Voya R. Markovich

Nano‐ and micro‐filled conducting adhesives for z‐axis interconnections: new direction for high‐speed, high‐density, organic microelectronics packaging

Purpose – The purpose of this paper is to discuss the use of epoxy‐based conducting adhesives in z‐axis interconnections.Design/methodology/approach – A variety of conductive adhesives with particle sizes ranging from 80 nm to 15 μm were laminated into printed wiring board substrates. SEM and optical microscopy were used to investigate the micro‐structures, conducting mechanism and path. The mechanical strength of the various adhesives was characterized by 90° peel test and measurement of tensile strength. Reliability of the adhesives was ascertained by IR‐reflow, thermal cycling, pressure cooker test (PCT), and solder shock. Change in tensile strength of adhesives was within 10 percent after 1,000 cycles of deep thermal cycling (DTC) between −55 and 125°C.Findings – The volume resistivity of copper, silver and low‐melting point (LMP) alloy based paste were 5 × 10−4, 5 × 10−5 and 2 × 10−5 Ω cm, respectively. Volume resistivity decreased with increasing curing temperature. Adhesives exhibited peel strength...

Printable electronics: towards materials development and device fabrication

Purpose – There has been increasing interest in the development of printable electronics to meet the growing demand for low‐cost, large‐area, miniaturized, flexible and lightweight devices. The purpose of this paper is to discuss the electronic applications of novel printable materials.Design/methodology/approach – The paper addresses the utilization of polymer nanocomposites as it relates to printable and flexible technology for electronic packaging. Printable technology such as screen‐printing, ink‐jet printing, and microcontact printing provides a fully additive, non‐contacting deposition method that is suitable for flexible production.Findings – A variety of printable nanomaterials for electronic packaging have been developed. This includes nanocapacitors and resistors as embedded passives, nanolaser materials, optical materials, etc. Materials can provide high‐capacitance densities, ranging from 5 to 25 nF/in2, depending on composition, particle size, and film thickness. The electrical properties of ...

Fabrication, integration and reliability of nanocomposite based embedded capacitors in microelectronics packaging

We have developed a variety of barium titanate (BaTiO3)–epoxy polymer nanocomposite based thin film capacitors. In particular, we highlight recent developments on high capacitance, large area, thin film passives, their integration in printed wire board (PWB) substrates and the reliability of the embedded capacitors. A variety of nanocomposite thin films ranging from 2 microns to 25 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 provided high capacitance density (10–100 nF inch−2) and low loss (0.02–0.04) at 1 MHz. The manufacturability of these films and their reliability has been tested using large area (13 inch × 18 inch or 19.5 inch × 24 inch) test vehicles. Reliability of the test vehicles was ascertained by IR reflow, thermal cycling, pressure cooker test (PCT) and solder shock. Capacitors were stable after PCT and solder shock. Capacitance change was less than 5% after IR reflow (assembly) preconditioning (3×, 245 °C) and 1400 cycles deep thermal cycle (DTC).

High capacitance, large area, thin film, nanocomposite based embedded capacitors

This paper discusses thin film technology based on barium titanate (BaTiO3)-epoxy polymer nanocomposites. In particular, we highlight recent developments on high capacitance, large area, thin film passives, their integration in PWB substrates and the reliability of the embedded capacitors. A variety of nanocomposite thin films ranging from 2 microns to 25 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 (10-100 nF/inch2) and low loss (0.02-0.04) 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 test vehicles was ascertained by IR-reflow, thermal cycling, PCT (pressure cooker test) and solder shock. Capacitors were stable after PCT and solder shock. Capacitance change was less than 5% after IR reflow (assembly) preconditioning (3X, 245 degC) and 1400 cycles DTC (deep thermal cycle)

Laser Micromachining of Barium Titanate

This paper discusses laser micromachining of barium titanate (BaTiO3)-polymer nanocomposite thin films. In particular, recent developments on high-capacitance, large-area, thin, flexible, embedded capacitors are highlighted. A variety of barium titanate (BaTiO3)-epoxy polymer nanocomposite-based flexible/rollable thin films ranging from 2 to 25 mum thick were processed on large-area substrates (330 mm times 470 mm, or 495 mm times 607 mm) by liquid coating processes. The electrical performance of composites was characterized by dielectric constant (Dk), capacitance, and dissipation factor (loss) measurements. Nanocomposites provided high capacitance density (10-100 nF/in2) and low loss (0.02-0.04) at 1 MHz. Scanning electron microscopy (SEM) micrographs showed uniform particle distribution in the coatings. Uniform mixing of nanoparticles in the epoxy matrix results in high dielectric (> 3 times 107 V/m) and mechanical strengths (> 3700 PSI). Reliability of the capacitor was ascertained by thermal cycling. Capacitance change was less than 5% after baking at 140degC for 4 h, and 1100 cycles from -55degC to 125degC (deep thermal cycle). A frequency-tripled Nd:YAG laser operating at a wavelength of 355 nm was used for the micromachining study. The micromachining was used to generate arrays of variable-thickness capacitors from the nanocomposites. The resultant thickness of the capacitors depends on the number of laser pulses applied.

({\hbox {BaTiO}}_{3})

This paper describes the design and process for an advanced card technology capable of achieving wiring densities of the order of 500-1000 in/sq. inch. Its unique features consist of using a photosensitive dielectric (PSD) redistribution layer to produce very small (2-4.0 mil) blind vias, as well as utilizing PCB signal and power planes for global interconnect of fine grid surface mount components (QFPs, SMA, and ICs). The process consists of subtractive etched power cores and/or additively plated signal cores. The subcomposite is completed using conventional PCB processing. The redistribution layer is added sequentially by coating and/or laminating a photosensitive dielectric and photoprocessing the blind vias. The circuitization of the redistribution layer is completed by a full additive plating process and/or electro pattern plating. A solder mask is applied, and Eutectic Solder is electroplated over the surface for component assembly. A key element of the technology that will allow the escape of high I/O components with a dense interconnecting grid (8.0-20.0 mils/200-500 microns), is the utilization of the signal and power planes in the subcomposite structure.<<ETX>>

-Epoxy Nanocomposite-Based Flexible/Rollable Capacitors: New Approach for Making Library of Capacitors

This paper discusses a new 3D “Package-Interposer-Package” (PIP) solution suitable for combining multiple memory, ASICs, stacked die, stacked packaged die, etc., into a single package. Recent work on interposers to join multiple packages is highlighted, with particular attention paid to the processing of the electrical joints formed between the interposer and package. A variety of package-interposer-package joining approaches were considered. Photographs were used to investigate the joining, conducting mechanism and path. Traditional Package-on-Package (PoP) approaches use direct solder connections between the packages and are limited to use of single (or minimum) die in the bottom package(s) in order to avoid warpage and poor reliability performance. This is because each package may have a different warpage trend from room temperature to reflow temperature when combined with other packages. For PIP, the stability imparted by the interposer reduces warpage and increases stability, allowing assemblers of the PIP to select the top and bottom components (packages, dies, stacked die, modules) from various suppliers. PIP can accommodate multiple stacks of dies. PIP can use modules with stacked die where modules can be organic, ceramic, or silicon board, where each can be detached and replaced without affecting the rest of the package. Thus PIP will be economical for high-end electronics, where a damaged, non-functional part of the package can be selectively removed and replaced. The paper also describes interconnect construction for a PIP. The present process allows fabrication of PIP interconnect joints having diameters in the range of 55–300 microns, allowing finer pitch, higher density packaging structures. The processes and materials used to achieve smaller feature dimensions, satisfy stringent registration requirements, and achieve robust electrical interconnections are discussed.

Film redistribution layer technology

This paper discusses laser micromachining of barium titanate (BaTiO3)-polymer nanocomposites and sol-gel thin films. In particular, recent developments on high capacitance, large area, and thin flexible embedded capacitors are highlighted. A variety of flexible nanocomposite thin films ranging from 2 microns to 25 microns thick were processed on copper or organic substrates by large area (13 inch times 18.5 inch, or 19.5 inch times 24 inch) liquid coating processes. SEM micrographs showed uniform particle distribution in the coatings. Nanocomposites resulted in high capacitance density (10-100 nF/inch2) and low loss (0.02-0.04) at 1 MHz. The remarkably increased flexibility of the nanocomposite is due to uniform mixing of nanoparticles in the polymer matrix, resulting in an improved polymer-ceramic interface. BaTiO3-epoxy polymer nanocomposites modified with nanomaterials were also fabricated and were investigated with SEM analysis. Capacitance density of nanomaterial-modified films was increased up to 500 nF/inch2, about 5-10 times higher than BaTiO3-epoxy nanocomposites. A frequency-tripled Nd:YAG laser operating at a wavelength of 355 nm was used for the micromachining study. The micromachining was used to generate arrays of variable-thickness capacitors from the nanocomposites. The resultant thickness of the capacitors depends on the number laser pulses applied. Laser micromachining was also used to make discrete capacitors from a capacitance layer. In the case of sol-gel thin films, micromachining results in various surface morphologies. It can make a sharp step, cavity-based wavy structure, or can make individual capacitors by complete ablation. Altogether, this is a new direction for development of multifunctional embedded capacitors.

Package-Interposer-Package (PIP): A breakthrough Package-on-Package (PoP) technology for high end electronics

Recent development work on flex joining using different pre-pregs is highlighted, particularly with respect to their integration in laminate chip carrier substrates, and the reliability of the joints formed between the rigid and flex surfaces. A variety of rigid-flex structures were fabricated, with 1 to 3 flex layers laminated into printed wiring board substrates. Photographs and optical microscopy were used to investigate the joining, bending, and failure mechanism. Flexibility decreased with increasing number of metal layers. The flexibility of the various flexes was characterized by roll diameter and bend angle. Flex substrates exhibited roll diameter with polyimide dielectric as low as 180 mils for 2 metal layers, and as high as 1300 mils for 6 metal layers. Similarly, bending for 12 metal layers flex with thin and thick dielectric were <1 inch and >1 inch, respectively. Reliability of the rigid-flex was ascertained by IR-reflow, thermal cycling, pressure cooker test (PCT), and solder shock. There was no delamination for Resin coated copper (rigid)-polyimide (flex) samples after IR-reflow, PCT, and solder shock. The paper also describes a novel approach for the fabrication of flexible electronics on PDMS substrates. It was found that with increasing thickness, the flexibility of the polydimethylsiloxane (PDMS) based substrate decreased less due to stretching property of PDMS. The present process evaluates the fabrication of PDMS substrates using different circuit lines and spaces.

Laser Micromachining of Nanocomposite-Based Flexible Embedded Capacitors

This article examines the use of nanomaterials in the area of electronic packaging. This includes capacitors and resistors as embedded passives, low-k materials, electrically conducting adhesives (ECAs) as interconnects, thermal interface materials (TIMs), etc.