Test head for a finger tester as well as a finger tester with multiple such test heads and a method for testing printed circuit boards

Abstract

This invention relates to: a test head for a finger tester used to test a printed circuit board; a finger tester; and a method for testing a printed circuit board. The test head includes: - a slider movably disposed on a lead wire of the finger tester; - a holding module for holding a rotating arm formed at a free end spaced apart from the holding module for receiving a test probe; - a lifting device by which the holding module is adapted to be vertically movable relative to the slider, the lifting device including a vertical guide rail having a rolling bearing; and - a rotating device for rotating the holding module and thus the rotating arm about a vertical rotation axis, wherein the rotating device includes a motor for rotating the rotating device. The test head is characterized in that the rotating device includes a shaft or axle, wherein a rotating member of the rotating device is concentrically arranged with the shaft or axle, such that the rotating member surrounds the shaft or axle, and the rotating member is mounted on the axle by at least one rolling bearing or the shaft is mounted on the slider by at least one rolling bearing, and the motor is configured as a direct drive, wherein the rotating member forms the rotor of the motor.

Description

[Technical Field]

[0001] The present invention relates to a test head for a finger tester, a finger tester having a plurality of such test heads, and a method for testing a printed circuit board using such a finger tester. [Previous Technology]

[0002] A finger tester is a testing device that sequentially contacts the contact points of a printed circuit board, with one contact finger or test finger at each contact point. When testing an unassembled PCB, the traces of the PCB under test are primarily tested for interruptions in the traces and for short circuits between traces. Measurements are typically performed as resistance and / or capacitance measurements. A basic design of such a finger tester can be found in EP 0 468 153 B1. It discloses a finger tester with several contact fingers mounted on sliders so as to be rotatable about a vertical axis and height adjustable, wherein the sliders of each contact finger are slidably mounted on horizontal intersecting members. The conductors themselves can move horizontally, transversely to the longitudinal direction of the corresponding conductor.

[0003] Such finger testers are also known, wherein several wires are arranged in fixed positions.

[0004] EP 0 853 242 A1 describes a method for testing printed circuit boards using a finger tester.

[0005] EP 1 542 023 B1 describes a finger tester for testing unassembled printed circuit boards, comprising an air-bearing linear motor on a test head. Such an air-bearing linear motor allows for extremely rapid vertical movement of the test head, thereby enabling rapid contact between the test probe and the contact points of the printed circuit board under test.

[0006] DE 10 2013 102 564 A1 discloses a lead wire unit for a test apparatus for a printed circuit board, characterized in that the lead wire unit is designed to accommodate at least two independent linear conductors, which are used to guide at least one of the positioning units.

[0007] The applicant of this patent application sells such finger testers under the product names A7 and A8, which include a test head having a vertical guide rail with roller bearings and therefore not mounted on an air bearing.

[0008] The applicant also manufactures and sells finger testers under the product names S2 and S3, which have a linear motor with an air bearing on the test head for vertical movement.

[0009] Test heads with air bearings are significantly faster than those without, but they are also significantly more complex to manufacture and correspondingly more expensive. In the case of an air-bearing test head, the components supported by the air bearing are extremely lightweight. These components are specifically the arms of the contact fingers that carry the test probes. These arms are extremely thin. Therefore, they generate only very low moments of inertia. However, their length is limited and they are very sensitive to damage. The arms can therefore be easily damaged when changing test probes.

[0010] In addition to finger testers, parallel testers are also known for testing printed circuit boards, each having a connector for simultaneously contacting all contact points of the printed circuit board under test. Such parallel testers are, in principle, much faster than finger testers, but additional connectors must be manufactured for each type of PCB, which is expensive.

[0011] The success of finger testers in the market is primarily determined by the testing speed, which allows for the measurement of multiple contact points on the PCB under test. Printed circuit boards typically have thousands of contact points. Many printed circuit boards are manufactured only in small series or are pre-production series required to accelerate mass production, so manufacturing adapters for parallel testers is often not beneficial. However, due to their complexity and the large number of contact points, their testing is extremely complex.

[0012] The objective of the present invention is to further develop a finger tester in such a way that, on the one hand, it is simple in design and can be manufactured at low cost; on the other hand, it achieves high throughput of the printed circuit board under test. [Summary of the Invention]

[0013] According to a first aspect of the present invention, a test head for a finger tester is provided, the finger tester being used to test printed circuit boards, the test head comprising: - a slider movably configured on a lead wire of the finger tester; - a holding module for holding a rotating arm adapted to receive a test probe at an end spaced apart from the holding module; - a lifting device, the holding module being designed to be movable in a vertical direction relative to the slider by means of the lifting device, wherein the lifting device includes a vertical guide rail having rolling bearings; - a rotating device for rotating the holding module and thus the pivoting arm about a vertical rotation axis, wherein the rotating device includes a motor for rotating the rotating device.

[0014] The test head is characterized in that the rotating device includes a shaft or axle, wherein the rotating member of the rotating device is concentrically arranged with the shaft or axle, so that the rotating member surrounds the shaft or axle, and the rotating member is mounted on the axle by means of at least one bearing or mounted on the slider via the shaft by means of at least one bearing, and the motor is formed as a direct motor, wherein the rotating member forms the rotor of the motor.

[0015] The shaft is fixed to the slider, that is, the shaft will not rotate, but the shaft rod can rotate relative to the slider.

[0016] The motor is suitable for directly driving a rotating device without the intervention of a gear mechanism. Because the rotating member surrounds a shaft or axle, its diameter is larger than that of the shaft or axle. On the one hand, the rotating member represents the rotor of the motor; on the other hand, the rotating member is an integral part of the rotating device. In addition, due to the relatively large diameter of the rotating member, high torque can be applied, which allows for high acceleration corresponding to rotational movement.

[0017] Preferably, the motor is a torque motor. In short, a torque motor can be considered a large servo motor optimized for high torque. Torque motors are typically constructed as brushless DC motors. However, switched reluctance motors are sometimes also used as torque motors. Preferably, the torque motor is a high-pole servo motor with, for example, at least 20 poles.

[0018] This invention is based on the following findings: 1. When measuring multiple contact points on a PCB under test, most of the time is spent moving the test finger from one contact point to another on the PCB, rather than performing individual measurements. 2. As explained above, air-bearing linear conductors allow for extremely fast vertical movement of the test head and thus shorten the travel time. However, a disadvantage is that, due to the air bearing, the movement mass of the test head supported by the air bearing is limited, and therefore only test fingers with relatively short arm lengths (at most a maximum of about 150 mm) are possible. Bearing configurations using rolling bearings (such as ball bearings, crossed roller bearings, or the like) can also reliably transmit higher mass and torque and allow for longer arm lengths of the test finger. A longer arm length has several advantages. First, a longer arm length means that the test probe attached to the rotating arm moves faster at the same rotational speed. Second, a longer rotating arm also allows for a larger test area. The applicant uses a rotating arm with an angle range limited to a maximum of 0° and approximately 45°, where 0° means the rotating arm is configured parallel to the guide wire on which the test probe is mounted, and 45° means the rotating arm forms a 45° angle with the guide wire. Within this angle range, extremely rapid movement of the test probe away from or towards the guide wire is achieved. At larger angles, the speed of movement of the test probe decreases in the lateral direction relative to the guide wire. The longer the rotating arm, the wider the area that the test head can cover along the corresponding guide wire. 3. At the end of the rotational movement, the rotating arm oscillates slightly. The test fixture described at the beginning comprises a steel shaft with a diameter of 8 mm and a distance of approximately 20 mm between the engagement point of the motor (=drive) on the shaft and the attachment point of the rotating arm (=output). The shaft is a solid body. Due to the axial offset between the drive and the output, this shaft vibrates somewhat during braking. The shaft thus forms a body subjected to torsional vibration.

[0019] In this invention, such torsional vibrations are largely avoided because the rotating component, significantly larger than the shaft, is directly driven. Due to its size and rigidity, the rotating component itself is not subjected to torsion and is directly coupled to the rotating device or forms an integral part of the rotating device, thus avoiding the transmission of torque via a slender shaft. The shaft or shaft is used only to support the rotating device and not to transmit the driving force applied by the motor to the mass of the rotating device to be rotated (specifically, the lifting device and the rotating arm). This avoids the torsion of conventional shafts. This is achieved by separating the bearings on the shaft or shaft from the drive on the rotating component.

[0020] Preferably, the shaft or shaft rod has a minimum outer diameter of at least 10 mm in the region where the bearing is located. The rotating device is supported on the shaft or by means of the shaft rod. The shaft or shaft rod may also have an outer diameter of at least 20 mm in the bearing region, specifically at least 25 mm, at least 30 mm, or even at least 35 mm. The larger the diameter of the shaft or shaft rod, the more stable the bearing of the rotating device.

[0021] Preferably, the rotating member is designed to have a maximum outer diameter of at least 50 mm. The rotating member may also have a maximum outer diameter of at least 60 mm, specifically at least 70 mm, and preferably at least 80 mm. The larger the outer diameter of the rotating member / rotor, the greater the torque generated by it.

[0022] If the test probe is configured to rotate and move its tip toward a target area with a width of 5 μm, the torsional vibration will cause a delay before it decays. With a conventional shaft of 8 mm in diameter and a distance of 20 mm between the drive and the output on the shaft, the delay is 40 ms. With a target window of 25 μm, it still takes 5 ms for the oscillation to decay.

[0023] It has been demonstrated that using a shaft or spindle with an outer diameter of at least 15 mm and the test head design according to the invention reduces the oscillation time to 7 ms for a target window of 5 μm and to 1 ms for a target window of 25 μm. If the shaft or spindle has an outer diameter of 55 mm, the outward oscillation time is reduced to less than 0.5 ms for a target window of 5 μm.

[0024] During this transient oscillation, the shaft does not exhibit torsional oscillation, but there is complex oscillation behavior of the rotating arm and tilting oscillation of the shaft or axle. The larger the diameter of the shaft or axle, the smaller the tilting oscillation. When the outer diameter of the shaft or axle is 55 mm, due to the high hardness of the bearing, there is practically no time requirement for the outward oscillation of the rotational movement.

[0025] The rotating device is not driven by a motor-driven shaft, but is rotatably mounted on a fixed or non-rotating shaft, or preferably by a shaft with a minimum outer diameter of 10 mm. Such an outer diameter requires a correspondingly large and stable bearing. Furthermore, the torque motor meshes directly with the rotating device independently of the shaft or shaft. Force is introduced at the rotating component with a diameter larger than the shaft or shaft. This avoids the drive and output offset along the axial direction of the slender shaft common in the prior art. Because in conventional rotating devices, the drive and output on the slender shaft are spaced apart from each other in the axial direction, this causes torsional vibration of the shaft, which, as the inventors have discovered, significantly delays transient oscillations at small contact points on the printed circuit board under test.

[0026] In the applicant's finger tester, the printed circuit board is horizontally arranged in the test area. Therefore, in this description, "vertical" refers to a direction perpendicular to the surface of the printed circuit board under test located in the finger tester. In principle, it is also possible that in the test apparatus, the printed circuit board under test may not be horizontally arranged, but rather, for example, at an angle or vertically. In this case, the various components of the test fixture must be aligned accordingly.

[0027] The arm length of the rotating arm is preferably at least 150 mm. The arm length is measured from the vertical rotation axis to the free end of the rotating arm to which the test probe can be attached. The effective arm length is the arm length from the vertical rotation axis to the tip of the test probe, to which the contact point of the printed circuit board under test will contact. The effective arm length is preferably at least 160 mm, specifically at least 170 mm or at least 180 mm.

[0028] The bearing is preferably at least an angular contact ball bearing.

[0029] Preferably, the shaft is supported on the slider or the rotating component is supported on the shaft by a set of at least two angular ball bearings, which allows the rotating parts to be positioned and held very precisely relative to the axis of rotation.

[0030] Angle contact bearings preferably include ceramic balls.

[0031] Preferably, the motor and rotating components are arranged substantially in the same plane as at least one rolling bearing. This means that there is no tilting torque or only a very low tilting torque, which can be caused by the axial offset of the drive and the bearing. In addition, arranging the motor, rotating components and bearings (specifically, rolling bearings) in substantially the same plane is extremely space-saving and compact.

[0032] In a roughly plane, there exists a plane that extends through the area where the rolling bearing is located, and also through the rotating component and the motor. Thus, the motor and the bearing are concentrically arranged in a plane, so the operation of the motor does not exert a tilting torque on the rotating component or the shaft, or only exerts a very low tilting torque.

[0033] If the rotating device has a shaft, the maximum length of the shaft is preferably 40 mm, and specifically only 30 mm. The shorter the shaft, the higher its stiffness.

[0034] The rotating arm is preferably tubular and made of fiber composite material. This gives the rotating arm high strength and low weight.

[0035] Specifically, the rotating arm is composed of a single block. The fibers in the fiber composite material are preferably carbon fibers. Such a single block has high stiffness.

[0036] On the one hand, such a rotating arm can be relatively long and lightweight; on the other hand, its high strength helps prevent vibration of the test probe when it approaches the contact point of the printed circuit board under test. This is particularly suitable for monolithic tubular designs of rotating arms made of fiber composite materials. This rotating arm is therefore highly advantageous when combined with the direct drive explained above and the use of rolling bearings to mount the lifting device. Direct drive avoids torsional vibration on the drive shaft known in the prior art, and the roller bearings on the lifting device allow for the use of a long rotating arm.

[0037] The rotating arm can taper toward the free end. This reduces the weight in the direction toward the free end of the rotating arm, thereby keeping the moment of inertia of the rotating arm low. In addition, taper also helps to reinforce the rotating arm.

[0038] The rotating arm can be bent in the side view as follows: the free end of the rotating arm is offset slightly from the end attached to the rotating device. The rotating arm can therefore be configured such that the free end is offset slightly from the slider. The rotating arm is thus bent slightly in the direction of the test area, where the sample is positioned for testing. This curvature of the rotating arm increases its rigidity and creates space for a camera to be mounted above the rotating arm. The camera can be attached to the rotating device, thus allowing the camera to detect the test probe, and specifically the contact tip of the test probe, to determine whether the test point of the printed circuit board under test is in correct contact with the test probe.

[0039] The test head may therefore be equipped with a camera for monitoring the positioning of the probe tip of the test probe.

[0040] The rotating component or rotor may contain a plurality of permanent magnets on its outer circumference, which interact with the magnetic field coils of the motor's stator. Because the magnetic field coils are located on the stator, it is not necessary to transmit current to the rotor to drive the motor. This simplifies the design of the device.

[0041] The stator and rotor of the motor are preferably designed to extend around a complete circle. Since the motor itself is only used to rotate within a range of ±45°, the stator and / or rotor could also be designed as a segment of a circle. However, if the stator and rotor extend around a complete circle, the torque achievable with the motor's compact design is much greater than if the stator or rotor only extends along a segment of a circle. This large torque allows for rapid rotation of the rotating mechanism. This is particularly advantageous when combined with a long rotating arm, as it allows the test probe to move extremely quickly between the various contact points on the circuit board under test.

[0042] The lifting device is preferably configured on the rotating device and includes a linear motor for moving the holding module.

[0043] The moving wheel of the linear motor can be formed on the slider to make the slider move.

[0044] Preferably, the lifting device is configured to be offset from the vertical rotation axis of the rotating device, so that the cable, which is basically used to transmit measurement signals and for motor control, is routed approximately along the vertical rotation axis in the area between the holding module and the slider. Although this slightly increases the moment of inertia of the test head, it has the effect of significantly extending the service life of the cable because in different designs of the test head, it will move more as the rotating head rotates.

[0045] According to another aspect of the invention, a finger tester is provided for testing printed circuit boards, and more particularly for testing unassembled printed circuit boards, comprising at least two wires, with at least one test head disposed on each of the at least two wires, as explained above.

[0046] When testing an unassembled PCB, test traces are used to detect interruptions and short circuits between adjacent PCBs. Compared to an assembled PCB, a PCB has more test points to contact and the test head needs to move more frequently. Therefore, the travel time for the probe to move from one test point on the PCB to another test point on the PCB under test is much longer when testing an unassembled PCB than when testing an assembled PCB. The test head of this finger tester allows the test probe and its test pins to move extremely quickly from one test point to another.

[0047] Preferably, each lead wire is made of a stone. The stone may contain grooves in which the stator of the linear motor is located, thus allowing the moving wheel of the linear motor, mounted on the test head, to move relative to the stator. Furthermore, a guide element or rail may be provided on the stone, guiding the slider along the lead wire. The stone is preferably a granite block.

[0048] According to another aspect of the present invention, a method is provided for testing a printed circuit board, specifically for testing an unassembled printed circuit board, using the finger tester explained above. In this method, after the rotational movement of one of the rotating arms, the time for waiting for the rotating arm to swing inward until it contacts the contact point to be tested does not exceed 5 ms.

Implementation Method

[0056] An embodiment of the finger tester 1 according to the present invention includes a frame 2, a total of four wires 3 or cross members respectively formed on the frame 2, and two test heads 4 movably disposed in each of the four wires 3 or cross members.

[0057] The frame 2 is made of granite blocks and includes a double-T shaped base plate 5 and a double-T shaped top plate 6 in the plan view. The base plate 5 and the top plate 6 each include longitudinal members 7, at the ends of which protrusions 8 project on each side. The top plate 6 and the base plate 5 are aligned with each other in the plan view, with vertical columns 9 located between the corresponding protrusions 8.

[0058] Two longitudinally extending grooves 10 are formed on each of the opposing surfaces of the longitudinal member 7, and each of the grooves 10 forms one of the wires 3. The stator 11 of the linear motor is disposed in each of the grooves 10 and extends over most of the length of the groove 10.

[0059] Adjacent to the groove 10, the guide rail 12 is disposed on the surfaces of the longitudinal member 7 facing each other, and the test head 4 can slide on the guide rail with the corresponding mating guide element 18.

[0060] Test area 13 is formed at the center and parallel to longitudinal member 7, and the printed circuit board under test can be accommodated in test area 13. In Figures 2 and 3a, test area 13 is schematically shown only by the board located where the printed circuit board under test will be placed. Test area 13 includes corresponding holding elements for holding the printed circuit board, which are omitted here for simplicity.

[0061] Each of the test heads 4 includes a base 14, which is generally plate-shaped in the plan view and includes a conductor side 15 facing the conductor and a test head side 16 facing away from the conductor.

[0062] A plate-shaped drive wheel 17 of the linear motor is attached to the wire side 15, and the drive wheel is vertically arranged on the wire side 15. Adjacent to the drive wheel 17, a guide element 18 is provided for sliding in the guide rail 12.

[0063] A rotating device 19 is disposed on the test head side 16, and a lifting device 20 is formed on the test head side 16. The lifting device 20 allows the holding module 21 to move in the vertical direction, and a rotating arm 22 is attached to the holding module 21. The rotating arm is formed at a free end spaced away from the holding module 21 for receiving the test probe 23. The test probe 23 includes a test needle 24, which has a probe tip 25 for contacting a contact point on the printed circuit board under test.

[0064] The rotating device 19 is designed to rotate the unit, which includes the lifting device 20, the holding module 21, the rotating arm 22 and the test probe 23, about the rotation axis 41, which is perpendicular to the test area 13.

[0065] The rotating device 19 includes a vertical shaft 26 fixedly attached to the base 14. In this embodiment, the vertical shaft 26 is formed of a tubular body. Two rolling bearings 27 are disposed on the outer circumference of the vertical shaft 26. The vertical shaft 26 has a large outer diameter in the region of the bearings 27 adjacent to the shaft, which is 35 mm in this exemplary embodiment. The rolling bearings 27 are angular ball bearings pressed together and aligned in opposite directions. This makes it possible to achieve a bearing configuration that is highly resistant to tilting. A rotating member 28 is located on the outer circumference of the rolling bearings 27. The rotating member 28 is a generally cylindrical rotationally symmetric body that is rotatably mounted about the vertical shaft 26 by means of the rolling bearings 27.

[0066] The rotating member 28 includes permanent magnets 29 arranged at regular intervals on its outer circumference and forms the rotor of the motor 30. The motor 30 is designed as a torque motor. The stator of the motor 30 is fixedly attached to the base 14 and surrounds the rotating member 28. The stator 31 includes a plurality of magnetic coils (not shown) that are controlled to apply torque to the rotating member 28 forming the rotor of the motor 30.

[0067] In this embodiment, the motor 30 has twenty-eight poles, that is, a corresponding number of permanent magnets are disposed on the rotating member 28. Preferably, the motor includes at least twenty poles.

[0068] The rotating base 32 is attached to the rotating member 28, and includes a central section 33, a lifting rail 34, and a compensation section 35, which is opposite the lifting rail 34 in diameter at the central section 33. The compensation section 35 has an arcuate shape in plan view and serves as a counterweight for the lifting rail 34. Therefore, the center of gravity of the rotating device 19 is located near the rotation axis 41. A linear scale is formed on the outer circumference of the compensation section 35, and this linear scale is scanned by an optical sensor 36. This detects the rotational position of the rotating device 19.

[0069] The lifting rail (34) includes a vertical guide rail.

[0070] The retaining module 21 is mounted on the lifting rail 34 by means of a rolling bearing 37, and therefore the retaining module 21 is designed to move vertically on the lifting rail 34. The lifting rail 34 includes a stator 38 of a linear motor and the retaining module 21 includes a corresponding slider 39 of the linear motor. The rolling bearing 37 is part of a cross roller guide disposed between the retaining module 21 and the lifting rail 34.

[0071] The retaining module 21 and the slider 39 together form a T-shape in the plan view, wherein the slider 39 is located in the groove formed by the stator 38, so that the retaining module 21 can be moved in the vertical direction by applying an upward or downward torque using a linear motor. Therefore, the retaining module 21 moves downward or upward together with the rotating arm 22.

[0072] The rotating arm 22 is a one-piece monolithic structure made of fiber-reinforced composite material. Specifically, the rotating arm is made of a fiber composite material containing carbon fibers. The rotating arm is tubular in shape, with a slightly circular or elliptical cross-section. The rotating arm has one end attached to the support module 21 and includes a free end 40 spaced apart from the support module 21. A test probe 23 is disposed at the free end 40 of the rotating arm 22. Such a test probe is known, for example, from WO 03 / 048787.

[0073] For ease of explanation, the wires used to control the motor or to transmit measurement signals from the test probe 23 to the evaluation device (not shown) are not shown in the diagram. The wires used to transmit measurement signals are routed within the hollow rotating arm and through the hollow vertical axis 26. The lifting device 20 is slightly offset from the rotating axis 41, which passes through the hollow vertical axis 26 at its center. The hollow vertical axis 26 represents the volume, while the rotating axis 41 is the geometric line. The shaft 26, the rolling bearing 27, the rotating component 28, and the stator 31 of the motor 30 are all concentrically arranged relative to the rotating axis 41 and are all located in the same plane. This arrangement not only saves space but also eliminates tilting torque, which would exist if the drive were offset from the bearing 27 relative to the rotating axis 41.

[0074] This special type of drive or bearing combination, with the lifting device 20 mounted via rolling bearing 37, allows the use of a large rotating arm 22, thus enabling the test head 4 to scan a wide range along the wire, and also allowing the test probe 23 to be moved away from or in the direction of the wire very quickly. Compared to test heads with air bearings, the test head 4 has a simpler and cheaper design. The special design of the rotating device allows it to rotate rapidly, requiring no or only slight oscillations when reaching the contact point to be contacted. Therefore, high throughput can be achieved more easily when testing specific printed circuit boards.

[0075] The second embodiment of the present invention (Figure 4) is explained below. The second exemplary embodiment substantially corresponds to the first exemplary embodiment, therefore the same parts have the same reference numerals and will not be explained further. Unless otherwise stated below, the explanation of the first exemplary embodiment above also applies to this second exemplary embodiment.

[0076] The second embodiment differs from the first embodiment in that a rotating shaft 42 is provided instead of a fixed vertical shaft 26. The rotating shaft 42 is rotatably mounted on a bushing 43 via a rolling bearing 27. The bushing 43 concentrically surrounds the shaft 42 and the rolling bearing 27 and is fixedly attached to the base 14 of the test head 4. The shaft 42 extends radially above the bushing 43 with a thin disc-shaped wall and is connected to a rotating member 28. The rotating member 28 is thus rotatably mounted on the base or slider 14 of the test head 4 via the shaft 42.

[0077] The shaft 42 may be designed as a solid body or as a hollow shaft. In the region where the shaft 42 rests against the inner side of the rolling bearing 27, the outer diameter of the shaft 42 is also 35 mm.

[0078] Both types of test heads 4 allow for rapid rotational movement without long inward rotation time. Combined with the stone frame 2 that integrates the wires 3, a finger tester is provided, enabling reliable and rapid contact with printed circuit boards with minimal contact points. The weight and rigidity of the frame 2 prevent vibration or other uncontrolled movement caused by the movement of the test head 4, which could reduce the positioning accuracy of the test probe.

[0079] Preferably, each second test head is equipped with a camera 44 (Figure 1) to monitor the position of the test pin 24 or probe tip 25 relative to the corresponding contact point of the printed circuit board under test. [Simplified Explanation of the Diagram]

[0049] The invention will be explained in more detail below by way of example with reference to the accompanying drawings, in which:

[0050] Figure 1 shows a perspective view of a finger tester with four leads and eight test heads.

[0051] Figure 2 shows a side view of the granite frame of the finger tester without the test head.

[0052] Figure 3a shows the test head in a view from the test area toward the test head.

[0053] Figure 3b shows the test head of Figure 3a in a transverse sectional view.

[0054] Figure 3c shows the test head of Figure 3a in a perspective sectional view.

[0055] Figure 4 shows a cross-sectional view through the test head of another embodiment. [Biomaterial Storage]

[0081] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A test head for a finger tester used to test a printed circuit board, the test head comprising: - a slider movably disposed on a lead of the finger tester; - a holding module for holding a rotating arm adapted to receive a test probe at a free end spaced apart from the holding module; - a lifting device by which the holding module is adapted to be movable in a vertical direction relative to the slider, the lifting device including a vertical guide rail having a rolling bearing; and - a rotating device for rotating the holding module and the rotating arm about a vertical rotation axis, the rotating device including a motor for rotating the rotating device. The rotating device includes a shaft or axle, wherein a rotating member of the rotating device is concentrically arranged with the shaft or axle, such that the rotating member surrounds the shaft or axle, and the rotating member is mounted on the axle by at least one rolling bearing or mounted on the slider via the shaft by at least one rolling bearing, and the motor is configured as a direct drive, wherein the rotating member forms the rotor of the motor.

2. The test head as described in claim 1, wherein the length of the rotating arm is at least 150 mm.

3. The test head as claimed in claim 1, wherein the shaft or shank is formed to have an outer diameter of at least 10 mm in the region where the rolling bearing is disposed on the shaft or shank.

4. The test head as claimed in claim 1, wherein the rotating member is formed to have a maximum outer diameter of at least 50 mm.

5. The test head as described in claim 1, wherein the rotating arm is tubular and made of fiber composite material.

6. The test head as claimed in claim 1, wherein the rotating arm tapers in the direction of the free end and / or is bent in a side view such that the free end of the rotating arm is configured to be slightly offset relative to the end fastened to the rotating device.

7. The test head as claimed in claim 1, wherein the motor and the rotating component are arranged on the same plane as the at least one rolling bearing.

8. The test head as claimed in claim 1, wherein the rotating device includes the shaft having a maximum length of 40 mm.

9. The test head as described in claim 8, wherein the shaft has a maximum length of 30 mm.

10. The test head as claimed in claim 1, wherein the lifting device is configured to be offset from the vertical rotation axis of the rotating device, so that a cable for transmitting measurement signals is guided approximately along the vertical rotation axis in the area between the holding module and the slider.

11. The test head as claimed in claim 1, wherein the rotating member includes a plurality of permanent magnets on its outer circumference, the permanent magnets interacting with the magnetic field coils of a stator of the motor.

12. The test head as described in claim 1, wherein the motor comprises a stator and a rotor, each extending around a complete circle.

13. The test head as claimed in claim 1, wherein the lifting device is disposed on the rotating device and includes a linear motor for moving the holding module.

14. The test head as described in claim 1, wherein a moving wheel of a linear motor is formed on the slider for moving the slider.

15. The test head as claimed in claim 1, wherein the test head includes a camera for detecting a test tip of a test probe.

16. A device for testing a printed circuit board comprising at least two conductors, wherein at least one test head as described in any one of claims 1 to 14 is movably disposed on each of the at least two conductors.

17. The finger tester as described in claim 16, wherein the finger tester is used to test an unassembled printed circuit board.

18. The finger tester as described in claim 16, wherein each wire is formed from a piece of stone.

19. A method for testing a printed circuit board, wherein a finger tester as described in any one of claims 16 to 18 is used, wherein after a rotational movement of one of the rotating arms, the time for waiting for the corresponding rotating arm to swing inward until it contacts a corresponding contact point of a printed circuit board under test is substantially no more than 5 ms.

20. The method as described in claim 19, wherein the method is used to test an unassembled printed circuit board.

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