Contact head for an electrical test device, test device

Abstract

Contact head (6) for an electrical test device (1) for the electrical testing of substrates having electrical contact points, comprising at least two guide plates (13, 14) arranged relative to each other by a spacer (15) and each having several guide openings (16) that are at least substantially aligned with each other for receiving pin-shaped contact elements (8) and being aligned relative to each other by a centering device (20), wherein the centering device (20) has four centering pins (19) which are slidably mounted in an elongated hole (23) extending to a center (Z) of the contact head (6) in at least one of the guide plates (13, 14), and wherein the centering pins (19) are each held in a centering opening (18) of the spacer (15), characterized in thatthat the centering openings (18) each have only one guide surface (21) oriented at least substantially parallel to a radial (R) with respect to the center (Z).

Description

[0001] The invention relates to a contact head for an electrical testing device for the electrical testing of substrates having electrical contact points, in particular electrical conductors and / or electrical / electronic components, with at least two guide plates arranged parallel to each other by a spacer and each having several guide openings that are at least substantially aligned with each other for receiving pin-shaped contact elements and being aligned to each other by a centering device, wherein the centering device has four centering pins which are slidably mounted in each of the elongated holes extending to a center of the contact head in at least one of the guide plates, and wherein the centering pins are each held in a centering opening of the spacer.

[0002] Furthermore, the invention relates to an electrical testing device for the electrical testing of substrates that have electrical conductors and / or electrical / electronic components.

[0003] Electrical test equipment of the type mentioned above serves to electrically contact a test specimen or substrate with its electrical conductors and / or components in order to test the functionality of the substrate. The test equipment establishes electrical connections to the substrate by, on the one hand, contacting the substrate or its electrical conductors or electrical contact points, and on the other hand, by providing electrical contacts that are connected to a test system. This allows the test system to supply electrical signals to the test specimen via the test equipment in order to perform functional tests such as resistance measurements, current and voltage measurements, or similar operations.Because the substrates to be tested, such as wafers, printed circuit boards, or solar cells, are often extremely small components or components with a high density of electrical contact points, contact elements with small dimensions are necessary to achieve a high scanning rate or contact rate in a small space. Typically, the guide openings in the guide plates are arranged according to the electrical contact points on the test specimen, so that the contact elements are positioned accordingly.

[0004] Because different ambient and / or test temperatures may be present during the test, it is necessary to ensure that thermally induced changes in the length of the test equipment do not cause the positioning of the contact elements relative to the electrical contact points on the test specimen or the substrate to deviate, which would prevent the test from being carried out successfully. It is therefore known to provide centering devices that allow for thermal expansion clearance in the test equipment such that any displacement of the contact elements due to temperature-related changes in quantity is minimized.

[0005] For example, German patent application DE 10 2004 023 987 A1 discloses an electrical testing device with a centering device that, with respect to the center of the testing device or the contact head (i.e., the center in a plane parallel to the guide plates), allows only radial temperature variation, i.e., variation towards or away from the center. This radial alignment to the center ensures that, overall, minimal offset occurs during temperature-induced quantity changes, because length changes in the respective plate cannot accumulate across the entire width of the respective guide plate.

[0006] The centering device features several centering pins that are attached to the spacer in centering openings and sit in elongated holes in the guide plates, with the elongated holes oriented radially to the center along their longitudinal axis. To ensure flawless operation, high tolerance requirements must be met for the centering pins, elongated holes, and centering openings. The centering openings are designed as bores, i.e., with a circular contour, which necessitates tight manufacturing tolerances to guarantee reliable centering operation over the long term.

[0007] Furthermore, an electrical testing device is known from the patent application DE 10 2006 054 734 A1, comprising a testing machine into which a contact device serving for the contacting of a test object can be inserted, wherein a centering device allowing only radial temperature compensation play is provided for the central alignment of the contact device and the testing machine relative to each other.

[0008] The invention is based on the objective of creating a contact head or a testing device of the type mentioned above that allows an advantageous radial thermal expansion clearance, but can be manufactured cost-effectively and allows for larger manufacturing tolerances.

[0009] The problem underlying the invention is solved by a contact head with the features of claim 1 or by a testing device with the features of claim 10. The contact head according to the invention has the advantage that the centering pins are held or mounted in an optimized manner with respect to their function, so that, on the one hand, the radial thermal expansion clearance is ensured in every case, and, on the other hand, the contact head can be manufactured cost-effectively and with lower tolerance requirements. According to the invention, this is achieved by the fact that the centering openings each have only one guide surface that is aligned at least parallel to the radial axis.In contrast to the centering openings known from the prior art, the invention provides that each centering opening has a single guide surface that is aligned at least parallel to a radial line passing through the center of the contact head. Because each of the four centering openings of the spacer, which is also plate-shaped, has only one such guide surface aligned at least parallel to the radial line, a clear arrangement of the centering pins in the centering openings is ensured, allowing for temperature-related changes in size without compromising the centering function.This means that during the manufacturing of the guide plates, only the tolerances of the single guide surface of each centering opening need to be precisely maintained, while the remaining contour of the respective centering opening can be machined less precisely and therefore more cost-effectively. The centering pins, held firmly in the centering openings, then slide within the respective elongated hole to compensate for temperature-related dimensional changes.

[0010] According to a preferred embodiment of the invention, the guide surfaces extend along the radials. This means that the guide surfaces are not only aligned parallel to the radials, but also run precisely along them. This ensures that the centering pins are guided along the radials not with their center or central axis, but with their outer circumference. This guarantees precise guidance of the centering pins or guide plates on the centering pins, while preventing over-guidance by providing only one such guide surface at each centering opening.

[0011] Preferably, each centering opening has an auxiliary guide surface oriented at least substantially perpendicular to the guide surface. This allows the guide surface and the auxiliary guide surface to form a kind of guide prism or triangle, which reliably guides and aligns the respective centering pin. While the guide surfaces preferably run exactly along the radials, the arrangement of the auxiliary guide surfaces is less critical and can be subject to larger tolerances, ensuring reliable positioning and alignment of the guide plates even at varying temperatures. Due to their perpendicular orientation, the auxiliary guide surfaces limit the maximum displacement of the guide plates relative to the centering pins, thus easily preventing incorrect assembly.

[0012] Furthermore, it is preferably provided that the auxiliary guide surfaces are formed at a radially inner end of the respective guide surface. These auxiliary guide surfaces are ultimately located between the centering pins and the center of the respective guide plate or contact head. Advantageously, the auxiliary guide surfaces are positioned radially inward to such an extent that any expected temperature variation between the guide plates can be reliably compensated for or balanced without generating mechanical stresses in the guide plate. Because the auxiliary guide surfaces do not serve a joining function, their design and tolerance accuracy are of secondary importance.

[0013] Furthermore, it is preferably provided that the centering openings are square, rectangular, triangular, or circular except for the guide surface and auxiliary guide surface. This makes the respective centering opening simple, quick, and cost-effective to manufacture. For example, it is provided that the respective centering opening is initially formed by drilling and then completed by electrical discharge machining (EDM), in particular wire EDM, of the guide surface and, if applicable, the auxiliary guide surface, so that the respective centering opening is circular except for the guide surface and auxiliary guide surface. This leaves a circular section of the centering opening connecting the guide surface and auxiliary guide surface. It is also conceivable to form the centering opening oval except for the guide surface and, if applicable, the auxiliary guide surface.Alternatively, the respective centering opening is designed to be square, rectangular or triangular, with one of the side surfaces forming the guide surface and an adjoining side surface forming the auxiliary guide surface.

[0014] According to a preferred embodiment of the invention, exactly four centering pins are provided. This results in advantageous and unambiguous guidance and support of the guide plates or centering pins, which ensures unambiguous alignment and thermal compensation movement.

[0015] In particular, it is provided that two of the centering openings are arranged diametrically opposite each other with respect to the center, so that the guide surfaces lie on a common straight line passing through the center. This ensures a particularly reliable and unambiguous arrangement and alignment of the guide plates and the guide openings for the contact elements arranged / formed in the guide plates. Furthermore, the advantageous alignment and arrangement of the guide surfaces reduces or eliminates the tolerance requirements in the manufacturing of the respective centering pin.

[0016] Furthermore, it is preferably provided that the centering pins are held in the respective centering opening by a radial or lateral pressure screw, in particular by at least one setscrew, which radially applies a compressive force to the respective centering pin and in particular presses against the guide surface and / or the respective auxiliary guide surface, in a frictionally and positively locking manner. This results in simple assembly and unambiguous positioning of the centering pins in the centering openings.

[0017] Preferably, the centering pins are also slidably mounted in elongated holes of both guide plates, so that the advantageous centering function or temperature clearance function benefits both guide plates.

[0018] According to a first embodiment, the centering pins can each be formed in one piece, extending from one guide plate, through the entire spacer, to the other guide plate and through it. Alternatively, the centering pins can be formed in two parts, with a first pin part projecting into the elongated hole of one guide plate and the second pin part, which is aligned with the first pin part, projecting into an elongated hole of the other guide plate to ensure the centering of the guide plates relative to each other. Two of the pin parts can be held in the same centering opening by a pressure screw each, or they can be held in two different centering openings.

[0019] Furthermore, it is preferably provided that the guide plates are made of a ceramic material and the spacer is made of metal. This results in different thermal expansion behaviors of the guide plates and spacer relative to each other, which, however, is reliably compensated for or influenced by the advantageous centering device in such a way that the arrangement of the contact elements, which are designed in particular as contact pins or contact needles, is ensured as described above.

[0020] The electrical testing device with the features of claim 10 is characterized by the contact head according to the invention. This results in the advantages already mentioned.

[0021] Further advantages and preferred features and combinations of features will become apparent in particular from the above description and from the claims. The invention will now be explained in more detail with reference to the drawings. Fig. 1. An electrical test device in a simplified representation, Fig. 2 guide plates of a contact head of the test device, Fig. 3 the contact head according to a known embodiment, Fig. 4 an advantageous embodiment of the contact head in a schematic representation and Fig. 5 a detailed view of the advantageous embodiment.

[0022] Fig. Figure 1 shows a schematic cross-section of an electrical test device 1, which is designed to electrically contact a substrate 2 having a plurality of electrical contact points. The substrate 2 is, for example, configured as a wafer 3, printed circuit board, or solar cell and can be placed on a support 4, in particular the test device 1. The support 4, also referred to as a chuck, is designed such that it can be cooled or heated, preferably by integrating a cooling device and / or a heating device into or arranging it on the support 4. This makes it possible to expose the substrate 2 to different temperatures during testing in order to determine its functionality even at different temperatures.For contacting the substrate 2, the test device 1 has a so-called test card 5, which, for carrying out the test, has a contact head 6 and a connection device 7. The contact head 6 carries a plurality of longitudinally displaceable, pin-shaped contact elements 8, which are aligned parallel to each other. The contact elements 8 each have one end facing the carrier 4 or the substrate 2, respectively. The other end of the contact elements 8 is connected to the connection device 7.

[0023] The connection device 7 is designed as a multilayer printed circuit board 9, which has a plurality of electrically conductive conductor tracks. At their ends corresponding to the contact head 6, the conductor tracks have contact surfaces 11, which can be touch-contacted by the contact elements 8. At their radially extending ends pointing away from the contact head 6, the conductor tracks 10 each have a connection surface 12, which can be connected to a test system (not shown) via cable connections (not shown).

[0024] The connection device 7 thus forms a conversion device that translates the very close spacing of the very small contact surfaces 11 via the conductor tracks 10 into larger spacings between the contact surfaces 13, so that the contact surfaces 11 can be more easily electrically contacted, and wherein the arrangement of the contact surfaces 11 corresponds to the arrangement of the pin-shaped contact elements 8 on a close grid. The size of the contact surfaces 11 is selected such that reliable touch contact can be achieved by the contact elements 8, while the size of the connection surfaces 12 is selected such that simple electrical contact 11, for example by connecting cables and solder joints, is ensured.

[0025] During the testing of the substrate 2, the connection device 7 moves towards the carrier 4 and / or the carrier 4 moves towards the connection device 7 in the axial direction of the contact elements 8, so that the ends or end faces of the contact elements 8 contact the contact surfaces of the substrate 2 on one side and the contact surfaces 11 on the other, thus establishing an electrical connection from the substrate 2 to the connection device 7. If the contact elements 8 are preferably designed as hinged wires, they can spring back laterally and thereby reliably ensure proper contact at all contact points. To ensure that sufficient force can be exerted on the contact elements without the circuit board 9 deforming under the load, a support plate 17 is provided, as indicated by an arrow in Fig. 1 shown.

[0026] For guiding and holding the contact elements 8, the contact head 6 has two guide plates 13, 14 arranged spaced apart from each other and parallel to each other. The guide plates 13, 14 are aligned with each other by a spacer 15.

[0027] Fig. Figure 2 shows, in a simplified perspective view, the two guide plates 13, 14, which are arranged parallel to each other. Each guide plate 13, 14 has a plurality of guide openings 16, which are designed and arranged on the guide plates 13, 14 such that a contact element 8 can be guided through two aligned or offset guide openings 16 of the two guide plates 13, 14 and is thereby guided by the guide plates and preferably held by friction. According to the Fig. In the embodiment shown in Figure 2, only four guide openings 16 are depicted in each of the guide plates 13, 14; however, the guide plates 13, 14 actually have a large number of guide openings 16. It can be seen that for each guide opening 16 in the guide plate 13, a corresponding guide opening 16 is formed in the guide plate 14. The distance between the guide plates 13, 14 is advantageously designed to allow the contact elements 8 to flex laterally or spring back during the test, as described above.

[0028] While the guide plates 13, 14 are made of ceramic, the spacer 15 is made of steel. This means that, due to their different coefficients of thermal expansion, the guide plates 13, 14 and the spacer 15 may behave differently when the temperature changes. In particular, the guide plates 13, 14 may expand in their respective planes due to temperature changes, causing the contact elements 8, which are held in the guide openings 16, to move along with the guide plates 13, 14. This, in turn, can lead to the contact elements 8 no longer contacting the contact surfaces 11 or the contact points of the substrate 2, thus compromising the reliability of the test. It is therefore already known to provide a centering device 20, which forms a central center for the guide plates 13, 14.

[0029] Fig. Figure 3 shows such a centering device 20 in a perspective view of an embodiment. The guide plates have elongated holes 23 extending radially towards the center Z of the respective guide plate 13, 14. Centering pins 19, mounted in the spacer 15, each project into one of the elongated holes 23 and are designed to be longitudinally displaceable within the elongated holes 23, i.e., along an imaginary radial R to the center Z in the respective elongated hole 23. If temperature-related changes in size occur, the guide plates 13, 14 can only expand or contract radially in the plane, starting from the center Z, thus ensuring that the guide openings 16 are only minimally affected in their position by thermal expansion.Because this is done starting from the center Z, it is ensured that the length expansions do not add up over the entire width or length of the respective guide plate 13, 14.

[0030] Fig. Figure 4 shows the contact head 6 with one of the advantageous centering devices 20. Fig. Figure 4 shows the centering device 20 in a schematic top view of the spacer 15. The spacer has several centering openings 18. According to the advantageous embodiment, each centering opening 18 has a guide surface 21 that runs not only parallel but also precisely along the respective radials R. Perpendicular to, or alternatively at an acute angle to, the guide surface 21, an auxiliary guide surface 22 is formed, such that the guide surface 21 and the auxiliary guide surface 22 together form a triangular or prismatic centering contour.

[0031] Fig. Figure 5 shows an enlarged representation of one of the centering openings 18, which are located in Fig. Figure 4 shows the centering device 20 in an enlarged detail view, formed in the spacer 15 at the top left. The guide surface 21 and the auxiliary guide surface 22 are visible, which, according to the present embodiment, form an angle α = 90° between them, with the guide surface 21 lying on the radial R to the center Z. According to the present embodiment, the guide surface 21 and the auxiliary guide surface 22 are of equal length and transition into a circular arc contour of the centering opening 18, which has the contour of the centering opening 18.

[0032] To produce the centering openings 18, it is specifically provided that the centering openings 18 are manufactured by electrical discharge machining (EDM), in particular wire EDM, of the guide surface 21 and the auxiliary surface 22 in the spacer 15. Because only the guide surface 21 has an important function for centering and tolerance compensation, only this surface requires attention to maintaining tight tolerances. The remaining contour of the centering opening 18 is less relevant because, normally, none of the centering pins 19 bear against the remaining contour of the respective centering openings 18. Because the centering opening 18 does not have parallel guide surfaces and thus always has a distance and dimension, the opposite side of the respective guide surface 21 is insignificant for guiding the centering pin 19, so that correspondingly large tolerances can be taken into account during manufacturing. Fig. Figure 5 also shows, with dashed lines, the orientation of the elongated hole 23 assigned to the centering opening 18.

[0033] According to the previous embodiment, exactly four such centering openings 18 are provided, with each pair of centering openings 18 being diametrically opposite each other to the center Z of the spacer 15 or the contact head 6. Because the guide surfaces 21 run along the radials R, the tolerances do not add up, with the result that the manufacturing tolerances of the centering pins 19 can also be larger than before. The arrangement and design of the auxiliary guide surfaces 22 need be less precise than before, and a precise right angle between the auxiliary guide surfaces 22 and the respective associated guide surfaces 21 is not required. Rather, angles α deviating from a right angle are also permissible.The size of the respective centering opening 18 must simply be larger overall than the diameter of the respective centering pin 19 in order to allow the mounting of the respective centering pin 19.

[0034] During assembly, the centering pins 19 are fastened to the spacer 15, in particular by means of lateral pressure screws 24, especially by means of set screws, such that they are subjected to a fastening force towards each other in the direction of the center, as shown in Fig. 4 through arrows and in Fig. 5 shown by dashed lines. This presses the centering pins 19 against the respective guide surface 21, thus ensuring simple alignment during assembly.

[0035] If temperature stresses or temperature-related changes in length occur in one of the guide plates 13, 14, the guide plates 13, 14 can expand radially as before, without the guide openings 16 and thus the contact elements 8 deviating too far from a predetermined position. The alignment of the guide openings 16 relative to each other is also maintained in such a way that sufficient holding force is ensured, particularly for frictional engagement of the contact elements 8.

Claims

[1] Contact head (6) for an electrical testing device (1) for the electrical testing of substrates having electrical contact points, with at least two guide plates (13, 14) which are arranged relative to one another by a spacer (15) and each have a plurality of at least substantially aligned guide openings (16) for receiving pin-shaped contact elements (8) and are aligned relative to one another by a centering device (20), wherein the centering device (20) has four centering pins (19) which are each displaceably mounted in an elongated hole (23) extending towards a center (Z) of the contact head (6) in at least one of the guide plates (13, 14), and wherein the centering pins (19) are each held in a centering opening (18) of the spacer (15), characterized bythat the centering openings (18) each have only one guide surface (21) aligned at least substantially parallel to a radial (R) - with respect to the center (Z). [2] Contact head according to claim 1, characterized by that the guide surfaces (21) each run along the radial (R). [3] Contact head according to one of the preceding claims, characterized by that the centering openings (18) each have an auxiliary guide surface (22) aligned at least substantially perpendicular to the guide surface (21). [4] Contact head according to one of the preceding claims, characterized by that the respective auxiliary guide surface (22) is formed / arranged at a radially inner end of the respective guide surface (21). [5] Contact head according to one of the preceding claims, characterized bythat the centering openings (18) are square, rectangular, triangular or circular except for the guide surface (21) and the auxiliary guide surface (22). [6] Contact head according to one of the preceding claims, characterized by that two of the centering openings (18) are arranged diametrically opposite each other with respect to the center (Z). [7] Contact head according to one of the preceding claims, characterized by that the centering pins (19) are slidably mounted in elongated holes (23) of both guide plates (13,14). [8] Contact head according to one of the preceding claims, characterized by that the centering pins (19) are fastened in the centering openings (18) by radial pressure screws (24), in particular grub screws. [9] Contact head according to one of the preceding claims, characterized bythat the guide plates (13,14) are made of a ceramic material and the spacer (15) is made of metal. [10] Electrical testing device (1) for electrically testing substrates (2) having electrical conductors and / or electrical / electronic components, with a connection device (7) and a contact head (6), characterized by the design of the contact head (6) according to one of claims 1 to 9.

Images