BACKGROUND

[0001] Testing of manufactured products, such as electronic assemblies, often requires a measure of the engagement force exerted on the unit under test (UUT). For instance, the UUT may be connected to automatic or manual testing equipment that applies and measures the engagement force during testing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 illustrates a front view of an example force-sensing system of the present disclosure;

[0003] FIG. 2 illustrates a flowchart of an exemplary method for sensing an incrementally increasing engagement force applied between a unit under test and a force-sensing system;

[0004] FIG. 3 illustrates a front view of one half of the system of FIG. 1 when compressed by an engagement force;

[0005] FIG. 4 illustrates a front view of another example force-sensing system of the present disclosure;

[0006] FIG. 5 is a bottom view of the body illustrated in FIG. 4;

[0007] FIG. 6 illustrates a front view of one example of a balancing member added to the system of FIG. 4; and

[0008] FIG. 7 depicts a high-level block diagram of a computer that can be transformed into a machine that is dedicated to perform the functions described herein.

DETAILED DESCRIPTION

[0009] The present disclosure broadly discloses an electro-mechanical force- sensing switch. Testing of manufactured products, such as electronic assemblies, often requires a measure of the engagement force exerted on the unit under test (UUT). However, it may be difficult to create an incrementally increasing engagement force between the UUT and a set of test probes, while simultaneously measuring and reporting the engagement force. In some cases, it may also be difficult to see the tips of the small test probes, or to adjust their locations for the purposes of adjusting the differential impedance.

[0010] Examples of the present disclosure provide a novel electromechanical force-sensing switch. For instance, examples of the present disclosure include a body formed from a material that is electrically non- conductive and mechanically compliant, i.e., able to recover its original dimensions after being compressed. In one example, the body is formed from a ceramic meta-material. One or more electro-mechanical switches are embedded in the body. In one example, each switch includes a pair of test probes. The test probes are spaced apart relative to each other, so that they do not make contact when the body is uncompressed. However, sufficient compression of the body will cause the test probes to make contact. A plurality of similar switches may be embedded along the length of the body, such that the amount of pressure applied to the body can be measured by the number of switches that are activated, i.e., the number of test probe pairs that make contact. This allows incrementally increasing engagement force between a unit under test (UUT) circuit and the test probes to be simultaneously exerted and measured.

[0011 ] Examples of the present disclosure make use of ceramic meta- materials. M eta-materials comprise three-dimensional, lattice-like arrays of interconnecting filaments having large voids between the filaments. When fabricated out of ceramics, meta-materials tend to have sponge-like properties, i.e., they are able to recover their original dimensions after being compressed to substantially smaller dimensions. Ceramic meta-materials are also electrically non-conductive.

[0012] FIG. 1 illustrates a front view of an example force-sensing system 100 of the present disclosure. In one example, the system 100 is implemented as a differential probe. In this example, the system 100 includes a body 102 connected to a printed circuit assembly (PCA) 104. The PCA 104 may be further connected to higher level instruments 1 10 such as oscilloscopes or other computing devices. [0013] In one example, the body 102 is formed in two pieces 102i and 102 ₂ that are mirror images of each other. The body 102 is formed from a mechanically compliant, electrically non-conductive material. For instance, in one example, the body 102 is formed from a ceramic meta-material. In one example, each piece 102! and 102 ₂ of the body 102 has a tapered shape, i.e., a first end of the piece is wider than a second end of the piece.

[0014] Each piece 102i and 102 ₂ of the body 102 also includes a test probe

106 ₁ or 106 ₂ (hereinafter "test probes 106") that comprises one half of a differential probe set. In one example, the test probe 106i or 106 ₂ is inserted into the second, narrower end of the piece 102i or 102 ₂ . For instance, the test probe 106i or 106 ₂ may be inserted such that the sharp end of the probe is embedded in the piece 102i and 102 ₂ , while the head of the test probe 106i or

106 ₂ visibly protrudes from the piece 102i and 102 ₂ . The test probes 106 could be of any style; however, in one example, the sharp ends of the test probes 106 have a "dog leg" or "side-stepped" shape that improves visibility of the heads. In a further example, the sharp ends of the test probes 106 include barbs or ribs that retain the test probes 106 in the body 102 and prevent the test probes 106 from rotating within the body 102. The user can define the distance between the test probes 106i and 106 ₂ by manually varying the distance between the pieces 102i and 102 ₂ of the body 102 and/or manually varying the positions of the test probes 106i and 106 ₂ in the pieces 102i and 102 ₂ . In one example, the test probes are formed of a glassy or amorphous metal. Amorphous metals include solid metallic materials, such as metal alloys, with a disordered atomic- scale structure. Whereas most metals are crystalline in their solid states, amorphous metals are non-crystalline and have glass-like structures. Some specific examples of amorphous metals from which the test probes may be formed include alloys of zirconium, palladium, iron, titanium, cooper, and magnesium.

[0015] One or more electro-mechanical switches 108r108 _n , hereinafter collectively referred to as "switches 108," are also embedded in the body 102. In one example, each switch 108 comprises a pair of differential test probes, which for the purposes of differentiation from the test probes 106 are hereinafter referred to as "ambient probes." In this case, the ambient probes probe nothing other than the ambient air when they are not engaged to the UUT. The ambient probes in each pair are positioned in a spaced-apart relation, i.e., with some user-definable distance separating the ambient probes when the body 102 is uncompressed. In one example, the ambient probes are formed of a glassy or amorphous metal.

[0016] Each test probe 106i and 106 ₂ and each switch 108 is connected to the PCA 104, e.g., via a wire that is soldered or crimped to the sensing elements of the probes. In the example where each switch 108 comprises a pair of ambient probes, one probe in each pair of ambient probes is connected to a pull up resistor to a direct current (DC) power supply voltage, while the other probe in the pair of ambient probes is connected to ground. FIG. 1 illustrates the PCA connections for the test probe 106i and the switches 108 embedded in only one piece 102i of the body 102; however, the test probe 106 ₂ and the switches 108 embedded in the other piece 102 ₂ of the body are connected to the same PCA 104 in a similar manner. In this manner, the PCA 104 is capable of receiving test signals from the test probes 106 and the switches 108. In one example, the PCA may also amplify these test signals before passing them on to higher-level instruments 1 10, e.g., other computing devices.

[0017] FIG. 2 illustrates a flowchart of an exemplary method 200 for sensing an incrementally increasing engagement force applied between a unit under test and a force-sensing system. For instance, the method 200 may be performed by higher level testing equipment 1 10 connected to a system configured substantially as illustrated in FIG. 1 . Thus, reference is made in the discussion of the method 200 to various elements of the system 100 illustrated in FIG. 1 .

[0018] At block 202, the method 200 begins. At block 204, a processor of the testing equipment receives signals from the PCA 104 indicating that one or more of the switches 108 embedded in the system 100 have closed. When an engagement force is applied to the system 100 at the test point, i.e., near where the test probes 106 are positioned, the engagement force will cause the body 102 to compress, as illustrated in FIG. 3. In particular, FIG. 3 illustrates a front view of one half of the system 100 of FIG. 1 when compressed by an engagement force. As illustrated, compression of the body 102 may cause one or more pairs of ambient probes to make contact with each other, thereby closing one or more of the force-sensing switches 108. In the example illustrated in FIG. 3, the engagement force is enough to cause the switch 108 ₂ to close, but not enough to cause the switch 108i to close. In one example, when a switch 108 is open, i.e., the ambient probes do not make contact, a "high" voltage is sensed on the pulled up side of the switch 108. Conversely, when the switch 108 is closed, i.e., the ambient probes do make contact, a "low" voltage is sensed on the pulled up side of the switch 108. Thus, a sensed low voltage indicates that a compressive engagement force has been detected. These sensed voltages are reported as signals by the PCA 104 to the higher-level testing equipment 1 10. In one example, the signals are amplified by the PCA prior to being received by the testing equipment. In one example, the signals are received at substantially the same time that the engagement force is applied.

[0019] At block 206, the processor of the testing equipment 1 10 determines the amount of the engagement force applied between the unit under test and the system 100, based on the number of switches that have been closed. The greater the engagement force, the greater the surface area of the body 102 that will compress, and, thus, the greater the number of switches 108 that will be closed. For instance, if only the switch 108 ₂ in FIG. 1 has been closed, this may indicate that the engagement force has only barely been applied to the test probe 106i. However, if the switch 108i is also closed, this may indicate that the engagement force is approaching the maximum amount of force that can be applied to the test probe 106i .

[0020] The method 200 ends in block 208.

[0021 ] Thus, the system 100 allows incrementally increasing engagement force to be applied between a UUT and a set of differential test probes, while the engagement force is simultaneously measured and reported. The sensitivity of the system 100 can be varied by varying the number of switches 108 embedded in the body. Since the engagement force can be measured as it is applied, the tester can be certain that sufficient force is being applied to generate a signal, but also that the force is not so great that it will damage the fragile testing equipment, such as the test probes, which can be very expensive to replace.

[0022] FIG. 4 illustrates a front view of another example force-sensing system 400 of the present disclosure. In one example, the system 400 is implemented as a differential probe, similar to the system 100 of FIG. 1 . In this example, the system 400 includes a body 402 connected to a printed circuit assembly (PCA) 404. The PCA 404 may be further connected to higher level instruments 416 such as an oscilloscope or other computing devices.

[0023] In one example, the body 402 is formed in two pieces 402i and 402 ₂ that are mirror images of each other. In one example, each piece 402i and 402 ₂ of the body 402 has a tapered shape, i.e., a first end of the piece is wider than a second end of the piece.

[0024] Each piece 402 _! and 402 ₂ of the body 402 includes a test probe 406i or 406 ₂ (hereinafter "test probes 406") that comprises one half of a differential probe set. In one example, the test probe 406i or 406 ₂ is inserted into the second, narrower end of the piece 402i or 402 ₂ . For instance, the test probe 406i or 406 ₂ may be inserted such that the sharp end of the probe is embedded in the piece 402i and 402 ₂ , while the head of the test probe 406i or 406 ₂ visibly protrudes from the piece 402i and 402 ₂ . The material comprising the portion of the body 402 into which the test probes 406 are inserted may be formed of any non-conductive material that is capable of retaining the text probes 406. The test probes 406 could be of any style; however, in one example, the sharp ends of the test probes 406 have a "dog leg" or "side-stepped" shape that improves visibility of the heads. In a further example, the sharp ends of the test probes 406 include barbs or ribs that retain the test probes 406 in the body 402 and prevent the test probes 406 from rotating within the body 402. The user can define the distance between the test probes 406i and 406 ₂ by manually varying the distance between the pieces 402i and 402 ₂ of the body 402 and/or manually varying the positions of the test probes 406i and 406 ₂ in the pieces 402i and 402 ₂ . In one example, the test probes are formed of a glassy or amorphous metal.

[0025] One or more electro-mechanical switches 408i-408 _n , hereinafter collectively referred to as "switches 408," are also embedded in the body 402. Any number of switches 408 may be embedded in the body 402. In this case, each switch 408 comprises a layer of the body 402; thus, the terms "switch" and "layer" will be used interchangeably in the description of the system 400 to refer to the force-detecting elements. Each layer or switch 408 includes one or more individual cells. Any number of cells may be included in each layer. For simplicity of illustration, only one of these cells is designated by a reference numeral in FIG. 4: cell 410. The other cells are configured in a manner similar to the cell 410. The switches 408 may be secured to each other by a variety of means, including non-conductive glue, small non-conductive strings or springs, or other mechanisms.

[0026] As illustrated, the cell 410 comprises a plurality of metal plates 412 412 _m , hereinafter collectively referred to as "plates 412," arranged to define the walls of an at least partially enclosed volume. The volume is at least partially enclosed in that at least one wall of the volume "floats" relative to the other walls. That is, at least one wall is not fixed or attached to the remainder of the walls. For instance, in FIG. 4, the plate 412 _! of the cell 410 is not fixed to the plate 412 _m , although the plates 412i and 412 _m may make contact with each other when the body 402 is compressed as illustrated. The volume defined by the plates 412 houses a compliant member 414. In one example, the compliant member 414 is formed from a mechanically compliant, electrically non- conductive material. The compliant member 414 could for, instance, be formed from the same material as the body 102 of the system 100. For instance, in one example, the compliant member 414 is formed from a ceramic meta-material.

[0027] Each test probe 406i and 406 ₂ and each switch 408 is connected to the PCA 404, e.g., via a wire. In the example where each switch 408 comprises a layer of the body 102, all but one switch 408 are connected to individual pull up resistors to a direct current (DC) power supply voltage, while the one remaining switch 408 is connected to ground. In one example, the switch 408 that is connected to ground is the switch 408 comprising the smallest or most narrow layer of the body 402. FIG. 4 illustrates the PCA connections for the test probe 406i and the switches 408 embedded in only one piece 402i of the body 402; however, the test probe 406 ₂ and the switches 408 embedded in the other piece 402 ₂ of the body are connected to the same PCA 404 in a similar manner. In this manner, the PCA 404 is capable of receiving test signals from the test probes 406 and the switches 408. In one example, the PCA may also amplify these test signals before passing them on to higher-level instruments 416, e.g., other computing devices.

[0028] The system 400 may be suitable for applications in which the compressive force required to close the switch at the widest part of the system's body is substantially greater than the force required to close the switch at the body's narrowest part; in such an instance, the body at the narrowest part may be unable to fully recover from the compression. Thus, the system 400 is capable of sensing forces having a wide range of magnitudes. The system 400 also allows the compliant members to be manufactured in smaller sizes than the body of the system 100, which may simplify manufacturing and/or reduce manufacturing costs.

[0029] As stated above, FIG. 4 illustrates a front view of the system 400; the other dimensions of the system 400 may be configured in a similar manner. For instance, the depth of the system 400, i.e., the dimension extending outward from the page, may also be configured to have a plurality of layers that taper from a narrowest layer to a widest layer. To further illustrate this, FIG. 5 is a bottom view of the body 402 illustrated in FIG. 4. As illustrated, the number of cells per layer may increase in each dimension - i.e., height, width, and depth - as one travels from the narrowest or bottom-most layer, in which the test probes are embedded, to the widest or top-most layer.

[0030] The force-sensing system 400 may be operated in a manner similar to the operation of the system 100. Thus, the method 200 depicted in FIG. 2 may also serve as a method of operation for the system 400.

[0031 ] In this case, an engagement force applied near the test points will cause the body 402 to compress, as illustrated in FIG. 4. As illustrated, compression of the body 402 may cause the plates of one or more switches 408 to make contact with each other, thereby closing the cells in a manner that compresses the compliant members housed within the cells. In the example illustrated in FIG. 4, the engagement force is enough to cause the plate 412i at the smallest or narrowest end of the body 402 to meet the plate 412 _m corresponding to the adjacent switch 408 _n .

[0032] In one example, when a switch 408 is open, i.e., the plates of adjacent layers do not make contact, a "high" voltage is sensed on the pulled up side of the switch 408. Conversely, when the switch 408 is closed, i.e., the plates of adjacent layers do make contact, a "low" voltage is sensed on the pulled up side of the switch 408 thanks to the grounding of the plate 412-i , which ripples to the wider layers of the body 402 as the body is further compressed. Thus, a sensed low voltage indicates that a compressive engagement force has been detected at a particular layer of the body 402.

[0033] Thus, in this example, the metal plates of the cells serve not only to limit the amount of compression that can be applied to the compliant members, but also to replace the ambient probes 108 of the system 100. Since each successive layer of the body 402, i.e., moving away from the test point, includes more compliant members that must be compressed, each layer can be used to measure larger increments of engagement force. As with the system 100, the amount of the engagement force is indicated by the number of switches 408 that are closed. The greater the engagement force, the greater the surface area of the body 402 that will compress, and, thus, the greater the number of switches 408 that will be closed. For instance, if only the switch 408 _n in FIG. 4 has been closed, this may indicate that the engagement force has only barely been applied to the test probe 406i. However, if the switch 408i is also closed, this may indicate that the engagement force is approaching the maximum amount of force that can be applied to the test probe 406i .

[0034] In some instances, the upward-pointing force of the UUT touching the test probes 406 may be asymmetrical or unbalanced with respect to the layers of the body 402 being compressed. That is, the layers closest to the test probes 406 will be forced to compress due to the presence of the test probes 406, but the layers further away from the test probes 406 will not be affected by a counter-balancing force. As a result, the entire body 402 may bow or distort in a manner that creates varying distance between the two pieces 402i and 402 ₂ of the body 402, and may also create a varying distance between the individual layers of the body 402.

[0035] In one example, a three-dimensional member formed of mechanically compliant, electrically non-conductive material is provided to counteract the resistance to compression in the system 400. FIG. 6 illustrates a front view of one example of a balancing member 600 added to the system 400 of FIG. 4. Although illustrated in connection with the system 400 of FIG. 4, the balancing member 600 could also be used in connection with the system 100 of FIG. 1 . The balancing member may be formed from a ceramic meta-material.

[0036] As illustrated, the balancing member 600 is sized and shaped to fit around or to hold the body 402. As such, the interior surface of the balancing member 600 is sized and shaped to match the exterior surface of the body 402, including the area near the probe tips 406 and any other embedded switches, wires, or other exposed components. In one example, the interior surface of the balancing member 600 leaves room for adjustment of the separation distance between the test probes 406.

[0037] The balancing member 600 may be attached to the body 402, e.g., using non-conductive glue, strings, or other mechanisms. Alternatively, the balancing member 600 may be force-fit to the body 402. In one example, the balancing member 600 comprises a single, unitary piece; however, in other examples, the balancing member 600 may comprise two or more pieces fitted or attached together.

[0038] The exterior surface of the balancing member 600 may have any shape. In one example, the bottom of the balancing member 600, i.e., the portion of the balancing member 600 closest to the test points, has a rounded shape. The balancing member 600 will be compressed by contact with the circuit board area surrounding the test points, as the test probes 406 are pressed into test points of the UUT.

[0039] Thus, the balancing member 600 minimizes distortion to the body 402 resulting from asymmetrical compressive forces. As an additional benefit, the balancing member 600 may dampen mechanical vibrations that can negatively affect signal integrity and damage the test probes.

[0040] FIG. 7 depicts a high-level block diagram of a computer that can be transformed into a machine that is dedicated to perform the functions described herein. As a result, the examples of the present disclosure may help improve the operation and functioning of the general-purpose computer to sense incrementally increasing engagement force applied to a unit under test, as disclosed herein. The computer may be part of an oscilloscope or other higher- level computing device that processes signals from the PCA 104 or the PCA 404 depicted in FIG. 1 or FIG. 4, respectively.

[0041] As depicted in FIG. 7, the computer 700 comprises a hardware processor element 702, e.g., a central processing unit (CPU), a microprocessor, or a multi-core processor, a memory 704, e.g., random access memory (RAM) and/or read only memory (ROM), a module 705 for sensing engagement force, and various input/output devices 706, e.g., storage devices, including but not limited to, a tape drive, a floppy drive, a hard disk drive or a compact disk drive, a receiver, a transmitter, a speaker, a display, a speech synthesizer, an output port, an input port and a user input device, such as a keyboard, a keypad, a mouse, a microphone, and the like. Although only one processor element is shown, it should be noted that the general-purpose computer may employ a plurality of processor elements. Furthermore, although only one general- purpose computer is shown in the figure, if the method(s) as discussed above is implemented in a distributed or parallel manner for a particular illustrative example, i.e., the blocks of the above method(s) or the entire method(s) are implemented across multiple or parallel general-purpose computers, then the general-purpose computer of this figure is intended to represent each of those multiple general-purpose computers. Furthermore, one or more hardware processors can be utilized in supporting a virtualized or shared computing environment. The virtualized computing environment may support one or more virtual machines representing computers, servers, or other computing devices. In such virtualized virtual machines, hardware components such as hardware processors and computer-readable storage devices may be virtualized or logically represented.

[0042] It should be noted that the present disclosure can be implemented by machine readable instructions and/or in a combination of machine readable instructions and hardware, e.g., using application specific integrated circuits (ASIC), a programmable logic array (PLA), including a field-programmable gate array (FPGA), or a state machine deployed on a hardware device, a general purpose computer or any other hardware equivalents, e.g., computer readable instructions pertaining to the method(s) discussed above can be used to configure a hardware processor to perform the blocks, functions and/or operations of the above disclosed methods. In one example, instructions and data for the present module or process 705 for sensing engagement force, e.g., machine readable instructions, can be loaded into memory 704 and executed by hardware processor element 702 to implement the blocks, functions or operations as discussed above in connection with the exemplary method 200. Furthermore, when a hardware processor executes instructions to perform "operations", this could include the hardware processor performing the operations directly and/or facilitating, directing, or cooperating with another hardware device or component, e.g., a co-processor and the like, to perform the operations.

[0043] In one example, instructions and data for the present module or process 705 for sensing engagement force, e.g., machine readable instructions can be loaded into memory 704 and executed by hardware processor element 702 to implement the blocks, functions or operations as discussed above in connection with the exemplary method 200. For instance, the module 705 may include a plurality of programming code components, including a signal detection component 708 and a signal conversion component 710. These programming code components may be included in an oscilloscope or other higher-level computing device that is part of a force sensing system, such as the system 100 or the system 400.

[0044] The signal detection component 706 may be configured to listen for signals from a separate PCA. As discussed above, the signals may indicate that one or more switches in a force-sensing system connected to a UUT have closed.

[0045] The signal conversion component 610 may be configured to convert signals received from the PCA into a measure of the engagement force applied between the force-sensing system and the UUT. As discussed above, this may include determining the number and/or location of the switches that have closed, based on the signals.

[0046] Furthermore, when a hardware processor executes instructions to perform "operations", this could include the hardware processor performing the operations directly and/or facilitating, directing, or cooperating with another hardware device or component, e.g., a co-processor and the like, to perform the operations.

[0047] The processor executing the machine readable instructions relating to the above described method(s) can be perceived as a programmed processor or a specialized processor. As such, the present module 705 for sensing engagement force, including associated data structures, of the present disclosure can be stored on a tangible or physical (broadly non-transitory) computer-readable storage device or medium, e.g., volatile memory, nonvolatile memory, ROM memory, RAM memory, magnetic or optical drive, device or diskette and the like. More specifically, the computer-readable storage device may comprise any physical devices that provide the ability to store information such as data and/or instructions to be accessed by a processor or a computing device such as a computer or an oscilloscope.

[0048] It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made.