Image sensor chip test fixture and test method

Abstract

The invention provides a test fixture for testing an image sensor chip, and aims to solve the problems of poor imaging consistency, limited site layout and the like caused by stray light generated by reflection and refraction of light on the surface of a structural member in an existing structure. The through straight hole is formed in the structure between the light source and the lens, and the transparent light guide piece is embedded in the straight hole, so that illumination light is transmitted in a unique and stable path. The material and the shape of the light guide piece can be freely selected according to requirements so as to adapt to different spectral characteristics and light source positions. The light enters the dodging part and the lens system after being directionally transmitted by the light guide part, and the middle does not contact the surface of a surrounding structure, so that stray light is effectively prevented from being generated, and the illumination uniformity and imaging consistency of each test position are remarkably improved. Due to the fact that the light path is strictly limited, the scheme is not limited by the field angle of the lens any more, the site distance can be reduced, a plurality of test positions can be flexibly arranged, the number of testable points in unit area is increased, and therefore the test efficiency and the throughput capacity of a production line are improved. The probe card is simple in structure, convenient to process and high in adaptability, can be directly applied to an existing probe card system, and has good popularization value.

Description

Technical Field

[0001] This invention relates to the field of image sensors, and more particularly to an image sensor chip testing fixture and testing method. Background Technology

[0002] With the widespread application of high-performance image sensors across various industries, the requirements for testing accuracy, imaging consistency, and efficient multi-site simultaneous testing in the production process are increasing. In actual wafer inspection, a light source and probe card are typically used together, with a light-diffusing element uniformly projecting illumination light into the lens structure to ensure stable and controllable illumination for the image sensor under test. However, existing technologies still face several technical challenges in achieving this.

[0003] First, in existing optical path designs, to prevent illumination light from entering the lens's field of view, the optical path between the light source and the lens typically needs to avoid the field of view area to prevent unnecessary scattering and reflection of light entering the lens. However, the existing design still has significant shortcomings, especially when light shines on structural components. Differences in the surface material and color of the structural components can cause light reflection and refraction. Due to the presence of these stray lights, the light ultimately entering the lens loses uniformity, leading to fluctuations in image quality and affecting the consistency of test results. This is particularly pronounced when testing multiple sites simultaneously, as the differences in imaging effects between different sites become more significant, further exacerbating the consistency problem. Second, existing optical path designs are limited by the physical constraints of the lens's field of view, making it difficult to reduce the spacing between sites. This design limits the number of test points (TDs) that can be tested simultaneously, failing to meet the demands of high-density, high-throughput testing. In this situation, the site layout of the test fixture typically needs to increase the spacing to avoid light interference or reflection, thereby affecting image quality. However, the increased spacing between stations significantly limits the number of test points that can be covered in each test, reducing testing efficiency and lengthening the production cycle, which cannot fully meet the needs of efficient and large-scale testing in modern image sensor production.

[0004] Existing probe card optical path structures face problems such as stray light interference, limited field of view, and inflexible site layout spacing. There is an urgent need for a new solution that can optimize optical path design, improve imaging consistency, and support high-density, multi-point testing. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a test fixture for testing image sensor chips. The test fixture is characterized in that it includes: a light source, a light homogenizer, a lens assembly, and a light guide assembly located between the light source and the lens assembly. The light guide assembly has a through hole along the light path, and a transparent light guide element is disposed in the through hole, so that the test light first passes through the light guide element and then through the light homogenizer to enter the lens according to a set unique light path.

[0006] Furthermore, the light guide assembly has a through hole to accommodate the light guide element.

[0007] Furthermore, the light guide is made of a transparent material, and the light transmittance and transmission / absorption characteristics of the material for different wavelengths can be selected according to application requirements.

[0008] Furthermore, the shape of the light guide is not limited to a single shape; it can be cylindrical, square, or any shape designed according to the position of the light source and the requirements of the optical path.

[0009] Furthermore, the light guide provides a single, essentially non-reflective transmission path in the optical path, thereby avoiding stray light formed by reflection or refraction when light passes through the light guide assembly or structure, and improving the imaging consistency at each test chip.

[0010] Furthermore, by setting the light guide, the layout of the test chips is not limited by the field of view of the lens, thereby achieving a more flexible arrangement of test chip spacing and improving the testing efficiency of test points.

[0011] Furthermore, the material selected for the light guide has minimal impact on visible light transmission but exhibits absorption characteristics in the infrared band, which helps to suppress infrared-related stray light.

[0012] Furthermore, the present invention also provides a method for assembling the test fixture as described above, the assembly steps including: forming a through hole at the light guide component; selecting or preparing a transparent light guide with the required transmittance and wavelength response; embedding the light guide in the through hole; adjusting the relative position between the light guide, the light homogenizer, and the lens to ensure that the light path passes through the light guide and enters the lens in a unique manner.

[0013] Furthermore, the present invention also provides an image sensor chip testing method using the above-described test fixture, comprising: test light emitted by a light source is directionally transmitted through the light guide, then enters the lens through a light homogenizer to illuminate the chip under test, and the stray light generated by reflection / refraction of the light guide component or the surface of the structural component is reduced through the optical path structure, so as to improve the imaging consistency and test repeatability between different test chips.

[0014] This invention incorporates a transparent light guide within the existing component and replaces the multi-stepped holes in the prior art with through-holes, allowing illumination light to travel along a single and controllable path, significantly reducing reflection and refraction on the surface of the structural components. This effectively suppresses stray light caused by differences in the material and color of the structural components, significantly improving the imaging uniformity and consistency at each test point. With the light guide, the incident light no longer depends on the avoidance layout of the lens's field of view, allowing for more flexible test point arrangement and increasing the number of points that can be tested simultaneously per unit area, thereby increasing overall test throughput and reducing test cycle and manufacturing costs. Furthermore, the material and shape of the light guide are not strictly limited; different materials or arbitrary cross-sections such as cylinders and squares can be selected according to different light source wavelengths and transmittance requirements to achieve high transmittance of visible light while suppressing infrared components, further reducing the influence of infrared-related stray light and improving signal-to-noise ratio and measurement reproducibility. The structural modification is simple, easily implemented in existing probe card manufacturing processes, convenient for assembly and maintenance, does not introduce complex process steps or expensive components, has strong compatibility, and is suitable for various lens and light-diffusing element combinations. This invention not only fundamentally reduces stray light sources in the optical path, improving imaging quality and test consistency, but also significantly improves the efficiency of simultaneous multi-point testing by increasing the degree of freedom in layout. It has important practical value for improving the reliability, repeatability and overall efficiency of image sensor chip testing and production line efficiency. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a testing fixture for existing image sensors. Figure 2 This is a schematic diagram of a testing fixture for existing image sensors. Figure 3 This is a schematic diagram of an image sensor testing fixture according to an embodiment of the present invention; Figure 4 This is a schematic diagram of an image sensor testing fixture according to an embodiment of the present invention. Detailed Implementation

[0016] like Figure 1 As shown, the existing technology typically uses a test fixture that includes a light source 101, a light homogenizer 103, and a lens 104 for the image sensor module. A stepped light guide component 102 is disposed between the light source 101 and the lens 104. To ensure image uniformity, the optical path from the lens to the light source 101 needs to avoid the field of view; therefore, the opening of the light guide component 102 needs to be tapered, wider at the top and narrower at the bottom. Furthermore, light emitted from the light source 101 and illuminating the light guide component 102 is subject to reflection or refraction from the surface of the light guide component 102, and differences in the material or color of the light guide component 102 can easily generate stray light, ultimately affecting the imaging effect of the image sensor chip under test, resulting in poor test consistency. In addition, as... Figure 2As shown, due to the structural limitations of the cone-shaped light guide assembly 102, the spacing W1 between adjacent chips under test is relatively large, thus limiting the number of image sensor chips that can be tested simultaneously.

[0017] To address the technical problems existing in the prior art, this invention proposes an image sensor testing fixture and testing method, specifically as follows: Figure 3-4 As shown.

[0018] This embodiment replaces the existing multi-step conical aperture light guide component structure at the optical path with a through-hole light guide component 202, and embeds a transparent light guide component 202a within the through-hole. The light guide component 202a is made of a high-transmittance material, and the material selection is not strictly limited. It can be glass, high-transmittance organic materials, or other materials with corresponding optical properties, depending on the wavelength and transmittance requirements of the test light source. To suppress interference at specific wavelengths, materials with absorption capabilities in the infrared spectrum can also be selected. The cross-sectional shape of the light guide component 202a is also not limited; it can be cylindrical, square, or customized into an asymmetrical shape according to the relative position of the light source and the optical axis to optimize the directional performance of the incident light.

[0019] The light guide component 202a is fixed to the through hole of the light guide assembly 202 by press-fitting or optical-grade adhesive. Its end face can be treated with anti-reflective coating to reduce interface reflection, and its exterior can be sealed for easy cleaning and replacement. Light emitted from the light source first passes through the light guide component 202a, where it is confined to a single path. It then passes through the light homogenizer 203 and enters the lens 204 of the image sensor module located below the test fixture. Since the light no longer undergoes secondary reflection or refraction with surrounding structural components in this optical path segment, stray light caused by differences in the material or surface of the structural components can be significantly reduced, improving the uniformity of incident light and the consistency of imaging at each test position.

[0020] In addition, such as Figure 4 As shown, through the orientation effect of the light guide component 202a, the sensitivity of the optical path to the lens field of view is weakened, allowing for a smaller test station spacing W2. Adjacent test chips can be more compact and flexible, thus enabling the arrangement of more test points per unit area and improving test throughput and production line efficiency. This structural improvement is simple and easy to implement, compatible with existing manufacturing and assembly processes, and readily adaptable to existing probe cards, demonstrating good versatility and practical value.

[0021] Furthermore, the present invention also provides a method for assembling the test fixture as described above, the assembly steps including: forming a through hole at the light guide component; selecting or preparing a transparent light guide with the required transmittance and wavelength response; embedding the light guide in the through hole; adjusting the relative position between the light guide, the light homogenizer, and the lens to ensure that the light path passes through the light guide and enters the lens in a unique manner.

[0022] Based on this, the present invention also provides an image sensor chip testing method using the above-described test fixture. The testing method includes: test light emitted by a light source is directionally transmitted through the light guide, then enters the lens through a light homogenizer to illuminate the chip under test, and the stray light generated by reflection / refraction of the light guide component or the surface of the structural component is reduced through the optical path structure, so as to improve the imaging consistency and test repeatability between different test chips.

[0023] This invention replaces the multi-stage stepped holes in the light guide components of existing test fixtures with through straight holes and incorporates a transparent light guide within the original components. This allows the illumination light to travel along a single and controllable path, significantly reducing reflection and refraction on the surface of the structural components. This effectively suppresses stray light caused by differences in the material and color of the structural components, significantly improving the uniformity and consistency of imaging at each test point. Using the light guide provided by this invention, the incident light no longer depends on the avoidance layout of the lens's field of view, allowing for more flexible test point arrangement and increasing the number of points that can be tested simultaneously per unit area. This improves overall test throughput and reduces test cycle time and manufacturing costs.

[0024] It should be understood that the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document indicates that the preceding and following related objects are in an "or" relationship. "Multiple" in the embodiments of this application refers to two or more. The descriptions such as "first," "second," etc., appearing in the embodiments of this application are only for illustration and to distinguish the described objects; they have no order and do not represent a special limitation on the number of devices in the embodiments of this application, nor do they constitute any limitation on the embodiments of this application.

[0025] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A test fixture for testing image sensor chips, characterized in that, The test fixture includes: a light source, a light homogenizer, a lens assembly, and a light guide assembly located between the light source and the lens assembly. The light guide assembly has a through hole along the light path, and a transparent light guide is provided in the through hole, so that the test light first passes through the light guide and then through the light homogenizer into the lens according to a set unique light path.

2. The test fixture according to claim 1, characterized in that, The light guide assembly has a through hole to accommodate the light guide element.

3. The test fixture according to claim 1 or 2, characterized in that, The light guide is made of a transparent material, and the light transmittance and transmission / absorption characteristics of the material for different wavelengths can be selected according to application requirements.

4. The test fixture according to any one of claims 1 to 3, characterized in that, The shape of the light guide is not limited to a single shape; it can be cylindrical, square, or any shape designed according to the position of the light source and the requirements of the optical path.

5. The test fixture according to any one of claims 1 to 4, characterized in that, The light guide provides a single, essentially non-reflective transmission path in the optical path, thereby avoiding stray light caused by reflection or refraction when light passes through the light guide assembly or structure, and improving the imaging consistency at each test chip.

6. The test fixture according to any one of claims 1 to 5, characterized in that, By setting the light guide, the layout of the test chips is no longer limited by the field of view of the lens, thereby achieving a more flexible arrangement of test chip spacing and improving the testing efficiency of test points.

7. The test fixture according to claim 3, characterized in that, The material selected for the light guide has minimal impact on visible light transmission but exhibits absorption characteristics in the infrared band, which helps to suppress infrared-related stray light.

8. A method for assembling the test fixture according to any one of claims 1 to 7, characterized in that, The steps include: A through hole is formed at the light guide assembly; a transparent light guide with the required transmittance and wavelength response is selected or prepared; the light guide is embedded in the through hole; the relative positions of the light guide, the light homogenizer, and the lens are adjusted to ensure that the light path passes through the light guide and enters the lens in a unique manner.

9. A method for testing an image sensor chip using the test fixture according to any one of claims 1 to 7, characterized in that, include: The test light emitted by the light source is directionally transmitted through the light guide, then enters the lens through the light homogenizer to illuminate the chip under test. This optical path structure reduces stray light generated by reflection / refraction from the surface of the light guide or structural component, thereby improving the imaging consistency and test repeatability between different test chips.

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