Printed circuit board circuit test fixture with adjustable density of test probes mounted thereon

A printed circuit board (PCB) test fixture includes a substrate, a first insulation layer formed on the substrate, a conductor layer formed on the first insulation layer and electrically connected to the upper electrodes through at least one first connection member, a second insulation layer formed on the first insulation layer, and multiple conductive cones arranged on the second insulation layer in a matrix form. A part of the conductive cones is electrically connected to the conductor layer through at least one second connection member. The circuit layout of the conductor layer, the at least one first connection member and the at least one second connection member is employed to supply testing power to a part of the conductive cones and an adjustable arrangement of the conductive cones to enhance density of test probes upon electrical testing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a printed circuit board (PCB) circuit test fixture and, more particularly, to a PCB circuit test fixture with adjustable density of test probes mounted thereon.

2. Description of the Related Art

Being one of basic procedures required for PCB fabrication, electrical testing is applied to test if a PCB to be tested is functioning and is ideally carried out by appropriate test equipment. During electrical testing, a PCB is placed on a test fixture of test equipment. The test equipment supplies power to the test fixture that further selectively supplies power to electrodes or points to be tested on the PCB to perform electrical testing of the PCB. With reference toFIG. 5, a conventional test fixture70includes a base board71, two springs72, an elevatable board73, multiple stretchable probes74and a masking board75. The base board71has multiple probe holes76formed in the base board71and evenly distributed on a top surface of the base board72in the form of a matrix. The two springs72are securely mounted on the top surface of the base board and are spaced apart from each other. The elevatable board73is mounted on top ends of the two springs72to vertically move according to a compression state of the two springs. The elevatable board73has multiple through holes77formed through the elevatable board72and corresponding to the respective probe holes76.

Each stretchable probe74has a probe cap741and a stretchable portion742. The stretchable portion742is mounted in one of the probe holes76. A bottom portion of the probe cap741is securely connected with a top end of the stretchable portion742.

When the test fixture70is applied to test a PCB80, the masking board75should be prepared beforehand and has multiple openings751respectively aligning with multiple electrodes81or points to be tested of the PCB80and a part of the multiple through holes77of the elevatable board73. After the masking board75is stacked on the elevatable board73and the PCB80is stacked on the masking board75, the masking board75and the elevatable board73compress the two springs72due to gravity, such that the elevatable board73moves toward the base board71. Meanwhile, a part of the probe caps741of the stretchable probes74penetrate through the through holes77of the elevatable board73and a part of the openings751of the masking board75for the part of the probe caps741to be electrically connected to the multiple electrodes81of the PCB80. As the stretchable portion742of each probe is connected with a wire for supplying power to the probe74, when the probe cap741of the probe is connected to a corresponding electrode81of the PCB80, power is supplied to the corresponding electrode81to perform electrical testing on the PCB80. The probe caps741of those stretchable probes74not aligning with the electrodes81are blocked by the masking board75and do not contact the PCB80to prevent short-circuit or inadvertent touch from occurring on the conducting area, such as conductor patterns, on the PCB80.

However, to avoid short-circuit arising from mutual contact of the stretchable probes74, it is critical to keep a distance between adjacent two of the stretchable probes74at least not less than a specific distance. However, the distance between adjacent two of the through holes77of the elevatable board73should be fixed, such that the distance between adjacent two of the stretchable probes74fails to be further shortened and this in turn limits a density of the points on the PCB to be tested down to a low value. Therefore, the stretchable probes74fail to contact all the electrodes or points to be tested on the PCB80and some points to be tested supposed to be conducting but not conducting are not tested or the test results are incorrect.

With reference toFIG. 6A, to solve the issue of insufficient density of the points on the PCB to be tested, the approach is to employ another test fixture with a different structure, which has at least one auxiliary board78stacked on the masking board75with each auxiliary board78having multiple through holes781formed through the auxiliary board78. When those stretchable probes74are not slanted, a probe distance between top portions of adjacent two of the probes74is L1. When a test distance L2between adjacent two of the electrodes81of the PCB80is less than the probe distance L1, a part of the electrodes81fails to be electrically connected to the stretchable probes74, causing missed points or incorrect results in the electrical testing.

With reference toFIG. 6B, when the auxiliary board78is horizontally moved, the through holes781of the at least one auxiliary board78are also horizontally moved. When the distance of the movement exceeds a diameter of the through holes781, during the course of movement, the through holes781abut against and push up corresponding probe caps741in slanted positions. The oblique angle of the probe caps741is determined by the location, size and distance of movement of the through holes781. If the distance of movement does not exceed the diameter of the through holes781, the stretchable probes74inside the respective through holes781won't be slanted at all or the oblique angle of the stretchable probes74is minor. Hence, a part of the stretchable probes74stays upright and the remaining stretchable probes74are pushed obliquely toward the unslanted stretchable probes74, such that the probe distance L1between the probe caps741can be shortened to be identical to the test distance L2between the electrodes81, so as to increase the density of points on a PCB80to be tested in the electrical testing.

Given the at least one auxiliary board78pushing obliquely against the stretchable probes74, the probe distance L1between the probe caps741can be reduced. However, during the course of movement, due to a large oblique angle and varying length and elasticity of the stretchable probes74, the slanted stretchable probes74sometimes fail to contact the electrodes81of the PCB80or just touch edge portions of the probes81to result in irregular test results. Additionally, frequent abrasion, damage and wear-out against the stretchable probes74arise from excessive oblique movement of the stretchable probes74. Accordingly, purchase of a large amount of stretchable probes74becomes necessary as a result of the shortened life duration of the stretchable probes74.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a printed circuit board (PCB) test fixture with adjustable density of test probes mounted thereon, which can tackle the problems of insufficient density of test probes upon electrical testing, damage and wear-out to test probes because of frequently tilted test probes and improper electrode contact or connection failure arising from test points on PCB being out of reach from test probes.

To achieve the foregoing objective, the PCB test fixture with adjustable density of test probes mounted thereon includes a substrate, multiple lower electrodes, multiple upper electrodes, a first insulation layer, a conductor layer, a second insulation layer and multiple conductive cones.

The substrate has a lower surface and an upper surface.

The multiple lower electrodes are formed on the lower surface of the substrate.

The multiple upper electrodes are formed on the upper surface of the substrate and are electrically connected to the respective lower electrodes.

The first insulation layer is formed on the upper surface of the substrate and has at least one first connection member electrically connected to corresponding upper electrodes.

The conductor layer is formed on the first insulation layer and is electrically connected to the at least one first connection member and the corresponding upper electrodes.

The second insulation layer is formed on the first insulation layer and has at least one second connection member electrically connected to the conductor layer.

The multiple conductive cones are formed on the second insulation layer and are adapted to electrically contact a PCB to be tested. A part of the multiple conductive cones is electrically connected to the respective at least one second connection member.

From the foregoing circuit layout of the PCB test fixture, the conductive cones serve to connect with multiple test points on a PCB to be tested, the lower electrodes on the substrate are connected with external wires to transmit power to the upper electrodes, and the upper electrodes selectively supply power to the conductive cones connected to the test points through the conductor layer, the at least one first connection member and the at least one second connection member while the unconnected conductive cones receive no power. The PCB test fixture adopts the conductive cones as test probes. The conductor layer, the at least one first connection member and the at least one second connection member are employed to selectively supply power to desired conductive cones upon testing of the PCB to be tested. To replace conventional probes with the conductive cones, the PCB test fixture effectively increases the density of test probes thereon upon high-density electrical testing. As it is unnecessary for the test probes to be tilted, test procedures can be simplified and test time can be shortened. As no purchase of test probes is required, the PCB test fixture further reduces the cost in its operation and the concern of mounting and replacing test probes is no longer necessary.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1 and 2, a PCB (Printed Circuit Board) test fixture with adjustable density of test probes mounted thereon in accordance with the present invention includes a substrate10, multiple lower electrodes21, multiple upper electrodes22, a first insulation layer30, a conductor layer23, multiple connection electrodes24, a second insulation layer40, multiple surface electrodes25and multiple conductive cones50.

The substrate10is a ceramic substrate and has an upper surface12, a lower surface11and multiple conducting members13. The lower surface11is opposite to the upper surface12.

The lower electrodes21are formed on the lower surface11of the substrate10and are arranged in the form of a matrix and are spaced apart from each other. The upper electrodes22are formed on the upper surface12of the substrate10and are aligned to vertically correspond to the respective lower electrodes21. Each conducting member13is mounted through the substrate10with two ends thereof electrically connected to the lower electrode21and the upper electrode22adjacent thereto.

The first insulation layer30is formed on the upper surface12and the multiple upper electrodes22and has a first insulation surface31, at least one first via32and at least one first connection member33. The first insulation surface31is defined as a top surface of the first insulation layer30. The at least one first via32is formed through the first insulation layer30and is aligned to respectively adjoin corresponding upper electrode(s)22. The at least one first connection member33is respectively inserted into the at least one first via32and is electrically connected to the corresponding upper electrode(s)22.

The conductor layer23and the multiple connection electrodes24are formed on the first insulation surface31. The conductor layer23is electrically connected to the multiple connection electrodes24. The multiple connection electrodes24and the multiple upper electrodes22are vertically aligned with each other. A part of the multiple connection electrodes24is electrically connected to the respective at least one first connection member33for the conductor layer23and the part of the multiple connection electrodes24to be electrically connected to a part of the multiple upper electrodes22through the respective at least one first connection member33. The second insulation layer40is formed on the first insulation surface31, the conductor layer23and the multiple connection electrodes24and has a second insulation surface41, at least one second via42and at least one second connection member43. The second insulation surface41is defined as a top surface of the second insulation layer40. The at least one second via42is formed through the second insulation layer40and is aligned to adjoin a part of the multiple connection electrodes24. The at least one second connection member43is respectively inserted into the at least one second via42and is electrically connected to the part of the multiple connection electrodes24.

The multiple surface electrodes25are formed on the second insulation surface41and are vertically aligned with the respective connection electrodes24. A part of the multiple surface electrodes25is electrically connected to the part of the multiple connection electrodes24through the respective at least one second connection member43.

The multiple conductive cones50are formed on and electrically connected to the respective surface electrodes25. Each conductive cone50progressively decreases in diameter in an upward direction perpendicular to the second insulation surface41. With reference toFIG. 3, each conductive cone50has a conducting layer51, a strengthening layer52and an anti-oxidant layer53. The conducting layer51is conical. The strengthening layer52is formed around a periphery of the conducting layer51to enclose the conducting layer51. The strengthening layer52is higher than the conducting layer51in hardness to increase strength of the conductive cones50, such that the conductive cones50possess sufficient strength to support a PCB to be tested. The anti-oxidant layer53is formed around a periphery of the strengthening layer52to enclose the strengthening layer52and the conducting layer51therein. As the conductive cones50serve to electrically connect points to be tested on a PCB, to prevent conductivity of the conductive cones50from dropping because of oxidation, the anti-oxidant layer53serves to prevent the conducting layer51from being oxidized with external air surrounding the conductive cones50.

The conducting layer51may be made from copper or a copper alloy. The strengthening layer52may be made from nickel, cobalt, tungsten or an alloy thereof. The anti-oxidant layer53may be made from gold, tin or an alloy thereof. In the present embodiment, the strengthening layer52may be an alloy of nickel and cobalt or an alloy of nickel and tungsten. A nickel-containing portion of the alloy of nickel and cobalt or the alloy of nickel and tungsten is in a range of 95% to 97%.

With reference toFIG. 4, when the PCB test fixture is used to perform electrical testing of a PCB to be tested60, the PCB test fixture is mounted to a testing device and is connected to a conducting board or multiple wires on the testing device, and the PCB to be tested60is placed on the conductive cones50for test points61(or electrodes) of the PCB60to be in contact with the conductive cones50. The testing device employs the conducting board or the wires to transmit power to the lower electrodes21of the PCB test fixture to supply power to the PCB test fixture. The PCB test fixture further adopts a circuit layout of the conductor layer23, the at least one first connection member33and the at least one second connection member43to selectively transmit the power of the testing device to the conducting cones50in contact with the test points61for performing electrical testing or circuit testing on the PCB60. In response to locations of test points61varying from PCB to PCB, the circuit layout in association with the conductor layer23, the at least one first connection member33and the at least one second connection member43may be altered to adjust current-flowing paths so as to control power to be transmitted to desired conductive cones50. Thus, the circuit layout of the conductor layer23, the at least one first connection member33and the at least one second connection member43should match with the test points61of the PCB to be tested60.

The PCB test fixture in accordance with the present invention may be produced by current PCB fabrication processes and the circuit layout of the conductor layer23, the at least one first connection member33and the at least one second connection member43are formed to correspond to the electrodes61of the PCB to be tested60. Accordingly, PCB suppliers can complete and obtain the PCB test fixture using currently available materials, rendering the electrical testing of PCB easy.

The present invention eliminates the use of conventional stretchable probes in connection with test points61of the PCB to be tested60, and the density of test probes is therefore not subject to the limitation of the distance between conventional stretchable probes. However, care should be taken to avoid electrical contact with the surface electrodes25underneath the conductive cones50of the PCB test fixture. The layout of the conductive cones50can be arranged at a high density. The minimum distance between the conductive cones50can be made to be the same as that formed by current PCB industry without any chance that the distance between the test points61of the PCB to be tested60is less than the distance between the conductive cones50.

In sum, the PCB test fixture in accordance with the present invention employs the circuit layout of the conductor layer, the at least one first connection member and the at least one second connection member to transmit power to the conductive cones in connection with the test points on the PCB to be tested. Because the conductive cones can be arranged at a high density, higher density of test probes can be acquired upon the use of the PCB test fixture for electrical testing. As can be completed by current PCB fabrication processes, the PCB test fixture can be made in a simpler way. Moreover, upon using the PCB test fixture for electrical testing, electrical testing efficiency increases and material cost for electrical testing decreases because no additional device is required and no probe replacement is necessary. Even though trace width and trace of PCB made by current PCB industry become finer and finer and thinner and thinner, the technique of the PCB test fixture is synchronous with current PCB fabrication technique. As such, the density of test probes in accordance with the present invention can keep abreast of the technique of PCB industry, thereby resolving the issue of insufficient density of conventional stretchable probes upon electrical testing.