15-11-2012, 05:17 PM
IPEM
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ABSTRACT
IPEM is an improved power processing technology through advanced
integration of power electronics components. It provides high frequency synthesis,
resulting in important improvements in performance, size, and cost.
Currently, assemblies of power semiconductor switches and their
associated drive circuitry are available in modules. Though the module contains a
small size power switching part, the associated control, sensing, electro magnetic
power passives and inter connect structures are very bulky. In IPEM, the reduction
in size and weight is provided by planar metalization that allows 3-D integration
of power devices and power passives to increase the power density.
This paper addresses the improvements of power processing technology
through advanced integration of power electronics. The fundamental functions in
electronic power processing, the materials, processes, and integration approaches
and future concepts are explained.
INTRODUCTION
In power electronics, solid-state electronics is used for the control
and conversion of electric power .The goal of power electronics is to realize
power conversion from electrical source to an electrical load in a highly
efficient, highly reliable and cost effective way. Power electronics modules
are key units in a power electronics system. These modules contain
integration of power switches and associated electronic circuitry for drive
control and protection and other passive components.
During the past decades, power devices underwent generation-bygeneration
improvements and can now handle significant power density. On
the other hand power electronics packaging has not kept pace with the
development of semiconductor devices. This is due to the limitations of
power electronics circuits. The integration of power electronics circuit is
quite different from that of other electronics circuits. The objective of power
electronics circuits is electronics energy processing and hence require high
power handling capability and proper thermal management.
Most of the currently used power electronic modules are made by
using wire-bonding technology [1,2]. In these packages power semi
conductor dies are mounted on a common substrate and interconnected with
wire bonds. Other associated electronic circuitries are mounted on a multi
layer PCB and connected to the power devices by vertical pins. These wire
bonds are prone to resistance, parasitic and fatigue failure. Due to its two
dimensional structure the package has large size. Another disadvantage is
the ringing produced by parasitic associated with the wire bonds.
FEATURES OF IPEMS
The basic structure of an IPEM contains power semi conductor
devices, control/drive/protection electronics and passive components. Power
devices and their drive and protection circuit is called the active IPEM and
the remaining part is called passive IPEM. The drive and protection circuits
are realized in the form of hybrid integrated circuit and packaged together
with power devices. Passive components include inductors, capacitors,
transformers etc.
The commonly used power switching devices are MOSFETs and
IGBTs [3]. This is mainly due to their high frequency operation and low on
time losses. Another advantage is their inherent vertical structure in which
the metalization electrode pads are on two sides. Usually the gate source
pads are on the top surface with non-solderable thin film metal Al contact.
The drain metalization using Ag or Au is deposited on the bottom of chip
and is solderable. This vertical structure of power chips offers advantage to
build sand witch type 3-D integration constructions.
DPS SYSTEM
The complete circuit diagram of DPS system is shown in figure 1. In
this DC-DC converter, the primary dc supply is split in with the help of
capacitors and then inverted to high frequency ac by MOSFET by half
bridge inverter. The resonant capacitor voltage is transformer coupled,
diode rectified and then filtered to get the output dc voltage [6].
Embedded Power stage
The core element in this structure is the embedded power stage that
comprises of ceramic frame, power chips (Si in figure), isolation dielectric
and metalization circuit. Inside the power stage, multiple bare power semi
conductor dies, featuring vertical semi conductor structures with topside and
backside electrode pads, are buried in a ceramic frame.
Planar metallization
In this module, wire bonds are replaced b metalization using copper
layers. It is shown in figure 3. Here the deposited Cu pattern layers connect
the Al pads of the power chips with external circuitry.
PERFORMANCE OF IPEM
The performance of IPEM can be evaluated using various parameters. A
comparison of IPEM and wire bonding technology is given in table 2. As given in
the table, IPEM has achieved 35% reduction of foot print area as compared to the
wire-bonding version. The planar interconnects in IPEM reduces the structural
inductance by a factor of three when compared to the wire bonding. But the
structural capacitance is increased by a factor of five.
CONCLUSION
In power electronics modules further improvements in performance,
reliability and cost can be achieved by using IPEMs. Various experiments have
proved its manufacturability and other features of this technology. The impacts of
system integration via IPEM will enable a rapid growth of power electronics that
can be compared to the impacts in computer applications brought about by VLSI
technology.