DE3535926A1 - MICRO CIRCUIT BUTTON WITH ADAPTED IMPEDANCE - Google Patents

Description

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STREET & RAIN _

Patent Attorneys - European Patent Attorney «YYYYY / D

Tektronix, Inc. Munich, October 8, 1985

Beaverton, Oregon 97077 (V.St.A.) ka-de 14 928

Microcircuit push-button with adapted impedance

The present invention relates to devices for measuring electrical circuits, and more particularly to probes or button for making a direct short-term contact with selected points of a microcircuit.

Microcircuit pushbuttons are used to temporarily between test facility and selected points, usually Solder joints to be electrically connected in integrated switching devices (IC). A microcircuit button should make good electrical contact without placing excessive pressure on the IC device will. The button should also go from the soldering point of the microcircuit to the connection point of the button with the Measuring arrangement represent a current path with a constant characteristic impedance, in particular when measuring IC devices in the microwave frequency range. Any Discontinuity can cause unwanted signal reflections Points of this discontinuity result in what is inaccurate Measurements.

The problem of a good electrical contact between the button and the microcircuit solder joint has been a problem up to now solved by attaching a short spring wire to the probe tip to make actual contact with the Allow solder joint. This procedure is often used when a button has more than one contact to the Should produce microcircuit, especially if the solder joints to be tested at different heights lie. The spring wires make good contact too

all soldering points, while their spring properties prevent the pushbutton from applying excessive pressure exercises any solder joint. Unfortunately that is Wave resistance of a spring wire is usually perfect different from the characteristic impedance of the rest of the pushbutton signal path and undesirable reflections can result at higher frequencies.

A probe is therefore required that has a current path with constant wave resistance over the entire length of the Push button from the connection point to the external test arrangement to a point as close as possible to the microcircuit test point having. The push button should also have good electrical contact when exercising a restricted Maintain contact pressure.

According to a preferred embodiment of the invention a microcircuit button is shown, the one Has waveguide with constant power resistance, the waveguide at one end by a resilient supported contact tip and terminated at the other end by a device that connects the waveguide with the external test arrangement connects. According to one aspect of the invention, the button has a coaxial waveguide with constant wave impedance on, with an inner conductor and an outer conductor, which are separated by dielectric material. At the end of Push-button are the outer conductor and the dielectric material over the inner conductor, so that a results in a cylindrical space in the middle of the probe tip, with a diameter equal to that of the inner conductor. A conductive coil spring with the same Outside diameter like that of the inner conductor essentially takes up the cylindrical space at the tip of the Button. One end of the spiral spring is connected to the end of the inner conductor, while the other end of the spring

is attached to a contact tip, the diameter of which is equal to the diameter of the inner conductor. The contact tip is so slidable in the cylindrical space The tip of the stylus added that the end of the tip slightly above the end of the dielectric Material and the outer conductor survives.

The contact tip comes to the soldering point of a microcircuit in contact, then the spring is compressed and prevents excessive deformation of the Solder joint or the contact tip, while still making good electrical contact between the tip and the Solder joint is present. Since the spiral spring and the contact tip have the same diameter as the Inner conductor is the characteristic impedance, i.e. the characteristic impedance of the push button transmission line via the Length of the button almost to the end of the contact tip constant.

In another embodiment of the present Invention, the button has flat microstrip conductors on, which is at the bottom of a triangular shape tapered sheet of resilient dielectric Substrate material are applied. The substrate sheet is on the underside of a tapered wire retainer mounted so that the microstrip conductors form waveguides which support the support member as a ground plane use. The microstrips end with contact tips at the tapered tip of the button. If the contact tips with soldering points of a microcircuit in Make contact, then presses the resilient dielectric Material between the microstrip and the support member together and prevents excessive deformation of the contact pins or the soldering points and allows Variations in the height of the solder joints or connection points.

The invention therefore solves the problem of specifying new and improved microcircuit buttons that are practical have a constant wave resistance over their entire length.

Furthermore, the new and improved Mi kroschaltungs-button a resilient mechanical contact to selected Establish points of a microcircuit while the contact pressure exerted on such point remains limited.

The new and improved microcircuit push-buttons should also be used be able to simultaneous electrical Make contact with a plurality of selected points on a microcircuit, such points in different heights on the surface of the microcircuit can be applied.

The subject matter of the present invention is also derived from the preceding claims. The structure and the mode of operation of the pushbutton according to the invention as well as further details, features and advantages result from the following description based on the drawing, the same reference numbers denoting the same elements.

In the drawing show:

Fig. 1 is a perspective view of a preferred embodiment of the microcircuit push button according to the invention,
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Fig. 2 is a section through the microcircuit push button Fig. 1,

Fig. 3 is a plan view of the underside of another embodiment of the Mi kroschaltung button according to the invention,

FIG. 4 is a front view of the microcircuit push button of FIG Fi g. 3 and

Fig. 5 is a section through the other embodiment of the Microcircuit push button of FIG. 3.

Fig. 1 illustrates in perspective a one according to the invention Microcircuit push-button, while Fig. 2 shows the push-button Fig. 1 shows in sectional view. A button 10 has a coaxial waveguide 12 with an outer conductor 14 and an inner conductor 16, which by dielectric Material 18 are separated. At the tip 20 of the button 10 is the outer conductor 14 and the dielectric Material 18 over the end 22 of the inner conductor 16 over, so that there is a cylindrical space 36 in the Center of the dielectric material 18 is formed and has a diameter which corresponds to the outer diameter of the inner conductor 16.

A spiral spring 24 is mounted in the space 36, with the upper end 26 at the end 22 of the inner conductor 16 attached. The spring 24 is made of conductive material and has an outer diameter that is substantially is equal to the outer diameter of the inner conductor 16.

The lower end 28 of the spring 24 is provided with a cylindrical extension 30 of reduced diameter Tip 32 connected and surrounds this tip, which is attached to the end of the space 36. The approach 30 has one Diameter which is substantially equal to the inner diameter of the spring 24, so that the spring 24 has the approach 30 firmly gripped. The tip 32 is also made of conductive material and has a cylindrical shape lower section 34, which is almost the same diameter

like the inner conductor 16, so that it fits into the space 36 with a sliding fit. The pin 32 is at the lower end 38 pointed, so that a selective electrical contact, for example with a small fastening or Soldering point 40 of a microcircuit device 42 is possible is.

The button 10 is suitable via a coupling 46 Having connector parts 48 and 50, with a coaxial cable 44 connected. The coaxial cable 44, which has an inner conductor 52 and an outer conductor 54, through dielectric material 56 are separated and that of a jacket 58 is surrounded, can at a distal end, not shown, to a test arrangement by means of a suitable connector.

The button 10 has the same physical training of the inner and outer conductors, such as the coaxial cable 44 from Pushbutton end in connector 46 to end 22 of inner conductor 16 and thus pushbutton 10 has the same Characteristic impedance as the cable 44 from the connector 46 to the Conductor end 22. Since the connector 46 is such that between the button and the cable 44 a connection with constant wave resistance is maintained, the signal path extends with constant wave impedance from the test arrangement to the end 22 of the Inner conductor 16.

The spring 24 and the pin 32, which function as an inner conductor and have the same outer diameter like that of the conductor 16, together with a continuation of the outer conductor 14 and the dielectric 18 at the probe tip 20, the spatial relationships of inner and outer conductors are set from the end 22 of the Conductor 16 continues through the end of tip 20 near lower portion 34 of post 32 where the

Outer conductor 14 at least part of the length of the lower Section 34 surrounds, especially when the spring 24 is compressed. Thus the signal path is with constant wave resistance of the button 10 to almost Solder 40 of the device 42 expanded.

When lowering the button 10, the pin 32 comes with the Solder 40 in contact, whereby the spring 24 is compressed, so that an undesirable deformation of the Solder 40 or pin 32 is prevented while there is enough pressure between solder 40 and pin 32 is present to make good electrical contact. The spring 24 is tightly wound so that it resembles a full-time leader as closely as possible. However, there is enough space between the turns for a sufficient one Pressing together while the button is in use.

Is a connection between the outer conductor 14 and a second solder joint 64 on the microcircuit device 42, then the button 10 can also have a conductive sleeve 60 which slides over the outer conductor 14 at the tip 20 of the button 10 fits. A second Coil spring 68 is around conductor 14 between a stop 66 on conductor 14 and the upper end of sleeve 60 placed to push it down. A pointed stylus pin 62 on the outer conductor extends slightly over the tip 20 of the button 10 and is attached to the lower periphery of the sleeve 60 so that when lowering the Button 10 of the pin 62 with a soldering point 64 in contact comes. The spring 68 is compressed and limits the contact pressure between the pin 22 and the solder joint 64. Since the sleeve 60, the spring 68 and the stop 66 lie outside the outer conductor 14, they influence Elements the wave resistance of the probe waveguide only in a negligible way.

3, 4 and 5 show an alternative embodiment of the device according to the invention with a Microcircuit button 11, the microstrip signal conductor 13, which are attached to the underside of a tapered plate 15, as specifically shown in FIG. 3 shows. The plate 15 is made of resilient dielectric Material that expediently comprises silicone rubber. The dielectric plate 15 is along the bottom a conductive support member 25 is attached. The holding member 25, which is expediently made of steel, has Connector parts 27 at one end for receiving connector parts 29 at the ends of the coaxial cables 31, the lead to the test arrangement, not shown. A conductor stub 33 which runs through the plate 15 is with a Microstrip 13 soldered or glued and connects an inner conductor 35 of the coaxial cable 31 with a microstrip conductor 13. An outer conductor 37 of the coaxial cable 31 is electrically connected to the holding member 25 via connector parts 27 and 29.

The holding member 25 acts as a base plate and forms together with the Signal1 egg tern 13 three waveguides to Conducting signals between contact pins 23 attached to conductors 13 at the tip of button 11 are, and a plurality of conductor stubs 33. The thickness of the plate 15 and the widths of the conductors 13 are selected so that the three waveguides have the same wave impedance like the coaxial cables 31 have. So that through the connector parts 27 and 29 a continuous continuation the wave resistance results, the nozzle 33 have the same diameter as the inner conductor 35 of the cables 31 and the inner diameter of the connector parts 27 and 29 are equal to the inner diameter of the outer conductor 37 of the

Cable 31. The characteristic impedance of each cable 31 thus continues through connector parts 29 and 27 to plate 15 and along the length of conductors 13 from stubs 33 to pins 23.
05

FIGS. 4 and 5 show the button 11 with the tips 23 in engagement with soldering points 39 of the microcircuit 41. When When the pins 23 are lowered onto the soldering points 39, the resilient dielectric material 13, which acts as a spring, is pressed together, whereby the contact pressure between the tips 23 and the soldering points 39 is limited, so that a excessive deformation of the tips and soldering points is prevented and a pin contact with all soldering points is given, even if some of the soldering points differ from others in height.

It should be noted that although in the embodiment according to Fig. 3 three conductors 13 with tips 23 are used in substantial alignment with one another. At a alternative embodiment can, however, more or less conductor 13 in a suitable shape on the plate 15 be provided so that there is a number and positioning of contact tips 23 as required are, so that a corresponding contact to an acceptable number and arrangement of solder points 39 on a Microcircuit device 41 can be manufactured.

According to the preferred and alternative embodiments the present invention thus results in a microcircuit pushbutton with at least one waveguide with constant wave resistance from the connection point of an external Signal1 conductor with a spring-loaded Pen at the tip of the button, the pen making resilient contact with a selected point on a device to be tested.

Claims (1)

Claims π.) button 'for coupling an electrical test arrangement with a chosen point in an electrical facility, marked by
a spring-loaded pin (32) for contacting the selected point and a waveguide (12) with substantially constant Characteristic impedance for coupling the test arrangement with the pen (32). 2. button according to claim 1, characterized, that the pin 32 is supported by a spring (24) is. 3. button according to claim 2, characterized, that the spring (24) is part of the waveguide (12). 4. button according to claim 1,
characterized, that the resilient mounting of the pin (32) by a resilient dielectric substrate takes place. 5. button according to claim 4,
characterized, that the substrate is part of the waveguide (12). 6. Button according to one of claims 1 to 5,
characterized, that the waveguide is a coaxial waveguide, with an inner conductor coupled to the pin (32) (16) and an outer conductor (14) at least partially surrounding the pin (32). 7. button according to claim 6, characterized,
that the inner conductor (16) has a spiral spring (24) for resilient support of the pin (32). 8. button according to claim 7, characterized,
that the pin (32) has essentially the same outer diameter as the spiral spring (24), so that the pin (32) forms part of the inner conductor (15) of the waveguide (12). 9. button according to one of claims 1 to 5, characterized, that the waveguide is a coaxial waveguide (12), with an outer conductor (14), which with the pin (32) is coupled. 10. button according to claim 9, characterized,
that a conductive sleeve (60) is provided on the outer conductor (14) to which the pin (62) is attached and that a spring (68) between the outer conductor (12, 66) and the sleeve (60) is arranged. Tl. Button according to one of the preceding claims,
characterized,
that a first resilient pin (32) contact a first point of the circuit and a second resilient pin (62) contact a second point of the circuit and that a coaxial waveguide (12) is coupled with its inner conductor (16) to the first pin (32) and with its outer conductor (14) to the second pin (62).
05 12. Button for coupling an electrical test arrangement with a chosen point in an electrical facility, marked by: a first conductor (25), a plate (15) of resilient dielectric Substrate, a second mounted on the substrate (15) Conductor (13), the first and second conductors forming a waveguide, a pin (23) for contacting the selected point, the pin (23) at one end of the second conductor (13) is attached and the substrate (15) deforms when the pin (23) contacts the selected point, and a device for coupling the waveguide with the test arrangement. 13. Button according to claim 12, characterized, that the waveguide has a substantially constant wave resistance over its entire length. 14. Button according to claim 12 or 13, marked by: a holding member (25) on which the substrate plate (15) is applied, so that when contacting the selected point by the pin (23), the substrate plate (15) between the holding member (25) and the second conductor (13) is compressed. 15. Button according to claim 14, characterized,
that the first conductor is the holding member (25) and the second conductor (13) forms the waveguide with the holding member (25). 16. Button according to one of claims 3 to 15,
characterized, that for contacting several selected points in the electrical circuit several second conductors (13) the resilient dielectric substrate plate (15) are arranged and with the holding member (25) form a plurality of waveguides, with one At the end of each conductor (13) a tip (23) is arranged.