Packaging for Electronics

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

Wire bonding

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

 

Our services

 

  • 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

 

Functional principle

 

  • Ultrasonic bonding works with high-frequency acoustic vibrations under pressure and creates a solid-state welding
  • For aluminum wedge-wedge-wire bonding ultrasonic energy is applied to the wire for a specific duration while being held down by a bond force
  • Thermosonic gold bonding includes heat treatment and can be used to form solid-state bonds below the melting point of the mating metals
  • For ball-wedge-bonding, a gold ball is formed before the bonding process by melting the end of the wire via high voltage

 

Devices and packaging

 

  • Power Electronic Modules
  • Single Semiconductors
  • Si, SiC and GaN devices
  • Surfaces providing best weld solutions: Aluminum, copper, gold and silver

 

Bonding machine features

 

  • Semi-automatic bonding process
  • Programmable bond layouts
  • Deformation limit control
  • Image recognition of semiconductors and substrates
  • Large area modules as well as small micro electronic devices bondable
  • Fast switching of bond heads and pull/shear heads
© Fraunhofer IISB

Gold wire (25µm)

© Fraunhofer IISB

Copper wire (250µm)

© Fraunhofer IISB

Aluminum wire (125µm)

Prototyping

  • Material selection including housing and potting
  • procurement of material
  • Small-scale production
© 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

Testing

  • Static thermal measurements from chip to coolant
  • Dynamic thermal measurements
  • Static electrical characterization
  • Dynamic switching characterization
  • Scanning acoustig microscopy
  • Shear, pull, peel test
  • Active Power Cycling
  • Passive Temperature Cycling

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
© Fraunhofer IISB

Cross section of a silver sintered bond line

© Fraunhoer IISB

Cross section of an aluminium-zink bond line

© Fraunhofer IISB

Cross section of a gold-germanium bond line

 

Packaging
For Electronics

[ PDF  0.22 MB ]

 

Wire Bonding

[ PDF 0.22 MB ]

 

CTE Management - Graphite Material for Power Modules

[ PDF  0.22 MB ]

 

Full SiC Double Sided Busbar Module

[ PDF  0.45 MB ]