WO2010143175A1

WO2010143175A1 - An optical device module and production method

Info

Publication number: WO2010143175A1
Application number: PCT/IE2010/000038
Authority: WO
Inventors: John D. Lambkin; David Barrow; Vincent Hung; Patrick Doyle
Original assignee: Firecomms Limited
Priority date: 2009-06-12
Filing date: 2010-06-11
Publication date: 2010-12-16

Abstract

An optical device module has leads (1) arranged for connection of the module to an external circuit. A substrate (2) is patterned with electrical tracks on at least opposed surfaces and is secured to the leads (2). A signal processing integrated circuit (3) with an optical device driver or amplifier function is on the substrate (2) and is electrically connected to at least some of the substrate tracks. There is a moulding (7) around the substrate (2) leaving at least one opening (8) exposing part of the substrate (2), the moulding fully encapsulating the integrated circuit (3). An optical device (9) is mounted on the substrate (2) within the moulding opening (8). An optical coupler (11) is mounted in the moulding opening (8) and is in alignment with the optical device (9). In another embodiment, the substrate (201) has an opening (206) which is accessible via the moulding opening (228) and the optical device (202) is mounted on a side of the substrate (201) opposed to the moulding opening, and there is a light path between the coupler and the optical device via said opening. The substrate (201) may include alignment features (212) engaging mating alignment features (213) of the optical coupler.

Description

"An Optical Device Module and Production Method"

INTRODUCTION

Field of the Invention

The invention relates to the fabrication of optical devices for the transmission and receiving of modulated light signals.

A particular challenge is that of achieving a very low device profile due to the slim shape of many user portable hand-held devices.

The invention is therefore directed towards providing an optical device module which fits into a very slim device or connector housing and which provides for repeated good optical connections.

The invention is directed towards achieving an optical semiconductor module and its manufacture, in which:

- manufacture can be on a large scale and at a low cost; and/or

- the module has a very small footprint and is compatible with conventional surface mount technology; and/or

- the module is robust and reliable, and in particular can withstand a solder reflow process; and/or

- in such a small footprint with a high current-to-volume ratio, there is good thermal conductivity and efficiently dissipation of heat away from the package. - ability to be moulded into a small form connector which can incorporate electrical connections; and/or

- ability to be electro-optically tested on substrate prior to moulding,

SUMMARY OF THE INVENTION

According to the invention, there is provided an optical device module comprising: leads arranged for connection of the module to an external circuit; a substrate patterned with electrical tracks on at least opposed surfaces and being secured to the leads; at least one signal processing integrated circuit with an optical device driver or amplifier function on the substrate and being electrically connected to at least some of the substrate tracks; a moulding around the substrate leaving at least one opening each opening exposing part of the substrate, the moulding encapsulating the integrated circuit, at least one optical device mounted on the substrate within the moulding opening or openings, each said optical device being an optical emitter, detector, or transceiver; and an optical coupler mounted in each moulding opening and each in alignment with an optical device.

In one embodiment, the moulding includes non-transparent moulding resin material.

In one embodiment, the coupler comprises a lens. In one embodiment, the coupler comprises a lens of transparent resin. In one embodiment, the coupler comprises a lens of glass. In one embodiment, the coupler includes a light concentrator.

In one embodiment, the coupler comprises a fibre-retaining socket. In one embodiment, the fibre-retaining socket comprises an integrated lens of transparent resin.

In one embodiment, the module comprises a transparent protective material between the optical device and the coupler.

In one embodiment, the leads are configured for surface mounting of the module. In one embodiment, the leads are configured for through-hole mounting.

In one embodiment, the substrate comprises a ceramics material. Preferably, the ceramics material comprises Al₂O₃ or AlN.

In one embodiment, the substrate has vertical conductive interconnects between the opposed surfaces.

In one embodiment, the substrate comprises a plurality of layers which are patterned with electrical tracks and conductive interconnects between the layers. In one embodiment, the substrate comprises a patterned non-conductive layer deposed over conductive tracks and being in contact with the leads.

In one embodiment, the leads are derived from a metal lead frame. In on embodiment, the leads comprise a flexible printed circuit.

In one embodiment, the module is at least partly wrapped in a metal shield surrounding at least part of the moulding. In one embodiment, the module is at least partly covered by a conductive plastics shield surrounding at least part of the moulding.

In one embodiment, the module comprises two or more openings, each having an associated optical device and coupler.

In one embodiment, the moulding includes a body between said openings, said body encapsulating the integrated circuit.

In one embodiment, the integrated circuit is linked with all of the optical devices. In one embodiment, at least one optical device is an optical transmitter and at least one other device is an optical detector.

In one embodiment, the substrate has an opening which is accessible via the moulding opening and the optical device is mounted one a side of the substrate opposed to the moulding opening, and there is a light path between the coupler and the optical device via said opening.

In one embodiment, the substrate includes alignment features engaging mating alignment features of the optical coupler. In one embodiment, the alignment features of the substrate are recesses and the optical coupler has protrusions that fit into the alignment recesses of the substrate. In one embodiment, the optical device is located in a recess in the substrate, said recess being on a side opposed to the coupler. In one embodiment, a lead is mounted over the recess in the substrate and the optical device such that the device is enclosed.

In one embodiment, the substrate has at least one through hole electrical via connected to ground in between the optical device and the integrated circuit. - A -

In one embodiment, there are a plurality of through hole electrical vias arranged to surround the optical device to form an enclosed metal cage.

In one embodiment, the substrate is made from two or more laminated layers with interconnects between the layers.

In one embodiment, alignment features for the optical coupler are located on one layer of the substrate; and a recess for the optical device is located on the other substrate layer.

In one embodiment, a part of the moulding and leads form an electrical connector which is independent of optical coupling of the module.

In one embodiment, there is a recess in the moulding portion that acts as a well for adhesive for attaching the optical coupler in the moulding opening.

In another aspect, the invention provides a method of manufacturing an optical device module comprising: leads arranged for connection of the module to an external circuit; a substrate patterned with electrical tracks on at least opposed surfaces and being secured to the leads; at least one signal processing integrated circuit with an optical device driver or amplifier function on the substrate and being electrically connected to at least some of the substrate tracks; a moulding around the substrate leaving at least one opening each exposing part of the substrate, the moulding encapsulating the integrated circuit, at least one optical device mounted on the substrate within the moulding opening or openings, each said optical device being an optical emitter, detector, or transceiver; and an optical coupler mounted in each moulding opening and each in alignment with an optical device; the method comprising the steps of: providing a lead frame incorporating said leads; placing the substrate on the lead frame in which tracks of the substrate are connected to at least some of the leads; placing the signal processing integrated circuit and any other desired components on the substrate; over-moulding the substrate to encapsulate the integrated circuit, while leaving a moulding opening which exposes some of the substrate; placing a coupler in the moulding opening in alignment with the optical device; cropping the lead frame to provide the module leads; and manipulating the leads for a desired mounting configuration.

In one embodiment, the leads are manipulated for surface mounting. In one embodiment, the leads are manipulated to wrap around the moulding. In one embodiment, the leads are manipulated for through-hole mounting

In one embodiment, the method comprises providing a through hole in the substrate, placing the optical device on the substrate in alignment with the through hole, and moulding so that the moulding opening is on the side opposed to the optical device.

DETAILED DESCRIPTION OF THE INVENTION

Brief Description of the Drawings

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:-

Fig. 1 is a diagram showing first stages of manufacture of an optical semiconductor module, in which a patterned ceramics submount or substrate is deposited on a lead frame, and an integrated circuit (IC) is mounted on the substrate, and Fig. 2 shows a view from underneath;

Fig. 3 shows manufacture after moulding of a non-transparent package around the substrate on both sides of the lead frame, but leaving an opening over the substrate; Fig. 4 is a cross-sectional view after a fibre ferrule has been inserted into the opening, Fig. 5(a) is a perspective view of a completed module, and Fig. 5(b) is a flow diagram summarising the major steps in the manufacturing process;

Figs. 6 to 9 are perspective views of completed modules of various embodiments, illustrating versatility in the manner of configuring leads for mounting modules on devices, and outside protection;

Figs. 10, 11, and 12 are cross-sectional views of modules of alternative embodiments, showing versatility achieved by the manufacturing process;

Fig. 13 shows how a number of modules, in this case four, may be manufactured using a single lead frame;

Figs. 14 and 15 are perspective views showing an alternative way of providing leads;

Fig. 16 is a diagram showing a cross section of a further module according to the invention;

Figs. 17 (a), (b), and (c) are diagrams showing cross sections of a module according to the invention at various stages of assembly, and Fig. 17(d) is a flow diagram;

Fig. 18 is a diagram showing a cross section of an optical transceiver module according to the invention, and Figs. 19(a) and (b) are top and underneath perspective views showing an alternative module;

Fig. 20 shows a stage of manufacture of a module having an optical transceiver in combination with an electrical connector, and Figs 21 (a) and 21(b) are front and rear perspective views of the completed module;

Fig. 22 is a pair of sets of views showing optical couplers for use in the manufacturing process; and Fig. 23 is a diagram showing a cross section of an alternative optical device module according to the invention.

Description of the Invention

Referring to Figs. 1 to 5 a low-profile optical semiconductor module is manufactured. The module is for mounting on or at the edge of a circuit board of a user hand-held device such as an MPEG music player. A lead frame 1 is provided onto which a ceramics submount or substrate 2 is attached. The ceramics substrate 2 has the advantages of (i) good thermal properties, (ii) high flexural strength (iii) excellent electrical properties (iv) the ability to form conductive tracks with fine resolution that can be routed within and through the ceramics body, and (v) ICs may be flip- chipped onto the ceramic, avoiding need for wire bonding which in turn leads to a reduction in the physical dimensions of the package. As shown in Fig. 2, the side of the ceramics substrate 2 contacting the lead frame has a non-conductive layer 4 and bond pads 5. The substrate 2 can thus be connected to the lead frame 1 in a versatile manner, with electrical contact only where desired. The ceramic also has excellent electrical properties that allows transmission of high speed (>5GHz) electrical interconnects along the ceramic The substrate 2 provides substantial electrical interconnection density for the module without being limited by the configuration of the lead frame. During machine handling, the lead frame 1 is gripped, allowing convenient manipulation for downstream processing and avoidance of contact with the substrate and its intricate tracks.

An optical device driver IC 3 is placed onto the ceramic substrate 2 on the side facing away from the lead frame 1. Hence, the interconnections between this top surface and the surface contacting the lead frame 1 provide the desired connectivity between the IC 3 and the lead frame 1 and on to the user device to which the module will be connected. The IC 3 has any of the desired driver and amplifier circuits for interfacing between the electrical and optical domains.

As shown in Figs. 3 and 4, a non-transparent plastics resin 7 is over-moulded, surrounding the substrate 2 on all sides, and leaving an aperture 8 exposing a metallised pad on the substrate 2 for an optical device. The IC 3 is completely encapsulated by the moulding 7. A semiconductor optical device 9 is placed through the aperture 8 onto the substrate 2 at this location, and wire bonds 10 are made. When the optical element 9 is in place on the substrate 2 in the opening 8, any of a variety of optical connectors or elements may be inserted in the opening 8 to achieve the desired connectivity. In the embodiment of Fig. 4 a lensed fibre ferrule 11 with a fibre termination 12 is located in the aperture 8. Fig. 4 also shows flip chip solder bonds 13 of the IC 3. The placement of the optical element 9 can be positioned within the opening 8 to sufficient precision to provide a desired accuracy of alignment between the coupler 11 and the optical element 9.

The excess lead frame 1 is cropped - leaving only desired legs extending from the substrate 2. The legs of the lead frame may be oriented in any desired manner to suit the required mounting arrangement. The arrangement of Fig. 5(a) shows a module 20 which is suitable for a "sidelooker" surface mount lead pin arrangement, in which the ferrule 11 is aligned parallel to the board onto which the module 20 is placed and the leads 15 are bent through a right angle.

The above manufacturing steps are summarised in Fig. 5(b).

In a module 25 shown in Fig. 6, an arrangement of leads 26 allows surface mounting in which the ferrule 11 is aligned normal to the board onto which the module 25 is placed.

Fig. 7 shows a module 30, in which leads 31 are wrapped around the moulding 7 in another surface mount configuration.

Fig. 8 shows a module 40 suitable for use in free space applications with a lens and window holder 41 supported on a casing, and surface-mount lead frame legs 42. There is a metal shield 43 and whose formed leads are in line with the formed leads 42 of the module 40.

As shown in Fig. 9, in a module 60 a metal shield 61 is wrapped around the module to provide protection from electromagnetic interference and to prevent the emission of electromagnetic noise from the module. The metal shield 61 also provides additional mechanical stability to the module after attachment to the board. The module 60 also has leads 62 bent at right angles and cropped short, a fibre socket 63 is inserted into the aperture, and a fibre F is connected into the socket.

There is excellent versatility in the manner of coupling the optical device with a fibre. As noted above, Fig. 4 shows a fibre ferrule 11 with moulded lens 14 in the opening 8, giving optical access to the optical element 9. Such a fibre ferrule may be made with a transparent plastics material capable of sustaining the temperatures of a solder reflow oven such as the plastics Extern™ or Ultem™.

Fig. 10 shows a module 70 having a glass ball lens 30 supported in a fibre ferrule 72 which is made from a non-transparent filled plastics body with high-temperature properties. A fibre termination 73 is retained in the socket formed by the ferrule 72. The ferrule 72 is attached to the opening in the over-mould 7.

Fig. 11 shows a module 80 having an over-mould 7 supporting a lens element 81 above the optical element 9 such that an optical beam B is either generated or collected. This allows the module 80 to be used in free space applications.

Referring to Fig. 12 a module 90 has a patterned substrate 91, moulded side walls 92, leads 93 from a lead frame, a driver IC 94 connected by flip chip bonds 95 to the substrate 91, a semiconductor optical emitter 96 with wire bonds 97, and a lens 98 in an opening over the emitter 96. There is also a lens 99 in a second opening formed between an over-moulding 100 and the walls 92, and a semiconductor optical receiver 101 in the second opening. This embodiment shows that there may conveniently be two or more optical devices (96 and 101) on a ceramics substrate (91). The over-moulding provides two apertures exposing two surfaces of the substrate 91. A single IC (94) provides all of the connectivity required for both of the optical devices 96 and 101. Again, there is excellent protection of the IC 3 due to the over-moulding, this single step also providing the opening for the optical elements and alignment of their associated couplers.

It will be appreciated that the invention allows a huge variety in terms of how the module is mounted on a board and in terms of free-space coupling or with a fibre termination. The height of the module may in one embodiment be dictated by the width of the substrate, as it can be turned through 90° for mounting. The use of a ceramics substrate allows for conductor tracks to be incorporated on and in the one substrate, with the advantage of vertical interconnects, either vias or edge connects. The resin used for the over-mould can have a high fill-factor and hence be thermally conductive with a low expansion coefficient and hence compatible with standard solder reflow processes. Referring to Fig. 13 a lead frame 120 is used to produce four modules, two being shown. A ceramics substrate 121 is placed at each of four sets of lead frame legs, and a driver IC 122 is placed on the substrate 121. It will be appreciated that a multiplicity of assemblies may be implemented on a lead frame to provide for an efficient high-volume manufacturing process. This drawing also shows, for one of the modules, an over-moulding 123 with an opening 124.

Figs. 1 and 2 illustrate the extent of interconnect allowed on the substrate 2. In another embodiment, a vertical cavity surface emitting laser (VCSEL) or similar optical device is placed in the moulding opening and wire bonded to the pad on the substrate. For certain varieties of optical devices the use of ball bonding may be entirely avoided if the optical device has also been specifically designed for a flip-chip bonding process. As illustrated in the various embodiments above, a ball lens fibre ferrule may be attached over the VCSEL element, and a metal shield may be wrapped around the plastics to provide protection from electromagnetic interference and to prevent the emission of electromagnetic noise from the module. The metal shield may also provide additional mechanical stability to the module after attachment to the board.

It is not essential that an all-metal lead frame as shown is used. A flexible frame such as the flex printed circuit board frame 150 shown in Fig. 14 could be used instead, and Fig. 15 shows completed assemblies built on the flexible frame. A flexible circuit is an arrangement of printed wiring, normally copper, laminated between 2 sheets of flexible heat resistant polymer, an example of which is Duponts Pryalux™. Fig. 14 (a-d) shows the module at various stages of construction. Fig. 4(a) shows a flexible circuit 150 which has holes in the upper polymer laminate 151 through which an electrical contact can be made to the underlying metal circuit tracks. Fig. 4(b) shows the assembled ceramic 151 electrically attached to the metal tracks of the flexible circuit. As shown in Fig 14(c), a non transparent plastics resin 154 is over-moulded surrounding the substrate on all sides and a portion of the flexible circuit attached to the ceramic, and leaving an aperture 155 exposing a metallised pad on the substrate. As shown in Fig. 4(d) an optical device 156 is mounted on the substrate through the aperture 157. As shown in Fig 15 an optical coupler is attached to the aperture of the over-mould and the flexible circuit can be bent through 90 degrees so that the module is seated in the correct orientation.

It is commonly known that it is not possible to over-mould onto a ceramics substrate using conventional moulding techniques. The ceramics material is brittle and normally slightly warped due to the firing process at the manufacturing stage. If a ceramics plate were to be placed between the two opposing plates of the molding tool and the plates were to clamp down on the brittle substrate it would cause it to fracture and break due to the high clamping pressures. However, a major advantage of the ceramics substrate being mounted on a lead frame is that the part is held in place in the centre of the mould and the moulding plates can clamp down on the flexible lead frame.

The non-transparent molding resin may advantageously have a filler content of at least 70 wt % or more so that it has a low thermal expansion coefficient, similar to that of the lead frame and also a high thermal conductivity that extracts heat out of the package.

The lead frame, optical module, IC driver/amplifier and any electrical components such as resistors or capacitors may be attached to the ceramics substrate using gold/tin eutectic, or a conductive silver epoxy paste, solder paste, or gold bump.

The IC driver/amplifier may be under-filled prior to moulding using an under-iϊll adhesive such as Henkel Ablestik UF8828 to ensure that voids in the over- mould do not occur under the IC and also to provide good mechanical stability of the IC to the ceramic.

The optical element and the wire bond may be encapsulated with a transparent resin which could be either an optical epoxy or a silicon elastomer or silicon epoxy to ensure that the component can operate in harsh high temperature and humidity environments.

The ceramics substrate may have patterned conductive tracks on both top and bottom surfaces, which are interconnected through vertical interconnects in the ceramic layers either through vias or edge connectors. The ceramics substrate may also be made of multiple layers of conductive patterned ceramic that are sandwiched together during the firing process and each layer may be interconnected through vertical interconnects in the layers either through vias or edge connectors.

The ceramics substrate can be made in production volumes using established technologies such as a low temperature co-fired ceramic (LTCC) method or a high temperature co-fired ceramic (HTCC) method. Typical HTCC materials are 90% to 99.6% Alumina (A12O3) and AlN or typical LTCC materials such as Kyocera's GL330. There may be a patterned non-conductive layer on the bottom of the substrate to prevent shorting of the conductive tracks and these can be a spin-on polymer resin that is capable of withstanding high temperatures such as benzocyclobutene (BCB) or polyamide.

The lead frame thickness is advantageously between 100 μm and 500 μm and is preferably made from a metal that has high electrical and thermal conductivity, such as copper or an iron/nickel alloy. The lead frame may be plated with silver, gold or palladium.

Fig. 16 is a cross-sectional view showing an optical device module according to another embodiment and Figs. 17(a), (b), and (c) are cross-sectional views of an optical device module showing the various stages of manufacture. The optical module is for mounting on or at the edge of a circuit board of a user hand-held device.

As shown in Fig. 16 a signal processing IC 204 is mounted and electrically connected by metal contacts 211 to tracks on a patterned substrate 201. A semiconductor optical device 202 is mounted and electrically connected by metal contacts 225 to a surface in a recess in the substrate 208 such that an optical surface 203 of the semiconductor optical device 202 is aligned to a through hole 206 formed in the ceramics substrate 201. A lead frame 205 is provided onto which the ceramics substrate 201 is electrically and mechanically attached. A non-transparent plastics resin 210 encapsulates the assembled substrate 201, leaving an aperture exposing the through hole 206. An optical coupler 207 is located in the aperture of the plastics resin and is aligned to the through hole 206 of the substrate by recesses 212 in the substrate which align to ridges in the optical coupler 213.

Fig. 17(a) shows a cross section view of the substrate 201 at the stage in manufacture after the components, signal processing IC 204 and optical semiconductor 202, have been mounted onto the ceramics substrate 201 and before the assembled substrate is attached to the lead frame 205. The substrate 201 is made of multiple layers 232, 233 and this method of manufacture is commonly known to those involved in the process of manufacturing ceramics. The two ceramics layers 232, 233 are both patterned with metalised circuit patterns on either or both surfaces and are punched to form holes through each layer. The layers are then aligned to each other and laminated under heat and pressure to form a single monolithic structure. This method of manufacture produces patterned metal circuits on both top and bottom surfaces of the ceramics substrate and also patterned metal circuits that are buried in the middle of the substrate. Through holes or vias 206 are formed when the holes from each layer are overlayed during the laminating process. Metallised vias 209 that interconnect the metallised circuit patterns are formed when through holes filled with metal are overlayed and blind vias 208, 212 or recesses in the substrate can also be formed when there is a through hole on only one layer. Fig 17(a) shows the assembly of the semiconductor optical device 202 and the signal processing IC 204 onto the ceramic substrate 201. The bond pads of the signal processing IC 204 are electrically connected to tracks on the top surface of the substrate 201 by a metal bond 211. This metal bond may be formed by a method known as flip chip solder bonding. The semiconductor optical device 202 is attached to the surface of the first substrate 232 inside a recess 208 in the second substrate layer 233. The bond pads of the semiconductor optical device 202 are electrically connected to a patterned metal circuit of the first substrate layer 232 via metal bonds 225. These patterned metal tracks are aligned to the via 206 in the first substrate layer 232.

Fig 17(b) shows a cross sectional view of the substrate 201 at the stage in manufacture after the assembled substrate has been attached to the lead frame 205 and before over-moulding in non- transparent plastics. This drawing shows how a wide lead 226 of the lead frame covers over the lower recess 208, thus forming an enclosure for the device 202. A combination of the filled vias 209, the pads 225, and the lead 226 together form the metallised cage.

Fig. 17(c) shows a cross section of the over-moulded assembled ceramics substrate. The non- transparent plastics resin encapsulates the substrate 201 but leaves an aperture in the plastics 228 over the through hole 206 and the two recesses 212 in substrate. After over-molding the optical coupler 207 is inserted into the aperture 228. The optical coupler 207 is located into the aperture of the plastics so that the alignment notches 213 of the optical coupler are seated into the corresponding recesses 212 in the ceramics substrate. The optical coupler 207 is attached to the plastics over-mould housing with a material such as epoxy resin at the attachment points 229. A recess 237, 238 in the over-mould acts as a well for adhesive so that the adhesive securely attaches the optical coupler at the corresponding points 228 and 229.

The above manufacturing steps are summarised in Fig. 17(d).

Referring again to Fig. 16 the alignment of the optical coupler 207 to the semiconductor optical surface 203 is important for attaining high transmission efficiency and high reception efficiency. The optical coupler 207 is aligned to the substrate by the two recesses 212, which control the alignment of the optical coupler 207 in respect to the substrate in both the X and Y directions and the Z direction. The bond pads of the semiconductor optical device 202 are aligned in the X and Y directions with respect to the metal circuit on the substrate on the plane 215. The optical device alignment to the metal circuit in the X and Y directions can be controlled by either accurate machine placement or a self-alignment flip chip process during the metal attach. The distance in the Z direction of the semiconductor optical surface 203 from the plane 215 can be controlled by the thickness of the metal contact 225. The alignment of the metal circuit to the recess on the opposite surface of the substrate is controlled during the substrate manufacturing process.

Fig. 18 is a cross-sectional view showing an optical module 250 according to another embodiment. The module 250 comprises a ceramics substrate 251 on a lead frame 252 which is considerably wider than those of the above embodiments. Figs. 19(a) and 19(b) show a ceramics substrate assembly before over-moulding.

Optical elements 253 and 254 are mounted in a manner similar to that described above with reference to Figs. 16 and 17. The elements 253 and 254 are in recesses 255 and 256 respectively, which are both covered at the bottom by a wide lead frame element 257. The substrate 251 includes a metal barrier 258, and the over-mould includes an optical barrier 259. There is an optical coupler 260 over a recess 261 in the substrate 251, and an optical coupler 262 over a recess 263 in the substrate 251. The coupler 262 has an alignment ridge 268 engaging a recess in the substrate 251 , and the coupler 260 has a similar alignment arrangement. In this embodiment there are ICs 265 and 266 having bonds 267.

This module is different from that illustrated in Fig. 16 in the point that a semiconductor optical emitter 254, a driver IC 266, a photodiode 253, a receiver IC 265, a receiver lens 260 and a transmitter lens 262 are incorporated in a single package. Hence, the module is a transceiver in one package.

The module 250 uses a non-transparent moulding portion 259 to obstruct any light coupling between the receiver lens 260 and transmitter lens 262. It is also understood that when a receiver and transmitter are incorporated in a single package electrical noise from the semiconductor optical emitter can be picked up by the photo diode and the receiver. The module 250 has the grounded metal vias 258 located between the photo diode 253 and the optical emitter 254. The photodiode recess 255 and the optical emitter recess 256 are enclosed by the grounded lead frame 257. The metal vias 258 and the grounded lead frame 257 combine to form an integrated metal shield around the photodiode and optical emitter that would potentially eliminate the need for a metal shield to be formed between the transmitter receiver parts which would simplify the manufacture and allow a smaller transceiver form factor and one in which the receiver and transmitter can be positioned closer together without a degradation of receiver data signal.

Figs. 19(a) and 19(b) show also surface mount capacitors 270 at each end of the substrate. The substrate 251 is in two parts 251 (a) and 251 (b), much as for the embodiment of Figs. 16 and 17. Fig. 19(b) shows the substrate's pads 271 for connection to the lead frame 252.

Fig. 20 shows an arrangement of an assembled substrate 280 secured to a lead frame 281 before over-moulding. The lead frame 281 includes leads as follows: 282 for receiver signals, 284 for transmitter signals, 283 for ground signals, and also leads 285 for electrical signals. As shown in Figs. 21 (a) and 21(b) after over-moulding and electrical shielding on the outside, the module 290 has an optical connector 291 and a two-part electrical connector 292(a) and 292(b). The module 290 shown in Figs. 21(a) and 21 (b) is different from that in the embodiment of Fig. 18 in the point that the optical transceiver module is integrated into an electrical connector so that the complete connector has the ability to receive and send both optical signals and electrical signals.

An advantage of this connector is in the simplicity of manufacture, in which the lead frame which is used in the assembly of the optical transceiver is also used to form an electrical socket for transmission of electrical signals.

The assembled ceramics substrate 280 is attached onto the lead frame281 prior to over-molding. After attachment to the lead-frame the whole assembly can be over-molded in one step and an integrated optical and electrical connector formed. Fig. 21 (a) shows the two optical windows for receiving and transmitting optical signals and also shows the electrical socket for receiving and sending electrical signals. Fig. 22 shows the receiving and transmitting couplers 261 and 262 in more detail. These are suitable for the embodiments of Figs. 18 to 21.

Fig. 23 shows a module 310 in which an optical element 314 is mounted not in a recess but directly onto the ceramic substrate 311 such that an optical surface 316 of the semiconductor optical device 314 is aligned to a through hole 313 formed in the ceramics substrate 311. The module 310 has a substrate 311, a lead frame 312, an aperture 313 in the substrate, and alignment protrusions 315 in a coupler 320. The substrate 311 forms side walls 315 in the sides of the aperture 313.

The ceramics substrate can be made in production volumes using established technologies such as a low temperature co-fired ceramic (LTCC) method or a high temperature co-fired ceramic (HTCC) method.

The ceramics substrate also has the advantages (i) ceramic has good thermal properties, (ii) the conductive tracks have fine resolution and can be routed within the body of the ceramic (iii) metal vias can be formed that allow electrical connection between top and bottom electrical tracks (iv) the surface of the ceramic is flat enough that ICs and optical devices may be flip- chipped onto the ceramic which avoids the need for wire bonding which in turn leads to a reduction in the physical dimensions of the package and (v) through holes and recesses can be formed in the ceramic.

Machine handling however is of the lead frame, allowing convenient manipulation for downstream processing.

The invention is not limited to the embodiments described but may be varied in construction and detail.

Claims

1. An optical device module comprising: leads arranged for connection of the module to an external circuit; a substrate patterned with electrical tracks on at least opposed surfaces and being secured to the leads; at least one signal processing integrated circuit with an optical device driver or amplifier function on the substrate and being electrically connected to at least some of the substrate tracks; a moulding around the substrate leaving at least one opening each opening exposing part of the substrate, the moulding encapsulating the integrated circuit, at least one optical device mounted on the substrate within the moulding opening or openings, each said optical device being an optical emitter, detector, or transceiver; and an optical coupler mounted in each moulding opening and each in alignment with an optical device.

2. An optical device module as claimed in claim 1, wherein the moulding includes non- transparent moulding resin material.

3. An optical device module as claimed in either of claims 1 or 2, wherein the coupler comprises a lens.

4. An optical device module as claimed in claim 3, wherein the coupler comprises a lens of transparent resin.

5. An optical device module as claimed in claim 3, wherein the coupler comprises a lens of glass.

6. An optical device module as claimed in any of claims 1 to 5, wherein the coupler includes a light concentrator.

7. An optical device module as claimed in any preceding claim, wherein the coupler comprises a fibre-retaining socket.

8. An optical device module as claimed in claim 7, wherein the fibre-retaining socket comprises an integrated lens of transparent resin.

9. An optical device module as claimed in any preceding claim, comprising a transparent protective material between the optical device and the coupler.

10. An optical device module as claimed in any preceding claim, wherein the leads are configured for surface mounting of the module.

11. An optical device module as claimed in any of claims 1 to 9, wherein the leads are configured for through-hole mounting.

12. An optical device module as claimed in any preceding claim, wherein the substrate comprises a ceramics material.

13. An optical device module as claimed in claim 12, wherein the ceramics material comprises Al₂O₃ or AlN.

14. An optical device module as claimed in any preceding claim, wherein the substrate has vertical conductive interconnects between the opposed surfaces.

15. An optical device module as claimed in any preceding claim, wherein the substrate comprises a plurality of layers which are patterned with electrical tracks and conductive interconnects between the layers.

16. An optical device module as claimed in any preceding claim, wherein the substrate comprises a patterned non-conductive layer deposed over conductive tracks and being in contact with the leads.

17. An optical device module as claimed in any preceding claim, wherein the leads are derived from a metal lead frame.

18. An optical device module as claimed in any preceding claim, wherein the leads comprise a flexible printed circuit.

19. An optical device module as claimed in any preceding claim, wherein the module is at least partly wrapped in a metal shield surrounding at least part of the moulding.

20. An optical device module as claimed in any preceding claim, wherein the module is at least partly covered by a conductive plastics shield surrounding at least part of the moulding.

21. An optical device module as claimed in any preceding claim, wherein the module comprises two or more openings, each having an associated optical device and coupler.

22. An optical device module as claimed in claim 21, wherein the moulding includes a body between said openings, said body encapsulating the integrated circuit.

23. An optical device module as claimed in claim 22, wherein the integrated circuit is linked with all of the optical devices.

24. An optical device module as claimed in any of claims 21 to 23, wherein at least one optical device is an optical transmitter and at least one other device is an optical detector.

25. An optical device module as claimed in any preceding claim, wherein the substrate has an opening which is accessible via the moulding opening and the optical device is mounted on a side of the substrate opposed to the moulding opening, and there is a light path between the coupler and the optical device via said opening.

26. An optical device module as claimed in any preceding claim, wherein the substrate includes alignment features engaging mating alignment features of the optical coupler.

27. An optical device module as claimed in claim 26, wherein the alignment features of the substrate are recesses and the optical coupler has protrusions that fit into the alignment recesses of the substrate.

28. An optical device module as claimed in any of claims 25 to 27 wherein the optical device is located in a recess in the substrate, said recess being on a side opposed to the coupler.

29. An optical device module as claimed in claim 28, wherein a lead is mounted over the recess in the substrate and the optical device such that the device is enclosed.

30. An optical device module as claimed in any preceding claim, wherein the substrate has at least one through hole electrical via connected to ground in between the optical device and the integrated circuit.

31. An optical device module as claimed in claim 30, wherein there are a plurality of through hole electrical vias arranged to surround the optical device to form an enclosed metal cage.

32. An optical device module as claimed in any preceding claim, wherein the substrate is made from two or more laminated layers with interconnects between the layers.

33. An optical device module as claimed in claim 32, wherein alignment features for the optical coupler are located on one layer of the substrate; and a recess for the optical device is located on the other substrate layer.

34. An optical device module as claimed in any of claims 25 to 33, wherein a part of the moulding and leads form an electrical connector which is independent of optical coupling of the module.

35. An optical device module as claimed in any preceding claim, wherein there is a recess in the moulding portion that acts as a well for adhesive for attaching the optical coupler in the moulding opening.

36. A method of manufacturing an optical device module comprising: leads arranged for connection of the module to an external circuit; a substrate patterned with electrical tracks on at least opposed surfaces and being secured to the leads; at least one signal processing integrated circuit with an optical device driver or amplifier function on the substrate and being electrically connected to at least some of the substrate tracks; a moulding around the substrate leaving at least one opening each exposing part of the substrate, the moulding encapsulating the integrated circuit, at least one optical device mounted on the substrate within the moulding opening or openings, each said optical device being an optical emitter, detector, or transceiver; and an optical coupler mounted in each moulding opening and each in alignment with an optical device; the method comprising the steps of: providing a lead frame incorporating said leads; placing the substrate on the lead frame in which tracks of the substrate are connected to at least some of the leads; placing the signal processing integrated circuit and any other desired components on the substrate; over-moulding the substrate to encapsulate the integrated circuit, while leaving a moulding opening which exposes some of the substrate; placing a coupler in the moulding opening in alignment with the optical device; cropping the lead frame to provide the module leads; and manipulating the leads for a desired mounting configuration.

37. A method as claimed in claim 36, wherein the leads are manipulated for surface mounting.

38. A method as claimed in claims 36 or 37, wherein the leads are manipulated to wrap around the moulding.

39. A method as claimed in claims 36 or 37, wherein the leads are manipulated for through- hole mounting

40. A method as claimed in any of claims 36 to 39 comprising providing a through hole in the substrate, placing the optical device on the substrate in alignment with the through hole, and moulding so that the moulding opening is on the side opposed to the optical device.