Chip warpage deformation measurement method and device

Abstract

The present invention provides a chip warpage deformation measurement method and device, the method comprising: using a bundle adjustment method to calibrate the internal and external parameters of a binocular camera and simultaneously performing a secondary correction on the binocular camera to obtain a camera calibration result; using the calibrated binocular camera to collect a first image of a speckle pattern of a sample to be tested at a first temperature, and the sample to be tested prepares the speckle pattern in advance; the first image comprises a first left image and a first right image; heating or cooling the temperature of the sample to be tested to a second temperature and using the calibrated binocular camera to collect a second image of the speckle pattern of the sample to be tested at the second temperature; the second image comprises a second left image and a second right image; obtaining three-dimensional coordinates of pixel points of the first image and the second image; calculating the warpage, strain and thermal expansion coefficient of the sample to be tested according to the three-dimensional coordinates; and improving measurement efficiency and accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of chip warpage measurement, and in particular to a chip warpage measurement method and device. Background Art

[0002] All chips need to withstand high temperature loads when in use and low temperature loads when turned off. When the temperature changes, due to the different thermal expansion coefficients of different materials, the different deformation amounts of various materials of the chip will cause stress concentration, causing the package to warp or even crack. Therefore, warpage is one of the most important indicators for evaluating device reliability in electronic packaging.

[0003] At present, integrated circuit packaging is increasingly developing in the direction of thinning, miniaturization and complex structure. Chips with thinner BGA and other packaging forms have the problem of greater warping under temperature load than previous packaging forms. And with the development of POP (package-on-package), i.e. 3D packaging stacking technology of chips, it becomes more serious. There is an urgent need for an effective method and device to accurately evaluate the warpage deformation analysis of the entire temperature load process.

[0004] At present, the methods and technologies used in warpage deformation measurement at home and abroad mainly include the following: laser light sectioning method, moiré fringe shadow method, DIC digital image correlation method, etc.

[0005] The core9038a of CORES of Japan is a typical representative of laser light sectioning technology. The system has low measurement efficiency and needs to scan the measured object line by line to complete a full-field displacement measurement. It can only measure the surface flatness relative to the glass surface as the reference point. In addition, it is inconvenient to heat the lower part of the glass, which is not conducive to uniform and constant heating of the entire measured object.

[0006] The AXP2.0 system of Akrometrix in the United States is a typical representative of the Shadow Moire technology. The camera resolution of this system is limited, which must be 1.5 times or even higher than that of Gratingpitch. In addition, due to the presence of the grating on the upper part of the sample, the temperature control is mainly controlled by the bottom, and it is impossible to achieve uniform temperature control at the same time. As a result, there is a certain difference in thermal expansion between the front and back sides of the device due to heating. In addition, the sample needs to be moved during the entire measurement process, and its noise cannot be ignored for high-precision scenes. Finally, there are certain requirements for the sample, and the sample surface needs to be continuous. In order to eliminate the horizontal offset angle caused by the measurement position of the component, the least squares method is used to fit the rotation and unify it into one coordinate system.

[0007] The Q-400μDIC microscope system from Dantec of Denmark is a typical representative of DIC technology. The manual calibration of this system has certain operational requirements for repeatability. The constant temperature control system is conducted through the bottom single side, and the uniformity is limited. In addition, the maximum temperature is 130 degrees Celsius. No vibration isolation measures are taken and the light source uses a constant light, which inevitably requires a long exposure time, and its imaging effect cannot be ignored.

[0008] In addition, there is no clear solution for the impact of the temperature control units of each system on heat waves at high temperatures, possible condensation or even frost when heating or cooling.

[0009] The disclosure of the above background technology content is only used to assist in understanding the concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0010] In order to solve the existing problems, the present invention provides a chip warpage deformation measurement method and device.

[0011] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0012] A chip warpage deformation measurement method comprises the following steps: S1: using bundle adjustment method to calibrate internal and external parameters of a binocular camera and simultaneously performing secondary correction on the binocular camera to obtain a camera calibration result; S2: using the calibrated binocular camera to collect a first image of a speckle pattern of a sample to be tested at a first temperature, wherein the sample to be tested prepares the speckle pattern in advance; the first image comprises a first left image and a first right image; S3: heating or cooling the temperature of the sample to be tested to a second temperature and using the calibrated binocular camera to collect a second image of the speckle pattern of the sample to be tested at the second temperature; the second image comprises a second left image and a second right image; S4: obtaining three-dimensional coordinates of pixel points of the first image and the second image; S5: calculating the warpage, strain and thermal expansion coefficient of the sample to be tested according to the three-dimensional coordinates.

[0013] Preferably, the bundle adjustment method is used to calibrate the internal and external parameters of the binocular camera, and the binocular camera is secondary corrected to obtain the camera calibration result, which includes the following steps: S11: the automatic calibration device performs a rotational motion with two degrees of freedom to obtain a plurality of different postures of the calibration plate; S12: the binocular camera is used to obtain image points of object points on the calibration plate in different postures; S13: the binocular camera is calibrated through the image points and secondary corrected to obtain the camera calibration result.

[0014] Preferably, the process of projecting an object point P on the calibration plate to an image point p through the optical center S of the camera includes the following: the rotation matrix of the object point P in the world coordinate system to the camera coordinate system is R, and the translation matrix is ​​T. After considering the actual camera principal point deviation and lens distortion, the collinear equation of the actual camera imaging is obtained as follows:

[0015]

[0016]

[0017] in,

[0018] a2=cosωsinκ

[0019]

[0020]

[0021] b2=cosωcosκ

[0022]

[0023]

[0024] c2=-sinω

[0025]

[0026] ω is the rotation angle around the x-axis of the coordinate system, is the rotation angle around the y-axis of the coordinate system, κ is the rotation angle around the z-axis of the coordinate system, (x, y) is the pixel coordinate of the image point p, (c x ,c y ) is the principal point deviation, f is the focal length, (Δx, Δy) is the distortion deviation, (X C ,Y C ,Z C ) is the coordinate of point P in the camera coordinate system, (X W ,Y W ,Z W ) is the coordinate of point P in the world coordinate system, (X S ,Y S ,Z S ) is the coordinate of the camera optical center S in the world coordinate system; the bundle adjustment algorithm is used to solve the collinearity equation to obtain the internal and external parameters of the binocular camera.

[0027] Preferably, the principal point deviation with quadratic plane correction is considered in the direction of the lens optical center, the principal point deviation is calculated in the camera image plane, and the lens distortion with quadratic plane correction is calculated to perform a secondary correction on the binocular camera to obtain a new collinearity equation:

[0028]

[0029] Among them, σ x is the x-direction deviation, σ y is the y-direction deviation, σ x It includes the principal point deviation in the x direction in the image plane, the principal point offset in the x direction of the lens in the direction of the optical center, and the lens distortion; σ y It includes the principal point deviation in the y direction in the image plane, the principal point offset in the y direction of the lens in the direction of the optical center, and lens distortion.

[0030] Preferably, obtaining the three-dimensional coordinates of pixel points of the first image and / or the second image includes the following steps: S41: selecting the area of ​​interest of the sample to be tested from the first left image and / or the second left image as an image sub-area; S42: using the digital image correlation method to match the left and right images at the same temperature according to the image sub-area to determine the image sub-area corresponding to the first right image and / or the second right image; S43: obtaining the three-dimensional coordinates of pixel points of the image sub-area of ​​the first image and / or the second image.

[0031] Preferably, a digital image correlation method is used to calculate the similarity between the left and right images to obtain the image sub-area corresponding to the first right image or the second right image by matching, and the similarity is calculated by the following formula:

[0032]

[0033] Among them, f(x,y) is the grayscale value of the sub-region point (x,y) of the left image; g(x′,y′) is the grayscale value of the sub-region point (x′,y′) of the right image, and r0, r1 are the grayscale differences between the left and right images due to different brightness.

[0034] Preferably, the pixel points of the image sub-areas of the first image and the second image are corrected using the camera internal and external parameters and the image correlation matching result;

[0035] The three-dimensional coordinates of the pixel points of the image sub-area are calculated using the least squares solution:

[0036]

[0037]

[0038] Among them, (u1, v1) and (u2, v2) are the pixel coordinates of the left image point and the pixel coordinates of the right image point after correction, respectively, m is the camera parameter matrix, the superscript l of m represents the left camera, and the superscript r of m represents the right camera.

[0039] Preferably, when calculating the warpage of the sample to be tested based on the three-dimensional coordinates, a coordinate system conversion method of rigid body displacement is used to align the three-dimensional coordinates at the second temperature to the first temperature. The coordinate system conversion method of rigid body displacement includes: selecting all patch nodes of the image sub-area, and fitting a plane as a first reference plane using the least squares method; establishing a world coordinate system using the six-point rule, so that the first reference plane fitted by the least squares method is horizontal and the plane is moved to the lowest point to obtain a second reference plane, so that the second reference plane becomes a reference plane for displacement calculation; at this time, the expression of the warpage is converted into the distance from the point to the reference plane.

[0040] Preferably, the coordinate transformation of rigid body displacement adopts the following three methods: average method: use the average RT matrix of all points in the whole field of two images adjacent in time sequence for alignment; single point method: fix a single point on the reference image as the reference point, and then the same point in all images is translated and aligned to the reference point; three-point method: fix three points on the reference image as the reference points, and then the corresponding three points in all images are translated and rotated to align to the reference point.

[0041] The present invention also provides a device for measuring chip warpage deformation, comprising: a first unit: using a bundle adjustment method to calibrate the internal and external parameters of a binocular camera, and at the same time performing a secondary correction on the binocular camera to obtain a camera calibration result; a second unit: using the calibrated binocular camera to collect a first image of a speckle pattern of a sample to be tested at a first temperature, and the sample to be tested prepares the speckle pattern in advance; the first image includes a first left image and a first right image; a third unit: heating or cooling the temperature of the sample to be tested to a second temperature and using the calibrated binocular camera to collect a second image of the speckle pattern of the sample to be tested at the second temperature; the second image includes a second left image and a second right image; a fourth unit: obtaining the three-dimensional coordinates of pixel points of the first image and the second image; a fifth unit: calculating the warpage, strain and thermal expansion coefficient of the sample to be tested based on the three-dimensional coordinates.

[0042] The beneficial effects of the present invention are: providing a chip warpage deformation measurement method and device, improving calibration efficiency and stability by adopting automatic calibration; and using the bundle adjustment method to calibrate the binocular camera and perform secondary correction to improve the camera calibration accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of a chip warpage measurement method according to an embodiment of the present invention.

[0044] Figure 2 Schematic diagram of a method for obtaining a camera calibration result in an embodiment of the present invention.

[0045] Figure 3Schematic diagram of camera center projection in an embodiment of the present invention.

[0046] Figure 4 It is a schematic diagram of a method for obtaining three-dimensional coordinates of pixel points of a first image and / or a second image in an embodiment of the present invention.

[0047] Figure 5 Schematic diagram of warping of a sample to be tested in an embodiment of the present invention.

[0048] Figure 6(a)-Figure 6(c) It is a schematic diagram of the rigid displacement of the sample to be tested during the warping deformation in the embodiment of the present invention.

[0049] Figure 7 Schematic diagram of coordinate transformation of rigid body displacement using the three-point method in an embodiment of the present invention.

[0050] Figure 8 Schematic diagram of a chip warpage measurement system according to an embodiment of the present invention.

[0051] Fig. 9 Schematic diagram of the structure of the automatic calibration unit in the embodiment of the present invention.

[0052] Fig.10 Schematic diagram of the structure of the automatic calibration unit in the embodiment of the present invention.

[0053] Fig.11 It is a schematic diagram of a spot-making effect in an embodiment of the present invention.

[0054] Fig.12 Schematic diagram of a circulating air heating and cooling unit in an embodiment of the present invention.

[0055] Fig.13 Schematic diagram of a dehumidification unit in an embodiment of the present invention.

[0056] Fig.14 Schematic diagram of a heat wave elimination unit in an embodiment of the present invention.

[0057] Fig.15 It is a schematic diagram of the process of automatically collecting data in an embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to make the technical problems, technical solutions and beneficial effects to be solved by the embodiments of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0059] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and circuit connection.

[0060] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0061] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0062] The laser light section method uses a high-precision laser displacement sensor to measure the Z-direction distance, and cooperates with the XY-direction motion mechanism to achieve full-field multi-point 3D displacement measurement.

[0063] The shadow moiré method uses geometric interference between a reference grating and its shadow on the sample to measure the relative vertical displacement of each pixel position in the image. It requires a regular grating, a white light source at approximately 45° to the grating, and a camera perpendicular to the grating. Vertical translation of the sample improves measurement resolution and provides automatic sorting of interference fringes.

[0064] Digital image correlation is to apply a high-contrast random speckle pattern to the surface of interest, use two cameras to form a binocular system, and use the spot feature recognition in a small pixel patch for the same point of the measured object. Apply the principle of stereo triangulation to determine the spatial position of the pixel patch relative to the camera in 3D space. By stepping the pixel patch calculation on the sample, the three-dimensional full-field displacement can be obtained and other values ​​can be calculated.

[0065] like Figure 1 As shown, the present invention provides a chip warpage deformation measurement method, comprising the following steps:

[0066] S1: using the bundle adjustment method to calibrate the internal and external parameters of the binocular camera and at the same time perform a secondary calibration on the binocular camera to obtain a camera calibration result;

[0067] S2: using the calibrated binocular camera to collect a first image of a speckle pattern of a sample to be tested at a first temperature, wherein the speckle pattern of the sample to be tested is prepared in advance; the first image includes a first left image and a first right image;

[0068] S3: heating or cooling the temperature of the sample to be tested to a second temperature and using the calibrated binocular camera to collect a second image of the speckle pattern of the sample to be tested at the second temperature; the second image includes a second left image and a second right image;

[0069] S4: Acquire three-dimensional coordinates of pixel points of the first image and the second image;

[0070] S5: Calculating the warpage, strain and thermal expansion coefficient of the sample to be tested according to the three-dimensional coordinates.

[0071] The present invention improves calibration efficiency and stability by adopting automatic calibration; and uses the bundle adjustment method to calibrate the binocular camera and simultaneously performs secondary correction to improve the camera calibration accuracy.

[0072] In an embodiment of the present invention, other temperature points may be set, and the image may be acquired at the set temperature points as described above.

[0073] like Figure 2 As shown, in another embodiment of the present invention, the internal and external parameters of the binocular camera are calibrated by the bundle adjustment method, and the binocular camera is calibrated twice to obtain a camera calibration result, which includes the following steps:

[0074] S11: The automatic calibration device performs a rotational motion with two degrees of freedom to obtain multiple different postures of the calibration plate;

[0075] S12: using the binocular camera to obtain image points of object points on the calibration plate in different postures;

[0076] S13: Calibrate the binocular camera using the image points and perform secondary correction to obtain the camera calibration result.

[0077] In one embodiment of the present invention, 18-24 different postures can be obtained.

[0078] The present invention adopts an automatic calibration device which is convenient and reliable and avoids the inconsistency of multiple manual operations.

[0079] Assume that the process of projecting an object point P on the calibration plate through the camera optical center S to the image point p includes the following:

[0080] The rotation matrix from the object point P in the world coordinate system to the camera coordinate system is R, and the translation matrix is ​​T.

[0081] like Figure 3 , which is a schematic diagram of camera center projection in an embodiment of the present invention.

[0082] After considering the actual camera principal point deviation and lens distortion, the collinear equation of the actual camera imaging is obtained as follows:

[0083]

[0084] a1=cosφcosκ+sinφsinωsinκ,

[0085] Where a1=cosφcosκ+sinφsinωsinκ

[0086] a2=cosωsinκ

[0087] a3=-sinφcosκ+cosφsinωsinκ

[0088] b1=-cosφsinκ+sinφsinωcosκ

[0089] b2=cosωcosκ

[0090]

[0091]

[0092] c2=-sinω

[0093]

[0094] ω is the rotation angle around the x-axis of the coordinate system, is the rotation angle around the y-axis of the coordinate system, κ is the rotation angle around the z-axis of the coordinate system, (x, y) is the pixel coordinate of the image point p, (c x ,c y ) is the principal point deviation, f is the focal length, (Δx, Δy) is the distortion deviation, (X C ,Y C ,Z C ) is the coordinate of point P in the camera coordinate system, (X W ,Y W ,Z W ) is the coordinate of point P in the world coordinate system, (X S ,Y S ,Z S ) is the coordinate of the camera optical center S in the world coordinate system;

[0095] The bundle adjustment algorithm is used to solve the collinearity equation to obtain the internal and external parameters of the binocular camera.

[0096] Considering the principal point deviation with quadratic plane correction in the direction of the lens optical center, the principal point deviation is calculated in the camera image plane, and the lens distortion with quadratic plane correction is calculated to perform a secondary correction on the binocular camera to obtain a new collinearity equation:

[0097]

[0098] Among them, σ x is the x-direction deviation, σ y is the y-direction deviation, σ x It includes the principal point deviation in the x direction in the image plane, the principal point offset in the x direction of the lens in the direction of the optical center, and the lens distortion; σ y It includes the principal point deviation in the y direction in the image plane, the principal point offset in the y direction of the lens in the direction of the optical center, and lens distortion.

[0099] It can be understood that in the present invention, the speckle pattern is prepared in advance for the sample to be tested, and the specific preparation method will be discussed in detail later.

[0100] The speckle pattern of the sample to be tested is collected by a calibrated binocular camera, and then the speckle evaluation algorithm is used to evaluate the measurability from three dimensions: contrast, grayscale gradient, and average pixel occupancy, thus improving the success rate of a single measurement.

[0101] The binocular camera can obtain two images, left and right, in one acquisition.

[0102] like Figure 4 As shown, obtaining the three-dimensional coordinates of the pixel points of the first image and / or the second image includes the following steps:

[0103] S41: selecting a region of interest of the sample to be tested from the first left image and / or the second left image as an image sub-region;

[0104] S42: Matching the left and right images at the same temperature using a digital image correlation method according to the image sub-regions to determine the image sub-regions corresponding to the first right image and / or the second right image;

[0105] S43: Acquire three-dimensional coordinates of pixel points of the image sub-area of ​​the first image and / or the second image.

[0106] Specifically, the digital image correlation method is used to calculate the similarity between the left and right images to obtain the image sub-area corresponding to the first right image or the second right image by matching, and the similarity is calculated by the following formula:

[0107]

[0108] Among them, f(x,y) is the grayscale value of the sub-region point (x,y) of the left image; g(x′,y′) is the grayscale value of the sub-region point (x′,y′) of the right image, and r0, r1 are the grayscale differences between the left and right images due to different brightness.

[0109] Then, the left pixel coordinates of the tracking point (u c1 ,v c1 ), right pixel coordinate (u c2 ,v c2 ), and then use stereo vision technology to perform 3D reconstruction, and finally use the results of 3D reconstruction to calculate warpage, strain and thermal expansion coefficient CTE.

[0110] Specifically, the pixel points of the image sub-areas of the first image and the second image are corrected using the camera internal and external parameters and the image correlation matching result; c1 ,v c1 ) as an example:

[0111]

[0112] The three-dimensional coordinates of the pixel points of the image sub-area are calculated using the least squares solution:

[0113]

[0114]

[0115] Among them, (u1, v1) and (u2, v2) are the pixel coordinates of the left image point and the pixel coordinates of the right image point after correction, respectively, m is the camera parameter matrix, the superscript l of m represents the left camera, and the superscript r of m represents the right camera.

[0116] Calculate the warpage:

[0117] The reference surface is fitted using multiple points on the two diagonals at the initial temperature of the sample under test, i.e. the first temperature T1, and a world coordinate system is established with the reference surface as the horizontal plane using a coordinate transformation algorithm. Then, the three-dimensional coordinates of multiple points on the two diagonals at the second temperature T2 are calculated, and the three-dimensional points at the second temperature T2 are aligned to the first temperature T1 using the rigid body displacement method. Finally, the distances from these points to the reference plane are calculated, and the position curves of each temperature zone point and the 3D displacement cloud map are plotted to describe the sample warping.

[0118] like Figure 5 FIG. 1 is a schematic diagram of warping of a sample to be tested in an embodiment of the present invention.

[0119] The strain is calculated by the following formula:

[0120]

[0121] Where L is the length before deformation and ΔL is the elongation after deformation.

[0122] The coefficient of thermal expansion is calculated by the following formula:

[0123]

[0124] Wherein, ΔT is the variation of the measured sample at two temperature points T and T′, and ε is the strain of the measured sample caused by ΔT.

[0125] like Figure 6(a)-Figure 6(c) As shown, it is a schematic diagram of the rigid displacement produced by the sample to be tested during warping deformation.

[0126] In a specific embodiment, when calculating the warpage of the sample to be tested according to the three-dimensional coordinates, a coordinate system conversion method of rigid body displacement is used to align the three-dimensional coordinates at the second temperature to the first temperature, and the coordinate system conversion method of rigid body displacement includes:

[0127] Select all patch nodes of the image sub-area, and use the least square method to fit a plane as a first reference plane;

[0128] A world coordinate system is established by using the six-point rule, so that the first reference plane fitted by the least square method is horizontal and the plane is moved to the lowest point to obtain a second reference plane, so that the second reference plane becomes a reference plane for displacement calculation;

[0129] At this time, the expression of warpage is transformed into the distance from the point to the reference plane.

[0130] The coordinate transformation of rigid body displacement adopts the following three methods:

[0131] Average method: use the average RT matrix of all points in two temporally adjacent images for registration;

[0132] Single point method: a single point is fixed on the reference image as the reference point, and then the same point in all images is translated and aligned to the reference point;

[0133] Three-point method: Three points are fixed on the reference image as reference points, and then the three points corresponding to all images are translated and rotated to align with the reference points.

[0134] like Figure 7 The figure shows the schematic diagram of coordinate transformation of rigid body displacement using the three-point method.

[0135] The present invention adopts rigid body displacement and coordinate system conversion algorithm, so that the sample can be accurately and flexibly unified after inevitable thermal expansion or rigid body displacement;

[0136] The present invention also provides a device for measuring chip warpage deformation, comprising:

[0137] Unit 1: Use bundle adjustment method to calibrate the internal and external parameters of the binocular camera, and perform secondary calibration on the binocular camera to obtain the camera calibration result;

[0138] Unit 2: using the calibrated binocular camera to collect a first image of a speckle pattern of a sample to be tested at a first temperature, wherein the speckle pattern is prepared in advance on the sample to be tested; the first image includes a first left image and a first right image;

[0139] The third unit: heats or cools the temperature of the sample to be tested to a second temperature and uses the calibrated binocular camera to collect a second image of the speckle pattern of the sample to be tested at the second temperature; the second image includes a second left image and a second right image;

[0140] Unit 4: acquiring three-dimensional coordinates of pixel points of the first image and the second image;

[0141] Unit 5: Calculating the warpage, strain and thermal expansion coefficient of the sample to be tested according to the three-dimensional coordinates.

[0142] like Figure 8 As shown, the hardware system of the present invention mainly includes a binocular camera 1, a light source 2, a temperature control unit 8, an automatic calibration unit 5, a dehumidification unit 7, a heat wave elimination unit 3, and a control unit 9 which are connected in sequence.

[0143] The automatic calibration unit 5 is arranged in the temperature chamber 4, and the entire temperature chamber 4 is arranged on the vibration isolation platform 6. The introduction of the vibration isolation platform can reduce the imaging smear caused by various vibrations.

[0144] like Fig. 9 Shown is a schematic diagram of the automatic calibration unit of the present invention.

[0145] In one embodiment, the automatic calibration unit is composed of a dual-axis rotation mechanism and a backlight source. The dual-axis rotation mechanism can realize the placement of the calibration plate in different postures, and the backlight source reduces the interference of the background on the calibration plate image, increases the contrast of the calibration plate image, and improves the image detection quality. First, the automatic calibration unit is powered and the backlight source is turned on; then, the control unit 9 is used to control the automatic calibration unit to move to multiple different postures, and the binocular camera 1 is controlled to trigger synchronous image acquisition; finally, the internal and external parameters of the binocular camera are calibrated by the bundle adjustment method of the secondary correction model to realize the automated camera calibration process. The automated calibration device is convenient and reliable, and avoids the inconsistency of multiple manual operations.

[0146] The calibration plate adopts photolithography technology and uses sodium calcium glass or quartz glass with low thermal expansion coefficient.

[0147] The present invention adopts a high-power synchronous light source, reduces the system exposure time by multiples, reduces smearing, and introduces a vibration isolation platform to reduce the impact of vibration.

[0148] The device of the present invention adopts the following two methods to prepare the speckle pattern:

[0149] (1) In micro-field applications, graphite powder or carbon powder with different particle sizes of 0.5um-10um is designed, combined with high-temperature resistant primer. Dust is formed by blowing gas into the carbon powder chamber and then sprayed out through the outlet.

[0150] like Fig.10 As shown, it is a kind of spot making effect of the present invention. Good randomness can be formed at a suitable distance.

[0151] (2) In other scene applications, the speckle projection device is used for preparation.

[0152] like Fig.11 As shown, the speckle projection device is composed of a light source 10, a mask sheet 11 and a lens 12 connected in sequence. The surface features of the sample are generated. First, a random vector template generation tool is used to generate speckles. Then, the designed random speckle pattern is made on sodium calcium glass or quartz glass as a mask sheet. The speckle projector is controlled by a system controller. A completed sequence is: speckle projection first, then camera acquisition, and then turning off speckle projection.

[0153] The present invention adopts an evaluable spot making technology to improve the measurability of the measurement sample and the one-time measurement success rate.

[0154] like Fig.12 As shown, in the present invention, a circulating air heating and cooling unit is used, and the test sample 13 on the support unit 14 is heated evenly at multiple angles, thereby solving the problem of insufficient uniformity of temperature control by conduction or unilateral radiation or the low efficiency caused by the need for long-term heat preservation, and cooperating with multi-point temperature measurement to provide fast, uniform and precise temperature control technology.

[0155] In the existing visual technology with a temperature chamber module and a camera lens, there is a common problem of water mist or even frost formed by condensation of water vapor due to alternating high and low temperatures, temperature deformation of the observation window and poor thermal insulation, and the influence of thermal air flow disturbance generated on the upper surface of the observation window on image acquisition at high temperatures.

[0156] like Fig.13As shown, the present invention is provided with a dehumidification module, and after the sample to be tested is placed in the temperature bin 4, the overall temperature circulation system forms a closed space. A dehumidification unit 7 is arranged between the temperature control unit 8 and the temperature bin 4, and then three sealing valves S1, S2, and S3 are arranged. First, the S1 sealing valve is closed, and the S2 and S3 sealing valves are opened. The dehumidification unit 7 starts to circulate the air from S3 through the pipeline, the temperature bin 4, the temperature control unit 8, and returns to the dehumidification unit 7 through S2. The dehumidification method can be chemical dehumidification of calcium oxide, physical dehumidification adsorption dehumidification, and periodic replacement of the dehumidifier. After the whole process is completed, close the S2 and S3 sealing valves, open the S1 sealing valve to enter the normal working mode. The temperature bin 4, the dehumidification unit 7 and the temperature control unit 8 are connected by pipelines to form a closed space.

[0157] The present invention also provides an observation window, and the observation window of the temperature chamber 4 is made of double-layer quartz optical glass with a vacuum treatment in the middle layer. Quartz optical glass with a low thermal expansion coefficient can be used as the observation window material, and the vacuum treatment in the middle layer reduces the condensation or frost of the outer glass at low temperatures below 0°C, which affects visual observation; it also reduces the temperature diffusion from the outer glass to the lens to form hot air flow disturbance under high temperature conditions, which also affects the imaging quality.

[0158] like Fig.14 As shown, the present invention is based on the thermal airflow and ambient airflow disturbance, and a uniform-speed fan and a fixed air outlet are arranged between the observation window and the lens to form a uniform and stable airflow field.

[0159] The present invention improves data stability and system measurement accuracy by setting multiple dimensions as above.

[0160] like Fig.15 The figure shows a specific flow chart.

[0161] The present invention requires presetting multiple temperature points that need to be tested and setting the starting temperature; starting the temperature control device for heating or cooling; acquiring the temperatures of multiple points and samples in real time, and judging whether the heating rate and temperature have reached the current set value of the sequence; if not, continuing the temperature change process, and stopping the temperature control device after reaching the set value; delaying for a few seconds to wait for the circulating airflow to stop; the acquisition system performs image acquisition according to the acquisition quantity and acquisition interval set by the customer, and correspondingly saves the samples and 5 temperature values ​​at this moment; then starting the temperature control device, changing the temperature to the next sequence temperature setting point, and completing all the sequence temperature points set by the program in this cycle; the automated acquisition is completed, and then the analysis mode can be entered for data processing.

[0162] The present invention uses a high-power synchronous light source to reduce the system exposure time exponentially. At the same time, a hose is used to connect the temperature control unit and the temperature chamber, and a vibration isolation platform is introduced to reduce imaging smear caused by various vibrations. A high-power synchronous flash light source is used to instantly provide up to 2-3 times the overload brightness. The exposure time is reduced to 1 / 2 to 1 / 3 of the original time. In different application scenarios, a light source with a specific wavelength can be selected to achieve the best effect. Such as blue light with a wavelength of 450nm in visible light, infrared band of 730nm in invisible light, laser, etc.

[0163] At the same time, a dual-frequency damping optical vibration isolation platform or a better active anti-vibration is used to reduce the vibration caused by the ground and other peripheral equipment, effectively improving the image smear caused by the exposure time due to vibration.

[0164] An embodiment of the present application also provides a control device, including a processor and a storage medium for storing a computer program; wherein the processor is used to execute at least the method described above when executing the computer program.

[0165] An embodiment of the present application also provides a storage medium for storing a computer program, which at least performs the method described above when executed.

[0166] An embodiment of the present application further provides a processor, which executes a computer program and at least performs the method described above.

[0167] The storage medium may be implemented by any type of volatile or non-volatile storage device, or a combination thereof. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a magnetic random access memory (FRAM), a flash memory, a magnetic surface memory, an optical disc, or a compact disc read-only memory (CD-ROM); the magnetic surface memory may be a disk memory or a tape memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM), synchronous static random access memory (SSRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAMEnhanced Synchronous Dynamic Random Access Memory), synchronous link dynamic random access memory (SLDRAM), direct memory bus random access memory (DRRAM). The storage media described in the embodiments of the present invention are intended to include, but are not limited to, these and any other suitable types of memory.

[0168] In the several embodiments provided in the present application, it should be understood that the disclosed systems and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored, or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0169] The units described above as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units; some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0170] In addition, all functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may be separately used as a unit, or two or more units may be integrated into one unit; the above-mentioned integrated units may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0171] A person skilled in the art can understand that: all or part of the steps of implementing the above method embodiment can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiment; and the aforementioned storage medium includes: mobile storage devices, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), disks or optical disks, etc. Various media that can store program codes.

[0172] Alternatively, if the above-mentioned integrated unit of the present invention is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present invention can be essentially or partly reflected in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROM, RAM, magnetic disks or optical disks.

[0173] The methods disclosed in several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0174] The features disclosed in several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments.

[0175] The features disclosed in several method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0176] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, several equivalent substitutions or obvious variations can be made without departing from the concept of the present invention, and the performance or use is the same, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A chip warpage measurement method, characterized in that: The steps include: S1: using the bundle adjustment method to calibrate the internal and external parameters of the binocular camera and at the same time perform a secondary calibration on the binocular camera to obtain a camera calibration result; S2: using the calibrated binocular camera to collect a first image of a speckle pattern of a sample to be tested at a first temperature, wherein the speckle pattern is prepared in advance on the sample to be tested; the first image includes a first left image and a first right image; S3: heating or cooling the temperature of the sample to be tested to a second temperature and using the calibrated binocular camera to collect a second image of the speckle pattern of the sample to be tested at the second temperature; the second image includes a second left image and a second right image; S4: Acquire three-dimensional coordinates of pixel points of the first image and the second image; S5: Calculating the warpage, strain and thermal expansion coefficient of the sample to be tested according to the three-dimensional coordinates; The steps of calibrating the internal and external parameters of the binocular camera by using the bundle adjustment method and performing secondary correction on the binocular camera to obtain the camera calibration result include the following steps: S11: The automatic calibration device performs a rotational motion with two degrees of freedom to obtain multiple different postures of the calibration plate; S12: using the binocular camera to obtain image points of object points on the calibration plate in different postures; S13: Calibrate the binocular camera using the image points and perform secondary correction to obtain the camera calibration result.

2. The chip warpage measurement method according to claim 1, characterized in that: The process of projecting an object point P on the calibration plate to an image point p through the optical center S of the camera includes the following steps: The rotation matrix from the object point P in the world coordinate system to the camera coordinate system is R, and the translation matrix is ​​T. After considering the actual camera principal point deviation and lens distortion, the collinear equation of the actual camera imaging is obtained as follows: in, a2=cosωsinκ b2=cosωcosκ c2=-sinω ω is the rotation angle around the x-axis of the coordinate system, is the rotation angle around the y-axis of the coordinate system, κ is the rotation angle around the z-axis of the coordinate system, (x, y) is the pixel coordinate of the image point p, (c x ,c y ) is the principal point deviation, f is the focal length, (Δx, Δy) is the distortion deviation, (X C ,Y C ,Z C ) is the coordinate of point P in the camera coordinate system, (X W ,Y W ,Z W ) is the coordinate of point P in the world coordinate system, (X S ,Y S ,Z S ) is the coordinate of the camera optical center S in the world coordinate system; The bundle adjustment algorithm is used to solve the collinearity equation to obtain the internal and external parameters of the binocular camera.

3. The chip warpage measurement method according to claim 2, characterized in that: Considering the principal point deviation with quadratic plane correction in the direction of the lens optical center, the principal point deviation is calculated in the camera image plane, and the lens distortion with quadratic plane correction is calculated to perform a secondary correction on the binocular camera to obtain a new collinearity equation: Among them, σ x is the x-direction deviation, σ y is the y-direction deviation, σ x It includes the principal point deviation in the x direction in the image plane, the principal point offset in the x direction of the lens in the direction of the optical center, and the lens distortion; σ y It includes the principal point deviation in the y direction in the image plane, the principal point offset in the y direction of the lens in the direction of the optical center, and lens distortion.

4. The chip warpage measurement method according to claim 3, characterized in that: Acquiring the three-dimensional coordinates of the pixel points of the first image and / or the second image comprises the following steps: S41: selecting a region of interest of the sample to be tested from the first left image and / or the second left image as an image sub-region; S42: Matching the left and right images at the same temperature using a digital image correlation method according to the image sub-regions to determine the image sub-regions corresponding to the first right image and / or the second right image; S43: Acquire three-dimensional coordinates of pixel points of the image sub-area of ​​the first image and / or the second image.

5. The chip warpage measurement method according to claim 4, characterized in that: The digital image correlation method is used to calculate the similarity between the left and right images to obtain the image sub-area corresponding to the first right image or the second right image by matching them. The similarity is calculated by the following formula: Among them, f(x,y) is the grayscale value of the sub-region point (x,y) of the left image; g(x′,y′) is the grayscale value of the sub-region point (x′,y′) of the right image, and r0, r1 are the grayscale differences between the left and right images due to different brightness.

6. The chip warpage measurement method according to claim 5, characterized in that: Correcting the pixel points of the image sub-areas of the first image and the second image by using the camera internal and external parameters and the image correlation matching result; The three-dimensional coordinates of the pixel points of the image sub-area are calculated using the least squares solution: Among them, (u1, v1) and (u2, v2) are the pixel coordinates of the left image point and the pixel coordinates of the right image point after correction, respectively, m is the camera parameter matrix, the superscript l of m represents the left camera, and the superscript r of m represents the right camera.

7. The chip warpage measurement method according to claim 6, characterized in that: When calculating the warpage of the sample to be tested according to the three-dimensional coordinates, a coordinate system transformation of rigid body displacement is used to align the three-dimensional coordinates at the second temperature to the first temperature. The coordinate system transformation of rigid body displacement includes: Select all patch nodes of the image sub-area, and use the least square method to fit a plane as a first reference plane; A world coordinate system is established by using the six-point rule, so that the first reference plane fitted by the least square method is horizontal and the plane is moved to the lowest point to obtain a second reference plane, so that the second reference plane becomes a reference plane for displacement calculation; At this time, the expression of warpage is transformed into the distance from the point to the reference plane.

8. The chip warpage measurement method according to claim 7, characterized in that: The coordinate transformation of rigid body displacement adopts the following three methods: Average method: use the average RT matrix of all points in two temporally adjacent images for registration; Single point method: a single point is fixed on the reference image as the reference point, and then the same point in all images is translated and aligned to the reference point; Three-point method: Three points are fixed on the reference image as reference points, and then the three points corresponding to all images are translated and rotated to align with the reference points.

9. A device for measuring chip warpage, characterized in that: include: Unit 1: Use bundle adjustment method to calibrate the internal and external parameters of the binocular camera, and perform secondary calibration on the binocular camera to obtain the camera calibration result; Unit 2: using the calibrated binocular camera to collect a first image of a speckle pattern of a sample to be tested at a first temperature, wherein the speckle pattern is prepared in advance on the sample to be tested; the first image includes a first left image and a first right image; The third unit: heats or cools the temperature of the sample to be tested to a second temperature and uses the calibrated binocular camera to collect a second image of the speckle pattern of the sample to be tested at the second temperature; the second image includes a second left image and a second right image; Unit 4: acquiring three-dimensional coordinates of pixel points of the first image and the second image; Unit 5: Calculating the warpage, strain and thermal expansion coefficient of the sample to be tested according to the three-dimensional coordinates; The camera calibration result obtained by calibrating the internal and external parameters of the binocular camera by using the bundle adjustment method and performing secondary correction on the binocular camera includes: The automatic calibration device performs a rotational motion with two degrees of freedom to obtain multiple different postures of the calibration plate; Using the binocular camera to obtain image points of object points on the calibration plate in different postures; The binocular camera is calibrated through the image points and corrected twice to obtain the camera calibration result.

Images