Circuit board back drilling method and circuit board

Abstract

The invention relates to a circuit board back drilling method and a circuit board. According to the technical scheme, the circuit board back drilling method is characterized by comprising the steps that the actual board thickness corresponding to all back drilling hole positions in the circuit board is obtained; dividing the actual plate thickness corresponding to each back drilling hole position into piles, and calculating the average plate thickness of each pile; the actual back drilling depth of each back drilling hole position is calculated according to the piling average plate thickness and the actual plate thickness corresponding to each back drilling hole position; performing back drilling on each back drilling hole position according to the actual back drilling depth of each back drilling hole position; according to the method and the device, the stub can be removed from the actual back drilling depth of each back drilling hole position, the back drilling stub is controlled within the tolerance of 2-6mil, and the yield of the back drilling circuit board is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and more particularly to a circuit board back drilling method and a circuit board. Background Art

[0002] Back drilling is an advanced process technology in circuit board manufacturing. Its main principle is to drill away the unnecessary copper-plated hole wall from the back of the circuit board that has been drilled and electroplated, thereby reducing the length of the via stub. In multi-layer circuit boards, the length of the back drilling stub will cause signal reflection, scattering, interference and delay, affecting signal integrity. In order to improve this situation, the back drilling process was introduced. The existing circuit board back drilling process usually adopts the back drilling fixed drilling depth process and the back drilling mapping process.

[0003] The back drilling fixed drilling depth process means that the back drilling machine is directly manufactured according to the drilling depth given by the system, and does not participate in the plate thickness analysis and calculation.

[0004] The back-drill mapping process refers to the process of detecting the height of the aluminum cover sheet and the bakelite plate with a drill needle before back-drilling, calculating the initial value of the board surface processing, detecting the board thickness and the initial thickness of the machine, and finally obtaining data to calculate the actual back-drilling depth, and back-drilling the circuit board according to the actual back-drilling depth. The back-drilling mapping process involves the analysis and calculation of the board thickness, but there are certain limitations for the control of high-precision stubs above 3mm: first, if the actual board thickness differs too much from the theoretical board thickness, the calculated actual back-drilling depth will have a serious deviation; second, in the actual back-drilling process of mapping, the spindle position of the same type of hole (the drill diameter and drilling depth are the same) is a fixed value, and different types of holes can be processed at different depths. In the process of circuit board production, it is often the case that the same type of holes are located at different positions in the board and the board thickness is inconsistent. At this time, the actual back-drilling depth can only be taken as the average value of the actual back-drilling depth calculated for all holes. If the board thickness exceeds the tolerance too much, the residual pile will also fluctuate greatly, and it cannot meet the requirements of high-precision back-drilling.

[0005] In traditional circuit board products, the requirements for back drilling stubs are not high, generally controlled within 2-12mil. As the product requirements for high-speed signals become higher and higher, the requirements for back drilling stubs are becoming more and more stringent. In the invention patent with patent number CN202011453503.6 "A method for improving the accuracy of PCB back drilling depth", it is mentioned that the PCB thickness data is fully scanned by laser measurement to overcome the problem of uneven PCB thickness and improve the back drilling accuracy. This solution can only make a comprehensive analysis of the thickness of the entire board, and cannot measure the thickness of a single point. As the control of PCB back drilling processing stub becomes more and more stringent, this solution can no longer meet the processing of drilling depth of 3-5mm and back drilling stub control of 2-6mil. Summary of the invention

[0006] In view of the deficiencies in the prior art, an object of the present invention is to provide a circuit board back drilling method and a circuit board to solve the above problems.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions: A circuit board back drilling method, comprising: obtaining the actual board thickness corresponding to all back drilling holes in the circuit board;

[0008] The actual plate thickness corresponding to each back-drilling hole position is divided into piles, and the average plate thickness of each pile is calculated;

[0009] Calculate the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position;

[0010] Each back-drilling hole position is back-drilled according to the actual back-drilling depth of each back-drilling hole position.

[0011] By obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board, it is convenient to analyze the holes of the same hole type according to the actual board thickness and the back-drilled hole position. The actual board thickness corresponding to each back-drilled hole position is divided into piles according to the back-drilling depth and drill diameter of each back-drilled hole position, and the average board thickness of each pile is calculated. The holes of the same hole type are divided into piles at intervals of a certain preset value, and the average board thickness of each pile is calculated. The actual back-drilling depth of each back-drilled hole position is calculated by combining the average board thickness of the pile and the actual board thickness. The actual back-drilling depth is matched to the back-drilled hole position, and the back-drilling process is performed using a fixed drilling depth. Since the actual back-drilling depth is calculated based on the average board thickness of the pile corresponding to each back-drilled hole position and the actual board thickness, it can ensure that the actual back-drilling depth of each back-drilled hole position can remove the residual piles, and the back-drilling residual piles are controlled within a tolerance of 2-6mil, thereby improving the yield rate of the back-drilled circuit board.

[0012] Optionally, obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board includes:

[0013] Measuring the thickness of bakelite and aluminum sheets at all back-drilling holes in the circuit board to obtain first board thickness information corresponding to each back-drilling hole;

[0014] Measure the thickness of bakelite boards, production boards and aluminum sheets at all back-drilled holes in the circuit board to obtain second board thickness information corresponding to each back-drilled hole;

[0015] The actual plate thickness corresponding to each back-drilling hole position is calculated according to the first plate thickness information and the second plate thickness information corresponding to each back-drilling hole position.

[0016] In the production process of 3-6mm thick circuit boards, due to the limitations of factors such as the fixation of inner layer graphics (inconsistent residual copper rates in different areas), material properties (PP glue flow), and fixed pressing parameters (upper pressing point, heating rate, maximum temperature, maximum pressure, etc.), the circuit board cannot achieve 100% flatness on the board surface, and the thickness range is controlled at around 5%. Taking a 5mm thick board as an example, the board thickness after pressing has a tolerance of about 10mils, plus the machine drilling depth tolerance. If no special control is done, the back-drilled residual piles are likely to exceed the 2-6mil tolerance, which does not meet product requirements.

[0017] The actual board thickness of all back-drilled holes is measured through the back-drill mapping process. The thickness of the cover aluminum sheet and the bakelite board is first detected by the drill needle, and this is used as the first board thickness information. The thickness of the bakelite board, the production board and the aluminum sheet is then detected by the drill needle, and this is used as the second board thickness information. The actual board thickness of the corresponding back-drilled hole can be obtained by subtracting the first board thickness information from the second board thickness information.

[0018] Optionally, the actual plate thicknesses corresponding to the back-drilled hole positions are divided into piles, and the average plate thicknesses of the piles are calculated, including:

[0019] Classify all back-drilled hole positions to obtain the hole position type corresponding to each back-drilled hole position;

[0020] The actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information;

[0021] The average plate thickness of the stack is calculated according to the stack information.

[0022] Since the drill depth and drill bit diameter used in each back-drill hole position in the circuit board are different, it is necessary to first classify all the back-drill holes, regard the back-drill holes with the same drill depth and drill bit diameter as the same hole type, and pile the actual board thickness of the back-drilled holes of each hole type. For each pile, ensure that the extreme difference of the board thickness is within the corresponding preset value and calculate the average board thickness of the pile, which can improve the back-drilling processing quality yield of the corresponding back-drilled hole position and reduce the production risk of the product due to board thickness fluctuations.

[0023] Optionally, the actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information, including:

[0024] The actual plate thicknesses of the back-drilled holes of the same hole type are arranged in order from small to large, and the first preset value is used as an interval, and the stacking is started from the smallest actual plate thickness to obtain the stacking information of the back-drilled holes of the same hole type.

[0025] Specifically, the first preset value is usually 2mil, with 2mil as the extreme difference in board thickness for each pile. Starting from the thinnest board thickness, the board thickness range of the first pile of back-drilled holes is from the thinnest board thickness to the thinnest board thickness + 2mil; the board thickness range of the second pile of back-drilled holes is from the thinnest board thickness + 2mil to the thinnest board thickness + 4mil, and so on until the end of the thickest board thickness, and the pile information of the back-drilled holes of this hole type can be obtained.

[0026] Optionally, the calculating the average plate thickness of the stacking according to the stacking information includes:

[0027] The actual plate thickness of each sub-pile is averaged according to the sub-pile information to obtain the average plate thickness of each sub-pile.

[0028] Specifically, the average plate thickness of the corresponding pile is obtained by calculating the average value of the actual plate thickness corresponding to each pile. By calculating the average plate thickness of the pile, the quality yield of the back drilling processing at the corresponding back drilling hole position can be improved, and the production risk of the product due to plate thickness fluctuations can be reduced.

[0029] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position includes:

[0030] Calculate the actual plate thickness of the back-drilled holes of the same hole type to obtain the actual average plate thickness of the back-drilled holes of the same hole type;

[0031] The actual back drilling depth of each back drilling hole position is calculated according to the average plate thickness of the pile corresponding to each back drilling hole position and the actual average plate thickness.

[0032] The actual back drilling depth is calculated by calculating the actual average plate thickness and combining the average plate thickness of the pile with the actual average plate thickness to improve the accuracy of the actual back drilling depth, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0033] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile corresponding to each back drilling hole position and the actual average plate thickness includes:

[0034] The actual back drilling depth of each back drilling hole is calculated according to the back drilling depth formula, and the back drilling depth formula is as follows:

[0035] L = (H1 / H2)*H3+E2-E1;

[0036] Among them, L is the actual back drilling depth, H1 is the actual plate thickness of the back drilling hole, H2 is the theoretical plate thickness information of the back drilling hole, H3 is the theoretical back drilling depth of the back drilling hole, E1 is the actual average plate thickness of the back drilling hole, and E2 is the average plate thickness of the back drilling hole in the pile.

[0037] Specifically, since the actual average plate thickness and the average plate thickness of the pile are taken into consideration when calculating the actual back drilling depth, the actual back drilling depth is more consistent with the actual plate thickness of the corresponding back drilling hole position, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0038] Optionally, after obtaining the actual average plate thickness of the back-drilled hole of the hole type, the method further includes:

[0039] Whether there is any abnormality in the plate thickness measurement is determined based on the average plate thickness of each sub-pile and the actual average plate thickness. If yes, the actual plate thickness is re-obtained.

[0040] After calculating the actual average plate thickness of the back-drilling hole position, compare the actual average plate thickness with the average plate thickness of the pile to prevent abnormal calculation of the actual back-drilling depth due to abnormal plate thickness measurement.

[0041] Optionally, judging whether there is an abnormality in the plate thickness measurement according to the average plate thickness of each sub-pile and the actual average plate thickness includes:

[0042] The average plate thickness difference corresponding to each sub-pile is calculated based on the average plate thickness of each sub-pile and the actual average plate thickness;

[0043] The average plate thickness difference corresponding to each sub-pile is compared with the second preset value. If the average plate thickness difference is greater than the second preset value, it is determined that the plate thickness measurement is abnormal.

[0044] Specifically, the second preset value is usually set to 20 mil. When the average thickness difference between the average thickness of the pile and the actual average thickness is greater than 20 mil, it means that the thickness measurement is abnormal, and the actual thickness needs to be remeasured.

[0045] The present invention also provides a circuit board, which is prepared by the circuit board back drilling method as described above.

[0046] The tolerance of the back-drilling stubs of the circuit board prepared by the circuit board back-drilling method can be controlled within 2-6 mil, which can reduce the influence of the back-drilling stub length on signal reflection, scattering, interference and delay, and ensure signal integrity.

[0047] In summary, the present invention has the following beneficial effects:

[0048] By obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board, it is convenient to analyze the holes of the same hole type according to the actual board thickness and the back-drilled hole position. The actual board thickness corresponding to each back-drilled hole position is divided into piles according to the back-drilling depth and drill diameter of each back-drilled hole position, and the average board thickness of each pile is calculated. The holes of the same hole type are divided into piles at intervals of a certain preset value, and the average board thickness of each pile is calculated. The actual back-drilling depth of each back-drilled hole position is calculated by combining the average board thickness of the pile and the actual board thickness. The actual back-drilling depth is matched to the back-drilled hole position, and the back-drilling process is performed using a fixed drilling depth. Since the actual back-drilling depth is calculated based on the average board thickness of the pile corresponding to each back-drilled hole position and the actual board thickness, it can ensure that the actual back-drilling depth of each back-drilled hole position can remove the residual piles, and the back-drilling residual piles are controlled within a tolerance of 2-6mil, thereby improving the yield rate of the back-drilled circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a flow chart of the method of the present invention;

[0050] Figure 2 This is a schematic diagram of the circuit board before back drilling;

[0051] Figure 3 This is a schematic diagram of the circuit board after back drilling. DETAILED DESCRIPTION

[0052] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. Several embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0053] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. The terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0054] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0055] Embodiment 1

[0056] This embodiment provides a circuit board back drilling method, such as Figure 1 As shown, including:

[0057] Get the actual board thickness corresponding to all back-drilled holes in the circuit board;

[0058] The actual plate thickness corresponding to each back-drilling hole position is divided into piles, and the average plate thickness of each pile is calculated;

[0059] Calculate the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position;

[0060] Each back-drilling hole position is back-drilled according to the actual back-drilling depth of each back-drilling hole position.

[0061] By obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board, it is convenient to analyze the holes of the same hole type according to the actual board thickness and the back-drilled hole position. The actual board thickness corresponding to each back-drilled hole position is divided into piles according to the back-drilling depth and drill diameter of each back-drilled hole position, and the average board thickness of each pile is calculated. The holes of the same hole type are divided into piles at intervals of a certain preset value, and the average board thickness of each pile is calculated. The actual back-drilling depth of each back-drilled hole position is calculated by combining the average board thickness of the pile and the actual board thickness. The actual back-drilling depth is matched to the back-drilled hole position, and the back-drilling process is performed using a fixed drilling depth. Since the actual back-drilling depth is calculated based on the average board thickness of the pile corresponding to each back-drilled hole position and the actual board thickness, it can ensure that the actual back-drilling depth of each back-drilled hole position can remove the residual piles, and the back-drilling residual piles are controlled within a tolerance of 2-6mil, thereby improving the yield rate of the back-drilled circuit board.

[0062] Optionally, obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board includes:

[0063] Measuring the thickness of bakelite and aluminum sheets at all back-drilling holes in the circuit board to obtain first board thickness information corresponding to each back-drilling hole;

[0064] Measure the thickness of bakelite boards, production boards and aluminum sheets at all back-drilled holes in the circuit board to obtain second board thickness information corresponding to each back-drilled hole;

[0065] The actual plate thickness corresponding to each back-drilling hole position is calculated according to the first plate thickness information and the second plate thickness information corresponding to each back-drilling hole position.

[0066] In the production process of 3-6mm thick circuit boards, due to the limitations of factors such as the fixation of inner layer graphics (inconsistent residual copper rates in different areas), material properties (PP glue flow), and fixed pressing parameters (upper pressing point, heating rate, maximum temperature, maximum pressure, etc.), the circuit board cannot achieve 100% flatness on the board surface, and the thickness range is controlled at around 5%. Taking a 5mm thick board as an example, the board thickness after pressing has a tolerance of about 10mils, plus the machine drilling depth tolerance. If no special control is done, the back-drilled residual piles are likely to exceed the 2-6mil tolerance, which does not meet product requirements.

[0067] The actual board thickness of all back-drilled holes is measured through the back-drill mapping process. The thickness of the cover aluminum sheet and the bakelite board is first detected by the drill needle, and this is used as the first board thickness information. The thickness of the bakelite board, the production board and the aluminum sheet is then detected by the drill needle, and this is used as the second board thickness information. The actual board thickness of the corresponding back-drilled hole can be obtained by subtracting the first board thickness information from the second board thickness information.

[0068] Optionally, the actual plate thicknesses corresponding to the back-drilled hole positions are divided into piles, and the average plate thicknesses of the piles are calculated, including:

[0069] Classify all back-drilled hole positions to obtain the hole position type corresponding to each back-drilled hole position;

[0070] The actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information;

[0071] The average plate thickness of the stack is calculated according to the stack information.

[0072] Since the drill depth and drill bit diameter used in each back-drill hole position in the circuit board are different, it is necessary to first classify all the back-drill holes, regard the back-drill holes with the same drill depth and drill bit diameter as the same hole type, and pile the actual board thickness of the back-drilled holes of each hole type. For each pile, ensure that the extreme difference of the board thickness is within the corresponding preset value and calculate the average board thickness of the pile, which can improve the back-drilling processing quality yield of the corresponding back-drilled hole position and reduce the production risk of the product due to board thickness fluctuations.

[0073] Optionally, the actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information, including:

[0074] The actual plate thicknesses of the back-drilled holes of the same hole type are arranged in order from small to large, and the first preset value is used as an interval, and the stacking is started from the smallest actual plate thickness to obtain the stacking information of the back-drilled holes of the same hole type.

[0075] Specifically, the first preset value is usually 2mil, with 2mil as the extreme difference in board thickness for each pile. Starting from the thinnest board thickness, the board thickness range of the first pile of back-drilled holes is from the thinnest board thickness to the thinnest board thickness + 2mil; the board thickness range of the second pile of back-drilled holes is from the thinnest board thickness + 2mil to the thinnest board thickness + 4mil, and so on until the end of the thickest board thickness, and the pile information of the back-drilled holes of this hole type can be obtained.

[0076] Optionally, the calculating the average plate thickness of the stacking according to the stacking information includes:

[0077] The actual plate thickness of each sub-pile is averaged according to the sub-pile information to obtain the average plate thickness of each sub-pile.

[0078] Specifically, the average plate thickness of the corresponding pile is obtained by calculating the average value of the actual plate thickness corresponding to each pile. By calculating the average plate thickness of the pile, the quality yield of the back drilling processing at the corresponding back drilling hole position can be improved, and the production risk of the product due to plate thickness fluctuations can be reduced.

[0079] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position includes:

[0080] Calculate the actual plate thickness of the back-drilled holes of the same hole type to obtain the actual average plate thickness of the back-drilled holes of the same hole type;

[0081] The actual back drilling depth of each back drilling hole position is calculated according to the average plate thickness of the pile corresponding to each back drilling hole position and the actual average plate thickness.

[0082] The actual back drilling depth is calculated by calculating the actual average plate thickness and combining the average plate thickness of the pile with the actual average plate thickness to improve the accuracy of the actual back drilling depth, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0083] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile corresponding to each back drilling hole position and the actual average plate thickness includes:

[0084] The actual back drilling depth of each back drilling hole is calculated according to the back drilling depth formula, and the back drilling depth formula is as follows:

[0085] L = (H1 / H2)*H3+E2-E1;

[0086] Among them, L is the actual back drilling depth, H1 is the actual plate thickness of the back drilling hole, H2 is the theoretical plate thickness information of the back drilling hole, H3 is the theoretical back drilling depth of the back drilling hole, E1 is the actual average plate thickness of the back drilling hole, and E2 is the average plate thickness of the back drilling hole in the pile.

[0087] Specifically, since the actual average plate thickness and the average plate thickness of the pile are taken into consideration when calculating the actual back drilling depth, the actual back drilling depth is more consistent with the actual plate thickness of the corresponding back drilling hole position, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0088] Specifically, taking a 5mm thick board as an example, assuming the same type of back-drilling hole position, the theoretical back-drilling depth is 3.175mm, and the board thickness after lamination has a tolerance of about 10mil. The actual board thickness is shown in the following table:

[0089]

[0090] The actual average plate thickness can be obtained to be 4.995mm. The actual plate thickness of the back-drilled hole position is divided into piles, and the results are shown in the following table:

[0091]

[0092] Calculate according to the back drilling depth formula. Taking the second pile as an example, the back drilling depth of the back drilling hole position with an actual plate thickness of 4.85 mm in the second pile is (4.85 / 5)*3.175+4.852-4.995=2.930 mm. Therefore, the back drilling is performed at a fixed depth of 2.930 mm for the back drilling hole position.

[0093] Embodiment 2

[0094] This embodiment provides a circuit board back drilling method, including:

[0095] Get the actual board thickness corresponding to all back-drilled holes in the circuit board;

[0096] The actual plate thickness corresponding to each back-drilling hole position is divided into piles, and the average plate thickness of each pile is calculated;

[0097] Calculate the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position;

[0098] Each back-drilling hole position is back-drilled according to the actual back-drilling depth of each back-drilling hole position.

[0099] By obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board, it is convenient to analyze the holes of the same hole type according to the actual board thickness and the back-drilled hole position. The actual board thickness corresponding to each back-drilled hole position is divided into piles according to the back-drilling depth and drill diameter of each back-drilled hole position, and the average board thickness of each pile is calculated. The holes of the same hole type are divided into piles at intervals of a certain preset value, and the average board thickness of each pile is calculated. The actual back-drilling depth of each back-drilled hole position is calculated by combining the average board thickness of the pile and the actual board thickness. The actual back-drilling depth is matched to the back-drilled hole position, and the back-drilling process is performed using a fixed drilling depth. Since the actual back-drilling depth is calculated based on the average board thickness of the pile corresponding to each back-drilled hole position and the actual board thickness, it can ensure that the actual back-drilling depth of each back-drilled hole position can remove the residual piles, and the back-drilling residual piles are controlled within a tolerance of 2-6mil, thereby improving the yield rate of the back-drilled circuit board.

[0100] Optionally, obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board includes:

[0101] Measuring the thickness of bakelite and aluminum sheets at all back-drilling holes in the circuit board to obtain first board thickness information corresponding to each back-drilling hole;

[0102] Measure the thickness of bakelite boards, production boards and aluminum sheets at all back-drilled holes in the circuit board to obtain second board thickness information corresponding to each back-drilled hole;

[0103] The actual plate thickness corresponding to each back-drilling hole position is calculated according to the first plate thickness information and the second plate thickness information corresponding to each back-drilling hole position.

[0104] In the production process of 3-6mm thick circuit boards, due to the limitations of factors such as the fixation of inner layer graphics (inconsistent residual copper rates in different areas), material properties (PP glue flow), and fixed pressing parameters (upper pressing point, heating rate, maximum temperature, maximum pressure, etc.), the circuit board cannot achieve 100% flatness on the board surface, and the thickness range is controlled at around 5%. Taking a 5mm thick board as an example, the board thickness after pressing has a tolerance of about 10mils, plus the machine drilling depth tolerance. If no special control is done, the back-drilled residual piles are likely to exceed the 2-6mil tolerance, which does not meet product requirements.

[0105] The actual board thickness of all back-drilled holes is measured through the back-drill mapping process. The thickness of the cover aluminum sheet and the bakelite board is first detected by the drill needle, and this is used as the first board thickness information. The thickness of the bakelite board, the production board and the aluminum sheet is then detected by the drill needle, and this is used as the second board thickness information. The actual board thickness of the corresponding back-drilled hole can be obtained by subtracting the first board thickness information from the second board thickness information.

[0106] Optionally, the actual plate thicknesses corresponding to the back-drilled hole positions are divided into piles, and the average plate thicknesses of the piles are calculated, including:

[0107] Classify all back-drilled hole positions to obtain the hole position type corresponding to each back-drilled hole position;

[0108] The actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information;

[0109] The average plate thickness of the stack is calculated according to the stack information.

[0110] Since the drill depth and drill bit diameter used in each back-drill hole position in the circuit board are different, it is necessary to first classify all the back-drill holes, regard the back-drill holes with the same drill depth and drill bit diameter as the same hole type, and pile the actual board thickness of the back-drilled holes of each hole type. For each pile, ensure that the extreme difference of the board thickness is within the corresponding preset value and calculate the average board thickness of the pile, which can improve the back-drilling processing quality yield of the corresponding back-drilled hole position and reduce the production risk of the product due to board thickness fluctuations.

[0111] Optionally, the actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information, including:

[0112] The actual plate thicknesses of the back-drilled holes of the same hole type are arranged in order from small to large, and the first preset value is used as an interval, and the stacking is started from the smallest actual plate thickness to obtain the stacking information of the back-drilled holes of the same hole type.

[0113] Specifically, the first preset value is usually 2mil, with 2mil as the extreme difference in board thickness for each pile. Starting from the thinnest board thickness, the board thickness range of the first pile of back-drilled holes is from the thinnest board thickness to the thinnest board thickness + 2mil; the board thickness range of the second pile of back-drilled holes is from the thinnest board thickness + 2mil to the thinnest board thickness + 4mil, and so on until the end of the thickest board thickness, and the pile information of the back-drilled holes of this hole type can be obtained.

[0114] Optionally, the calculating the average plate thickness of the stacking according to the stacking information includes:

[0115] The actual plate thickness of each sub-pile is averaged according to the sub-pile information to obtain the average plate thickness of each sub-pile.

[0116] Specifically, the average plate thickness of the corresponding pile is obtained by calculating the average value of the actual plate thickness corresponding to each pile. By calculating the average plate thickness of the pile, the quality yield of the back drilling processing at the corresponding back drilling hole position can be improved, and the production risk of the product due to plate thickness fluctuations can be reduced.

[0117] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position includes:

[0118] Calculate the actual plate thickness of the back-drilled holes of the same hole type to obtain the actual average plate thickness of the back-drilled holes of the same hole type;

[0119] The actual back drilling depth of each back drilling hole position is calculated according to the average plate thickness of the pile corresponding to each back drilling hole position and the actual average plate thickness.

[0120] The actual back drilling depth is calculated by calculating the actual average plate thickness and combining the average plate thickness of the pile with the actual average plate thickness to improve the accuracy of the actual back drilling depth, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0121] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile corresponding to each back drilling hole position and the actual average plate thickness includes:

[0122] The actual back drilling depth of each back drilling hole is calculated according to the back drilling depth formula, and the back drilling depth formula is as follows:

[0123] L = (H1 / H2)*H3+E2-E1;

[0124] Among them, L is the actual back drilling depth, H1 is the actual plate thickness of the back drilling hole, H2 is the theoretical plate thickness information of the back drilling hole, H3 is the theoretical back drilling depth of the back drilling hole, E1 is the actual average plate thickness of the back drilling hole, and E2 is the average plate thickness of the back drilling hole in the pile.

[0125] Specifically, since the actual average plate thickness and the average plate thickness of the pile are taken into consideration when calculating the actual back drilling depth, the actual back drilling depth is more consistent with the actual plate thickness of the corresponding back drilling hole position, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0126] Specifically, taking a 5mm thick board as an example, assuming the same type of back-drilling hole position, the theoretical back-drilling depth is 3.175mm, and the board thickness after lamination has a tolerance of about 10mil. The actual board thickness is shown in the following table:

[0127]

[0128] The actual average plate thickness can be obtained to be 4.995mm. The actual plate thickness of the back-drilled hole position is divided into piles, and the results are shown in the following table:

[0129]

[0130]

[0131] Calculate according to the back drilling depth formula. Taking the second pile as an example, the back drilling depth of the back drilling hole position with an actual plate thickness of 4.85 mm in the second pile is (4.85 / 5)*3.175+4.852-4.995=2.930 mm. Therefore, the back drilling is performed at a fixed depth of 2.930 mm for the back drilling hole position.

[0132] Optionally, after obtaining the actual average plate thickness of the back-drilled hole of the hole type, the method further includes:

[0133] Whether there is any abnormality in the plate thickness measurement is determined based on the average plate thickness of each sub-pile and the actual average plate thickness. If yes, the actual plate thickness is re-obtained.

[0134] After calculating the actual average plate thickness of the back-drilling hole position, compare the actual average plate thickness with the average plate thickness of the pile to prevent abnormal calculation of the actual back-drilling depth due to abnormal plate thickness measurement.

[0135] Optionally, judging whether there is an abnormality in the plate thickness measurement according to the average plate thickness of each sub-pile and the actual average plate thickness includes:

[0136] The average plate thickness difference corresponding to each sub-pile is calculated based on the average plate thickness of each sub-pile and the actual average plate thickness;

[0137] The average plate thickness difference corresponding to each sub-pile is compared with the second preset value. If the average plate thickness difference is greater than the second preset value, it is determined that the plate thickness measurement is abnormal.

[0138] Specifically, the second preset value is usually set to 20 mil. When the average thickness difference between the average thickness of the pile and the actual average thickness is greater than 20 mil, it means that the thickness measurement is abnormal, and the actual thickness needs to be remeasured.

[0139] Embodiment 3

[0140] This embodiment provides a circuit board, which is prepared by the circuit board back drilling method as described above, including: obtaining the actual board thickness corresponding to all back drilling holes in the circuit board;

[0141] The actual plate thickness corresponding to each back-drilling hole position is divided into piles, and the average plate thickness of each pile is calculated;

[0142] Calculate the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position;

[0143] Each back-drilling hole position is back-drilled according to the actual back-drilling depth of each back-drilling hole position.

[0144] By obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board, it is convenient to analyze the holes of the same hole type according to the actual board thickness and the back-drilled hole position. The actual board thickness corresponding to each back-drilled hole position is divided into piles according to the back-drilling depth and drill diameter of each back-drilled hole position, and the average board thickness of each pile is calculated. The holes of the same hole type are divided into piles at intervals of a certain preset value, and the average board thickness of each pile is calculated. The actual back-drilling depth of each back-drilled hole position is calculated by combining the average board thickness of the pile and the actual board thickness. The actual back-drilling depth is matched to the back-drilled hole position, and the back-drilling process is performed using a fixed drilling depth. Since the actual back-drilling depth is calculated based on the average board thickness of the pile corresponding to each back-drilled hole position and the actual board thickness, it can ensure that the actual back-drilling depth of each back-drilled hole position can remove the residual piles, and the back-drilling residual piles are controlled within a tolerance of 2-6mil, thereby improving the yield rate of the back-drilled circuit board.

[0145] Optionally, obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board includes:

[0146] Measuring the thickness of bakelite and aluminum sheets at all back-drilling holes in the circuit board to obtain first board thickness information corresponding to each back-drilling hole;

[0147] Measure the thickness of bakelite boards, production boards and aluminum sheets at all back-drilled holes in the circuit board to obtain second board thickness information corresponding to each back-drilled hole;

[0148] The actual plate thickness corresponding to each back-drilling hole position is calculated according to the first plate thickness information and the second plate thickness information corresponding to each back-drilling hole position.

[0149] In the production process of 3-6mm thick circuit boards, due to the limitations of factors such as the fixation of inner layer graphics (inconsistent residual copper rates in different areas), material properties (PP glue flow), and fixed pressing parameters (upper pressing point, heating rate, maximum temperature, maximum pressure, etc.), the circuit board cannot achieve 100% flatness on the board surface, and the thickness range is controlled at around 5%. Taking a 5mm thick board as an example, the board thickness after pressing has a tolerance of about 10mils, plus the machine drilling depth tolerance. If no special control is done, the back-drilled residual piles are likely to exceed the 2-6mil tolerance, which does not meet product requirements.

[0150] The actual board thickness of all back-drilled holes is measured through the back-drill mapping process. The thickness of the cover aluminum sheet and the bakelite board is first detected by the drill needle, and this is used as the first board thickness information. The thickness of the bakelite board, the production board and the aluminum sheet is then detected by the drill needle, and this is used as the second board thickness information. The actual board thickness of the corresponding back-drilled hole can be obtained by subtracting the first board thickness information from the second board thickness information.

[0151] Optionally, the actual plate thicknesses corresponding to the back-drilled hole positions are divided into piles, and the average plate thicknesses of the piles are calculated, including:

[0152] Classify all back-drilled hole positions to obtain the hole position type corresponding to each back-drilled hole position;

[0153] The actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information;

[0154] The average plate thickness of the stack is calculated according to the stack information.

[0155] Since the drill depth and drill bit diameter used in each back-drill hole position in the circuit board are different, it is necessary to first classify all the back-drill holes, regard the back-drill holes with the same drill depth and drill bit diameter as the same hole type, and pile the actual board thickness of the back-drilled holes of each hole type. For each pile, ensure that the extreme difference of the board thickness is within the corresponding preset value and calculate the average board thickness of the pile, which can improve the back-drilling processing quality yield of the corresponding back-drilled hole position and reduce the production risk of the product due to board thickness fluctuations.

[0156] Optionally, the actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information, including:

[0157] The actual plate thicknesses of the back-drilled holes of the same hole type are arranged in order from small to large, and the first preset value is used as an interval, and the stacking is started from the smallest actual plate thickness to obtain the stacking information of the back-drilled holes of the same hole type.

[0158] Specifically, the first preset value is usually 2mil, with 2mil as the extreme difference in board thickness for each pile. Starting from the thinnest board thickness, the board thickness range of the first pile of back-drilled holes is from the thinnest board thickness to the thinnest board thickness + 2mil; the board thickness range of the second pile of back-drilled holes is from the thinnest board thickness + 2mil to the thinnest board thickness + 4mil, and so on until the end of the thickest board thickness, and the pile information of the back-drilled holes of this hole type can be obtained.

[0159] Optionally, the calculating the average plate thickness of the stacking according to the stacking information includes:

[0160] The actual plate thickness of each sub-pile is averaged according to the sub-pile information to obtain the average plate thickness of each sub-pile.

[0161] Specifically, the average plate thickness of the corresponding pile is obtained by calculating the average value of the actual plate thickness corresponding to each pile. By calculating the average plate thickness of the pile, the quality yield of the back drilling processing at the corresponding back drilling hole position can be improved, and the production risk of the product due to plate thickness fluctuations can be reduced.

[0162] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position includes:

[0163] Calculate the actual plate thickness of the back-drilled holes of the same hole type to obtain the actual average plate thickness of the back-drilled holes of the same hole type;

[0164] The actual back drilling depth of each back drilling hole position is calculated according to the average plate thickness of the pile corresponding to each back drilling hole position and the actual average plate thickness.

[0165] The actual back drilling depth is calculated by calculating the actual average plate thickness and combining the average plate thickness of the pile with the actual average plate thickness to improve the accuracy of the actual back drilling depth, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0166] Optionally, the calculating the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile corresponding to each back drilling hole position and the actual average plate thickness includes:

[0167] The actual back drilling depth of each back drilling hole is calculated according to the back drilling depth formula, and the back drilling depth formula is as follows:

[0168] L = (H1 / H2)*H3+E2-E1;

[0169] Among them, L is the actual back drilling depth, H1 is the actual plate thickness of the back drilling hole, H2 is the theoretical plate thickness information of the back drilling hole, H3 is the theoretical back drilling depth of the back drilling hole, E1 is the actual average plate thickness of the back drilling hole, and E2 is the average plate thickness of the back drilling hole in the pile.

[0170] Specifically, since the actual average plate thickness and the average plate thickness of the pile are taken into consideration when calculating the actual back drilling depth, the actual back drilling depth is more consistent with the actual plate thickness of the corresponding back drilling hole position, thereby improving the back drilling processing quality yield of the corresponding back drilling hole position and reducing the production risk of the product due to plate thickness fluctuations.

[0171] Optionally, after obtaining the actual average plate thickness of the back-drilled hole of the hole type, the method further includes:

[0172] Whether there is any abnormality in the plate thickness measurement is determined based on the average plate thickness of each sub-pile and the actual average plate thickness. If yes, the actual plate thickness is re-obtained.

[0173] After calculating the actual average plate thickness of the back-drilling hole position, compare the actual average plate thickness with the average plate thickness of the pile to prevent abnormal calculation of the actual back-drilling depth due to abnormal plate thickness measurement.

[0174] Optionally, judging whether there is an abnormality in the plate thickness measurement according to the average plate thickness of each sub-pile and the actual average plate thickness includes:

[0175] The average plate thickness difference corresponding to each sub-pile is calculated based on the average plate thickness of each sub-pile and the actual average plate thickness;

[0176] The average plate thickness difference corresponding to each sub-pile is compared with the second preset value. If the average plate thickness difference is greater than the second preset value, it is determined that the plate thickness measurement is abnormal.

[0177] Specifically, the second preset value is usually set to 20 mil. When the average thickness difference between the average thickness of the pile and the actual average thickness is greater than 20 mil, it means that the thickness measurement is abnormal, and the actual thickness needs to be remeasured.

[0178] The tolerance of the back-drilling stubs of the circuit board prepared by the circuit board back-drilling method can be controlled within 2-6 mil, which can reduce the influence of the back-drilling stub length on signal reflection, scattering, interference and delay, and ensure signal integrity.

[0179] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A circuit board back drilling method, characterized in that: include: Get the actual board thickness corresponding to all back-drilled holes in the circuit board; The actual plate thickness corresponding to each back-drilling hole position is divided into piles, and the average plate thickness of each pile is calculated; Calculate the actual back drilling depth of each back drilling hole position according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position; Each back-drilling hole position is back-drilled according to the actual back-drilling depth of each back-drilling hole position.

2. A circuit board back drilling method according to claim 1, characterized in that: The step of obtaining the actual board thickness corresponding to all back-drilled holes in the circuit board includes: Measuring the thickness of bakelite and aluminum sheets at all back-drilling holes in the circuit board to obtain first board thickness information corresponding to each back-drilling hole; Measure the thickness of bakelite boards, production boards and aluminum sheets at all back-drilled holes in the circuit board to obtain second board thickness information corresponding to each back-drilled hole; The actual plate thickness corresponding to each back-drilling hole position is calculated according to the first plate thickness information and the second plate thickness information corresponding to each back-drilling hole position.

3. A circuit board back drilling method according to claim 2, characterized in that: The actual plate thickness corresponding to each back-drilling hole position is divided into piles, and the average plate thickness of each pile is calculated, including: Classify all back-drilled hole positions to obtain the hole position type corresponding to each back-drilled hole position; The actual plate thickness of back-drilled holes of the same hole type is grouped to obtain grouping information; The average plate thickness of the stack is calculated according to the stack information.

4. A circuit board back drilling method according to claim 3, characterized in that: The actual plate thickness of the back-drilled holes of the same hole type is grouped to obtain grouping information, including: The actual plate thicknesses of the back-drilled holes of the same hole type are arranged in order from small to large, and the first preset value is used as an interval, and the stacking is started from the smallest actual plate thickness to obtain the stacking information of the back-drilled holes of the same hole type.

5. A circuit board back drilling method according to claim 3, characterized in that: The calculating the average plate thickness of the stacking according to the stacking information includes: The actual plate thickness of each sub-pile is averaged according to the sub-pile information to obtain the average plate thickness of each sub-pile.

6. A circuit board back drilling method according to claim 3, characterized in that: The actual back drilling depth of each back drilling hole position is calculated according to the average plate thickness of each pile and the actual plate thickness corresponding to each back drilling hole position, including: Calculate the actual plate thickness of the back-drilled holes of the same hole type to obtain the actual average plate thickness of the back-drilled holes of the same hole type; The actual back drilling depth of each back drilling hole position is calculated according to the average plate thickness of the pile corresponding to each back drilling hole position and the actual average plate thickness.

7. A circuit board back drilling method according to claim 6, characterized in that: The actual back drilling depth of each back drilling hole position is calculated according to the average plate thickness of each pile corresponding to each back drilling hole position and the actual average plate thickness, including: The actual back drilling depth of each back drilling hole is calculated according to the back drilling depth formula, and the back drilling depth formula is as follows: L = (H1 / H2)*H3+E2-E1; Among them, L is the actual back drilling depth, H1 is the actual plate thickness of the back drilling hole, H2 is the theoretical plate thickness information of the back drilling hole, H3 is the theoretical back drilling depth of the back drilling hole, E1 is the actual average plate thickness of the back drilling hole, and E2 is the average plate thickness of the back drilling hole in the pile.

8. A circuit board back drilling method according to claim 6, characterized in that: After obtaining the actual average plate thickness of the back-drilled hole of the hole type, the method further includes: Whether there is any abnormality in the plate thickness measurement is determined based on the average plate thickness of each sub-pile and the actual average plate thickness. If yes, the actual plate thickness is re-obtained.

9. A circuit board back drilling method according to claim 8, characterized in that: The step of judging whether there is an abnormality in the plate thickness measurement according to the average plate thickness of each sub-pile and the actual average plate thickness comprises: The average plate thickness difference corresponding to each sub-pile is calculated based on the average plate thickness of each sub-pile and the actual average plate thickness; The average plate thickness difference corresponding to each sub-pile is compared with the second preset value. If the average plate thickness difference is greater than the second preset value, it is determined that the plate thickness measurement is abnormal.

10. A circuit board, characterized in that: The circuit board is prepared by the circuit board back drilling method as described in any one of claims 1 to 9.

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