WO2001011697A1

WO2001011697A1 - Optocoupler on a metallized pcb and method of manufacturing the same

Info

Publication number: WO2001011697A1
Application number: PCT/US2000/021023
Authority: WO
Inventors: Ralph E. Simon
Original assignee: Qt Optoelectronics, Inc.
Priority date: 1999-08-04
Filing date: 2000-08-01
Publication date: 2001-02-15
Also published as: JP2003521107A; AU6509900A

Abstract

A device through which circuits communicate is disclosed. The device includes a substrate having a top surface and a bottom surface. A light emitter and a light detector are positioned over the top surface of the substrate. A light transmissive material couples the light emitter with the light detector. A plurality of electrical conductors extend along the top surface of the substrate and are each associated with a contact region. At least one of the electrical conductors provides electrical communication between the light emitter and the associated contact region and at least one other electrical conductor provides electrical communication between the light detector and the associated contact region.

Description

OPTOCOUPLER ON A METALLIZED PCB AND METHOD OF MANUFACTURING THE SAME

BACKGROUND OF THE INVENTION A. Field of Invention

The present invention relates to devices which permit communication between circuits which operate at different voltage potentials.

B. Description of Related Art Modern technology frequently requires communication between circuits which require electrical isolation from one another. For instance, computer systems often require communication between circuits operating at different potentials. Because the potential difference between these circuits is often quite large, they need to be electrically isolated from one another. An optocoupler is a device which permits communication between these circuits without electrically connecting them.

Optocouplers typically include a light emitter and a light detector connected to different leads of a lead frame. During operation of the optocoupler, electrical leads associated with the light emitter are typically connected with a circuit operating at one potential and electrical leads associated with the light detector are connected with another circuit operating at a different potential. When the light emitter receives a signal from its associated circuit, the light emitter produces a light signal. The light signal is transmitted to the light detector which converts the light signal to an electrical signal supplied to the circuit associated with the light detector. Accordingly, the optocoupler provides communication between the electrically isolated circuits. The typical optocoupler is formed by attaching the light emitter and the light detector to different leads on a lead frame. A light transmitting material is then formed over the light emitter and light detector. This light transmitting medium permits a light signal to be transmitted from the light emitter to the light detector. An opaque epoxy body is then formed around the light transmitting material in order to mechanically anchor the leads of the lead frame. This body also serves to electrically isolate the leads, protect the device from external forces and protect the light transmitting material from outside light. This body is typically formed using transfer molding techniques. The lead frame and transfer molding associated with the typical optocoupler are known to add considerable expense to the fabrication of optocouplers.

There is a need for an optocoupler associated with lower fabrication costs.

SUMMARY OF THE INVENTION

The invention relates to a device through which circuits communicate.

The device includes an insulating substrate having a top surface and a bottom surface. A light emitter and a light detector are positioned over the top surface of the substrate. A light transmissive material couples the light emitter with the light detector. A plurality of electrical conductors extend along the top surface of the substrate and are each associated with a contact region. At least one of the electrical conductors provides electrical communication between the light emitter and the associated contact region and at least one other electrical conductor provides electrical communication between the light detector and the associated contact region.

Another embodiment of the device includes a first reflective layer formed on the top surface of the substrate. The light emitter and a light detector are positioned over the top surface of the substrate. A light transmissive material is positioned over the first reflective layer and couples the light emitter with the light detector.

Yet another embodiment of the device includes a light emitter and two light detectors coupled with the top surface of the substrate. A light transmitting material couples two light detectors with the light emitter so as to conduct a light signal from the light emitter to both the first and second light detectors.

An additional embodiment of the device includes two light emitters and a light detector coupled with the top surface of the substrate. A light transmitting material couples the first and second light emitters with the light detector so as to conduct a first light signal from the first light emitter to the light detector and to conduct a second light signal from the second light emitter to the light detector.

The invention also relates to a method for manufacturing a device through which circuits communicate. The method includes providing a substrate upon which a light emitter and a light detector are mounted. The method also includes coupling a molded part to the substrate such that the light emitter and the light detector are at least partially positioned within a void defined by a concave surface of the molded part. The molded part has an injection port. The method also includes flowing a light transmitting material precursor into the void through the injection port and forming the light transmitting material precursor into a light transmitting material.

Another embodiment of the method includes providing a rigid and electrically insulative substrate and forming a first reflective layer on a portion of the substrate. The method also includes forming electrical conductors on a top surface of the substrate and coupling a light emitter and a light detector to the electrical conductors. The method further includes forming a light transmitting material on the first reflective layer so as to couple the light emitter with the light detector. Yet another embodiemnt of the method includes depositing a second reflective layer over the light transmitting material and forming a substantially opaque layer over the second reflective layer. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 provides a sideview of a device through which circuits communicate, representing an embodiment of the invention. Figure 2 provides a topview of a device through which circuits communicate, representing an embodiment of the invention.

Figure 3 provides a bottomview of a device through which circuits communicate, representing an embodiment of the invention.

Figure 4A illustrates formation of a first reflective surface and electrical conductors on the top surface of a substrate, representing an embodiment of the invention.

Figure 4B illustrates the electrical conductors coupled with a light detector and with a light emitter, representing an embodiment of the invention.

Figure AC illustrates a light transmitting material formed over the first reflective layer, representing an embodiment of the invention.

Figure 4D illustrates a second reflective layer and an opaque layer formed over the light transmitting material, representing an embodiment of the invention.

Figure 4E illustrates a completed device, representing an embodiment of the invention.

Figure 5 is a topview of a device with a top surface having 6 electrical conductors, representing an embodiment of the invention.

Figure 6 illustrates a method incorporating a hollow shell to form the light transmitting material, the second reflective layer and/or the opaque layer, representing an embodiment of the invention.

Figure 7 illustrates a device having a dome with a squared contour, representing an embodiment of the invention.

Figure 8 A illustrates a device having a plurality of output portions, representing an embodiment of the invention. Figure 8B illustrates a device having a plurality of light emitters, representing an embodiment of the invention.

Figure 9A is a topview of an enlarged substrate including a plurality of devices, representing an embodiment of the invention. Figure 9B is a topview of an enlarged substrate including a plurality of devices with contact regions formed on the top surface of the substrate.

DETAILED DESCRIPTION

The invention relates to a device through which circuits communicate.

The device includes a substrate having a top surface and a bottom surface. A light emitter and a light detector are positioned over the top surface of the substrate. A light transmitting material couples the light emitter with the light detector. The light transmitting material provides a channel for transmission of the light from the light emitter to the light detector.

The light emitter and the light detector are coupled with electrical conductors which are formed on the top surface of the substrate. These electrical conductors can also include contact regions formed on the top and/or bottom surfaces of the substrate. The substrate can include plated through holes. When the contact regions are on the bottom surface of the substrate, the electrical conductors can extend through plated through holes to provide electrical communication between the contact regions and the light emitter on the top surface of the substrate and/or between the contact regions and the light detector on the top surface of the substrate. As a result, the device provide communication between two external circuits by attaching the contact regions on the bottom surface of the device to contacts on the external circuits.

Positioning the contact regions on the bottom surface of the substrate makes the contact regions readily accessible for attachment to the external circuits. As a result, there is no need to bend the substrate and the substrate can be flat. The use of a flat substrate eliminates the need for a lead frame. Eliminating the lead frame provides a significant cost advantage. Further, a flat substrate can be rigid enough to provide additional structural integrity to the device. The added structural integrity can be sufficient to eliminate the need for encasing the light transmitting material in an epoxy body and accordingly eliminating the need for the transfer molding step.

A first reflective layer can be formed between the light transmitting material and the substrate. A second reflective layer can be formed over the light transmitting material. The first and second reflective layers provide surfaces adjacent to the light transmitting material which reflect light from the light emitter back into the light transmitting material. Reflecting the light back into the light transmitting material increases the intensity of light received at the light detector and accordingly increases the efficiency of the device.

The device can also include a substantially opaque layer formed over the second reflective layer. The substantially opaque layer reduces the quantity of light which enters the light transmitting material from outside the light transmitting material. As a result, the substantially opaque layer reduces interference from external sources.

The light transmitting material, the first and second reflective layers and the substantially opaque layer can all be formed with glob top encapsulation. The machinery for glob top encapsulation is cheaper then the machinery required for transfer molding. As a result, the present invention can reduce manufacturing costs.

Figure 1 provides a sideview of a device 10 through which circuits communicate. The device 10 includes a substrate 12 with a top surface 14 and a bottom surface 16. Suitable materials for the substrate 12 include, but are not limited to, printed circuit boards and epoxy glass laminates. A light emitter 18 and light detector 20 are positioned over the top surface 14 of the substrate 12. Suitable light emitters 18 include, but are not limited to, an LED, laser or light emitting structure and may include circuitry to drive the light emitter. Suitable light detectors 20 include, but are not limited to, light-sensitive diodes, triacs and transistors which may be connected to other digital and analogue output devices.

A light transmitting material 22 covers at least a portion of both the light emitter 18 and the light detector 20. Accordingly, the light transmitting material couples the light emitter 18 with the light detector 20. The light transmitting material 22 can be formed from materials such as silicones, epoxies and urethanes. A first reflective layer 24 is formed between the light transmitting material 22 and the top surface 14 of the substrate 12 and a second reflective layer 26 is formed over the light transmitting material 22. An opaque layer 28 is formed over the second reflective layer 26. Suitable materials for the opaque layer 28 include, but are not limited to, silicone, epoxy, polyurethane and Thermoset 310 by Thermoset Plastics, Inc. located in Indianapolis, Indiana. The opacity of the opaque layer 28 can be increased by adding black fillers, such as carbon black.

During operation of the device 10, the light emitter produces light signals detected at the light detector 20. The light transmitting material 22 acts as a channel which transmits the light signals between the light emitter 18 and the light detector 20. Light from the light emitter 18 can be reflected one or more times from the first and/or second reflective layers 24, 26 before being detected at the light detector 20. Accordingly, the first and second reflective layers 24, 26 increase the efficiency of the device 10 by causing light from the light emitter 18 to be reflected back into the light transmitting material 22.

The opaque layer 28 prevents stray light from outside the device 10 from entering into the light transmitting material 22 and can provide protection against mechanical stress. As a result, the opaque layer 28 reduces the opportunity for the light detector 20 to receive false signals from external sources.

Figure 2 provides a topview of the device 10. The light emitter 18 is coupled with two electrical conductors 34 extending along the top surface 14 of the substrate 12. Two of the electrical conductors 34 couple the light emitter 18 with contact regions 36 so as to provide electrical communication between the contact regions and the light emitter. Similarly, two other electrical conductors 34 couple the light detector 20 with the contact regions 36 so as to provide electrical communication between the contact regions and the light detector. Suitable materials for the contact regions 36 include, but are not limited to, gold plated copper. The substrate 12 is preferably an electrical insulator to prevent or minimize electrical communication between the electrical conductors 34 on the substrate 12. While the electrical conductors 34 are illustrated on top of the first reflective layer 24, the electrical conductors 34 can be positioned between the first reflective layer 24 and the substrate 12 provided electrical communication is retained between the electrical conductors 34 and the light emitter 18 and the light detector 20. Alternatively, electrical conductors can be included on the bottom surface to couple the electrical conductors 34 via plated-through-holes to contact regions which are positioned on the bottom surface of the substrate optionally remote from the plated- through-holes.

As illustrated in Figure 3, a bottom surface of the device 10 can optionally include a plurality of contact regions 36. The contact regions 36 can be in electrical communication with the contact regions 36 on the top surface 14 of the substrate 12 via metal plated through holes 40. Accordingly, the plating of the through holes 40 permits electrical communication between the contact regions 36 on the bottom surface 16 of the substrate 12 and the light emitter 18 and/or the light detector 20. Electrical conductors can also be included on the bottom surface of the substrate in order to couple the plated through holes to contact regions which are on the bottom surface of the substrate but are remote from the through holes.

When the device 10 includes contact regions 36 on the bottom surface 16 of the substrate 12, the device 10 can be mounted on the surface of a printed circuit board containing an external circuit. Aligning the contact regions 36 on the bottom surface 16 with contact regions on the printed circuit board incorporates the device 10 into the external circuit. Additionally, the contact regions 36 on the substrate can be aligned with the contacts of different circuits. For instance, the contact regions 36 in communication with the light emitter can be aligned with the contacts of a first external circuit while the contact regions in communication with the light detector can be aligned with the contacts of a second external circuit. This arrangement electrically isolates the first and second circuit while permitting communication between the two circuits through the device 10.

Plated through holes 40 can be coupled directly to the electrical conductors 34 without any need for contact regions 36 on the top surface 14 of the substrate 12. Accordingly, the use of contact regions 36 on the top surface 14 of the substrate 12 is optional. Although the through holes 40 are illustrated at an edge of the device 10, the through holes 40 can be apertures extending through a centralized portion of the substrate 12. Figures 4A-4E illustrate a process for manufacturing an embodiment of device 10 according to the present invention. In Figure 4A, the first reflective layer 24 is formed on the top surface 14 of a substrate 12 which includes through holes 40. The electrical conductors 34 and contact regions 36 are then formed over the substrate 12 and first reflective layer 24 using traditional techniques for laying metal traces. When the device 10 includes through holes, the through holes 40 can be plated along with the electrical conductors 34 and contact regions. In another embodiment of the method, the electrical conductors and the contact regions are independent of one another until each contact region is coupled with the associated electrical conductor. Figure 4B illustrates the light emitter 18 and the light detector coupled with electrical conductors 34. The attachment of the light emitter 18 and light detector 20 to the electrical conductors 34 can be done using automatic die bonding equipment. Typical automatic die bonding equipment will load the light emitter 18 and the light detector 20 into position relative to the substrate 12, apply electrically conducting adhesive to the substrate 12 and place the light emitter 18 and the light detector 20 onto the substrate 12. As illustrated, one or more wires 42 can be used to couple the light emitter 18 and light detector 20 with the electrical conductors 34. Suitable techniques for attaching the wires 42 to the electrical conductors 34 include, but are not limited to, thermosonic ball bonding and ultrasonic wedge bonding.

Figure 4C illustrates the light transmitting material 22 formed over the first reflective layer 24 so as to couple the light emitter with the light detector. The light transmitting material 22 can be formed with techniques such as transfer molding and glob-top encapsulation. Glob top encapsulation consists of flowing a light transmitting material 22 precursor onto a portion of the first reflective layer 24 where the light transmitting material 22 is to be formed. The light transmitting material 22 precursor is then cured to form a solid or semi- solid light transmitting material 22. The precursor can be air curing, UN light curing, or even heat curing. Suitable light transmitting material 22 precursors include, but are not limited to, clear silicones and epoxies in their fluid states. Flowing the light transmitting material 22 precursor onto the substrate 12 can be accomplished by several different techniques. For instance, a charge of the light transmitting material 22 precursor can be obtained on a rod or spatula by dipping the rod or spatula into a bath of the light transmitting material 22 precursor. The charge is then contacted with the portion of the device 10 where the light transmitting material 22 is to be formed. Alternatively, a syringe or other instrument with a hollow needle can be used to introduce the charge of light transmitting material 22 precursor onto the substrate 12. During glob-top encapsulation, the viscosity of the light transmitting material 22 precursor must be kept low enough that the precursor flows yet high enough that the light transmitting material 22 precursor takes the desired shape on curing. A technique for reducing viscosity is heating the substrate 12 prior to flowing the light transmitting material 22 precursor onto the substrate 12. When the substrate 12 is preheated, the substrate 12 is preferably heated to approximately 50 °C-200°C, more preferably approximately 70 °C- 150 °C and most preferably approximately 90 °C -120 °C.

Figure 4D illustrates the second reflective layer 26 and the opaque layer 28 formed over the light transmitting material 22. These layers can be formed by the transfer molding or glob top encapsulation methods described above or by painting the precursor on the light transmitting material 22. When glob top encapsulation is employed, the viscosity of the precursor must be low enough that the fluid flows over any previously formed structure. For instance, when the opaque layer 28 is formed via glob top encapsulation, the opaque layer 28 precursor must have a viscosity which is low enough that the precursor flows over the previously formed second reflective layer 26. When two or more layers are formed via glob top encapsulation, the two or more layers can be cured simultaneously. Alternatively, each layer can be cured sequentially after the previous layer has cured. This sequential process is often necessary because the light transmitting material 22, the second reflective layer 26 and/or the opaque layer 28 frequently have different curing schedules and/or state requirements. For instance, the typical cure schedules of Thermoset 310 are 16- 24 hours at 75°C, 6-8 hours at 95°C, and 2-3 hours at 120°C while the typical cure schedules of Sylgard 527 are 4 hours at 65°C, 1 hour at 100°C, and 15 minutes at 105°C.

The adhesion between the light transmitting material 22 and the first and second reflective layers 24, 26 can be increased by applying plasma discharge or equivalent surface treatment to the existing portions of the device 10 before forming the next layer. Similar treatments can be used to increase adhesion between the second reflective layer 26 and the opaque layer 28 and/or between the substrate 12 and the first reflective layer 24.

Figure 4E illustrates the completed device 10. The light transmitting material 22 (not shown), second reflective layer 26 (not shown) and opaque layer 28 are centrally formed on the substrate 12 to form a dome 62 on the substrate 12. The substrate 12 and electrical conductors 34 extend outward from the periphery of the light tranmsitting material 22.

Figure 5 illustrates an embodiment of the invention where both the light emitter and the light detector are each coupled with three contact regions 36. Both the light emitter 18 and the light detector 20 are directly mounted to a centrally located electrical conductor 34, they are also both connected to two additional electrical conductors 34 via wires 42. It can be appreciated that the larger number of contact regions 36 permit the illustrated embodiment to be integrated with an electrical system of greater complexity. Figure 6 illustrates another method for forming the light transmitting material 22, the second reflective layer 26 and/or the opaque layer 28. A hollow shell 50 is coupled with the substrate 12 such that the light emitter 18 and the light detector 20 are at least partially positioned within a void 52 defined by a concave surface of the hollow shell 50. More generically, the structure for defining the void 52 can be a mold. In the illustrated embodiment, the hollow shell 50 includes an injection port 54 and a vent 56. A light transmitting material 22 precursor 58 is flowed through the injection port 54 with a hypodermic needle or other fluid delivery device 60. While the light transmitting material 22 precursor is flowed through the injection port 54, air from within the void 52 of the hollow shell 50 can exit the hollow shell 50 through the vent 56. Once the light transmitting material 22 precursor is within the void 52 of the hollow shell 50, the light transmitting material 22 precursor is cured to form the solid or semi solid light transmitting material 22. The hollow shell 50 can be opaque with an inner reflecting coating thus providing the second reflective layer and the opaque layer 28. The hollow shell will be held in place by the cured light transmitting material.

Other embodiments of the device 10 can be formed with the various methods described above. For instance, a device 10 having six contacts on the top surface 14 of the substrate 12 can be formed as illustrated in Figure 5. Although not illustrated, another embodiment can include six contacts on the bottom surface of the substrate 12.

As illustrated in Figure 7, the shape of the dome is not limited to rounded geometries. For instance, the dome can have a squared shape which aids in picking up the device 10 from a flat surface. The squared shape can be a result of forming any of the light transmitting material 22, the second reflective layer 26 and/or the opaque layer 28 with a squared shape. For instance, if the light transmitting material 22 is formed with a squared shape, a second reflective layer 26 formed by glob top encapsulation will also adopt a squared geometry. The device 10 with a squared shape is preferably formed by employing glob top encapsulation to form the light transmitting material 22 and the second reflective layer 26 and employing transfer molding to form the opaque layer 28 into squared shape.

Referring to Figure 8 A the device 10 can include a light emitter 18, a first light detector 20 A and a second light detector 20B. As a result, a light signal from the light emitter 18 can be transmitted to both the first and second output circuits. As illustrated in Figure 8B, the device 10 can include a single light detector 20 and a plurality of light emitters 18 A, 18B. In still another embodiment (not shown), the device can include a plurality of light emitters and a plurality of light detectors.

The above embodiments of the device 10 can be mass produced as illustrated in Figure 9A. A plurality of devices 10 are formed on an enlarged substrate 12. A saw can be used along the vertical and horizontal saw lines 70 to separate devices 10. The plurality of through holes 40 in the enlarged substrate 72 can be formed before the formation of the domes. The through holes 40 can be plated before using the saw to separate the devices 10.

Figure 9B illustrates an enlarged substrate 72 for production of devices 10 without contact regions 36 on the bottom surface 16 of each device 10. It can be appreciated that there are no through holes illustrated in Figure 9B. In each of the device embodiments described above, the contact regions can be integral with the associated electrical conductors such that an electrical conductor has a contact region and an electrical conductor region. In other embodiments of the device, the contact regions and electrical conductors are formed on the substrate independent of one another and/or the contact regions and electrical conductors are independent of one another until each contact region is joined with the associated electrical conductors. Further, the electrical conductors can serve as the contact regions and/or the contact regions can serve as the electrical conductors. While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than limiting sense, as it is contemplated that modifications and combinations will readily occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A device through which circuits communicate, comprising: an insulating substrate having a top surface and a bottom surface; a light emitter and a light detector positioned over the top surface of the substrate; a light transmissive material coupling the light emitter with the light detector; and a plurality of electrical conductors which are each associated with a contact region and which extend along the top surface of the substrate, at least one of the electrical conductors providing electrical communication between the light emitter and the associated contact region and at least one other electrical conductor providing electrical communication between the light detector and the associated contact region.

2. The device of claim 1, wherein the substrate is an electrical insulator.

3. The device of claim 1, wherein the substrate is a printed circuit board.

4. The device of claim 1, wherein the electrical conductors are metal traces on the top surface of the substrate.

5. The device of claim 1 , wherein the contact regions are positioned on the top surface of the substrate.

6. The device of claim 1 , wherein the contact regions are positioned on the bottom surface of the substrate.

7. The device of claim 6, further comprising: plated through holes coupling the electrical conductors with the contact regions.

8. The device of claim 7, wherein the plated through holes are apertures extending through the substrate.

9. The device of claim 7, wherein the plated through holes are positioned at an edge of the substrate.

10. The device of claim 1, further comprising: a first reflective layer positioned between the light transmitting material and the top surface of the substrate.

11. The device of claim 10, wherein the first reflective layer is positioned between the light emitter and the substrate and between the light detector and the substrate.

12. The device of claim 1, further comprising: a second reflective layer formed over the light transmitting material.

13. The device of claim 1, further comprising: a second reflective layer formed over the light transmitting material; and an opaque layer formed over the second reflective layer.

14. The device of claim 1, wherein the substrate is flat and extends beyond the periphery of the light transmitting material such that at least a portion of the electrical conductors is positioned on the portion of the substrate extending beyond the periphery of the substrate.

15. The device of claim 1 , wherein the substrate is flat.

16. The device of claim 1 , wherein the light transmitting material at least partially covers both the light emitter and light detector.

17. A device through which circuits communicate, comprising: a substrate having a top surface and a bottom surface; a first reflective layer formed on the top surface of the substrate; a light emitter and a light detector over the top surface of the substrate; and a light transmissive material over the first reflective layer and coupling the light emitter with the light detector.

18. The device of claim 17, wherein the first reflective layer is positioned between the light emitter and the substrate and between the light detector and the substrate.

19. The device of claim 17, further comprising: a second reflective layer formed on the light transmitting material.

20. The device of claim 19, further comprising: a substantially opaque layer formed over the second reflective layer.

21. The device of claim 17, wherein the substrate is a printed circuit board.

22. The device of claim 17, further comprising: a plurality of electrical conductors which are each associated with a contact region and which extend along the top surface of the substrate, at least one of the electrical conductors providing electrical communication between the light emitter and the asscociated contact region and at least one other electrical conductor providing electrical communication between the light detector and the associated contact region.

23. A device through which circuits communicate, comprising: a substrate having a top surface and a bottom surface; a light emitter coupled with the top surface of the substrate; first and second light detectors coupled with the substrate; a light transmitting material coupling the first and second light detectors with the light emitter so as to conduct a light signal from the light emitter to both the first and second light detectors.

24. The device of claim 23, further comprising: a first reflective layer formed on the top surface of the substrate between the light transmitting material and the top surface of the substrate.

25. The device of claim 24, wherein the light emitter and the first and second light detectors are positioned on the first reflective layer.

26. The device of claim 23, further comprising: a plurality of electrical conductors which are each associated with a contact region and which extend along the top surface of the substrate, at least one of the electrical conductors providing electrical communication between the light emitter and the associated contact region and at least one other electrical conductor providing electrical communication between the light detector and the associated contact region.

27. A device through which circuits communicate, comprising: a substrate having a top surface and a bottom surface; first and second light emitters coupled with the top surface of the substrate; a light detector coupled with the top surface of the substrate; a light transmitting material coupling the first and second light detectors with the light emitter to conduct a first light signal from the first light emitter to the light detector and to conduct a second light signal from the second light emitter to the light detector.

28. The device of claim 27, further comprising: a first reflective layer formed on the substrate between the light transmitting material and the top surface of the substrate.

29. The device of claim 28, wherein the light emitter and the light detector are positioned on the first reflective layer.

30. The device of claim 27, further comprising: a plurality of electrical conductors which are each associated with a contact region and which extend along the top surface of the substrate, at least one of the electrical conductors providing electrical communication between the light emitter and the associated contact region and at least one other electrical conductor providing electrical communication between the light detector and the associated contact region.

31. A method for manufacturing a device through which circuits communicate, comprising: providing a substrate upon which a light emitter and a light detector are mounted; coupling a mold to the substrate such that the light emitter and the light detector are at least partially positioned within a void defined by a concave surface of the mold, the mold having an injection port; flowing a light transmitting material precursor into the void through the injection port; and forming the light transmitting material precursor into a light transmitting material.

32. The method of claim 31 , wherein the mold is a hollow shell and flowing the light conductive material precursor includes venting air located within the void through a vent in the hollow shell.

33. The method of claim 31 , further comprising; forming a reflective layer on the substrate before coupling the mold to the substrate.

34. The method of claim 31 , wherein the mold is opaque and has a reflective inner surface.

35. A method for manufacturing a device through which circuits communicate, comprising: providing a rigid and electrically insulative substrate; forming a first reflective layer on a portion of the substrate; forming electrical conductors on a top surface of the substrate; coupling a light emitter and a light detector to the electrical conductors; forming a light transmitting material on the first reflective layer so as to couple the light emitter with the light detector.

36. The method of claim 35, further comprising: forming a second reflective layer over the light transmitting material.

37. The method of claim 36, further comprising: forming a substantially opaque layer over the second reflective layer.

38. The method of claim 35 , further comprising : forming contact regions on the substrate such that the contact regions are coupled with the electrical conductors.

39. The method of claim 36, wherein the contact regions are formed on a bottom surface of the substrate.