Thermosets

in cooperation with LS Polymeric Materials of BTU Cottbus – Senftenberg

Development of multifunctional polymers based on SOLID process

SOLID-Process

Deposition (film formation) of polymer parylene onto a lquid substrate

Chemistry

Reaction of monomers and polymers (vinyl- or acrylate polymers, polymers containing perfluorvinylidene groups) with intermediate III to modify parylene. Encapsulation of liquid crystal mixtures using parylene.

Characterization

FT-IR-ATR-spectroscopy, NIR spectroscopy, Raman spectroscopy, UV-VIS spectroscopy, refractive index determination

Applications

Polymer based operational devices, optical wave guides, organic transistors (OFET), organic light diodes (OLED, PLED), flexible displays, organic solar cells

in cooperation with LS Polymeric Materials of BTU Cottbus – Senftenberg

Miniaturization of microelectronic components requires the development of novel insulation coatings with low dielectricity constants of k< 4 (low-k-dielektrika), while so-called ultra-low-k materials with k < 2.4 are aimed for. In principle there are two ways to lower the dielectricity constant:

• Lowering of the polarizability (dipole strength) through use of substances with less polar bonds such as C-C, C-H, Si-F and Si-C bonds.
• Lowering of the density (dipole density) via creation of free volume and/or generation of locally confined pores.

The aim of this project was the development of novel low-k polymer materials with larger free volume on the basis of polycyanurate and perfluorocyclobutane (PFCB) polymers. These novel low-k polymers are produced without generation of pores by inclusion of bulky monofunctional structural elements to increase free volume. This avoids the described problems of integration for porous materials during processing.

Result

The dielectricity constant could be lowered to presently k = 2.51 for a polycyanurate copolymer with a large percentage of monofunctional components. The good mechanical and thermal properties of polycyanurates were retained. The current industrial requirements for low-k materials with with respect to leakage current density (< 10^-9 A/cm) and breakdown field strength EBD (> 3 MV/cm) were met. In addition, an adapted processing sequence was developed and applied successfully to the basic polymer. These results are a very promising basis for the successful integration into a copper metallization.

References

This project (01.07.2002 - 31.12.2006) was funded by the DFG (BA 1168/10 – 1) and carried out in cooperation with the Chair in Microtechnology of the Faculty for Electrotechnology and Information Technology at TU Chemnitz.

Publications

K. Schulze, U. Schuldt, O. Kahle, S. E. Schulz, M. Uhlig, C. Uhlig, C. Dreyer, M. Bauer, T. Gessner: Novel Low-k Polycyanurates for Integrated Circuit (IC) Metallization, Microelectronics Engineering 82 (3-4), p. 356-361 (2005)

C. Dreyer, J. Schneider, N. Keil, C. Zawadzki, H. H. Yao, U. Schuldt, K. Schulze, O. Kahle, S. E. Schulz, M. Uhlig, C. Uhlig, C. Boeffel, T. Gessener, M. Bauer: Material Development for Integrated Optics, Microelectronics and Display-Technology - Selected Examples, MicroSystem Technologies 2005, H. Reichl (ed.), ISBN 3-7723-7040-3, p. 455-462 (2005)

C. Dreyer, M. Bauer, J. Schneider, C. Boeffel, O. Kahle, C. Uhlig, U. Schuldt, N. Keil, H. H. Yao, C. Zawadzki: Fluorinated Polymers for High-Performance Applications, Science for Innovation, Brüssel (B), 04./05.10.2005

K. Schulze, U. Schuldt, O. Kahle, S. E. Schulz, M. Uhlig, C. Uhlig, C. Dreyer, M. Bauer, T. Gessner: Polycyanurates – A Low-k Material Approach, European Congress on Advanced Materials and Processes EUROMAT, Prag (CZ), 5.-8.9.2005

Results

Reactive resin systems based on cyanate esters and epoxides are used as adhesives, underfillers and capping materials for electronic components. The property profile of these reactive resins is sufficient for many areas of application, however with the continuous advance of the technology there is an urgent need for improvement of their processing and end characteristics.

To overcome the discrepancy between too short pot lives (less than 8 hours) and too long curing times (e.g. 175 °C for over 1 hr), we encapsulate small particles (order of magnitude about 10 µm) of effective curing systems, to suppress the curing reaction at room temperature. In this way 1K mixtures of a liquid cyanate ester with encapsulated curing agent reach a pot life of more than 3 months; in contrast resin with non-encapsulated curing agent will gel after only 30 min at room temperature.

The structure of curing agent and capsule can be adjusted so that the capsules open at a specific temperature, starting the reaction of the curing agent with the resin. In this way low temperature systems with curing times of about 5 mins at 80°C glass temperatures of about 140 °C, while another resin/curing agent system will reach a glass temperature of 220°C after only 10 seconds curing time.

The developed snap-cure base systems can be formulated with common additives such as mineral fillers, tougheners, metal powders and others, to cover the wide area of processing and end characteristics for adhesives, underfillers, capping materials and similar.

Applications

Adhesives, underfiller, capping material

Publications

J. Bauer, M. Bauer: Cyanate Ester Based Resin Systems for Snap-Cure Applications, Micro System Technologies 2001, Düsseldorf, 27.-29.03.2001.

Research into the potential of plasma polymerization as a method for pretreatment of metal surfaces for bonding and coating.

Results

Synthesis of new monomers for plasma polymerization

Low network densities were achieved at low plasma energies (~10W RF):

• large CTE (typical for rubber state)
• large sol fraction
• low temperature resistance
• high water uptake

High network densities were achieved at high plasma energies (pulsed DC):

• CTE (typical for glass state)
• layer contains no measureable amount of sol
• temperature resistance to >300°C
• low water uptake

It was shown with plasma polymers from acrylic acid (AA) as an example, that addition of ca. 25% octadiene the optimum characteristics are achieved (reduction of sol-fraction, increase of thermal stability, reduction of water uptake).

References

This project was funded by the European Union (Brite EuRam, Contract No: BRPR 97-0582, Project No: BE97-4013) and carried out in cooperation with:

• British Aerospace, Sowerby Research Centre, Bristol (GB)
• University of Sheffield, Sheffield (GB)
• Profactor GmbH, Steyr (A)
• Instituto Superior Técnico, Lissabon (P)
• Rübig GmbH & Co. KG, Wels (A)

Publications

D. B. Haddow, A. Goruppa, J. Whittle, R. D. Short, O. Kahle, C. Uhlig, M. Bauer: The Application of Variable Temperature Ellipsometry to Plasma Polymers: The Effect of Addition of 1,7-Octadiene to Plasma Deposits of Acrylic Acid, Chemistry of Materials 12(4), p. 866-868 (2000)

Principle

Poly(melamine) dendrimers are of special interest, as they combine the positive characteristics of dendrimers (e.g. defined molecular structure, ideally branched structure, better solubility compared to analogous linear structures) with the specific properties of melamines (e.g. temperature resistance, improved adhesive properties). The dendrimers can be produced via divergent (i.e. growing outwards from a core) or convergent (i.e. beginning with the outer sphere and growing inwards) synthesis. This happens via a repetitive synthetic sequence, which consists of the following steps (in case of divergent synthesis):

1. Reaction of a derivative of cyanuric acid (preferably 2,4,6-trisphenoxy-1,3,5-triazine) with excess di- or triamine or with diamine protected on one side; followed by removal of excess/deprotection.
2. Reaction of free amino-groups with another cyanuric acid derivative. Because of the staggered reactivity of the substituents on the triazine ring the cyanuric acid derivative can be added in nearly stoichiometric quantities under suitable reaction conditions.
3. Repeat of steps 1 and 2 and/or modification of the dendrimer outer sphereby reaction with a monoamine, which can have additional functional groups.

The convergent synthesis proceeds in the following steps:

1. Reaction of two of the three functional groups of the cyanuric acid derivative with a monofunctional amine, which makes up the dendrimer outer sphere
2. Reaction of the third functional group with a partially protected diamine or excess diamine and removal of excess or protecting group
3. Reaction of the free amino groups of two equivalents of the product from step 2 with more cynuric acid derivative
4. Repetition of steps 2 and 3

Through choice of the monofunctional amine component the outer sphere of the dendrimers can be modified and their properties adjusted to a wide range of applications. For example, dendrimers can be synthetised with unsubstituted alkyl groups of varying chain length, or with hydroxyl- or amino-groups in the outer sphere.

Applications

• Polyfunctional cross-linkers e.g. for polyurethanes, EP-resins or similar
• Modification of stationary phase in chromatography
• Carrier for active ingredient in pharmacy or cosmetics

Scientific Achievement

Dendrimers with covalently bound, heteroaromatic branching units were previously unknown. Their Synthesis enabled access to new materials which combine the advantages of dendrimers with those of poly(melamine).

References

The work was carried out as an in-house research project.

Publications/Patents

J. Bauer, M. Bauer, J. Neumann: Poly(melamin)dendrimere und Verfahren zu ihrer Herstellung
DE 195 28 882 A1

J. Neumann-Rodekirch, J. Bauer, M. Bauer: Stationäre Phase für die Chromatographie
DE 196 21 741 A1

J. Neumann-Rodekirch: Darstellung und Charakterisierung von hochverzweigten, molekulareinheitlichen und molekularunheitlichen Polymelamin-Strukturen, zugl. Diss., Universität Bremen, PhD-Thesis (1997).

C. Dreyer, F. Reetz: Untersuchungen zur Einlagerung von Fulleren C60 in Lipiddoppelschichten mittels Differential Scanning Calorimetry, zugl. Dipl., Universität Kaiserslautern, Diploma Thesis (1996).

J. Neumann-Rodekirch, C. Dreyer, J. Bauer, M. Bauer: Polymelamin-Dendrimere, Vortragstagung »Neue Horizonte in der Polymerchemie«, Mainz, 23./24.03.1998.

M. B. Steffensen, E. Hollink, F. Kuschel, M. Bauer, E. E. Simanek: Dendrimers based on [1,3,5]-triazines, Journal of Polymer Science. Part A: Polymer Chemistry 44(11), p. 3411-33 (2006)

Results

Friction brake pads are relevant components to safety in the automotive industry. Due to increased requirements to performance and safety it is necessary to develop brake pads with higher thermal stability and more convenience. The polymeric rheological additive of the multicomponent system brake pad and the structural adhesive are essentials in this task. Based on modern high-temperature-stable thermosets, the novolak-based cyanate esters, fundamental work on structure, reaction and characteristics of the resins and thermosets has been done as well as product-related developments of rheological additives and structural adhesives. In addition to the improvement of the brake pads' characteristics the production technology can be simplified, shortened and made more cost-effective.

Application Area

Automotive industry

Co-operation

The work has been done in Co-operation with:

• Perstorp AG
• Lonza AG
• TMD Friction

Patent

M. Bauer, J. Bauer, P. Severit: Cyanatbasierte Klebstoffe für und in Kombination mit Reibbelägen sowie Verfahren zum Herstellen von auf einer Unterlage haftenden Reibbelägen (2000)
DE 100 19 475.3

Results

Thermo-optic (TO) switches are important components for fiberoptic communication as switch components and optical routers. By using the advantages of two different types of material – silicon with ultra-low optic loss and specially adjusted polymers with high TO-coefficients and low thermal conductivity – we designed a novel polymer/silicon hybrid concept, where a planar SiO₂ wave guide is used exclusively for optic transport, while a planar polymer wave guide takes on the TO switch function. A vertical coupling schematic was developed to produce these hybrid elements. We produced and tested a hybrid polymer/silicon 1x2-coupler with less than -30 dB polarization independent crosstalk, low extrinsic junction loss (1,5 dB),  low breaking capacity (30 mW per switch element) and low dimensions. Furthermore, using these 1x2 switches as the basic unit we developed an integrated hybrid polymer/silicon 1x8 switch matrix with less than -24dB polarization independent crosstalk . This hybrid concept is also interesting for other thermo-optic components like tuneable filters and optic dampening elements. In addition the packing density of the optic elements on the chip could be increased, a basic prerequisite for the building of large switch matrices.

Application

Integrated optics and optoelectronics

Cooperation

The work was carried out in close cooperation with the Fraunhofer Institute for news technology, the Heinrich-Hertz-Institute and the Alcatel Corporate Research Center Stuttgart.

Publications

N. Keil, C. Weinert, W. Wirges, H. H. Yao, S. Yilmaz, C. Zawadzki, J. Schneider, J. Bauer, M. Bauer: Thermo-optic vertical coupler switches using hybrid polymer/silica integration technology, Electronic Letters 36, p. 430 (2000)

N. Keil, H. H. Yao, C. Zawadzki, K. Lösch, K. Satzke, W. Wischmann, J. Schneider, J. Bauer, M. Bauer: Hybrid polymer/silica vertical coupler switch with <-32dB polarisation-independent crosstalk, Electronic Letters 37, p. 89 (2001)

Principle

Within the optically active polymer light conductors are produced, which are separated for a short distance into two symmetrical paths. In one path the optical properties of the material are changed by the applied electric switching voltage, while the other path remains unchanged. When light hits the entrance of the modulator, if the switching voltage is applied, there is no light at the exit of the modulator, due to overlay of the two parts of the beam. When the electric voltage is switched off, it becomes light. These are the closed and open positions of the modulator.

Applications

The developed electrooptical switch can be used in integrated optics and for the modulation of very short light impulses, which are important for high bit rate data transfer.

The information to transmit is digitally coded by the voltage impulses and are transformed directly into digital optical signals. With these modulators switch frequencies of over 10 GHz can be reached without difficulty. Therefore the data transfer rate of conventional methods can be improved by a factor of 100.

Scientific Achievement

Novel NLO-polymers were developed which enabled the construction of an electro-optical switch with the following core data:

• Electrooptical coefficient r₃₃ = 12-20 pm/V @ 1320 nm
• Thermal stability of  r₃₃ smaller than/equal to 5 a @ 80°C (T_g = 155-170°C)
• Optical loss greater than/equal to 1 dB/cm @ 1320 nm
• Switching voltage 40V (unstructured)

References

The work is carried out together with SIEMENS AG, BASF AG and FH Merseburg within the BMBF-initiative 03M4083

Publications/Patents

J. Nordmann, S. Beckmann, K.-H. Etzbach, R. Sens, M. Bauer, H. Krüger, J. Bauer, C. Günzelmann, H. Hartmann, A. Walter: Elektrooptische und photonische Bauelemente (1998)
DE 196 39 445 A1

J. Nordmann, S. Beckmann, K.-H. Etzbach, R. Sens, M. Bauer, H. Krüger, J. Bauer, C. Günzelmann, H. Hartmann, R. Flaig: Elektrooptische und photonische Bauelemente (1998)
DE 196 39 446 A1

J. Nordmann, S. Beckmann, K.-H. Etzbach, R. Sens, M. Bauer, H. Krüger, J. Bauer, C. Günzelmann:  Elektrooptische und photonische Bauelemente (1998)
DE 196 39 447 A1

J. Nordmann, S. Beckmann, K.-H. Etzbach, R. Sens, M. Bauer, H. Krüger: Elektrooptische und photonische Bauelemente (1998)
DE 196 39 381 A1

J. Nordmann, S. Beckmann, K.-H. Etzbach, R. Sens, M. Bauer, H. Krüger, J. Bauer, C. Günzelmann: Elektrooptische und photonische Bauelemente (1998)
DE 196 39 382 A1

Application

Mask coating: temporary protection of the resistance layer during different technological steps during processing of the component.

Passivation coating: hermetic protection of high performance resistors or other electronic components against environmental influence.

Scientific Achievement

Development of two coating systems on the basis of two different thermally curing reactive resin recipes for mask coatings: reactive resin recipes, which are suitable for the deposition of the outer contact by electroplating and of the inner contact via a sputter process.

Characteristics

• can be screen-printed
• low conductivity
• good adhesion
• 65-75% solids
• curing temperature < 180 °C
• can be pigmented (passivation coating)
• moisture resistant (passivation coating)
• can be lifted (mask coating)
• sputter resistant, electroplating stable (mask coating)

References

The work is carried out under the BMBF project „Neue Keramik- und Dünnschichtwerkstoffe für miniaturisierte Chipbauelemente“, Teilaufgabe: “ Weiterentwicklung von Passivierungs- und Maskierungslacken für hochwertige funktionelle Dünnschicht- und Keramikwerkstoffe“ (Förderkennzeichen: 03N1020C9)

Publications

H. Korth, H. Bilz, J. Dänhardt, K. Mathis, H. Krüger, W. Brüstel: Anwendungen neuer Werkstoffe in Verfahren zur Erzeugung hochwertiger Funktionselemente, Poster auf der Werkstoffwoche, München, 12.-15.10.1998