CA1085654A

CA1085654A - Electrical contact

Info

Publication number: CA1085654A
Application number: CA267,143A
Authority: CA
Inventors: Ronald N. Caron; Stanley Shapiro
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1976-01-19
Filing date: 1976-12-03
Publication date: 1980-09-16
Also published as: IT1126705B; GB1514147A; JPS5288789A; FR2338585A2; DE2700275A1; FR2338585B2

Abstract

ABSTRACT OF THE DISCLOSURE
High strength copper base alloy electrical connectors having good stress corrosion resistance, stress relaxation resistance and good strength to bend ductility. The connectors contain from 1 to 5% tin, 1 to 4.5% silicon and a minimum tin plus silicon content of 3.5%.

Description

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108565i4 .
SUPPLEMENTAR~ DISCLOSURE

It has been found that the alloys of the pr~sent inventlon are partlcularly useful as electrical connector~
or contacting springs. Copper ~ase alloys are widely used as electronic and electrical connectors for terminals. These connectors are most often designed as ~lexural sprin~s, and electrical contact is maintained by the action of the bending stresses that are developed. A high~ stable contact pressure assures a reliable electrical contact and thus ls an impor~ant per~ormance criterion for electrical connectors.
It is,therefore, highly desirable to provide a high strength copper base alloy electrical connector having a desirable combination of properties lncluding excellent stress corrosion resistance, excellent stress relaxation resistance, and general corrosion reslstance especially in severe ammoni-acal environments. It ls also deslrable to provlde such a material having good strength to bend ductility. Furthermore, it is particularly desirable to provide such a material which can be ine~pensively and expeditiously prepared on a commercial scale.
~he provision of a material of this type would satis~y the stringent requlrements imposed by modern applications ~or electrical contact` springs, for example, in whlch spring temper mechanical properties are required coupled with adequate bend formability and with stress corrosion resl~tance in severe ammoniacal environments which are generated during decomposition of organic electrical insulation materials.
SUMMARY OF THE INVENTION
In accordance with the present lnvention it has been found that an improved high strength copper base alloy ~'^t~'.~' .

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electrical connector or contact~ng spring may be provided having good stress corroslon resistance, good stress relaxation reslstance and good strength to bend ductility. The connector of the present invention has a composition consisting essentially of from 1.0 to 4.5% silicon, from 1.0 to 5.0% tin, wlth a minimum silicon plus tin content being 3.5%, balance copper. In addition, the connector o~ the present lnvention has a portion for matlng engagement with a ~econd electrical connector or terminal so that said portion is placed under stress during said mating ~ngagement wlth said second electrical connector. Generally, the connector of the present invention is a strip material having at least one bent portion.
Thus, the excellent properties of the connector of the present invention are particularly useful in the ~abrication of the connector.
In a preferred embodiment the connectors of the present invention contain a ~irst additive selected ~rom the group ; consisting of from 0.01 to 2.0% iron, from 0.01 to 2.0%
cobalt and mixtures thereof, with a maximum total iron plus cobalt content being 3.0%. In addition, it is pre~erred that the connectors of the present invention contain a second additive selected from the group consisting of: Nickel from 0.01 to 5.0%, manganese from 0.01 to 5.0%, titanium from 0.01 to 5.0%~ zirconium from 0.01 to 5.0%, hafnium ~rom 0.01 to 5.0%, chromium from 0.01 to 2.0%, beryllium from 0.01 to 3.0%, vanadium from 0.01 to 5.0%, and magnesium from 0.01 to

2.0% and mixtures thereof. The total content o~ said first additive plus said second additive should be less than 10.0%.
In addition, optimum properties are obtained when the resultant wrought connector ls characterized by a fineg ~ 6034-MB

~V~SGS4 uniform precipitation of said second additive dispersed -throughout the matrix. Naturally, the first additive may be present in the connector independently o~ the second additive, and the second additive may be present in the connector independently o~ the first additlve, so that the connector may contain the ~irst additive without the second additi~e, or the second additive without the first additlve, or preferably both may be present together.
It has been found that the copper base alloy connectors o~ the present invention provide highly desirable, high -mechanical strength, excellent stress corrosion resistance and general corroslon resistance, especially in severe ammoniacal environments, plus good stress relaxation resist-ance. In addition, the connectors of the present inventlon are inexpensively and conveniently prepared on a commercial , scale.
BRIEF DESCRIPTION OF THE DRAWINGS
; Figure lA is a representative connector of the present invention disengaged from a second connector.
Figure lB shows the connector of Figure lA in mating engagement with the second connector.
Figures 2A, 2B, 3A, 3B, 4A and 4B show alternate typical embodiments of connectors o~ the present invention.
Figure 5 is a graph showing the stress rela~ation behavior o~ the connector o~ the present in~ention compared wlth representative commercial materials plotting the stress remaining ln ksi in the longitudinal orientation in the heat treated condition as the ordinate versus the as-rolled minimum badway bend radius as the ~bscissa.
3o DETAILED DESCRIPTION OF THE PREFER~ED EMBODIMENTS
As lndicated hereinabove, copper base alloy electrical connectors are most often designed as ~lexural springs with the electrical contact malntained by the action of the bending stresses that are developed. Thus, as can be seen in Figures lA and lB, the electrical connector 1 o~ the present invention has a portion 2 for mating engagement w~th a second electrical connector 3 so that said portion 2 is placed under stress during mating engagement with said second electrical connector ~;

3 as clearly shown in ~igures lA and lB. In addition, generally the connector of the present invention is a strip materlal having at least one bent portion, as flanges 4 and 5.
Thus, the connector o~ the present invention is placed under stress in contact with a second electrical connector. With - time) stress relaxation will degrade the contact pressure and result in poor electrical contact between the two connectors.
This can also be seen in the alternate embodiments o~ the connector of the present invention shown in Figures 2, 3 and

4, all o~ which show the connector placed under stress during mating engagement with a second connector. Naturally, these ~ embodiments are intended to be illustrative only, and ; numerous other embodiments may be provided within the scope of the present invention.
In accordance with the present invention, the connector o~ the present invention is characterized by a particularly desirable combination of properties which render said ~ .

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5 ~ S 4 connector well suited ~or a variety o~ applications wherein at least a portion o~ said connector is placed under stress in contact with a second electrical connector.
In accordance wlth the present invention, the silicon and tin components provide maximum solid solution strengthen-ing and work hardening, with the silicon contenk being crucial for desired stress corroslon resistance. The ~irst and second additlves referred to hereinabove are preferred to obtain optimum physical properties. These materlals generally ~orm dispersed or precipitated second phases. The morphology of these phases is controlled during processing to provide dispersion strengthening and grain refinement and/or precipitation hardening especially during an aging treatment.
In addltion to the foregoing, it is preferred to utilize a third additive selected from the ~ollowing group and mixtures thereof, from 0.01 to 3.0% each o~ the following materials and mi~tures thereof: Arsenic, antimony, aluminum and zinc. The ~oregoing third additives should be presenk in a maximum total o~ less than 5.0%. ~he aluminum addition is particularly desirable in combination with the nickel or manganese component. Naturally, the third additive may be present in the alloy independently o~ the ~irst and second additives, or in combination with either the ~irst or second additives, or preferably in combination with both the firsk and second additives.

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The fore~oing alloys used in the connectors of the present inventlon may be readily and conveniently processed on a commercial scale ln accordance with the procedure outlined in the main case. Thus, the casting procedure~
hot rolling procedure, heat treatment, cold rolling and annealing procedures are as outlined in the main case.
In accordance with the present invention, the processed material is formed into the desired connector. One will preferably per~orm a heat treatment step on the formed part in order to provide greater stress relaxation properties.
This final heat treatment step should be conducted at a temperature o~ from 150 to 400C for from 15 minutes to 8 hours.
The connectors o~ the present invention may be formed by stamping, bending, crimping or the like~ Contact with an electrlcal conductor or wire at ~he non-stressed portions may be provided by solder or solderless type connections. It is an advantage of the present lnvention that the instant connectors can be formed and bent and stressed in any direction relative to the sheet rolling direction.
The present invention will be more readily apparent from a consideration of the ~ollowing illustrative examples.

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~)1356~4 - -EXAMPLE I
Alloy A of the connector o~ the present invention, consisting o~ 3% silicong 2.5% tin, 1.5% iron and the balance copper, was cast ~rom 1200C into a skeel mold with a water-~; cooled copper base. The lO lb. ingot was soaked at 750C for 2 hours and immediately hot rolled to 0.375" at a hot rolling finishing temperature ln excess of 400C, followed by cold rolling to 0.100" at a temperature below 200C. The alloy was then annealed ~or l hour at 450~C ~ollowed by further processing as follows to provide metal at 0.020" gage in the as-quenched and 40, 60 and 80% cold rolled condition. Some metal was cold rolled directly to 0.020" gage, i.e., 80% cold rolled metal. Some metal was cold rolled to 0.050" gage, annealed at 450C ~or l hour and cold rolled to 0.020" gage, i.e., 60% cold rolled metal. Some metal was aold rolled to 0.033" gage, annealed at 450C ~or 1 hour and cold rolled to 0.020" gage, i.e., 40% cold rolled metal. Some o~ the 40%
cold rolled metal was annealed at 0.020" gage at 450C for 1 hour to provide annealed metal, i.e., 0% reduction. The tensile properties o~ these condltions are listed in Table I
below. These properties are compared with those of the commercial high strength copper base alloys, Alloy B (a commercial alloy designated as CDA Alloy 510 - having the composition 4.4% tin, 0.07% phosphorus, and the balance essentially copper) and Alloy C (a commercial alloy designated as CDA Alloy 638 - having the composition 2.7% aluminum, ; '' ' ~ ~;

lV 8S6 54 1.7% silicon, 0.4% cobalt, bala~ce essentially copper).
~ he data in ~able ~ below clearly demonstrates the slgni~icant rolled temper strength advantages obtalned in accordance with the present in~ention wh~ch are partlcularly use~ul in the electrical connectors of the present in~ention.
In addition, the graln ~izes Or these alloys were as follows:
Alloy A - O.005 mm., Alloy B - O.010 mm.; and Alloy C -O.005 mm. Both Al}oy A of the present invention and commercial Alloy 638 were characterized by particulate phases uniformly distributed throughout the matrix. The particulate pha~e in the alloy o~ the present in~ention was a mixture of alpha iron and iron silicide.
TABLE I
TENSILE PROPERTIES
Alloy% Cold 0.2% Yield ~ltlmate Reduction Strength Tensile (ksi) Stren~th Elongation _ (k8i) (%) ~ 0 40 56 46 A 40 109 130 2.0 B 40 93 97 5.0 C 40 99 120 5.0 A 60 125 142 1.2 B 60 107 110 2.0 C 60 110 130 3.0 A 80 130 148 1.0 B 80 114 120 1.0 C 80 116 136 2.8 EXAMPLE II
Alloys A and C, processed as in Example I, in the 0% cold rolled, 40% cold rolled, 60% cold rolled and 80% cold rolled ; conditions, were sub~ected to stabilizatlon (stress relief) anneal~ at about 320C for 1 hour. The 90 bend properties .

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for these stabillzed materials were then measured. The resulting data presented in Table II below were based on plots of 0.2% offset yield strength versus the ratio o~ bend radius to thickness (R/t) so that the bend propertles could be easlly compared at an equivalent 0.2% yield s~rength. For comparison purposes the bend data was determined ~rom published data for Alloy B and CDA Alloy 688 tAlloy D - having the composition 22.7% zinc, 3.5% aluminum, 0.38% cobalt, balance essentially copper) and are included in Table II.
The bend properties determine the minimum radius about which strip could be bent without cracking either parallel to or perpendicular to the rolling direction. The longitudinal properties refer to the axls perpendicular to the rolling direction (goodway) and the transverse propertles refer to the axis parallel to the rolling direction (badwa~). R is the smallest radius which does not crack and t is the thickness o~
the strip, i.e., all at 0.020" gage. It is significant that the present in~ention o~ers better goodway bend properties than commercial CDA Alloys 638 and 688 and better badway bend properties than commercial CDA Alloys 510 and 638. It is - particularly significant that the alloy of the present invention has adequate ductility at stren~th levels the other alloys cannot obtain. These properties are particularly significant in the electrical connectors o~ the present invention.

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TABLE II
BEND PROPERTIES
Alloy 0.2% Yield Strength Longitw~nal ~sverse (ksi) t t A 80 0.3 1.1 B 80 ~3 1.5 C 80 0.7 2.0 D 80 0.8 0.9 }0 A 100 1.3 3.8 B 100 1.0 5.2 C 100 ~.9 5.2 ; D 100 2.2 2.1 A 110 2.2 6.
B 110 1.8 9.0 C 110 2.3 10.0 D 110 2.1 3-3 A 120 2.2 14 EXAMPLE III
Copper base alloys used in the connectors of the present inventlon containlng silicon, tin and iron ~ere chill cast as 10 lb. lngots as in Example I. They were processed as in Example I and annealed to provide metal at 0.030" gage in the 50% cold rolled temper as ~ollows: hot roll from 750C to 0.375" gage with a ~inishing temperature above 400C; cold roll below 200C to 0.120" gaæe; anneal at 450C for 1 hour;
cold roll to o.o60~ gage below 200C; anneal at 450C for 1 hour; and cold roll 50% to 0.030" gage at below 200C. The alloys were stress corrosion tested in moist ammonia in the ~ollowing manner. The amount o~ springback af~er removal ~rom a test Jig was measured versus exposure time with U-bend shaped specimens. In this test the stress corrosion parameter of most interest is the time for 80% springback. The higher the value of thia parameter, the more resistant the alloy to stress corrosion in the particular environment. The stress '~

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lt)SS~iS4 corrosion data and the transverse tensile properties are shown in ~able III below. For comparison, simllar data are shown for commerclal CDA Alloy 510 (Alloy B) and commercial C~A Alloy 638 (Alloy C). These da~a clearly show the excellent stress corrosion resistance obtained in accordance with the present invention. It can be clearly seen that tin alone, as in commercial CDA Alloy S10, does not provide the desired resistance to stress corrosion. Furthermore, silicon ln combination with another element such as aluminum, does not yield the excellent resistance to stress corrosion as does the present invention. Therefore, it is most ~urprising that the silicon and tin combination in accordance with the present invention provides such excellent stress corrosion reslstance.

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I~ this example additional data was obtained showing properties Por a variety o~ material~. Alloys A, B, C, and D
are as indicated hereinabov~. Alloys E, F, G~ H~ and I have the composition set forth in Table IV-A below. Alloys A and E through I were processed in a manner a~ter Examples I and II
as set out below: hot roll from 750C to 0.375" gage with a ~inlshing temperature above 400C; cold roll to 0.120" gage at below 200C; anneal at 450C for 1 hour, cold roll 67% to 0.040" gage at below 200C; a~neal at 450C for 1 hour; and cold roll 50% to 0.020" gage at below 200C, The resultant tensile and bend properties are shown in Table IV-B and Table IV-C below. For comparison purposes similar data is shown for Alloys B, C, and D.
TA~LE IV-A - COMPOSITION
AlloySilicon % Tin % Cobalt % Iron %
E 3.0 2-5 1.5 F 1.5 4 - -G 2.0 4 - -H 2.0 3.5 I 2.0 3.5 - 1.5 TABLE IV-B - TENSILE PROPERTIES
Ultimate 0.2 % Yield Tensile - % Cold Strength Streng~h Elongatlon ~ Reduction (ksi) (ksi) (~) !;
' A 50 120 137 1.5 , B 50 101 103 3.0 ` C 50 105 126 4,0 .~ 30 D 50 116 128 2.0 E 5 120 137 1.5 F 50 106 114 6.6 , G 50 110 123 2.5 ; H 5 107 120 2.0 I 50 120 133 2.5 . .
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0.2% Yield Strength LongitudinalTransver3e Alloy (ksi) R/t R~t A 100 1.3 3.8 B 100 1.0 5.2 C 100 1.9 5.2 D 100 2.2 2.1 E 100 1.2 4.6 F 100 1.2 5.0 G 100 1.6 4.7 H 100 0.8 3.8 I 100 1.2 3.0 The foregolng data clearly hows that the alloyæ used in ; the connectors o~ the present invention have higher yield .
strength than Alloys B and C for equivalent cold reduction.
.Specifically referring to Table IV-C, the bend data shows that the alloys o~ the present invention have better longitudlnal (goodway) bend properties at comparable yield strength than the comparative alloys excluding Alloy B, and ha~e better transverse (badway) bend properties than the comparative alloy~
excluding Alloy D.
EXAMPLE V
This example compares the stress relaxation resistance of the alloy used in the electrlcal connector of the present ` lnvention, Alloy H above, to commercial CDA Alloy 510 (Alloy .
B) and commercial CDA Alloy 638 (Alloy C). Each alloy was processed to provide a material in a hard temper (~dentified .:
;- as condition X) and a heat treated temper (identified as condltion Y). The hard tempers were obtained by cold rolling the amounts speci~ied ln the table and the heat treated ~i tempers were obtained by heat treating the hard or X material .. . ~ .
a specifled amount for a speclfied period of time as set forth in the table.

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T LE V
MECHAN~CAL PROPERTIES OF THE METAL
~ESTED IN El`END STRESS RELAXA'rION
Alloy Temper 0.2~ YS UTS Longitudinal T~erse _ ksi ksi RJt R/t B X tCR 37%) 84 87 1.6 2.7 B Y ~200C - 1 Hr.) 78 87 1.2 2.3 B X (CR 56%) 103 106 2.8 ~.2 B Y (200~C - 1 Hr.)97 102 3.1 6.2 B X (CR 75%) 114 120 3.8~12.5 B y (200C - 1 Hr.) 112 117 2.3~12.5 C X (CR 13%) 67 88 >0.2 0.4 C Y t315C - 1 Hr.) 68 89 ~0.2 0.4 C X (CR 31%) 92 109 1.2 2.9 C Y (315C - 1 ~r.) 91 108 2.0 2.8 C X (CR 40%) 99 116 1.6 4.9 C Y (300C - 1 Hr.) 96 114 2.0 6.5 H X (CR 37%) 103 120 2.0 4.1 H Y (25~C - 1 Hr.) 112 120 1.5 6.1 H X (C~ 60%) 112 130 2.7 8.6 H Y (250C - 1 ~r.) 121 131 2.7 17.0 ~, The samples prepared in Table V were tested to determine stress relaxation resistance. ~he test invol~ed mounting a strip sample so that a plurality of points acts on the sample to bend the sample with a predetermined force in order to provide a stress on the sample equal to 80% o~ the 0.2% o~fset yield ~trength. As the sample stress relaxes the load or force applied to the sample, drops wlth time~(in this partlcular test o~er a period of 15 minutes) indicating the ~ 30 ~tress relaxation property in the sam~le. Results are shown``~
i ln Figure 4 which plots the stress remaining in ksi versus the -~ minimum badway bend radius in the cold rolled condition to represent formability. This shows the`combination o~ stress relaxation resistance in the heat treated condition (post forming) expressed in terms of stress remaining after 15 -: , ~) !35654 :
minutes plotted against badway bends in a cold rolled condition. Thls expresses the key combination o~ properties desired by a designer of electrical connectors as described above and clearly shows the signi~icant advantages of the connectors of the present invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A high strength copper base alloy electrical connector or contacting spring having good stress corrosion resistance, stress relaxation resistance and good strength to bend ductility having a composition consisting essentially of from 1.0 to 4.5% silicon, from 1.0 to 5.0% tin, with the minimum silicon plus tin content being 3.5%, balance copper, said connector having a portion for mating engagement with a second electrical connector or terminal so that said portion is placed under stress during said mating engagement with said second electrical connector.

2. A connector according to Claim 1 wherein said connector is a strip material having at least one bent portion.

3. A connector according to Claim 2 wherein said copper base alloy includes a first additive selected from the group consisting of from 0.01 to 2.0% iron, from 0.01 to 2.0%
cobalt, and mixtures thereof, with a maximum total iron plus cobalt content of 3.0%.

4. A connector according to Claim 2 including a second additive selected from the group consisting of nickel from 0.01 to 5.0%; manganese from 0.01 to 5.0%; titanium from 0.01 to 5.0%; zirconium from 0.01 to 5.0%; hafnium from 0.01 to 5.0%, chromium from 0.01 to 2.0%; beryllium from 0.01 to 3.0%;
vanadium from 0.01 to 5.0%; and magnesium from 0.01 to 2.0%;
and mixtures thereof, wherein the total content of said second additive is less than 10.0%.

5. A connector according to Claim 3 including a second additive selected from the group consisting of nickel from 0.01 to 5.0%; manganese from 0.01 to 5.0%; titanium from 0.01 to 5.0%; zirconium from 0.01 to 5.0%, hafnium from 0.01 to 5.0%; chromium from 0.01 to 2.0%; beryllium from 0.01 to 3.0%;
vanadium from 0.01 to 5.0%; and magnesium from 0.01 to 2.0%;
and mixtures thereof, wherein the total content of said first additive plus said second additive is less than 10.0%.

6. A connector according to Claim 4 wherein said contact is characterized by a fine uniform precipitate of said second additive dispersed throughout the matrix.

7. A connector according to Claim 5 wherein said contact is characterized by a fine uniform precipitation of said second additive dispersed throughout the matrix.

8. A connector according to Claim 2 containing a third additive selected from the group consisting from 0.01 to 3.0%
arsenic, from 0.01 to 3.0% antimony, from 0.01 to 3.0%
aluminum, from 0.01 to 3.0% zinc and mixtures thereof, wherein said third additive is present in a maximum total of less than 5.0%.

9. A connector according to Claim 2 having a grain size less than 0.060 mm.