Printed Circuit Design & Fab - September 2008 - (Page 40)

nanotEch TV Printed Capacitors Figure 4A. Representative test vehicle (TV) and corresponding cross-section view of screen printed cross-section view of screen printed embedded capacitors embedded capacitors and resistors (Collaboration: Georgia Tech PRC and Nokia.) FiGurE 4. Representative test vehicle (TV) and corresponding and resistors (Collaboration: Georgia Tech PRC and Nokia. 1 mm 2 mm FiGurE 5. Printed resistors. Figure 5. Printed resistors. B A 12.5 !m FiGurE 6. (A) Spiral inductors, and (B) cross section of multilayered spiral inductors. Figure 6. (A) Spiral inductors, and (B) cross section of multilayered spiral inductors. Capacitors and Resistors Novel classes of polymer nanocomposites that have shown a high dielectric constant are the BaTiO3 epoxy nanocomposites. These are used to fabricate thin-film embedded FiGurE 7. Change in capacitance IR reflow reflow Figure 9. Change in capacitance afterafter IR(assembly)(assembly capacitors. High temperature/pressure lamination was pre-conditioning (3X, 2450C) and thermal shock up to 1400 shock up (-55C-125C) cycles (-55C-125C) for large, medium an used to embed capacitors in multilayer PCBs. The capacicycles to 1400 for large, medium and small capacitors for embedded capacitors. tor fabrication is based on a sequential build-up technology employing a first-etched copper electrode. After patterning of the electrode, the nanocomposite can be they are capable of being printed in the internal layers of deposited and laminated within a PCB. Nanocomposites circuit boards. We have developed various discrete resistors can be directly deposited by printing. FiGurE 3 shows a with a sheet resistance ranging from 1 ohm to 120 M ohm. Resistors in various ranges (e.g. 1, 5, 10, 50 and 100 ohms) process flow for making screen-printed, discrete embedded can easily be made. Resistor materials can be printed in the capacitors and resistors. Capacitance values are defined same internal layer. FiGurE 5 shows printed resistors with by the feature size, thickness and dielectric constant of the polymer-ceramic compositions. FiGurE 4 shows a different lines and spaces. representative test vehicle (TV) and corresponding crosssectional views of screen printed embedded capacitors and Inductors resistors. Measurement of electrical properties of capaciInk-jet printing of spiral structures can be used to form tors fabricated from nanocomposite prints and with areas inductors. The spacing in the spiral and resistance will of ~2 mm2 to 100 mm2 (smallest circle electrode 0.060” dictate quality of inductors. High resistance causes thermal loss and, therefore, is not suitable for inductors. In this diameter and square was 0.109” x 0.109”) showed high example, we deposited multi-metal layers on ink-jet printed capacitance density ranging from 5 nF/in.2 to 25 nF/in.2, lines to increase current carrying capacity or conductance. depending on composition, particle size and thickness of High conductance spirals can generate a higher magnetic the prints. Thin-film capacitors fabricated from 40% to field at the same voltage, thus providing a higher inductance 60% v/v BaTiO3 epoxy nanocomposites showed a stable in smaller packages. We used a variety of multi-metal laycapacitance density in the range of 5 nF/in to 20 nF/in.2 ers including electroless copper, immersion gold, electroless and low loss ~0.012 to 0.022. Measurement of electrical gold, electroless palladium, electroless nickel and others. properties of capacitors fabricated from 70% v/v nanocomposite showed capacitance density of about 25 nF/in.2. FiGurE 6 shows a representative example of multi-metalCapacitance density of BaTiO3-epoxy polymer nanocomlayer-based inductors. Multi-metal layer deposition reduces posites modified with nanomaterial was also investigated. line resistance to hundreds of milliohms. Capacitance density of nanomaterials with modified films was higher than BaTiO3-epoxy nanocomposites. Reliability Nanococomposites are attractive for resistor applicaReliability of the nanocomposites was ascertained using tions because variable resistor materials can be formed IR reflow, thermal cycling, the pressure cooker test (PCT) simply by changing the metal insulator ratio. These comand solder shock. The change in capacitance after three positions, however, have practical advantage only when times in IR reflow and after 1,000 cycles of deep thermal 40 printEd CirCuit dESign & fAB SEPTEMBER 2008

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - September 2008

Printed Circuit Design & Fab - August 2008 Contents Our Line Market Watch Around the World Happenings ROI Positive Plating Off the Shelf Marketplace Ad Index EMC for the Real World Final Finish Forum Design for Green: Laminates A Systematic Approach to Increasing Layer Count The NTI $100 Million Club Printable Nanocomposites BGA Bulletin

Printed Circuit Design & Fab - September 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.