Integrated circuit transmission line

• US 8,377,749 B1
• Filed: 09/15/2009
• Issued: 02/19/2013
• Est. Priority Date: 09/15/2009
• Status: Expired due to Fees

• Current Assignee: MACOM Connectivity Solutions, LLC (MACOM Technology Solutions Holdings, Inc.)
• Original Assignee: Applied Micro Circuits Corporation (MACOM Technology Solutions Holdings, Inc.)
• Inventors: Patterson, Joseph Martin
• Primary Examiner(s): Picardat, Kevin M
• Application Number:
  US12/560,187
• Time in Patent Office: 1,253 Days
• Field of Search: 438/111, 438/112, 438/123, 438/124, 438/126, 438/127
• US Class Current: 438/123
• CPC Class Codes: H01L 2223/6611 Wire connections
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/451 with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/85399 Material
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 23/66 High-frequency adaptations
• 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 24/49 of a plurality of wire connectors
• CPC Class Codes: H01L 24/85 using a wire connector wire bonding in general B23K20/004
• 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 2924/00014 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 2924/15153 the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: H01L 2924/15165 : Monolayer substrate
• CPC Class Codes: H01L 2924/3011 : Impedance
• CPC Class Codes: H01L 2924/30111 : matching
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding

Abstract

A method is provided for fabricating a transmission line between electrical circuits. The method initially provides a first electrical circuit with a signal interface and a reference voltage interface, and a second electrical circuit with a signal interface and a reference voltage interface. The first circuit signal interface is connected to the second circuit signal interface with a metal wire. An insulator coating (e.g., poly-para-xylylene) is formed, encapsulating the wire. Then, an electrically conductive coating is formed, encapsulating the insulator coating. Typically, the conductive coating is connected to at least one of the first and second circuit reference voltage interfaces. In one aspect, the first circuit signal interface connection to the second circuit signal interface is a transmission line formed from the combination of the wire, insulator coating, and conductive coating. The transmission line has a frequency-dependent characteristic impedance responsive to the wire diameter, insulator thickness, and dielectric constant.

Claims

1. A method for fabricating a transmission line between electrical circuits, the method comprising:

providing a wire coupling a first electrical circuit with a signal interface to a second electrical circuit with a signal interface, the wire comprising a predetermined diameter;

forming an insulator coating encapsulating the wire, wherein the insulator coating comprising a predetermined thickness and a predetermined dielectric constant;

forming an electrically conductive coating encapsulating the insulator coating; and

forming a transmission line from the combination of the wire, the insulator coating and the electrically conductive coating, the transmission line comprising a controlled frequency-dependent characteristic impedance responsive to the predetermined diameter of the wire, the predetermined thickness of the insulating coating and the predetermined dielectric constant of the insulator coating.

2. The method of claim 1 wherein each of the first and second electrical circuits comprises at least one reference voltage interface;

and,

wherein further forming the conductive coating includes connecting the conductive coating to the at least one of the first and second circuit reference voltage interfaces.

3. The method of claim 1 wherein forming the insulator coating includes forming a poly-para-xylylene coating.

4. The method of claim 1 wherein forming the electrically conductive coating includes forming an electrically conductive coating from a material selected from a group consisting of carbon paint, conductive epoxy paint, copper, silver, gold, and overmolded bulk conductive epoxy.

5. The method of claim 4 wherein forming the electrically conductive coating includes using a process selected from a group consisting of sputtering, chemical vapor deposition (CVD), evaporation, dipping, and electroplating.

6. The method of claim 1 further comprising:

prior to forming the insulator coating, masking the reference voltage interfaces; and

,

subsequent to forming the insulator coating and prior to forming the electrically conductive coating, removing the reference voltage interface masks.

7. A method for fabricating transmission line wire bonds between an integrated circuit (IC) die and a chip carrier, the method comprising:

providing a plurality of wire bonds between an IC die with a plurality of signal interfaces and a plurality of chip carrier signal lead frames, the plurality of wire bonds comprising a predetermined diameter;

forming an insulator coating encapsulating each of the plurality of wire bonds, the insulator coating comprising a predetermined thickness and a predetermined dielectric constant; and

,

forming an electrically conductive coating encapsulating each insulator coating;

forming a transmission lines from the combination of each of the plurality of wire bonds, the insulator coating and the electrically conductive coating that encapsulate each of the plurality of wire bonds, each transmission line comprising a controlled frequency-dependent characteristic impedance responsive to the predetermined diameter of the plurality of wire bonds, the predetermined thickness of the insulator coating, and the predetermined dielectric constant of the insulator coating.

8. The method of claim 7 wherein the IC die comprises a reference voltage interface, and wherein the chip carrier comprises a reference voltage lead frame interface;

and,

wherein forming the electrically conductive coating includes connecting the electrically conductive coating to at least one of the IC die and chip carrier signal lead frame reference voltage interfaces.

9. The method of claim 7 wherein forming the insulator coating includes forming a poly-para-xylylene coating.

10. The method of claim 7 wherein forming the electrically conductive coating includes forming a conductive coating from a material selected from a group consisting of carbon paint, conductive epoxy paint, copper, silver, gold, and overmolded bulk conductive epoxy.

11. The method of claim 7 further comprising:

prior to forming the insulator coating, masking the die reference voltage interface and a reference voltage lead frame contact point; and

,

subsequent to forming the insulator coating and prior to forming the electrically conductive coating, removing the reference voltage interface masks.

12. An integrated circuit (IC) with transmission line wire bonds between a die and a chip carrier, the IC comprising:

an electrical circuit die with a plurality of signal interfaces and at least one reference voltage interface;

a chip carrier with a plurality of signal lead frames and at least one reference voltage lead frame;

shielded connectors between the die signal interfaces and the chip carrier signal lead frames, each shielded connector including;

a wire bonded to a die signal interface and a signal lead frame, the wire comprising a predetermined diameter;

an insulator coating encapsulating the wire; and

,

an electrically conductive coating encapsulating the insulator coating;

wherein the insulator coating comprises a predetermined thickness and dielectric constant;

wherein the insulator coating isotropically covers unmasked portions of the die and chip carrier, including the wire;

wherein the conductive coating isotropically covers unmasked portions of the die and chip carrier and is connected to the die reference voltage interface and the reference voltage lead frame; and

,

wherein the combination of each wire bond, insulator coating, and conductive coating forms a transmission line comprise a controlled frequency-dependent characteristic impedance responsive to the wire diameter, insulator thickness, and dielectric constant.

13. The IC of claim 12 wherein the insulator coating is poly-para-xylylene.

14. The IC of claim 12 wherein the conductive coating is a material selected from a group consisting of carbon paint, conductive epoxy paint, copper, silver, gold, and overmolded bulk conductive epoxy.