GB2398790A

GB2398790A - Polymer composition

Info

Publication number: GB2398790A
Application number: GB0329819A
Authority: GB
Inventors: Simmi Abrol
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-12-24
Filing date: 2003-12-23
Publication date: 2004-09-01
Anticipated expiration: 2023-12-23
Also published as: GB2398790B; GB0329819D0; DE10360895A1; AU2002953570A0

Abstract

A polymer composition suitable for encapsulation of electronic components comprises a polycyanurate matrix, a filler component and a toughening component. The polycyanurate matrix can comprise phenyl groups and more particularly can be a polymerisation product of one or more phenyl group and multiple cyanate ester comprising compounds.

Description

2398790 - 1

POLYMER COMPOSITIONS

Field of the Invention

The present invention relates generally to polymer compositions comprising a polycyanurate polymer matrix, a filler component and a toughening component, and in particular to polymer compositions wherein the polycyanurate matrix is a polymerization product of one of more phenyl group and multiple cyanate ester containing compounds.

The polymer compositions according to the invention, which exhibit improved crack resistant properties relative to known polyeyanurate materials, are particularly useful as encapsulants in electronic devices. The invention therefore also relates to electronic devices incorporating the polymer compos tions and to methods of production of the polymer compositions and the devices.

Background of the Invention

Small electronic components are commonly encased in filled polymer systems to ensure device operation. The encapsulant insulates the device from the surrounding environment both in manufacture (e.g. during press fitting operations) and in operation (e.g. protection from thermal, chemical and moisture attack). In protecting the devices the key role of the encapsulant is to prevent device failure via short circuit or reverse current.

Traditionally semiconductor encapsulation materials have consisted of twocomponent epoxy matrices filled with various conventional additives including fillers, antifoaming agents, colouring agents, coupling agents, plasticisers and the like. However, such epoxy materials have to date exhibited deficiencies that limit device properties.

These include the two component nature of epoxy materials, limited thermal stability (moderate glass transition temperature and onset of decomposition) and high iOTliC contamination (which reduces insulating properties), all of which result in limitations to product design, manufacture processes and maximal operation temperature and voltages.

There is an ever-present push to increase maximal operation temperattire of electrical devices such as power diodes, either through a need for increased operating power, or through increased operational environment temperatures (eg increased engme t temperatures). One potential material that may be used as an encapsulant m electronic devices may be based on the cyanate ester family of resin compounds. These cyanate esters may be derived from bisphenol compounds, by reaction of the alcohol group of the bisphenol with cyanogcn bromide / chloride. When heated, the cyanate ester monomers undergo exothermic cyclotrimerisation to form a cross- linked networked stntcturc, as shown in Fig. 1. The resultant materials have several characteristics that make them attractive altematives/replacements to two-component epoxies. Such characteristics include their single component nature, increased glass transition temperature, increased thermal stability, decreased moisture absorption, decreased dielectric constant and minimal ionic contaminant concentration, relative to the epoxy materials.

Research in relation to binary cyanate ester compositions is reported in Japanese Patent No. JP 19950214. This document discloses composite systems that contain the cyanate ester resin in combination with a silane coupling agent treated filler.

Unfortunately, however, the composites produced according to this approach provide only moderate cracking resistance, and have therefore been found unsuitable for use as encapsulant materials within electronic devices. The present inventors have now determined that by the inclusion of one of more toughener agents within a cyanate ester composition that includes the resin and a filecr material, it is possible to improve cracking or fracture resistance properties to enable such compositions to be utilised as encapsulate materials within electronic devices. Although toughening materials have been used in other polymer compositions, it was unclear prior to the present invention how their incorporation within cyanate ester compositions would affect the properties of these compositions.

Summary of the Invention

According to one embodiment of the present invention there Is provided a polymer composition compasmg a polycyanurate matrix, a filecr component, and a toughemng component. Preferably the polycyanurate matrix comprises phenyl Broths. The po,ycyaniirate matrix may be a polyrnerisatior. product of one or more pher.yl group and multiple cyanate ester comprising compounds.

Preferably the polycyanurate matrix is a polyrnerisation product of one or more of:

NCO OCN

NCO OCN Is

NCO OCN

NCO CH2 OCN

NCO OCN

NCO CH2 5/r MOCK NCO-C/9 = / - OCN NCO be/\ CH2 0CN NCO -' 'ó S OCN

NCO _ OCN

Cl\ ,CI NCO am NCO= OCN CF3 BAN OC,N CH2

OCN OCN OCN

CH2 CH The filler component may comprise one or more of alumina, silica coated aluminium Stride (SCAN), fused silica, crystalline silica, alumina silicate, alummium tahydrate, asbestos, barium sulphate, calcium carbonate, calcium sulphate, cellulosic, ceramic, ceramic spheres, charcoal, china clay, glass spheres, gypsum, kaolin, magnesium carbonate, manganese disulphde, marble powder, mica powder, nano filler (nano composite), perhte, starch, wollastomte, wood flour and zeohte.

Preferably the toughening component comprises agents selected from one or more of the categories of.

nhhery toughening agents; <A - s - hard particle toughening agents; hollow micro-sphere toughening agents; thermoplastic toughening agents; hybrid particle toughening agents; and/or layered particulate toughening agents.

In a particularly preferred embodiment the toughening component comprises one or more of albidur, polyacryonitrile, carboxy terminated butadiene, silicone treated fused silica, stearic acid treated calcium carbonate, methacrylate coated silica, biotite mica, Muscovite mica, carbon fibre and aramid pulp.

According to another embodiment of the invention there is provided a polymer composition generated from starting materials comprising: one or more phenyl group and multiple cyanate ester comprising compounds; a filler component; and a toughening component.

The starting materials may further comprise one or more of catalysts, coupling agents, plasticizers, colouring agents, anti-bacterial agents, emulsifiers, anti-foaming agents, anti-static agents and lubricants.

The phenyl group and multiple cyanate ester comprising compounds may be selected from one or more of:

NCO OCN

NCO 3 = OCN

NCO OCN

-

NCO -, 7- CH2 OCN

NCO OCN

NCO CH2 OCN SCOW= - OCN NCO/\CH20CN NCO S an/ \-OCN

NCO OCN

Cl\,Cl

NCO C OCN CF3

NCO OCN CF3

rail ( )C N CH2

OCN OCN OCN

] CH2] CH2 W] In another preferred aspect of the invention the starting materials comprise: (A) one or more phenyl group and multiple cyanate ester comprising compounds; (B) an alkyl phenol cocatalyst component; (C) a metal catalyst component; (D) a filler component; (E) a coupling component; (F) a toughening component.

Preferably (A) to (F) are present within about the following relative weight fractions: (A) / [(A) t(B)+(C)+(D)+(E) (F)] = 0 2 0 95 (B) / (A) = 0.01-0.1 (C) / (A) = 0.001-0.1 (D) / [(A)+(B)+(C)+(D)+(E)+(F)] = 0.01 0.75 (E) / [()-(B)+(C)+(D)+(E)+(F)] -- 0.01 - 0 06 (F) / [(A)+(B)+(C)J = 0.01 - 0.3 More preferably (A) to (F) are present within about the following relative weight fractions: (A) / [(A)(B)--(C)-(D)-(E)+(F)] = 0 3 0 45 - 8 (B) / (A) = 0.01 - 0.1 (C) / (A) = 0.001 - 0.1 (D) / [(A)+(B)+(C)+(D)+(E)+(F)] -. 0 50 - 0.7 (E) / [(A)-t(B)+(C)+(D)+(E)+(F)] 0.01 - 0.06 (F) / [(A)+(B)+(C)] = 0.025 - 0.125 According to another embodiment of the present invention there is provided an electronic device having electrical components at least partially encapsulated within a polymer composition as outlined above. The electronic device may be a power diode, a semiconductor, a silicon chip, a flip chip underlay, an hermetic package, a generator or an ignition coil.

According to another embodiment of the invention there is provided a power diode comprising a pin and a base, between which is sandwiched a P/N semiconductor chip, wherein the pin, base and chip are at least partially encapsulated within a polymer composition as outlined above. In a preferred embodiment there Is no lacquer coating on the P/N semiconductor chip.

According to a still further embodiment of the invention there Is provided a method of producing a polymer composition comprising mixing one or more phenyl group compnsmg multiple cyanate ester compounds, a filler component, a toughening component and optional further components, forming the mixture into a suitable conformation and heating to a suitable temperature and for a suitable period for polyrnerisation to take place.

Brief description of the Figures

The present invention will be f;trther described by way of example only with reference to the Figures, wherein.

F'g l shows a reaction scheme of the thermally imitated cyclotrimensation of cyanate ester monomers to forth a polycyanurate.

fig. shows dagrarnmatc representations of a prior art (is) power diode and a power diode according to the invention (B).

Fig. 3 shows the effect of contcat (wt% of matnx) of different thermoplastic tougheners (triangle - polyctherimicle (PEI) Ultem 1000, circle - polyethersulphone (PES)) on the fracture toughness Kc (MNrn32) of filled cyanate ester composites prepared according to examples 9 and 10, respectively.

Fig. 4 shows the effect of content (wt% of matrix) of different thermoplastic tougheners (triangle - polyetherimide (PEI) Ultem 1000, circle - polyethersulphone (PES)) on the fracture energy Go (Jm2) of filled cyanate ester composites prepared according to examples 9 and 10, respectively.

Detailed description of the Invention

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "compose", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art In this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common genera] knowledge in Austraha.

The polycyanurates are particularly suited as encapsulating agents for electronic devices in view of their thermal stability and high glass transition temperatures, which approach their thermal decomposition temperatures. As the cyanate esters polymerise by an addition reaction, no volatile materials or byproducts are produced during polymerization that may form voids or subsequent loss of strength in the polymer product.

The polycyanurate matrix utrlrsed vithm the compositions of the invention may take a variety of different forms, although it is preferred that the polycyanuratcs will be 3() generated from monomers that include two or more cyanate ester groups and include at least one phenyl group. The presence of two or more cyanate ester groups within the monomer units will allow the generation of a cross-linked polymer matrix. While it will usually be the case that the cyanate ester monomers adopted within the polycyanurate matrix will be the same, it is possible for the polycyanurate matrix to be generated from two or more different multiple cyanate ester comprising monomer compounds. Suitable phenyl group and multiple cyanate ester composing compounds that may be utilised to generate the polycyanurate matrix incorporated within compositions of the invention, include the following:

NCO OCN

NCO 3 OCN

NCO OCN

NCO CH20CN NCO:3OCN NCO= CH2 OCN NCO\' "ON - 11 NCO mu\ CH2 OCN

NCO S OCN

NCO OCN Cl\,

NCO \ ,

NCO OCN CF3

OCN OCN CH2

OCN OCN OCN

CH2 CH2 The examples of cyanatc ester monomer compounds presented above are not intended] to be limiting upon the scope of the invention, and is to be understood that other cyanate ester monomers which include two or more cyanate ester groups and preferably - 12 also include at least one phcnyl grotto, may be utilised in generation of the polycyanurate matnx. As would be readily understood by persons skilled in the art the nature and proportions of cyanate ester monomers will be selected depending upon the specifically desired characteristics of the composition intended to be produced. Cyanate ester monomers such as those identified above are readily commercially available. The cyanate ester monomers employed m this invention are preferably hquid at ambient temperatures.

This imparts several benefits to device preparation including a reduced propensity to entrain gas bubbles, reduced propensity for inadequate device coating, and avoidance of polymer compromise due to monomer crystallization during potting. The present invention does not preclude the use of cyanate ester monomers with melting points higher than 25"C due to the fact that such monomers may be blended with sub ambient melting (or super cooled) monomers to achieve eutectic melting point depression, and hence produce an ambient temperature liquid monomer. The overall potting process may also be conducted with heating so that the resin is melted.

The compositions according to the invention will also include a filler component.

A wide variety of filler materials may be incorporated within the compositions of the invention, as will be well understood in the art. Generally, however, the filler component will constitute inorganic materials which are generally unreactive and which are incorporated within the polymer matrix, but which can be selected on the basis of the physical properties they will impart upon the polymer compositions. Examples of materials that may be incorporated within the filler component, either solely or in combination, are one or more of alumina, silica coated aluminium nitride (SCAN), fused silica, crystalline sihca, alumina silicate, aluminium tnhydrate, asbestos, barium sulphate, calcium carbonate, calcium sulphate, cellulosic, ceramic, ceramic spheres, charcoal, china clay, glass spheres, gypsum, kaolin, magnesium carbonate, manganese disulphide, marble powder, mica powder, nano filler (nano composite), perlite, starch, wollastonte, wood flour and zeolite. Although these materials may be in spherical form, ruptured form, or other physical forms it is most preferred that a spherical forth is adopted as this enables high fi Her loadings.

For example, filler may be present withy the composition in a wegllt fraction of - 13 between about 0.01 to about 0.85, preferably between about 0.01 to 0.75 and most preferably between abort 0.5 to 0.7 of the total weight of the composition. Filler content below about 0.45 of the total weight of the composition is undesirable because as a result the encapsulant is likely to have too high a coefficient of thermal expansion and too low a dimensional stability. In contrast, filler content above about 0.7 of the total weight of the composition is also undesirable as this is likely to give rise to unsuitably high pre-cure viscosity which is likely to lead to extraneous gas entrapment and a brittle final material.

Preferably the filler component will include filler materials of varying sizes, each of which will impart different characteristics upon the end product. Large individual filler particles will permit the presence of high filler content due to the aspect ratio, although particles of this size type have a tendency to settle and create non-uniform filler distribution. Small filler particles have a dramatically reduced tendency to settle, and in fact at high loading may tend to float or percolate to the top of the mixture. The presence of excessive amounts of small filler particles may also increase the viscosity of the formulation and thereby increase gas entrainment. Balance of large and small particle sizes within the filler component will allow for optimal anti-settling properties along with optimal viscosity, to allow pouring of the material during potting for generating the appropriate conformation to be utilised in the end product, at the same time as allowing this process to be conducted at suitable temperatures while gas entrainment is minimised.

In one preferred embodiment of the invention the filler component includes various size particles of spherical silica. In another preferred embodiment the filler component comprises various sizes of spherical silica coated aluminium nitrite (SCAN). The use of various sized particles of spherical scan is particularly suitable for high power and tempt rature applications where the encapsulant is required to also act as a heat sink. The SCAN filler is preferred over other filler materials due to its high thermal conductivity, which is some 10 times that of conventional silica fillers. When the polymer formulation includes a weight fraction of 0 6 to 0.65 of high thermal conductive filler, the composition will act as an effective thermal concltctor that dsperscs heat generated by the electronic device away from the dcviee/encapsulant interface.

In another embodiment of the invention the filler may comprise a mixture of two or - 14 more preferred types of filler matenal. In this way it is possible to optimism characteristics such as thermal conductivity, without incurring a significant cost penalty.

The compositions according to the present invention include a toughener component, which the present inventors have demonstrated to reduce the propensity for failure or cracking under mechanical stress of the polycyanurate compositions. There are a variety of classes of toughener agents which are well recognised within the art and which may usefully be incorporated within the present compositions. For example, the toughening component may be selected from one or more of the categories of rubbery toughening agents, hard particle toughening agents, hollow micro-sphere toughening agents, thermoplastic toughening agents, hybrid particle toughening agents and layered particulate toughening agents. Examples of rubbery phase toughening agents include alibidur, polyacrylonitrile, and carboxy terminated butadiene. Examples of hard particle toughening agents include silicon treated fused silica or steric acid calcium carbonate, such as for example silicon treated I lam fused silica and steric acid treated 0.7 1lm calcium carbonate. Examples of hybrid particle toughening agents (also referred to "core shell" particles) include methacrylate coated silica and examples of layered particulate toughening agents include biotite mica, Muscovite mica or others of the mica group of minerals as well as fibres such as carbon fibre or aramid pulp. Examples of themnoplastc toughening agents include polyetherimide (PEI), polyethersulphone (PES), aromatic polyesters, aromatic polysulphones and polyimides. Preferred thermoplastic toughening agents are PEI and aromatic polyesters. Preferably the toughening component is present in a weight fraction of between about 0.01 to 0.3, more preferably between about 0.025 and 0.125 of the total weight of the matrix (that is, the weight of the composition excluding weight of the filler, coupling and toughening components).

Generally the toughening component will have the effect of altering properties of the composition such as dimensional stability, or more particularly modulus and strength.

T he actual toughening component selected will depend upon the nature of the polycyanurate material, the properties of the filler component and desired properties of the end product, m particular dmcnsonal stability, toughening micro-mechanism and thermal - 15 expansion.

It may be appropriate to incorporate within the starting materials utilised to prepare the composition one or more further components such as catalysts, coupling agents, plasticizers, colouring agents, anh-bactenal agents, emulsifiers, anti- foamng agents, anti- static agents, lubricants and other components routinely used in the polymer chemistry field, particularly in the preparation of encapsulant materials for electronic devices. It may be particularly suitable for an alkyl phenyl co-catalyst component and/or a metal catalyst component to be incorporated into the starting materials. Examples of suitable alkyl phenyl co-catalysts include, but are not restricted to, nonylphenol and dinonylphenol. As indicated above, the preferred catalyst component that may be utilised is a metal catalyst component which may for example consist of a soluble coordination metal carboxylate (naphthenate or octoate) or chelate (acetylactetonate) with the metal centre consisting of Cu2i, Co2+ 3+, Zn2+, or Mn2+. Examples of such catalysts include, but are not restricted to; Zinc (11) chloride, Chromium (III) acetylacetonate, Cobalt (II) acetylacetonate, Cobalt (III) acetylacetonate, Copper (II) acetylacetonate, Zinc (II) acetylacetonate, Manganese (II) acetylacetonate, Cobalt (III) naphthenate, Copper (II) napthenate, Zinc (11) napthenate, Cobalt (11) octoate, Manganese (II) octoate, Zinc (II) octoate, or encapsulated catalysts and the like.

The preferred weight fraction of alkly phenyl co-catalyst to cyanate ester monomer is 0.01 to 0.1 and the preferred weight fraction of metal catalyst to cyanate ester monomer is 0.001 to 0.1. High levels of the alkyl phenyl co-catalyst, such as for example in weight fractions compared to the cyanate ester monomer in excess of 0.06, may give rise to a plasterismg effect that may result in a decrease in glass transition temperature arid elastic modulus of the resultant composite. Similarly high levels of metal catalyst, such as for example in excess of weight ratios against the cyanate ester monomer of 0.1 could result m premature curing of the compositions of the invention.

Another preferred cornponcnt that may be incorporated within the compositions of the invention is a coupling agent, which may be used to treat the filler component surface such that adhesion interactions between the filler and the polymer matrix are optimised. on - 16

The coupling agent component may for example consist of silane coupling agents (for example silane esters such as Silquest A-137, A-162, A-1230, A-1630, and Y-11597), vinyl slanes (such as Silquest RC-1, A-151, A-171, A-172 and A-2171), methacryloxy l silanes (such as Silquest A-174), epoxy silane (such as Silquest A-186 and A-187), sulphur silane (such as Silquest A-189, RC-2, A-1289 and A-1589), amino silane (such as Silquest A-1100, A-1101, A-1102, A-1106, A-1108, A-1110, A-1120, A-1126, A-1128, A1130, A-1170, Y-9669, Y-11343, A-1387 and A-2120), ureido silane, isocyanato silane, alkoxysilane or titanate coupling agents such as for example monalkoxy ttanates, chelate titanates, quat ttanates, coordinate titanates or neoalkoxy ttantes. Coupling agents may be present in a weight fraction of 0.01 to 0.06 of the total weight of the composition. In one preferred embodiment the coupling agent is present in a weight fraction of 0.2 based on the weight of the filler compound.

A most preferred coupling component is an organo-titanate coupling agent, and particularly an aromatic titanate coupling agent, such as KR 134S manufactured by KenRich. As indicated above, the coupling component provides intermediate adhesion between filler and matrix. Use of a treatment, such as epoxy silane treatment which will promote near perfect adhesion, may in some contexts be problematic in that the resultant polymer composition may have excessive strength that is therefore brittle and subject to fracture. Use of a treatment such as silicone mold release agent, which will tend to limit adhesion may also be problematic in that the resultant polymer material may have high fracture toughness but inadequate strength.

The polymer compositions according to the present invention may be incorporated withm electronic crevices such as power diodes, semi conductors, silicon chips, flip chip underlays, hermatc packages, generators, ignition coils and the like. The compositions of the Invention are well suited to use in devices designed to operate at temperatures exceeding 150 C and to thereby provide the physical protection as well as electrical and heat insulation for electrical components of the electronic devices. This will be achieved by encapsulating the electrical components at least partially within the polymer composition by virtue of potting or pouring the liquid polymer composition starting Lo - 17 material into the appropriate conformation (for example within an appropriate mold) and in association with the other components of the electronic device, and then allowing the material to cadre by exposure to heating to a suitable temperature for a suitable period for polymensation of the composition to take place. For example, depending upon the exact nature of the starting materials adopted, the potted materials may be heated to between about 140 C to about 350 C for between about 20 minutes and about 12 hours, more preferably between about 1 60 C to about 260 C for between about I hour to about 8 hours, and particularly preferably between about 160 C and about 260 C for between about 2 hours and about 6 hours. In another embodiment of the invention the heating may involve a schedule of heating for defined periods of time at distinct temperatures, such as for example for a period of half an hour or one hour, two hours, three hours or four hours at temperatures of for example 140 C, 160 C, I 80 C, 200 C, 220 C, 240 C or 260 C. In a particularly preferred embodiment of the invention heating of the potted materials is for approximately one hour at 160 C, followed by a further one hour at 220 C and a further two hours at 260 C.

In a preferred embodiment of the invention the electronic device into which the polymer compositions of the present invention are formed is a power diode, as for example shown in Fig. 2B, which relative to the standard power diode design shown in Fig. 2A does not require the presence of a lacquer coating 5 on the P/N chip. As shown in Fig. 2B the power diode consists of a pin I and a base 2 between which is sandwiched a P/N semiconductor chip 3, wherein the pin, base and chip are at least partially encapsulated by the polymer composition 4 according to the invention. Preferably, when the polymer composition of the invention is intended to be utiliscd in manufacture of power diodes the composition will meet the application requirements outlined in Table 1.

The present invention will now be described with reference to the following non-

limting examples. To - 18

F,xample 1: Formulations Ingredients according to table I were dispersed into the liquid polycyanate ester monomer vehicle using an overhead Warring type mixer. The resultant polycyanate ester potting composition was molded both into test samples and onto alternator power diodes.

Test pieces were evaluated for mechanical, therrna], and electrical properties according to the following methods.

À Glass transition: Modulated Differential Scanning Calorimetry, MDSC.

À Thermal Stability. Therrnogravimetric Analysis, TGA.

À Thermal E.rparsion: TherrnoMechanical Analysis, TMA.

À Fle.Zral norllrs and strength: 3 point bend mechanical testing according to ASTM D700.

À Compressive mottles and strength: parallel platen compressive testing according to ASTM D 695.

À Fracture toughness and energy: Double torsion fracture toughness testing.

À Electrical conductivity: Electrochemical Impedance Spectroscopy, EIS.

Examples 2 - 8: Formulations Liquid polycyanate ester encapsulant materials were obtained in a similar manner to example 1, except that the formulations described in table 2 were adopted. Test pieces were prepared and their properties were characterized.

The following ingredients were used in all examples: 2,2-Bis(4-cyanatophenyl)propane, AroCy B cyanate ester resin Nonylphenol, alkylphenol cocatalyst Copper Acetylacetonate (CuAcAc), coordinate transition metal catalyst Spherical fused silica (SE 5) (Manufactured by Tokoyuna) The following ingredients were used in the proportions shown Intable 2 Ttanate coupling agent KR I 34s (manufactured by Ken-React) Epoxy Silane coupling agent (ash) (manufactured by Osi Specialty Chemicals) Muscovite Mica (Mica) - 19 Alibdur (Manufactured by Hansa Chemie) (PAN) Polyacrylonitrile Aramid (Manufactured by Du Pont) Examples 9 & 10: Formulations Liquid polycyanate ester encapsulant materials were obtained in a similar manner to example 1, except that the following formulations were adopted. Test pieces were prepared and their fracture toughness (Fig. 3) and fracture energy (Fig. 4) were determined.

The formulations consisted of:

_

Matrix (primaset lecy) 40% by weight of formulation l Filler (fused silica) 60% by weight of formulation Coupling agent (titanate) 2% by weight of the filler component Toughening agent - PEI (example 9) 0, 5, 10 or 15% by weight of matrix component - PES (example 10) 0.5 or 10% by weight of matrix component Example 11: Power Diodes A liquid polycyanate ester composition formulated according to any of examples I are potted, using a six-nozzle dispenser, onto BOSCH ZR power diodes. The potted diodes are then placed in an oven and cured Ltsing the following schedule, I hour at 160 C, I hour at 220 C and 2 hours at 260 C. The resultant diodes are tested for application compliance according to the test schedule in table 3. To - 20

Property Application requirement Glass Transition, Tg > 250"C Decomposition temperature, TO > 300 C Coefficient of thermal expansion, CTE 30-35 rim m, K- AC conductivity, is < 1 x 10- S cmi Flexural modulus (3pt bend) 9000 (+ 1000) MPa Compressive Modulus 10,000 (+ 1000) MPa Flexural Strength > 100 MPa Compressive Strength > 60 MPa Fracture toughness, K'c (4pt dual 1.5 - 1.7 MPa cantilever) Fracture energy, G'c (4pt dual cantilever) 250 - 300 J m2 Viscosity at potting temperature 30 50 Pas Table 1: Performance requirements for power diode application O 1= IVJ U) C, UJ V] I 0 Go O 0 0 ] vet i 0 co E A. en, v, To OoO o A

E C

Xo Cat o o o o o E, I I oo 0, Q Cat E o o o

C

_. =0 o 0 vet CL X 1 c-' == c: Cat V] o o o c V o O CL a O 0 00 O. v' O c: C) -1 O O 0 _

O CCL -

U _ =0 0 0 v' O O E - d,, ,, ,,, c: Àe c - . - c p d d _ - 22 Failure Test Test criterion Temperature cycling test (Active) 3000 cycles Temperature shock test (passive) -40 to 250 C, 100 cycles Hot storage test 250 C, 1000 hours Cold storage test -40 C, 250 hours End of life (EOL) test 41000 cycles High temperature reverse bias test 250 C, 1000 hours Moisture absorption < 1% at 85 C 85 relative humidity 500 hours Salt Spray test 35 C, 5%NaCI, 200 hours, without rinsing Sealing test I M Sodium acetate, 25 C,SO N/cm2, 4 hours Pull test (upper wire) >70 N at 250 C Bending test (upper wire) >20 N at 250 C Vibration test Real vibration in generator Load dump test 1500 W. 0.6ms, 1000 pulses Mechanical shock test metal block dropped from Im height, 10 repetitions Continuous wet hot test 85 C, 85% relative humidity, 500 hours Table 3: Test cutenon for power diode application testing - 23

Claims

T77E CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: I. A polymer

composition comprising: a polycyanurate matrix; a filler component; and a toughening component.
2. The polymer composition according to claim l wherein the polycyanurate matrix comprises phenyl groups.
3. The polymer composition according to claim I wherein the polycyanurate matrix is a polymerization product of one or more phenyl group and multiple cyanate ester composing compounds.

I 5
4. The polymer composition according to claim I wherein the polycyanurate matrix is a polymerization product of one or more of: NCO gOCN i 1 NCo33 OCN NCO 3 OCN NCOCH20CN o - 24

NCO OCN

NCO a,'\ \ CH2 4 0CN NCO/=OCN NCO/\CH2 g:OCN NCOgS 43 OCN NCO { j ON Cl\ , CI NCOCI /: <\ OCN NCO = OCN CF3 -

OCN OCN CH2

OCN OCN OCN

CH2 CH2
5. The polymer composition according to claim I wherein the filler component comprises one or more of alumina, silica coated aluminium nitride (SCAN), fused silica, crystalline silica, alumina silicate, alumintum trihydrate, asbestos, barium sulphate, calcium carbonate, calcium sulphate, cellulosic, ceramic, ceramic spheres, charcoal, china clay, glass spheres, gypsum, kaolin, magnesium carbonate, manganese disulphide, marble powder, mica powder, nano filler (nano composite), perlite, starch, wollastonite, wood flour and zeolite.
6. The polymer composition according to claim I wherein the toughening component comprises agents selected from one or more of the categories of: rubbery toughening agents; hard particle toughening agents; hollow micro-sphere toughening agents; thermoplastic toughening agents; hybrid particle toughening agents; and/or layered particulate toughening, agents.
7. The polymer composition according to claim I wherem the toughening component comprises one or more of albdur, polyacryonitrile, carboxy terminated butadene, silicone treated fused silica, stearic acid treated calcium carbonate, methacrylate coated silica, biotite mica, Muscovite mica, carbon fibre, aramid pulp, polyethenmmtle, polyethersulphone, aromatic polyester, aromatic polysulphone and polyamide. - 26
S. A polymer composition generated from starting materials composing: one or more phenyl group and multiple cyanate ester cornpnsmg compounds; a filler component; and a toughening component. :
9. The polymer composition according to claim 8 wherein the starting materials further comprise one or more of catalysts, coupling agents, plasticizers, colouring agents, anti-bacterial agents, emulsifiers, anti- foaming agents, anti-static agents and lubricants.
10. The polymer composition according to claim 8 wherein the phenyl group and multiple cyanate ester comprising compounds are selected from one or more of:

NCOOCN

NCO= OCN

NCO OCN

NCO of/ CH2 3 OCN NCO= ' OCN NCO CH240CN! - 27 /=,OCN NCO/\CH2 ON NCO= SOCN NCO; OCN Cl\ ,CI NCO=C OCN i NCO OCN CF3

OCN OCN CH2

OCN OCN OCN

CH2 j: > CH2

- - 28
11. The polymer composition according to claim 8 wherein the filecr component comprises one or more of alumina, silica coated altmimtm nitride (SCAN), fused silica' crystalhne silica, alumina silicate, alurninium tritydrate, asbestos, barium sulphate, calcium carbonate, calcium sulphate, cellulosic, ceramic, ceramic spheres, charcoal, china clay, glass spheres, gypsum, kaolin, magnesium carbonate, manganese disulphide, marble powder, mica powder, nano filler (nano composite), perlite, starch, wollastonite, wood flour and zeolite.
12. The polymer composition according to claim 8 wherein the toughening component comprises agents selected from one or more of the categories of.

rubbery toughening agents; hard particle toughening agents; hollow microsphere toughening agents; thermoplastic toughening agents; hybrid particle toughening agents; and/or layered particulate toughening agents.
13. The polymer composition according to claim 8 wherem the toughening component comprises one or more of albidur, polyacryonitrile, carboxy terminated butadiene, silicone treated fessed silica, stearic acid treated calcium carbonate, methacrylate coated silica, biotite mica, muscovite mica, carbon fibre, arched pulp, polyetheriminide, polyethersulphone, aromatic polyester, aromatic polysulphone and polyimide.
14. The polymer composition according to claim 8 \vheren the starting materials comprise (A) one or more phenyl group and multiple cyanate ester comprising compounds; (B) an alkyl phenol cocatalyst component; (C) a metal catalyst component; ( L)) a fi 11 er component; - 29 (E) a coupling component; (F) a tottghemng component.
15. The polymer composition according to claim 14 wherein (A) to (F) are present within about the following relative weight fractions: (A) / [(A)+(B)+(C)+(D)(E)+(F)] = 0.2 - 0.95 (B) / (A) = 0.01-0.1 (C) / (A) = 0.001-0.1 I (D) / [(A)-r(B)+(C)+(D) (E)+(F)] = 0.01 - 0.75 (E) / [(A)+(B)+(C)-(D)+(E)+(F)] = 0.01 - 0.06 (F) / [(A)+(B)+(C)] = 0.01 - 0.3
16. The polymer composition according to claim 14 wherein (A) to (F) are present within about the following relative weight fractions: (A) / [(A)+(B)+(C)+(D)+(E)+(F)] = 0.3 0.45 (B) / (A) = 0.01 - 0.1 (C) / (A) = 0.001 - 0.1 (D) / [(A)+(B)-(C)+(D)+(E)+(F)] = 0.50 0 7 (E) / [(A)+(B)+(C)+(D)+(E)+(F)] 0.01 - 0.06 (F) / [(A)+(B)+(C) = 0.025 - 0. 125
17. An electronic device having electrical components at least partially encapsulated within a polymer composition according to any one of claims I to 16.
18. The electronic device according to claim 17 which is a power diode, a semiconductor, a silicon chip, a flip chip underlay, an thematic package, a generator or an Ton coil.
19. A power diode comprising a pm and a base, between which is sandwiched a PIN semiconductor chip, wherem the pin, base and chip are at least partially encapsulated withy a polymer composition according to any one of claims I to 16.
-A - 30

The power diode according to claim 19 wherein there is no lacquer coating on the P/N semiconductor chip.
21. A method of producing a polymer composition comprising mixing one or more phenyl group and multiple cyanate ester comprising compounds, a filler component, a toughening component and optional farther components, forming the mixture into a suitable conformation and heating to a suitable temperature and for a suitable period for polymerization to take place.
22. A polymer composition according to either claim I or claim 8, substantially as hereinbefore described with reference to the examples and/or figures.
23. A power diode according to claim 19, substantially as hereinbefore described with reference to the examples and/or figures.
24. A method of producing a polymer composition according to claim 21, substantially as hereinbefore described with reference to the examples and/or figures.