Back-drilling automatic optical inspection method

Abstract

A kind of back-drilling automatic optical detection method, its steps include: positioning, eccentricity inspection, depth inspection and inclination inspection, the present application utilizes laser optical module to be inspected to at least one drill-through hole on at least one plate body and the back-drilling of the back of the drill-through hole, its advantages are: can be completed without damaging the plate body under the condition of inspection, determine that secondary back-drilling processing can effectively remove unnecessary copper plating area on the surface of the drill-through hole, and inspection area is large, high efficiency.

Description

Technical Field

[0001] This invention relates to a method for detecting back-drilled holes in circuit boards, and more particularly to an automatic optical detection method for back-drilled holes with eccentricity, depth and tilt detection functions. Background Technology

[0002] Current circuit board manufacturing methods use the copper surface of the circuit board as a reference to uniformly set the drilling depth during back-drilling. They do not consider the impact of thickness differences or poor thickness uniformity between circuit boards on the machining accuracy of the back-drilling depth (stub length). Therefore, when there are significant thickness differences or poor thickness uniformity between circuit boards, the machining accuracy of the back-drilling depth will have a larger error range as the back-drilling depth increases, and may also result in eccentricity and tilting.

[0003] Existing back-drilled hole inspection methods are destructive testing methods that randomly sample and destroy circuit board slices to observe whether each back-drilled hole meets the requirements. However, destructive testing is time-consuming and can only be observed from a specific angle, which are the biggest drawbacks of existing inspection methods. Therefore, there is still a need for improvement. Summary of the Invention

[0004] This invention discloses an automatic optical inspection method for back-drilled holes, the steps of which include:

[0005] Positioning: At least one plate is fixed on a testing device. The plate includes at least one back drill hole with a predetermined depth. The testing device includes at least one laser optical module, at least one display, and a computing module. The laser optical module faces the back drill hole and displays the image through the display.

[0006] Eccentricity test: The laser optical module is focused on the surface of the board with the back drill hole. A first radius data is formed on the surface from the center of the back drill hole to the edge of the back drill hole, and a second radius data is formed from the center of the back drill hole to the edge of the first drill hole (including the thickness of the copper plating). The first radius data and the second radius data are transmitted to the computing module and an eccentricity calculation is performed. The eccentricity = first radius data / second radius data. When the eccentricity is equal to 1, the back drill hole passes the eccentricity test. When the eccentricity is less than 1, the back drill hole fails the eccentricity test.

[0007] Depth Test: A neck is formed between the back-drilled hole and the through-hole at a predetermined depth. The laser optical module sets its focal length based on the predetermined depth of the back-drilled hole. When the neck image is displayed on the screen, the predetermined depth of the back-drilled hole passes the depth test; when the neck image is not displayed on the screen, the predetermined depth of the back-drilled hole fails the depth test.

[0008] Tilt Inspection: A first positioning point is formed by using the laser optical module to detect the center position of the back drill hole on the surface of the board. Then, the laser optical module is focused on the neck, and a second positioning point is formed with the center position of the neck. The distance between the first positioning point and the second positioning point is calculated by the processing module to obtain a center offset value. Then, the tan... -1 (Center offset value / predetermined depth of back drill hole) yields a tilt angle. When the tilt angle value is less than a predetermined value, the back drill hole passes the tilt test. When the tilt angle is greater than a predetermined value, the back drill hole fails the tilt test.

[0009] Preferably, the board is a printed circuit board, which includes multiple copper-plated areas. The copper plating in each copper-plated area has a predetermined thickness. During each back-drilling process, the copper-plated area on the surface of the drilled hole is removed.

[0010] Preferably, the second radius data includes a predetermined thickness of copper plating at the edge of the drilled hole.

[0011] Preferably, the back drill hole is located on the other side of the plate.

[0012] The beneficial effects of the present invention include at least the following:

[0013] This invention enables inspection without damaging the board, confirming that secondary back drilling can effectively remove unnecessary copper plating areas on the surface of the drilled hole, and has a large inspection area and high efficiency. Attached Figure Description

[0014] Figure 1 This is a block diagram illustrating the steps of the present invention;

[0015] Figure 2 This is a top view of the eccentricity test of the present invention;

[0016] Figure 3 This is a schematic diagram of the eccentricity inspection of the through hole and back hole of the present invention;

[0017] Figure 4 This is a schematic diagram illustrating the pass and fail of the eccentricity test for this invention.

[0018] Figure 5 This is a top view of the depth inspection of the present invention;

[0019] Figure 6 This is a cross-sectional view of the plate body of the present invention;

[0020] Figure 7 This is a top view of the tilted inspection of the present invention;

[0021] Figure 8This is a schematic diagram of the inclined inspection of the through hole and back hole of the present invention;

[0022] Figure 9 This is a schematic diagram illustrating the tilt test of the present invention;

[0023] Figure 10 This is a schematic diagram illustrating the tilt test of the present invention;

[0024] Figure 10 The first is a schematic diagram of the present invention failing the tilt test.

[0025] Explanation of reference numerals in the attached figures

[0026] A Positioning

[0027] B. Eccentricity Test

[0028] C Depth Test

[0029] D. Tilt test

[0030] D1 Center Offset Value

[0031] D11 Tilt Angle Value

[0032] F focal length

[0033] 10 plate body

[0034] 11 Drilling through holes

[0035] 111 Second radius data

[0036] 12 Back-drilled holes

[0037] 12d Pre-depth

[0038] 121 Center

[0039] 122 First radius data

[0040] 123 First positioning point

[0041] 124 Second positioning point

[0042] 20. Neck. Detailed Implementation

[0043] Please see Figure 1 The automatic optical inspection method for back-drilled holes of the present invention includes the following steps: positioning A, eccentricity inspection B, depth inspection C, and tilt inspection D.

[0044] Please refer to Figure 1 , Figure 2 and Figure 6Positioning A: At least one plate 10 is fixed on a testing device (not shown in the figure). The plate 10 includes at least one through hole 11. The through hole 11 is further subjected to at least one back drilling process to enlarge one end of the through hole 11 to form a back drill hole 12. The back drill hole 12 has a predetermined depth 12d. The testing device includes at least one laser optical module (not shown in the figure), at least one display (not shown in the figure), and a computing module (not shown in the figure). The laser optical module faces and focuses on the back drill hole 12 and displays the images of the through hole 11 and the back drill hole 12 through the display.

[0045] The board 10 is a printed circuit board (PCB) and includes multiple copper-plated areas. The copper plating in each copper-plated area has a predetermined thickness. During the back drilling process, unnecessary copper-plated areas on the surface of the drilled hole 11 are removed.

[0046] Please refer to Figure 1 , Figure 3 and Figure 4 Eccentricity Test B: The laser optical module is focused on the surface of the plate 10 having the through hole 11 and the back drill hole 12 respectively. A first radius data 122 is formed from the center 121 of the back drill hole 12 to the edge of the back drill hole 12, and a second radius data 111 is formed from the center 121 of the back drill hole 12 to the edge of the through hole 11. The first radius data 122 and the second radius data 111 are transmitted to the computing module and an eccentricity ratio (shift ratio) calculation is performed. The shift ratio = first radius data / second radius data. When the shift ratio is equal to 1, the back drill hole 12 passes the eccentricity test B. When the shift ratio is less than 1, the back drill hole 12 fails the eccentricity test B.

[0047] The second radius number 111 includes the predetermined thickness of the copper plating on the edge of the drilled hole 11.

[0048] Please refer to Figure 1 , Figure 5 and Figure 6 Depth Test C: A neck 20 is formed between the back drill hole 12 and the through hole 11. The laser optical module sets its focal length F according to the predetermined depth 12d of the back drill hole 12. When the image of the neck 20 of the back drill hole 12 is displayed on the monitor, the predetermined depth 12d of the back drill hole 12 passes the depth test. Please refer to... Figure 5 When the image of the neck 20 of the back drill hole 12 is not displayed on the display (the back drill hole 12 is shown in the figure with a dashed line), the predetermined depth 12d of the back drill hole 12 fails the depth test. In other words, since the position of the focal length F cannot be correctly corresponded to the neck 20, an image cannot be formed.

[0049] Please refer to Figure 7 and Figure 8 Tilt inspection D: The laser optical module detects the center position of the back drill hole 12 to form a first positioning point 123. Then, the laser optical module focuses on the neck 20, and a second positioning point 124 is formed at the center position of the neck 20. The distance between the first positioning point 123 and the second positioning point 124 is calculated by the calculation module to obtain a center offset value D1. The calculation module then calculates the center offset value using the formula: tan -1 (Center offset value D1 / predetermined depth 12d of back drill hole 12) yields an inclination angle value D11. Please refer to... Figure 9 and Figure 10 When the tilt angle value D11 is less than a predetermined value, the back drill hole 12 passes the tilt test. Please refer to [reference needed]. Figure 10 First, if the tilt angle value D11 is greater than a predetermined value, then the back drill hole 12 fails the tilt test.

[0050] However, the above description is only a preferred embodiment of the present invention and should not be used to limit the scope of the present invention. All changes and modifications that can be obviously made by those skilled in the art should be considered as not departing from the essence of the present invention.

Claims

1. An automatic optical inspection method for back-drilled holes, characterized in that the steps include: include: Positioning: At least one plate is fixed on a testing device. The plate includes at least one through-hole. The through-hole is back-drilled at least once to form a back-drilled hole at one end. The back-drilled hole has a predetermined depth. The testing device includes at least one laser optical module, at least one display, and a computing module. The laser optical module faces and focuses on the back-drilled hole and displays the images of the through-hole and the back-drilled hole on the display. Eccentricity test: The laser optical module is focused on the surface of the board with the back drilled hole and the through hole respectively. A first radius data is formed from the center of the back drilled hole to its edge, and a second radius data is formed from the center of the back drilled hole to its edge, including the copper plating thickness. The first radius data and the second radius data are transmitted to the processing module and an eccentricity calculation is performed. When the eccentricity is equal to 1, the back drill hole passes the eccentricity test; when the eccentricity is less than 1, the back drill hole fails the eccentricity test. Depth Test: A neck is formed between the back-drilled hole and the through-hole. The laser optical module sets its focal length according to the predetermined depth of the back-drilled hole and focuses on the neck. When the image of the neck is displayed on the screen, the predetermined depth of the back-drilled hole passes the depth test; when the image of the neck is not displayed on the screen, the predetermined depth of the back-drilled hole fails the depth test. Tilt Inspection: The laser optical module detects the center position of the back drill hole to form a first positioning point. Then, the laser optical module focuses on the neck, forming a second positioning point with the center position of the neck. The processing module calculates the distance between the first and second positioning points to obtain a center offset value. Then, the processing module calculates tan... -1 A tilt angle value is obtained. When the tilt angle value is less than a predetermined value, the back drill hole passes the tilt test. When the tilt angle value is greater than a predetermined value, the back drill hole fails the tilt test.

2. The automatic optical inspection method for back-drilled holes according to claim 1, characterized in that, The board is a printed circuit board, which includes multiple copper-plated areas. The copper plating in each copper-plated area has a predetermined thickness. During back-drilling, the copper-plated areas on the surface of the drilled hole are removed.

3. The automatic optical inspection method for back-drilled holes according to claim 2, characterized in that, The second radius data includes the predetermined thickness of the copper plating at the edge of the drilled hole.

4. The automatic optical inspection method for back-drilled holes according to claim 1, characterized in that, The back drill hole is located on the other side of the plate.

Images