Printed board back drilling depth correction method

Abstract

The invention provides a printed board back drilling depth correction method. The printed board back drilling depth correction method comprises the steps that the actual thickness value of a printed board at each back drilling hole position is measured; judging whether the actual thickness value of the printed board at each back drilling hole position exceeds a standard upper limit value or a standard lower limit value, and if yes, correcting the actual thickness value of the printed board to obtain a corrected thickness value of the printed board; if the standard upper limit value or the standard lower limit value is not exceeded, the actual thickness value of the printed board is reserved; according to the corrected thickness value of the printed board at each back drilling hole position or the proportional relation between the actual thickness value of the printed board and the theoretical thickness value of the printed board, the actual drilling depth at each back drilling hole position is calculated; and back drilling is conducted according to the actual drilling depth. According to the method, the actual thickness of the printed board exceeding the standard upper limit value or the standard lower limit value is corrected, the correction value is used as the actual thickness value of the printed board, the accuracy of board thickness data is ensured, and then the precision of the back drilling depth is improved.

Description

Technical Field

[0001] The invention relates to the technical field of back-drilling production, and in particular to a method for correcting the back-drilling depth of a printed circuit board. Background Art

[0002] With the widespread application of electronic products in high-speed signal transmission, the requirements for the precision of the back-drilled pile size are getting higher and higher. With the increase of the thickness and format size of the printed circuit board, the thickness uniformity of the printed circuit board fluctuates more and more. Accurately obtaining the thickness of the printed circuit board to reversely infer the back-drilling depth is the prerequisite for achieving precise depth control processing.

[0003] At present, the main depth control method is to use a resistive or capacitive sensing system to form a capacitive system or a resistive loop with the drill bit, printed circuit board, and machine tool table. When the drill bit contacts the surface aluminum cover plate, the sensing system is triggered to record the grating scale data, thereby obtaining height data and controlling the processing depth. However, in the actual back drilling process, the detection height data is often inaccurate due to the cover plate on the surface of the printed circuit board or the presence of foreign matter on the surface of the printed circuit board, aluminum chips or copper chips wrapped around the drill bit, etc., which makes the actual thickness measurement of the printed circuit board have errors, causing the back drilling depth to be calculated too large or too small, resulting in deep or shallow drilling quality problems.

[0004] The technical scheme of CNCN105050326B discloses a method for measuring the thickness of a printed circuit board: Step 2: Place the PCB on a table, measure the height of each back-drilled hole except the back-drilled surface, and obtain data H1; Step 3: Remove the PCB, measure the height of the back-drilled hole in step 2 corresponding to the position of the pad, and obtain data H2; Step 4: Turn the pad over and place it on the table, measure the height of each back-drilled hole on the back-drilled surface corresponding to the position of the pad, and obtain data H4; Step 5: Turn the PCB over and place it on the pad, measure the height of the back-drilled surface corresponding to the back-drilled hole in the above step 4, and obtain data H3; Step 6: Calculate the data through the back-drilling machine to calculate the actual board thickness Hn=Min[(H2-H1),(H4-H3)]. In this technical scheme, it is necessary to measure the data height four times to obtain the actual board thickness of the printed circuit board, and there are multiple printed circuit boards and pads arranged in different orders during the measurement process, resulting in a cumbersome and complicated measurement process, and a cumbersome and complicated calculation process, which is not conducive to improving the execution efficiency of the back-drilling program. At the same time, in the process of multiple measurements and calculations in this technical solution, if there is an error in one of the links, it will cause a deviation in the actual thickness of the plate, and then cause a deviation in the back drilling depth. There is no effective detection method to avoid the occurrence of such deviations, which will also affect the accuracy of the final back drilling depth. Summary of the invention

[0005] In order to overcome the problems existing in the related art, the purpose of the present invention is to provide a method for correcting the back drilling depth of a printed circuit board, which corrects the actual thickness of a printed circuit board that exceeds a standard upper limit or a standard lower limit, and uses the correction value as the actual thickness value of the printed circuit board to ensure the accuracy of the board thickness data, thereby improving the accuracy and acquisition efficiency of the back drilling depth.

[0006] A method for correcting back drilling depth of a printed circuit board, comprising:

[0007] S1: Measure the actual thickness of the printed circuit board at each back-drilling hole position;

[0008] S2: judging whether the actual thickness value of the printed board at each back-drilling hole position exceeds the standard upper limit value or the standard lower limit value, if it exceeds the standard upper limit value or the standard lower limit value, correcting the actual thickness value of the printed board to obtain the corrected thickness value of the printed board; if it does not exceed the standard upper limit value or the standard lower limit value, retaining the actual thickness value of the printed board;

[0009] S3: Calculate the actual drilling depth at each back drilling hole position according to the corrected thickness value of the printed board at each back drilling hole position or the proportional relationship between the actual thickness value of the printed board and the theoretical thickness value of the printed board;

[0010] S4: Back-drill according to the actual drilling depth.

[0011] Furthermore, the method for measuring the actual thickness value of the printed circuit board at each back-drilled hole position in step S1 includes:

[0012] Place a backing plate and a first aluminum sheet on the drilling machine table in sequence, perform a first back drilling procedure in the first aluminum sheet to obtain a first back drilled hole, and measure a distance H1 between the bottom of the first back drilled hole and the drilling machine table;

[0013] A backing plate, a printed circuit board, and a second aluminum sheet are sequentially placed on the drilling machine table, a second back drilling procedure is performed in the second aluminum sheet to obtain a second back drilling hole, and a distance H2 between the bottom of the second back drilling hole and the drilling machine table is measured; wherein the first aluminum sheet and the second aluminum sheet have the same material and thickness; and the first back drilling procedure and the second back drilling procedure are the same;

[0014] The actual thickness value of the printed circuit board at each back drilling hole position is T = |H1-H2|.

[0015] Furthermore, the method for obtaining the standard upper limit value and the standard lower limit value includes: measuring the actual thickness at various positions in the printed circuit board, wherein the maximum measured value and the minimum measured value are the standard upper limit value and the standard lower limit value;

[0016] Alternatively, the method for obtaining the standard upper limit value and the standard lower limit value includes: calculating the standard upper limit value and the standard lower limit value of the printed circuit board according to the theoretical stacking structure of the printed circuit board.

[0017] Furthermore, the actual thickness at each position in the printed circuit board is measured by a contact type board thickness detection device or an optical non-contact board thickness detection device.

[0018] Furthermore, in step S2, the actual thickness value of the printed circuit board is corrected, specifically including:

[0019] The printed circuit board is divided into regions, and for the actual thickness value of the printed circuit board in each region that exceeds the standard upper limit value or the standard lower limit value, the average value of the actual thickness values ​​of the printed circuit boards in the region that do not exceed the standard upper limit value or the standard lower limit value is calculated as the corrected thickness value of the printed circuit board at the corresponding back drilling position; M is an integer greater than 1.

[0020] Furthermore, the area division of the printed circuit board includes: dividing the printed circuit board into a central area and X edge areas, the central area is located at the center of the printed circuit board, and the edge areas surround the central area and are located at the edge of the printed circuit board.

[0021] Furthermore, the printed circuit board is a rectangular parallelepiped, the number of the edge regions is four, and the four edge regions correspond to the four sides of the printed circuit board and are respectively located outside the central region, and the width of the edge regions is 25-35 mm.

[0022] Furthermore, the said dividing the printed circuit board into regions includes: dividing the Y regions in the printed circuit board in a matrix arrangement.

[0023] Furthermore, in step S3, the actual drilling depth at each back-drilling position is calculated, which specifically includes:

[0024] Actual drilling depth = (T 实际 / T 理论 )×D 理论 +K; when the actual thickness of the printed board does not exceed the upper or lower limit of the standard, T 实际 is the actual thickness of the printed board; when the actual thickness of the printed board exceeds the standard upper limit or standard lower limit, T 实际 is the corrected thickness value of the printed circuit board; K is the compensation value.

[0025] Further, when the back drilling procedure is performed, when an aluminum sheet is placed on the printed circuit board, K = thickness of the aluminum sheet + [(drill radius) / tan(drill point angle*0.5)];

[0026] When the back drilling procedure is performed and no aluminum sheet is placed on the printed circuit board, K = [(drill radius) / tan(drill point angle*0.5)].

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides a method for correcting the back-drilling depth of a printed circuit board, comprising: measuring the actual thickness value of the printed circuit board at each back-drilling hole position; judging whether the actual thickness value of the printed circuit board at each back-drilling hole position exceeds the standard upper limit value or the standard lower limit value, if it exceeds the standard upper limit value or the standard lower limit value, correcting the actual thickness value of the printed circuit board to obtain the corrected thickness value of the printed circuit board; if it does not exceed the standard upper limit value or the standard lower limit value, retaining the actual thickness value of the printed circuit board; calculating the actual drilling depth at each back-drilling hole position according to the proportional relationship between the corrected thickness value of the printed circuit board at each back-drilling hole position or the actual thickness value of the printed circuit board and the theoretical thickness value of the printed circuit board; back-drilling according to the actual drilling depth. The present application corrects the actual thickness of the printed circuit board that exceeds the standard upper limit value or the standard lower limit value, and uses the correction value as the actual thickness value of the printed circuit board to ensure the accuracy of the board thickness data, thereby improving the accuracy and acquisition efficiency of the back-drilling depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the process flow of the printed circuit board back drilling depth correction method of the present application;

[0030] Figure 2 This is a schematic diagram of the area division in Example 3;

[0031] Figure 3 This is a schematic diagram of the area division in Example 4.

[0032] Reference numerals:

[0033] S0, center area; S1, upper edge area; S2, left edge area; S3, lower edge area; S4, right edge area. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0035] Example 1

[0036] like Figure 1 As shown, the present application provides a printed circuit board back drilling depth correction method, comprising:

[0037] S1: Measure the actual thickness of the printed circuit board at each back-drilling hole position;

[0038] S2: Determine whether the actual thickness value of the printed board at each back-drilling hole position exceeds the standard upper limit value or the standard lower limit value. If it exceeds the standard upper limit value or the standard lower limit value, correct the actual thickness value of the printed board to obtain the corrected thickness value of the printed board; if it does not exceed the standard upper limit value or the standard lower limit value, retain the actual thickness value of the printed board.

[0039] During the measurement process, the actual thickness of the printed board is often inaccurately measured due to the cover plate on the surface of the printed board or the presence of foreign matter on the surface of the printed board, aluminum or copper chips wrapped around the drill bit, etc., which results in errors in the actual thickness measurement of the printed board, causing the back drilling depth to be calculated too large or too small, resulting in quality problems such as deep drilling or shallow drilling. The purpose of this step is to calibrate the actual thickness value of the printed board in step S1. If the actual thickness value of the printed board exceeds the upper limit of the standard brick or the lower limit of the standard, it means that there is an error in its measurement. At this time, the actual thickness value of the printed board needs to be corrected, which can reduce or avoid errors or inaccurate measurements in step S1. Only by correcting the accurate actual thickness value of the printed board can the accuracy of the subsequent calculation of the actual drilling depth be ensured.

[0040] S3: Calculate the actual drilling depth at each back drilling hole position according to the corrected thickness value of the printed board at each back drilling hole position or the proportional relationship between the actual thickness value of the printed board and the theoretical thickness value of the printed board;

[0041] When the actual thickness value of the printed board is not corrected, the actual drilling depth at the back drilling position is calculated based on the proportional relationship between the actual thickness value of the printed board at the back drilling position and the theoretical thickness value of the printed board. When the actual thickness value of the printed board is corrected, the actual drilling depth at the back drilling position is calculated based on the proportional relationship between the corrected thickness value of the printed board at the back drilling position and the theoretical thickness value of the printed board.

[0042] S4: Back-drill according to the actual drilling depth.

[0043] This application corrects the actual thickness of the printed circuit board that exceeds the standard upper limit or standard lower limit, and uses the correction value as the actual thickness value of the printed circuit board to ensure the accuracy of the board thickness data, thereby improving the accuracy and acquisition efficiency of the back drilling depth.

[0044] Example 2

[0045] like Figure 1 As shown, the present application provides a printed circuit board back drilling depth correction method, comprising:

[0046] S1: Measure the actual thickness of the printed circuit board at each back-drilling hole position; specifically include:

[0047] S11: placing a pad and a first aluminum sheet on a drilling table in sequence, executing a first back-drilling procedure in the first aluminum sheet to obtain a first back-drilled hole, and measuring a distance H1 between the bottom of the first back-drilled hole and the drilling table.

[0048] S12 places a pad, a printed circuit board, and a second aluminum sheet on the drilling rig table in sequence, executes a second back drilling procedure in the second aluminum sheet to obtain a second back drilling hole, and measures a distance H2 between the bottom of the second back drilling hole and the drilling rig table; wherein the material and thickness of the first aluminum sheet and the second aluminum sheet are the same; and the first back drilling procedure and the second back drilling procedure are the same.

[0049] The first back drilling program and the second back drilling program here both refer to the back drilling program when back drilling the printed board to be processed. For the convenience of description, they are distinguished in the naming. Since it is necessary to measure the actual thickness of the printed board at each back drilling hole position in the printed board to be processed, when the first back drilling program and the second back drilling program are executed, it is necessary to drill holes at the corresponding positions to obtain the actual thickness value of the printed board at the position.

[0050] It should be noted that there are multiple back-drilling positions on the printed circuit board to be processed, and the present application needs to measure the actual thickness value of the printed circuit board for each back-drilling position.

[0051] S13 The actual thickness value of the printed circuit board at each back-drilling hole position T = |H1-H2|.

[0052] In this step, the thickness of the first aluminum sheet and the second aluminum sheet are the same, and during the execution of the first back-drilling procedure and the second back-drilling procedure, the first aluminum sheet and the second aluminum sheet will not be drilled through. In this way, the distance H2 between the bottom of the second back-drilling hole and the drilling machine table is equal to the thickness of the printed circuit board to be processed plus the distance H1 between the bottom of the first back-drilling hole and the drilling machine table. The actual thickness value of the printed circuit board at the same back-drilling hole position can be calculated by the height difference between the two distances. Among them, the distance H1 between the bottom of the first back-drilling hole and the drilling machine table and the distance H2 between the bottom of the second back-drilling hole and the drilling machine table can be specifically measured by the principle of capacitive height detection or the principle of resistive height detection.

[0053] The principle of capacitive height detection is as follows: the drill tip, printed circuit board, drilling rig table, and spindle form a capacitive circuit. The printed circuit board surface and the drilling rig table form a variable capacitor. When the drill tip contacts the first aluminum sheet or the second aluminum sheet on the printed circuit board, the initial capacitance signal is triggered. After a series of signal amplification and denoising processing, it is transmitted to the CNC system and the grating ruler reading at this time is recorded to obtain the initial height. As the spindle moves downward, the grating ruler reading is continuously recorded to achieve back drilling processing at a specified depth, and then the distance between the bottom of the back-drilled hole and the drilling rig table is calculated.

[0054] The principle of resistive height detection is as follows: the drill tip, printed circuit board, drilling rig table, and spindle form a resistive circuit. When the drill tip contacts the first aluminum sheet or the second aluminum sheet on the printed circuit board, a signal is triggered. After a series of signal amplification and denoising processes, the signal is transmitted to the CNC system and the grating scale reading at this time is recorded to obtain the initial height. As the spindle moves downward, the grating scale reading changes, thereby realizing back drilling processing at a specified depth, and then calculating the distance between the bottom of the back-drilled hole and the drilling rig table.

[0055] S2: Determine whether the actual thickness value of the printed board at each back-drilling hole position exceeds the standard upper limit value or the standard lower limit value. If it exceeds the standard upper limit value or the standard lower limit value, correct the actual thickness value of the printed board to obtain the corrected thickness value of the printed board; if it does not exceed the standard upper limit value or the standard lower limit value, retain the actual thickness value of the printed board.

[0056] Specifically, the method for correcting the actual thickness value of the printed circuit board includes:

[0057] The printed circuit board is divided into regions, and for the actual thickness values ​​of the printed circuit boards in each region that exceed the standard upper limit value or the standard lower limit value, the average value of the actual thickness values ​​of the printed circuit boards in the region that do not exceed the standard upper limit value or the standard lower limit value is calculated as the corrected thickness value of the printed circuit board at the corresponding back-drilled hole position; M is an integer greater than 1, and the number of M does not exceed the number of normal actual thickness values ​​of the printed circuit boards in the region. The normal actual thickness value of the printed circuit board refers to the actual thickness value of the printed circuit board that does not exceed the standard upper limit value or the standard lower limit value. For example, in the same region, there are 10 back-drilled holes, of which the actual thickness values ​​of the printed circuit boards corresponding to the positions of 8 back-drilled holes do not exceed the standard upper limit value or the standard lower limit value, and the actual thickness values ​​of the printed circuit boards corresponding to the positions of 2 back-drilled holes exceed the standard upper limit value or the standard lower limit value, then the actual thickness values ​​of these 2 printed circuit boards need to be corrected. When making the correction, at least two of the 8 normal actual thickness values ​​of the printed circuit boards can be searched for an average value, and the average value can be used as the corrected thickness value of the printed circuit board at the back-drilled hole position.

[0058] When executing the first back-drilling program or the second back-drilling program, the first back-drilling program or the second back-drilling program includes a positioning program, and the positioning program records the coordinates of each back-drilling hole. The coordinates of the positioning holes in the printed circuit board can be matched with the coordinates of the drilling machine table, thereby achieving the matching and conversion of the coordinate system, and accurately positioning the coordinate position of each back-drilling hole. When performing regional division, regional division can also be performed with the help of the coordinate system.

[0059] Specifically, the method for obtaining the standard upper limit value and the standard lower limit value in this step may include the following two methods:

[0060] The first acquisition method: measure the actual thickness at various positions in the printed circuit board, where the maximum and minimum measured values ​​are the standard upper and lower limits. Specifically, the actual thickness at various positions in the printed circuit board can be measured by a contact-type board thickness detection device or an optical non-contact board thickness detection device. Here, the actual thickness at various positions of the printed circuit board is measured, not only at the back-drilled hole location, but also at various positions outside the back-drilled hole.

[0061] The second acquisition method: Calculate the standard upper limit and standard lower limit of the printed board according to the theoretical stacking structure of the printed board. That is to say, the standard upper limit and standard lower limit can be determined according to the design theoretical value of the printed board. During the design and production process of the printed board, it is formed by laminating multiple layers. During the lamination process, the material and thickness of each layer are determined. Therefore, according to its theoretical design value, combined with the empirical value, the standard upper limit and standard lower limit of the printed board can be obtained.

[0062] The above-mentioned division of the printed circuit board into regions includes the following two division methods:

[0063] The first area division method: the printed circuit board is divided into a central area and X edge areas, the central area is located at the center of the printed circuit board, and the edge areas surround the central area and are located at the edge of the printed circuit board. For example, when the printed circuit board is a rectangular parallelepiped, there are four edge areas, and the four edge areas correspond to the four sides of the printed circuit board and are respectively located outside the central area. The width of the edge area is 25-35 mm.

[0064] According to the lamination rules of printed circuit boards, after the lamination process, the edge areas of the printed circuit boards will be distributed with glue grooves, so that the edge areas and the central areas have a more obvious difference in thickness. Therefore, the edge areas with glue grooves are divided into X areas according to the orientation or other positional relationships, and the central area without glue grooves is divided as a separate area. This can ensure the uniformity of the thickness of each area and ensure that the correction result is more accurate.

[0065] The second area division method: divide the Y areas in the printed circuit board in a matrix arrangement. For example, when the printed circuit board is a rectangular parallelepiped, it can be divided into areas of A rows and B columns in a matrix manner. The larger the values ​​of A and B, the more areas are divided, and the actual thickness correction for the area will be more accurate, but it also increases the difficulty of division. Therefore, in actual operation, the printed circuit board can be appropriately divided according to its size information to ensure that the thickness in the same area is uniform and consistent, so as to ensure the uniformity of the thickness of each area and ensure that the correction result is more accurate.

[0066] S3: Calculate the actual drilling depth at each back drilling position according to the corrected thickness value of the printed board at each back drilling position or the proportional relationship between the actual thickness value of the printed board and the theoretical thickness value of the printed board. Specifically, when the actual thickness value of the printed board has not been corrected, the actual drilling depth at the back drilling position is calculated according to the proportional relationship between the actual thickness value of the printed board at the back drilling position and the theoretical thickness value of the printed board. When the actual thickness value of the printed board is corrected, the actual drilling depth at the back drilling position is calculated according to the proportional relationship between the corrected thickness value of the printed board at the back drilling position and the theoretical thickness value of the printed board.

[0067] Calculate the actual drilling depth at each back-drilling location, including:

[0068] Actual drilling depth = (T 实际 / T 理论 )×D 理论 +K; when the actual thickness of the printed board does not exceed the upper or lower limit of the standard, T 实际 is the actual thickness of the printed board; when the actual thickness of the printed board exceeds the standard upper limit or standard lower limit, T 实际 is the corrected thickness value of the printed circuit board; K is the compensation value.

[0069] When performing the back drilling procedure, when an aluminum sheet is placed on the printed circuit board, K = aluminum sheet thickness + [(drill radius) / tan(drill point angle*0.5)];

[0070] When the back drilling procedure is performed and no aluminum sheet is placed on the printed circuit board, K = [(drill radius) / tan(drill point angle*0.5)].

[0071] The actual drilling depth in this step refers to the depth of the hole that the drill needs to drill when executing the back drilling program. In order to protect the surface of the printed circuit board, it is usually necessary to cover the surface of the printed circuit board with an aluminum sheet when drilling. At this time, the compensation value needs to include the thickness of the aluminum sheet. If the hole is drilled directly without covering the aluminum sheet, the thickness of the aluminum sheet does not need to be included in the compensation value.

[0072] At the same time, since the drill bit has a conical structure, the bottom of the back-drilled hole refers to the bottommost position that the drill bit can reach during the drilling process, and (T 实际 / T 理论 )×D 理论 The calculated theoretical depth refers to the theoretical depth of the cylindrical bottom of the back-drilled hole. Therefore, the cone depth compensation value caused by the cone-shaped drill bit needs to be added to the supplementary value. Cone depth compensation value = [(drill radius) / tan(drill point angle*0.5)].

[0073] S4: Back-drill according to the actual drilling depth.

[0074] As mentioned above, if the compensation value includes the thickness of the aluminum sheet, the corresponding aluminum sheet needs to be placed on the surface of the printed circuit board before back drilling. If the compensation value does not include the thickness of the aluminum sheet, the back drilling process can be performed directly without placing the aluminum sheet.

[0075] The actual drilling depth calculated above in the present application can be integrated into the back-drilling program, that is, the calibrated back-drilling program. The calibrated back-drilling program is used to drill holes in the printed circuit board, which can avoid the back-drilling error caused by inaccurate thickness of the printed circuit board in the prior art. At the same time, it also fully considers the influence of the thickness of the aluminum sheet and the shape of the drill bit on the drilling depth, thereby further improving the drilling accuracy.

[0076] Example 3

[0077] like Figure 1 As shown, the present application provides a printed circuit board back drilling depth correction method, comprising:

[0078] S1: Measure the actual thickness of the printed circuit board at each back-drilling hole position; specifically include:

[0079] S11: placing a pad and a first aluminum sheet on a drilling table in sequence, executing a first back-drilling procedure in the first aluminum sheet to obtain a first back-drilled hole, and measuring a distance H1 between the bottom of the first back-drilled hole and the drilling table.

[0080] S12 places a pad, a printed circuit board, and a second aluminum sheet on the drilling rig table in sequence, executes a second back drilling procedure in the second aluminum sheet to obtain a second back drilling hole, and measures a distance H2 between the bottom of the second back drilling hole and the drilling rig table; wherein the material and thickness of the first aluminum sheet and the second aluminum sheet are the same; and the first back drilling procedure and the second back drilling procedure are the same.

[0081] S13 The actual thickness value of the printed circuit board at each back-drilling hole position T = |H1-H2|.

[0082] The distance H1 between the bottom of the first back-drilled hole and the drilling rig table and the distance H2 between the bottom of the second back-drilled hole and the drilling rig table can be measured by the principle of capacitive height detection or the principle of resistive height detection.

[0083] S2: Determine whether the actual thickness value of the printed board at each back-drilling hole position exceeds the standard upper limit value or the standard lower limit value. If it exceeds the standard upper limit value or the standard lower limit value, correct the actual thickness value of the printed board to obtain the corrected thickness value of the printed board; if it does not exceed the standard upper limit value or the standard lower limit value, retain the actual thickness value of the printed board.

[0084] Specifically include:

[0085] S21: Measure the actual thickness at various positions in the printed board, where the maximum and minimum measured values ​​are the upper and lower limits of the standard. Specifically, the actual thickness at various positions in the printed board can be measured by a contact-type board thickness detection device or an optical non-contact board thickness detection device. Here, the actual thickness at various positions of the printed board is measured, not only at the back-drilled hole position, but also at various positions other than the back-drilled hole.

[0086] S22: Figure 2 As shown in FIG. 1 , the printed circuit board is divided into a central area S0 and four edge areas, which are named S1, S2, S3 and S4. The central area S0 is located at the center of the printed circuit board and is also a rectangular structure. The upper edge area S1, the left edge area S2, the lower edge area S3 and the right edge area S4 surround the outer side of the central area S0 and are located at the edge of the printed circuit board. The width of the edge area is 25-35 mm, as shown in FIG. Figure 2 As shown, it can be 30 mm in particular. The width here refers to the dimension from the side length of the printed circuit board in the edge area to the side length of the center area.

[0087] S23: For the actual thickness value of the printed board that exceeds the standard upper limit value or the standard lower limit value in each area, calculate the average value of the M actual thickness values ​​of the printed board that do not exceed the standard upper limit value or the standard lower limit value in the area, as the corrected thickness value of the printed board at the corresponding back drilling position; M is an integer greater than 1, and the number of M does not exceed the number of normal actual thickness values ​​of the printed board in the area, and the normal actual thickness value of the printed board refers to the actual thickness value of the printed board that does not exceed the standard upper limit value or the standard lower limit value.

[0088] When executing the first back-drilling program or the second back-drilling program, the first back-drilling program or the second back-drilling program includes a positioning program, and the positioning program records the coordinates of each back-drilling hole. The coordinates of the positioning holes in the printed circuit board can be matched with the coordinates of the drilling machine table, thereby achieving the matching and conversion of the coordinate system, and accurately positioning the coordinate position of each back-drilling hole. When performing regional division, regional division can also be performed with the help of the coordinate system.

[0089] S3: Calculate the actual drilling depth at each back drilling hole position according to the corrected thickness value of the printed board at each back drilling hole position or the proportional relationship between the actual thickness value of the printed board and the theoretical thickness value of the printed board.

[0090] Specifically, the actual drilling depth = (T 实际 / T 理论 )×D 理论+ thickness of aluminum sheet + [(drill radius) / tan(drill point angle*0.5)]; when the actual thickness of the printed board does not exceed the upper or lower limit of the standard, T 实际 is the actual thickness of the printed board; when the actual thickness of the printed board exceeds the standard upper limit or standard lower limit, T 实际 is the corrected thickness value of the printed circuit board; K is the compensation value.

[0091] Aluminum sheet refers to the aluminum sheet covering the printed circuit board when performing the back drilling procedure. When drilling the printed circuit board, the backing plate, printed circuit board and aluminum sheet are placed in the drilling machine table in sequence.

[0092] S4: Back-drill according to the actual drilling depth.

[0093] Example 4

[0094] like Figure 1 As shown, the present application provides a printed circuit board back drilling depth correction method, comprising:

[0095] S1: Measure the actual thickness of the printed circuit board at each back-drilling hole position; specifically include:

[0096] S11: placing a pad and a first aluminum sheet on a drilling table in sequence, executing a first back-drilling procedure in the first aluminum sheet to obtain a first back-drilled hole, and measuring a distance H1 between the bottom of the first back-drilled hole and the drilling table.

[0097] S12 places a pad, a printed circuit board, and a second aluminum sheet on the drilling rig table in sequence, executes a second back drilling procedure in the second aluminum sheet to obtain a second back drilling hole, and measures a distance H2 between the bottom of the second back drilling hole and the drilling rig table; wherein the material and thickness of the first aluminum sheet and the second aluminum sheet are the same; and the first back drilling procedure and the second back drilling procedure are the same.

[0098] S13 The actual thickness value of the printed circuit board at each back-drilling hole position T = |H1-H2|.

[0099] The distance H1 between the bottom of the first back-drilled hole and the drilling rig table and the distance H2 between the bottom of the second back-drilled hole and the drilling rig table can be measured by the principle of capacitive height detection or the principle of resistive height detection.

[0100] S2: Determine whether the actual thickness value of the printed board at each back-drilling hole position exceeds the standard upper limit value or the standard lower limit value. If it exceeds the standard upper limit value or the standard lower limit value, correct the actual thickness value of the printed board to obtain the corrected thickness value of the printed board; if it does not exceed the standard upper limit value or the standard lower limit value, retain the actual thickness value of the printed board.

[0101] Specifically include:

[0102] S21: The standard upper limit value and the standard lower limit value of the printed circuit board are calculated according to the theoretical stacking structure of the printed circuit board, that is, the standard upper limit value and the standard lower limit value are determined according to the design theoretical value of the printed circuit board. During the design and production process of the printed circuit board, the printed circuit board is formed by laminating multiple layers. During the lamination process, the material and thickness of each layer are determined. Therefore, according to its theoretical design value, combined with the empirical value, the standard upper limit value and the standard lower limit value of the printed circuit board can be obtained.

[0103] S22: Figure 3 As shown, the 16 regions in the printed circuit board are divided in a matrix arrangement. For example, when the printed circuit board is a rectangular parallelepiped, the printed circuit board can be divided into 4 rows and 4 columns in a matrix manner.

[0104] S23: For the actual thickness value of the printed board in each area that exceeds the standard upper limit value or the standard lower limit value, calculate the average value of the actual thickness values ​​of the three printed boards in the area that do not exceed the standard upper limit value or the standard lower limit value, as the corrected thickness value of the printed board at the corresponding back drilling position.

[0105] When executing the first back-drilling program or the second back-drilling program, the first back-drilling program or the second back-drilling program includes a positioning program, and the positioning program records the coordinates of each back-drilling hole. The coordinates of the positioning holes in the printed circuit board can be matched with the coordinates of the drilling machine table, thereby achieving the matching and conversion of the coordinate system, and accurately positioning the coordinate position of each back-drilling hole. When performing regional division, regional division can also be performed with the help of the coordinate system.

[0106] S3: Calculate the actual drilling depth at each back drilling hole position according to the corrected thickness value of the printed board at each back drilling hole position or the proportional relationship between the actual thickness value of the printed board and the theoretical thickness value of the printed board.

[0107] Specifically, the actual drilling depth = (T 实际 / T 理论 )×D 理论 +[(drill radius) / tan(drill point angle*0.5)]; where, when the actual thickness of the printed board does not exceed the upper or lower limit of the standard, T 实际 is the actual thickness of the printed board; when the actual thickness of the printed board exceeds the standard upper limit or standard lower limit, T 实际 is the corrected thickness value of the printed circuit board; K is the compensation value.

[0108] S4: Back-drill according to the actual drilling depth.

[0109] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0110] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for correcting the back drilling depth of a printed circuit board, characterized in that: include: S1: Measure the actual thickness of the printed circuit board at each back-drilling hole position; S2: judging whether the actual thickness value of the printed board at each back-drilling hole position exceeds the standard upper limit value or the standard lower limit value, if it exceeds the standard upper limit value or the standard lower limit value, correcting the actual thickness value of the printed board to obtain the corrected thickness value of the printed board; if it does not exceed the standard upper limit value or the standard lower limit value, retaining the actual thickness value of the printed board; S3: Calculate the actual drilling depth at each back drilling hole position according to the corrected thickness value of the printed board at each back drilling hole position or the proportional relationship between the actual thickness value of the printed board and the theoretical thickness value of the printed board; S4: Back-drill according to the actual drilling depth.

2. A printed circuit board back drilling depth correction method according to claim 1, characterized in that: The method for measuring the actual thickness value of the printed circuit board at each back-drilling hole position in step S1 includes: Place a backing plate and a first aluminum sheet on the drilling machine table in sequence, perform a first back drilling procedure in the first aluminum sheet to obtain a first back drilled hole, and measure a distance H1 between the bottom of the first back drilled hole and the drilling machine table; A backing plate, a printed circuit board, and a second aluminum sheet are sequentially placed on the drilling machine table, a second back drilling procedure is performed in the second aluminum sheet to obtain a second back drilling hole, and a distance H2 between the bottom of the second back drilling hole and the drilling machine table is measured; wherein the first aluminum sheet and the second aluminum sheet have the same material and thickness; and the first back drilling procedure and the second back drilling procedure are the same; The actual thickness value of the printed circuit board at each back drilling hole position is T = |H1-H2|.

3. A printed circuit board back drilling depth correction method according to claim 1, characterized in that: The method for obtaining the standard upper limit value and the standard lower limit value comprises: measuring the actual thickness at various positions in the printed board, wherein the maximum measured value and the minimum measured value are the standard upper limit value and the standard lower limit value; Alternatively, the method for obtaining the standard upper limit value and the standard lower limit value includes: calculating the standard upper limit value and the standard lower limit value of the printed circuit board according to the theoretical stacking structure of the printed circuit board.

4. A printed circuit board back drilling depth correction method according to claim 3, characterized in that: The actual thickness at each position of the printed board is measured by a contact-type board thickness detection device or an optical non-contact board thickness detection device.

5. A printed circuit board back drilling depth correction method according to claim 1, characterized in that: In step S2, the actual thickness value of the printed circuit board is corrected, specifically including: The printed circuit board is divided into regions, and for the actual thickness value of the printed circuit board in each region that exceeds the standard upper limit value or the standard lower limit value, the average value of the actual thickness values ​​of the printed circuit boards in the region that do not exceed the standard upper limit value or the standard lower limit value is calculated as the corrected thickness value of the printed circuit board at the corresponding back drilling position; M is an integer greater than 1.

6. A printed circuit board back drilling depth correction method according to claim 5, characterized in that: The area division of the printed circuit board includes: dividing the printed circuit board into a central area and X edge areas, wherein the central area is located at the center of the printed circuit board, and the edge areas surround the central area and are located at the edge of the printed circuit board.

7. A printed circuit board back drilling depth correction method according to claim 6, characterized in that: The printed circuit board is a rectangular parallelepiped, and there are four edge regions, which correspond to the four sides of the printed circuit board and are respectively located outside the central region. The width of the edge region is 25-35 mm.

8. A printed circuit board back drilling depth correction method according to claim 5, characterized in that: The said dividing the printed circuit board into regions includes: dividing the Y regions in the printed circuit board into regions in a matrix arrangement.

9. A printed circuit board back drilling depth correction method according to claim 1, characterized in that: The actual drilling depth at each back-drilling position is calculated in step S3, specifically including: Actual drilling depth = (T 实际 / T 理论 )×D 理论 +K; when the actual thickness of the printed board does not exceed the upper or lower limit of the standard, T 实际 is the actual thickness of the printed board; when the actual thickness of the printed board exceeds the standard upper limit or standard lower limit, T 实际 is the corrected thickness value of the printed circuit board; K is the compensation value.

10. A printed circuit board back drilling depth correction method according to claim 9, characterized in that: When performing the back drilling procedure, when an aluminum sheet is placed on the printed circuit board, K = aluminum sheet thickness + [(drill radius) / tan(drill point angle*0.5)]; When the back drilling procedure is performed and no aluminum sheet is placed on the printed circuit board, K = [(drill radius) / tan(drill point angle*0.5)].

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