and lines of interconnects;
system must be compatible with the manufactured functional materials (paints, inks) used in printed electronics to create conductors and active and passive elements.
As an example of one of the first steps towards the creation of manufacturing technologies of integrated single-level and multilevel quasi-4D objects of TEU it is possible to consider the existing hybrid technology, which allows to combine the installation of discrete electronic components and the creation of conductive layers [7, 8]. Using this technology the wing for the UAV with integrated printed electronic circuit composed of the discrete sensor (or chips) and conductive metal tracks, which works as antennas and power supply, was manufactured. Polymer extrusion (FDM, a 3D printing technology), has been used to create the carrier. Hybrid technology combined extrusion of molten metal for forming the circuit elements and conductors [7] and 3D-MID method of aerosol jet [8].
The third conclusion is that the long-term perspective of creating 4D objects of TEU should be linked to the development of fundamentally new technologies.
The main limiting factors in the production of new objects of TEU is a need to develop technologies and equipment, providing reduction of size and increase in the degree of integration of elements. That is, the development of new technology should be associated, primarily, with the increased resolution of the basic method based on a certain physical principle. Thus, upon transition to the submicron range the analysis of existing methods of miniaturization (creation of semiconductor TEU of appropriate dimensions) showed a significant reduction in the number of possible physical principles of TEU (Fig.7). One of solutions to this problem is the widespread introduction of group methods of functional electronics, providing a fundamental replacement of the basic methods of design of TEU and the creation of new element base. For example, instead of conductive metal interconnects (paths) it is possible to use optical waveguides, and lasers of various types as signal generators. ■
This article concludes a series of papers (see: Nanoindustry, 2016, Vol.3 (65), P. 90–96 and Nanoindustry, 2016, Vol.4 (66), P. 60–77), published in the framework of the Federal target program "Development of electronic component base for electronics", project N 14.429.11.0004.
4. ANALYSIS OF STATE
IN 3D MID-TECHNOLOGIES
Products based on the 3D-MID technology are currently used in the following areas (Fig.1):
Antennas for mobile and telecommunication devices, such as phones, smartphones, PDAs etc. For example, with use of 3D-MID technology antenna for mobile communication networks (GSM, LTE), radio data transmission (Bluetooth and Wi-Fi) and satellite navigation systems (GPS, GLONASS) can be manufactured on one compact base;
Automotive electronics. Interest in 3D-MID technology in this area is associated with a constant increase in the number of electronic components in vehicles, which are subject to more stringent requirements from reduction of the number of parts (cables, connectors, etc.) to reduction of the cost, acceleration and simplification of assembly, improving reliability;
Medical equipment, for example, in the manufacture of hearing aids, devices for the early detection of caries, pacemakers, artificial kidney apparatus, etc. Replacement of traditional printed circuit boards in medical equipment can significantly reduce its size, simplify the design, to abandon the use of cables and to extend the functionality;
Means of radio frequency identification (RFID/NFC tag) containing an antenna and a chip in which data is stored. RFID is a system for unidirectional communication in which the data is transmitted from the tag to the contactless reader. In NFC (Near Field Communication) to the read function, which duplicates the RFID technology, the two modes are added, which provide dynamic bidirectional communication between the tags for read and write. The first mode is "NFC card emulation" (recording the information on a smart card or other compatible device and read from these devices). The second mode is P2P (peer to peer), where smartphones and other NFC-enabled devices come into radio communication and each node (peer) is both a client and performs the functions of the server. Radius of action of NFC does not exceed 10 cm, which is much smaller than that of the RFID technology. Predicted sales of only RFID/NFC tags will grow by 2020 more than twice (tab.1).
In Russia attention is paid to the development and introduction of new types of 3D-MID technology. In particular, in 2015, a basic technology of multichip assembly of super large scale integration circuits based on the methods of 3D integration called "Krutizna" was developed [2]. This technology is intended for creation of a miniature on-board modules for compute and control devices for aerospace. According to experts, only due to reduction of the length of electrical connections, the introduction of this technology allows to reduce the size of the device and its weight and dimensions by 3–4 times.
Active introduction of 3D MID technology in the manufacture of electronic products is caused by their following advantages in comparison with traditional technologies:
miniaturization of products (reduction in mass and linear dimensions) due to the optimal use of three-dimensional space: of an internal or external load-bearing structural surfaces, and volumes of end-products;
an increase in the degree of integration of printed circuit boards by reducing the space occupied by paths, pads, etc.;
high design flexibility thanks to the use of substrates of various shapes and sizes;
increased reliability of end product due to the exclusion of external components (cables, connectors, etc.);
reduction of consumption of materials for production;
increased production volumes of finished products due to parallel execution of operations of assembly and packaging;
wide range of materials for bases (substrates) and functional layers.
A comparative analysis of capabilities of different 3D MID-technologies in manufacturing of three-dimensional electronic devices (Fig.2) revealed that from the point of view of resolution of the images (minimum size of the structure element) the use of jet sputtering, aerosol jet, laser direct structuring and 3D photolithography is preferably (Fig.2a).
In terms of possible thickness of formed per cycle functional layers (Fig.2b), 3D MID-technologies can be divided into three groups:
thermo-active technologies with the thickness of layers from 100 to 200 microns (insert molding and two step molding);
thick-film technologies with the thickness of layers from 10 to 200 microns (laser structuring and 3D photolithography);
thin-film technologies with the thickness of layers less than 10 microns.
Depending on the speed of formation of the functional layers during one cycle (Fig.2c), technologies can be divided into two groups:
volume forming technologies with the speed of the formation of structures from 0.5 to 60 mm/min (insert molding and two step molding);
film technologies with the speed of the formation of structures of less than 0.5 mm/min.
From the point of view of the range of the used materials (table.2) all currently known technologies can be divided into the following groups:
"versatile" technologies that enables deposition of almost any material to almost any kind of substrates without restrictions on the types of materials and structures. This group includes plasma technologies of atmospheric pressure (flamecon and plasma dust);
"specialized" technologies that can be divided into technologies of "free substrate", which allows to use almost any type of substrates without restrictions on the types of materials and structures (jet sputtering and aerosol jet), and technologies of "free functional", which allows to use virtually any type of functional materials or even devices with certain types of substrates (insert molding);
"highly specialized" technologies, which use only certain types of functional materials associated with a particular type of substrate (two step molding, laser structuring and 3D photolithography).
Thus, the choice of a particular 3D MID-technology is determined by the parameters of products, materials and production volume.
Of course, the 3D-MID technologies have a number of disadvantages, as it does not solve several basic problems associated with the formation of 4D-elements of TEU:
need to use materials of TEU that can withstand a sufficiently high temperature during soldering (up to 260°C), so the widespread introduction of 3D MID-technology is limited by high cost of operating and supporting materials;
need to use at least two different processes and route cards, that is, the inability to create a TEU in a single technological cycle;
difficulties with the mounting of electronic components to the substrate, which requires precision three-dimensional system of electronic assembly on several axes with complex optical systems;
impossibility of making a full-fledged 4D-parts of TEU using as functional elements of all free faces, edges, and volume (or the entire thickness of the walls).
Based on a comparative analysis of different methods of creating a quasi-4D products using the 3D-MID technology it can be concluded that the following solutions are necessary for their further development and introduction into production:
systems of high performance multi-function facilities, allowing in the same industrial building (premises), to obtain the finished product, using entirely different technologies (from laser structuring to the galvanic deposition of metals) combined in a single technological process;
system of high-performance hybrid equipment, which allow to combine several different methods of processing or deposition of various types of materials in a single method. For example, to increase productivity and expand the range of materials that are deposited by aerosol jet it is necessary to create installations with a matrix of heads (nozzles) with an independent supply system (injection) of materials. Such a matrix should allow high-speed deposition of one material and the deposition of various types of materials, for example, with different melting point;
networks of continuous control of product parameters with use of camera systems, sensors, 3D scanners for non-destructive testing,which allows to carry out the culling of products at all stages of production, including the earliest;
wired and wireless connection of sensors and blocks to automated control system;
new principles of formation of functional structures and materials, particularly for manufacture in micron and submicron ranges.
5. PROSPECTS OF DEVELOPMENT OF 3D TECHNOLOGIES FOR TEU
The ultimate goal of the development of modern 3D technology is the development of industrial solutions, allowing to create 4D objects of TEU (table.2). But this goal is too complicated to implement in one generation of technology, so, from our point of view, it is appropriate to highlight the main challenges of the current stage of development:
creation of "hollow" 4D objects of TEU on the basis of cases of elements;
creation of a "monolithic" three-dimensional IC with their subsequent installation into the "hollow" 3D cases of TEU (for example, made using the 3D-MID technology);
creation of a "monolithic" three-dimensional integrated devices.
Since these tasks can be solved in parallel, it is necessary to introduce the concept of "generations" (Fig.3) in the classification of TEU.
4D-objects of the first generation are formed layer by layer using only the wall thickness of structural elements as functional elements. For example, the entire volume of the case of the electronic device can be used for the formation of the conductor layers and electrical circuits consisting of discrete resistors, capacitors, etc.
In uncased 4D-objects of the second generation the layer-by-layer formation of a monolithic three-dimensional integrated circuits (3D IC), consisting of interconnected layers of electrical conductors and circuits that include integrated resistors, capacitors, etc. is implemented. Subsequent operation of manufacture of a TEU is a encapsulation of monolithic 3D IC and their subsequent wiring.
For monolithic 4D-objects of the second generation is typical the layer-by-layer formation of three-dimensional devices consisting of a "built-in" external protective case with the corresponding external connections and of monolithic 3D IC on the basis of both integral and discrete resistors, capacitors, etc.
4D objects of the third generation are packaged and unpackaged plastic (flexible) devices consisting of several interconnected plastic objects. For example, shockproof mobile phone, includes the following components:
flexible multilayer printed motherboard manufactured with use of technology of unpackaged 4D-objects of the second generation;
multilayer ultrathin (about 1 mm) plastic flexible polymer display, obtained according to the OLED or PLED technology [3, 4], which is characterized by low power consumption, high resolution (UHD 4K or 8K), high dynamic contrast and wide color gamut;
environmentally friendly ultra-capacious flexible polymer power source (battery) [5];
flexible plastic case [6].
As an example of 4D-object of the second generation it is possible to compare standalone VHF-transmitters, one of which is made by up-to-date technology of printed circuit boards with components mounted on the surface, and another is made using promising technology, based on 3D tracing.
The device (Fig.4) consists of three VT-bipolar transistors, 11 capacitors, five resistors, two inductors, microphone, antenna and battery. The generator of the RF signal is assembled at the base of the VT2 transistor using the known three-point scheme. Circuit is tuned to the frequency of 96±5 MHz. Currently, this electrical circuit mounted on a printed circuit board using SMD components, has overall dimensions of 15 × 25 × 15 mm (Fig.5).
The design of the device in SolidWorks using the 3D tracing of the object with replacing a part of the circuitry (Fig.6), testifies to a possibility of manufacture of this device with dimensions 6 × 6 × 5 mm, that is reduction of his size by 30 times.
Comparative analysis of modern (mid-2016) technologies for creating 4D objects of TEU (table.3) allows to draw three main conclusions.
First, currently are developed only certain 3D manufacturing technologies of TEU, which are essentially allowing to obtain the integral structure of micron range. So, for example, by insert molding it is possible to manufacture a quasi 3D or 4D functional cell of products and further, using laser structuring and galvanic deposition, it is possible to create a passive part of the product.
Second, none of the existing technologies allows to create integrated single-level and multilevel quasi-4D objects of TEU in a single cycle, therefore, the immediate prospect of development is associated with the integration of different types of technologies in a single production line. It is necessary to develop equipment that meets the following requirements:
TEU should be made on the basis of three-dimensional computer models created by CAD tools;
the elements of the electronic circuit should be formed by different blocks of functional heads on all the free edges (possibly simultaneously) and in volume (or across the wall thickness) of the product;
creation of the TEU should occur in a continuous process cycle in a single 3D robotic system;
manufacture or installation of both passive and active elements and lines of interconnects;
system must be compatible with the manufactured functional materials (paints, inks) used in printed electronics to create conductors and active and passive elements.
As an example of one of the first steps towards the creation of manufacturing technologies of integrated single-level and multilevel quasi-4D objects of TEU it is possible to consider the existing hybrid technology, which allows to combine the installation of discrete electronic components and the creation of conductive layers [7, 8]. Using this technology the wing for the UAV with integrated printed electronic circuit composed of the discrete sensor (or chips) and conductive metal tracks, which works as antennas and power supply, was manufactured. Polymer extrusion (FDM, a 3D printing technology), has been used to create the carrier. Hybrid technology combined extrusion of molten metal for forming the circuit elements and conductors [7] and 3D-MID method of aerosol jet [8].
The third conclusion is that the long-term perspective of creating 4D objects of TEU should be linked to the development of fundamentally new technologies.
The main limiting factors in the production of new objects of TEU is a need to develop technologies and equipment, providing reduction of size and increase in the degree of integration of elements. That is, the development of new technology should be associated, primarily, with the increased resolution of the basic method based on a certain physical principle. Thus, upon transition to the submicron range the analysis of existing methods of miniaturization (creation of semiconductor TEU of appropriate dimensions) showed a significant reduction in the number of possible physical principles of TEU (Fig.7). One of solutions to this problem is the widespread introduction of group methods of functional electronics, providing a fundamental replacement of the basic methods of design of TEU and the creation of new element base. For example, instead of conductive metal interconnects (paths) it is possible to use optical waveguides, and lasers of various types as signal generators. ■
This article concludes a series of papers (see: Nanoindustry, 2016, Vol.3 (65), P. 90–96 and Nanoindustry, 2016, Vol.4 (66), P. 60–77), published in the framework of the Federal target program "Development of electronic component base for electronics", project N 14.429.11.0004.
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