sensor report 3-2010

3-2010 sensor report

For years now Heraeus Sensor Technology a division of W.C. Heraeus has been a technology and

market leader in the broad ﬁ eld of high quality temperature sensors. Manufactured in platinum thin-

ﬁ lm technology, several tens of millions of sensors leave the factory in Germany‘s Kleinostheim each

year. They are destined for continuous use in process technology, in exhaust systems, ovens, buil-

dings or also in calibration laboratories. The accumulated knowledge and expertise, as well as the

setting up of production plants, are now returning extremely positive initial experience in new ﬁ elds

of application. We were able to learn about this early experience from the Division Manager and

General Manager of Heraeus Sensor Technology Dr. Martin Turwitt and the Director for Marketing

& Sales, Dr. Gerold Kerkhoff.

Sensor Components Division grows into new markets

Beyond Temperature

Sensors

Which properties make platinum such an extraordinary

material?

TURWITT. We basically exploit two of the special properties of

platinum. One is the almost linear characteristic of the tempera-

ture dependence of conductivity which makes platinum the ideal

material for resistance temperature sensors. The second reason is

that platinum really earns its classification as a noble metal. It is

particularly inert in reactions or, to put it positively, it is resistive

to corrosion with other materials.

KERKHOFF. We have special expertise in the use of platinum as

a sensor – correctly packaged – for applications in the high tem-

perature range up to 1,100°C. This is where one of our strengths

lies, for example with the use of our temperature sensors or flow

sensors in exhaust systems.

We have used the property of its inertness as a noble metal for a

long time now, particularly in biosensors, where it is important

that no chemical reaction whatsoever occurs between the sensor

and any substances.

How did you come from the passive layers of tempera-

ture sensors to the active layers of heaters and therefo-

re to sensors for gases and mass flow rate?

TURWITT. The measurement principle of the anemometer is now

very old, but formerly thin films were not used. And then came

the requirement from the automotive industry to measure the

mass air flow rate for optimising the combustion. Here, we were

able to apply our expertise in thin-film technology and enter very

decisively with a solution. Today this task is carried out by a sili-

con component. It does not function however in the high tempera-

tures of the exhaust system, so that we were able to offer a soluti-

on with our platinum technology.

Where do you see the opportunities of employing plati-

num films other than in temperature and flow?

TURWITT. Thin films are, of course, very widely used. You will

also find our platinum films in biosensors, for example. This ena-

bles, say, cell growth under the influence of various medicaments

to be observed. Or water quality can be monitored via the degree

of algae formation. Projects are running in co-operation with the

University of Munich in this respect.

The sensors involve not only the deposition of the platinum, but

also thin films of other metals and oxides. Here, we are moving

away from the field of platinum films and are working with comple-

tely different materials – but still in the form of thin films. Where

required, these can also be magnetic, optical or gas-sensitive films.

Of course, our processes extend still further. Here, they cover the

micro-structuring of these films, protective coatings and contac-

ting.

Does this mean that in future you will also be able to

establish thin-film processes which are not based on pla-

tinum?

TURWITT. Exactly. They can be other metals or oxides – inclu-

ding ceramic thin films. We modify the initial materials to manu-

facture products other than temperature and flow sensors in large

quantities using our process experience and our machines. We

certainly have the appropriate specialists for this.

KERKHOFF. We are increasingly making use of the combination

of our technological possibilities and our special material experti-

se to go beyond temperature sensors. Through the integration of

micro-heaters and high-temperature stability sensor structures on

one chip we are developing and producing customised solutions

for tasks in gas and particle sensors. In our biosensors we are al-

ready now integrating oxygen and pH sensors which are not ma-

nufactured in platinum.

So far we have been talking about substrates of alumini-

um oxide. Along with other thin-film materials, do other

substrates also play a role?

TURWITT. The most obvious are of course other oxides, such as

zircon oxide, which almost behaves the same in a vacuum, that is,

it does not evolve gases nor evaporate. Various types of glass are

of special interest for biological chips. Here, it is often necessary

to carry out supplementary observations with an optical micro-

scope, so transparent materials are needed. We are supplying all

this already.

KERKHOFF. When a customer comes to us with a concrete pro-

duct design and specifies the substrate and coating materials,

then we develop the appropriate process. Usually though, the cus-

tomer has a sensor problem and is seeking a company that will

make a suitable selection of materials and develop a functioning

layout for the sensor structure. Between the conflicting priorities

of product requirements, product manufacturing feasibility and

economic efficiency, we develop a solution for customers based on

the most suitable combination of materials. Often we are included

in a development project if it entails the transfer of research pro-

ducts into large scale production. In this respect we have not only

our own laboratories at our disposal, but we also have access to

extensive expertise in metals, in quartz glass or ceramics within

the Heraeus Group. For almost all technically relevant materials

we have specialists within the group who are available.

What happens in the further processing of the coated

components?

TURWITT. Normally, our products start in clean rooms with

cleaning and coating processes and finish with screen printing

COVER STORYCOVER STORY

processes, for example for the protection of thin films by glass or

for the manufacture of, for example, conductor or contact tracks

with the relevant subsequent oven processes. This all means that

we have also accumulated lots of expertise in the field of thick

films. Usually, the combination of thin and thick films produces

the desired solution.

After that first comes the contacting. For temperatures up to about

600°C we use thermobonding, but we also have various welding

and brazing methods for higher temperatures. Then, as applicable,

mechanical processing steps follow, such as welding or sawing

and other assembly steps. Finally, we can manufacture products

which are completely encased. However, this is not our primary

objective. We want to manufacture sensor elements or semi-fabri-

cated sensors which are then processed further by our custo-

mers.

Going beyond production, what fields of competence can

Heraeus Sensor Technology offer?

TURWITT. We are certainly keen to take up general enquiries

from customers in the direction of technology, market situation or

portfolio, etc. and elaborate on them. Here, it may also transpire

that it is better, for example, to first make contact with an institute

to clarify certain steps. We also undertake one or the other basic

research project if it is evident that at the end of the day it might

lead to the large-scale production of a component.

KERKHOFF. Often these are projects which involve product feasi-

bility. We particularly see ourselves at the interface between basic

research and large-scale production. That is often a long path. Es-

pecially interesting for us are products matching our product

spectrum which have been developed by industrial companies to-

gether with research establishments. When the question arises

after the development phase: Who can now produce for the mar-

ket? Then with our facilities, we are the right company to contact

for developing large-scale production processes – through to the

inspection specifications for the customer‘s end product and the

appropriate training.

L103106

www.heraeus-sensor-technology.com

gerold.kerkhoff@heraeus.com

AUTHOR. The questions were put by the Chief Editor, Dr. Ger-

hard Weissler.

In discussion at Heraeus Sensor Technology (from the left) General

Manager Dr. Martin Turwitt, SR Chief Editor Dr. Gerhard Weissler and

Dr. Gerold Kerkhoff, Director for Marketing & Sales: «Especially

interesting for us are products matching our product spectrum which

have been developed by industrial companies together with research

establishments....»

ABSTRACT

Seit Jahren gehört Heraeus Sensor Technology zu den

Technologie- und Marktführern im weiten Feld der hochwer-

tigen Temperatursensorik, hergestellt in Platin-Dünn-

schichttechnik. Das Unternehmen bietet jetzt kundenspezi-

fische Lösungen für mikrostrukturierte Dünnschicht- oder

Dickschicht-Systeme. Der Produktbereich erstreckt sich

von hochtemperaturstabilen resistiven oder kapazitiven

Sensoren über Mikroheizer bis zu Multisensorlösungen für

Anwendungen in den Lebenswissenschaften, der Bio- und

Gassensorik. Besonderes Interesse gilt der Überführung

von Prototypen in die Serienfertigung. [gaw]