Flip-chip height measurement method and system

Abstract

This invention discloses a method and system for measuring flip-chip height. [Solution] The flip-chip height measurement method includes the steps of: providing a flip-chip structure, the flip-chip structure comprising a substrate, a chip, and a plurality of solder balls provided between the substrate and the chip; acquiring and measuring an image of the flip-chip structure, the steps of: acquiring a side image of the flip-chip structure by imaging the flip-chip structure, and measuring the vertical distance between the chip's side image or the vertical distance between the substrate and the chip based on the side image of the flip-chip structure; calculating the vertical distance within the flip-chip structure, the steps of: calculating the vertical distance between the substrate and the chip based on the vertical distance between the chip's side image or the vertical distance between the images; and calculating the total spatial volume, the steps of: calculating the total spatial volume between the substrate and the chip based on the vertical distance.

Description

Technical Field

[0001] The present invention relates to a measurement method and its system, and particularly to a flip chip height measurement method and its system.

Background Art

[0002] In the flip chip process, a chip is fixed on a substrate via a plurality of solder balls. At this time, there is a vertical distance between the substrate and the chip. Further, an underfill is filled between the chip and the substrate to increase the bonding strength between the chip and the substrate and to function as a thermal expansion buffer between the chip and the substrate.

[0003] When the filling amount of the underfill is excessive, the underfill may overflow and eventually cover the top surface of the chip. On the other hand, when the filling amount of the underfill is insufficient, the effect of improving the bonding strength between the chip and the substrate cannot be achieved. Therefore, in order to fill an appropriate amount of underfill, it is necessary to obtain the distance between the chip and the substrate, accurately obtain the total space volume between the chip and the substrate, and calculate the filling amount of the underfill.

[0004] However, as the chip structure becomes finer, even an error at the micrometer level has a great influence on the filling amount of the underfill.

[0005] Therefore, improving the measurement process and improving the accuracy of measuring the total space volume between the chip and the substrate to prevent defects caused by insufficient filling or overfilling of the underfill has become one of the important issues to be solved in the technical field.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technical problem that this invention aims to solve is to provide a flip-chip height measurement method and system that overcomes the shortcomings of the prior art. [Means for solving the problem]

[0007] To solve the above-mentioned technical problems, a flip-chip height measurement method is provided according to one aspect of the present invention. The flip-chip height measurement method includes the steps of: providing a flip-chip structure, wherein the flip-chip structure comprises a substrate, a chip, and a plurality of solder balls provided between the substrate and the chip; acquiring and measuring an image of the flip-chip structure, which includes acquiring a side image of the flip-chip structure by imaging the flip-chip structure, and acquiring the chip side image vertical distance of the chip or the image vertical distance between the substrate and the chip based on the side image of the flip-chip structure; calculating the vertical distance within the flip-chip structure, which includes calculating the vertical distance between the substrate and the chip based on the chip side image vertical distance or the image vertical distance; and calculating the total spatial volume, which includes calculating the total spatial volume between the substrate and the chip based on the vertical distance.

[0008] To solve the technical problems described above, another aspect of the present invention provides a flip-chip height measurement system. The flip-chip height measurement system comprises an image acquisition device, a measuring device, and a correction device. The image acquisition device acquires a side image of a flip-chip structure comprising a substrate, a chip, and a plurality of solder balls provided between the substrate and the chip by lateral imaging. The measuring device acquires the chip side image perpendicular distance or the image perpendicular distance between the substrate and the chip based on the side image of the flip-chip structure. The correction device calculates the vertical distance between the substrate and the chip based on the chip side image perpendicular distance or the image perpendicular distance, and calculates the total spatial volume between the substrate and the chip based on the vertical distance. [Effects of the Invention]

[0009] A beneficial effect of the present invention is that the flip-chip height measurement method according to the present invention employs lateral imaging to capture and acquire image distances related to the flip-chip structure via a lateral imaging unit, and compensates for errors due to the imaging angle using trigonometric calculations, thereby obtaining accurate vertical distances between the chip and the substrate and improving the accuracy of measuring the total spatial volume between the substrate and the chip. Consequently, the accuracy of the estimated underfill material amount is improved, and the product yield can be increased.

[0010] To provide a clearer understanding of the features and technical content of the present invention, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the accompanying drawings are for illustrative purposes only and do not limit the scope of the present invention. [Brief explanation of the drawing]

[0011] [Figure 1] This is a process flowchart of the flip-chip height measurement method according to the present invention. [Figure 2] This is a schematic side view of the flip-chip structure according to the present invention. [Figure 3] This is a schematic block diagram of the flip-chip height measurement system according to the present invention. [Figure 4] This is a schematic side view of a first embodiment of the flip-chip height measuring system according to the present invention. [Figure 5] This is a magnified view of a portion of Figure 4. [Figure 6] This is a schematic side view of a second embodiment of the flip-chip height measurement method according to the present invention. [Figure 7] This is a magnified section of Figure 6. [Modes for carrying out the invention]

[0012] The following describes embodiments of the flip-chip height measurement method and system according to the present invention using specific examples. Those skilled in the art will readily understand the advantages and effects of the present invention based on the disclosure herein. The present invention can be carried out or applied through other different specific embodiments, and the details described herein can be modified in various ways without departing from the spirit of the invention, depending on different viewpoints or applications. Furthermore, the accompanying drawings of the present invention are for illustrative purposes only and do not show actual dimensions. The following embodiments further describe the relevant technical content of the present invention, but the disclosed content is not intended to limit the scope of protection of the present invention. Also, the term "or" as used herein shall include any combination of one or more of the relevant enumerated items as necessary.

[0013] Figure 1 is a process flowchart of the flip-chip height measurement method according to the present invention. As shown in Figure 1, the first embodiment of the present invention provides a flip-chip height measurement method. The flip-chip height measurement method includes the steps of providing a flip-chip structure (step S1), acquiring and measuring an image of the flip-chip structure (step S2), calculating the vertical spacing distance within the flip-chip structure (step S3), and calculating the total spatial volume (step S4).

[0014] Figure 2 is a schematic side view of the flip-chip structure according to the present invention. As shown in Figure 2, the flip-chip structure F in step S1 comprises a substrate 1, a chip 2, and a plurality of solder balls 3. The substrate 1 has a top surface 10, and the chip 2 has a bottom surface 20, a top surface 21, and at least one side surface 22. The solder balls 3 are provided between the chip 2 and the substrate 1, and the substrate 1 and the chip 2 are separated by a predetermined distance. That is, the distance between the top surface 10 of the substrate 1 and the bottom surface 20 of the chip 2 is a vertical distance H.

[0015] In step S2, first, planar and cross-sectional images of the flip-chip structure F are captured, and then image measurement is performed based on the acquired planar and cross-sectional images. Here, regarding the side image, an image of the flip-chip structure F may be obtained by capturing the flip-chip structure F at a predetermined imaging angle. In this invention, the imaging angle is in the range of 0 degrees or more and less than 90 degrees. That is, a side image is obtained by imaging from the side.

[0016] In step S3, the image distance obtained by imaging the flip-chip structure F from the side has parallax with the actual distance, so image correction is performed to compensate for the parallax. In the image correction process, the vertical distance H between the top surface 10 of the substrate 1 and the bottom surface 20 of the chip 2 in the flip-chip structure F is obtained by correcting the image distance based on the imaging angle.

[0017] In step S4, after obtaining the vertical spacing distance H, the total spatial volume V between the substrate 1 and the chip 2 can be obtained by calculating the product of the vertical spacing distance H and the bottom area of ​​the chip 2.

[0018] Furthermore, in the flip-chip height measurement method according to the present invention, a step of calculating the estimated amount of underfill material to be filled may be performed using an external underfill material filling device. In this step, the estimated amount of underfill material to be filled is calculated based on the total space volume between the substrate and the chip and the total volume of the plurality of solder balls 3. For example, the total volume of the plurality of solder balls 3 is a known default value before processing the flip-chip. By subtracting the total volume of the plurality of solder balls 3 from the total space volume V, the estimated amount of underfill material to be filled can be obtained. This makes it possible to control the amount of underfill material to be filled in each flip-chip structure F, thereby improving the structural strength of the flip-chip structure F and reducing the deformation effect of the flip-chip structure F caused by differences in thermal expansion coefficients. Due to the influence of process operations, the estimated amount of underfill material to be filled can also be adjusted by other correction models, and the present invention is not limited thereto.

[0019] Next, FIG. 3 is a block schematic diagram of a flip chip height measurement system according to the present invention. As shown in FIGS. 2 and 3, the flip chip height measurement system 4 includes an image acquisition device 5, a measurement device 6, and a correction device 7. The image acquisition device 5 acquires a side image of the flip chip structure F by performing side imaging at a predetermined imaging angle. The measurement device 6 is connected to the image acquisition device 5, acquires a side image of the flip chip structure F from the image acquisition device 5, and finally performs a measurement operation based on the side image of the flip chip structure F to acquire an image distance in the side image of the flip chip structure F. The correction device 7 is connected to the measurement device 6, acquires an image distance in the side image of the flip chip structure F from the measurement device 6, and finally corrects the image distance based on the imaging angle to acquire a vertical interval distance H between the top surface 10 of the substrate 1 and the bottom surface 20 of the chip 2 in the flip chip structure F, and calculates a total space volume V between the substrate 1 and the chip 2. The correction device 7 may transmit the total space volume V to an external underfill material filling device (not shown). The external underfill material filling device acquires an estimated underfill material filling amount of the underfill material based on the total space volume V and the total volume of a plurality of solder balls 3. It should be noted here that data information on the total volume of the plurality of solder balls 3 may be stored in advance in the correction device 7 or the external underfill material filling device.

[0020] Refer to FIGS. 4 and 5. FIG. 4 is a side schematic diagram of a first embodiment of a flip chip height measurement system according to the present invention, and FIG. 5 is a partial enlarged view of FIG. 4. In the first embodiment, the image acquisition device 5 includes a first distance measurement unit 51, a second distance measurement unit 51', and a side imaging unit 52. The first distance measurement unit 51 images the top surface 10 of the substrate 1, the second distance measurement unit 51' images the top surface 21 of the chip 2, and the side imaging unit 52 images a side image of the flip chip structure F.

[0021] In the first embodiment, the measuring device 6 first obtains the vertical distance ΔD between the top surface 21 of the chip 2 and the top surface 10 of the substrate 1 (that is, the total thickness of the chip 2 and the plurality of solder balls 3) based on the images captured by the first distance measuring unit 51 and the second distance measuring unit 51'. Specifically, the measuring device 6 obtains a first measured distance D1 and a second measured distance D2 respectively based on the images captured by the first distance measuring unit 51 and the second distance measuring unit 51'. The first measured distance D1 is the vertical measured distance from the first distance measuring unit 51 to the top surface 10 of the substrate 1, and the second measured distance D2 is the vertical measured distance from the second distance measuring unit 51' to the top surface 21 of the chip 2. Since the first distance measuring unit 51 and the second distance measuring unit 51' are provided at the same height, the difference between the first measured distance D1 and the second measured distance D2 is the vertical distance ΔD between the top surface 21 of the chip 2 and the top surface 10 of the substrate 1 (that is, ΔD = D1 - D2).

[0022] In the first embodiment, two distance measuring units such as the first distance measuring unit 51 and the second distance measuring unit 51' are exemplified. However, in actual operation, in other embodiments, two distance measuring units or the same distance measuring unit may be selectively used for measurement, and the present invention is not limited thereto. In the first embodiment, each of the first distance measuring unit 51 and the second distance measuring unit 51' is configured as a stereo camera, but the present invention is not limited thereto. In other embodiments, a device for directly measuring distance may be used, and it is not necessary to measure the distance on the image after obtaining the image.

[0023] In the first embodiment, the side imaging unit 52 captures the side surface 22 of the flip chip structure F at a predetermined imaging angle θ and obtains the vertical distance A1 of the chip side surface image on the image of the chip 2. Since the side imaging unit 52 employs side imaging, the vertical distance A1 of the chip side surface image does not correspond to the actual vertical distance D3 of the side surface of the chip 2 (also called the thickness of the chip 2). Therefore, the correction device 7 corrects the vertical distance A1 of the chip side surface image based on the imaging angle θ and obtains the vertical distance D3 of the side surface.

[0024] As shown in Figure 5, the lateral imaging unit 52 forms two virtual imaging lines (shown as dashed lines in Figure 5) that extend toward the lateral imaging unit 52 at an imaging angle θ from the intersection of the bottom surface 20 and top surface 21 of the chip 2 and one of its side surfaces in the imaging field of view (shown as dashed lines in Figure 5). The chip lateral image vertical distance A1 is the vertical distance between the two virtual imaging lines. In the first embodiment, the lateral vertical distance D3 is obtained by correcting the chip lateral image vertical distance A1 based on the geometric concepts of alternate interior angle and supplementary angle. Specifically, the chip lateral image vertical distance A1 is calculated as the reciprocal of the cosine of the imaging angle θ, and the lateral vertical distance D3 is calculated (i.e., D3 = A1 × 1 / cosθ).

[0025] As shown in Figure 4, after obtaining the lateral vertical distance D3, the vertical spacing distance H (i.e., H = ΔD - D3) is obtained by subtracting the lateral vertical distance D3 from the top surface distance ΔD.

[0026] After obtaining the vertical distance H, the total spatial volume V between the substrate 1 and the chip 2 can be accurately calculated. Furthermore, the external underfill material filling device calculates the estimated amount of underfill material to be filled based on the total volume of multiple solder balls 3. Finally, an appropriate amount of underfill material is filled between the chip 2 and the substrate 1.

[0027] Refer to Figures 6 and 7. Figure 6 is a schematic side view of a second embodiment of the flip-chip height measurement system according to the present invention, and Figure 7 is a partially enlarged view of Figure 6. Refer also to Figures 1 to 5. In the second embodiment, the flip-chip height measurement system is generally the same as in the first embodiment, except that the image acquisition device 5 further comprises a positioning unit 53. The positioning unit 53 is configured to define a reference point R projected onto the substrate 1 along the side surface 22 of the chip 2. The lateral imaging unit 52 is configured to perform imaging at an imaging angle θ and acquire the image vertical spacing distance A2 of the reference point R with respect to the bottom surface B of the chip 2. Since the lateral imaging unit 52 employs lateral imaging, the acquired image vertical spacing distance A2 does not correspond to the actual vertical spacing distance H. Therefore, the correction device 7 corrects the image vertical spacing distance A2 based on the imaging angle θ and acquires the vertical spacing distance H.

[0028] In the second embodiment, a positioning unit 53 (e.g., a directional light source) is used to generate a linear light beam vertically above the flip-chip structure F. The linear light beam is projected along the side surface 22 of the chip 2 onto the top surface 10 of the substrate 1 to form a reference point R.

[0029] When the positioning unit 53 is a directional light source, the positioning unit 53 may be a laser light emitter or an LED emitter, but the present invention is not limited thereto. Any device that can project light along the side surface 22 of the chip 2 onto the top surface 10 of the substrate 1 to form a reference point R can be used as the positioning unit 53.

[0030] In Figures 6 and 7, due to the field of view, the base B is shown as a single point, but in reality, it extends along the normal vector of the paper. Within the field of view of the lateral imaging unit 52, the base B of the chip 2 is located at the intersection of the bottom surface 20 and the side surface 22 (the boundary between the bottom surface 20 and the side surface 22), so the base B of the chip 2 is clearly visible. The reference point R is formed by projection by the directional light source, so the position of the reference point R is also clearly visible. Furthermore, since the directional light source is projected perpendicularly along the side surface 22 of the chip 2 to form the reference point R, it is guaranteed that the reference point R and the side surface 22 of the chip 2 are on the same plane. Therefore, the image vertical spacing distance A2 can be obtained by measuring the vertical distance between the base B and the reference point R in the lateral image of the chip 2.

[0031] As shown in Figure 7, the lateral imaging unit 52 forms two virtual imaging lines (shown as dashed lines in Figure 7) that extend toward the lateral imaging unit 52 at an imaging angle θ from a reference point R and a reference point R perpendicular to the base B of the chip 2 within the imaging field of view (shown as dashed lines in Figure 7). The image vertical spacing distance A2 is the vertical distance between the two virtual imaging lines. In the second embodiment, the vertical spacing distance H is obtained by correcting the image vertical spacing distance A2 based on the geometric concepts of internal alternate angles and complementary angles. Specifically, the image vertical spacing distance A2 is calculated as the reciprocal of the cosine of the imaging angle θ to obtain the vertical spacing distance H (i.e., H = A2 × 1 / cosθ).

[0032] After obtaining the vertical spacing distance H, this is equivalent to obtaining the height of the solder balls 3. This allows the correction device 7 to accurately calculate the total spatial volume V between the substrate 1 and the chip 2. Furthermore, the external underfill material filling device calculates the estimated amount of underfill material to be filled based on the total spatial volume V and the total volume of the multiple solder balls 3. Finally, an appropriate amount of underfill material is filled between the chip 2 and the substrate 1.

[0033] However, the embodiments described above are merely feasible examples and do not limit the present invention. [Beneficial effects of the examples]

[0034] A beneficial effect of the present invention is that the flip-chip height measurement method according to the present invention employs lateral imaging to capture and acquire image distances related to the flip-chip structure via a lateral imaging unit, and compensates for errors due to the imaging angle using trigonometric calculations, thereby obtaining accurate vertical distances between the chip and the substrate and improving the accuracy of measuring the total spatial volume between the substrate and the chip. Consequently, the accuracy of the estimated underfill material amount is improved, and the product yield can be increased.

[0035] The information disclosed herein represents only preferred and feasible embodiments of the present invention and does not limit the scope of protection of the present invention. Accordingly, all equivalent technical modifications made based on the description and drawings of the present invention are all included within the scope of protection of the present invention. [Explanation of Symbols]

[0036] 1: Circuit board 10:Top surface 2: Tip 20: Bottom 21:Top surface 22: Side view 3: Solder ball 4: Flip-chip height measurement system 5: Image acquisition device 51: First distance measuring unit 51': Second range measuring unit 52: Lateral imaging unit 53: Positioning Unit 6: Measuring device 7: Correction device F: Flip-chip structure A1: Vertical distance of the chip side view A2: Image vertical spacing distance B: Bottom D1: First measurement distance D2: Second measurement distance D3: Side vertical distance ΔD: Distance between top surfaces H: Vertical spacing distance θ: imaging angle S1~S4: Step

Claims

1. A step of providing a flip-chip structure, wherein the flip-chip structure comprises a substrate, a chip, and a plurality of solder balls provided between the substrate and the chip, A step of acquiring and measuring an image of a flip-chip structure, comprising: acquiring a side image of the flip-chip structure by imaging the flip-chip structure; and measuring and acquiring the vertical distance of the chip's side image or the vertical distance between the substrate and the chip based on the side image of the flip-chip structure. A step of calculating the vertical spacing distance within the flip-chip structure, comprising the step of calculating the vertical spacing distance between the substrate and the chip based on the vertical distance of the chip side image or the vertical spacing distance of the image, A step of calculating the total spatial volume, comprising the step of calculating the total spatial volume between the substrate and the chip based on the vertical spacing distance, A flip-chip height measurement method characterized by including the following:

2. In the process of acquiring and measuring flip-chip structure images, a side view image of the flip-chip structure is acquired by taking a side view image at a predetermined imaging angle. In the step of calculating the vertical spacing distance within the flip-chip structure, the vertical distance of the chip side image or the vertical spacing distance of the image is corrected based on the imaging angle, and the vertical spacing distance is obtained. The flip-chip height measurement method according to feature 1.

3. The vertical distance of the chip side image is calculated by taking the reciprocal of the cosine of the imaging angle to determine the vertical distance, or the vertical spacing distance is calculated by taking the reciprocal of the cosine of the imaging angle to determine the vertical spacing distance. The flip-chip height measurement method according to feature 2.

4. The process of acquiring and measuring flip-chip structural images further includes acquiring the distance between the top surface of the chip and the top surface of the substrate, In the step of calculating the vertical spacing distance within the flip-chip structure, the vertical spacing distance is calculated based on the difference between the vertical distance of the side surface and the distance between the top surfaces. The flip-chip height measurement method according to feature 3.

5. In the process of acquiring and measuring flip-chip structural images, a reference point is defined by projecting it onto the substrate along the side of the chip, a lateral image is taken at a predetermined imaging angle, and the vertical distance between the image of the reference point and the bottom edge of the chip is acquired. The bottom edge of the chip is the boundary between the bottom surface and the side surface of the chip. The flip-chip height measurement method according to feature 1.

6. A step of calculating the estimated amount of underfill material to be filled, further comprising the step of calculating the estimated amount of underfill material to be filled based on the total volume of the space and the total volume of the plurality of solder balls, The total space volume between the substrate and the chip is obtained by multiplying the vertical spacing distance and the bottom surface area of ​​the chip, and the estimated amount of underfill material is obtained by subtracting the total volume of the multiple solder balls from the total space volume. The flip-chip height measurement method according to feature 5.

7. An image acquisition device that acquires a side view of a flip-chip structure comprising a substrate, a chip, and a plurality of solder balls provided between the substrate and the chip by lateral imaging, A measuring device that acquires the vertical distance of the chip's side image, or the vertical distance between the substrate and the chip, based on a side image of the flip-chip structure, A correction device that calculates the vertical distance between the substrate and the chip based on the vertical distance of the chip side image or the vertical distance of the image, and calculates the total spatial volume based on the vertical distance, A flip-chip height measuring system characterized by having the following features.

8. The image acquisition device includes a side imaging unit that acquires a side image of the flip-chip structure of the chip by imaging it from the side at a predetermined imaging angle. The correction device corrects the vertical distance of the chip side image or the vertical spacing distance of the images based on the imaging angle, and obtains the vertical spacing distance. The flip-chip height measuring system according to feature 7.

9. The correction device calculates the vertical distance of the chip side image by the reciprocal of the cosine of the imaging angle, or calculates the vertical spacing distance by the reciprocal of the cosine of the imaging angle. The flip-chip height measuring system according to feature 8.

10. The image acquisition device further comprises at least one distance measuring unit used to acquire the top surface distance between the top surface of the chip and the top surface of the substrate, The correction device calculates the vertical spacing distance based on the difference between the vertical distance of the side and the distance between the top surfaces. The flip-chip height measuring system according to feature 9.

11. The image acquisition device is A positioning unit configured to define a reference point projected onto the substrate along the side surface of the chip, The system includes a lateral imaging unit configured to perform lateral imaging at a predetermined imaging angle and to acquire the vertical distance between the image and the reference point relative to the bottom edge of the chip, The bottom edge of the chip is the boundary between the bottom surface and the side surface of the chip. The flip-chip height measuring system according to feature 7.

12. The correction device provides the total space volume to the external underfill material filling device, and the external underfill material filling device is configured to calculate the estimated amount of underfill material to be filled based on the total space volume and the total volume of the plurality of solder balls. The external underfill material filling apparatus obtains the total space volume between the substrate and the chip by multiplying the vertical spacing distance and the bottom surface area of ​​the chip, and obtains the estimated amount of underfill material to be filled by subtracting the total volume of the plurality of solder balls from the total space volume. The flip-chip height measuring system according to feature 11.

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