Materials development for commercial multilayer ceramic capacitors
Promotion date: 17. November 2011
Promotor: Prof. dr. ing. Guus Rijnders
Assistant promotor: Prof. dr. ir. André. ten Elshof
Multilayer ceramic capacitors are mainly used in today’s electronic devices and these types of capacitors are discussed in this thesis. The components are made up of a body, in which alternating layers of dielectrics and conducting electrodes are embedded.
In the 1980s and 1990s the majority of multilayer capacitors were made with expensive noble metals like palladium or platinum. Due to the price increase the passive component industry started to develop new dielectric materials suitable for co-firing, with less expensive noble metals like pure silver or silver-palladium alloys.
Another way to decrease metal costs is to implement base metals
like nickel and copper as electrode material. Therefore new types of dielectric materials had to be developed in order to be co-fired with nickel or copper in a reducing atmosphere to prevent the metals from oxidizing.
The multilayer ceramic capacitors are already produced with low cost metals, in particular nickel electrodes. Development is mainly focused on increasing the capacitive volume efficiency by decreasing the dielectric layer thickness and by maximizing the number of electrodes layers. Various strategies are described to
make high capacitance multilayer capacitors.
How did you come across the idea of studying multilayered capacitors?
From the start of my career, starting in 1996 at Philips Research in Aachen, I worked on ceramic materials in electronic devices. Two years ago I started writing my thesis report after working for about 10 years in Roermond, at Philips and Yageo. In Roermond, multilayered capacitors were at the core of my R&D research activities at various companies, including Yageo.
While cooperating with the Inorganic Materials Science group, Professor André ten Elshof invited me to do the PhD-research on this interesting research topic, having great application value.
The route I came to writing my thesis work was far from usual, it is fair to say.
Did you feel part of the Mesa+ team while working at the company most of the time?
A vast amount of the data I gathered while working on materials for multilayered capacitors. However, important scientific questions arose here. Some of the important scientific questions for making reliable multilayer ceramic capacitors, are touched by my work and some design rules and new materials are proposed in the thesis, based on the information gathered during my working life at a company. However, I got the possibility to do extra research to answer some open questions related to capacitor material design and put some ideas for new types of dielectric ceramic materials to achieve high permittivity values.
I spent eight months doing additional experiments and analyses at the IMS group, also collaborating with Professor Ian M. Reaney at the University of Sheffield.
In this period I am proud to have come up with a set of design rules to construct robust capacitors, using multilayers in which less palladium is needed in a reliable way. A different route of synthesis is presented also.
What did you learn by spending this time as an academic researcher?
I was not used to incorporate literature writings into my own research and seeking ways to incorporate these into my own results. By doing so I learned to design and perform research in a new way, starting from a secure knowledge base.
Also I learned new experimental skills, which I can use in my current work and in the future, while working as a R&D scientist.
What are your future plans?
At Philips, I work on new phosphors usable in LED lighting systems. Chemistry, materials and process development are part of my responsibility. Although long term strategy is involved, most of the innovations will be in products coming to the market in about a year time.
In your opinion, what is important for Mesa+ to stay successful?
Next to working with IMS, also I had a good cooperation with the Materials Science group making my analyses. The accessibility of different experts and expertises from different groups and the easy way of cooperating with them is to be cherished.
A little concern to me is the ambition of young PhD students. Most of them like to work as a post-doc after they finish. Little they know about the way research is carried in company environments. In my opinion it is a good thing if these students work within such an environment for a few months, collaborating in related research while being of some practical use for these companies. PhD student should see it as their responsibility to try and become aware of the way R&D is taking place in commercial companies during their PhD working period.