Fraunhofer Institute for Integrated Systems and Device Technology IISB

Packaging for Electronics

Ceramic Embedding

Using the various advantages for Wide Band Gap semiconductor devices, we investigate concepts that exhibit planar contacts, low parasitic inductance, high voltage, high design flexibility, environmental compatibility and high temperature suitability.

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Motivation for Ceramic Embedding:

Miniaturization & no housing, 3D-integration, reduction of connection points
High switching & short current paths, vias instead of bond wires, low parasitic inductance
More efficient cooling & double-sided cooling, thermal vias

High temperature capability (> 200 °C)
High thermal conductivity (Al2O3, AlN, Si3N4)
High current carrying capability (Cu layer > 300 µm), no wires
High corrosion resistance (ceramic)
Low CTE-Mismatch

Ultra Short Pulse Laser Structuring

Easy DBC designing on demand
Cost effective and fast prototyping
Super fine lining
Electrical field control
Limitless trench layout for insulation
3D structuring of organic, inorganic and metallic materials
Reverse engineering

Wire Bonding

Using new materials for bond wires like copper, composites, or alloys, we aim for improvement of the application’s lifetime. Furthermore, by bonding parameters, geometry, material, and others, we cover every power electronics application. For best bondability, we also benefit from using metallization and surface optimization of semiconductors.

Wedge-Wedge

Ball-Wedge

Wire bond materials: aluminium, copper, aluminium composites, gold

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Wire Bonding - topside connection for semiconductors (iisb.fraunhofer.de)

Research fields

New materials for bond wires like copper, composites, or alloys
Improvement of application’s lifetime by bonding parameters, geometry, material, and others
Metalization and surface optimization of semiconductors for best bondability
Cleaning process to achieve a reliable bond connection
In combination with power cycling tests a correlation between bonding parameters to lifetime is possible
Aluminum and copper wedge-wedge-bonding with diameters from 100μm to 500μm possible
Ribbon bonding
Gold ball-wedge bonding with diameters from 25μm to 75μm possible
Heatable work holder for bond process under temperature for up to 200°C
Quality assurance through pull and shear tests
Control of reliability and lifetime by active power cycling test, passive temperature cycling and vibration tests
Design of experiments to find best suited bonding parameters

Add-on: Vias in DBC Substrates for embedded power modules

Novel Via manufacturing approaches

Laser drilling, stencil printing, dispensing, mechanical contacting
Copper paste, copper rivets, silver paste

Die Bonding

Our portfolio of services contains all standard soldering techniques for chip attachments, as well as pressureless and pressure assisted sintering and next-generation silver direct bonding techniques for 3D power integration.

Silver direct bonding is an innovative die-attach technique for 3D power integration. This technology allows micro-structured devices with thin metal films to be joined together without an intermediate layer. Normally, the direct bond is formed completely under solid-state conditions without liquid phase. In case of silver finish, direct bonds exhibiting high bonding strength and good interlayer electrical conduction can be already obtained at low temperature and pressure.

TOP SIDE LEADFRAME

Lifetime 17x
Metallization of off the shelf devices
Ag-Sintering, top and bottom chip contact
Pressure assisted process
Pressure less process
Stress relieving measures

Download product Sheets and Articles as PDF:

Packaging for Electronics (iisb.fraunhofer.de)
CTE Management (iisb.fraunhofer.de)
Article - Annual report 2018: Power electronics meet fine pitch - Direct bond Technology (iisb.fraunhofer.de)

Silver sintering

Pressureless and pressure assisted (up to 75kN) process for small and large areas
Single and double sided semiconductor devices
Multichip power modules using pre attaching
Selective sintering on populated circuit boards
Sintering of active and passive components
Sintering on DCB, PCB, and leadframe
Screening of different sinter material

Soldering

Standard lead free tin based and high temperature alloys
Void free soldering with paste and preform material

Direct Bonding

Summary:

No intermediate layer
Reduced assembly process steps
Reduced process costs
Fine pitch
Very high bonding strength made for power electronics

Prototypes

Full SiC Double Sided Busbar Module

Idea of concept

Low inductance and high temperature power module for e-drives
Fast switching with SiC
DC+ & DC- on outer metalliztion for lowest parasitic C to ground
High reliability and temperature capability by silver sintering
Low cost due to copper busbars with hybrid polymer isulation layers instead of DBC substrates
Double sided cooling, high thermal capability

Download Product Sheet "Full SiC Double Sided Busbar Power Module"

Further examples of our prototypes

© Fraunhofer IISB
Head spreading and CTE matching by graphite

© Fraunhofer IISB
Double sided cooled sintered power module

© Fraunhofer IISB
Double sided silver sintering of power semiconductors

Equipment & Laboratories

We operate our own clean room according to ISO classification 7 and futher laboratories for analysis and lifetime testing.

Due to our membership in the Research Fab Microelectronics Germany (FMD), we operate an advanced packaging line for power electronics, as well as an environmental laboratory for power electronics - components and systems.

Stencil printer and Ink-jet printer for sinter and solder pastes as well as printing polymers and thermal interface materials in the packaging clean room

Forschungsfabrik Mikroelektronik Deutschland (FMD) (iisb.fraunhofer.de)

Equipment

Multi-physics simulation tools (electro-thermo-mechanical), CAD
Plasma cleaning
Printer for paste material
Vapor-phase vacuum soldering
Formic-acid-activated IR vacuum reflow
Hydrogen activated IR vacuum reflow
Full automatic die placer with high temperature and extended tool force capability
Automatic wire and ribbon bonders (Al, Cu, Au)
Servo press for sintering
Ultrasonic and resistance welding machines for electric terminals