Connector for ceramic hybrid circuits for well- logging tools

CONNEC~OR FOR C~AMIC HYBRID CI~CUITS FOR WELL-LOGGING TOOLS A~D .~$T~OD ~OR CONNEC~ING ÇERAMIC HYBRID CI~C~ITS FOR USE IN WE~L-LOGGING TOOBS 1.

Field of the Invention ~5 ~he invention relat~s to: a connector ~or a ceramic h~rid circuit to operatively associate the circ~it to a cartridge chassis within a well~logging tool in a well barehole; a connector a~sem~ly for a ceramic hybrid circuit to mechanically connec~ the circuit to a cartridge chassis within 1 well-lc~ging tool in a well borehole; and a method for electrically connecting a ceramic hybrid circuit to other circuits within a well-logging tool intended for use in a well borehole.

2.

Description o~ the ~rior Art In well-lo~ging tools, for use in a well borehols, 3~ numerous types of instrumentatio~ are disposed within the well~logging tool to measure various types of information from the well borehole, as i5 w~ll known in the art.

The well-logging instrumentation is subiected to a unique range or severe enviroNmental conditions 7~ --2- during the operation of such instrumentation. A combination of cycles of extreme temperature differentials -- typical?y -25 to ~275 C. -- and severe shock and vibration for~es, often leads to mechanical ~ailure of some o the instrumentation components in the well-logging tool.

The problem is fundamental to any assembly of dissimilar materials, and is a result of mismatched coefficients of thermal expansio~ o~ the dissimilar materials.

The problem is further compounded by the necessity of having the component parts with mismatched coef~icients or thermal expansion to be firmly attached to one another to avoid destructive interference in the event of shock loadings or harmonic resonances caused by vibration ~orces.

In well-logging tool instrumentation, it is increasingly desirable to have hybrid integrated circuits based upon large ceramic substrates which must be mechanically connected to ~arious cartridge chassis, which are commonly manufactured of stainless steel or other metals, and elec~rically connected to other circuits in the tool via multiple electrical contacts.

one approach to overcome the foregoing described problems has been to rigidly join the dissimilar materials by a member that is free to deflect ~5 elastically to accomodate dif~erential e~pansion of the dissimilar materials.

Thus a third dissimilar material is interposed between the two dissimilar materials, the third material having a coefficlent of thermal expansion intermediate those of the two parts to be joined.

This 3a approach may reduce the severity of the di~ferential expansion or the components; however, mechanical resonances caused by vlbration may be severe.

579~ -3 Another approach to the foregoing described problem has been to join the two dissimilar materials ~y a material that deforms plasticaLly.

This approach may be a successful solution to the foregoing problem for components that do not have to be regularly replaced, particularly i~ the expasure to high temperature conditions tends to aid plastic deformation and subsequent recovery.

However, the maj~r disadvantage associated with the foregoing aQproach is that most .

plastic materials will suffer eventual failure through repeated.plastic-flow cycles.

Additionally, because of the extreme temperature and pressure conditions in a borehole, as well as potentially severe shock and vibration forces, well-logging instrumentation components tend to require regular replacem~nt.

With both of the previously described solutions, in order to replace failed ceramic hybrid circuits, the use of specialized extrac~ion or soldexing tools to remove the ceramic hybrid circuit from the well-logging tool is required.

Accordingly, prior to the development of the prese~t invention, ~here has been neither a method for . electrically connecting a ceramic hybrid circuit to other circuits within a well-logging tool, nor a con~ector for a ceramic hybrid circuit to mechanically connect the circuit to a cartridge chassis wit~in a well-logging tool in a well borehole, which: is not subject to destructive interf.erence in the event of shock loadings or harmcnic resonances caused by vibration; allows failed ceramic hybrid circuits to be readily replaced without specialized extraction or soldering tools; and is capable of withstanding cycles of extreme temperature differentials in the borehole without causing mechanical failure, such as cracking, of the ceramic hybrid circuits.

Therefore, the ar-t has sought a method of electrically connecting ceramic hybrid circuits, and a connector therefor, for use with a well-logging tool within a well borehole, which: allows failed ceramic hybrid circuits to be readily replaced in the well-logging tool; is capable of withstanding cycles of extreme temperature differentials; and avoids destructive interference in the event of shock loadings or harmonic resonances caused by vibration forces.

SUMMARY OF THE INVENTION ... .

In accordance with a broad aspect of the invention there is provided a connector for a ceramic hybrid circuit to operatively associate the circuit to a cartridge chassis within a well-logging tool intended for use in a well borehole, comprising:

a base mem~er adapted to be secured to the cartridge chassis and including means for positioning the ceramic hybrid circuit with respect to the base member to prevent gross movement of the ceramic hy~rid circuit under severe shock conditions, said positioning means comprising a recessed support surface which generally conforms to the outer configuration of the ceramic hybrid circuit when the ceramic hybrid circuit has experienced its greatest expansion due to increased temperature conditions in the borehole;

a latch member engageable with the base member; and a plurality of electrically conauctive contact pins for supporting and contacting the ceramic hybrid circuit between the base member and the latch member, said plurality of pins being disposed in the recessed support surface and extending outwardly therefrom, each of said pins having an elongate hous ing member supported by the base member, a contact member mount ed on the housing member and axiall~ slidable with respect thereto toward an extended position in which the end of the -- 5 - contact member protrudes from the housing member to contact the hybrid circuit and a spring mounted between the housing member and the contact member to urge the latter towards said extended position, the springs of the contact pins having a spring force sufficient to exert a combined force upon the ceramic hybrid circuit to sufficiently restrain the ceramic hybrid circuit to prevent damage thereto from contact scrubbing action, shock and vibration forces exerted upon the well-logging tool which are imparted to the cartridge chassis, and to maintain the ceramic hybrid circuit in low resistance electrical contact with the contact pins.

~",, L S r7 4L 9~ ~IE~ DESCRIPTION OF T~E DRAWINGS In ~he drawings:

FIG. l is a graph illustrating pro~lems of joining dissimilar materials having different coefficients of thermal expansion;

FIG. 2 is a schematic diagram of a connector in accordance with the present invention;

FIG. 3 is a side view of a connector and connector ~ssembly in accordance with the present invention:

1S) FIG. 4 is a top view of a connector and connector assembly in accordance with the present invention;

FIG. S is a partial cross-sectional view of a contact pin of the connector in accordance with the present invention;

FIG. ~ is a schematic ~orce diagram illustrating the forces between the connector pins and ceramic hybrid 2U circuit contacts, in accordance with the present invention; and FIG. 7 is a graph illustrating the relationship between the contact force and contact force per unit area o~ the contact pin and ceramic hybrid circuit in accordance with the present invention.

While the invention will be described in connection with the preferred embodiment, it will be understood that it is not intended to limit the invention to that emb~diment.

On the contrary, it is intended to cover all alternatives, modifica-tions, and equivalents 2S may be included within the spirit and SCOp2 of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION With reference to FIG. 1, the fundamental problem of the wide divergence in expansion of dissimilar materials as a re.sult of their different coefficients of thermal expansion is illus-trated. ~s seen in FIG. 1 the percentage expansion of three materials is plott~d against increasing temperature, the upper temperature ranges corresponding to the extreme temperatures e~perienced in a well borehole.

The stainless steel 1o plot 80 repres~nts the normal material of the well-lagging to~l housing and cartridge cha s.is of the well-logging tool.

The plot 81 for alumina caramic materials represent the ceramic matQrial used for hybrid circuit substrates.

Plot 82 represents the percentage e~pansion of silicon, the most commonly used material for active electronic instrumentation devices.

Such silicon devices may be attached rigidly to the ceramic without causing faiLure.

As illustrated in FIG. 1, alumina ceramics will not tolerate strains much graater than 0.1~ without failur2, such as a cracking of the alumina ceramic hybrid circuit substrate.

Thus, free and sufficient motion is required bet~een the alumina ceramic substrate and the metal, such as stainles3 stPel, components of the well-logging tool housing and cartridge chassis members when the total differentlal expansion approaches 0.25~ over a 300 C. range.

In accordance with the present invention, a principle of operation of:the connector, connector assembly, and method there~or is illustrated in FIG. 2.

A. plurali'cy of sprlng-loaded colltact pins 83 is shown : schematically and is disposed between a base mem~er 84, and a ceramic hybrid circuit substrate 85 which has th hybrid circuit disposed thereon, lncludlng a plurality 5 of îlat, planar contact sur~aces 86.

The ceramic hybrid circ~it substrate 85, hybrid circuit, and flat planar '7~ --8- hybrid circuit contact surfaces 86 are well known in the hybrid circuit art, and are designed in accordance with the desired well-logging instrumentation to be utilized to measure various property characteristics in the well borehole.

The ceramic hybrid circuit sub~trate 85 may, for example, be relatively large, such as 3.~ x 9.l cm., with a rectangular configuration.

Substrate 85 may have many contact surfaces 86 disposed thereon, even severaL - hundred; as shown herein, 36 contact surfaces are 1o disposed along each of the longer sides of the ceramic hybrid circuit substrate 8~.

The ceramic hybrid circuit substrate 85 is disposed between the contact 2ins 83 and a base chassis member 87.

Each spring-loaded contact pin 83 includes a spring 88 and a contact pin contact surface 89 which preferably has a spherical configuration as illustrated in FIG. 2, as will be hereinafter described in greater detail.

Thus, a plurality of multiple, independent ~lectrical contacts is provided bet-~een contact surac~s 86 and the spherical contact surfaces 89 of contact pins 83.

In order to provide a reliable low-resistance electrical circuit, which circuitry and its related comp~nents, as . will be hereinafter described, can withstand the severe shoc~, vibration, and temperature environment of a well borehole, sufficient forces from the springs 88 of contact pins 83 must be exerted again t the contact surfaces 86 of the ceramic hybrid circuit substrate 85.

Still with reference to FIG. 2, the force in each contact pin 83 must be ~uficient to make electrical connection at the mating contact surf aces ~ 6 or ceramic hybrid circuit substrate 85 and contact surfac- 89 of contact pin 83, and oppo 2 any motion of the moveable contact surfaces 89 of contact pins 83, which have a mass m. A total force of nr is applied f~r n contac~s - 9 89, acting against the total mass M of the entire ceramic hybrid circuit substrate 85.

The critical acceleration factor G which will cause relative motion of the ceramic hybrid circuit substrate 85 if applied in a direction opposite to the spring forces nf is then given by the following fonmulae:

For the contact surface 86,89/ substrate 85 connection, GCS For the substrate 8S/base c~assis 87 connec~ion~ GsB = ~ where G i measured in units of g, the un versal acceleration constant due to gravity.

The self-xesonant fre~uencies of ~he corresponding mechanisms may be readily detexmined from the same constants:

For the movable contact sur.ace 89, F~ ~11 ~v For the ceramic hybxid circuit substrate 8S, F5 = 1 ~ Wherz S = Contact spring-rate 3~ _ f/d d = Spring deflection at fQrce f.

As an example, some typical values for the various parametGrs used in well-logging tools are:

~.2~ --10- f = 100 gm. force m = 0.04 gm.

n = 72 d = 0.2 cm.

M = 30 gm.

g = ~81 cm./sec then, ~ Gcs a 2 5 0 0 g ~s~ = 2~0 g F~ = 557 ~z .~S = 173 Hz The foregoing results for Gcs I G5~ .

Fc ~ and Fs are consistent with the re~uirements of well-logging tools.

Still with reference to FIG. 2, it should be noted that when the forces encountered by a well-logging tcol are tra~smitted to the ceramic hybrid circuit substrate . 85, base chassis member 87, and base member 84 in a direction orthogonally to the axis of sprin~s 88, the ceramic hybrid circuit substrate 85 is restrained by frictional forces between the substrate 85 and base chassis member 87.

If the frictional constant at the inter.ace between base chassis member 87 and ceramic hybrid circuit substrate 85 is F, then a lateral 3~ acceleration factor may be calculated as follows:

Por the lateral substrate 85/base chassis 87 connection, G58~ = nr ~2~ ~ . , .

This lateral motion is undesirable since it may cause a "scrubbing" of the electrical contact surfaces 86 and 89 which, if sustained for extended periods of time, will cause eventual failure of the contacts. ~owever, since F may be in the xange of 0.8-1.0 dependent upon the substrate a5/b~se chassis 87 interface properties, then:

192 g < GS~L ~ 2~ o3 which value should not promote a scrubbing action of the electrical contacts 86 and 89.

Isolated incidents of such scrubbing action may however be tolerated, if caused by occasional extreme shock forces, without significant damage.

Of paramount importance, is that the foragoins lateraL friction force between t~e ceramic hybrid circuit substrate 85 and base chassis me0~er 87 is insu~icient to unduly restrain the differential ex2ansion between the ceramic hybrid circuit substrate 85 and the base chassis membex 87 caused by increas~d . temperatu~es in the well borehole, whereby thexa is only a very remote possibility of thP ceramic hy~rid circuit substrate 85 fracturing as a result of such differential expansion.

Thus, the ceramic hybrid circuit ~ubstrate 85 may freely and sufficiently expand in response to increased temperature conditions, while at the same- tlme a reliable low-resistance electrical circuit is provided 3a between the contacts 89 a~d 86 which can withstand severe shoc~ and vi~ration forces which ar~ encountered by ~ell-logging tools in a well borehole.

With reference now to FIGS. 3 and 4, the connector 90 and connector assemblv 91 of the present invention 7~4 ~12 will be described in greater detail.

The connector 90 and conn~ctor assembly 91 of the present invention incorporate t~e principles previously described with respect to FIGS. 1 and 2.

As seen in FIGS. 3 and 4, the ceramic hybrid circuit substrate 85, havi~g the hybrid circuit and its contact suraces 86 thereon i5 disposed between a base member 84 and a latch member 92 engageable with the base member 84.

As seen in FI5. 3, in dotted lines, latch member 92 is shown in an open position, and in solid lines in a closed position engaged to base member 84.

Base member 84 is adapted to be secured to a cartridge chassis 93 which is disposed within a well-logging tool (not shown).

Cartridge chassis 93 may normally be made of stainless steel and is provided with screw threads 94 adapted to receive a bolt (not shown) which passes through openings 95 in base member 84, whereby base member 84 is secured to the cartridge chassis 93.

Base member 84 and latch member 92 may be manufactured of any suitable material;

however, it is preferred that base member 84 be manufactured oE an elect~ically non-conductive plastic . material such as a silicone resin/glass powder composite, and latch mem~er 92 may be manufactured of aluminum.

Base member 84 should have a coefficient of . thermal expansion close to that of the cartridge chassis 93.

With reference to FIGS. 2 and 3, it should ~e noted that base member 84 is the same in both figures, and base chassis member 87 of FIG. 2 has latch member 92 substituted therefor in FIG. 3.

Thus, the geometry or the various compone~ts, and the previously descri~ed formulae and calculations, ara likewise appLicable to the connector 90 and connector assembly 91 of FIGS. 3 and 4.

5~ -13 Still with ref~rence to FIGS. 3 and 4, it is seen that latch member 92 is pivotably mounted to the base member 84 as by a hinge 96 disposed on a first end 97 of latch ~ember 92, and the second end 98 of latch member 92 is provided with a releasable latch 9~ which en~ages the base member 84 as seen in FIG. 3. ~eleasable latch 99 may include a spring-loaded tab lO0 which pivots about a pivot pin 101, the lower end of tab lO0 being normally biased toward the latch member 84 as by a spring 102.

The lowe~ e~d of tab lO0 may preferably have a projection 103 formed therein which engages a mating projection 104 disposed on the base memb~r 84 as sesn in FIG. 3.

Still with reference to FIGS. 3 and 4, it is seen that a plurality of spri~s~loaded, electrically conductive contact pins 83 are disposed o~ the base member 84 for supparting and contacting the ceramic hybrid circ~it substrate 85 between the bas2 ~ember 84 and the latch member 92, w~ere~y the ceramic hy~rid circuit substrate 85 may sufficiently and freely move, without damage theret~, with respect to the base member 34 and latch member 92 as a result o~ thenmal expansion and contraction caused by temperature changes in the borehole, while the caramic hybrid circuit substrate 85 is sufficiently restrained to prevent damage thereto from shock forces and vibration forces exerted up~n the well-logging tool which are imparted to the ca~tridge chassis 93.

Further, the ceramic hybrid circuit substrate 85 and ceramic hybrid circuit contact sur~aces 86 will remain in low-resistance electrical contact with the contact pins 83 and the cartridge chassis 93, as pre~iously described and explained with reference to FIG. 2.

-14 Still with reference to FIGS. 3 and 4, it is seen that the base member 84 may include means for positioning ceramic hybrid circuit substrate 85 with respect to base mem~er 84 to li~it any gross movement of S the ceramic hybrid circuit substrate 85 under severe shocX and vibration conditions.

The means for positioning 105 may comprise a recessed support surface 10~ which generally con~orms to the outer configuration of the ceramic hybrid circuit substrate 85, when the 1 a ceramic hybrid circuit substrate 85 has experienced its greatest expansion due to increased temperature conditions in the borehole.

The recessed support surface 106 is seen in FIG. 4 as including a recessed ledge (shown in d~tted lines) e~tending the length of the two longer sides of the ceramic hybrid circuit substrate 85.

Pre~erably, the plurality o~ contact pins 83 are disposed in the recessed support surf ace 106, and the contact pins a3 extend outwardly from the recessed support surface lC6 as seen in FIG. 3.

As discussed with re~pect to FIG. 2, the forces exerted by the spring-loaded contact pins 83 upon ceramic hybrid circuit substrate 85 and ceramic hybrid circuit contact surfaces 86 are sufficient to ma.k2 an electrical connection there~etween and to oppose any relative motio~ between the ceramic hybrid circuit and substrate 85 and the base member 84, when an external shock ~orce is transmitted through the well-logging tool in any direction but particularly a direction perpendicular ~o the forces exerted by the spring-loaded contact pins 3~ ~3.

As shown in FIGS. 3, 5, and 6, contact pins 83 ha~e a first end 107 intended for connection to an electrical wiring ha~ness, a plurality of insula~ed electrical ~ires, (not shown), so that connections may be made ~1579L~ --15- between electrical circuits on the hybrid circuit 85 and other circuits in the well-logging tool~ The second end lO9 of contact pins 83 has a spherical contact surface 89 for contacti~g the ceramic hybrid circuit contact surfaces 86. With refere~ce to FIG. 5, the structure of the contact pins 83 is shown to include a senerally cylindrical housing 110 having a contact member lll disposed therein for relative movement therebetween.

Contact member lll has the spherical contact surfac- 89 at one end and an enlarged end portion 112 which is restrai~ed from outward movement from housing L10 as by a crimped portion 113 in housing llOo A suitable spring 114 is capturad between the end of housing 110 and the enlarged end portion 112 of contact member lll.

With reference to FIGS. 6 and 7, the details of operation of the contact pins 83 will be described in greater detail. In FIG. 6, f represents the force exerted by spring 114 of contact pin 83, R represents the radius OL curvature of the spherical contact surface 89 of contact member 111, E represents the elastic m~dul~s for the material of which the spherical contact surface 89 is manufactured, and 86 represents the flat, planar contact surface of the ceramic hybrid circuit and substrate 85.

Electrical contact is made between the spherical contact surface 89 and the flat, planar contact surface 86 of ceramic hybrid circuit and substrate 85 without a scrubbin~ action, as previously described, as a result of the very high pr~ssure force available when a spherical sur~ace, such as spherical contact surface 89, comes in~to contact with a flat, planar surf~ce, such as contact surface 86.

Preferably, the two contact surfaces 89 and ~6 are noble-metal surfaces, contact surface 86 preferably being a 1~215744 .

-16 thick~film gold material disposed on the ceramic hybrid circuit substrate 85.

It should of course ~e recognized by one skilled in the art, that contact pins 83 could be associated with the latch member 92 with the first ends 107 of contact pins connected to other circuits i~ the well-logging tool as by an electrical wiring harness.

Ceramic hybrid circuit 85 would then be disposed on base member 84 with 1~ the contact suxfaces 86 facing upwardly to be engaged by the spherical contact surfaces ~9 of the second ends 109 of the contact plns 83, upon latch member 92 being closed as sho~n in FIG~ 3.

With reference to FIG. 7, the plotted curve depicts how the peak contact force/unit area rises to a value suficient to enable the spherical contact surface 89 to pass through any contaminants, particularly all kncwn organic contaminants ~16, as seen in FIG. 6, which may 2~ be present on the contact surface 86.

The plotted curve 115 also depicts how the spherical contact surface 89 may be deformed elastically as the contaminants 116 are swept aside, until the force/unit area approaches the elastic limit for the material of which spherical contact surface 8~ is manufactured.

In FIG. 6, the arrows 117 illustrate the contact area between contact surfaces 89 and e6 due to elastic deformation of the spherical contact urface 8g.

Thus, a reliable electrical connection between contact sur~aces ~9 and 86 3~ may be obtained ~it~out the need to plastically deform the contact material of spherical contact surfacs 89 ~y correctly choo5i~g the radius R of the spherical contact sur~ace 89, and a material having the requisite elastic modulus E to manufact~re the spherical contact surface 3S 744 .

-17 99, and a force f resulting from the compression of spring 114.

With reference to FIG. 3, the methcd for electrically connecting a ceramic hybrid circuit 8~ to a cartridge chassis 93 within a well-loggi~g tool in a well borehole in accordance with the presçnt invention will be described. The method steps include securing the base member 84 to the cartridge chassis 93, such as by bolts ~not shown), which mate with thr~aded openlngs 94 in cartridge chassis 93. A plurality of spring-loaded, electrically conductive contact pins 83 is then disposed with first end 107 c~ each contact pin 83 in electrically conductive relationship with a wiring harness (not shown).

The ceramic hybrid circuit 85 is then placed upon the base mem~er 84 in an overlying relationship to the contact pins 83. La~ch member 92 is then engaged to the base member 84, as by the latc~ 99.

The ceramic hybrid circuit and substrate 35 is then supported between the base member 84 and the latch member 92 by a second end 109 of each contact pin 83.

The ceramic hybrid circuit and substrate 85 is allowed to sufficiently and freely move, with respect to th~ base member 84 and the latch member 92, without damage thereto, as a result of thermal e~pansion and contraction thereof caused by temperature changes in the borehole.

The ceramic hybrid circuit and substrate 85 is caused to remain in a low-resistance electrical contact with the s~cond end 109 of each contact end 83.

The contact pins 83 are provided with spherical contact surfaces 8g to contact the ceramic hybrid circuit contact surfaces 36 and a scrubbing action between the contact pins 83 and the ceramic h~bri~ circuit contact surfac~s 86 is prevented.

The spherical contact 7~ surfaces 89 are passed through any organic contaminant~ 116 on the ceramic hybrid circuit contact surfaces 86.

It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiment shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art; for example, the latch member could be provided with a latch at either of its ends for engagement with the base member, and additional rows of contact pins could be provided.

Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

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