Probe for electrical testing in a defect detection system

Abstract

The fine electric probe can provide fine fine pitch applications in devices such as smart watches and smart phones. The fingers are positioned on the substrate. The substrate has a recess that allows the fingers to flex. The substrate and the fingers are positioned in an assembly. The assembly has a recess that allows the substrate to flex.

Description

Technical Field

[0001] The present disclosure relates to probes for electrical testing. Background Art

[0002] Multi-electrode probes are typically used to determine one or more electrical parameters of a test sample. When performing these measurements, the multi-electrode probe contacts the sample surface to make electrical contact. Liquid crystal display (LCD) panels incorporate liquid crystals that exhibit electric field-dependent light modulation properties. They are often used to display images and other information in a variety of devices, including fax machines, laptop screens, phones, tablet computers, watches, and large-screen high-definition televisions. Active matrix LCD panels are complex layered structures that may include several functional layers, including polarizing films; thin-film transistor (TFT) glass substrates incorporating thin-film transistors, storage capacitors, pixel electrodes, and interconnects; oriented films made of polyimide; and actual liquid crystal materials incorporated into plastic / glass spacers to maintain appropriate LCD unit thickness. LCD panels are manufactured in a clean room environment under highly controlled conditions to maximize yield. Despite this, many LCDs are discarded due to manufacturing defects.

[0003] To increase the yield of complex electronic devices, such as LCD panels, various inspection stages are performed to identify various defects that may occur during various stages of the manufacturing process. These inspection stages may be performed between manufacturing stages or after the entire manufacturing process is completed. An example of an inspection process is testing TFT arrays for LCD and OLED displays for electrical defects. Various inspection devices are used to perform the testing.

[0004] Electrical inspection systems typically require that the device under test (DUT) be driven by electrical signals or patterns that facilitate detection of defects. These signals are transmitted from a pattern generator subsystem to the DUT using a structure carrying probe fingers that physically contact contact pads located around the active area of ​​the DUT.

[0005] Previous electrical inspection techniques used pogo pins, which are spring-preloaded plungers. The size of these pins cannot be reduced below a few hundred microns in diameter. This size does not allow for reductions in the pitch and size of the probes. Additionally, the pogo pins are mechanically mounted on a machined plastic carrier. Plastic machining is limited in accuracy and resolution.

[0006] Therefore, new systems and technologies are needed. Summary of the invention

[0007] In a first embodiment, a probe is disclosed. The probe includes: a substrate defining a contact surface and a substrate recess at a distal end of the substrate; a plurality of fingers disposed on the contact surface; and an assembly configured to hold the substrate and the fingers. The fingers extend beyond the distal end of the substrate and span the substrate recess. When the fingers extend across the substrate recess, the fingers are spaced apart from the substrate. The assembly defines an assembly recess. The substrate is spaced apart from the assembly in the assembly recess.

[0008] The fingers may be made of BeCu. The substrate may be ceramic.

[0009] The assembly may define a hole. The probe may include a limiter disposed in the hole. The limiter is configured to extend into the assembly recess and limit deflection of the substrate. The limiter may be made of metal.

[0010] The probe may include an electrical connector in electrical communication with the plurality of fingers. The electrical connector is disposed in the assembly.

[0011] The probe may include at least one spring disposed in the assembly recess between the substrate and the assembly.

[0012] The substrate recess may extend from the contact surface by 25 μm to 100 μm into the substrate.

[0013] The fingers may extend 50 μm to 200 μm beyond the distal end of the substrate.

[0014] Each of the fingers may have a width from 10 μm to 20 μm.

[0015] The fingers may have a thickness extending from 30 μm to 150 μm from the contact surface.

[0016] Each of the fingers may have a conical or frustoconical cross-section having a first outer surface and a second outer surface opposite the first outer surface. The second outer surface is wider than the first outer surface.

[0017] A distance between the finger and the substrate in the substrate recess may be greater than zero and less than 1 mm.

[0018] In a second embodiment, a method is provided. The method includes contacting an electrical device with a probe, the probe including a plurality of fingers (e.g., BeCu) disposed on a substrate. The fingers are flexed within a substrate recess of the substrate. The fingers and the substrate are flexed within an assembly recess of an assembly configured to hold the fingers and the substrate. Measurements of an electrical test of the electrical device are received using the probe.

[0019] The method may include applying tension between the substrate and the assembly using at least one spring disposed in a recess of the assembly between the substrate and the assembly.

[0020] The fingers may flex 25 μm to 100 μm across the substrate recess.

[0021] The substrate can flex up to 50 μm across the assembly recess.

[0022] The electrical device may be a screen or a flat panel display. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a more complete understanding of the nature and purpose of the present disclosure, reference should be made to the following detailed description in conjunction with the accompanying drawings, in which:

[0024] Figure 1A An embodiment of a probe including components but without an assembly is shown;

[0025] Figure 1B Show components with assembled parts;

[0026] Figure 1C exhibit Figure 1B a reverse view of the assembly in;

[0027] Figure 2A is a side cross-sectional view of an embodiment of a probe;

[0028] Figure 2B yes Figure 2A Front view of the probe in;

[0029] Figure 2C yes Figure 2A A top perspective view of a probe;

[0030] Figure 2D yes Figure 2A A cross-sectional view of the probe fingers and substrate in FIG.

[0031] Figure 3 is a top view of a finger extending beyond a substrate;

[0032] Figure 4 is an embodiment of a finger cut from a foil on a substrate;

[0033] Figure 5 is an embodiment of a finger-like object;

[0034] Figure 6 showing the fingers as magnification increases;

[0035] Figure 7 A top view showing an embodiment of a substrate;

[0036] Figure 8 is a view of a cavity in a substrate; and

[0037] Fig. 9 is a flow chart of an embodiment of a method according to the present disclosure. DETAILED DESCRIPTION

[0038] Although the claimed subject matter will be described in terms of certain embodiments, other embodiments, including embodiments that do not provide all of the benefits and features set forth herein, are also within the scope of the present disclosure. Various structural, logical, process step, and electronic changes may be made without departing from the scope of the present disclosure. Accordingly, the scope of the present disclosure is defined solely by the appended claims.

[0039] Embodiments disclosed herein provide fine electrical probes (e.g., 20 μm) that enable fine pitch electrical measurement applications for devices such as smart watches and smartphones. Smart watches, smartphones, and other screens or tablets can benefit from probes with finer tips. The size, shape, and flexure of the fingers and associated components can improve accuracy and resolution compared to previous designs.

[0040] Figures 1A to 1C and Figures 2A to 2D An embodiment of a probe 100 is shown. The probe 100 includes a substrate 101 defining a contact surface 106 and a substrate recess 107 at a distal end 107 of the substrate 101. The substrate 101 may be made of ceramic, such as Al2O3, AlN, BeO, glass, silicon dioxide, or other insulating materials.

[0041] The fingers 102 are disposed on the contact surface 106 of the substrate 101. The fingers 102 extend beyond the distal end 111 of the substrate 101 and span across the substrate recess 107. When the fingers 102 extend across the substrate recess 107, the fingers 102 are spaced apart from the substrate 101.

[0042] In an example, the fingers 102 are made of BeCu. BeCu provides improved properties in terms of fatigue resistance, wear resistance and weldability. The fingers 102 may be made of other materials, such as high hardness steel coated with electroless nickel.

[0043] The fingers 102 may be processed by femtosecond laser or chemically etched. In an example, a 50 to 100 μm thick BeCu foil is used to form a plurality of fingers 102, each finger 102 having a width of 10 μm or more and a length of several hundred microns. The fingers 102 may extend in a fan shape, with the width increasing as it extends, such as Figure 5 As shown in .

[0044] In an example, the fingers 102 are glued to the substrate 101 before micromachining. Figure 4 The finger 102 is shown being formed. Figure 4 Some foils have been removed. The glued and micro-machined sandwich structure including fingers 102 and substrate 101 has protruding fine fingers 102 on one end and the same number of wider pads on the other end of substrate 101. These pads can be used as part of the electrical connections.

[0045] The assembly 103 is configured to hold the substrate 101 and the fingers 102. The assembly 103 defines an assembly recess 108. The substrate 101 is spaced apart from the assembly 103 in the assembly recess 108. The assembly recess may have a depth configured to allow the substrate 101 to angularly deflect by 3° to 5° or 3° to 7°. The substrate 101 may be positioned in the assembly recess 108 at this dive angle in a downward manner from the assembly 103, which is shown in FIG. Figure 2A When the finger 102 is pressed during testing, the distance between the substrate 101 and the assembly 103 in the assembly recess 108 may be close to zero or even zero.

[0046] The substrate 101 may be soldered to the electrical connector 105, and the electrical connector 105 may be connected to the assembly 103. For example, the substrate 101 and the electrical connector 105 may be bolted to the assembly 103. When the substrate 101 is connected to the assembly 103, it may include the fingers 102.

[0047] In an example, assembly 103 may be made of anodized aluminum, but other materials are possible. The anodized aluminum may be 6061-T6 aluminum.

[0048] The assembly 103 may define a hole 109 through its body. The hole 109 may extend from the upper surface of the assembly 103 to the assembly recess 108. The limiter 104 may be disposed in the hole 109. The limiter 109 is configured to extend into the assembly recess 108 and limit the deflection of the substrate 102. The limiter 109 may prevent excessive deflection of the substrate 101 and the fingers 102.

[0049] The restrictor 104 may be made of metal, ceramic or plastic. The restrictor 104 is connected to the assembly 103, for example by gluing, welding or mechanically fixing the components.

[0050] The electrical connector 105 may be in electrical communication with the fingers 102. The electrical connector 105 may be disposed in the assembly 103. In an example, the fingers 102 may be soldered to a printed circuit board (PCB) that serves as the electrical connector 105, which electrically connects the probe sandwich structure (i.e., the fingers 102 and the substrate 101) to the measurement tool. A hot bar technique may be used for soldering.

[0051] The flexure travel may be related to the maximum stress in the finger 102. The connection between the finger 102 and the electrical connector 105 may be configured to operate when the finger 102 is at maximum stress. If the extension exceeds the maximum stress, the finger 102 may break or bend.

[0052] The contacts between the PCB and the sandwich structure (ie, fingers 102 and substrate 101) in the electrical connector 105 can also serve as flexures, allowing the sandwich structure to be moved in the Z direction (see FIG. Figure 2A and 2D ) deflects by about 1000 μm. For example, see Figure 2A The diving angle α in .

[0053] At least one spring 110 may be used in the probe 100. In an embodiment, two springs 110 are disposed between the substrate 102 and the assembly 103 in the assembly recess 108. The at least one spring 110 creates a preload on the deflected sandwich structure (i.e., the finger 102 and the substrate 101) that can ensure a predefined probing force and also provide a desired contact resistance. The spring 110 may have a force from 0.1 to 0.3 N, but other values ​​are also possible.

[0054] In an example, substrate recess 107 extends from contact surface 106 into substrate 101 to a depth of 25 μm to 100 μm. For example, a depth of 50 μm to 100 μm may be used. In an example, a distance between a surface of finger 102 and an opposing surface of substrate 101 in substrate recess 107 is greater than zero and less than 1 mm. This may refer to when there is no flexure of the finger.

[0055] Figure 3 is a top view of fingers 102 extending beyond substrate 101. Fingers 102 may extend 50 μm to 200 μm beyond distal end 107 of substrate 101. In an example, fingers 102 extend about 100 μm beyond distal end 107 of substrate 101. The final width of individual fingers 102 contacting an electrical device may be from 15 to 50 μm.

[0056] Figure 6The fingers 102 are shown at increasing magnifications. Each of the fingers 102 may have a width from 10 μm to 300 μm. For example, the width may be from 10 μm to 20 μm. Each of the fingers may have a height (e.g., thickness extending from the contact surface 106) from 30 μm to 150 μm. The geometry of the fingers 102 may be adjusted depending on the height and width to accommodate stress, deflection, and life of the fingers. This may reduce the likelihood of breakage.

[0057] There may be two regions of deflection for the finger 102. First, the fine finger 102 may be limited to 50 μm to 100 μm of deflection by the position in the substrate recess 107. Second, the portion of the finger 102 connected to the electrical connector 105 may be limited in deflection using the assembly 103 and the limiter 104. The portion of the finger 102 connected to the electrical connector 105 may move 500 μm to 1000 μm. The portion of the finger 102 that extends beyond the distal end 111 of the substrate 101 may deflect approximately 200 μm.

[0058] like Figure 6 As shown in FIG. 1 , each of the fingers 102 has a conical or frustoconical cross-section with a first outer surface and a second outer surface opposite the first outer surface. The second outer surface (i.e., Figure 6 The bottom of the first outer surface (i.e., Figure 6 width at the top of the

[0059] Laser processing typically creates a cone shape in the finger 102 due to its optical numerical aperture (N / A). The tip width of the finger 102 can be small enough to touch the pad of the device. The entire finger 102 can be as wide as possible within the allowed pitch to avoid lateral movement, which is provided at least in part by the tapered shape.

[0060] Figure 7 A top view of an embodiment of substrate 101 is shown. The angle to the rectangular portion of substrate 101 may be about 45°. The width of the substrate distal end where the fingers extend may be from 2 mm to 5 mm wide. Substrate 101 may have a similar shape to a fan-out foil, which may reduce weight.

[0061] Figure 8 is a view of a recess in the substrate. Each finger may be positioned opposite a recess machined into the substrate. One or more micromachined ("engraved") recesses in the substrate 101 may limit local deflection of the finger 102. The recess may act as a barrier, not allowing the finger 102 to deflect after contact with the inspected glass. For a 1000 μm protruding finger 102, the engraved recess may limit deflection to a maximum of 50 μm.

[0062] Although Figure 8 Individual dimples are shown, but a single recess spanning the width of the finger may also be used.

[0063] Embodiments disclosed herein provide improved finger sizes for probes. Different geometries than existing pogo pins are possible. Life and contact resistance can be configured by controlling contact force. In examples, embodiments of probes disclosed herein can be consumable parts that can be replaced in the field.

[0064] Micro-machined fine finger probes offer advantages over previous designs. A single piece of foil can be used to form the fingers, which can provide a distribution pattern for the fine fingers from the fingers to the flexure and / or contact with the PCB. The fingers can also provide flexure and PCB contact. Under preload force, the overall ceramic movement on the flexure can be mechanically (adjustably) limited to 500 μm, which determines the contact resistance. Further reduction of the probe mass does not apply additional force to the fingers.

[0065] Fig. 9 2 is a flow chart of an embodiment of a method 200 that may use an embodiment of the probe 100. At 201, an electrical device is contacted with a probe comprising a plurality of fingers disposed on a substrate. The electrical device may be, for example, a screen or flat panel display. The fingers may be BeCu. At least one probe is mounted on a tool platform. The tool platform may include a beam that travels over the electrical device and may be moved farther and closer to the surface of the electrical device to make contact. When lowered, the fingers of the probe contact a conductor on the electrical device, which provides an electric field for inspection.

[0066] At 202, the fingers are flexed within a substrate recess of a substrate. At 203, the fingers and substrate are flexed within an assembly recess of an assembly configured to hold the fingers and substrate. Steps 202 and 203 may occur in any order or at least partially simultaneously. The fingers may flex 25 μm to 100 μm across the substrate recess. The substrate may flex up to 50 μm across the assembly recess.

[0067] In an example, the fingers 102 may deflect up to 100 μm (either collectively or individually to accommodate reduced pressure). The substrate 102 as a whole may deflect 500 μm to 1000 μm to allow for tool inaccuracies.

[0068] At 204, measurements of electrical testing of the electrical device are received using the probe. The measurements may be received by a processor for analysis. The processor may be part of a computer or another system.

[0069] Tension may be applied between the substrate and the assembly using at least one spring disposed between the substrate and the assembly in the assembly recess.

[0070] Although the present disclosure has been described with respect to one or more specific embodiments, it should be understood that other embodiments of the present disclosure may be made without departing from the scope of the present disclosure. Therefore, the present disclosure is considered to be limited only by the appended claims and reasonable interpretations thereof.

Claims

1. A probe comprising: a substrate defining a contact surface and a substrate recess at a distal end of the substrate; a plurality of fingers disposed on the contact surface, wherein the fingers extend beyond the distal end of the substrate and across the substrate recess, and wherein the fingers are spaced apart from the substrate when the fingers extend across the substrate recess; and An assembly configured to hold the substrate and the fingers, wherein the assembly defines an assembly recess, and wherein the substrate is spaced apart from the assembly in the assembly recess.

2. The probe of claim 1, wherein the fingers are made of BeCu. The probe according to claim 1 , wherein the substrate is ceramic.

4. The probe of claim 1, wherein the assembly defines a hole and further comprises a limiter disposed in the hole, wherein the limiter is configured to extend into the assembly recess and limit deflection of the substrate. The probe of claim 4 , wherein the limiter is made of metal.

6. The probe of claim 1, further comprising an electrical connector in electrical communication with the plurality of fingers, wherein the electrical connector is disposed in the assembly.

7. The probe of claim 1, further comprising at least one spring disposed between the substrate and the assembly in the assembly recess. 8 . The probe of claim 1 , wherein the substrate recess extends from the contact surface into the substrate by 25 μm to 100 μm.

9. The probe of claim 1, wherein the fingers extend 50 μm to 200 μm beyond the distal end of the substrate.

10. The probe of claim 1, wherein each of the fingers has a width from 10 μm to 20 μm.

11. The probe of claim 1, wherein the fingers each have a thickness extending from the contact surface from 30 μm to 150 μm.

12. The probe of claim 1, wherein each of the fingers has a conical or frustoconical cross-section having a first outer surface and a second outer surface opposite the first outer surface, wherein the second outer surface is wider than the first outer surface. 13 . The probe of claim 1 , wherein a distance between the finger and the substrate in the substrate recess is greater than zero and less than 1 mm.

14. A method comprising: contacting the electrical device with a probe comprising a plurality of fingers disposed on a substrate; flexing the finger within a substrate recess of the substrate; flexing the fingers and the substrate within an assembly recess of an assembly configured to hold the fingers and the substrate; and Measurements of electrical testing of the electrical device are received using the probe.

15. The method of claim 14, wherein the fingers are made of BeCu.

16. The method of claim 14, further comprising applying tension between the substrate and the assembly using at least one spring disposed in the assembly recess between the substrate and the assembly.

17. The method of claim 14, wherein the fingers flex 25 μm to 100 μm across the substrate recess.

18. The method of claim 14, wherein the substrate deflects at most 50 μm across the assembly recess.

19. The method of claim 14, wherein the electrical device is a screen.

20. The method of claim 14, wherein the electrical device is a flat panel display.

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