Package and Integration Technology in Point-of-load Converters. Laili Wang Xi an Jiaotong University Sumida Technology

Transcription

1 Package and Integration Technology in Point-of-load Converters Laili Wang Xi an Jiaotong University Sumida Technology

2 Content Introduction Multi-permeability distributed air-gap inductor Multi-permeability multi-window nonlinear inductor Magnetic packaged power module

3 Introduction The trend of integrated power module Power Semiconductor Control Circuit System Passive Devices (Transformer, Inductor, Capacitor) New generation semiconductor Power Semiconductor Control Circuit System Passive Devices (Transformer, Inductor,Capacitor) Passive devices still take up more than 50% of the volume Skin effect, proximity effect, fringing effect becomes worse Hybrid integration technology is required D. Reusch, D. Gilham, Y. Su and F. C. Lee, "Gallium Nitride based 3D integrated non-isolated point of load module," Applied Power Electronics Conference and Exposition (APEC), 2012 Twenty-Seventh Annual IEEE, Orlando, FL, 2012, pp

4 Introduction Voltage Rating Input Voltage Rating: 5V, 12V, 24V, 48V. Applications 5V, Portable Electronics, Cell Phone Charger, POL on Mother Board 12V, POL on Mother Board,VRM 24V, Battery system, Drones, Industrial Application 48V, New Power System in Data Center Challenges Power density, Efficiency, Thermal

5 Introduction Power System in Package

6 Introduction Power System on Chip High power density Low parasitic inductance High frequency Application orientated Low value for passives A Multi-Stage Interleaved 45MHz Synch Buck Converter with Integrated Output Filter Chip photograph of fabricated GaN monolithic inverter IC in which 6 GITs are integrated Full off-line LED driver chip (Power IC with integrated PFC) Target specs: 15W, PFC >0.99, efficiency at full load >90% Making magnetics on IC S. Abedinpour et.al.. Session 19.7, ISSCC Conference, February 2006 The Metacapacitors Team: Prof. Steve O Brien, Prof. Seth Sanders, Prof. Peter Kinget, Prof. Dan Steingart

7 Introduction Embedding Technology Zhankun Gong; Qiaoliang Chen; Xu Yang, etc. Design of high power density DC-DC converter based on embedded passive substrate, 2008 IEEE PESC. LTCC Technology

8 Integrated Converter with LTCC Substrate Adding function integration of heatsink Controller Package Switches Inductor Heatsink PCB substrate Capacitor Components Switches Inductor Package Substrate Capacitor Heatsink Functions Generate waveforms Smooth current Protection Mechanical assembly and layout Smooth voltage Dissipate heat What s the essence of heatsink? Reduce thermal resistance from hotspots to ambient The LTCC substrate converter Integrate three functions on one component 8

9 Introduction to LTCC Technology Brief introduction about LTCC Low temperature co-fired ceramic technology Advantages Three dimensional inter-connection Good for passive integration chip Ceramic tape Ferrite tape Capacitor tape

10 Introduction to LTCC Technology Material Ceramic tape Ferrite tape Capacitor tape Ag paste Capacitor paste Ferrite paste Dielectric composition Fabricating process

11 Introduction to LTCC Technology Punching via Filling via Screen printing

12 Introduction to LTCC Technology Laminating Co-firing Jointing

13 Content Introduction Multi-permeability distributed air-gap inductor Multi-permeability multi-window nonlinear inductor Magnetic packaged power module

14 Multi-permeability distributed air-gap inductor Background Air-gap inductors in VRM and resonant converters Fringing effect loss New devices boost the frequency R ac Cross-section view of inductors Si devices GaN devices f 100kHz~1MHz 1MHz~10MHz

15 Multi-permeability distributed air-gap inductor Quasi-distributed air-gap inductor Low permeability Conductor Conductor High permeability Air-gap inductor High permeability Add low permeability Conductor Conductor High permeability Distributed air-gap High permeability Smaller air-gaps

16 Multi-permeability distributed air-gap inductor Issues of distributed air-gap inductors High permeability Inductance Low permeability Current With low permeability magnetic core, the inductor has small inductance decrease, but its light load inductance is too small to increase efficiency. Low permeability High permeability Conductor With high permeability magnetic core, the inductor has higher light load inductance, but the inductance decreases quickly with the increase of current.

17 Multi-permeability distributed air-gap inductor Three cross-section views uneven flux distribution. Varying the permeability distribution will result in higher inductance value without drop Inductance Multi-permeability Low permeability High permeability Current

18 Multi-permeability distributed air-gap inductor Simulated flux density of single permeability of oneturn toroidal and planar inductors lr R E R I Conductor Ferrite lr k h w

19 Multi-permeability distributed air-gap inductor Number of permeability layers Single permeability Multi-permeability Continuous permeability R E lr R E R E R I R I R I Advise to design 3~15 layers

20 Multi-permeability distributed air-gap inductor Continuously and discretely changed permeability R E R E R I R I k k h w h w µ r (l r )

21 Multi-permeability distributed air-gap inductor How to arrange permeability values of each layer to maximize the inductance value Single permeability Continuous permeability Multi-permeability R E lr R E R E R I R I R I B a_max µ µ B a_max A 3 A 2 A 0 A 1 B 3 B 0 B 2 B 1 Continuous permeability Discrete permeability R i R i+1

22 Multi-permeability distributed air-gap inductor Permeability value for each layer A 3 B 3 A 3 B 3 B 0 A 2 B 2 A 0 A 2 B 2 A 1 B 1 A 1 B 1 The best value of the discrete permeability is the value of continuous permeability at inner radius of each layer. R i R i+1 Full load Single permeability Single permeability Single permeability Permeability distribution Per unit length inductance Inductance density

23 Multi-permeability distributed air-gap inductor Full load flux density distribution and inductance density

24 Multi-permeability distributed air-gap inductor Two methods to realize the multi-permeability inductor Use low temperature co-fired ceramic technology (LTCC) to fabricate the inductor. Use flexible magnetic sheet to fabricate the inductor. LTCC tapes Magnetic sheets

25 Multi-permeability distributed air-gap inductor Two-permeability planar inductor The layer to layer structure of the LTCC inductor makes it very difficult to design a complete two permeability inductor, an approximate prototype is designed. The permeability of external layer is higher than should be, leading to lower heavy load inductance. Low permeability ferrite High permeability ferrite Conductor

26 Multi-permeability distributed air-gap inductor Prototype fabrication and test 2mm 0.26mm 3mm 单磁导率电感 0.4mm 1.2mm 0.4mm 0.26mm 导体 Conductor 3mm 双磁导率电感 According to the simulation results, two prototypes whose conductor width are 3mm made and ferrite tapes from Electro- Science company are selected. They have permeability 50 and /min Natural cooling 1 /min 3 hr 5.5 hr Temperature profile for co-firing the inductors

27 Multi-permeability distributed air-gap inductor Two-permeability planar inductor Specification: 5V Input, 3.3V/15A Output, 750kHz

28 Multi-permeability distributed air-gap inductor Three-permeability toroidal inductor Three kinds of magnetic sheets are employed to make the inductors. They are C350 from Epcos, IRJ04 and IRJ09 from TDK. They have permeability 9, 40 and 100. µ r =9 µ r =40 µ r =100

29 Multi-permeability distributed air-gap inductor Three-permeability toroidal inductor Specification: 5V Input, 3.3V/15A Output, 750kHz Single permeability Two permeability

30 Multi-permeability distributed air-gap inductor Inductance increase of metal power composite inductors Chip inductors are widely used in POL converters, especially in 12V input VRM. Sing permeability to three-permeability The inductance value could be significantly increased by using the three-permeability configuration

31 Summary The multi-permeability distributed air-gap inductor could increase inductance for the whole load range. Two kinds of multi-permeability inductors are designed and fabricated to identify the effect of inductance increase. Great Efficiency improvement of DC/DC converters. High potential for industry application (VRM, power module)

32 Content Introduction Multi-permeability distributed air-gap inductor Multi-permeability multi-window nonlinear inductor Magnetic packaged power module

33 Multi-permeability multi-window inductor Improve light load efficiency I I o + I/2 I o I o - I/2 I o + I /2 I o ' I o - I /2 T/2 T'/2 ωt ωt Constant on time control converter Current ripple Conduction loss and switching loss Inductance(nH) Current(A) Nonlinear inductor charateristic Adaptive on time control Loss breakdown

34 Multi-permeability multi-window inductor Nonlinear inductor based on LTCC technology Multi-permeability integration Inductance Inductance Biased current Conventional nonlinear inductor Load current LTCC nonlinear inductor Features Need extra DC bias, extra loss Sharp inductance change, sensitive to bias current Inductance value is hard to control h 1 h2 h3 h n-1 h n

35 Multi-permeability multi-window inductor Nonlinearity of Vertical winding LTCC inductor Io=5, µ r =150 Io=10, µ r =150 Io=15, µ r =150 The magnetic material get saturated from the inner side, resulting in the nonlinearity

36 Multi-permeability multi-window inductor Nonlinear inductor based on LTCC technology Improve light load efficiency Reduce switching loss without reducing voltage ripple Reduce conduction loss without reducing switching frequency Control strategy Constant on time control based on constant inductance value Variable on time control based on LTCC nonlinear inductor Inductance(µH) Frequency(kHz) DCM CCM Inductance(µH) Frequency(kHz) Output Current (A) Output Current (A) Output Current (A) Output Current (A) Constant on time control based on constant inductance Variable on time control based on LTCC nonlinear inductor

37 Multi-permeability multi-window inductor Nonlinear inductor based on LTCC technology Nonlinear structure 18% h 1 h 2 17% h 2 /2 h 1 h 2 /2 Conductor µr=50 µr=200 Solid coverage Top View Cross-section view Different expansion coefficients results in bending problem during co-firing process 0.3mm Failure Sample Successful Sample Sample Outlook 1.1mm 1.1mm 1.1mm 0.3mm

38 Multi-permeability multi-window inductor Nonlinear inductor based on LTCC technology Specification: 12V input, 1.6V/30A output, Fsw = 500~1000kHz Inductance (nh) Output Current (A) Frequency (khz) Inductance DCR( Volume(mm (nh) mω) 3 ) Chip inductor I Chip inductor II Nonlinear inductor 130~ Efficiency (%) A output current (X: 1µs/div, Y: 2.5A/div) 30A output current (X: 0.4µs/div, Y: 2.5A/div) Current (A) 0.1uH Inductor 0.15uH Inductor LTCC nonlinear inductor

39 Summary Multi-hole multi-permeability nonlinear inductor has better nonlinearity Compared with constant value chip inductor, the nonlinear inductors can significantly improve the light load efficiency of DC/DC converters.

40 Content Introduction Multi-permeability distributed air-gap inductor Multi-permeability multi-window nonlinear inductor Magnetic packaged power module

41 Magnetic packaged power module Adding function integration of heatsink Controller Package Switches Inductor Heatsink PCB substrate Capacitor Components Switches Inductor Package Substrate Capacitor Heatsink Functions Generate waveforms Smooth current Protection Mechanical assembly and layout Smooth voltage Dissipate heat What s the essence of heatsink? Reduce thermal resistance from hotspot to ambient The magnetic packaged converter Integrate three functions on one component 41

42 Magnetic packaged power module Power System-in-Inductor Bigger Inductor volume Same module volume Higher thermal conductivity Lower winding resistance Save cost for plastic packaging Higher inductance value Plastic packaging Magnetic packaging

43 Magnetic packaged power module Hot spots and thermal conduction paths Less thermal resistance to ambient Magnetic material Winding Chip Magnetic material Plastic 3W/m-k 0.6W/m-k 5 times Substrate Plastic material Magnetic material Plastic Winding Chip Substrate 43

44 Magnetic packaged power module Heat contributors in magnetic packaged module Magnetic material Winding Chip Substrate Magnetic core is also a heat source Heat sources: Chip (fixed); Magnetic core (minor); Winding (variable) By changing the parameters of the windings, the DCR of the inductor varies, leading to temperature variation. Simulation is executed to show its effect. Fixed number of turns: 5.5 Sweep radius (R), width (w) and thickness (t) to obtain different DCR and winding loss 44

45 Magnetic packaged power module Loss of the module with different parameters Inductor Thickness (mm) Width (mm) Radius (mm) DCR (mω) Inductance Value (μh) L L L Converter Winding Loss (mw) Core Loss (mw) Switches Loss (mw) L L L Loss breakdown of the converter with different inductors Tested loss curves of the magnetic material Assign the loss to heat sources and simulate the temperature distribution 45

46 Magnetic packaged power module Simulated temperature of different windings Case temperature DCR=5.8mΩ, copper loss=248mw t=0.2mm, R=2mm, w=1.5mm DCR=11.7mΩ, copper loss=500mw t=0.15mm, R=1.5mm, w=1.2mm DCR=17.6mΩ, copper loss=752mw t=0.1mm, R=1.5mm, w=1mm. Internal temperature DCR=5.8mΩ, copper loss=248mw t=0.2mm, R=2mm, w=1.5mm; DCR=11.7mΩ, copper loss=500mw t=0.15mm, R=1.5mm, w=1.2mm; DCR=17.6mΩ, copper loss=752mw t=0.1mm, R=1.5mm, w=1mm. 46

47 Magnetic packaged power module Thermal comparison of different inductors Inductor Loss of inductors Internal temperature Maximum Case temperature Winding (mw) IC (mw) Winding (mw) IC (mw) L L L Can t choose L1 to make prototype, choose L2 to make prototype 1. The inductance value is lower than specified (1μH); 2. The magnetic material above and below the winding is too thin to make 47

48 Magnetic packaged power module Analytical thermal models Thermal resistance contributed by plastic Magnetic packaged power module The thermal model has small thermal resistance in upper direction Plastic packaged power module Three hotspots in both models: IC (P IC_diss ), Inductor winding (P winding_diss ), Magnetic core (P core_diss ). The thermal model has higher thermal resistance in upper direction because of plastic packaging 48

49 Magnetic packaged power module Calculated temperature based on the models Magnetic packaged power module with 11.7mΩ inductor Plastic packaged power module with 11.7 mω inductor Plastic packaged power module with 17.6 mω inductor 49

50 Magnetic packaged power module Simulated temperature Case temperature Magnetic packaged power module, DCR=11.7mΩ Plastic packaged power module, DCR=11.7mΩ Plastic packaged power module, DCR=17.6mΩ. Internal temperature Magnetic material packaged module, DCR=11.7mΩ Plastic packaged module, DCR=11.7mΩ Plastic packaged power module, DCR=17.6mΩ. 50

51 Magnetic packaged power module Comparison of analytical results and simulation results Inductor Calculation temperature ( ) Simulation ( ) Magnetic package DCR=11.7mΩ Winding IC Winding IC Plastic package DCR=11.7mΩ Plastic package DCR=17.6mΩ Improvement The calculation results correlate well with the simulation results; 2. The junction temperature of IC is reduced by 8 with the new technology 51

52 Magnetic packaged power module Prototype and test 1.2 Pressure Inductance (µh) Simulation Measurement Current (A) The error between simulation and measurement is 0.3μH at 10A Flux density distribution in the core at 6A AC resistance of magnetic packaged inductor at 6A

53 Magnetic packaged power module Experiment 1 Verify the inductor has better performance Comparison with plastic package solution To leave enough margin for plastic packaging, the inductor has to be smaller. L=1μH, DCR=17.6mΩ The losses of the active devices are exactly the same. So 3% difference come from the inductors. Same inductance value Same active devices Same PCB layout

54 Magnetic packaged power module Experiment 2 Verify the magnetic packaged power module has better performance Comparison with commercial products For fair comparison, the PCB board area is the same, and layout is similar Magnetic packaged module on PCB Commercial plastic packaged module on PCB 3.3% higher efficiency Commercial plastic packaged module Magnetic packaged module VIN=12V VOUT=5V/6A Commercial plastic packaged module Magnetic packaged module Fs=780kHz

55 Magnetic packaged power module Temperature test Efficiency curves VIN=12V, VOUT=5V/6A, Fs=780kHz 1. The proposed module has lower temperature than the commercial plastic packaged modules with same size 2. The proposed module (15mm*9mm) has the same temperature with commercial plastic packaged modules with the size 15mm*15mm 55

56 Summary The proposed magnetic packaged power module can significantly reduce the junction temperature for lower thermal resistance from junction to ambient. Variation of winding parameters have significant effect on thermal performance The magnetic packaged power module has higher efficiency for its lower DCR 56

57 Positions Available Invite talents to join in Laili Wang s research team As a new professor in Xi an Jiaotong University, Laili Wang is conducting several big projects, and he is strongly supported by the Department of Electrical Engineering to recruit faculty/research fellow to join in his team. There are several positions available for applying. 1. Tenure track asistant/associate professor; 2. Professional Research Staff; 3. Postdoctoral Research Fellow. If you have interest to join in Laili Wang s team, please send your CV to llwang@mail.xjtu.edu.cn