Packaging 4.0 for power electronics: towardshigher power density, an integration

perspective with focus on package andassembly

State of the Art and Proposed Development

Cyril BUTTAY1, Florent MOREL1, Christian MARTIN1,Rémy CAILLAUD2, Johan LE LESLE2, Roberto MRAD2,

Nicolas DEGRENNE2, Rémi PERRIN2,3, Stefan MOLLOV2,Bruno ALLARD1

1Laboratoire Ampere, Univ. Lyon, France2Mitsubishi Electric Research Centre Europe, Rennes, France

3Center for Power Electronic Systems, Univ. Viginia Tech., USA

22/11/2018 - IRT Nanoélectronique1 / 32

Outline

Introduction

State of the Art of PCB embedding

Proposition – Design Tools for Power Electronics

Conclusions

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Power electronics – Areas for Progress

Source: Kolar et al. [1]Source: Kerachev et al. [2]

I Excellent active devices are now available (SiC, GaN)I Many topologies introduced over the years;

I Recent changes: multilevel, multicellular structuresI Integration and Packaging are the main areas for progress

I Reduce size and circuit parasitics, improve thermal management. . .I Manage increased density of interconnexion

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Power electronics – Areas for Progress

Source: Texas Instruments

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Power electronics – Areas for Progress

Source: P. Waltereit et al [3]

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PCB Technology

Surface-mount component

Via

Microvia

Wirebonds

External copper layer

Internal copper layers

Semiconductor die

Fiber/polymer laminate

Solder

Printed Circuit Board isMature I Large range of available design software

I Can be manufactured in large quantities, low priceI Mainly oriented towards microelectronics and low power

Flexible I Custom designI Many configurations possible

Limited I Poor thermal conductivity

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Sample circuit

I Main issues:I Parasitics

I Optimization of boardI Option 3D-2 not sufficientI Necessity to go further

source: A. Letellier [4]

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Why Embedding?

I Optimize thermal managementI Heat sources closer to heatsinkI Dual side cooling

I Improve performanceI Shorter interconnectsI Lower inductances

I Reduce sizeI Use substrate volume

I Manage complex interconnectsI Batch process

Surface-mount component

Via

Microvia

Wirebonds

External copper layer

Internal copper layers

Semiconductor die

Fiber/polymer laminate

Solder

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Embedding of Power Dies – 1

I Most embedding effort on power dies:I Most power densityI Fastest voltage/current transients

I Requires special finish on diesI 5-10 µm Cu (not standard)I Buffer for UV laserI Also for microetch in plating step

I Backside connexion by sintering or viasI Sintering compatible with standard diesI Vias require Cu finish and adhesive

conductive chip attach

embedding by lamination

via drilling top, through-via

Cu plating and structuringLeft and above, source: Ostmann [5]

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Embedding of Power Dies – 2Some alternative techniques

I Stud bumps and machiningI Foam interposerI Mechanical drilling

Source: Hoene et al. [6]

Source: Pascal et al. [7]Source: Sharma et al. [8]

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Embedding of Formed Components – Capacitors

Source: Dupont [9]

Source: Andresakis [10]

I introduction of a capacitive layer inthe stack-up

I thin layer (8–25 µm)I high permittivity (e.g. BaTiO3 filler)

I single layer plane capacitorÜ low capacitance densityÜ limited voltage strength

I ≈ 1 nF cm−2 for 100 V rating

Ü more suited to GHz-rangedecoupling than to power electronics

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Embedding of Formed Components – Inductors

Magnetic Layer

I Relies on magnetic/polymer film Ü Low µr

I Limited to 10 – 100 WSource: Waffenschmidt et al. [11]

Planar magnetic componentsI Very common, but not really embeddedI High performanceI Compatible with low (W) or high power (kW)

Embedded coreI Strong industrial development (Murata, AT&S,

Wurth)I Currently limited to low power (W)

Source: Ali et al. [12]

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Embedding of Inserted Components

Soldered components:I Suits most Surface-Mount DevicesI Connexions with regular vias

Vias to components:I Requires components with Cu finishI More compact (vias on components)

Source: Ostmann [5]

For power electronicsI Embedding of “large” capacitors (1 µF range)I Embedding of gate driver ICs and peripheral components, control

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Thermal Management of Embedded Components – 1

I Poor thermal conductivity of FR4 compared to ceramics(1–7 W m−1 K−1 vs 150 W m−1 K−1 for AlN)

I In theory better breakdown field (≈ 50 kV mm−1 vs. 20 kV mm−1)To improve through-plane heat conduction:

I Micro-vias (electrically conductive), Filled cores (e.g. alumina)To increase in-plane heat conduction:

I Thicker copper, Anisotropic layers (Graphite), Dual-phase

Source: left: Liew et al. [13]; right: Silvano et al. [14]

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Reliability of PCB with Embedded Components

Source: Randoll et al. [15]. Superimposition of reliabilitydata for dies in PCB on Infineon’s results for standardpower modules

Source: Perrin et al. [16]. Left: standard FR4, right:low-CTE. Magnetic core embedded, after 1000 thermalcycles (-50/200 ◦C)

I Temperature-related issuesI Rapid degradation above 190 ◦CI Hydrocarbon, polyimide-based

PCBs resistant up to 250 ◦CI Thermal cycling issues

I CTE of PCBs much higher thanceramic or semiconductor

I Availability of low-CTE materialsÜ lacks data on large components

I Other PCB-specific issuesI moisture absorption,I conductive anodic filaments. . .

Ü No showstopper identified yet!

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Compact power supply

Embedded transformerI Simple PCB approach

I High Temp pre-pregI Few processing steps

I 3000-h aging

Source: Rémi Perrin [17].

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Conclusions on Embedding Technology

Application to Power ElectronicsI Many components can be

embeddedI Dies require Cu finishI Large components?

I Acceptable thermal performanceOpen questions

I Find the sweet spot:I Embedding power dies only?I Embed everything?I Or somewhere in-between?

I Are flat converters desirable?I How to design for embedding?

Mitsubishi: SiC PFC Cell, 750 W, PCB size 7×7×1 cm3 . SiCdies, gate driver circuit, PFC inductor and temperature sensorsembedded in PCB.

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Design in Power Electronics – Current State

Specifications Pre-design(ideal circuit)

Specifications

Mechanical design

Parasitics extraction Thermal modeling

Circuit simulation

Pre-design(ideal circuit)

Specifications

Heterogeneous models(various formats, physical domains)

Inputs

Implementation loop

Mechanical design

Parasitics extraction Thermal modeling

Circuit simulation

Pre-design(ideal circuit)

Specifications

Manufacturing

Continous validationfor manufacturabilityHeterogeneous models

(various formats, physical domains)

Inputs

Implementation loop

Mechanical design

Parasitics extraction Thermal modeling

Circuit simulation

Pre-design(ideal circuit)

Specifications

Test

Manufacturing

Continous validationfor manufacturabilityHeterogeneous models

(various formats, physical domains)

Inputs

Implementation loop

Mechanical design

Parasitics extraction Thermal modeling

Circuit simulation

Pre-design(ideal circuit)

Specifications

Power Modules

Components off-the-shelf

Custom components (magnetics...)

Custom parts (PCB...)

Standard parts (e.g. magnetic cores)

Semiconductor dies

PCB assembly

Final assembly

Converter

Other custom & standard parts (housing, heatsink...)

pcb=flexibility

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Design in Power Electronics – Real-case example

Implementation

Manufacturing

Legend

Operation Transformer design Power electronics design Control design

Input Analytic design

Thermal managementdesign basedon converterspecifications

Power modulesdesign

Selection/design ofauxiliary elements

(gate driver,capacitors, etc.)

Selection of real-time platform

OutputControl designin simulatedenvironment

Existingmechanical design

First estimation ofconverter losses

Detailed powerelectronics circuit

Design ofa low power

converter mock-up

Finite Elementsdesign

Refinement oftransformer

losses calculation

Physicalimplementation

of power electronics

Internal design ofthe power modules

Routing ofgate driver

Mock-upfabrication and test

Physicalimplementationof transformer

Mechanical designof converter

Validation of controlwith Mock-up PHIL

Circuit models,including layout

parasitics, excl. driver

Design of controlsystem iterfaces

ManufactureTransformer Manufacture Module Manufacture Driver

Manufacture otherinverter elements(frame, busbars. . . )

ManufactureInterfaces

Transformer testingExperimental

dynamic testing(Double-pulse)

Modify drivers

Experimental lossescharacterization,second estimationof converter losses

Assemble inverters

Design andbuild test bench Assemble converters Installation in

dedicated test benchFull converter testing

Source: Supergrid Institute, submitted article22 / 32

Design in Microelectronics

Source: Cadence

Integrated software forI Circuit designI RoutingI SimulationI Mask generation. . .

Why not available in power electronics?I powerful financial incentive for virtual prototyping

I A 45 nm mask set costs ≈ 2 M$ (source: Electronic design, 2009)

I Limited technology variationsI Most of the circuit is monolithicI No flexibility allowed in technology configuration

Ü Manufacturers supply a “design toolkit” describing the technology

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Proposition – Design in Power Electronics

Components off-the-shelf

Standard parts (e.g. magnetic cores)

Semiconductor dies

PCB manufacturing

Converter

Custom parts (heatsink...)

I Rationalized manufacturingÜ Reduce design variabilityI Design Toolkit for simulation

and validationÜ Design for manufacturing

Specifications

Inputs

Components/cellslayout

Reduced-order models (EMC/thermal/electrical)

Design Rules

Toolkit library

Specifications

Inputs

Components/cellslayout

Reduced-order models (EMC/thermal/electrical)

Design Rules

Toolkit library

Pre-design(ideal circuit)

Specifications

Inputs

Components/cellslayout

Reduced-order models (EMC/thermal/electrical)

Design Rules

Toolkit library

Pre-design(ideal circuit)

(Auto) layout

Model generation

Circuit simulation

Validation

Implem

entation loop

Specifications

Inputs

Components/cellslayout

Reduced-order models (EMC/thermal/electrical)

Design Rules

Toolkit library

Pre-design(ideal circuit)

(Auto) layout

Model generation

Circuit simulation

Validation

Implem

entation loop

Manufacturing

Specifications

Inputs

Components/cellslayout

Reduced-order models (EMC/thermal/electrical)

Design Rules

Toolkit library

Pre-design(ideal circuit)

(Auto) layout

Model generation

Circuit simulation

Validation

Implem

entation loop

Manufacturing

Test

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Proposition – Expected Outcomes

What would we get?I Fully custom designs, as opposed to modularI Automatic Design for Manufacturing (fabless approach)I Single, well controlled technology:

Qualification: of technology rather than productsScalability: same technology for test and production runsPrototyping: share panels across projects

Ü Basically all the usual features in IC design.At what cost?

I Reduced choice of componentsI Must be in the toolkit library

I Reduced design flexibilityI The fewer degrees of freedom, the simpler the toolkit

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Proposition – Getting There

I Better design toolsI Large choice of existing software (PCB layout, circuit

simulators, EM modeling)I Need to identify suitable modelling approach

(speed/accuracy trade-off)I Software “glue” required for automatic model generation

I Define design rules for PCB embeddingI Required for automatic design validationI Long experimental work required.

I The impact on the supply chain must also be assessed

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Conclusions – Exploiting the PCB Embedding

I PCB embedding is very promisingI Provides a single, unified technology for

power electronics (W to 10’s of kW range)I High performanceI Scalable, reasonable cost. . .

I Situation comparable to microelec. in the 70’sI Many technologies available, but no standardI No separation between design and manuf.

Ü Need for Design Rules and uniformizationI Large effort required on the design tools

I Allow Design for ManufacturingI Objective: efficient virtual prototyping

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Bibliography I

J. W. Kolar, F. Krismer, and H.-P. Nee, “What are the big challenges in powerelectronics?,” in Proceedings of CIPS, (Nuremberg), 2014.

L. Kerachev, A. Andreta, Y. Lembeye, and J.-C. Crebier, “Generic approach fordesign, configuration and control of modular converters,” in InternationalExhibition and Conference for Power Electronics, Intelligent Motion, RenewableEnergy and Energy Management, (Nuremberg), pp. 212 – 219, VDE Verlag, May2017.

P. Waltereit, R. Reiner, B. Weiss, S. Moench, S. Muller, H. Czap, M. Wespel,M. Dammann, L. Kirste, and R. Quay, “Monolithic GaN power circuits forhighly-efficient, fast switching converter applications with higher functionality,” in9th WBG Workshop, 2018.

A. Letellier, Commutation de puissance haute fréquence basée sur la technologiea large bande interdite.PhD thesis, Université de Sherbrooke, Quebec, Canada, 2018.

A. Ostmann, “Evolution and future of embedding technology,” in IMAPS/NMIworkshop "disappearing die embed your chips", 2016.

E. Hoene, “Ultra Low Inductance Package for SiC,” in ECPE workshop on powerboards, ECPE, 2012.

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Bibliography II

Y. PASCAL, D. Labrousse, M. Petit, S. LEFEBVRE, and F. Costa,“PCB-Embedding of Power Dies Using Pressed Metal Foam,” in PowerConversion and Intelligent Motion (PCIM) Europe , (Nuremberg, Germany), June2018.

A. B. Sharma, D. Paul, M. Kreck, Y. Rahmoun, P. Anders, M. Gruber, andT. Huesgen, “PCB embedded power package with reinforced top-side chipcontacts,” in 2016 6th Electronic System-Integration Technology Conference(ESTC), pp. 1–5, Sept 2016.

Dupont., “Dupont interra embedded passives materials – interra HK04 planarcapacitor laminate,” tech. rep., Dupont, 2007.

J. Andresakis, “Embedded Capacitors,” presentation, Oak-Mitsui Technologies,Nov. 2005.

E. Waffenschmidt, B. Ackermann, and J. A. Ferreira, “Design Method andMaterial Technologies for Passives in Printed Circuit Board Embedded Circuits,”IEEE Transactions on Power Electronics, vol. 20, pp. 576–584, May 2005.

M. Ali, E. Labouré, F. Costa, and B. Revol, “Design of a hybrid integrated EMCfilter for a DC–DC power converter,” IEEE Transactions on Power Electronics,vol. 27, no. 11, pp. 4380–4390, 2012.

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Bibliography III

L.-A. Liew, C.-Y. Lin, R. Lewis, S. Song, Q. Li, R. Yang, and Y. Lee, “Flexiblethermal ground planes fabricated with printed circuit board technology,” Journal ofElectronic Packaging, vol. 139, no. 1, pp. 011003–011003–10, 2017.

J. S. de Sousa, P. Fulmek, M. Unger, P. Haumer, J. Nicolics, M. A. Ras, andD. May, “Enhanced in-plane heat transport in embedded mini heat pipes PCB,”International Symposium on Microelectronics, vol. 2017, no. 1,pp. 000130–000134, 2017.

R. Randoll, W. Wondrak, and A. Schletz, “Lifetime and manufacturability ofintegrated power electronics,” Microelectronics Reliability, vol. 64, pp. 513 – 518,2016.Proceedings of the 27th European Symposium on Reliability of Electron Devices,Failure Physics and Analysis.

R. Perrin, B. Allard, C. Buttay, N. Quentin, W. Zhang, R. Burgos, D. Boroyevich,P. Preciat, and D. Martineau, “2 MHz high-density integrated power supply forgate driver in high-temperature applications,” in Applied Power ElectronicsConference and Exposition (APEC), (Long Beach, United States), Mar. 2016.

R. Perrin, Characterization and Design of High-Switching speed Capability ofGaN Power Devices in a 3-Phase Inverter.PhD thesis, INSA Lyon, Lyon, France, 2016.

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Thank you for your attention

cyril.buttay@insa-lyon.frbruno.allard@insa-lyon.fr

Presented results were funded by Mitsubishi Electric ResearchCentre Europe, the French Agency for Technology and Research(ANRT) and Banque Public d’Investissement (BPI).

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