Abstract
A plug-in connector has a press-in body which is coated with a first Ni-containing layer and a second Ni-containing layer. The first and/or the second Ni-containing layer is a nanocrystalline or amorphous layer. The first Ni-containing layer and the second Ni-containing layer have grain sizes of different orders of magnitude. In particular, one of the layers can be microcrystalline and the other can be nanocrystalline or amorphous.
Claims
1. A plug-in connector, comprising: a press-in body; a first Ni-containing layer coating said press-in body; and a second Ni-containing layer coating said press-in body, at least one of said first Ni-containing layer or said second Ni-containing layer is a nanocrystalline layer or an amorphous layer.
2. The plug-in connector according to claim 1, wherein one of said first and second Ni-containing layers is a matt nickel and another of said first and second Ni-containing layers is a bright nickel.
3. The plug-in connector according to claim 1, wherein said first Ni-containing layer or said second Ni-containing layer is said amorphous layer which contains up to 15% by weight of phosphorus.
4. The plug-in connector according to claim 1, wherein at least one of said nanocrystalline layer or said amorphous layer has a thickness of 0.1-3 m.
5. The plug-in connector according to claim 1, further comprising a third Ni-containing layer disposed on top of said second Ni-containing layer.
6. The plug-in connector according to claim 5 wherein said second Ni-containing layer is microcrystalline and said third Ni-containing layer is said nanocrystalline or said amorphous.
7. The plug-in connector according to claim 1, wherein said press-in body is formed of a material selected from the group consisting of copper, a copper alloy and steel.
8. The plug-in connector according to claim 7, wherein said copper alloy is an alloy composed of CuFe, FuFe.sub.2P, CuNiSn, CuNiSi, CuZn, CuSnZn, CuSn.sub.4, CuSn.sub.6 or CuSn.sub.8.
9. The plug-in connector according to claim 1, further comprising an intermediate layer composed of Cu or Sn and disposed between said press-in body and said first Ni-containing layer.
10. The plug-in connector according to claim 1, wherein said first Ni-containing layer or said second Ni-containing layer is said amorphous layer which contains up to 10% by weight of phosphorus.
11. The plug-in connector according to claim 1, wherein at least one of said nanocrystalline layer or said amorphous layer has a thickness of 0.1-2.2 m.
12. The plug-in connector according to claim 1, wherein at least one of said nanocrystalline layer or said amorphous layer has a thickness of 0.1-1 m.
13. The plug-in connector according to claim 1, wherein at least one of said nanocrystalline layer or said amorphous layer has a thickness of 0.1-0.7 m.
14. The plug-in connector according to claim 1, wherein at least one of said nanocrystalline layer or said amorphous layer has a thickness of 0.1-0.3 m.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0017] FIG. 1 is an illustration of a plug-in connector according to the invention;
[0018] FIG. 2 is a diagrammatic, sectional view of a coating sequence of the plug-in connector of FIG. 1;
[0019] FIG. 3 is a sectional view of a second working example of a layer sequence of the coating of the plug-in connector;
[0020] FIG. 4 is a sectional view of a third working example of the coating sequence of a plug-in connector;
[0021] FIG. 5 is a sectional view of a fourth working example of a coating of a plug-in connector;
[0022] FIG. 6 is a graph showing a friction test;
[0023] FIG. 7 is a further graph of the friction test;
[0024] FIG. 8 is a schematic depiction of a transmission electron micrograph of a cross section of a bright nickel surface; and
[0025] FIG. 9 is a schematic depiction of a transmission electron micrograph of a cross section of an amorphous NiP surface.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a plug-in connector 1 which is suitable for pressing into an opening of a circuit board which is made of copper and is coated with bronze and/or tin. The plug-in connector 1 contains a pin tip 10, a press-in body 2 having a press-in region 11 and a fastening region 12. The plug-in connector 1 is coated with two Ni-containing layers which are at least partly superposed. A cylindrical section of the press-in region 11 serves as contact area.
[0027] FIG. 2 shows a first working example of the layer structure of the plug-in connector 1. The press-in body 2 is made of CuSn.sub.6 and has a roughness Ra=0.5 m. A first Ni-containing layer 3 having an average grain size of 0.8 m is arranged on top of this. The final surface is formed by a nanocrystalline second Ni-containing layer 4 which has an average grain size of 30 nm. The second Ni-containing layer 4 having a nanocrystalline grain size increases the surface hardness, which at a grain size of 30 nm has an E modulus of 205+/7 GPa and an indentation hardness of 9.4+/0.6 GPa. The nanocrystalline microstructure of the second Ni-containing layer 4 produces a smoother surface which has improved sliding properties. Such a layer sequence is particularly suitable for a one-off plug-in operation.
[0028] FIG. 3 shows a further working example of a layer structure of a plug-in connector. The layer structure has an intermediate layer 5 between the press-in body 2 and the first Ni-containing layer 3. The intermediate layer 5 consists of tin. It serves as a bonding layer and also for evening out the roughness of the press-in body 2. The intermediate layer is a nanocrystalline layer having a grain size of 30 nm. As an alternative, the intermediate layer 5 can also consist of copper.
[0029] FIG. 4 shows a third working example of a layer structure on a press-in body 2 having three Ni-containing layers, where the first Ni-containing layer 3 is a nanocrystalline layer, the second Ni-containing layer 4 is a microcrystalline layer and the third Ni-containing layer 6 is an amorphous layer. The amorphous layer contains 12% by weight of phosphorus. Such an NiP layer has an E modulus of 149+1-6 GPa and an indentation hardness of 9+1-0.7 GPa. The surface of the amorphous layer has a constant low frictional resistance against a copper contact surface. Cold welding against a copper or bronze layer can be minimized or prevented by means of such a layer structure. The amorphous layer has increased stability against frictional oxidation and low layer degradation, so that it is also well-suited to repeated plugging-in operations.
[0030] FIG. 5 shows a layer structure on a press-in body 2 having three Ni-containing layers and also an intermediate layer 5. The three Ni-containing layers 3, 4, 6 correspond to those of the working example shown in FIG. 4. The intermediate layer 5 consists of tin.
[0031] FIG. 6 shows the result of two friction tests between a copper pin and a plate coated with a matt nickel or a bright nickel, respectively. The time is plotted on the horizontal axis, and the coefficient of friction (COF) is plotted on the vertical axis. The curve for the bright nickel shows a running-in phase in which the coefficient of friction increases during the friction test, while the coefficient of friction has an approximately constant value in the friction test on matt nickel.
[0032] FIG. 7 is a graph and shows a comparison of a further friction test between a copper pin and a plate coated with bright nickel or an amorphous NiP layer. The friction tests on the amorphous NiP layer show a constant low coefficient of friction, while the friction test on the bright nickel displays an increasing coefficient of friction. After 10 friction cycles, a transfer of Cu particles, as can be seen in the schematic depiction of the microscopic examination in FIG. 8, occurs in the case of bright nickel. In the case of an amorphous NiP layer, no transfer of material to the friction surface, as is shown in FIG. 9, was observed after 10 friction cycles.
[0033] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0034] 1 Plug-in contact [0035] 2 Press-in body [0036] 3 First Ni-containing layer [0037] 4 Second Ni-containing layer [0038] 5 Intermediate layer [0039] 6 Third Ni-containing layer [0040] 10 Pin tip [0041] 11 Press-in region [0042] 12 Fastening region
