Jin-Gul Hyun

Frequency and Temperature Dependence of Dielectric Constant of Epoxy/BaTiO3 Composite Embedded Capacitor Films (ECFs) for Organic Substrate

In this study, temperature dependence of capacitance, one of the most important properties of ECFs, was investigated. Temperature dependence of ECFs capacitance was determined by temperature dependence of dielectric constant and thickness, and among these, main factor was dielectric constant of ECFs. Dielectric constant of ECFs is determined by that of epoxy and BaTiO3 powders. Below 130degC, dielectric constant of ECFs increased as temperature increased, and was mainly affected by an epoxy matrix. However, above 130degCs the Curie temperature of BaTiO3, the increase rate of ECFs dielectric constant started decreasing, because BaTiO3 powder undergoes a phase transition from a tetragonal to a cubic structure and its dielectric constant decreases at 130degC. Dielectric constant of BaTiO 3 powder was obtained from measured dielectric constants of ECF and applying the Lichtenecker logarithmic rule. Dielectric constants of ECFs at high frequency range (0.1~10GHz) were measured using a cavity resonance method. For both powders, dielectric constants in high frequency range were about 3/4 of the dielectric constants at 1 MHz. This difference is mainly due to the decrease of dielectric constant of epoxy matrix. For BaTiO3 ECFs, there was a dielectric relaxation at 5~9GHz presumably due to the polarization mode change of BaTiO3 powder

A Study on Dielectric Constants of

Epoxy/BaTiO3 composites have been of great interest as embedded capacitor materials, mainly due to high dielectric constant of ceramic powders, and good process compatibility of epoxy with printed circuit boards (PCBs). However, one of the potential problems of epoxy/BaTiO3 composite is the dielectric relaxation at gigahertz range. In this paper, epoxy/SrTiO3 composite embedded capacitor films (ECFs) were fabricated for high-frequency applications. Dielectric constants of epoxy/SrTiO3 composite embedded capacitor films with various SrTiO3 particles loading for three different commercial SrTiO3 powders were measured, and experimental data were fitted to the Lichtenecker equation for the prediction of the effective dielectric constant of SrTiO3 powders in epoxy/ SrTiO3 composite ECFs. Using a rectangular cavity resonator method, dielectric constants of epoxy/SrTiO3 composite ECFs were measured at gigahertz range (1-10 GHz). At gigahertz frequencies, dielectric constants of epoxy/SrTiO3 composite ECFs were nearly constant. In contrast, epoxy/BaTiO3 composite ECFs showed decrease of dielectric constants above 5 GHz. Therefore, it is concluded that epoxy/SrTiO3 composite ECFs can be more effectively to be applied for high-frequency applications.

{\rm Epoxy/SrTiO}_{3}

Epoxy/BaTiO/sub 3/ composite embedded capacitor films (ECFs) were newly designed for high dielectric constant and low-tolerance (less than /spl plusmn/5%) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of a specially formulated epoxy resin and latent curing agent, and in terms of a coating process, a comma roll coating method is used for uniform film thickness in large area. The dielectric constant of ECF in high frequency range (0.5/spl sim/3 GHz) is measured using the cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. The dielectric constant is calculated by observing the frequencies of the resonant cavity modes. Calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of the epoxy matrix. The dielectric relaxation of barium titanate (BaTiO/sub 3/: BT) powder is not observed within measured frequency. An alternative material for embedded capacitor fabrication is epoxy/BaTiO/sub 3/ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming a capacitor partially in the desired part. However, the screen printing makes surface irregularities during mask peel-off. Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, a dielectric layer with improved thickness uniformity is successfully demonstrated. Using epoxy/BaTiO/sub 3/ composite ECP, a dielectric constant of 63 and specific capacitance of 5.1 nF/cm/sup 2/ were achieved.

Composite for Embedded Capacitor Films (ECFs)

Embedded capacitor technology is one of the methods to miniaturize and to obtain higher performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been of great interest as embedded capacitor materials for packaging applications, because they have good processability and compatibility with printed circuit boards (PCB), in addition to high dielectric constant. In this study, we have demonstrated the fabrication of prototype-scale embedded capacitors in manufacturing scale PCBs using multi-layer PCB build-up process. Specially formulated B-stage epoxy/BaTiO3 embedded capacitor films (ECFs) were used as not only an adhesive between two copper clad laminates (CCLs) but also capacitor dielectrics for embedded capacitors. The total thickness of PCB included embedded capacitor was below 250 mum. Dielectric properties of epoxy/BaTiO3 ECFs were measured at 100 kHz using a LCR meter, and the dielectric properties at high frequency were measured using devices specially designed for correcting stray effect around capacitors. High temperature storage test at 150degC, high temperature /humidity test with 60degC/60RH% condition, and reflow process at 260degC were performed to evaluate the reliability of prototype-size embedded capacitors. In summary, fabrication of B-stage epoxy/BaTiO3 composite embedded capacitors in prototype-scale 405 times 508 mm PCBs using CCL was successfully demonstrated using conventional PCB manufacturing processes, and their dielectric properties and reliability were evaluated.

Epoxy/BaTiO/sub 3/ composite films and pastes for high dielectric constant and low-tolerance embedded capacitors fabrication in organic substrates

Epoxy/BaTiO3 composite embedded capacitor films (ECFs) were newly designed for high dielectric constant and low tolerance (less than plusmn5%) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric properties of BaTiO3 (BT) & SrTiO3 (ST) composite ECF is measured MIM capacitors with oxygen plasma etched ECFs on 10times10 cm PCBs. For 1times1 mm capacitors with 12 um thickness and 50 vol.%BTO ECFs, dielectric constant of 39, dielectric loss of 0.017, capacitance density of 2.4 nF/cm2, and less than 10% tolerance were obtained. Dielectric constant of BTOECF is bigger than that of STECF, and it is due to difference of permittivity of BT and SrTiO3 particles. Dielectric constant of BT & ST ECF in high frequency range (0.5~10 GHz) is measured using a cavity resonance method. In order to estimate dielectric constants at high frequency, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. Although there was no dielectric relaxation observed at pure epoxy, for BT ECF, there is the dielectric relaxation at 5~9GHz. It is mainly due to changing of polarization mode of BT powder itself. In contrast, there is no relaxation for ST ECF up to 10 GHz. Alternative material for embedded capacitor fabrication is epoxy/BT composite embedded capacitor pastes (ECPs). It uses similar materials formulation like ECFs and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired area. But the screen printing makes surface irregularity during mask peel-off. Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. For 4times4 mm capacitors with 11 um thickness and 50 vol.% BT ECFs, dielectric constant of 39, dielectric loss of 0.023, capacitance density of2.6nF/cm2, and 22% tolerance were obtained

Fabrication and characterization of embedded capacitors in printed circuit boards using B-stage epoxy/BaTiO 3 composite embedded capacitor films (ECFs)

Embedded capacitor technology is one of effective packaging technologies for further miniaturization and higher performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been of great interest as embedded capacitor material, because they have good process compatibility with multilayer organic substrates applications such as printed circuit boards (PCBs). In this work, less than 7% tolerance embedded epoxy/BaTiO/sub 3/ composite capacitors made of newly developed embedded capacitor films (ECFs) composed of low temperature rapid curing epoxy resin, latent curing agent, and barium titanate powder were successfully fabricated on PCBs and Si wafers. Then capacitor properties were characterized. Compared to epoxy/BaTiO/sub 3/ composite capacitor solutions (or pastes) deposited by a spin coating method, ECFs have excellent advantages such as lower capacitance tolerance over large area, no waste of materials, good film formation capability and processability, long shelf life, and good thermo-mechanical stability after final epoxy cure. Over 100 dielectric constant numbers were obtained using two different size BaTiO/sub 3/ powders mixtures. Another important capacitor property of the capacitor films, leakage current, was also less than 10/sup -7/ A/cm/sup 2/ which is excellent enough for decoupling capacitor applications. Epoxy resin formulation, curing agent, dispersant, and several additives were optimized to produce good film formation capability, fast curing characteristics at 180/spl deg/C of less than 20 seconds, good BaTiO/sub 3/ powder dispersion control, and excellent shelf life for handling. Typically, capacitors of /spl plusmn/7 /spl mu/m film thickness with 10 nF/cm/sup 2/ with less than 7% tolerances and low leakage current (less than 10/sup -7/ A/cm/sup 2/ at 10 V) were successfully demonstrated on PCBs and Si wafers using newly developed epoxy/BaTiO/sub 3/ composite capacitor films. These capacitor films can be embedded on selective areas of PCBs during build-up processes or other substrates such as Si and ceramic substrates.

Epoxy/BaTiO3 (SrTiO3) Composite Films and Pastes For High Dielectric Constant and Low Tolerance Embedded Capacitors in Organic Substrates

In this study, we have demonstrated new patterning method of epoxy/BaTiO3 composite ECFs for fine patterning using the combination of reactive ion etching and ultrasonic cleaning. And the effect of patterning processes on the dielectric properties of epoxy/BaTiO3 composite ECFs has been also investigated. The capacitance and dielectric loss of the fine patterned ECFs were lower than those of non-patterned ECFs. The dielectric constant and capacitance of patterned ECFs decreased by 10% and dielectric loss by 40% due to thermal history during the etching process. In addition, the pattern size of ECFs has also affected dielectric properties. The dielectric constant slightly increased from 34 to 37 and capacitance tolerance from plusmn5% to plusmn9%, as the pattern size decreased from 4 mm times 4 mm to 1 mm times 1 mm. It was mainly due to the increased tolerance of finer defined electrode areas. The dielectric constant of 37, capacitance of 2.4 nF/cm2, and capacitance tolerance of plusmn9% was obtained by 1 mm times 1 mm size fine patterned capacitors. As a result, ECFs patterning method using plasma etching and ultrasonic cleaning was successfully demonstrated for fine patterned embedded capacitors.

Low tolerance epoxy/BaTiO/sub 3/ composite embedded capacitor films (ECFs)

Epoxy/BaTiO3 composites have been of great interest as embedded capacitor materials, mainly due to high dielectric constant of ceramic powders, and good process compatibility of epoxy with printed circuit boards (PCBs). However, one of the potential problems of epoxy/BaTiO3 composite is the dielectric relaxation at GHz range. In this paper, epoxy/SrTiO3 composite ECFs were fabricated for high frequency applications. Dielectric constants of epoxy/SrTiO3 composite embedded capacitor films with various SrTiO3 particles loading for three different commercial SrTiO 3 powders were measured from 100 Hz to 1 MHz, and experimental data at 100 kHz were fitted to the Lichtenecker equation for the prediction of the effective dielectric constant of SrTiO3 powders in epoxy/SrTiO3 composite ECFs. Using a rectangular cavity resonator method, dielectric constants of epoxy/SrTiO 3 composite ECFs were measured at GHz range (1-10 GHz). At GHz frequencies, dielectric constants of epoxy/SrTiO3 composite ECFs were nearly constant. In contrast, epoxy/BaTiO3 composite ECFs showed significant decrease of dielectric constants above 5GHz. Therefore, it is concluded that epoxy/SrTiO3 composite ECFs cab be more effectively to be applied for high frequency applications.

Characteristics of Fine Patterned Epoxy/BaTiO3 Composite Embedded Capacitor Films (ECFs) for Organic Substrates

Epoxy/BaTi03 composite embedded capacitor films (ECFs) were newly designed for high dielectric constant and low tolerance (less than ±5%) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of ECF in high frequency range (0.5∼3GHz) is measured using cavity, resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. Calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. Dielectric relaxation of BT powder is not observed within measured frequency. Alternative material for embedded capacitor fabrication is epoxy/BaTiO3 composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off. Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using epoxy/BaTiO3 composite ECP, dielectric constant of 63 and specific capacitance of 5.InF/c2 were achieved.

Frequency behavior of embedded epoxy/SrTiO 3 composite capacitor materials

Embedded capacitor technology is an essential method for miniaturization and high performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been of great interest as embedded capacitor materials because they have good processability, compatibility with printed wiring boards (PWB), and high dielectric constant.