Assembly and method for testing an electronic circuit test fixture

A method provides testing of an electronic circuit test system that includes a test fixture having headed and headless test probes, a shorting plate and a test probe verification plate with apertures. A probe verification test includes: moving the test probe verification plate and the shorting plate into position, where the shorting plate engages any test probe that extends through an aperture of the verification plate; and transmitting an electrical signal to each of the test probes. The electricity flow associated with each of the test probes is analyzed to determine if any of the headless test probes have an open circuit. In response to detecting an open circuit: one or more of the headless test probes are indicated as (a) defective in the test fixture or (b) missing from the test fixture; and the specific locations in the test fixture of the defective or missing test probes are identified.

BACKGROUND

1. Technical Field

The present disclosure generally relates to the testing of electronic circuits and in particular to testing an electronic circuit test system that is used to test printed circuit board assemblies (PCBAs).

2. Description of the Related Art

IHSes typically contain one or more printed circuit board assemblies (PCBAs), which are manufactured and tested prior to installation into the HIS. During manufacturing of the PCBAs, electronic circuit test systems are used for testing printed circuit board assemblies (PCBAs) of various types. An electronic circuit test system is particularly suited to testing PCBAs (such as computer motherboards) with large quantities of devices under test (DUT). Examples of devices under test include resistors, capacitors, inductors, transistors, and integrated circuit devices. A typical electronic circuit test system includes a test fixture that is populated with a large number, or array, of test probes. An electrical signal can be selectively applied to each of the test probes by the electronic test system. The PCBA is typically moved into contact with the test probes via vacuum or mechanical test fixture actuation. Some test fixtures contain thousands of individual test probes in a large matrix. For example, a laptop motherboard typically requires approximately 1500 test probes and a server motherboard typically requires over 6000 test probes. In addition, several different types of test probes are typically used in a single test fixture depending upon the specific DUT to be tested.

The test probes are prone to damage and wear during use over a large number of test cycles, and the test probes require periodic maintenance. The replacement of worn test probes is a tedious manual procedure that must be performed by a human operator. Because there are thousands of test probes that may need to be removed and replaced, it is common for errors and mistakes to be made during such maintenance operations. The possible types of operator mistakes include installing a test probe in a location that does not require a test probe, omitting a test probe in a location that requires a test probe and installing the wrong type of test probe for a specific test fixture position. It is particularly difficult to determine if an incorrect type of test probe has been installed in a specific test fixture location or position. Incorrect test probes in the test fixture can cause false test results or cause damage to the PCBA.

BRIEF SUMMARY

Disclosed is a method and an assembly for automated verification of the installation correctness of test probes in an electronic circuit test fixture.

According to one embodiment, the method includes: providing a test fixture having a plurality of test probes, the test probes including one or more headed test probes and one or more headless test probes; providing a conductive shorting plate; and providing a verification plate that has apertures at specific locations relative to expected positions of the one or more headed and one or more headless probes on the test fixture. Each aperture has a perimeter dimension or orientation that allows the headless probe to pass through the aperture, but prevents the headed probe from passing through the aperture. The method also includes positioning the verification plate relative to the test fixture such that the plurality of apertures align with positions of the test probes of the test fixture, such that the one or more headless probes positioned in alignment with a corresponding aperture extends through the corresponding aperture, while each headed probe is prevented from extending through an aperture with which the headed probe is aligned. The method then includes executing at least one of a shorted probe test, a probe presence test, and a probe verification test. The combination of these tests identifies whether the headed probes and the headless probes are all present and correctly placed in the test fixture.

According to one embodiment, the probe verification test includes: moving the shorting plate into a position at which the shorting plate would engage with any test probe that extends through its corresponding aperture of the verification plate; transmitting an electrical signal to each of the test probes; and analyzing the electricity flow associated with each of the test probes to determine if any of the expected headless test probes have an open circuit. In one embodiment, the analyzing further includes comparing a location of each headless test probe that provided a closed circuit with a pre-established probe location mapping for all of the headless test probes that should exist on a correctly configured test fixture. The pre-established probe location mapping provides a correct location for each headless test probe and each headed test probe on the test fixture. In response to detecting an open circuit at locations of the test fixture at which one or more of the headless test probes are expected to be provided on the test fixture, one or more of the headless test probes are indicated as one of (a) defective in the test fixture and (b) missing from the test fixture. Alternatively, the open circuit can also indicate that one or more of the headed probes are incorrectly installed in a location designed for a headless probe. At least one corresponding location is identified in the test fixture of a defective or missing headless test probe or an incorrectly installed headed probe.

Also disclosed is an assembly for testing an electronic system, the assembly comprising: a test fixture having a plurality of test probes that include one or more headed test probes, one or more headless test probes; a conductive shorting plate; and a verification plate. The verification plate is configured with through apertures at specific locations relative to expected positions of the one or more headed and one or more headless probes on the test fixture. Each aperture has a perimeter dimension or orientation that allows a headless probe to pass through the aperture, but prevents a headed probe from passing through the aperture. The verification plate is positioned relative to the test fixture such that each of the plurality of apertures is aligned with a position of a test probe of the test fixture. With this alignment of the verification plate, the one or more headless probes positioned in alignment with a corresponding aperture extends through the corresponding aperture, while each headed probe is prevented from extending through an aperture with which the headed probe is aligned.

DETAILED DESCRIPTION

The illustrative embodiments provide a method of testing a test fixture having headed test probes and headless test probes by using a shorting plate and a test probe verification plate that has several apertures. A probe verification test is executed including placing the shorting plate and test probe verification plate into a position where the shorting plate engages any test probe that extends through its corresponding aperture on the test probe verification plate and transmitting an electrical signal to each of the test probes. The electricity flow associated with each of the test probes is analyzed to determine if any of the expected headless test probes have an open circuit or if any of the expected headed probes have a short circuit. Detecting an open circuit on the expected headless probe or a short circuit on the expected headed probe indicates that one or more of the test probes are one of (a) defective in the test fixture, or (b) missing from the test fixture or (c) the wrong type of probe. The method also includes identifying locations in the test fixture of the defective or missing test probes.

FIG. 1illustrates an apparatus or assembly50for testing an electronic circuit test fixture, within which one or more of the described features of the various embodiments of the disclosure can be implemented. Referring specifically toFIG. 1, the assembly50for testing an electronic circuit test system comprises a test fixture100. Test fixture100includes a generally rectangular shaped housing102that encloses an interior cavity (not shown). Housing102can be formed from suitable materials such as metals or plastic. A probe plate104is mounted above housing102. Housing102has a bottom surface and four side surfaces108.

An array of probe receptacles110are defined in probe plate104. Receptacles110extend entirely through probe plate104into the interior cavity of test fixture100. Test probes, which include headed test probes124, and headless test probes128, are inserted into the receptacles in the probe plate104of the test fixture, and the test probes124/128extend above the receptacles. Test probes124/128are made from an electrically conductive material such as bronze or gold plated steel.

The test probes124/128are used to contact test points on a PCBA (not shown). Typically, the headed test probes124are used to contact pin-through-hole component leads on the circuit board assembly. The headless test probes128are used to contact via pads, test pads, or surface mount attachment pads on the circuit board assembly. While nine test probes124/128are shown inFIG. 1, it is understood that test probes124/128can number in the hundreds or thousands of test probes. The array of test probes124/128is spaced in a matrix at various positions or locations (having x, y coordinates as shown in the example figure) in test fixture100.

The assembly50for testing an electronic circuit test fixture also includes a test probe verification plate150. Test probe verification plate150can be generally rectangular in shape and can be formed from suitable materials such as glass reinforced epoxy laminate sheets (e.g. G10 or FR4) or other suitable non-conductive material. Test probe verification plate150has a top surface152and bottom surface154and includes an array of apertures156that extend entirely through the test probe verification plate150. The apertures156are spaced at various aperture positions or locations (indicated as an x,y coordinate) in test probe verification plate150. Each aperture156is positioned in the test probe verification plate150in coaxial alignment with each individual headed test probe124and with each headless test probe128.

In one embodiment, apertures156are circular and have various diameters based on the types of headless and headed probes used in the test fixture. In other embodiments, apertures156have a non-circular shape or orientation such as oval or rectangular and include at least one minor or smaller dimension. In order to ensure that the apertures156align with the correct test probes, test fixture100is configured with the tooling pins165, while test probe verification plate150includes one or more corresponding tooling holes160. The combination of the tooling pins165and the tooling holes160serve to guide the test probe verification plate150into the correct position, relative to the test fixture and probes located thereon. Also, as provided for inFIG. 4, described hereafter, the tooling pins165are also utilized to guide the placement of a shorting plate175, which is also configured with tooling holes162.

In the following description of the various figures, reference is also made to elements described in preceding figures, and like elements are provided the same reference numerals throughout the description of the various figures. As an example, in the description ofFIGS. 2and3, reference is also made to elements described inFIG. 1.

With reference toFIG. 2, there are illustrated details of example headless test probes128. Headless test probes128include example headless test probe styles210and230. Headless test probes210and230are similar except that each has a different shaped terminal end or probe tip. Many more headless probe styles exist than are described in this document. Headless test probe example210is an elongated cylinder in shape and has a probe tube212, a plunger214and a terminal end or probe tip216. Example probe tip216has a single triangular shaped prong217. Headless test probe example230is an elongated cylinder in shape and has a probe tube212, a plunger214and a terminal end or probe tip236. Example probe tip236has multiple triangular shaped prongs217. The probe tubes212are received by or inserted into receptacles110of test fixture100(FIG. 1).

Referring toFIG. 3, details of headed test probes124are shown. Headed test probes124include example headed test probe styles310and330. Headed test probes310and330are similar except that each has a different shaped terminal end or probe tip. Many more headed probe styles exist than are described in this document. Headed test probe example310is an elongated cylinder in shape and has a probe tube312, a plunger314and a terminal end or probe tip316. Example probe tip316has a single triangular shaped prong317. Headed test probe example330is an elongated cylinder in shape and has a probe tube312, a plunger314and a terminal end or probe tip336. Example probe tip336has multiple triangular shaped prongs317on a cylindrical base337. The probe tubes312are received by or inserted into receptacles110of test fixture100(FIG. 1).

It is appreciated that for purposes of this disclosure, except for the type of probes, from among a headed probe and a headless probe, that is placed at each of the probe locations of the test fixture, the exact configuration of the test probes are not relevant to the overall understanding of the disclosure. The specific presentation herein of the probes and test fixture, and other parts of the overall system are presented simply to explain how exactly the test probe verification plate150is configured and utilized to test for the correct installation of headed and headless test probes in the test fixture.

FIGS. 4A-4Billustrate two views of the assembly50for testing an electronic circuit test fixture with the test probe verification plate150placed in a testing position, followed by the shorting plate410being placed in a testing position. In one implementation,FIGS. 4A and 4Brepresent a time sequence of placing the components to complete one or more tests of the probes, as described herein. As illustrated within these figures, probe testing assembly50further includes a conductive shorting plate410. Shorting plate410is generally shaped to allow shorting plate410to be able to simultaneously interface with all of the test probes124/128in test fixture100. Shorting plate410has a top surface412and a bottom surface414. Shorting plate410can be formed from a conductive material such as copper, an alloy of copper, or aluminum. Test probe verification plate150and shorting plate410are moved or positioned by an operator during testing of the assembled test fixture (with probes inserted) as will be described later.

InFIG. 4A, test probe verification plate150is shown placed in a testing position, while shorting plate410has not yet contacted the exposed headless test probes128. This view enables an understanding of the placement of test probe verification plate150relative to both the exposed headless probes and the shorting plate, when in a testing configuration. However, according to one or more embodiments, during actual testing operation, the shorting plate410is placed on top of the test probe verification plate150. Thus, in these embodiments, the combination of shorting plate410and test probe verification plate150are moved in concert, in a downward direction, towards test fixture100. As the test probe verification plate150contacts the test probes, the headed test probes124and the headless test probes128are in axial alignment with corresponding respective apertures156in test probe verification plate150such that with continued downward movement of test probe verification plate150, the headless test probes128pass through apertures156and extend above top surface152(FIG. 1), while the headed probes, which are also in axial alignment with corresponding headless test probe apertures420, do not pass through the apertures156(due to probe head diameter or size constraints). The diameter of apertures156is greater than the diameter of the headless test probes128such that the headless test probes128can pass through apertures156. However, the diameter of the apertures156is smaller than the diameter of headed probes124such that the headed probes cannot pass through the apertures. In one example embodiment, apertures156have a diameter of 40 mils, the headless test probes128have a diameter of 36 mils, and the headed test probes124have a diameter of 62 mils.

Any headless test probes128that are missing from test fixture100or any headed test probes124that are incorrectly installed in test fixture100will result in an empty opening420. Any headless test probes128that are missing from test fixture100will not be available to pass through aperture156resulting in the empty opening420. Any headed test probes124that are incorrectly installed in a headless test probe location will not be able to pass through aperture156resulting in an empty opening420.

At the same time, the headed test probes124are aligned with the bottom surface154in test probe verification plate150such that with continued downward movement of test probe verification plate150, the headed test probes124are blocked by contact with bottom surface154(FIG. 1) surrounding apertures156. This causes the headed test probes124to be compressed via the spring action of the probe, as known to those skilled in the art.

With theFIG. 4Bconfiguration, the test probe verification plate150and shorting plate410are moved downwardly towards test fixture100, until eventually the bottom surface414of shorting plate410will contact the probe tips217(FIG. 2A) of the headless test probes128. The surface of the shorting plate410becomes electrically coupled to the probe tips heads of the headless test probes128extending through the test fixture100causing all of the headless test probes128to be shorted together in a short circuit. Any headless probes that are incorrectly placed will pass through the aperture causing a short circuit to be detected at that particular location (e.g., x,y probe location) of the test fixture100.

As shown by bothFIGS. 4A and 4B, using the respective tooling holes160and162, the tooling pins165serve to guide the test probe verification plate150as well as the shorting plate410into the correct position, relative to the test fixture. This use of the tooling holes160and162and tooling pins165are aligned such that they ultimately align the apertures in the test probe verification plate150with the specific configuration and/or layout of test probes being analyzed.

FIG. 5illustrates a block diagram representation of an example test system500for testing PCBAs using test fixture100with which the test probe verification plate150and shorting plate175can be advantageously implemented. Test system500comprises a computer510that is coupled to test controller hardware520which is coupled to analog test hardware530. Analog test hardware530is coupled to test fixture interface540which is coupled to individual test probes124,128(FIG. 1) in test fixture100. The components of test system500are coupled to each other via respective interconnects, generally presented as a single connecting wire515.

Computer510can be a conventional computer, as presented inFIG. 6, described hereafter. Software/firmware such as test programs can be stored on computer510. Test controller hardware520interfaces with computer510and receives commands from computer510, which controller hardware520forwards to analog test hardware530. The analog test hardware530can include an ohmmeter that can be connected to connections of test fixture interface540. The test fixture interface540is a mechanical interface that provides electrical connectivity to the bed-of-nails test fixture100. This electrical connectivity is typically done through dedicated wiring or cables. In one or more embodiments, feedback signals from test fixture100and specifically from the individual test probes124/128can be routed to computer510for analysis thereof.

FIG. 6illustrates a block diagram representation of an example information handling system (IHS)600, within which one or more of the described features of the various embodiments can be implemented. In one embodiment, computer510ofFIG. 5can be generally represented by IHS600, although other types of devices can be utilized to perform the functionality associated with computer510. References to IHS600are understood to refer to computer510and both terms (and reference numerals) are utilized interchangeably herein. For purposes of this disclosure, an information handling system, such as IHS600, may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a handheld device, personal computer, a server, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components.

Referring specifically toFIG. 6, example IHS600includes one or more processor(s)605coupled to system memory610via system interconnect615. Also coupled to system interconnect615is local storage620within which can be stored software and one or more sets of data (not specifically shown). As shown, system memory610can include therein a plurality of modules, data612and test programs/software614. Data612can contain information about test fixture100(FIG. 1) such as the locations of the headed and headless test probes. The various software and/or firmware modules have varying functionality when their corresponding program code is executed by processor(s)605or other processing devices within IHS600.

IHS600further includes one or more input/output (I/O) controllers630which support connection to and processing of signals from one or more connected input device(s)632, such as a keyboard, mouse, or touch screen. I/O controllers630also support connection to and forwarding of output signals to one or more connected output devices634, such as a monitor or display device. Additionally, in one or more embodiments, one or more device interface(s)636provide an integration point for connecting other device(s) to IHS600. In one such implementation, device interface(s)636can further include General Purpose I/O interfaces such as I2C, SMBus, and peripheral component interconnect (PCI) buses and universal serial buses (USB). Device interface(s)636can be communicatively coupled to components of test system500such as test controller hardware520(FIG. 5).

In one or more embodiments, IHS600comprises a network interface device (NID)640. NID640enables IHS600to communicate and/or interface with other devices, services, and components that are located external to IHS600. These devices, services, and components can interface with IHS600via an external network, such as example network650, using one or more communication protocols. Network650can comprise one or more direct connections to other devices as well as a more complex set of interconnections as can exist within a wide area network, such as the Internet.

Those of ordinary skill in the art will appreciate that the hardware components and basic configuration depicted inFIG. 6and described herein may vary. For example, the illustrative components within IHS600are not intended to be exhaustive, but rather are representative to highlight components that can be utilized to implement aspects of the present disclosure. For example, other devices/components may be used in addition to or in place of the hardware depicted. The depicted examples do not convey or imply any architectural or other limitations with respect to the presently described embodiments and/or the general disclosure.

FIG. 7illustrates a flowchart of an exemplary method by which computer-based PCBA test system500operating with assembly50, as presented within the preceding figures, perform different aspects of the processes that enable one or more embodiments of the disclosure. According to one embodiment, computer-based PCBA test system500is configured to test for short circuits and open circuits. The description is provided with general reference to the specific components illustrated within the preceding figures. Generally, the processing and analysis aspects of method700are described as being implemented via the execution of code provided by test program software614executing within HIS600and/or computer510. It is however appreciated that certain aspects of the described methods may be implemented via other processing devices and/or execution of other code.

FIG. 7illustrates an example method of testing test fixture100to identify and determine if the correct test probes124/128are installed in the correct locations in the test fixture100. Method700begins at the start block and proceeds to block702where the test fixture100is installed on (i.e., communicatively coupled to) the test system500. At block704, a shorted probe test is performed without the test probe verification plate150and shorting plate410. With this first test, the computer510can determine if any of the test probes are shorted to another test probe and their location114in the test fixture. Thus, at decision block706, computer510determines if any of the test probes124/128are shorted to another test probe. In response to one or more of the test probes124/128being shorted to another test probe (or to the test fixture), computer510reports the specific shorted test probes (124/128) that require repair and their location on the test fixture100(block708). A test fixture with defective test probes is repaired (block734). After repair (block734), method700returns to block702and reinitiates the test process.

In response to none of the test probes124/128being shorted to another test probe, the shorting plate410is installed in place on the test fixture100(block712). At block714, computer510runs a probe presence test and determines the locations114of any open circuit (missing) test probes in the test fixture100. At decision block716, computer510determines if there are open circuit (missing) test probes124/128. In response to the detection of open circuit test probes (among the test probes124/128), computer510reports the open test probes (124/128) that require repair and their location in the test fixture (block718). The test fixture with defective test probes is repaired (block734). After repair (block734), method700returns to block702and reinitiates the test process.

In response to none of the test probes112having an open circuit in block716, the shorting plate410is removed (block720). The test probe verification plate150is installed on test fixture100(block722). The shorting plate410then is installed on test fixture100over test probe verification plate150and moved into contact with the probe tips217of any headless probes128that extend through apertures156in test probe verification plate150(block724). Because apertures156are axially aligned over the headless test probes128and the diameter of apertures156is greater than the diameter of the headless test probes128, only the headless test probes128can pass through apertures156and come into contact with shorting plate410.

At block726, computer510performs (or runs) a probe verification test. Electrical signals are applied to the headless test probes128and the flow of electricity between the headless test probes is monitored. Computer510determines if any of the headless test probes128have an open circuit and identifies the locations of any of the open circuit headless test probes in the test fixture (block728). Any headless test probes128that are missing from test fixture100will result in an open circuit. Also, any headed test probes124that are incorrectly installed in a headless test probe location, also will be blocked from contact with shorting plate410, resulting in an open circuit at that probe location.

Computer510analyzes electricity flow associated with each of the test probes to determine if any of the expected headless test probes have an open circuit. The analysis includes comparing a location of each headless test probe that provided a closed circuit with a pre-established probe location mapping for all of the headless test probes that should exist on a correctly configured test fixture. The pre-established probe location mapping provides a correct location for each headless test probe and each headed test probe on the test fixture100. This information can be stored as test data612within storage and/or memory of computer510.

In response to the detection of any open circuit headless test probes128, computer510reports the defective test probes that require repair and their location (block732). The test fixture with defective test probes is repaired (block734). After repair (block734), method700returns to block702and reinitiates the test process.

In response to none of the headless test probes128having an open circuit in decision block728, computer510determines if there are any short circuited, headed probe locations (decision block730). Any headless test probes128that are incorrectly installed in a headed test probe location will pass through aperture156and contact shorting plate410, leading to detection of a short circuit at that probe location. In response to the detection of a short circuit in the location expected for any headed test probes124, computer510reports the defective test probes that require repair and their position (block732). The test fixture with defective test probes is repaired (block734). After repair (block734), method700returns to block702and reinitiates the test process. In response to no defects being detected, computer510indicates that the headed test probes124and the headless test probes128are correctly installed in their corresponding correct positions in test fixture100(block736). Method700then ends.

FIG. 8illustrates an optional alternative embodiment of a test fixture and test probe verification plate with possible automation of the test operation. Automated test assembly800includes linear actuators810and820that can position and move the combination of test probe verification plate150and shorting plate175, into a specific test position. In the illustrative embodiment, linear actuator810is attached to shorting plate410by a shaft812and linear actuator820is attached to verification plate150by a shaft822. Linear actuator810moves the combined shorting plate410and verification plate150in an upward and downward direction along an axis that is perpendicular to test fixture100. Linear actuator820moves the combined shorting plate410and verification plate150in a horizontal direction along an axis that is parallel to test fixture100. Computer510can provide signals to position verification board150and shorting plate410through the use of linear actuators810and820.

The actuator810is communicatively coupled to test fixture interface540via a communication cable814. Test fixture interface540is also in indirect electrical communication with the shorting plate410, headed test probes124and headless test probes128by electrical cables862. Through test fixture interface540, computer510can trigger the selective application of electrical signals to one or more of the headed test probes124or the headless test probes128and analyze the flow of electricity between any pairs or more of headed test probes124or headless test probes128or between any one of headed test probes124or headless test probes128and shorting plate175. The above implementation is by way of example and provided solely for the purpose of suggesting one possible automated implementation of the concepts disclosed herein. It is appreciated that one or more of these processes can be performed manually, without the use of a computer, in one or more embodiments.

In the above described flow chart, one or more of the methods may be embodied in a computer readable medium containing computer readable code such that a series of functional processes are performed when the computer readable code is executed on a computing device. In some implementations, certain steps of the methods are combined, performed simultaneously or in a different order, or perhaps omitted, without deviating from the scope of the disclosure. Thus, while the method blocks are described and illustrated in a particular sequence, use of a specific sequence of functional processes represented by the blocks is not meant to imply any limitations on the disclosure. Changes may be made with regards to the sequence of processes without departing from the scope of the present disclosure. Use of a particular sequence is therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined only by the appended claims.