Advanced packaging and integration solutions for enhanced performance power convertors

Solomon, Adane Kassa (2015) Advanced packaging and integration solutions for enhanced performance power convertors. PhD thesis, University of Nottingham.

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Abstract

The design of novel solutions for packaging and integration of power semiconductor devices to deliver switches with advanced performance and reliability is very important aspect of power electronics technology evolution. The advancement of technology in this area is committed to bring significant improvements in the design and implementation of power converters particularly in the enhancement of efficiency, higher power density and better cooling system as compared to the state-of-the-art solutions.

A power module is a combination of either multiple semiconductor or discrete devices which are connected to form an electrical circuit of certain structure. They are mainly constructed with a stack of four main parts (power semiconductor devices, insulating substrate with circuit conductor, baseplate, and interconnecting material encapsulated in a plastic case) and each of these parts is of a different material. Some of the interfaces within the module are prone to failure with thermal cycling such as wire-bond, solder die attach and substrate. Therefore reducing the number of interfaces in the assembly will greatly reduce the thermal resistance from the junction to ambient and yields noticeable increase of performance.

Moreover, using solid posts as opposed to wires to connect the surface of vertical power components enable a significant improvement in power density as compared with standard modules based on wire bond technology. Additionally, the replacement of wires with such posts drastically reduces the distributed parasitic inductance, together with double-sided cooling of the devices, results in an increase of performance and reliability of the components and assemblies.

In this work, 70um thick Infineon technology power devices which are rated at 600V/200A were used for the assembly of a Bi-directional switch based converter and discussing the challenges and trade-offs related to selecting processes and materials. Encapsulation is also one of the important factors in making of power module to protect the power chip and the interconnections from moisture, chemicals, dust, gases, and so on. Here, insulation process was carried out for a given prototype using silicone gel; however, it is worth to note the existing challenge on insulating a very small gap between the sandwich layers of the prototype as compared with the standard planar power module structure. A basic partial discharge test was also taken to demonstrate the performance of the insulation.

This research has presented an advanced modular integration approach for power device packaging demonstrating the progress beyond the state of the art in power system assembly by proposing a solution which significantly improves electromagnetic and thermomechanical performance of the power module. In particular, fully bond wireless, double sided cooling and layout symmetry are key aspects. The proposed approach is transferable to many topologies having extra benefit of restricting the impact of single device or switch failure on the general system accessibility.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Castellazzi, A.
Wheeler, P.W.
Johnson, M.
Keywords: Power semiconductors, Power electronics, Electric current converters
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7800 Electronics
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 30987
Depositing User: Solomon, Adane
Date Deposited: 15 Apr 2016 07:25
Last Modified: 05 Nov 2016 15:32
URI: http://eprints.nottingham.ac.uk/id/eprint/30987

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