IC packaging body crack detection method based on tomography test

Abstract

The invention provides an IC packaging body crack detection method based on a tomography test, and the method comprises the steps: carrying out the transmission scanning of an IC packaging body through an ultrasonic scanning microscopic test, obtaining a crack initial distribution region, and determining a crack development range on the basis; respectively performing ultrasonic scanning microscopic test scanning in the X, Y and Z directions to obtain crack distribution information in the corresponding directions, and recording the section corresponding to the maximum crack area as a main plane O; cT scanning is conducted inside and outside the crack development range on the two sides of O, then interfaces of different parts are covered, the crack area and the packaging body area of each image are distinguished, the crack areas in the adjacent scanned images in the data set are compared, if the space change degrees of all the cracks are within a set value, detection is completed, and if some space change degrees are larger than the set value, detection is completed. CT scanning is supplemented between the corresponding adjacent scanning images until the spatial variation degrees of all the cracks are within a set value, the data can be accurately reconstructed into a three-dimensional model of the target packaging body containing the cracks, and a basis is provided for subsequent simulation experiments and failure analysis work.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor packaging, and in particular to a method for detecting cracks in an IC packaging body based on tomography testing. Background Art

[0002] IC packaging refers to the process of connecting one or more chips and devices to circuits through a series of technologies, and then combining them with various types of carriers with specific input and output ports in a suitable form, and using materials with certain functions to add shells, and finally forming electronic devices or circuit systems with specific functions. The main functions of the package formed by IC packaging are fixation, protection, structural support, and electrical connection, which requires the package to have strong stability. Various factors such as material selection, structural design, and process parameters have complex effects on the reliability of the package. During the production process, the package will experience various stress and temperature environments, and microcracks may occur inside, or even internal interface delamination, which will lead to serious packaging structure failure problems such as package cracking, chip breakage, and even package breakage, which will have a serious impact on its working performance. Identifying cracks in various components of the package and conducting quantitative and qualitative analysis of them in combination with various environmental factors is one of the important basic work to explore various fracture failure mechanisms of the package.

[0003] At present, there are many non-destructive tomography imaging test methods applied to the detection of cracks and delamination in IC packages. The basic theory of ultrasonic scanning microscopy (SAT) was first proposed by scholars in the 1930s, and the first acoustic scanning equipment was successfully developed by the CFQuate team in 1973. SAT is to send high-frequency ultrasonic waves to the sample to be tested through a transmitting device, and penetrate into the interior of the sample from the surface. Due to the difference in material acoustic impedance at the interface between different media, high-frequency ultrasonic waves will absorb and reflect the sound waves to varying degrees. Therefore, the energy information or sound wave phase information of the reflected or penetrated high-frequency ultrasonic waves can be collected to determine the internal structural information of the sample. Ultrasonic scanning microscopy has significant advantages such as diverse scanning forms and no damage to the sample.

[0004] The theory of computer tomography (CT) was proposed by physicist Cormack in 1963. In 1967, the first simple scanning device of X-ray radiation source was developed by electronic engineer Hounsfield. In 1972, the first CT equipment was successfully developed. At present, the increasingly mature CT technology has been widely used in medical examination, industrial inspection and other fields. Industrial CT has a strong tomographic imaging function, which can obtain detailed cross-sectional images of the sample to be tested and has a very high material density resolution ability. The output of industrial CT imaging is a digital image result, which can directly read the physical information of the object to be tested, such as pixel value, size, density, etc., which is very convenient for storage, transmission and analysis.

[0005] The morphology of cracks in the package formed by IC packaging is relatively complex. Single-method tomography tests such as SAT and CT cannot accurately characterize the crack morphology characteristics and the spatial distribution of cracks within the entire package, and cannot fully describe the cracks in the package. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides an IC package crack detection method based on tomography testing, which can accurately and efficiently identify cracks in the package, and facilitate the accurate reconstruction of the obtained cross-sectional imaging data into a three-dimensional model of the target package containing cracks, thereby providing a basis for subsequent simulation experiments and failure analysis work.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for detecting cracks in an IC package based on tomography testing comprises the following steps:

[0009] S1, firstly, using the T-Scan mode of ultrasonic scanning microscopy to perform transmission scanning on the IC package to be tested, to obtain the area Q where cracks of the IC package are initially distributed, and then determining the precise crack development range of the IC package based on the area Q;

[0010] S2, performing ultrasonic scanning microscopic test scans at equal intervals in the X direction, Y direction and Z direction of the crack development range to obtain crack distribution information in the X direction, Y direction and Z direction, and recording the section corresponding to the maximum crack area in all section scanning results as the main plane O of the IC package crack;

[0011] S3, performing CT scanning inside and outside the crack development range at a fixed interval on both sides of the main plane O, and then performing CT scanning on different parts of the interface of the IC package that are not covered by the separate CT scanning, and finally distinguishing the crack area and the package area of ​​each scanned image to obtain a CT scanning data set;

[0012] S4, comparing the crack areas in adjacent scanned images in the CT scan data set to obtain a series of crack space variation data. If all the crack space variation degrees are within the set value, the detection of IC package cracks is completed. If there is a crack space variation degree greater than the set value, a supplementary CT scan is performed between the corresponding adjacent scanned images until all the crack space variation degrees are within the set value, thereby obtaining a new CT scan data set and completing the detection of IC package cracks.

[0013] Preferably, S1 performs ultrasonic scanning microscopic testing along the X direction, Y direction and Z direction of the region Q to determine the precise crack development range of the IC package, and the determination of the X direction, Y direction and Z direction is as follows:

[0014] The IC package is a rectangular parallelepiped, the Z direction is the thickness direction of the IC package, if the length and width of the IC package are not equal, the X direction is the length direction of the IC package, and the Y direction is the width direction of the IC package; if the length and width of the IC package are equal, the X direction is the direction of the long opposite side of the main chip surface in the package, and the Y direction is the direction of the short opposite side of the main chip surface in the package.

[0015] Furthermore, S1 performs B-Scan profile scans with equal intervals in the X direction with the X axis as the normal. The starting and ending positions of the scan are located on both sides of the X direction of region Q to determine the extension boundary range of the crack in the X direction. Then, the scan interval is shortened to perform profile scanning to obtain the development range of the crack in the X direction.

[0016] Perform B-Scan profile scans with equal intervals in the Y direction with the Y axis as the normal. The starting and ending positions of the scan are located on both sides of the Y direction of region Q to determine the extension boundary range of the crack in the Y direction. Then, shorten the scanning interval to perform profile scanning to obtain the development range of the crack in the Y direction.

[0017] A C-Scan profile scan with equal intervals and the Z axis as the normal is performed in the Z direction. The starting and ending positions of the scan are located on both sides of the Z direction of area Q to determine the extension boundary range of the crack in the Z direction. Then, the scanning interval is shortened to perform a profile scan to obtain the development range of the crack in the Z direction.

[0018] Furthermore, when S1 obtains the development range of the crack in the X-axis direction, the shortened scanning interval is the time interval for determining the extension boundary range of the crack in the X-axis direction.

[0019] When S1 obtains the development range of the crack in the Y-axis direction, the shortened scanning interval is the time interval for determining the extension boundary range of the crack in the Y-axis direction.

[0020] When S1 obtains the development range of the crack in the Z-axis direction, the shortened scanning interval is the time interval for determining the extension boundary range of the crack in the Z-axis direction.

[0021] Further, in S2, in the X direction, starting from a boundary of the crack development range of the IC package body, a B-Scan mode scan is performed in the crack development range along the X direction with equal intervals to obtain crack distribution information in the X direction;

[0022] In the Y direction, starting from one boundary of the crack development range of the IC package, a B-Scan mode scan is performed in the crack development range along the Y direction with equal intervals to obtain the crack distribution information in the Y direction;

[0023] In the Z direction, starting from a boundary of the crack development range of the IC package, a C-Scan mode scan is performed in the crack development range along the Z direction with equal intervals to obtain the crack distribution information in the Z direction.

[0024] Preferably, in S3, the CT scanning interval outside the crack development range is greater than the CT scanning interval within the crack development range.

[0025] Preferably, if there is a scan image in S3 in which the crack area occupies more than 10% of the corresponding cross-sectional area of ​​the IC package, a supplementary scan is performed at the midpoint position of adjacent scan images on both sides of the corresponding scan image to obtain an optimized CT section scan data set, and then the optimized CT section scan data set is processed in the same manner as the CT scan data set in S4 to complete the detection of cracks in the IC package.

[0026] Preferably, in S4, a supplementary CT scan is performed at the midpoint position of the corresponding adjacent scan images.

[0027] Preferably, S4 obtains the corresponding crack space variation degree from two adjacent scan images according to the following process, and then obtains a series of crack space variation degree data from adjacent scan images in the CT scan data set:

[0028] Assuming that the maximum aperture of the smallest crack in two adjacent scanned images is d, the ε value of the adjacent images is determined by the following formula, where ε is the side length of the square block used to measure fractals in fractal geometry, and n is the target accuracy:

[0029] ε=d / n;

[0030] The complexity of the crack boundaries of the two adjacent scanned images is determined by the following formula:

[0031] D i =log (1 / ε) N i (ε);

[0032] N i (ε) is the number of square blocks with a side length equal to ε required to completely cover the crack area in the corresponding scanned image, i = 1 or 2, 1 corresponds to one of the scanned images, and 2 corresponds to the other scanned image;

[0033] The crack spatial variation C is determined by the following formula:

[0034] C = |D1-D2|.

[0035] Compared with the prior art, the present invention has the following beneficial technical effects:

[0036] The present invention is a crack detection method for IC package based on tomography test. The T-Scan mode based on ultrasonic scanning microscopy test can first determine the area where the cracks of the IC package are initially distributed, which is convenient for determining the crack development range of the IC package. On this basis, the cross section corresponding to the maximum crack area can be obtained according to the crack distribution information determined in the X direction, Y direction and Z direction. This is used as the main plane to facilitate CT scanning to obtain a cross-sectional scanning image of the package containing cracks with high imaging accuracy. At the same time, it is necessary to ensure that the interfaces of different parts of all IC packages are covered, so as to ensure the accuracy of the data. In order to ensure the accuracy of the CT scanning data, when there is a large degree of crack space variation in adjacent scanning images, it is necessary to perform additional CT scanning to obtain a high-precision CT scanning cross-sectional data set. The combined use of ultrasonic scanning microscopy testing and CT scanning testing reduces the cost and difficulty of obtaining high-precision cross-section scanning imaging data of cracked packages. When performing CT scanning testing, the present invention fully considers the three-dimensional model structural characteristics of the components to be subsequently constructed, rationally arranges the test section positions, performs intensive scanning in the crack development area, and performs fixed-point scanning at the package structure interface, thereby improving the accuracy of the crack section scanning results, ensuring the data foundation for accurate modeling, and making the three-dimensional model structural information of the package subsequently established complete.

[0037] Furthermore, the present invention establishes a three-dimensional spatial coordinate system based on the parameter characteristics of the package itself, and performs various profile scans according to the reference spatial coordinate system, which facilitates the organization and analysis of imaging data sets. For crack systems with complex details, profile scanning imaging with increased density can be clearly performed, thereby enhancing the accuracy and practicality of the imaging data of this method. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention is a flowchart of establishing a three-dimensional model of an IC package body containing cracks based on the IC package body crack detection method of the present invention.

[0039] Figure 2 It is a main plane overall flow chart of determining the extension space of the crack of the package body according to the present invention.

[0040] Figure 3 It is a flow chart of the present invention for determining the spatial distribution characteristics of cracks in a package based on ultrasonic scanning microscopy testing.

[0041] Figure 4 It is a flow chart of the present invention for determining the position of the main plane of the crack extension space of the package based on ultrasonic scanning microscopy testing.

[0042] Figure 5 It is a schematic structural diagram of the crack-containing package of the present invention.

[0043] Figure 6 for Figure 5 Schematic diagram of the crack distribution range of the structural schematic diagram described in FIG.

[0044] In the figure: 1 is the inner surface of the crack-containing package; 2 is the crack development range in the package; 3 is the structure of a certain type of crack in the package; 201 and 202 are the two boundary surfaces of the crack development range in the Y-axis direction; 203 and 204 are the two boundary surfaces of the crack development range in the X-axis direction; 205 and 206 are the two boundary surfaces of the crack development range in the Z-axis direction. DETAILED DESCRIPTION

[0045] The present invention is described in detail below in conjunction with the accompanying drawings. It should be noted that, in the description of the present invention, the following specific embodiments cannot be understood as limiting the present invention, but are only applicable to the explanation of the present invention.

[0046] The present invention is a method for detecting cracks in an IC package based on computer tomography testing. Figure 1 As shown, the following steps are included:

[0047] S1: Determine the appropriate packaging form, package the bare chip, and after completing the corresponding packaging process, form a finished IC package.

[0048] S2: After the finished IC package (hereinafter referred to as package) has completed the packaging process, it is necessary to screen out the finished products containing cracks.

[0049] Specifically, cracks that extend inward from the outer surface of the package or internal cracks that extend to the surface of the package can be screened out through visual inspection tests; further, cracks whose main structure is completely inside the package can be screened out using the S3 test method.

[0050] S3: After screening out the packages with cracks, ultrasonic scanning microscopy test is performed on the packages to be tested. The SAT used has multiple working modes, which can be divided into reflection type and transmission type according to the way of receiving high-frequency ultrasonic information. In the reflection type working mode, the high-frequency ultrasonic transmitting device and the receiving device are on the same side of the sample, and the information of the reflected wave is mainly used for analysis and detection. The scanning result is relatively accurate, but it is necessary to scan both sides of the sample separately to determine all the crack information in the sample; in the transmission type working mode, the high-frequency ultrasonic transmitting device (ultrasonic transmitter) and the receiving device are symmetrically distributed on both sides of the sample. All the crack information inside the sample can be determined by scanning once, but the specific layer of the crack cannot be determined.

[0051] According to the scanning method, SAT can be divided into the following main working modes:

[0052] A-Scan mode, where the horizontal axis of the display is the propagation time or propagation distance of the high-frequency ultrasonic wave in the sample, and the vertical axis is the amplitude of the reflected wave of the ultrasonic wave, which can determine the depth position of the crack in the sample in the direction of the high-frequency ultrasonic wave emission;

[0053] In B-Scan mode, the scan result on the display is a two-dimensional image, and the imaged section is parallel to the direction of sound wave propagation and perpendicular to the sample surface on the side where the detection device is located;

[0054] In C-Scan mode, the display result is still a two-dimensional graphic, representing the sample cross-section image at a certain depth parallel to the sample surface on the side where the detection device is located;

[0055] In TAMI scanning mode, the ultrasonic transmission and reception mode is consistent with C-Scan, but the scanning section is multi-layer;

[0056] T-Scan is a full transmission scanning mode that can detect cracks within the entire package.

[0057] Through cross-sectional scanning in various modes, crack distribution information such as the number of cracks in the package, the location of the main crack, and the distribution range of the crack system can be determined.

[0058] In order to detect the spatial distribution characteristics of cracks in the package, the following technical process is used:

[0059] S31: First, the sample to be tested is pre-treated before ultrasonic scanning microscopy testing, that is, the sundries on the surface are removed to ensure the accuracy of the ultrasonic scanning microscopy testing.

[0060] S32: Quantitatively characterize the spatial characteristics of the cracks in the package according to ultrasonic scanning microscopy tests in different modes. The specific process is as follows:

[0061] S321: First, the T-Scan mode is used to perform a transmission scan of the entire package body, and the position and extension range of the crack in the package body space are preliminarily analyzed so as to narrow the subsequent scanning range and obtain the preliminary distribution area Q of the crack.

[0062] The package is generally in the shape of a cuboid, and a corresponding spatial reference coordinate system can be established. Since the ultrasonic transmitter scans vertically from top to bottom, the axial direction of the ultrasonic transmitter is the Z axis, that is, the thickness direction of the package, and the horizontal plane with the Z axis as the normal direction is the XY plane, that is, the length and width directions of the package are the X axis and Y axis respectively. Correspondingly, a vertex at the bottom of the package is the intersection of the coordinate system, such as Figure 5 shown.

[0063] Specifically, when two adjacent opposite sides on the surface of the package are taken as the longitudinal and transverse reference directions, if the lengths of the two opposite sides are not equal, the shorter opposite side of the package is the longitudinal direction (Y axis) and the longer opposite side is the transverse direction (X axis); if the surface of the package is a square, the main chip in the package is taken as the reference, the shorter opposite side of the main chip surface is the longitudinal direction, and the longer opposite side is the transverse direction.

[0064] S322: Based on the scanning results of the T-Scan mode, a B-Scan profile scan is performed in the X-axis direction with the X-axis as the normal. The starting and ending positions of the scan are located on both sides of the region Q. First, the extension boundary range of the crack on both sides of the X-axis direction is determined. The scanning density of the B-Scan mode is increased within this range. The scanning interval can be changed to 1 / 100 of the original scanning interval. In this way, it is determined whether the crack is close to the left or right position in the original scanning interval, and the precise position of the crack boundary in the specific X direction is determined, that is, Figure 6 Boundary surface 203 and boundary surface 204 in.

[0065] S323: Based on the scanning results of the T-Scan mode, a B-Scan profile scan is performed in the Y-axis direction with the Y-axis as the normal. The starting and ending positions of the scan are located on both sides of the region Q. First, the extension boundary range of the crack on both sides of the Y-axis direction is determined. The scanning density of the B-Scan mode is increased within this range. The scanning interval can be changed to 1 / 3 of the original scanning interval. In this way, it is determined whether the crack is close to the left or right position in the original scanning interval, and the exact position of the crack boundary in the specific Y direction is determined, that is, Figure 6 Boundary surface 201 and boundary surface 202 in.

[0066] S324: Based on the scanning results of the T-Scan mode, a C-Scan profile scan is performed in the Z-axis direction with the Z-axis as the normal. The starting and ending positions of the scan are located on both sides of the region Q, respectively. The extension boundary range of the crack on both sides of the Z-axis direction is determined. The scanning density of the C-Scan mode is increased within this range. The scanning interval can be changed to 1 / 3 of the original scanning interval. In this way, it is determined whether the crack is close to the left or right position in the original scanning interval, and the precise position of the crack boundary in the specific Z direction is determined, that is, Figure 6 Boundary surface 205 and boundary surface 206 in.

[0067] S325: Therefore Figure 3 As shown in the figure, based on the scanning results of the fracture boundary profiles in three axes, the fracture range boundary is determined, the fracture boundary position is recorded, and the precise fracture development range is obtained. A certain approximate shape of the fracture can be referred to Figure 6 The three-dimensional area enclosed by the dotted line.

[0068] S33: Within the crack development range of the package, based on the boundaries in the three directions determined in S32, ultrasonic scanning microscopic tests with different working modes are performed internally, such as Figure 2 As shown, the test results are comprehensively compared and the main plane spatial position of the crack is determined. The specific process is as follows:

[0069] S331: Starting from a boundary of the package crack extension range in the X direction in the spatial reference coordinate system, a B-Scan mode profile scan is performed at equal intervals within the crack range along the X direction to obtain crack distribution information in the X direction.

[0070] S332: In the Y direction of the spatial reference coordinate system, starting from a boundary of the package crack extension range in this direction, a B-Scan mode profile scan is performed at equal intervals within the crack range along the Y direction to obtain crack distribution information in the Y direction.

[0071] S333: Starting from a boundary of the package crack extension range in the Z direction in the spatial reference coordinate system, perform C-Scan mode profile scans at equal intervals within the crack range along the Z direction to obtain crack distribution information in the Z direction.

[0072] Specifically, when performing cross-sectional scanning imaging in various directions, if the cross-sectional scanning density needs to be increased, a cross-sectional scanning test is added at the middle position of the current minimum scanning interval, and cross-sectional scanning in various directions is performed progressively in this way.

[0073] S334: Therefore Figure 4As shown, the profile scanning data groups in various directions are sorted out, the crack area size in each profile scanning result is compared, and the maximum crack area Z in the Z-axis direction under C-Scan mode is selected. max The cross section of the image is taken and the maximum crack area X in the X-axis and Y-axis directions in B-Scan mode is selected. max , Y max cross section.

[0074] S335: Compare the scanned data of the sections with the largest crack areas in the three directions and select the section A with the largest area. max , take this plane as the main plane of the package crack and record the spatial position of the main plane.

[0075] S4: After performing ultrasonic scanning and microscopic scanning on the cracks of the package and determining the main plane of the cracks, perform CT scanning test on the package to obtain a cross-sectional scanning image of the package containing cracks with high imaging accuracy. CT uses X-ray, gamma ray and other ray beams to scan a certain layer of the sample to be tested. The detector receives the ray beam that passes through the plane to be tested and converts it into visible light. The optical signal is then converted into an electrical signal, which is then converted into a digital signal through a digital converter and input into a computer for imaging.

[0076] First, the main plane of the package crack is imaged by CT section, and then the main plane is used as the reference plane, and CT section imaging scans are performed on both sides of the main plane at a certain distance, and all scan sections are parallel;

[0077] During the CT scanning process on both sides of the main plane, the scanning interval within the crack range is small, and the scanning interval outside the crack range is large. If the scanned section does not cover the interface of different parts of the package, such as the junction of the chip and the plastic packaging material, if no section imaging is performed, it is necessary to perform a separate CT scan at the interface corresponding to different parts according to the structural parameters of the package, so as to obtain the interface imaging data of the model in the package body, and ensure the integrity of the package structure during the subsequent three-dimensional model reconstruction. Image processing software is used to perform image threshold segmentation processing on the obtained CT scanning section data according to the pixel grayscale value, and the crack area and package area of ​​each image are subdivided, and the noise in the image is removed. The crack area and package area in the image are distinguished. In order to obtain more accurate CT scanning section data, if the crack area in the section scan in the crack area of ​​the package body accounts for more than 10% of the package area, a supplementary scan is performed at the midpoint position of the adjacent sections on both sides of this scanning section to obtain the initial CT section scanning data set.

[0078] S5: The CT section scanning data set obtained in S4 is processed twice using relevant mathematical methods in fractal geometry, that is, the crack areas in adjacent CT section scanning images are compared to determine the crack space variation between adjacent CT section scanning positions, and based on the result, it is determined whether supplementary scanning is required between adjacent images. If the first several crack space variations after sorting by size are greater than the set value, supplementary scanning is required at the midpoint position of the corresponding two adjacent images until the maximum value of the crack space variation of the newly added scanning section is within the set value.

[0079] The specific process of judging the spatial variation of the fissures in adjacent CT section scans is as follows: The box-counting dimension calculation formula in fractal geometry is as follows:

[0080]

[0081] Where dim box (S) is the box-counting dimension, ε is the side length of the square block used to measure the fractal, and N(ε) refers to the number of square blocks with a side length of ε required to completely cover the fractal pattern.

[0082] Define the crack space variation between adjacent CT scan section images as C, and define the crack boundary complexity in adjacent images as D1 and D2 respectively. The maximum aperture of the smallest crack in two adjacent images is d. Then the ε value of adjacent images is determined by the following formula:

[0083] ε=d / n

[0084] Where n is the target accuracy, and the complexity of the crack boundary of adjacent images can be determined by the following formula:

[0085] D i =log (1 / ε) N i (ε)

[0086] Where N i (ε) is the number of square blocks with a side length of ε required to completely cover the crack area in the corresponding CT scan section image after the target accuracy is determined, i = 1 or 2, 1 corresponds to one of the scan images, and 2 corresponds to the other scan image.

[0087] According to the above formula, the complexity of crack boundaries D1 and D2 of adjacent images are calculated respectively, and the crack space variation between adjacent images is determined by the following formula:

[0088] C=|D1-D2|

[0089] When judging whether adjacent CT scan profiles need to be supplemented with scans, the target accuracy n is first determined, and the crack space variation of the initial CT scan profile image in the crack area is calculated according to the method, sorted by size, and the first several adjacent profile images with crack space variation greater than a set value are selected, and supplementary scans are performed at the midpoints of these adjacent profile images, and the crack space variation of the newly added scanned profile is calculated. After sorting and supplementary scanning are performed according to the method, after several supplementary scans, the maximum value of the crack space variation of the newly added scanned profile can be made within the set value, thereby obtaining a high-precision CT scan profile data set.

[0090] S6: The final cross-sectional scanning data set is imported into the three-dimensional reconstruction software, and various image processing algorithms built into the three-dimensional reconstruction software are used to reconstruct the cross-sectional scanning image of the cracked package into a three-dimensional model.

[0091] Example

[0092] The present invention provides an IC package crack detection method based on computer tomography testing, which can be used to establish a three-dimensional model of a package containing cracks, and mainly comprises the following six steps:

[0093] S1: Determine whether to use substrate packaging or frame packaging based on the packaging product requirements, and record the packaging form used by the product and the number of chips in the packaging product, combination method and other basic information. At the same time, record the basic structural parameter information of the packaging components such as chips and plastic packaging bodies as basic background information, measure and record the package body length L, package body width W, and package body thickness H.

[0094] S2: Use visual inspection to select packages with cracks inside as samples to be tested.

[0095] S3: Process the surface of the sample to be tested, remove debris on the surface of the package to be tested and the ultrasonic transmitter on the same side to ensure the accuracy of the cross-sectional scanning results. In the process, different scanning modes and corresponding channel energies need to be set according to different steps, and the ultrasonic scanning microscopy test equipment is initialized. According to the package size measured in S1, the appropriate scanning area size is set.

[0096] First, the T-Scan mode is used to perform transmission scanning on the entire package to preliminarily analyze the position and extension range of the crack in the package space and obtain the preliminary distribution area Q of the crack.

[0097] According to the scanning results of the T-Scan mode, the B-Scan mode profile imaging scan is performed on the approximate boundary range of the crack in the Y-axis and X-axis directions respectively with the Y-axis and X-axis directions of the reference space coordinate system as the normal direction to determine the boundary range of the cracks on both sides in the two directions. According to the scanning results of the T-Scan mode, the Z-axis direction of the reference space coordinate system is used as the normal direction to determine the boundary range of the cracks on both sides in the Z-axis direction under the C-Scan mode profile scanning imaging, and the starting and ending positions of the scan are located on both sides of area Q respectively. The scanning intervals of each pair of adjacent profile imaging are 1 / 10L, 1 / 10W, and 1 / 10H respectively, and the interval between each two adjacent profile imaging is recorded as J. i , i = X, Y or Z, that is, the interval between every two adjacent profile imaging in the three axes. When performing profile imaging scanning with increasing density, in 1 / 2J i Supplementary cross-sectional imaging scans were performed at the same location.

[0098] The position of the crack boundary of the package determined by the profile scan is recorded, and the profile scans of the B-Scan working mode and the C-Scan working mode are performed in the three directions within the crack range determined in the X-axis, Y-axis and Z-axis directions. The scanning intervals in the three directions are one tenth of the lengths of the corresponding crack development areas in the three directions. The profile scan imaging results in the three directions are sorted out, and the profile image with the largest crack area in the three directions is determined by comparison. The scanning position of this profile is recorded, and this plane is the main plane A of the crack. max .

[0099] S4: After determining the main plane within the crack development range, a CT test is performed. First, the main plane of the cracked package is scanned and imaged. Then, CT imaging scans are performed at different intervals on both sides of the main plane with the main plane as the reference plane. CT imaging scans with different intervals are performed inside and outside the crack extension range of the package. The scanning intervals within the crack extension range are 1 / 30L, 1 / 30W and 1 / 30H respectively, and the scanning intervals outside the crack range are 1 / 10L, 1 / 10W and 1 / 10H. If the chip and plastic encapsulation material interface positions of different structural parts parallel to the CT scanning section in the package are not assigned with profile scanning imaging, then a supplementary scan is performed at the corresponding position to accurately obtain the profile imaging data of the interface in the package. The obtained CT profile scanning imaging data is image processed to distinguish the crack area and the package area. If the area of ​​the crack area in the scanned section accounts for more than 10% of the package area, a supplementary scan is performed at the middle point of the profile scan on both sides of the adjacent section to finally obtain the initial scan profile data set.

[0100] S5: Sort and classify the acquired CT profile scanning imaging data, determine the target accuracy n of the initial profile scanning image within the crack development range, and calculate the crack space variation C between adjacent images in the crack development area based on the selected target accuracy, count and record the crack space variation calculation results of the initial profile scanning, sort them in order from large to small according to the crack space variation, perform supplementary scanning at the middle point position of adjacent scanning profiles corresponding to the top 50% of the largest crack space variation, then recalculate the crack space variation in the newly added supplementary scanning profile area and record and organize, screen according to the method, perform ten cycles of supplementary scanning, and finally form a high-precision profile scanning imaging data set of cracked package.

[0101] S6: The functions of modeling and simulation software have been greatly expanded, which provides a basis for establishing a comprehensive test method to fully describe the cracks in the package, and further helps to explore the failure mechanism of the package during production and use. However, it is necessary to accurately transfer the structural information of cracks and delamination failure in the package to the simulation software, and establish an accurate three-dimensional package model including the failure structure based on multi-type tomography comprehensive tests.

[0102] Import the various CT section scanning imaging data sets obtained into the 3D reconstruction software AVIZO. After the loaded data set is selected, the basic information of the data set, such as the type of original data, coordinate type, and voxel size, can be viewed in the Properties Area column. After loading various CT section scanning imaging data, set various image parameter information in the Image ReadParameters dialog box that appears. The Crop item can be used to trim the CT section scanning imaging data set. The Filtering algorithm can be used to reduce noise on the trimmed scanning imaging data set to enhance the presentation of the characteristic structure of cracks in the package. The Thresholding option can be used to perform threshold segmentation on the obtained scanning imaging data set to enhance the image features of each structure in the package for distinguishing modeling. The 3D Reconstruction sub-item in the Reconstruction item in the menu bar can start the 3D reconstruction, and set the specific parameters of the package to be reconstructed in the pop-up window. The Algebraic Reconstruction Technique algorithm can be used to perform 3D reconstruction of the model, and the Measure and Analyze functions can be used to cyclically correct and reconstruct the 3D reconstruction results. Finally, a complete and accurate package model with cracks is established, which can comprehensively describe the cracks in the package and provide a basis for subsequent simulation experiments and failure analysis.

[0103] Although the present invention discloses the above technical contents, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for detecting cracks in an IC package based on tomography testing, characterized in that: The steps include: S1, firstly, using the T-Scan mode of ultrasonic scanning microscopy to perform transmission scanning on the IC package to be tested, to obtain the area Q where cracks of the IC package are initially distributed, and then determining the precise crack development range of the IC package based on the area Q; S2, performing ultrasonic scanning microscopic test scans at equal intervals in the X direction, Y direction and Z direction of the crack development range to obtain crack distribution information in the X direction, Y direction and Z direction, and recording the section corresponding to the maximum crack area in all section scanning results as the main plane O of the IC package crack; S3, performing CT scanning inside and outside the crack development range at a fixed interval on both sides of the main plane O, and then performing CT scanning on different parts of the interface of the IC package that are not covered by the separate CT scanning, and finally distinguishing the crack area and the package area of ​​each scanned image to obtain a CT scanning data set; S4, comparing the crack areas in adjacent scanned images in the CT scan data set to obtain a series of crack space variation data. If all the crack space variation degrees are within the set value, the detection of IC package cracks is completed. If there is a crack space variation degree greater than the set value, a supplementary CT scan is performed between the corresponding adjacent scanned images until all the crack space variation degrees are within the set value, thereby obtaining a new CT scan data set and completing the detection of IC package cracks.

2. The IC package crack detection method based on tomography testing according to claim 1, characterized in that: S1 performs ultrasonic scanning microscopic testing along the X direction, Y direction and Z direction of the region Q to determine the precise crack development range of the IC package. The determination of the X direction, Y direction and Z direction is as follows: The IC package is a rectangular parallelepiped, the Z direction is the thickness direction of the IC package, if the length and width of the IC package are not equal, the X direction is the length direction of the IC package, and the Y direction is the width direction of the IC package; if the length and width of the IC package are equal, the X direction is the direction of the long opposite side of the main chip surface in the package, and the Y direction is the direction of the short opposite side of the main chip surface in the package.

3. The IC package crack detection method based on tomography testing according to claim 2, characterized in that: S1 performs B-Scan profile scans with equal intervals in the X direction with the X axis as the normal. The starting and ending positions of the scan are located on both sides of the X direction of region Q to determine the extension boundary range of the crack in the X direction. Then, the scan interval is shortened to perform profile scanning to obtain the development range of the crack in the X direction. Perform B-Scan profile scans with equal intervals in the Y direction with the Y axis as the normal. The starting and ending positions of the scan are located on both sides of the Y direction of region Q to determine the extension boundary range of the crack in the Y direction. Then, shorten the scanning interval to perform profile scanning to obtain the development range of the crack in the Y direction. A C-Scan profile scan with equal intervals and the Z axis as the normal is performed in the Z direction. The starting and ending positions of the scan are located on both sides of the Z direction of area Q to determine the extension boundary range of the crack in the Z direction. Then, the scanning interval is shortened to perform a profile scan to obtain the development range of the crack in the Z direction.

4. The IC package crack detection method based on tomography testing according to claim 3, characterized in that: When S1 obtains the development range of the crack in the X-axis direction, the shortened scanning interval is the time interval for determining the extension boundary range of the crack in the X-axis direction. When S1 obtains the development range of the crack in the Y-axis direction, the shortened scanning interval is the time interval for determining the extension boundary range of the crack in the Y-axis direction. When S1 obtains the development range of the crack in the Z-axis direction, the shortened scanning interval is the time interval for determining the extension boundary range of the crack in the Z-axis direction.

5. The IC package crack detection method based on tomography testing according to claim 4, characterized in that: In S2, in the X direction, starting from one boundary of the crack development range of the IC package, a B-Scan mode scan is performed in the crack development range along the X direction with equal intervals to obtain crack distribution information in the X direction; In the Y direction, starting from one boundary of the crack development range of the IC package, a B-Scan mode scan is performed in the crack development range along the Y direction with equal intervals to obtain the crack distribution information in the Y direction; In the Z direction, starting from a boundary of the crack development range of the IC package, a C-Scan mode scan is performed in the crack development range along the Z direction with equal intervals to obtain the crack distribution information in the Z direction.

6. The IC package crack detection method based on tomography testing according to claim 1, characterized in that: In S3, the CT scanning interval outside the crack development range is larger than the CT scanning interval within the crack development range.

7. The IC package crack detection method based on tomography testing according to claim 1, characterized in that: If there is a scan image in S3 in which the crack area occupies more than 10% of the corresponding cross-sectional area of ​​the IC package, a supplementary scan is performed at the midpoint position of adjacent scan images on both sides of the corresponding scan image to obtain an optimized CT section scan data set. Thereafter, the optimized CT section scan data is processed in accordance with the method of processing the CT scan data set in S4 to complete the detection of cracks in the IC package.

8. The IC package crack detection method based on tomography testing according to claim 1, characterized in that: In S4, a supplementary CT scan is performed at the midpoint position of the corresponding adjacent scan images.

9. The IC package crack detection method based on tomography testing according to claim 1, characterized in that: S4 obtains the corresponding crack space variation degree from two adjacent scan images according to the following process, and then obtains a series of crack space variation degree data from adjacent scan images in the CT scan data set: Assuming that the maximum aperture of the smallest crack in two adjacent scanned images is d, the ε value of the adjacent images is determined by the following formula, where ε is the side length of the square block used to measure fractals in fractal geometry, and n is the target accuracy: ε=d / n; The complexity of the crack boundaries of the two adjacent scanned images is determined by the following formula: D i =log (1 / ε) N i (e); N i (ε) is the number of square blocks with a side length equal to ε required to completely cover the crack area in the corresponding scanned image, i = 1 or 2, 1 corresponds to one of the scanned images, and 2 corresponds to the other scanned image; The crack spatial variation C is determined by the following formula: C = |D1-D2|.

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