Wireless Telemetry Electronic Circuit Board for High Temperature Environments

• US 20100039779A1
• Filed: 08/15/2008
• Published: 02/18/2010
• Est. Priority Date: 08/15/2008
• Status: Active Grant

• Current Assignee: Cree Fayetteville, Inc. (Wolfspeed, Inc.)
• Original Assignee: Siemens Power Generation, Inc., Arkansas Power Electronics International, Inc. (Wolfspeed, Inc.)
• Inventors: FRALEY, JOHN R., ROESCH, EDWARD R., LOSTETTER, ALEXANDER B., MITCHELL, DAVID J., SCHUPBACH, ROBERTO, WESTERN, BRYON, WAITS, ROD, SUBRAMANIAN, RAMESH, KULKARNI, ANAND A., MCPHERSON, BRICE
• Granted Patent: US 8,023,269 B2
• Time in Patent Office: Days
• US Class Current: 361/739
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 13/02 for measuring temperature of moving fluids or granular materials capable of flow
• CPC Class Codes: G01K 13/024 of moving gases
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45139 Silver (Ag) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48472 the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• CPC Class Codes: H01L 2224/48644 Gold (Au) as principal constituent
• 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 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/13062 Junction field-effect transistor [JFET]
• CPC Class Codes: H01L 2924/20751 larger or equal to 10 microns less than 20 microns
• CPC Class Codes: H01L 2924/20752 larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H05K 1/092 Dispersed materials, e.g. conductive pastes or inks
• CPC Class Codes: H05K 2201/10674 Flip chip
• CPC Class Codes: H05K 2203/0186 Mask formed or laid on PCB, the mask having recesses or openings specially designed for mounting components or body parts thereof
• CPC Class Codes: H05K 2203/049 Wire bonding
• CPC Class Codes: H05K 2203/0557 : Non-printed masks
• CPC Class Codes: H05K 2203/1126 : Firing, i.e. heating a powder or paste above the melting temperature of at least one of its constituents
• CPC Class Codes: H05K 2203/167 : Using mechanical means for positioning, alignment or registration, e.g. using rod-in-hole alignment
• CPC Class Codes: H05K 3/102 : by bonding of conductive powder, i.e. metallic powder H05K3/12 takes precedence
• CPC Class Codes: H05K 3/1291 : Firing or sintering at relative high temperatures for patterns on inorganic boards, e.g. co-firing of circuits on green ceramic sheets
• CPC Class Codes: H05K 3/321 : by conductive adhesives
• CPC Class Codes: H05K 3/328 : by welding
• CPC Class Codes: Y10T 29/49128 : Assembling formed circuit to base
• CPC Class Codes: Y10T 29/49139 : by inserting component lead or terminal into base aperture
• CPC Class Codes: Y10T 29/49144 : by metal fusion
• CPC Class Codes: Y10T 29/53174 : Means to fasten electrical component to wiring board, base, or substrate
• CPC Class Codes: Y10T 428/2947 : Synthetic resin or polymer in plural coatings, each of different type

Abstract

A circuit assembly (34) resistant to high-temperature and high g centrifugal force is disclosed. A printed circuit board (42) is first fabricated from alumina and has conductive traces of said circuit formed thereon by the use of a thick film gold paste. Active and passive components of the circuit assembly are attached to the printed circuit board by means of gold powder diffused under high temperature. Gold wire is used for bonding between the circuit traces and the active components in order to complete the circuit assembly (34). Also, a method for manufacturing a circuit assembly resistant to elevated temperature is disclosed.

Claims

1. A circuit assembly resistant to high-temperature and high centrifugal (g) forces comprising:

a printed circuit board fabricated from alumina and having conductive traces of said circuit deposited thereon;

active and passive components of said circuit assembly being attached to said printed circuit board by means of gold powder diffused under high temperature; and

,

gold wire bonding between said circuit traces and said active components in order to complete said circuit assembly, said wire bonding being oriented parallel to a direction of centrifugal forces to be exerted upon said circuit assembly and having a diameter within the range of 0.7 mil and 1.0 mil.

2. The circuit assembly as in claim 1 wherein said passive components comprise a metal wire air core conductor affixed to said circuit traces of said printed circuit board for forming an inductive element of said circuit assembly.

3. The circuit assembly as in claim 2 where said conductor comprises a coil of gold or silver wire encased in an alumina-based potting material.

4. The circuit assembly as in claim 2 wherein said metal wire air core conductor is potted along the length thereof so as to prevent electrical shorts at high frequencies.

5. The circuit assembly as in claim 4 further comprising insulating tape on said potted wire where said wire crosses itself so as to prevent electrical shorts.

6. The circuit assembly as in claim 3 wherein said metal wire is formed into a bridge at cross over points thereof in order to prevent electrical shorts.

7. In a combustion turbine engine, a circuit assembly affixed to a stationary or moving part of said turbine engine for receiving sensed information about the condition of said part and transmitting said sensed information to a receiver external to said turbine engine, said circuit assembly comprising:

a printed circuit board comprising an alumina substrate and having conductive traces formed of a thick film gold paste deposited thereon;

active and passive components of said circuit assembly being attached to said printed circuit board by means of gold powder diffused under high temperature; and

,

gold wire bonding between said circuit traces and said active components in order to complete said circuit assembly, said gold wire bonding being oriented parallel to a direction of centrifugal forces to be exerted upon said circuit during operation of the turbine engine.

8. The circuit assembly as in claim 7 wherein said passive components comprise a metal wire air core conductor affixed to said circuit traces of said printed circuit board for forming an inductive element of said circuit assembly and potted along a length thereof so as to prevent electrical shorts at high frequencies.

15. The process as in claim 8 wherein the gold powder is deposited in the form of a gold paste for attaching the components to said printed circuit board.

9. A method for manufacturing a circuit assembly resistant to elevated temperature and high g forces, said method comprising the steps of:

locating a printed circuit board inside a transfer plate, said printed circuit board having gold circuit traces formed thereon;

positioning an alignment plate over said printed circuit board, said alignment plate having openings therein corresponding to size and location of components to be attached to said printed circuit board;

depositing gold powder in said openings of said alignment plate;

depositing said components inside of said openings in said alignment plate;

clamping said transfer plate containing said circuit assembly between a pair of heated graphite plates and subjecting all to elevated temperatures, whereby said gold powder diffuses into said printed circuit board and into said components, thereby forming a secure bond that can withstand elevated temperatures and high g-forces.

10. The process as in claim 9 wherein said transfer plate is made of graphite and is sized and shaped with at least one opening formed therein for receipt of said printed circuit board.

11. The process as in claim 9 wherein said alignment plate is made of stainless steel so as not to bond to said gold powder.

12. The process as in claim 9 wherein said alignment plate is made of ceramic so as not to bond to said gold powder.

13. The process as in claim 9 further including the step of bonding wire between said components and said circuit traces on said printed circuit board.

14. The process as in claim 13 wherein said bonding wire is made of gold and has a diameter within the range of 0.7 mil and 1.0 mil.