Ceramic optical sub-assembly for opto-electronic module utilizing LTCC ( low-temperature co-fired ceramic ) technology

• US 20030165303A1
• Filed: 03/03/2003
• Published: 09/04/2003
• Est. Priority Date: 05/09/2000
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Liu, Jia, Pendse, Neeraj Anil, Roberts, Bruce Carlton, Auzereau, Lionel, Barratt, Christopher
• Granted Patent: US 6,767,140 B2
• Time in Patent Office: Days
• US Class Current: 385/89
• CPC Class Codes: G02B 6/4201 Packages, e.g. shape, construction, internal or external details
• CPC Class Codes: G02B 6/4272 with mounting substrates of high thermal conductivity
• CPC Class Codes: G02B 6/4277 Protection against electromagnetic interference [EMI], e.g. shielding means shielding of electric apparatus H05K9/00, of instruments G12B17/00
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/05024 the internal layer being disposed on a redistribution layer on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/05099 Material
• CPC Class Codes: H01L 2224/05548 Bonding area integrally formed with a redistribution layer on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/16145 the bodies being stacked
• CPC Class Codes: H01L 2224/45014 Ribbon connectors, e.g. rectangular cross-section
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48235 connecting the wire to a via metallisation of the item
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 23/49838 Geometry or layout
• CPC Class Codes: H01L 24/16 of an individual bump connector
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 25/167 : comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00011 : Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 : Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01042 : Molybdenum [Mo]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/3011 : Impedance
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding
• CPC Class Codes: H05K 1/0219 : Printed shielding conductors for shielding around or between signal conductors, e.g. coplanar or coaxial printed shielding conductors
• CPC Class Codes: H05K 1/0274 : Optical details, e.g. printed circuits comprising integral optical means H05K1/0269 takes precedence; coupling light guides with opto-electronic components G02B6/42
• CPC Class Codes: H05K 1/189 : characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/0715 : provided by an outer layer of PCB
• CPC Class Codes: H05K 2201/09236 : Parallel layout layout of balanced signal pairs H05K1/0245; superposed layout H05K2201/09672
• CPC Class Codes: H05K 2201/10121 : Optical component, e.g. opto-electronic component
• CPC Class Codes: H05K 3/366 : substantially perpendicularly to each other H05K3/361 takes precedence
• CPC Class Codes: H05K 3/403 : Edge contacts; Windows or holes in the substrate having plural connections on the walls thereof H05K3/4092 takes precedence

Abstract

A high performance ceramic block for use with small-scale circuitry is described. The block can be used in an optical sub-assembly (OSA) suitable for optical interconnection with optical fibers and electrical interconnection with a chip sub-assembly (CSA) is formed. The block includes a first surface and a second surface and is formed using one of low temperature co-fired ceramic (LTCC) and high temperature co-fired ceramic (HTCC) techniques. Photonic devices are formed on the first surface of the ceramic block and electrical contacts are formed on a second surface of the block. The electrical contacts being suitable for electrical communication with a chip sub-assembly. Electrical connections are formed so that they pass internally through the ceramic block to electrically interconnect the photonic devices on the first face of the block with the electrical contacts on the second face of the block. Such a block can be advantageously used to form an optoelectronic module.

Claims

1. An optical sub-assembly (OSA) suitable for optical interconnection with optical fibers and electrical interconnection with a chip sub-assembly (CSA), the OSA comprising;

a ceramic block having a first face and a second face, the ceramic block being formed using one of low temperature co-fired ceramic (LTCC) and high temperature co-fired ceramic (HTCC);

at least one photonic device formed on a first face of the ceramic block;

at least one signal connection that passes through internal portions of the ceramic block, each signal connection being suitable for electrically connecting a photonic device to a chip sub-assembly (CSA);

at least one ground; and

at least one ground connection that passes through internal portions of the LTCC block and electrically connects a photonic device to an associated ground of the at least one ground.

2. The optical sub-assembly (OSA) of claim 1 wherein the at least one ground is electrically connected to the chip sub-assembly.

3. The optical sub-assembly (OSA) of claim 2 wherein the at least one ground passes through internal portions of the ceramic block.

4. The optical sub-assembly (OSA) of claim 3 wherein the at least one photonic device comprises a plurality of photonic devices;

wherein the at least one ground includes a plurality of grounds; and

wherein the at least one ground connection that passes through internal portions of the ceramic block comprises a plurality of ground connections configured so that each ground connection electrically connects a photonic device to an associated ground.

5. The optical sub-assembly (OSA) of claim 4 wherein each ground of the plurality of grounds is shielded from other grounds by a metal shield layer.

6. The optical sub-assembly (OSA) of claim 1 wherein the at least one ground comprises a single ground plane.

7. The optical sub-assembly (OSA) of claim 6 wherein the at least one ground comprises two ground planes.

8. The optical sub-assembly (OSA) of claim 7 wherein the two ground planes are shielded from each other by a shield plane.

9. The optical sub-assembly (OSA) of claim 1 wherein the at least one photonic device comprises a plurality of photonic devices;

wherein a plurality of bonding pads are formed on the first face of the ceramic block;

wherein a first end of each signal connection is electrically connected to one of the plurality of bonding pads and wherein each bonding pad is wire bonded to an associated one of the plurality of photonic devices thereby establishing electrical connections to the photonic devices;

wherein a plurality of contact pads are formed on a second face of the ceramic block; and

wherein a second end of each signal connection is electrically connected to one of the plurality of contact pads, such signal connection passing internally through the ceramic block, thereby establishing electrical connection between photonic devices and the plurality of contact pads.

10. The optical sub-assembly (OSA) of claim 9 wherein the plurality of bonding pads are formed in two groups, a first set of bond pads being formed on one side of the photonic devices and a second set of bond pads being formed on an opposite side of the photonic devices, the sets of bond pads are arranged such that the bond pads of the first set are staggered with respect to the bond pads of the second set and such that the wire bonds to each bond are correspondingly staggered.

11. The optical sub-assembly (OSA) of claim 9 further comprising:

a semiconductor chip sub-assembly (CSA) having a top surface that has exposed up-linking contacts; and

wherein the OSA including the ceramic block is placed onto the top surface of the CSA such that the contact pads are placed in electrical communication with the up-linking contacts of the CSA and such that the at least one ground is placed in electrical communication with the up-linking contacts of the CSA.

12. The CSA of claim 11 wherein the CSA is a leadless leadframe package.

13. An optoelectronic module comprising:

a ceramic block having a front surface and a bottom surface, the ceramic block being formed using one of low temperature co-fired ceramic (LTCC) and high temperature co-fired ceramic (HTCC), the ceramic block including,

a device attachment area formed on the front surface;

photonic devices formed on the device attachment area;

solder pads formed on the bottom surface of the ceramic block;

electrical contact lines that pass internally through the ceramic block,

the electrical contact lines including,

contact pads formed on the front surface of the ceramic block;

signal connections that pass through internal portions of the ceramic block to electrically connect the contact pads to associated solder pads;

wire bonds for electrically connecting the contact pads with the photonic devices;

grounds that are electrically connected to selected solder pads;

ground connections that pass through internal portions of the ceramic block to electrically connect the device attachment area to the grounds; and

a semiconductor chip sub assembly (CSA) having a top surface that has exposed up-linking contacts, wherein the ceramic block is placed onto the top surface of the CSA such that the solder pads formed on the bottom surface of the ceramic block are placed in electrical communication with the up-linking contacts of the CSA.

14. An optoelectronic module as recited in claim 13 wherein the module comprises an optical transceiver wherein the photonic devices comprise an optical transmitter and an optical receiver.

15. An optoelectronic module as recited in claim 13 wherein the module includes twelve photonic devices.

16. An optoelectronic module as recited in claim 13 wherein the contact pads formed on the front surface of the ceramic block are formed in two sets of contact pads so that a first set of contact pads is formed on a first side of the photonic devices and a second set of contact pads is formed on a second side of the photonic devices.

17. An optoelectronic module as recited in claim 16 wherein the contact pads of the first set of contact pads are configured in a staggered arrangement with respect to the contact pads of the second set of contact pads.

18. An optoelectronic module as recited in claim 16 wherein the photonic devices formed on the device attachment area comprise n photonic devices, wherein n comprises an integer number of 2 or greater;

and

wherein the first set of contact pads comprises

$\frac{n}{2}$

 

contact pads and wherein the second set of contact pads comprises

$\frac{n}{2}$

 

contact pads.

19. An optoelectronic module as recited in claim 17 wherein the photonic devices formed on the device attachment area comprise n photonic devices, wherein n comprises an integer number of 2 or greater;

and

wherein the first set of contact pads comprises

$\frac{n}{2}$

 

contact pads and wherein the second set of contact pads comprises

$\frac{n}{2}$

 

contact pads.

20. An optoelectronic module as recited in claim 16 wherein the signal connections associated with the first set of contact pads are shielded from the signal connections associated with the second set of contact pads.

21. An optoelectronic module as recited in claim 13 wherein the distance between the bond pads is greater than the distance between the associated photonic devices.

22. An optoelectronic module comprising:

a ceramic block having a front surface and a bottom surface, the ceramic block including a plurality of ceramic layers, the block being formed using one of low temperature co-fired ceramic (LTCC) techniques and high temperature co-fired ceramic (HTCC) techniques, the block having;

the front surface having a device attachment area and contact pads formed thereon;

photonic devices formed on the device attachment area;

the bottom surface having solder pads formed thereon;

at least one internal electric contact plane having at least one electric contact line formed thereon such that the at least one electric contact line passes internally through the ceramic block, the at least one electric contact line being in electrical communication with the contact pads and associated solder pads;

wire bonds for electrically connecting the contact pads with the photonic devices;

at least one internal ground plane having at least one ground contact line formed thereon such that the at least one ground contact line passes internally through the ceramic block, the at least one ground contact line being in electrical communication with selected solder pads; and

a semiconductor chip sub assembly (CSA) having a top surface that has exposed up-linking contacts, wherein the ceramic block is placed onto the top surface of the CSA such that the solder pads formed on the bottom surface of the ceramic block are placed in electrical communication with the up-linking contacts of the CSA.

23. An optoelectronic module as in claim 22, wherein

the contact pads formed on the front surface of the ceramic block are formed in two sets of contact pads so that a first set of contact pads is formed on a first side of the photonic devices and a second set of contact pads is formed on a second side of the photonic devices;

wherein the at least one internal electric contact plane comprises two internal electric contact planes, a first internal electric contact plane and a second internal electric contact plane;

wherein the first set of contact pads is in electrical communication with the at least one electric contact line formed on the first internal electric contact plane and wherein the at least one electric contact line formed on the first internal electric contact plane is in electrical communication with associated solder pads; and

wherein the first internal electric contact plane and the second internal electric contact plane are shielded from each other.

24. An optoelectronic module as in claim 23, wherein the at least one internal ground plane includes a single ground plane having at least one ground contact line, the at least one ground contact line being in electrical communication with the die attachment pad and selected solder pads.

25. An optoelectronic module as in claim 24, wherein the single ground plane includes a single ground contact line being in electrical communication with the device attachment area and a selected solder pad.

26. An optoelectronic module as in claim 23, wherein the at least one internal ground plane includes a two ground planes, a first ground plane and a second ground plane, each having at least one ground contact line, the at least one ground contact line being in electrical communication with the device attachment area and selected solder pads.

27. An optoelectronic module as in claim 26, wherein the first ground plane is associated with the photonic devices electrically connected with the first set of contact pads and wherein the second ground plane is associated with the photonic devices electrically connected with the second set of contact pads.

28. An optoelectronic module as in claim 27, wherein the first ground plane is and the first set of contact pads are shielded from the second ground plane and the second set of contact pads.

29. An optoelectronic module as in claim 23, wherein the photonic devices are electrically connecting the contact pads using the bonding wires in an alternating configuration such that odd numbered photonic devices are electrically connected with the contact pads of the first set of contact pads and such that even numbered photonic devices are electrically connected with the contact pads of the second set of contact pads.

30. An optical sub-assembly (OSA) suitable for optical interconnection with optical fibers and electrical interconnection with a chip sub-assembly (CSA), the OSA comprising:

a ceramic block having a first surface and a second surface, the ceramic block being formed using one of low temperature co-fired ceramic (LTCC) and high temperature co-fired ceramic (HTCC);

at least one photonic device formed on the first surface of the ceramic block;

a plurality of electrical contacts suitable for electrical communication with a chip sub-assembly, the plurality of electrical contacts formed on the second surface of the ceramic block; and

a plurality of electrical connections that pass internally through the ceramic block so that the photonic devices on the first face of the block are electrically connected with the plurality of electrical contacts on the second face of the block.

31. The OSA of claim 30, wherein the plurality of electrical contacts include ground connections and signal connections configured such that each photonic device is electrically connected with at least one electrical connection and at least one ground connection.

32. The OSA of claim 30, wherein each electrical contact includes a contact pad formed on the first surface of the ceramic block, each contact pad being in electrical communication with an associated photonic device and wherein each electrical contact includes a solder pad formed on the second surface of the ceramic block, each solder pad being suitable for electrical connection with an associated up-linking contact on a chip sub-assembly.

33. The OSA of claim 32, wherein the at least one photonic device is electrically connected to the contact pads using a contact wire;

and

wherein the contact pads are configured in two sets of contact pads arranged such that a first set of contact pads formed on one side of the at least one photonic device and such that a second set of contact pads is formed on another side of the at least one photonic device thereby increasing the distance between the contact wires and thereby reducing cross-talk.

34. The OSA of claim 30, wherein the ceramic block includes internal shielding configured to reduce cross-talk in the OSA.