WO2014027955A1

WO2014027955A1 - A novel method of making a novel lcp nanocomposite

Info

Publication number: WO2014027955A1
Application number: PCT/SG2012/000291
Authority: WO
Inventors: Shuang Wu Huang; Tah-Fah CHU; Chin Kwee LIM
Original assignee: Unisteel Technology International Limited
Priority date: 2012-08-16
Filing date: 2012-08-16
Publication date: 2014-02-20

Abstract

A novel method for preparing a novel nanocomposite is described. The method comprises the step of mixing nano-fillers with a Liquid Crystalline Polymers (LCP) matrix to form the nanocomposite. The LCP matrix has segments and intermolecular spaces between the segments. The nano-fillers are hermetic and nano-sized, and are molecularly arranged in the intermolecular spaces such that the nanocomposite is hermetic.

Description

A NOVEL METHOD OF MAKING A NOVEL LCP NANOCOMPOSITE

FIELD OF THE INVENTION

[0001] The present invention relates to a new method of making a new Liquid

Crystalline Polymers (LCP) nanocomposite and the use of this LCP nanocomposite to package electronic devices.

BACKGROUND

[0002] Electronic devices are prone to dust, dirt, moisture and other contaminants, which through exposure will affect the operating reliability of the devices. Hermetic packaging can be used to shield the devices from these contaminants. Examples of hermetic packaging materials are metal, silicon, ceramic and eutectic seals. However, hermetic packages are expensive. Moreover, the technical and manufacturing resources for producing hermetic packages are diminishing.

[0003] There is therefore a need to look for an alternative cheaper method to package electronic devices. Ideally, this new method should also be lighter and produce superior hermetic qualities when compared to hermetic packaging.

[0004] The use of Liquid Crystal Polymers (LCP) substrates is a likely candidate to substitute hermetic packaging. This is because LCP have an oriented crystalline structure and therefore layers of LCP can be packed closely which therefore improves the barrier proprieties of the packaging. Moreover, LCP have excellent electrical properties and a low co-efficient of thermal expansion. However, the drawback of LCP is that it is not fully hermetic (and only near-hermetic) as molecules are still able to diffuse through it. Figure 1 shows the internal structure of near- hermetic LCP 101. Near-hermetic LCP 101 contains amorphous segments 102 and crystalline segments 103. Moisture and small molecules can permeate or diffuse through the intermolecular spaces between the amorphous segments 102 and the crystalline segments 103 of the near-hermetic LCP 101 . The path of the moisture and small molecules through the near-hermetic LCP 101 is depicted in Figure 2 as path 104. [0005] The object of the invention is thus to provide a solution that overcomes the above disadvantages or at least provide a novel method of making a novel LCP nanocomposite suitable for packaging electronic devices.

SUMMARY OF INVENTION

[0006] According to a first aspect of the invention, a method for preparing a nanocomposite is described, the method comprising the step of mixing nano-fillers with a Liquid Crystalline Polymers (LCP) matrix to form the nanocomposite. The LCP matrix has segments and intermolecular spaces between the segments. The nano-fillers are hermetic and nano-sized, and are molecularly arranged in the intermolecular spaces such that the nanocomposite is hermetic.

[0007] In another embodiment, prior to the step of mixing nano-fillers with a Liquid

Crystalline Polymers (LCP) matrix to form the nanocomposite, compatibilizers are mixed with the nano-fillers. Compatibilizers are organic materials that chemically bond the nano- fillers to the segments.

[0008] In another embodiment, the method further comprises the step of mixing adhesion promoters with the nanocomposite. Adhesion promoters are solid epoxy resins that improve the metallic bonding strength of the nanocomposite.

[0009] In another embodiment, the method further comprises the step of mixing inorganic particles with the nanocomposite. Inorganic particles are rigid and micro-sized particles that increases the rigidity of the nanocomposite.

[0010] In another embodiment, the method further comprises the step of mixing antioxidants with the nanocomposite.

[001 1] In another embodiment, the method further comprises the step of mixing glass fibers with the nanocomposite.

[0012] In another embodiment, the nano-fillers are wollastonite minerals, kaolin minerals, talcum powder minerals or mica minerals. [0013] In another embodiment, the nano-fillers have an aspect ratio of higher than 10.

[0014] In another embodiment, the inorganic particles are C_aC0₃, B_aC0₃, B_aS0₄ or

M_gC0₃ micro particles.

[0015] In another embodiment, the anti-oxidants are anti-oxidant 1010 molecules or anti-oxidant 168 molecules.

[0016] According to a second aspect of the invention, a nanocomposite is described comprising a Liquid Crystalline Polymers (LCP) matrix, the LCP matrix having segments and intermolecular spaces between the segments. The nanocomposite further comprises nano- fillers, wherein the nano-fillers are hermetic and nano-sized, and are molecularly arranged in the intermolecular spaces such that the nanocomposite is hermetic.

[0017] In another embodiment, the nanocomposite further comprises compatibilizers.

Compatibilizers are organic materials that chemically bond the nano-fillers to the segments.

[0018] In another embodiment, the nanocomposite further comprises adhesion promoters. Adhesion promoters are solid epoxy resins that improve the metallic bonding strength of the nanocomposite.

[0019] In another embodiment, the nanocomposite further comprises inorganic particles. Inorganic particles are rigid and micro-sized particles that increases the rigidity of the nanocomposite.

[0020] In another embodiment, the nanocomposite further comprises anti-oxidants.

[0021 ] In another embodiment, the nanocomposite further comprises glass fibers.

[0022] In another embodiment, the nano-fillers are wollastonite minerals, kaolin minerals, talcum powder minerals or mica minerals.

[0023] In another embodiment, the nano-fillers have an aspect ratio of higher than 10. [0024] In another embodiment, the proportion of nano-fillers is 10 to 30 parts by weight.

[0025] In another embodiment, the proportion of compatibilizers is 1 to 10 parts by weight.

[0026] In another embodiment, the proportion of glass fibers is 10 to 50 parts by weight.

[0027] In another embodiment, the proportion of adhesion promoters is 1 to 10 parts by weight.

[0028] In another embodiment, the proportion of anti-oxidants is 0.1 to 1 parts by weight.

[0029] In another embodiment, the inorganic particles are C_aC0₃, B_aC0₃, B_aS0₄ or

M_gC0₃ micro particles.

[0030] In another embodiment, the anti-oxidants are anti-oxidant 1010 molecules or anti-oxidant 168 molecules.

[0031] According to a third aspect of the invention, a Quad Flat No-lead (QFN) package for Microelectromechanical systems (MEMS) devices comprising a substrate made up of comprising the nanocomposite as described.

[0032] The invention will now be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying figures illustrate disclosed embodiment(s) and serve to explain principles of the disclosed embodiment(s). It is to be understood, however, that these drawings are presented for purposes of illustration only, and not for defining limits of the application.

[0034] Figure 1 shows the internal structure of a near-hermetic LCP.

[0035] Figure 2 shows the path of moisture and small molecules through a near- hermetic LCP.

[0036] Figure 3 shows the internal structure of a hermetic LCP nanocomposite in accordance with the invention.

[0037] Figure 4 shows the path of moisture and small molecules through a hermetic

LCP nanocomposite.

[0038] Figures 5 (a), (b), (c) and (d) shows exemplary shapes of nano-fillers.

[0039] Figure 6 shows the internal structure of a hermetic LCP nanocomposite with nano-fillers being joined to an amorphous segment or a crystalline segment via compatibilizers.

[0040] Figure 7 shows a flow chart illustrating a method of preparing a hermetic LCP nanocomposite in accordance with the invention.

[0041] Figure 8 shows a flow chart illustrating a method for fabricating a Quad Flat

No-lead (QFN) package using the hermetic LCP nanocomposite.

[0042] Figure 9 shows a perspective view of the pre-molded QFN open cavity substrate.

[0043] Figure 10 shows a top view of the pre-molded QFN open cavity substrate.

[0044] Figure 1 1 shows a cross-sectional side view of the QFN package. [0045] Exemplary, non-limiting embodiments of the present application will now be described with references to the above-mentioned figures.

DETAILED DESCRIPTION

[0046] Figure 3 shows the internal structure of a LCP nanocomposite 301 in accordance with the invention. LCP nanocomposite 301 contains in addition to amorphous segments 302 and crystalline segments 303, nano-fillers 304, compatibilizers 305, adhesion promoters 306, inorganic particles 307 and anti-oxidants 308.

[0047] Nano-fillers 304 are nano-sized mineral fillers. Examples of nano-fillers 304 are wollastonite minerals, kaolin minerals, talcum powder minerals, mica minerals. These are exemplary examples only. One skilled in the art can appreciate that any nano-sized hermetic particle can be used as a nano-filler. Nano-fillers 304 are added to the LCP, and the nano- fillers 304 are molecularly arranged in the intermolecular spaces between the amorphous segments 302 and the crystalline segments 303 of the LCP to increase its hermetic properties.

[0048] This is illustrated in figure 4 where nano-fillers 304 hinder the permeation of moisture and small molecules across the LCP nanocomposite 301. Nano-fillers 304 themselves are hermetic, and therefore hinders the moisture and small molecules from permeating across the LCP nanocomposite 301 by diverting the moisture and small molecules. The nano-fillers 304 are dispersed at the nano level in the intermolecular spaces among the amorphous segments 302 and the crystalline segments 303. The moisture and small molecules collide with the nano-fillers 304 and are diverted.

[0049] This intermolecular collision with the nano-fillers 304 causes the moisture and small molecules to lose kinetic energy and momentum. The diverted path of the moisture and small molecules through the LCP nanocomposite 301 is depicted in Figure 4 as diverted path 309. Repeated diversions by the nano-fillers 304 will cause the moisture and small molecules to eventually lose all kinetic energy and stop within the LCP nanocomposite 301. As a result, the LCP nanocomposite 301 is able to achieve good hermetic performance.

[0050] The nano-fillers 304 as its name suggests, are nano-sized. This is because larger sized fillers (for example micro-sized) do not function as well as they are more susceptible to aggregation i.e. the fillers clumping or grouping together, causing phase separation and forming a larger and irregular mass. This is undesirable as aggregation will affect the distribution of the fillers. A well evenly distributed network of nano-fillers is desirable is it will effectively block or at least slow down the permeation of the moisture and small molecules through the LCP nanocomposite 301. Aggregation of the fillers will form larger clumps, and may cause some areas to have no fillers where moisture and small molecules can travel or diffuse through more or less unabated, thereby resulting in the LCP nanocomposite 301 no longer being hermetic.

[0051] Aspect ratio is the ratio of a particular object's width to its height. Preferably, nano-fillers 304 are shaped such that they have an aspect ratio of higher than 10. A nano-filler 304 with a high aspect ratio has more surface area in serving as a barrier for the moisture and small molecules. Another advantage of nano-fillers having a high aspect ratio is that it improves the fiowability of the LCP nanocomposite 301 when it is subjected to injection molding. Injection molding involves heating the LCP nanocomposite 301 in a heated barrel till it liquefies, and then forcing the liquefied LCP nanocomposite 301 into a mold cavity where it cools and hardens to form pellets through cutting. The fiowability of the LCP nanocomposite 301 refers to the capability of the liquefied LCP nanocomposite 301 to move from the heated barrel to the mold cavity.

[0052] Exemplary shapes of the nano-fillers 304 can be found in Figures 5 (a), (b), (c) and (d). The shapes in Figures 5 (a), (b), (c) and (d) have high aspect ratios. Preferably, the nano-fillers 304 have irregular shapes (no lines of symmetry and all the sides are not the same).

[0053] Compatibilizers 305 are organic materials (i.e. materials that have carbon) used to chemically join or bond the nano-fillers 304 onto the amorphous segments 302 and crystalline segments 303 of the LCP 301. Figure 6 shows nano-fillers 304 being joined or bonded to an amorphous segment 302 or a crystalline segment 303 via the compatibilizers 305. Preferably, multiple nano-fillers 304 are joined or bonded to any one amorphous segment 302 or crystalline segment 303. This is to ensure that the nano-fillers 304 are well-distributed and cover enough intermolecular spaces for the LCP nanocomposite 301 to be hermetic.

[0054] The chemical bond formed by the compatibilizers 305 prevents phase separation of the nano-fillers 304 from the amorphous segments 302 or crystalline segments

303. Preventing phase separation is important as if the nano-fillers become separated, they may aggregate together and as explained previously, aggregation may result in the LCP nanocomposite 301 losing its hermeticity.

[0055] Referring back to Figure 3, adhesion promoters 306 are powdered solid epoxy resins that are added to the LCP nanocomposite 301 to improve the bonding strength of the LCP nanocomposite 301 to the metallic substrates (e.g. lead frame) which form the electrical input/output path of the electronic packages.

[0056] During the shaping of the LCP nanocomposite 301 , the LCP nanocomposite

301 will be subjected to a temperature drop from a higher processing temperature to a lower room temperature which may result in non-uniform cooling and thus warpage issues. To address this problem, powdered inorganic (i.e. materials that do not contain carbon) particles 307 are added to the LCP nanocomposite 301 to mitigate the occurrence of warpage issues by altering the rheology of the LCP nanocomposite 301. The inorganic particles 307 are rigid and micro-sized (which are large compared to the other nano-sized particles in the LCP nanocomposite 301). Therefore, the presence of these rigid "larger" sized inorganic particles 307 increases the overall rigidity of the LCP nanocomposite 301. Examples of inorganic particles 307 are C_aC0₃ (calcium carbonate), B_aC0₃, B_aS0₄ and M_gC0₃ micro particles.

[0057] LCP nanocomposites 301 (especially the crystalline segments) are vulnerable to themo-oxidative degradation especially when the LCP nanocomposites 301 are exposed to temperatures higher than 300°C. Anti-oxidants 308 are molecules that inliibit the oxidation of other molecules. Anti-oxidants 308 when added to the LCP nanocomposite 301 prevent themo-oxidative degradation which is advantageous because the anti-oxidants 308 can effectively absorb ultra-violet light, and therefore reduce themo-oxidative degradation. Examples of anti-oxidants 308 are anti-oxidant 1010 and anti-oxidant 168.

[0058] Figure 7 shows the steps of making a LCP nanocomposite in accordance with a preferred embodiment of the invention.

[0059] Step 1 : Mix nano-fillers with compatibilizers. Bonds are formed between the nano-fillers and compatibilizers. Preferably, the nano-fillers and the compatibilizers are in a powdered form. The advantage of first mixing the nano-fillers with compatibilizers is that the compatibilizers form an easier and stronger bond with the amorphous and crystalline segments of the LCP, as compared to if the nano-fillers are mixed directly with the LCP. Therefore, when the nano-fillers (bonded to the compatibilizers) are added to the LCP, the compatibilizers portion bonds readily to the amorphous and crystalline segments of the LCP (see figure 6), and thereby ensuring proper placement of the nano-fillers and reducing the possibility of aggregation of the nano-fillers.

[0060] This chemical bond prevents phase separation between the nano-fillers and the amorphous segments or crystalline segments. Preventing phase separation is important as if the nano-fillers become separated, they may aggregate together

[0061] Step 2: Mix a LCP matrix (which will act as the resin) with glass fibers to form a LCP nanocomposite. Preferably, the LCP matrix is in a powdered form. Preferably, the proportion of glass fibers is 10 to 50 parts by weight.

[0062] Step 3: Mix adhesion promoters with the LCP nanocomposite. Preferably, the adhesion promoters are in a powdered form. Preferably, the proportion of adhesion promoters is 1 to 10 parts by weight.

[0063] Step 4: Mix inorganic particles with the LCP nanocomposite. Preferably, the inorganic particles are in a powdered form.

[0064] Step 5: Mix anti-oxidants with the LCP nanocomposite. Preferably, the antioxidants are in a powdered form. Preferably, the proportion of adhesion promoters is 0.1 to 1 parts by weight.

[0065] Step 6: Mix the nano-fillers (bonded to the compatibilizers) with the LCP nanocomposite. Preferably, the proportion of nano-fillers is 10 to 30 parts by weight. Preferably, the proportion of compatibilizers is 1 to 10 parts by weight.

[0066] Step 7: Mechanically blend the LCP nanocomposite. This can be done via injection molding in which the LCP nanocomposite is fed into a heated barrel, and forced into a mold cavity where it cools and hardens to form pellets of the LCP nanocomposite. [0067] Table 1 below shows the compositions and exhibited properties of sample LCP nanocomposites made in accordance with the invention.

Table 1 : Compositions and exhibited properties of sample LCP nanocomposites

[0068] It is apparent from table 1 that LCP nanocomposites made in accordance with the invention exhibit good hermetic performance i.e. low leakage rate. A lower leakage rate means that it exhibits better hermetic properties. The LCP nanocomposites also exhibit good dimensional stability (high values for surface resistivity, tensile strength and impact strength).

[0069] Table 2 below shows the exhibited properties of sample LCP nanocomposites as a result of different nano-fillers.

Table 2: Sample data of LCP nanocomposites

[0070] Table 2 shows how low leakage rates (i.e. high hermetic performance) can be achieved using different recipes of nano-fillers (i.e. wollastonite, kaolin, talcum powder and mica minerals) and anti-oxidants (i.e. 1010 (AO-1) and 168 (AO-2)). The proportions of the LCP content, nano-fillers and anti-oxidants are in parts. For example, LCP nanocomposite LCP1/WS has 100 parts LCP, a range of between 1 to 15 parts wollastonite minerals (nano- filler), a range of 1 to 10 parts compatibilizers, a range of 0.10 to 0.25 parts anti-oxidant 1010 and a range of 0.10 to 0.25 parts anti-oxidant 168, and LCP nanocomposite LCPl/KL-1 has 100 parts LCP, a range of between 1 to 5 parts kaolin minerals (nano-filler), a range of 1 to 10 parts compatibilizers, a range of 0.10 to 0.25 parts anti-oxidant 1010 and a range of 0.10 to 0.25 parts anti-oxidant 168.

[0071] Table 2 also shows that LCP nanocomposites with higher portions of nano- fillers do not necessarily exhibit lower leakage rates (or better hermetic performance). This phenomenon is due to the fact that a higher portion of nano-fillers will lead to a higher probability of aggregation i.e. clumping or grouping together of the nano-fillers, causing phase separation (i.e. breaking the bonds) of the nano-fillers with the crystalline or amorphous segments of the LCP. This may thus result in the nano-fillers being unevenly distributed, and may cause certain regions to have no nano-fillers. Moisture and small molecules can thus travel or diffuse easily through these regions, affecting the hermeticity of the LCP nanocomposite.

[0072] The applications of the LCP nanocomposites made in accordance with the invention are numerous. For instance, the LCP nanocomposites can be used in the fabrication of Quad Flat No-lead (QFN) packages for Microelectromechanical systems (MEMS). QFN packages are thermally enhanced standard size integrated circuit (IC) packages designed such that the thermal pad is exposed at the bottom of the IC, which therefore results in a low thermal resistance path between the thermal pad and the exterior of the package. Perimeter lands on the QFN packages provide electrical connections to the printed circuit boards (PCB).

[0073] Figure 8 shows the steps of fabricating QFN packages using the LCP nanocomposites.

[0074] Step 1 : Fabricate half-etched lead frame.

[0075] Step 2: Injection mold the LCP nanocomposite onto the lead frame to create a pre-molded QFN open cavity substrate. Figures 9 and 10 show perspective and top views of the pre-molded QFN open cavity substrate. The pre-molded QFN open cavity substrate has LCP nanocomposite walls 402, lead portions 403 and a thermal pad 404.

[0076] Step 3: Insert IC into the cavity of the substrate and use thermal adhesive to attach the IC to the thermal pad. [0077] Step 4: Bond wires to electrically connect the IC to the lead frame.

[0078] Step 5: Seal QFN open cavity substrate with a hermetic lid to complete the

QFN package.

[0079] One skilled in the art will appreciate that above method can be applied to make saw singulation or punch singulation QFN packages.

[0080] Figure 1 1 shows a cross-sectional side view of a QFN package 401 made from the above method. QFN package 401 has LCP nanocomposite walls 402, lead portions 403 and a thermal pad 404. In the interior of QFN package 401 is an integrated circuit 405 adhered to the thermal pad 404 with thermal adhesive 406. Wire 407 electrically connect bond pad 408 on the integrated circuit 405 to the lead portion 403. Cover lid 409 seals the QFN package 401. The cover lid 409 is hermetic, and can be made up of a metal (e.g. aluminum, nickel, copper, stainless steel) or glass or ceramic (A1₂0₃) or the LCP nanocomposite. As the LCP nanocomposite walls 402, lead portions 403, thermal pad 404, and cover lid 409 are hermetic, therefore if follows that the QFN package 401 is also hermetic.

[0081] Another advantage is that QFN packages made with LCP nanocomposite will have a smaller form factor when compared to conventional QFN packages made with ceramic because LCP nanocomposite is smaller, thinner, and lighter in size than ceramic, which results in more units per lead frame. LCP nanocomposite is also cheaper than ceramic and therefore QFN packages made with LCP nanocomposite are cheaper.

[0082] It will be apparent that various other modifications and adaptations of the application will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the application and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

1. A method for preparing a nanocomposite comprising the step of :

mixing nano-fillers with a Liquid Crystalline Polymers (LCP) matrix to form the nanocomposite, the LCP matrix having segments and intermolecular spaces between the segments;

wherein the nano-fillers are hermetic and nano-sized, and are molecularly arranged in the intermolecular spaces such that the nanocomposite is hermetic.

2. The method of claim 1 wherein prior to the step of mixing nano-fillers with a Liquid Crystalline Polymers (LCP) matrix to form the nanocomposite, compatibilizers are mixed with the nano-fillers; and wherein compatibilizers are organic materials that chemically bond the nano-fillers to the segments.

3. The method of any one of the preceding claims further comprising the step of mixing adhesion promoters with the nanocomposite, wherein adhesion promoters are solid epoxy resins that improve the metallic bonding strength of the nanocomposite.

4. The method of any one of the preceding claims further comprising the step of mixing inorganic particles with the nanocomposite, wherein inorganic particles are rigid and micro-sized particles that increases the rigidity of the nanocomposite.

5. The method of any one of the preceding claims further comprising the step of mixing anti-oxidants with the nanocomposite.

6. The method of any one of the preceding claims further comprising the step of mixing glass fibers with the nanocomposite.

7. The method of any one of the preceding claims wherein the nano-fillers are any one of the following: wollastonite minerals, kaolin minerals, talcum powder minerals and mica minerals.

8. The method of any one of the preceding claims wherein the nano-fillers have an aspect ratio of higher than 10.

9. The method of claim 4 wherein the inorganic particles are any one of the following: C_aC0₃, B_aC0₃, B_aS0₄ and M_gC0₃ micro particles.

10. The method of claim 5 wherein the anti-oxidants are any one of the following: antioxidant 1010 molecules and anti-oxidant 168 molecules.

1 1. A nanocomposite comprising :

a Liquid Crystalline Polymers (LCP) matrix, the LCP matrix having segments and intermolecular spaces between the segments;

nano-fillers, wherein the nano-fillers are hermetic and nano-sized, and are molecularly arranged in the intermolecular spaces such that the nanocomposite is hermetic.

12. The nanocomposite of claim 11 wherein the nanocomposite further comprises compatibilizers and compatibilizers are organic materials that chemically bond the nano-fillers to the segments.

13. The nanocomposite of claims 1 1 or 12 wherein the nanocomposite further comprises adhesion promoters and adhesion promoters are solid epoxy resins that improve the metallic bonding strength of the nanocomposite.

14. The nanocomposite of any one of claims 1 1 to 13 wherein the nanocomposite further comprises inorganic particles and inorganic particles are rigid and micro-sized particles that increases the rigidity of the nanocomposite.

15. The nanocomposite of any one of claims 1 1 to 14 wherein the nanocomposite further comprises anti-oxidants.

16. The nanocomposite of any one of claims 1 1 to 15 wherein the nanocomposite further comprises glass fibers.

17. The nanocomposite of any one of claims 11 to 16 wherein the nano-fillers are any one of the following: wollastonite minerals, kaolin minerals, talcum powder minerals and mica minerals.

18. The nanocomposite of any One of claims 11 to 17 wherein the nano-fillers have an aspect ratio of higher than 10.

19. The nanocomposite of any one of claims 11 to 18 wherein the proportion of nano- fillers is 10 to 30 parts by weight.

20. The nanocomposite of claim 12 wherein the proportion of compatibilizers is 1 to 10 parts by weight.

21. The nanocomposite of claim 16 wherein the proportion of glass fibers is 10 to 50 parts by weight.

22. The nanocomposite of claim 13 wherein the proportion of adhesion promoters is 1 to 10 parts by weight.

23. The nanocomposite of claim 15 wherein the proportion of anti-oxidants is 0.1 to 1 parts by weight.

24. The nanocomposite of claim 14 wherein the inorganic particles are any one of the following: C_aC0₃, B_aC0₃, B_aS0₄ and M_gC0₃ micro particles.

25. The nanocomposite of claims 15 or 23 wherein the anti-oxidants are any one of the following: anti-oxidant 1010 molecules and anti-oxidant 168 molecules.

26. A Quad Flat No-lead (QFN) package for Microelectromechanical systems (MEMS) devices comprising a substrate comprising the nanocomposite of any one of claims 1 1 to 25.