Konstantinos I. Papathomas

Influence of Nanoparticles, Low Melting Point (LMP) Fillers, and Conducting Polymers on Electrical, Mechanical, and Reliability Performance of Micro-Filled Conducting Adhesives for Z-Axis Interconnections

This paper discusses micro-filled epoxy-based conducting adhesives modified with nanoparticles, conducting polymers, and low melting point (LMP) fillers for z-axis interconnections, especially as they relate to package level fabrication, integration, and reliability. A variety of conducting adhesives with particle sizes ranging from 80 nm to 15 mum were incorporated as interconnects in printed wiring board (PWB) or laminated chip carrier (LCC) substrates. SEM and optical microscopy were used to investigate the micro-structure, and conducting and sintering mechanisms. Volume resistivity of modified adhesives is in the range of 10-5 to 10-6 ohm-cm. Adhesives formulated with a conducting polymer exhibited tensile strength with Goulds JTC-treated Cu ges 3800 PSI, and as low as 1800 PSI for a conducting polymer-LMP based system. There was no delamination of conductive joints after 3X IR-reflow, pressure cooker test (PCT), and solder shock. Among all, the conducting polymer modified micro-filled adhesives showed the highest mechanical strength. The paper also describes a combinatorial approach to the synthesis of LMP coated particles. Several conductive adhesives were used in a z-axis interconnect construction for a laminate chip carrier and printed wiring board (PWB). The present process allows fabrication of z-interconnect conductive joints having diameters in the range of 55-300 microns. The processes and materials used to achieve smaller feature dimensions, satisfy stringent registration requirements, and achieve robust electrical interconnections are discussed.

Printable Nanocomposites for Advanced Organic Packaging

This paper examines the use of nanocomposites or materials in the area of printing technology. A variety of printable nanomaterials for advanced organic packaging have been developed. This includes nano capacitors and resistors as embedded passives, nano magnetic materials, multifunctional materials, etc. Nanocomposites can provide high capacitance densities, ranging from 5 nf/inch2 to 25 nF/inch2, depending on composition, particle size and film thickness. The electrical properties of capacitors fabricated from BaTiO3-epoxy nanocomposites showed a stable capacitance and low loss over a temperature range from 25degC to 100degC. A variety of printable discrete resistors with different sheet resistances, ranging from 1 ohm to 120 Mohm, processed on large panels (19.5 inches times 24 inches) have been fabricated. Low resistivity nanocomposites, with volume resistivity in the range of 10-4 ohm-cm to 10-6 ohm-cm depending on composition, particle size, and loading can be used as conductive joints for high frequency and high density interconnect applications. Thermosetting polymers modified with ceramics can produce low k dielectrics with k value in the range between 5.41 and 3.59. Similarly, low loss dielectric materials can be produced form mixing epoxy with silica or other low loss fillers. Reliability of the nanocomposites was ascertained by IR-reflow, thermal cycling, pressure cooker test (PCT), and solder shock. Change in capacitance after 3X IR-reflow and after 1000 cycles of deep thermal cycling (DTC) between -55degC and 125degC was within 5%. Most of the nanocomposites in the test vehicle were stable after IR-reflow, PCT, and solder shock.

Resin coated copper capacitive (RC3) nanocomposites for system in a package (SiP): Development of 3-8-3 structure

Embedded passives account for a very large part of todays electronic assemblies. This is particularly true for products such as cellular phones, camcorders, computers and several critical defense devices. Market pressures for new products with more features, smaller size and lower cost demand smaller, compact, simpler substrates. An obvious strategy is to reduce the number of surface mounted passives by embedding them in the substrate. In addition, current interconnect technology to accommodate surface mounted passives imposes certain limits on board design which constrain the overall system speed. Embedding passives is one way to minimize the functional footprint while at the same time improving performance. This paper discusses thin film technology based on resin coated copper capacitive (RC3) nanocomposites. In particular, we highlight recent developments on high capacitance, large area, thin film passives and their integration in System in a Package (SiP). A variety of RC3 nanocomposite thin films ranging from 8 microns to 50 microns thick were processed on Cu substrates by liquid coating. Multilayer embedded capacitors resulted in high capacitance 16–28 nF. The fabricated test vehicle also included two embedded resistor layers with resistance in the range of 15 ohms to 100 kohms. To enable high performance devices, an embedded resistor must meet certain tolerances. The embedded resistors can be laser trimmed to a tolerance of ≪5%, which is usually acceptable for most applications. We have an extended embedded passives solution that has been demonstrated both through its high wireability designs and package performance to be perfectly suited for the system in package (SiP) applications. As a case study, we have designed and fabricated eight layer high density internal passive core and subsequently applied fine geometry 3 buildup layers to form a 3-8-3 structure. The passive core technology is capable of providing up to 6 layers of embedded capacitance and could be extended further. This effort is an integrated approach centering on three interrelated fronts: (1) materials development and characterization; (2) fabrication, and (3) integration at the device level.

Resin coated copper capacitive (RC3) nanocomposites for multilayer embedded capacitors

This paper discusses thin film technology based on resin coated copper capacitive (RC3) nanocomposites. In particular, we highlight recent developments on high capacitance, large area, thin film passives, their integration in printed wiring boards (PWB), system in package (SiP) and chip package substrates and the reliability of the embedded capacitors. A variety of RC3 nanocomposite thin films ranging from 2 microns to 50 microns thick were processed on PWB substrates by liquid coating or printing processes. SEM micrographs showed uniform particle distribution in the coatings. The electrical performance of composites was characterized by dielectric constant (Dk), capacitance and dissipation factor (loss) measurements. Nanocomposites resulted in high capacitance density (7-500 nF/inch2) at 1 MHz. The manufacturability of these films and their reliability has been tested using large area (13 inch times 18 inch or 19.5 inch times24 inch) test vehicles. Reliability of the RC3 nanocomposite was ascertained by IR-reflow, PCT (pressure cooker test) and solder shock. As a case study, an example of RC3 based multilayer embedded capacitor construction for a flip-chip plastic ball grid array package with a 300 mum core via pitch is given. This effort is an integrated approach centering on three interrelated fronts: (1) materials development and characterization; (2) fabrication, and (3) integration at the device level.

Manufacturing Substrates with Embedded Passives

Passives account for a very large part of todays electronic assemblies. This is particularly true for digital products such as cellular phones, camcorders, computers and several critical defense devices. This paper presents an entire process from design and fabrication to electrical characterization and reliability test of embedded passives on organic multilayered substrates. A variety of thin film capacitor and resistors were utilized to manufacture high-performance embedded passives. The electrical properties of capacitors fabricated from polymer-ceramic nanocomposites showed a stable capacitance and low loss over a wide temperature range. We have designed and fabricated several printed wiring board (PWB) and flip-chip package test vehicles focusing on resistors and capacitors. Two basic capacitor cores were used for this study. One is a layer capacitor. The second capacitor in this case study was discrete capacitor. In both cases, capacitance values are defined by the feature size, thickness and diele...

“Green” nanocomposites for electronic packaging

This paper examines the use of nanocomposites in the area of “green” technology. A variety of green materials for advanced organic packaging have been developed. These include capacitors and resistors as embedded passives, resin coated Cu (RCC) as buildup layers, highly conducting nano-micro media for Z-interconnects, lead free assembly paste, ZnO based additives and magnetic materials. Nanocomposites can provide high capacitance densities, ranging from 5 nf/inch2 to 25 nF/inch2, depending on composition, particle size and film thickness. The electrical properties of capacitors fabricated from BaTiO3-epoxy nanocomposites showed a stable capacitance over a temperature range from 20°C to 120°C. A variety of printable discrete resistors with different sheet resistances, ranging from 1 ohm to 120 Mohm, processed utilizing a large panel format (19.5 × 24 inches) have been fabricated. Low resistivity nanocomposites, with volume resistivity in the range of 10−4 ohm-cm to 10−6 ohm-cm depending on composition, particle size, and loading can be used as conductive joints for high frequency and high density interconnect applications. A variety of metals including Cu, Ag, LMP (low melting point) and LMP-coated Cu fillers have been used to make halogen free, lead free electrically conducting adhesive technology as an alternative to solders. Halogen free resin modified with ceramics/organic particles can produce low Dk resin coated Cu (RCC) with Dk value in the range between 4.2 and 3.2. Similarly, low loss RCC materials can be produced by combining HF resin with low loss fillers. The mechanical strength of the various RCC was characterized by a 90 degree peel test and measurement of tensile strength. RCC exhibited peel strength with Goulds JTC-treated Cu as high as 6 lbs/inch for halogen free RCC. These halogen free RCC materials exhibit coefficients of thermal expansion (CTE), ranging from 27 ppm/°C to 32ppm/°C. Altogether, this is a new direction in the development of Green Packages and more specifically in the development of coreless substrates for semiconductor packaging.

Resin coated copper capacitive (RC3) nanocomposites for multilayer embedded capacitors: towards system in a package (SiP)

Purpose – Embedded passives account for a very large part of todays electronic assemblies. This is particularly true for products such as cellular phones, camcorders, computers, and several critical defence devices. Market pressures for new products with more features, smaller size and lower cost demand smaller, compacter, simpler substrates. An obvious strategy is to reduce the number of surface mounted passives by embedding them in the substrate. In addition, current interconnect technology to accommodate surface mounted passives imposes certain limits on board design which constrain the overall system speed. Embedding passives is one way to minimize the functional footprint while at the same time improving performance. The purpose of this paper is to describe the development of a thin film technology based on ferroelectric‐epoxy polymer‐based flake‐free resin coated copper capacitive (RC3) nanocomposites to manufacture multilayer embedded capacitors.Design/methodology/approach – This paper discusses t...