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Power Conversion Systems

Power Conversion Systems

Chargers, Converters, Inventers

AC/DC - DC/DC

Inverters

The AC/DC inverter functions to change the direct current (DC) of the battery into an alternating current (AC) which is used by the electric motor to move the vehicle. Additionally, the inverter on an electric vehicle is tasked with changing the AC current of the regenerative braking to DC current that is consequently used to recharge the battery. 


AC/DC inverters have sub components, each with its different story:

  1. High voltage power modules
  2. DC link capacitors
  3. SiC, Silicone Carbide TO packages
Inverter components require thermal interface materials that can keep up with the market trends and the ever changing requirements. These components are critical for the thermal design of power modules and can be a literal llife or death decision that has to be taken.

Market Trends and TIM Needs

  • High Power Density in Reduced Space
    • TIMs with better thermal performance 
  • Mechatronic Integration Design
    • TIMs with great conformability to surfaces 
    • TIMs with thin-bondline thickness 
  • Reliability is a Must
    • TIMs with long-term reliability
    • TIMs withstand harsh conditions


High Voltage power modules


Power modules consist of IGBT modules, MOSFET modules, IPMs and SIP modules. Power modules are used extensively in high power inverter applications.
Thermal management is crucial since more power always warrants more heat and hence more thermal dissipation needs. That's why we have a range of Thermal interface materials, made for power modules such as PTM-6000HV

Thermal Interface material Application considerations:

  • Excellent Thermal Performance
    • Low thermal resistance down to 0.04 ˚C·cm2/W
    • High thermal conductivity (up to 8 W/mK)
    • Optimal Surface Wetting & Low Contact resistance
    • Great conformability to fill up microscopic voids and cavities
  • High Reliability and Long-life
    • No bleed-out, pump-out and flow out issues
    • No aging effects including dry-out over time and degraded thermal performance 
    • Stable thermal impedance across accelerated aging test
  • Manufacturability
    • Easy assembly & broad process window
    • High yield with low/zero material waste
    • Pad and paste form factor

Phase change materials (PCM) are designed to minimize thermal resistance at interfaces and maintain stable performance through the rigorous reliability testing required for long product life applications. 

Their main benefits are:

  • Min BLT 20~30um
  • High thermal conductive
  • Non silicone based material
  • No pump out, bleed out, dry out issue
  • Superior long-term reliability
  • Stencil printable and dispensable


DC link capacitors

DC link capacitors can be either film or electrolytic capacitors that are used as plugins by being mounted directly on IGBTs. They have self healing capabilities, coming from their metallized dielectric propylene and can maintain an exquisite dielectric in harsh operating conditions and elevated temperatures. They need to be able to withstand temperatures up to 125°C for long operating periods of time.

Their self healing function ensures high reliability, high capacitance stability and a very limited capacitance loss throughout the product's life span. Among others, they can be used for DC/AC inverters for wind and solar applications and are commonly found in frequency inverters. These intermediaries reduce the power transfer noise during the AC source conversions and are crucial for the high power circuits that they are commonly used.


SiC TO packages

TIMS are not the only product category that has to be "custom made" for Power modules. High power requires not just dissipation but also thermally stable semiconductor materials that can withstand the rigourous thermal cycling requirements. These range from die attach, encapsulants and bonding wires to epoxy molding compounds.

Epoxy molding compounds such as the GR750 series and GR15F-MOD2C are made with power modules in mind. With exquisite thermal performance these compounds have a very high Glass transition temperature and easy pass HTRB tests while keeping high MSL levels. They are designed for high power devices with low moisture absorption requirements.

Epoxy Molding compounds application considerations:

  • Excellent Thermal Stability Pass thermal cycling test
    • High Tg as required
    • Low weight loss by TGA test and low thermal expansion
  • Excellent Electrical Stability  Pass HTRB test
    • Low ion content and low ionic mobility at high power condition
    • Stable ionic conductivity and permittivity at high temperature condition;
  • Reliability for SiC MOSFETs Packages Pass MSL test
    • Low moisture absorption 
    • Low storage modulus
    • Superior adhesion to lead frame
    • Low Coefficient of Thermal Expansion (CTE)
  • Environmentally Friendly
    • Green material without Br/Sb comply with RoHS;
    • Suitable for halogen-free devices defined by the Jedec JS709B;