Composite including a component and a glass material

Abstract

A composite includes a component and a glass or glass ceramic material. The component has a first coefficient of expansion .sub.1 and the glass or the glass ceramic material has a second coefficient of expansion .sub.2. The glass or the glass ceramic material has a surface with a thickness and thickness differences (TTV) within the surface, and thickness fluctuations (LTV). The composite has a residual stress in the glass or the glass ceramic material (WARP), and a geometric and material-physical degree of compatibility KG4.

Claims

1. A composite, comprising: a component; and a glass material which is a thin glass sheet having a thickness <300 m , wherein the component has a first coefficient of expansion .sub.1, wherein the glass material has a second coefficient of expansion .sub.2, wherein the glass material has a surface with a thickness and thickness differences (TTV) within the surface, thickness fluctuations (LTV), and a WARP, wherein the composite including the component and the glass material has a residual stress in the glass material, and wherein the composite has a geometric and material-physical degree of compatibility
KG=10.Math.(.sub.1/.sub.2).Math.((1(LTV/1.5))+(1(TTV/7))+(1(WARP/200))), wherein KG4.

2. The composite according to claim 1, wherein KG15.

3. The composite according to claim 1, wherein KG30.

4. The composite according to claim 1, wherein the component is an electronic component.

5. The composite according to claim 1, wherein the component is a substrate.

6. The composite according to claim 5, wherein the substrate is an electronic substrate.

7. The composite according to claim 1, wherein the component is a wafer.

8. The composite according to claim 1, wherein the first coefficient of expansion .sub.1 of the component is greater than or equal to the second coefficient of expansion .sub.2 of the glass material.

9. The composite according to claim 8, wherein at a maximum, the first coefficient of expansion .sub.1 is triple that of the second coefficient of expansion .sub.2 of the glass material.

10. The composite according to claim 1, wherein the difference in thickness (TTV) of the glass material within the surface is <10 m.

11. The composite according to claim 1, wherein the difference in thickness (TTV) of the glass material within the surface is <7 m.

12. The composite according to claim 1, wherein local fluctuations in thickness (LTV) of the glass material over a surface area of 25 mm.sup.2 or less is <5 m.

13. The composite according to claim 1, wherein local fluctuations in thickness (LTV) of the glass material over a surface area of 25 mm.sup.2 or less is <2 m.

14. The composite according to claim 1, wherein the WARP in the glass material is <300 m for a composite component with a diameter of 6 inches.

15. The composite according to claim 1, wherein the WARP in the glass material is <200 m for a composite component with a diameter of 6 inches.

16. The composite according to claim 1, wherein the component comprises one or more materials selected from the group of: silicon, lithium tantalate, lithium niobate, lithium tetraborate, glass, ceramic, silicon carbide, gallium nitrite, gallium arsenide, indium phosphide, sapphire and quartz.

17. The composite according to claim 1, wherein the glass material is a soda-lime glass, a borosilicate glass, or an alkali free alumino borosilicate glass.

18. The composite according to claim 1, wherein the glass sheet is a thin glass sheet having a thickness <200 m.

19. The composite according to claim 1, wherein the glass sheet is a thin glass sheet having a thickness <50 m.

20. The composite according to claim 1, wherein the composite comprises a bonding material for bonding of the glass material with the component.

21. The composite according to claim 20, wherein the bonding material is an adhesive material.

22. The composite according to claim 21, wherein the adhesive material can be cured with UV radiation.

23. A method to produce a composite including a component and a glass material, wherein the component has a first coefficient of expansion .sub.1, wherein the glass has a second coefficient of expansion .sub.2, wherein the glass material has a surface with a thickness and thickness differences (TTV) within the surface, thickness fluctuations (LTV), and a WARP, wherein the composite including the component and the glass material has a residual stress in the glass material, and wherein the composite has a geometric and material-physical degree of compatibility KG=10.Math.(.sub.1/.sub.2).Math.((1(LTV/1.5))+(1(TTV/7))+(1(WARP/200))), wherein KG4, wherein the glass material is a thin glass sheet having a thickness <300 m and wherein said method comprises: providing the component having the first coefficient of expansion .sub.1 and the glass material having the second coefficient of expansion .sub.2; stretching to smooth the glass material; wetting at least one of the surface of the component and the glass material with a thin layer of a bonding material; and pressing the component and the glass material to form the composite.

24. The method according to claim 23, wherein the stretching to smooth the glass material includes using suction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 is a composite according to the current state of the art, which leads to stress crack corrosion;

(3) FIG. 2A is a side view of a composite, according to an embodiment of the invention; and

(4) FIG. 2B is a top-view of the composite of FIG. 2A, according to an embodiment of the invention.

(5) Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 illustrates a composite according to the current state of the art. Composite 1 according to the current state of the art consists of a component 3 that is bonded together by means of an adhesive 5 with a glass 7 or a glass ceramic material 7. Adhesive 5 is inserted as an intermediate layer 9 between component 3 and glass 7. The thermal coefficient of expansion of component 3 is .sub.1, the thermal coefficient of expansion of the glass substrate is .sub.2. As is seen in FIG. 1, a coefficient of expansion .sub.1 of the material of the component that is lower than the coefficient of expansion .sub.2 of the glass substrate leads to a tensile stress occurring on the surface of the glass that is not wetted with adhesive, resulting in stress crack corrosion and long-range failure of the composite. The example in FIG. 1 clearly illustrates that adhesive 5 does not cover the entire surface of the glass or glass ceramic material which is also the case regarding the surface of the component. Accordingly, a bond of this type is not stable.

(7) FIGS. 2A and 2B illustrate a composite 10 according to an embodiment of the invention, including a component 12, in particular an electronic substrate and a glass substrate 14. FIG. 2A shows a side view of the composite and FIG. 2B illustrates a top view. Component 12 in the illustrated example is a piezo substrate comprising an input structure 20 that can also serve as output structure. As material for the piezo substrate, lithium niobate is predominantly used that has a thermal coefficient of expansion =12.Math.10.sup.6 1/K. In addition to input/output structure 20 the piezo substrate also shows an absorber 22. The piezo substrate serves to convert electronic GHz signals in input structure 20 into surface waves that enable a compact filter design. The surface wave spreading across the substrate is identified with 24. An AF32 glass having a thickness of 0.3 mm can be used as the glass substrate. AF32 glass is an alkali free alumino-borosilicate thin glass by Schott AG, Mainz. Alumino-borosilicate glass AF32 is characterized by excellent electric properties and a low thermal coefficient of expansion of 3.2.Math.10.sup.6 1/K. The surface roughness is <1 nm RMS, the electric constant at 1 MHz is 5.1, the refractive index n.sub.D is 1.5099 and the density after annealing at 40 C./h is 2.43 g/cm.sup.3.

(8) The geometric and material-physical degree of compatibility
KG=10.Math.(.sub.1/.sub.2).Math.((1(LTV/1.5))+(1(TTV/7))+(1(WARP/200)))
of the exemplary embodiment according to FIGS. 2A to 2B, with a value for the thickness difference TTV of 5 m, the thickness fluctuation LTV of 0.6 m and a WARP value of 130 m, as well as the stated values of .sub.1 for the electronic substrate and .sub.2 for the glass material, is
KG=46.12
which is greater than KG=15 and 30.

(9) Instead of the borosilicate glass AF32, a modified soda-lime glass, for example B270 can also be used.

(10) In the inventive design example according to FIGS. 2a and 2b the adhesive layer that is located between component surface and glass or glass ceramic surface is placed uniformly and with homogenous thickness on the surfaces due to the degree of compatibility KG>4, in contrast to the adhesive layer illustrated in FIG. 1 which, due to tensile stresses and unfavorable surface geometry does not display a surface that is completely covered with adhesive.

(11) Furthermore, design examples according to embodiments of the invention are provided.

(12) In a first design example the material used for the component in one exemplary embodiment is again lithium niobate with an .sub.1 of approximately 12.Math.10.sup.6 1/K. The glass material used is for example a special glass B270 by Schott AG, Hattenbergstrasse 10, 55120 Mainz with appropriately selected properties for LTV, TTV and WARP. Glass material B270 is a highly transparent modified soda lime glass. The coefficient of expansion of B270 is .sub.2=9.4.Math.10.sup.6 1/K. Glass B270 has a difference in thickness TTV in the selected design example of TTV=5 m. The fluctuation in thickness LTV of the glass is LTV=0.6 m. The WARP of the glass used in the design example described above is 130 m. The design example including lithium niobate in combination with B270 glass then has a

(13) $\begin{array}{c}\mathrm{KG}=10.Math.\left(\frac{12.Math.10E-61/K}{9\text{,}4.Math.10E-61/K}\right).Math.\\ \left[\left(1-\frac{0\text{,}6m.}{1\text{,}5m.}\right)+\left(1-\frac{5m.}{7m.}\right)+\left(1-\frac{130m.}{200m.}\right)\right]\\ =15.7\end{array}$
and therefore, a KG4, in particular 15. For a glass B270 with such specifications, a surprisingly stable bond is the result.

(14) Alternatively to glass material B270, other glass materials can also be used, for example glass AF32 by Schott AG, Hattenbergstrasse 10, 55120 Mainz.

(15) The coefficient of expansion .sub.2 of AF32 is 3.2.Math.10.sup.6 1/K. At the same values for the lithium niobate material and parameters TTV, LTV and WARP the following results

(16) $\begin{array}{c}\mathrm{KG}=10.Math.\left(\frac{12.Math.10E-61/K}{9\text{,}4.Math.10E-61/K}\right).Math.\\ \left[\left(1-\frac{0\text{,}6m.}{1\text{,}5m.}\right)+\left(1-\frac{5m.}{7m.}\right)+\left(1-\frac{130m.}{200m.}\right)\right]\\ =46.12,\end{array}$
and therefore, a KG15, preferably 30.

(17) The invention specifies for the first time a composite that, compared to composites that are known from the current state of the art distinguishes itself through longer lifespan of the composite, as well as greater compatibility of the materials. The composites according to the invention moreover are characterized by low residual stresses in the glass and high surface quality.

(18) Furthermore, excellent adhesion of the adhesive is provided in the composite as well as on the surface and also on the component surface.

(19) While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.