GB2441801A

GB2441801A - Optical interconnection of components within a housing which has a reflective surface

Info

Publication number: GB2441801A
Application number: GB0618148A
Authority: GB
Inventors: Raymonde Gene Clifford Artus
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-09-15
Filing date: 2006-09-15
Publication date: 2008-03-19
Anticipated expiration: 2026-09-15
Also published as: WO2008062452A3; GB0618148D0; WO2008062452A2; GB2441801B

Abstract

A component assembly 10 comprising a housing 12 having an internally reflective surface 14; a plurality of optical components 16 located in the housing 12; and an optical medium 44 in direct contact with each optical component 16, for optically connecting each optical component 16 to at least one other optical component 16, whereby optical data may be transferred between the optical components 16 in the assembly 10. The optical medium may be a liquid such as paraffin or silicon oil containing scattering particles to aid diffusion of light. The reflective surface may be a Lambertian surface.

Description

2441801

A COMPONENT ASSEMBLY

The present invention relates to a component assembly, and particularly, but not 5 exclusively to a component assembly that allows the transfer of optical data between components in the assembly.

It is known in the art to include complex circuits within a single module comprising a plurality of components such as microchips arranged in arrays and 10 interconnected with one another. It is desirable to be able to pass data between assemblies of components within the module at frequencies greater than that reasonably possible using wire bond leads.

In such circumstances use can be made of various optical means of data transfer, 15 for example optical fibre and wave-guides. However, such optical means are difficult and expensive to implement, and in particular, are especially not conducive to multiple channel data transfer processes within a module.

According to the invention there is provided a component assembly comprising: 20 a housing having an internally reflective surface;

a plurality of optical components located within the housing; and an optical medium in direct contact with each optical component, for optically connecting each optical component to at least one other optical component, whereby optical data may be transferred between the optical 25 components in the assembly.

By means of the present invention data, in the form of optical signals may be transmitted to all optical components within the housing via the optical medium and the reflecting surface on the inside of the housing, thereby obviating the need 30 for optical fibre or wave-guide signal transfer.

The optical components are located within a cavity in the housing, and the optical medium occupies the remaining space within the cavity.

1

The optical components may be arranged within the cavity of the housing in any orientation. Ideally the optical components are arranged in such a way as to facilitate electrical power connection and allow component-to-component wire 5 interconnects to be made.

The optical components may be arranged in arrays within the housing, preferable in three dimensional arrays in order to maximise the optical component density in the component assembly.

10

Preferably each optical component comprises at least one optical data emitter for transmitting optical signals and at least one optical data detector for detecting a transmitted optical signal.

15 Preferably the reflecting surface is totally reflective.

Preferably the internally reflective surface of the housing scatters light in substantially all directions. Optical signals may thus be diffusely transmitted to all the optical components in the array. This reflection and scattering from the 20 internally reflective surface may be enhanced by means of at least one surface area forming part of the internally reflective surface having matt properties.

A surface is said to have matt properties if it has the ability to diffusively reflect light.

25

Ideally the or each surface area having matt properties is a Lambertian type surface area.

Advantageously, substantially all of the internally reflective surface of the housing 30 is a Lambertian type surface.

A Lambertian type surface is a surface which adheres to Lamberts cosine law. That is to say, the reflected or transmitted luminous intensity in any direction from

2

the surface varies as the cosine of the angle between that direction and the normal vector of the surface. As a consequence, the luminance of a Lambertian type surface is the same regardless of the viewing angle.

5 Thus, due to the fact that the internally reflective surface of the housing comprises a Lambertian type surface, the diffusion or acceptance of any signal into a communal optical path is enhanced, as the luminance of the internally reflective surface will be the same regardless of the viewing angle. This means that a greater volume of the optical medium will be illuminated than if the internally reflective 10 surface did not comprise a Lambertian surface, thus enhancing the scattering of the transmitted signal.

The phrase "communal optical path" is used to describe a transmission path through the volume of the optical medium. The transmission path is communal in 1 5 that all optical signals may use the path.

Ideally the Lambertian type surface area comprises a plurality of bumps or dimples of the same scale as the wavelengths of the optical signals and has a diffusing reflection coefficient of 0.75 or better.

20

Preferably a Lambertian type surface area is located immediately in front of or opposite an optical data emitter.

Instead of having a Lambertian type surface area, the internally reflective surface 25 may comprise a polished metal surface area with a reflection coefficient of 0.85 or better. Preferably the polished metal surface is an aluminium, silver or gold polished surface.

Alternatively, the internal reflective surface may comprise a surface area coated

30 with a suitable dielectric coating such as but not limited to Ti(>2, ZnS or MgF2.

Such a surface would enhance the reflectivity of the internal reflective surface for a smaller range of wavelengths to better than 0.999.

3

Conveniently the optical medium scatters light in three dimensions in a similar manner to a mist.

Advantageously the optical medium comprises a plurality of scattering centres.

5

The scattering centres in the optical medium provide the equivalent of a 'mist' or 'fog' to emitted light, so that when any optical data emitter within the housing is switched on, substantially the entire volume of the optical medium within the housing will be illuminated in a diffuse mode.

10

It is well known that in a mist or fog, infrared radiation or radiation having wavelengths longer than the dimensions of the scattering particles is not scattered. The provision of scattering centres with a wide range of sizes ensures that light of any wavelength within a wide range of wavelengths will be scattered.

15

In a preferred embodiment of the invention, the scattering centres comprise particles of optically clear crystalline substances.

An object is said to be "optically clear" if the object is transparent to the 20 wavelength of a transferred signal. That is to say that the wavelength of the transferred signal is scattered only and not absorbed by the object.

The wavelength of a transferred signal may be of any wavelength that is compatible with the transmission/absorption properties of the optical medium and 25 the reflective surface of the housing.

Conveniently the crystalline substances are selected from a group comprising sapphire, diamond, moisanite, cubic boron nitride, cubic zirconium and glass. However the crystalline substances may be a mixture of any of these materials.

30

In another preferred embodiment of the invention, the scattering centres comprise particles of optically clear plastics material.

4

Preferably (he scattering centres have a wide range of sizes, typically no larger than 100 microns.

Advantageously the optical medium further comprises an optically clear liquid and S the scattering centres are dispersed into the optically clear liquid.

Conveniently the refractive index of the optically clear liquid is different from that of the scattering centres in order to assist the scattering of the light.

10 Ideally, there is a significant difference in the refractive index of the optically clear liquid when compared with that of the scattering centres.

The optically clear liquid may be an organic liquid such as a paraffin, preferably n-decane paraffin.

15

Alternatively the optically clear liquid may be an inorganic liquid such as a silicon oil.

Thus by means of the invention, optical data injected into the medium may be 20 captured by any optical component that is embedded within the optical medium and optical data transfer may be obtained throughout the entire volume.

The scattering of light by the scattering centres is achieved by means of reflection or refraction. The likelihood of absorption of the transmitted signal by the optical 25 medium is low since the scattering centres and the optically clear liquid are transparent.

The amount of light that is reflected by any scattering centre is given by:-

30 R=[(ni-n2)/(ni + n2)]2 where nj = refractive index 1 (optically clear liquid)

n2 = refractive index 2 (scattering centre).

5

If the indices ni and m are the same, then no light is refracted and all light is scattered only from the internally reflective surface.

Light emitted from any optical component within the housing may be either 5 coherent or non coherent. The light emitted from an optical component, will be scattered both by scattering centres that are larger than the wavelength of the light, and by the internally reflective surface. This scattering will take place throughout the volume of the optical medium and hence will illuminate all optical components that are embedded in the optical medium, or that are exposed to or are 10 in contact with the optical medium.

Different wavelengths of light may be transmitted simultaneously and thus provide a number of independent channels of communication. The different wavelengths of light will each equate to a different channel of communication.

15

Several signals may be transmitted simultaneously via the communal optical path by utilising different wavelengths for the optical data emitters. The separation of signals or channel separation by wavelength may be further enhanced by means of suitable optical filters on the surface of a receiving optical component.

20

It is well known that some optical components are adversely affected on being generally irradiated with light causing the generation of excessive noise etc.

The optical filters have the added benefit of removing or significantly reducing 25 these adverse effects that may occur through general irradiation of the optical component with light.

The adverse effects may also be eradicated by reflectively transmitting signals between particular optical components via a confined optical channel laid directly 30 at the surface of an array linking only specific optical components and embedded into the optical medium.

6

In addition, particular areas of the internally reflective surface of the housing may be omitted or masked, to remove or significantly reduce any adverse effects that may be caused by general irradiation.

The invention will now be described by way of a non-limiting example with reference being made to the accompanying drawings in which:

Figure 1 is a perspective view of a component assembly according to the present invention; and

Figure 2 is a schematic view of the component assembly of Figure 1 showing a diffusion process forming part of the optical data transfer process according to the present invention.

Referring to Figure 1, a component assembly 10 according to the invention is shown.

The component assembly comprises a housing 12; a plurality of optical components 16; and an optical medium 44 (not shown) in direct contact with each component 16.

The optical components 16 are operatively located in the housing 12.

The optical components 16 may be located in the housing in any orientation, for example, the optical components 16 may be arranged in arrays within the housing 12 as shown in Figure 1.

In a preferred embodiment, each optical component 16 is a die assembly.

Each die assembly 16 is in the form of an optical data signal transfer assembly having at least one optical emitter 30 for transmitting optical signals to one or more other die assemblies 16 and least one optical detector 36 for detecting a transmitted signal.

7

The optical emitter 30 may transmit optical signals of any type, that is to say, it may transmit coherent or non-coherent signals. For example, the optical emitter 30 may be a laser emitter 32 or an L.E.D emitter 34.

5

In the embodiment shown in Figure 1, each die assembly comprises a laser emitter 32 and an L.E.D emitter 34.

The die assemblies 16 may be arranged in an array on a printed circuit board, to 10 create a sub-assembly circuit 28. The printed circuit board may be either a flexible or a rigid circuit board.

Alternatively, the die assemblies 16 may be arranged on a flexible film circuit to create a sub-assembly circuit 28. In such an arrangement, the die assemblies 16 15 may be mounted on both sides of the flexible film circuit.

The component assembly 10 may comprise a plurality of sub-assembly circuits within the housing. As such, the size of the housing 12 will be dependent on the number of sub-assembly circuits 28 being located in the housing.

20

The housing 12 comprises a body portion 18 comprising a cavity 20 and having at least one opening for permitting access to the cavity 20. The housing further comprises at least one corresponding lid 22 for covering the respective opening in order to restrict access to the cavity 20.

25

In the embodiment shown in Figure 1, the body portion 18 comprises an opening at each of the opposite faces 21 of the body portion 18, and two corresponding lids 22 for sealing the cavity 20.

30 Preferably, the or each sub-assembly circuit 28 is primarily housed within the cavity 20 of the housing 12.

8

The housing further comprises an internally reflective surface 14 for scattering light in a plurality of directions. The internally reflective surface 14 allows optical data to be diffusely transmitted to all the die assemblies 16 in the array.

5 In a preferred embodiment, the internally reflective surface 14 comprises a Lambertian type surface area.

The diffusion or acceptance of any optical signal into a communal optical path is enhanced by a Lambertian type surface area forming part or all of the internally 10 reflective surface 14 of the housing.

It is preferred that the internally reflective surface 14 comprises a plurality of Lambertian type surfaces areas which are located immediately in front of or opposite a optical data emitter 30.

15

Each die assembly 16 may further comprise a suitable optical filter (not shown in the figures) for blocking stray light. As a result, adverse effects that may be caused by general irradiation of the die assemblies 16 i.e. the generation of excessive noise etc, are removed or significantly reduced.

20

Alternatively, particular areas of the internally reflective surface 14 of the housing 12 may be masked or omitted in order to eradicate the adverse effects cause by general irradiation.

25 The housing 12 further comprises at least one port 38,40 through which the die assemblies 16 may be connected to an external device. Hie die assemblies 16 may either be electrically or optically connected to an external device.

In the embodiment shown in Figure 1, the housing 12 comprises an electrical 30 connection port 38 and an optical connection port 40.

The electrical connection port 38 and the optical connection port 40 are connected to the die assemblies 16 via the circuit board of a respective sub-assembly 28. This

9

may be achieved by means of an electrical connection port 38 in the form of an electrical feed-through and an optical connection port 40 in the form of a fibre optic inter-connect.

5 Referring to Figure 2, it can be seen that the optical medium 44 comprises a plurality of scattering centres 46 dispersed in an optically clear liquid 48. The optically clear liquid 48 is preferably either an n-decane paraffin or a silicone oil.

The optical medium 44 fills the cavity 20 of the housing 12 and optically connects

10 each die assembly 16 to at least one other die assembly 16 such that optical data may be transferred between the die assemblies 16 within the cavity 20. The transfer of data between the die assemblies 16 will be described in more detail below.

15 The scattering centres 46 may comprise particles of optically clear crystalline substances selected from a group comprising sapphire, diamond, Moisanite, cubic boron nitride, cubic zirconium and glass. The crystalline substances may be composed of a single element or a mixture of elements selected from the group.

20 Optical connection between the optical components 16 is achieved via the scattering centres 46 in the optical medium 44 which provide the equivalent of a 'mist* or 'fog' to light emitted from an optical emitter 30, so that when any optical emitter 30 within the cavity 20 is switched on, the entire volume within the cavity 20 is then illuminated in a diffuse mode.

25

The refractive index of the optically clear liquid 48 is preferably significantly different from that of the scattering centres 46 in order to assist the scattering of the light.

30 Thus by means of the invention, optical data injected into the medium 44 may be captured by any die assembly 16 that is embedded within the medium 44 and this optical data transfer may be obtained throughout the entire volume of the cavity 20.

10

The scattering of light by the scattering centres is achieved by means of reflection or refraction.

5 The amount of light that is reflected by any scattering centre is given by:-

R=[(ni-n2)/(ni + n2)]2 where ni = refractive index 1 (optically clear liquid)

n2 = refractive index 2 (scattering centre).

10 In an n-decane/diamond optical medium, the refractive indices are preferably about ni = 1.4103 and n2 = 2.42, giving a value of about R = 0.069

In a silicon oil/Moisanite optical medium, the refractive indices are preferably about ni = 1.3 n2 = 2.65, giving a value of about R = 0.117

15

In an optical medium 44 where the indices ni and n2 are the same, no light is refracted by the scattering centres and all light is scattered only from the Lambertian type surface.

20 The transmission of data between two die assemblies 16a, 16b within the component assembly 10 will now be described.

Firstly the optical emitter 30 of die assembly 16a is switched on and transmits a data signal 50 in the form of a light signal to the die assembly 16b.

25

The optical signal transmitted by the optical emitter 30 may be of any wavelength that is compatible with the transmission/absorption properties of the optically clear liquid 48, the scattering centres 46 and the reflecting surface 14 of the housing 12.

30 The transmitted signal will then be reflected by an internally reflective surface 14, which will in turn scatter the light signal in a number of directions.

11

The scattered light will be picked up by a scattering centre 46 which in turn redirects the light in a number of directions.

The optical detector element 36 of the die assembly 16b will be illuminated by the S scattered light, the detector 36 will then pick up the signal and the transmission is completed.

The light signal may be redirected on a plurality of occasions through a number of scattering centres before being received by the detector 36 of a different die 10 assembly 16.

Light of aily wavelength, emitted from any emitter 30 within the cavity 20, will be scattered by the internally reflective internal surface 14 and scattering centres 46 that are larger than the wavelength of the transmitted signal, throughout the entire IS volume of the optical medium 44 and hence will illuminate all die assemblies 16 or sub-assembly circuits 28 that are embedded within the housing and that are exposed to or are in contact with the medium 44.

Several signals may be transmitted simultaneously via the communal optical path 20 by utilising different wavelengths for the emitters 30. The different wavelengths of light may be used to provide a number of independent channels of communication.

In a preferred embodiment, signals between particular die assemblies 16 are 25 reflectively transmitted via a confined optical channel laid directly at the surface of the sub-assemblies 28 (see Figure 1) linking specific die assemblies.

Due to the requirement to house the die assemblies in relatively close confinement, heat from the die assemblies may affect the efficiency of the 30 component assembly.

The component assembly 10 according to the invention may therefore include means for cooling the die assemblies 16. As shown in Figures 1 and 2, this may

12

be in the form of fins 26 on the lids 22 for heat dissipation or through a heat sinking material embedded in the housing.

13

Claims

1. A component assembly comprising:

a housing having an internally reflective surface; s a plurality of optical components located in the housing; and an optical medium in direct contact with each optical component, for optically connecting each optical component to at least one other optical component, whereby optical data may be transferred between the optical components in the assembly.

10

2. An assembly according to Claim 1 wherein each optical component comprises at least one optical emitter and at least one optical detector.

3. An assembly according to Claim 1 or Claim 2 wherein the internally is reflective surface comprises at least one Lambertian type surface area.

4. An assembly according to Claim 2, or Claim 3 when dependent on Claim 2, wherein the or each Lambertian type surface area is located immediately in front of or opposite an optical data emitter.

20

5. An assembly according to Claim 1 or Claim 2 wherein the internally reflective surface is a Lambertian type surface.

6. An assembly according to Claim 1 wherein the internally reflective surface 25 is a polished metal surface with a reflection coefficient of 0.85 or better.

7. An assembly according to any one of Claims 1 to 6 wherein the optical medium comprises plurality of scattering centres.

30 8. An assembly according to Claim 7 wherein the scattering centres comprise particles of optically clear crystalline substances

14

9. An assembly according to Claim 8 wherein the crystalline substances are selected from a group comprising: sapphire; diamond; moisanite; cubic boron nitride; cubic zirconium and glass.

5 10. An assembly according to Claim 7 wherein the scattering centres comprise particles of optically clear plastics material.

11. An assembly according to any one of Claims 7 to 10 wherein the scattering centres have sizes no larger than 100 microns.

10

12. An assembly according to any one of Claims 7 to 11 wherein the optical medium comprises an optically clear liquid and the scattering centres are dispersed into the optically clear liquid.

15 13. An assembly according to Claim 12 wherein the optically clear liquid is an organic liquid.

14. An assembly according to Claim 13 wherein the organic liquid is a paraffin.

20

15. An assembly according to Claim 12 wherein the optically clear liquid is an inorganic liquid.

16. An assembly according to Claim 15 wherein the inorganic liquid is a 25 silicon oil.

17. An assembly as substantially hereinbefore described with reference to and/or illustrated in the accompanying drawings.

15