Chapter 11 Fundamentals of Passives: Discrete, Integrated, and Embedded

1. Chapter 11 Fundamentals of Passives: Discrete, Integrated, and Embedded Presented by Paul Kasemir and Eric Wilson

2. Chapter Objectives • Define passives and their fundamental parameters • Describe the role of passives in electronic products • Introduce the different forms • Describe the different materials and processes used for passives

3. 11.1 What are Passives? • Can sense, monitor, transfer, attenuate, and control voltages • Cannot differentiate between positive and negative polarity • Cannot apply gain or amplification • Passives absorb and dissipate electrical energy • Ex. Resistor, inductor, capacitor, transformer, filter, switch, relay

4. 11.2 Role of Passives in Electronic Products • High frequency applications take smaller values (pF and nH) • Impedance matching to coax (50 ohm) • Power supplies require large capacitance • Digital circuitry requires decoupling capacitors for current surges • Resistors used for termination, filtering, timing and pull up/down

5. RF Passives • Filters, couplers, RF crossings, impedance matching, and antennas. • Signal inductors (1-20nH) and capacitors (1-20pF) • Choke Inductors (20-100nH) • Higher frequency requires smaller footprints, or even embedded passives • Mixed-Signal packages used in cell phones and GPS in MCM

6. 11.3 Fundamentals of Passives • Resistor • Resist current flow • Dissipate a power as heat • V = IR • Current Density, resistivity, conductivity, and sheet resistance

7. Fundamentals of Capacitor • Stores electrical charge Q • Dielectric between 2 metal plates • Capacitance C = QV = εA/d • I = C(dV/dt) DC open • Series and parallel capacitors • Reactance, impedance, ESR, leakage current

8. Fundamentals of Inductor • Stores energy in magnetic field • Wire coil with or without core • Inductance L = μn2Al • V = L(dI/dt) DC short • Magnetic cores increase B field, and thus inductance

9. Filters • Low-pass • High-pass • Bandpass • Bandstop • Series-parallel combination of R, L, and C

10. 11.4 Physical Representation

11. Physical Representation • Discrete – single passive • Integrated – multiple passives • Array • SIP and DIP resistor packages • Network • Filter circuits with only inputs and outputs as package terminals • Embedded • Created as part of the substrate

12. Passive Comparisons • In a typical circuit, 80% of components are passives • 50% of the PCB is taken by passives • 25% of solder connections go to passives • ~900 billion discrete units per year

13. 11.5 Discrete Passives • Resistors • Wire-wound • Nichrome wire • Film resistors • Carbon or metal film deposited on substrate • Carbon-composite • Graphite powder, silica and a binder

14. Resistor applications • Bias • Divider • Feedback • Termination • Pull up/down • Sense • Delay • Timing

15. Polar Capacitors • Aluminum electrolyte • Uneven surface gives efficiency • Tantalum • Pellet with lots of surface area • Cathode material limits conductivity

16. Nonpolar Capacitors • Film • Rolled • Stacked • Ceramic • Most dominant • Like stacked film • Used to need precious metals • Now Ni and Cu can be used • High Capacitance • 1-47 F

17. Capacitor Performance I • Remember capacitors have AC effects • Temperature coefficient • Typically less than 10% • Some can be on order of ppm/°C • Larger capacitance = worse coefficient

18. Capacitor Performance II • Voltage coefficient • Aging • Logarithmic • X7R 1% per decade hour (good) • Reversible

19. Capacitors Becoming Inductors • Caps have associated inductance • Self resonant frequency • ESL dependent on physical structure

20. Capacitor Applications I • Coupling • Timing and wave shaping • Changing RC time constant • Windshields

21. Capacitor Applications II • Filtering • Low pass filters • Decoupling • Mostly for digital signals

22. Inductors • SMT inductors looking like SMT caps • Core type • Value in henries, but should also have series resistance • “Choke” role • Timing circuits using Ls are gone

23. 11.6 Integrated Passives • Increased quantity decreases price • But maybe not as much as you would think • Smaller components = higher mounting costs • But maybe a lot more than you would think

24. Arrays and Networks • Arrays • Many of the same type in a single package • Good for R • Not as much for C • Networks • Different types in one package • Good for RC or RLC functions

25. 11.7 Embedded (Integral) Passives • Benefits • Smaller • Cheaper (???) • More reliable • Costs • New designs • New manufacturing processes

26. Integration Options • Ceramic • Thin film on Si • IC Integration • Horrible

27. Barriers to Embedded Passives • Risk • No reworkability • Cost • But wait until 2004!

28. Embedded Passives Technology • R • Thick film ~100-1M Ω/square • Thin film ~25-100 Ω/square • C • Typical inorganic is 50 nF/cm2 • GE has gotten ~200 nF/cm2 with inorganics • Polymer-ceramic components can get 4-25 nF/cm2 • L • Okay in embedded if <100 nH • Discrete recommended for >100 nH

29. The End