package and integration technology in point-of-load converters · 2017-04-25 · hybrid integration...

Package and Integration Technology in Point-of-load Converters

Laili WangXi’an Jiaotong University

Sumida Technology

Content

Introduction

Multi-permeability distributed air-gap inductor

Multi-permeability multi-window nonlinear inductor

Magnetic packaged power module

Introduction

The trend of integrated power module

Passive Devices

Control Circuit

System

Passive devices still take up more than 50% of the

volumePower

Semiconductor

Passive Devices

ControlCircuit

（Transformer，Inductor，Capacitor）

SystemNew generation semiconductor

Skin effect, proximity effect, fringing effect becomes worse

Hybrid integration technology is required

（Transformer，Inductor，Capacitor）

Power Semiconductor

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. 38-45.

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…

Introduction

Power System in Package

Introduction

Power System on Chip– High power density– Low parasitic inductance– High frequency– Application orientated– Low value for passives

S. Abedinpour et.al.. Session 19.7, ISSCC Conference, February 2006

A Multi-Stage Interleaved 45MHz Synch Buck Converter with Integrated Output Filter

Full off-line LED driver chip (Power IC with integrated PFC)Target specs: 15W, PFC >0.99, efficiency at full load >90%

The Metacapacitors Team: Prof. Steve O’Brien, Prof. Seth Sanders, Prof. Peter Kinget, Prof. Dan Steingart …

Chip photograph of fabricated GaN monolithic inverter IC in which 6 GITs are integrated

Making magnetics on IC

Embedding Technology

LTCC Technology

Introduction

Zhankun Gong; Qiaoliang Chen; Xu Yang, etc. “Design of high power density DC-DC converter based on embedded passive substrate”, 2008 IEEE PESC.

Integrated Converter with LTCC Substrate

Adding function integration of heatsink

8

PCB substrate

Generate waveforms

Smooth current

Mechanical assembly and layout

Protection

Switches

Inductor

Package

Substrate

Components Functions

Capacitor Smooth voltage

The LTCC substrate converter

Integrate three functions on one component

Inductor CapacitorSwitches

Controller

Package

Heatsink Dissipate heat

Heatsink

What’s the essence of heatsink ?

Reduce thermal resistance from hotspots to ambient

Introduction to LTCC Technology

Brief introduction about LTCC– Low temperature co-fired ceramic technology– Advantages

• Three dimensional inter-connection• Good for passive integration

Ceramic tapeFerrite tape

Capacitor tape

chip


Material

Ceramic tapeFerrite tape

Capacitor tape

Ag paste Capacitor paste Ferrite paste Dielectric composition

• Fabricating process


Punching via Filling via Screen printing

Laminating Co-firing Jointing


Content

Introduction





Background

Rac

fSi devices GaN devices100kHz~1MHz 1MHz~10MHz

Air-gap inductors in VRM and resonant converters

Fringing effect loss

New devices boost the frequency

Cross-section view of inductors


Quasi-distributed air-gap inductor

High permeability

Conductor

Low permeability

High permeability

Conductor

High permeability

Conductor

High permeability

Conductor

Air-gap inductor Add low permeability

Distributed air-gap Smaller air-gaps


Issues of distributed air-gap inductors

With low permeability magnetic core, the inductor has small inductance decrease, but its light load inductance is too small to increase efficiency.

With high permeability magnetic core, the inductor has higher light load inductance, but the inductance decreases quickly with the increase of current.

Indu

ctan

ce

Current

Low permeability

High permeability

Conductor

High permeability

Low permeability


Indu

ctan

ce

Current

High permeability

Low permeability

Three cross-section views uneven flux distribution. Varying the permeability distribution will result in higher inductance value without drop

Multi-permeability


Simulated flux density of single permeability of one-turn toroidal and planar inductors

Conductor

Ferrite

RI

RElr

wh

klr


RI

RE

RI

RElr

RI

RE

Advise to design 3~15 layers

Single permeability Continuous permeabilityMulti-permeability

Number of permeability layers


Continuously and discretely changed permeability

RI

RE

wh

k

µr(lr)

RI

RE

wh

k


How to arrange permeability values of each layer to maximize the inductance value

RI

RE

RI

RElr

RI

RE

Ba_maxBa_max

µ µ

Ri Ri+1

A3

A2

A1

A0

B3

B2

B1

B0

Continuous permeability

Discrete permeability

Single permeability Continuous permeability Multi-permeability


Permeability value for each layer

Ri Ri+1

A3

A2

A1

A0

B3

B2

B1

B0

A3

A2

A1

B3

B2

B1

Full load

Permeability distribution Per unit length inductance Inductance density

Single permeability Single permeabilitySingle permeability

The best value of the discrete permeability is the value of continuous permeability at inner radius of each layer.


Full load flux density distribution and inductance density


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


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


Prototype fabrication and test

2mm 0.26mm

3mm

单磁导率电感

0.4mm

1.2mm

0.4mm

0.26mm

3mm

双磁导率电感4001140010导体Conductor

1 /min

450 5 /min

850

Natural cooling

3 hr 5.5 hr

According to the simulation results, two prototypes whoseconductor width are 3mm made. 40010 and 40011 ferrite tapes from Electro-Science company are selected. They have permeability 50 and 200.

Temperature profile for co-firing the inductors


Two-permeability planar inductor– Specification: 5V Input, 3.3V/15A Output, 750kHz


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.

µr=9µr=40µr=100


Three-permeability toroidal inductor– Specification: 5V Input, 3.3V/15A Output, 750kHz

Single permeability

Two permeability


Inductance increase of metal power composite inductors

Sing permeability to three-permeabilityChip inductors are widely used in

POL converters, especially in 12V input VRM.

The inductance value could be significantly increased by using the three-permeability configuration

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)

Content

Introduction




Multi-permeability multi-window inductor

Improve light load efficiencyIo+I/2

Io-I/2

Io+I‘/2

Io-I‘/2

Io

Io'

ωt

T/2

T'/2

ωt

I

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25 30 35 40

Current(A)

Indu

ctan

ce(n

H)

Constant on time control converter Conduction loss and switching loss

Nonlinear inductor charateristic

Current ripple

Adaptive on time control Loss breakdown


Nonlinear inductor based on LTCC technology– Multi-permeability integration

h1h2h3

hn-1hn

Conventional nonlinear inductor LTCC nonlinear inductor

Inductance

Biased current Load currentInductance

Need extra DC bias, extra lossNeed extra DC bias, extra loss

Sharp inductance change, sensitive to bias currentSharp inductance change, sensitive to bias current

Inductance value is hard to controlInductance value is hard to control

Features


Nonlinearity of Vertical winding LTCC inductor

Io=5, µr=150 Io=10, µr=150 Io=15, µr=150

The magnetic material get saturated from the inner side, resulting in the nonlinearity


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

Indu

ctan

ce(µ

H)

Output Current (A) Output Current (A) Output Current (A) Output Current (A)

DCM CCMIn

duct

ance

(µH

)

Freq

uenc

y(kH

z)

Freq

uenc

y(kH

z)

Constant on time control based on constant inductance

Variable on time control based on LTCC nonlinear inductor


Nonlinear inductor based on LTCC technology– Nonlinear structure

Conductorµr=50µr=200

Solid coverage Top View Cross-section view

Different expansion coefficients results in bending problem during co-firing process

Failu

re

Sam

ple

Succ

essf

ul

Sam

ple

Sam

ple

Out

look

1.1mm1.1mm1.1mm

0.3mm

0.3mm

18%

17%

h1h2

h1h2/2

h2/2


Nonlinear inductor based on LTCC technology– Specification: 12V input, 1.6V/30A output, Fsw = 500~1000kHz

010020030040050060070080090010001100

0100200300400500600700800900

10001100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Frequency

(kH

z)

Inductance (

nH)

Output Current (A)

70

75

80

85

90

95

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30Current (A)

Effic

ienc

y (%

)

0.1uH Inductor 0.15uH Inductor LTCC nonlinear inductor

Inductance(nH)

DCR(mΩ)

Volume(mm3)

Chip inductor I 100 0.96 609.84Chip inductor II 150 1.2 609.84Nonlinear

inductor130~660 1.2 921

3A output current (X: 1µs/div, Y: 2.5A/div) 30A output current (X: 0.4µs/div, Y: 2.5A/div).

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.

Content

Introduction





Adding function integration of heatsink

41

PCB substrate

Generate waveforms

Smooth current

Mechanical assembly and layout

Protection

Switches

Inductor

Package

Substrate

Components Functions

Capacitor Smooth voltage

The magnetic packaged converter

Integrate three functions on one component

Inductor CapacitorSwitches

Controller

Package

Heatsink Dissipate heat

Heatsink

What’s the essence of heatsink ?

Reduce thermal resistance from hotspot to ambient


Power System-in-Inductor

Bigger Inductor volumeSame module volume

Higher inductance value

Higher thermal conductivity

Lower winding resistance

Save cost for plastic packaging

Plastic packaging Magnetic packaging


Hot spots and thermal conduction paths

43

Winding Chip

Magnetic material

Substrate

Winding Chip

Magnetic material

Substrate

Plastic material

Plastic

Magnetic material

Plastic

3W/m-k

0.6W/m-k5 times

Less thermal resistance to ambient


Heat contributors in magnetic packaged module

44

Winding Chip

Magnetic material

Substrate

Magnetic core is also a heat source

Chip (fixed); Magnetic core (minor);Winding (variable)

Heat sources:

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


Loss of the module with different parameters

45

Converter Winding Loss(mW)

Core Loss (mW)

Switches Loss (mW)

L1 752 66 1246L2 500 164 1250L3 248 210 1256

Inductor Thickness(mm)

Width(mm)

Radius(mm)

DCR(mΩ)

Inductance Value(μH)

L1 0.1 1.2 2.5 17.6 1.7L2 0.15 1.2 1.8 11.7 1L3 0.2 1.2 1.5 5.8 0.75

Tested loss curves of the magnetic material

Loss breakdown of the converter with different inductors

Assign the loss to heat sources and simulate the temperature distribution


Simulated temperature of different windings

46

DCR=5.8mΩ, copper loss=248mWt=0.2mm, R=2mm, w=1.5mm

DCR=11.7mΩ, copper loss=500mWt=0.15mm, R=1.5mm, w=1.2mm

DCR=17.6mΩ, copper loss=752mWt=0.1mm, R=1.5mm, w=1mm.

DCR=5.8mΩ, copper loss=248mWt=0.2mm, R=2mm, w=1.5mm;

DCR=11.7mΩ, copper loss=500mWt=0.15mm, R=1.5mm, w=1.2mm;

DCR=17.6mΩ, copper loss=752mWt=0.1mm, R=1.5mm, w=1mm.

Cas

e te

mpe

ratu

reIn

tern

al te

mpe

ratu

re


Thermal comparison of different inductors

47

Inductor Loss of inductors Internal temperature Maximum Case temperature

Winding(mW)

IC (mW) Winding (mW) IC (mW)

L1 248 1256 59.2 57.4 58.74L2 500 1250 62.3 59.4 61.98L3 752 1246 67.0 63.4 66.21

Can’t choose L1 to make prototype, choose L2 to make prototype1. The inductance value is lower than specified (1μH);2. The magnetic material above and below the winding is too thin to make


Analytical thermal models

48

The thermal model has small thermal resistance in upper direction

Three hotspots in both models: IC (PIC_diss), Inductor winding (Pwinding_diss), Magnetic core (Pcore_diss).


Plastic packaged power module

Thermal resistance contributed by

plastic

The thermal model has higher thermal resistance in upper direction because of plastic packaging


Calculated temperature based on the models

49

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


Simulated temperature

50

Plastic packaged power module, DCR=11.7mΩ

Magnetic packaged power module, DCR=11.7mΩ

Plastic packaged power module, DCR=17.6mΩ.

Magnetic material packaged module, DCR=11.7mΩ

Plastic packaged module, DCR=11.7mΩ

Plastic packaged power module, DCR=17.6mΩ.

61.73

70.59659.36

52.29

65.02

54.41 55.6

67.172.82

Cas

e te

mpe

ratu

reIn

tern

al te

mpe

ratu

re


Comparison of analytical results and simulation results

51

Inductor Calculation temperature ( ) Simulation ( )

Winding IC Winding ICMagnetic package DCR=11.7mΩ

60.70 58.80 61.73 59.36

Plastic package DCR=11.7mΩ 65.02 62.50 70.60 65.02Plastic package DCR=17.6mΩ 73.40 67.20 72.82 67.10Improvement 12.70 8.40 11.09 7.74

1. The calculation results correlate well with the simulation results;2. The junction temperature of IC is reduced by 8 with the new technology


Prototype and test

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 2 4 6 8 10

Indu

ctan

ce (µ

H)

Current (A)

Simulation

Measurement

The error between simulation and measurement is 0.3μH at 10A

Pressure

Flux density distribution in the core at 6AAC resistance of magnetic packaged inductor at 6A


Experiment 1

Comparison with plastic package solutionSame inductance value

Same active devices

Same PCB layout

Verify the inductor has better performance

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.


Experiment 2

Comparison with commercial productsVerify the magnetic packaged power module has better performance

Magnetic packaged module on PCB

Commercial plastic packaged module on PCB

Commercial plastic packaged module

Commercial plastic packaged module

Magnetic packaged module

Magnetic packaged module

For fair comparison, the PCB board area is the same, and layout is similar

3.3% higher efficiency

VIN=12V

VOUT=5V/6A

Fs=780kHz


Temperature test

55

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

Efficiency curves

VIN=12V, VOUT=5V/6A, Fs=780kHz

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 performanceThe magnetic packaged power module has higher efficiency for its lower DCR

56

Positions Available

Invite talents to join in Laili Wang’s research teamAs a new professor in Xi’an Jiaotong University, Laili Wang is

conducting several big projects, and he is strongly supported by theDepartment of Electrical Engineering to recruit faculty/research fellow to joinin 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 [email protected]

package and integration technology in point-of-load converters · 2017-04-25 · hybrid integration...

Documents