KR20160006052A - Method for Inspecting a Electronic Board with X-ray - Google Patents

Abstract

The present invention relates to a method of inspecting an electronic board with X-ray and, more specifically, relates to a method of inspecting a soldering bump of an electronic board with X-ray. The method of inspecting an electronic board comprises: a step of dividing an inspection area into a plurality of sub-inspection areas; a step of obtaining images of each bumps by irradiating X-ray to the bumps formed in the sub-inspection area; a step of determining a relative size of the obtained images; and a step of determining whether there are defects or not in accordance with the relative size.

Description

[0001] The present invention relates to a method of inspecting an electronic board,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inspecting an x-ray of an electronic substrate, and more particularly, to a method of inspecting an x-ray of a soldering bump of an electronic substrate.

Soldering is the bonding of different base metal materials that require connection in the state of melting a metal or alloy with a lower melting point than the base metal to be bonded. For soldering, lead-tin alloys, lead-tin-zinc alloys, lead-cadmium, zinc-cadmium or lead-tin-bismuth alloys may be used and gold (Au) may be used in the flip- . In addition, lead free soldering processes have also been developed. The memory or large scale integrated circuit may be placed on the wafer by a soldering process or by bumps and the contact state needs to be checked since the solder or bump has a function of a path of an electrical signal.

Prior art related to bonding inspection of a substrate is disclosed in Korean Patent Laid-Open No. 2006-0094844. The prior art includes a photographing unit for photographing a substrate, a shape detecting unit for detecting an image having a correct bump shape among images representing bumps included in the object image obtained by the photographing unit, An inspection area setting unit for setting a non-inspection area as an area including an image having a correct bump shape detected by the detection unit and an area around the image as an inspection area, and setting the other area as an inspection area; And a comparison inspection unit for checking whether the bump is formed with a predetermined precision by comparing the object image and the master image with respect to the inspection area set by the inspection area setting unit, Device.

Another prior art related to bonding inspection of a substrate is disclosed in Korean Patent Laid-Open Publication No. 2009-0069838. In the wafer bumping process, there is an apparatus and a method for inspecting solder bump formation and static state using an electron beam. The prior art includes electron beam emitting means for emitting an electron beam to a target object; Deflection and acceleration means for effecting deflection and acceleration of the electron beam; A detector for detecting electrons emitted from the object by the electron beam and converting the detected electrons into an electrical signal; And a signal processing unit for processing the electrical signal from the detector to generate information on an arrangement state of the metal material formed on the object, wherein the object includes a template having a plurality of solder bumpers formed thereon, A circuit board having a plurality of electrode pads connected to a semiconductor wafer or an electric circuit formed with transferred solder bumps, a circuit board having a plurality of test terminals in the form of a plurality of electrode lines or solder bumpers, A plurality of solder bumps formed on the circuit board, solder bumps formed on the semiconductor wafer, or a plurality of test terminals formed on the circuit board, From the electrical signal, That of generating the electrical characteristics relating to the operation is started with respect to the testing device according to claim.

Another prior art related to bonding inspection of a substrate is disclosed in Korean Patent Laid-Open Publication No. 2009-0069851. In the wafer bumping process, there is an apparatus and a method for checking solder bump formation and transition state using thermal imaging. The prior art includes an infrared ray sensing means for sensing infrared rays emitted from a target and converting the infrared rays into an electrical signal and a data processing unit for processing the electrical signals to produce image information related to the temperature distribution with respect to the arrangement of the metal materials formed on the target object And the object is in the form of a flat plate including a metal material formed at a plurality of positions.

The method disclosed in the prior art is disadvantageous in that it is difficult to inspect substantially invisible portions and it is difficult to thoroughly inspect a predetermined portion of the substrate such as a bump.

The present invention has been made to solve the problems of the prior art and has the following purpose.

Prior Art 1: Patent Publication No. 2006-0094844 (published on August 30, 2006) Prior Art 2: Patent Publication No. 2009-0069838 (published on 01.07.2009) Prior Art 3: Patent Publication No. 2009-0069851 (published on July 01, 2009)

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray inspection method of an electronic substrate which enables precise inspection of a soldering bumper formed on an electronic substrate.

According to a preferred embodiment of the present invention, an inspection method for an electronic substrate includes dividing an inspection area into a plurality of sub-inspection areas; Irradiating the bumps formed in the sub-inspection region with an x-ray to obtain an image for each bump; Determining a relative size of the acquired image; And determining from the relative size whether a defect is caused.

According to another suitable embodiment of the present invention, the step of judging whether or not the defect includes the step of determining the suspect bump and the step of obtaining at least one directional cross-sectional image with respect to the suspect bump.

According to another preferred embodiment of the present invention, the bumps are arranged in a memory chip or a flip chip.

According to another preferred embodiment of the present invention, at least one directional cross-sectional image is obtained by irradiating the x-ray in a direction different from the direction of irradiation for acquiring an image for each of the bumps.

According to another preferred embodiment of the present invention, at least one directional cross-sectional image is obtained by causing the suspected bump to rotate at a predetermined position.

The inspection method according to the present invention has an advantage that it is possible to perform thorough inspection of each bump formed on an electronic substrate and to inspect the entire bump formed in a required area. In addition, the method according to the present invention has the advantage that inspection of the bumps applied to a substrate bonding method such as a flip-chip is enabled.

FIG. 1A shows an embodiment of a process applied to an inspection method according to the present invention.
1B shows an embodiment of an inspection structure that can be applied to the inspection process of 1a.
FIG. 2A illustrates an example of an x-ray image of an object to be inspected, which is shown in an inspection process according to the present invention.
FIG. 2B shows another embodiment of an X-ray image of an object to be inspected, which is shown in the inspection process according to the present invention.
FIG. 2C shows an example of the inspection result according to the inspection method according to the present invention.
FIG. 3 illustrates an example of a process for determining whether a defect is detected in the inspection method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings, but the present invention is not limited thereto. In the following description, components having the same reference numerals in different drawings have similar functions, so that they will not be described repeatedly unless necessary for an understanding of the invention, and the known components will be briefly described or omitted. However, It should not be understood as being excluded from the embodiment of Fig.

FIG. 1A shows an embodiment of a process applied to an inspection method according to the present invention, and FIG. 1B shows an embodiment of an inspection structure applicable to an inspection process of FIG. 1A.

Referring to FIG. 1A, an inspection method of an electronic board according to the present invention includes: (S11) dividing an inspection area into a plurality of sub-inspection areas; Irradiating the bumps formed in the sub-inspection region with an X-ray (S12) to obtain an image for each bump (S13); Determining a relative size of the obtained image (S141); And determining from the relative size whether a defect is caused. In addition, the step of determining the defect in the inspection method according to the present invention includes a step (S142) of determining a suspect bump and a step (S15) of obtaining at least one directional cross-sectional image with respect to the suspect bump.

In the present description, a directional sectional image or a rotated image is used in the same or similar meaning. And the whole image means one image obtained in one direction with respect to the object to be inspected. On the contrary, the directional cross-sectional image means an image cut in a specific direction by a device such as a computer, for example, in order to obtain an entire image with an image viewed from a specific direction. At least two directional cross-sectional images can be made into an entire image by Back Projection. According to the description, the directional cross-sectional image or the rotated image means one cross-sectional image, or the whole cross-sectional image may be a composite image.

The inspection method according to the present invention can be applied to, for example, a bonding inspection of a memory chip of an electronic substrate or a bonding inspection of a high-density integrated circuit (LSI), but is not limited thereto. Further, the inspection method according to the present invention can be applied to inspection of a solder bump of a flip chip. As described above, the inspection method according to the present invention can be applied to various soldering bonding tests applied to a semiconductor process, and the present invention is not limited to an inspection object.

The number of sub-inspection regions can be determined according to the size of chips or wafers to be inspected. Also, the size of the sub-scan region can be determined by the irradiation capability of the x-ray tube and the detector, but the sub-region can be set by various methods (S11). For example, the sub-area may be set according to the moving structure of the x-ray tube and detector or the moving structure of the inspection stage. On the other hand, the sub-area can be determined as a sample pattern. For example, when it is difficult to perform a full inspection on an object to be inspected, the irradiation region is divided first, and a sample region may be set for each divided region and selected as a sub region. The number of bumps or bonds included in each sub-region may be the same or different, and the geometry or size of each sub-region may be the same or different. Thus, the present invention is not limited by the geometry of the sub-areas.

When the region is divided and the sub-region is determined (S11), the x-ray inspection for bumps or bonding included in the sub-region may proceed. The x-ray inspection for the sub-area may be made for the entire bump included or in the form of a sample inspection. In order to inspect the bump defect, the x-ray region inspection may be performed first (S12).

In the present specification, area inspection means inspection of a plurality of inspection objects in a sequence in the sub-area. By the area inspection, the defective bump or suspect inspection object can be detected. For example, in order to inspect the area, the x-ray tube may be positioned vertically with respect to the bump or bonded substrate to be inspected so that the x-ray is irradiated from the upper ceiling portion of the object to be inspected through the bottom portion. In such an inspection method, the image obtained by the detector can be a top view from the ceiling of the inspection target, viewed from the bottom surface.

1B, an inspection object B1 formed on an electronic substrate or a chip can be disposed on an inspection stage 13 having a planar surface, and an X-ray tube 11 can be disposed above the inspection stage 13 have. And the detector 12 may be disposed below the inspection stage 13. [ In this structure, a top view image of the inspection target B1 in the detector 12 can be obtained by the X-ray X1 irradiated from the X-ray tube 11 (S13). The image for the sub-area can be obtained by dividing the area again. Specifically, a primary image for each inspection object B1 existing in the sub-area can be obtained while the x-ray tube 11 and the detector 12 are moved parallel to the inspection stage 13 on the sub-area (S13). The normal bump, the bad bump, and the suspect inspection object can be discriminated from the image obtained by the detector 12 with the unique identification number assigned to each inspection object B1 in the sub area (S141, S142). Depending on the shape or layout of the inspection object, it may be judged from the primary image whether it is defective or not. For example, in the case of a bump of a memory chip, a defect may be determined from the primary image (S141). On the other hand, in the case of a bump of a high-density integrated circuit or a flip chip, it can be judged whether or not it corresponds to the normal from the primary image, but it may not be clear whether or not it is defective. In such a case, it can be classified as a suspicious object and needs to be further inspected (S142). However, the bump of the high-density integrated circuit is not judged to be defective from the primary image. Specifically, it is clear whether the normal or defective can be judged from the primary image directly or the normal or defective can be judged immediately according to the shape or the arrangement structure of the inspection target, but it is further clarified whether it corresponds to the normal state or the defective state There may be objects to be inspected. In this way, an additional inspection can be performed on the inspection object to be suspected of badness.

The detection of the suspect object may be determined for each object B1 from the area inspection image and a unique identification number for the suspect object may be stored in a storage medium associated with the control unit, for example. The suspicious subject can be determined stochastically and can be determined according to a predetermined criterion. For example, a reference image may be prepared and the size of the reference image and the image of the object to be inspected B1 may be compared. If the difference in image size is 5% or 10% or more, it can be classified as suspect. Alternatively, the subject of the suspicious test may be determined by the brightness of the specific region. For example, when the detected image becomes circular, the suspicious object can be detected by comparing the shade of the outer part with the reference image. As another alternative, suspect objects can be detected by the geometric shape of the detected image. Suspect objects can be detected in various ways, and the present invention is not limited to the embodiments shown.

If a suspicious inspection target is detected (S142), the directional cross-sectional image inspection may be performed on the suspect inspection target (S15).

The directional cross-sectional image inspection refers to judging whether or not the inspection object is defective from the image obtained in a plurality of directions. The directional cross-sectional image inspection refers to an inspection method for accurately obtaining the entire image from a plurality of directional cross-sectional images or rotated images and determining whether the inspection object is defective or not based on the obtained whole image. Such an examination method is similar to computed tomography (CT).

Referring to FIG. 1B, the detector 12 may be positioned in an inclined direction with respect to the x-ray tube 11. The suspect examination object B 2 can be positioned on the side surface of the x-ray tube 11. The X-rays irradiated from the X-ray tube 11 in the detector 12 can be detected, and an image obtained in such an arrangement structure can be a sectional image along a specific direction.

In the present specification, the inspection process in which the x-ray tube 11 and the detector 12 are arranged in such a tilted direction and thereby obtains a cross-sectional image is referred to as a tilt inspection. Two detectors 12 may be disposed at different positions on the frame member 15 for the tilt inspection or the detector 12 may be installed to be movable along the frame member 15. [ On the other hand, the x-ray tube 11 may be rotatably installed as needed. The moving position of the suspect inspection object B2 in the inspection stage 13 can be determined in advance.

When the position is determined and the inspection target B2 is moved, a plurality of directional sectional images can be obtained while the inspection stage 13 is rotated at a predetermined position. And one composite image can be obtained by back projection of a plurality of directional cross-section images. Then, it is judged whether or not the object to be inspected is defective based on the obtained composite image (S16).

As described above, a unique identification number is assigned to each bump and a unique identification number of the suspect inspection object B2 can be extracted. And the position of the suspicious inspection object B2 in the sub-region and the sub-region in which the suspect inspection object B2 exists can be determined. When the position of the suspect inspection object B2 is determined, the movement or rotation angle of the inspection stage can be determined accordingly. And the movement or rotation angle of the X-ray tube 11 can be determined. The detection position of the detector 12 with respect to the x-ray tube 11 can also be determined. A plurality of tilt tests may be performed on one suspect test object B2 and a plurality of suspect test objects B2 or sub-regions including the suspect test object B2 may be simultaneously or continuously inspected.

If a plurality of directional cross-sectional images are obtained for the suspect test object and an entire image is obtained from the plurality of directional cross-sectional images (S15), whether or not the suspect test object is defective can be determined (S16). The defect of the inspection object means that the inspection object does not have a predetermined shape and means that the bump is not formed on the electronic substrate in a proper shape, for example. The defect criteria of various shapes can be determined according to the inspection object B1. Such normal or badness can be determined by predetermined data.

An inspection object to which the inspection method according to the present invention can be applied will be described below.

FIG. 2A illustrates an example of an x-ray image of an object to be inspected, which is shown in an inspection process according to the present invention.

2A shows an example of a bump that can be determined to be defective in the memory, and FIG. 2A (B) shows an example of a bump that can be determined to be normal in the memory.

The embodiment shown in Fig. 2A shows an embodiment according to the result of a region check, for example a vertical inspection.

The normal bump BP1 and the suspicious bump BP2 can be determined according to the result of the area inspection. Then, the slope inspection can be performed on the suspicious bump BP2.

The size of the contact portion SC2 of the suspect bump BP2 with respect to the substrate S is small and the size of the contact portion SC1 with respect to the substrate S of the normal bump BP2 is large. The images detected and changed by the detectors of the bumps BP1 and BP2 have different shapes as shown below. Specifically, the size of the whole image of the suspicious bump BP2 may be smaller than that of the normal bump BP1. Specifically, the normal image BI1 of the normal bump has a size similar to that of the actual bump. In contrast, the defective image (BI2) of the defective bump has a smaller size than the actual bump. The criterion for the size, contrast ratio, or brightness difference of the entire image determined by the suspicious bump BP2 can be predetermined.

The normal bump BP1 and the defective bump BP2 may or may not be determined from the primary image depending on the shape or arrangement of the bumps to be inspected. For example, in the case of a bump of a memory chip, the normal bump (BP1) and the defective bump (BP2) can be determined from the primary image, but in the case of the bump of the high density integrated circuit, the defect may or may not be determined from the primary image. An object to be inspected may not be subject to suspicion.

FIG. 2B shows another embodiment of an X-ray image of an object to be inspected, which is shown in the inspection process according to the present invention.

(A) and (b) of FIG. 2B show defect types that can be generated in the flip chip, respectively. The flip chip may be formed with bumps BP1 and BP2 of flip chip, and the spare bumps may be formed on the two substrates S1 and S2 facing each other and the two spare bumps may be joined together. For the bumps (BP1, BP2) of this type, differences in the contrast ratio may occur between the central portion and the peripheral portion due to the difference in transmittance depending on the density of the x-rays. The bump (BP2) to be subjected to the suspicious inspection can be detected by the area inspection. Then, the tilt inspection can be performed on the bump (BP2) subject to the suspicion inspection.

The bumps BP1 and BP2 formed in the flip chip can be subjected to a tilt test without performing a vertical inspection for the area inspection. As shown in Fig. 1 (c), the slope inspection can be performed by obtaining a plurality of directional cross-section side images and obtaining the entire image BP. Specifically, at least one directional cross-sectional image can be obtained and an entire image BP from at least one directional cross-sectional image can be obtained. At least one side image means a sectional image, and a plurality of side images may be used to form a preliminary composite image (sinogram). Then, the entire image BP can be formed by combining the preliminary synthesized images (back projection).

According to the present invention, a vertical inspection can be performed or a tilt can be performed to inspect the area of the bumps BP1 and BP2 of the flip chip. And the tilt inspection can be accomplished by obtaining at least one cross-sectional image. And a plurality of rotated images can be obtained for the tilt inspection. The rotated image means a cross-sectional image obtained at different angles and may include a cross-sectional image obtained in the vertical direction.

The rotated image or the cross-sectional image can be divided into a plurality of cross-sections according to the height of the bumps (BP). And a cross-sectional image of each cross-section can be obtained according to the rotation of the inspection stage described above. And each cross-sectional image is arranged according to the angle obtained and the entire image can be obtained by a back projection. The number of the cross-sectional images is not particularly limited and may be selected as an appropriate number to judge whether the cross-sectional image is defective or not.

FIG. 2C shows an example of the inspection result according to the inspection method according to the present invention.

2C shows a first image according to bump inspection of memory, FIG. 2B shows a bad bump image according to a bump test of a high-density integrated circuit chip, and FIG. 3C shows a normal bump image .

Referring to (A) of FIG. 2C, in the case of a bump in the memory, a defect may be determined from the primary image. The small image located in the middle portion represents the bad bump and the rest represents the normal bump. In the case of the memory bump, whether or not the memory bump is defective can be determined from the vertical inspection.

Referring to (B) and (C) of FIG. 2C, in the case of a high-density integrated circuit, the suspicious bumps are determined by the vertical inspection, and the defect is determined by synthesizing the entire image by the rotation image. (B) and (C) of FIG. 2C show the result of synthesizing a plurality of rotated images, respectively.

The number of cross-sectional images or rotated images for determining whether the defect is defective can be determined by the distance between the bumps, the size of the bumps themselves, the shape of the bumps, or the relative positions of the bumps and the substrate. On the other hand, a plurality of cross-sectional images are obtained not over one bump, but over a certain area, and a whole image is obtained for the entire certain area.

In the illustrated embodiment, the memory bump has a small number of bumps per unit area and a relatively large bump size. Thus, the defective image can be determined as one inclined image. On the other hand, in the case of a bump of a high-density integrated circuit, the number of bumps per unit area is large and the size of the bump itself is relatively small. Therefore, the entire image is created by combining a plurality of cross-sectional images and the defectiveness can be determined based thereon.

The bumps formed on various types of electronic substrates can be inspected by the method according to the present invention and the present invention is not limited to the embodiments shown.

FIG. 3 illustrates an example of a process for determining whether a defect is detected in the inspection method according to the present invention.

Referring to FIG. 3, the inspection region may be divided to determine a sub region (P31) for inspecting bumps or other types of electrical contact portions formed on the electronic substrate by the inspection method according to the present invention. However, one sub-area may be created depending on the size of the inspection area. The sub-area does not necessarily have to include all the inspection areas. The sub-region may be determined in the form of a sample. If the sub-area to be inspected is determined, the vertical inspection for each sub-area may be performed (P32). Then, it is judged whether or not the suspicious inspection object is detected by the area inspection (P321). If no suspicious inspection object is detected (NO), inspection for another area can be continuously performed. On the other hand, if a suspicious inspection object is detected (YES), the identification code for the location area can be stored (P33). The identification code can be assigned in two ways. The identification code may be given, for example, for each inspection object, or may be given according to an area made of one image. And the identification code may correspond to the position on the substrate. Thereafter, the inspection can be continuously performed, and if the area inspection is completed, the tilt inspection method can be determined according to the stored identification code (P34). The tilt inspection method can be selected according to the structure of the object to be inspected and can be inspected by a single cross-sectional image, as described above, or by an entire image by a cross-sectional image obtained at multiple locations. When the inspection method for the object is determined, the rotation position can be determined (P35). The determination of the rotational position means a position at which a rotational image capable of obtaining an image for a failure determination can be obtained. When one cross sectional image is obtained, one rotation position can be determined and the rotation angle can be determined at one inclination position when a plurality of rotation images have to be obtained. Such a rotational position can be determined in advance by the structure of the object to be inspected and can be determined according to the position of the substrate corresponding to the stored identification code. Then, in the rotated position, a rotated image is obtained and a cross-sectional image can be created accordingly (P36). The defectiveness can be determined based on the cross-sectional image (P361). If it is not defective (NO), the appropriate rotational position for inspection of the other suspect objects may be determined (P35). On the other hand, if it is determined to be defective (YES), the identification code is stored again and it is finally determined that there is a defect.

In general, defects in the automated manufacturing process can be attributed to temporary operational errors or errors in the process itself. If data on persistent defect inspections accumulate, then the failure pattern can be analyzed (P37). It can be judged whether the defect is transient or due to errors in the process itself (P38). By such failure analysis and the process analysis, the effect of process improvement and productivity can be improved.

The inspection method according to the present invention can be applied in various ways, and the present invention is not limited to the embodiments shown.

The inspection method according to the present invention has an advantage that it is possible to perform thorough inspection of each bump formed on an electronic substrate and to inspect the entire bump formed in a required area. In addition, the method according to the present invention has the advantage that inspection of the bumps applied to a substrate bonding method such as a flip-chip is enabled.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention . The invention is not limited by these variations and modifications, but is limited only by the claims appended hereto.

11: X-ray tube 12: Detector
13: inspection stage 15: frame member

Claims (5)

In an electronic substrate inspection method,
Dividing the inspection area into a plurality of sub-inspection areas;
Irradiating the bumps formed in the sub-inspection region with an x-ray to obtain an image for each bump;
Determining a relative size of the acquired image; And
And judging whether or not there is a defect from the relative size. 2. The method of claim 1, wherein the step of determining the failure includes determining a suspect bump and obtaining at least one cross-section image for the suspect bump. The method according to claim 1, wherein the bumps are disposed on a memory chip or a flip chip. The method according to claim 2, wherein the at least one directional cross-sectional image is obtained by irradiating an x-ray in a direction different from the direction of irradiation for acquiring an image for each bump. The method according to claim 2, wherein the at least one directional cross-sectional image is obtained by rotating the suspected bump at a predetermined position.

Images