Manufacturing method of back drilling hole

Abstract

The embodiment of the invention discloses a manufacturing method of a back drilling hole. The manufacturing method of the back drilling hole comprises the following steps: providing a multi-layer board and a plurality of standby multi-layer boards; a signal layer to be subjected to back drilling in the standby multilayer board is connected with the via hole through a lead to form a loop; carrying out copper deposition and electroplating treatment on the multi-layer board and the plurality of standby multi-layer boards; performing back drilling on the to-be-back-drilled holes of the standby multilayer board through a back drilling machine table, and recording the back drilling depth when an open circuit of a loop is detected; according to the back drilling depth and the drilling depth adjustment amount, the final back drilling depth is determined; the drilling depth adjustment amount is the sum of the preset stub length and the thickness of the signal layer; and performing back drilling on the multilayer board according to the final back drilling depth to form back drilling holes. According to the technical scheme provided by the embodiment of the invention, the accurate drilling depth of the back drill can be obtained, so that the precision control of the back drill stub is improved, and the product quality of the printed circuit board is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board, and particularly relates to a back drilling manufacturing method. BACKGROUND

[0002] With the progress of science and technology, the printed circuit board (PCB) industry has also developed rapidly, and various products have emerged in an endless stream. The quality requirements of products are also getting higher and higher. Among them, the high-speed signal backboard is particularly prominent. One of the main characteristics of high-speed backboard is the stability of signal transmission. The main performance is the back drilling of high-speed signal line. The effective transmission and stability of control signal are controlled by controlling the back drilling stub. Therefore, most of the back drilling products currently have extremely strict requirements for back drilling stub. The qualified production of back drilling stub is also one of the main difficulties of the back drilling process. The overage of back drilling stub will cause the PCB product to be scrapped, affecting the reliability of the PCB product signal transmission.

[0003] In the prior art, the manufacturing method of the back drilling stub includes a back drilling method by board thickness distribution or an automatic drilling depth adjustment method for each hole by laser measuring the board thickness.

[0004] However, although the manufacturing method has diversification, it has certain limitations and cannot effectively control the back drilling stub, thereby reducing the quality of the PCB product. SUMMARY

[0005] The present application provides a back drilling manufacturing method to obtain accurate back drilling depth, thereby improving the precision control of the back drilling stub and improving the quality of the PCB product.

[0006] According to an aspect of the present application, a back drilling manufacturing method is provided, which comprises:

[0007] A plurality of multi-layer boards and a plurality of spare multi-layer boards are provided. The signal layer of the back drilling hole in the spare multi-layer board is connected to form a loop through a lead and a via;

[0008] The multi-layer board and the plurality of spare multi-layer boards are subjected to copper deposition and electroplating treatment;

[0009] The back drilling machine is used to back drill the back drilling hole of the spare multi-layer board. When the loop is opened, the back drilling depth is recorded;

[0010] According to the back drilling depth and the drilling depth adjustment amount, the final back drilling depth is determined. The drilling depth adjustment amount is the sum of the preset stub length and the thickness of the signal layer;

[0011] According to the final back drilling depth, the multi-layer board is back drilled to form a back drilling hole.

[0012] Optionally, after the copper plating and electroplating treatment of the multi-layer board and the plurality of spare multi-layer boards, comprising:

[0013] Forming a welding ring on both sides of the to-be-back-drilled hole of the plurality of spare multi-layer boards.

[0014] Optionally, the back drilling machine table is provided with an open short circuit detection module and a back drilling backing plate device; the open short circuit detection module and the back drilling backing plate device are connected; the back drilling backing plate device is connected with the welding ring and the electroplated via hole respectively;

[0015] Back drilling the to-be-back-drilled hole of the spare multi-layer board by the back drilling machine table, and recording the back drilling depth when detecting the open circuit, comprising:

[0016] Back drilling the to-be-back-drilled hole of the spare multi-layer board by the back drilling tool;

[0017] Detecting the connection of the back drilling backing plate device with the welding ring and the electroplated via hole by the open short circuit detection module;

[0018] When the open short circuit detection module detects the open circuit, controlling the back drilling tool to stop drilling, and recording the back drilling depth.

[0019] Optionally, determining the final back drilling depth according to the back drilling depth and the drilling depth adjustment amount, comprising:

[0020] Determining the preset stub length according to the stub length range;

[0021] Determining the drilling depth adjustment amount according to the sum of the preset stub length and the thickness of the signal layer;

[0022] Determining the final back drilling depth according to the difference between the back drilling depth and the drilling depth adjustment amount.

[0023] Optionally, determining the preset stub length according to the stub length range, comprising:

[0024] Determining the preset stub length according to half of the sum of the maximum stub length and the minimum stub length in the stub length range;

[0025] Or;

[0026] Determining the preset stub length according to half of the sum of the maximum stub length and the minimum stub length in the stub length range plus a preset safety distance length.

[0027] Optionally, back drilling the to-be-back-drilled hole of the multi-layer board according to the final back drilling depth, and forming a back drilled hole, comprising:

[0028] Measuring the length of the stub to determine whether the length of the stub exceeds the stub length range;

[0029] When the length of the stub is within the stub length range, batch back drilling is performed on the to-be-back-drilled holes of the multi-layer boards.

[0030] Optionally, welding rings are formed on both sides of the to-be-back-drilled holes of the multiple standby multi-layer boards, including:

[0031] The multiple standby multi-layer boards are subjected to pre-process and dry film lamination;

[0032] Welding rings are formed on both sides of the to-be-back-drilled holes through exposure, development and etching.

[0033] Optionally, the multi-layer boards and the multiple standby multi-layer boards are provided, including:

[0034] The copper-clad boards and the multiple standby copper-clad boards are provided;

[0035] The multi-layer copper-clad boards and the multiple standby copper-clad boards are drilled through holes after pre-process and pressing;

[0036] The multi-layer boards and the multiple standby multi-layer boards are subjected to copper deposition and electroplating, including:

[0037] The through holes are subjected to copper deposition, and the board surfaces are subjected to electroplating.

[0038] Optionally, according to the back drilling depth and the drilling depth adjustment amount, the final back drilling depth is determined, and further including:

[0039] The average value of the maximum value and the minimum value of the final back drilling depths of the to-be-back-drilled holes at the same position of the multiple standby multi-layer boards is taken as the final back drilling depth of each to-be-back-drilled hole of the multi-layer boards;

[0040] Alternatively,

[0041] The average value of the maximum value and the minimum value of the final back drilling depths of all to-be-back-drilled holes of each drill sequence is taken as the final back drilling depth of each drill sequence of the multi-layer boards.

[0042] Optionally, when the length of the stub is within the stub length range, batch back drilling is performed on the to-be-back-drilled holes of the multi-layer boards, including:

[0043] The multi-layer boards are subjected to post-process;

[0044] The multiple standby multi-layer boards are distinguished and discarded.

[0045] The technical scheme of the embodiment of the present application provides a back drilling manufacturing method, through providing a plurality of standby multilayer boards, accidental errors of single detection can be reduced, and the reliability of back drilling depth calibration is improved. The signal layer of the to-be-back-drilled hole in the standby multilayer board is connected to form a loop through a lead and a via, the to-be-back-drilled hole of the standby multilayer board is over-drilled, the loop is opened after drilling through the signal layer, and the back drilling depth is recorded according to the real-time open point; and the final back drilling depth of the to-be-back-drilled hole of the multilayer board is determined through the back drilling depth when each to-be-back-drilled hole is drilled to open, and the drilling depth adjustment amount determined according to the sum of the preset residual stub length and the thickness of the signal layer. Through the technical scheme of the embodiment of the present application, the optimal back drilling depth of the to-be-back-drilled hole of the multilayer board can be effectively obtained, the precision control of the residual stub length is improved, and the quality of the PCB product is improved.

[0046] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent through the following description. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0048] Figure 1 is a flow chart of a back drilling manufacturing method provided by the embodiment of the present application;

[0049] Figure 2 is a structural schematic diagram of a standby multilayer board provided by the embodiment of the present application;

[0050] Figure 3 is a cross-sectional structural schematic diagram of a multilayer board after press bonding and electroplating provided by the embodiment of the present application;

[0051] Figure 4 is a cross-sectional structural schematic diagram of a standby multilayer board after press bonding and electroplating provided by the embodiment of the present application;

[0052] Figure 5 is a structural schematic diagram of a standby multilayer board after forming a solder ring provided by the embodiment of the present application;

[0053] Figure 6 is a cross-sectional structural schematic diagram of a standby multilayer board after forming a solder ring provided by the embodiment of the present application;

[0054] Figure 7is a structural schematic diagram of a back-drilling backplate device provided according to an embodiment of the present application;

[0055] Figure 8 is a structural schematic diagram of a back-drilling backplate device provided according to an embodiment of the present application; Figure 1 is a flowchart of S130 in the method;

[0056] Figure 9 is a structural schematic diagram of a back-drilling depth adjustment structure provided according to an embodiment of the present application;

[0057] Figure 10 is a flowchart of another back-drilling hole manufacturing method provided according to an embodiment of the present application;

[0058] Figure 11 is a flowchart of another back-drilling hole manufacturing method provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0059] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the present application.

[0060] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0061] Figure 1 is a flowchart of a back-drilling hole manufacturing method provided according to an embodiment of the present application. The present embodiment can be applied to manufacturing a back-drilling hole of a printed circuit board. The back-drilling hole manufacturing method can be executed by a back-drilling hole manufacturing device. As shown in the figure, the back-drilling hole manufacturing method comprises the following steps. Figure 1

[0062] S110, providing a multi-layer board and a plurality of spare multi-layer boards; the signal layer to be back-drilled in the spare multi-layer board is connected to form a loop through a lead and a via. ​

[0063] Specifically, according to the product design requirements, a multi-layer plate containing a core plate, a prepreg and a copper foil is prepared. The multi-layer plate is composed of a multi-layer copper-clad plate after lamination treatment. The copper-clad plate is the basis for forming a printed circuit board. The standby multi-layer plate uses the same base material, the same stacking structure and the same copper thickness parameters as the multi-layer plate. The number of standby multi-layer plates can be greater than or equal to two. In the signal layer corresponding to the back-drilling hole of the standby multi-layer plate, a lead is made by etching process to connect the signal layer copper foil and the inner wall metal layer of the via, forming a closed conductive loop. The loop conduction can be detected in advance by a multimeter.

[0064] Figure 2 is a structural schematic diagram of a standby multi-layer plate according to an embodiment of the present application. As shown in Figure 2 , it includes a signal layer 10 of a back-drilling hole in a standby multi-layer plate, a back-drilling hole 20 in a standby multi-layer plate, an independent via 30 in a standby multi-layer plate, and a lead 40 connecting the signal layer 10 of the back-drilling hole in the standby multi-layer plate and the via 30. The signal layer corresponding to all types of back-drilling holes on the standby multi-layer plate needs to additionally increase the lead 40 to connect the via 30 which is not back-drilled. The width of the lead 40 is greater than or equal to 3 mil and less than or equal to 6 mil, preventing the lead 40 from occupying too much area and increasing the residual copper rate, affecting the plate thickness consistency with the multi-layer plate. The lead 40 can connect the independent via 30 pad, or connect the large copper skin containing the via 30, but the lead 40 is not allowed to connect other back-drilling via pads, and it is also not allowed to be designed to drill through the layer, avoiding affecting the open-short circuit test of the loop formed by connecting the signal layer of the back-drilling hole in the standby multi-layer plate with the via through the lead.

[0065] S120, copper deposition and electroplating treatment is performed on the multi-layer plate and the plurality of standby multi-layer plates.

[0066] Figure 3 is a cross-sectional structural schematic diagram of a multi-layer plate after pressing and electroplating according to an embodiment of the present application. Figure 4 is a cross-sectional structural schematic diagram of a standby multi-layer plate after pressing and electroplating according to an embodiment of the present application. As shown in Figure 3 and Figure 4 , the multi-layer plate 100 and the standby multi-layer plate 200 after pressing and electroplating both include a back-drilling hole 20, a via 30 and a signal layer 10. The standby multi-layer plate 200 further includes a lead 40 connecting the signal layer 10 and the via 30.

[0067] In an optional embodiment of the present application, after S120, copper deposition and electroplating treatment is performed on the multi-layer plate and the plurality of standby multi-layer plates, it includes: forming a solder ring on both sides of the back-drilling hole of the plurality of standby multi-layer plates.

[0068] In the alternative embodiment of the present application, the welding ring is formed on both sides of the to-be-back-drilled holes of the plurality of spare multi-layer boards, comprising: performing pre-process and dry film pasting on the plurality of spare multi-layer boards; forming the welding ring on both sides of the to-be-back-drilled holes by exposure, development and etching.

[0069] Specifically, after the copper deposition and electroplating treatment of the multi-layer board and the plurality of spare multi-layer boards, and before the back drilling of the to-be-back-drilled holes of the spare multi-layer boards by the back drilling machine, the spare multi-layer boards are first distinguished from the multi-layer board and pre-processed. Specifically, the dry film is first pasted on the copper-clad plate, the dry film in the specific area is chemically reacted by exposure, the dry film in the unexposed part is removed by developing solution, and finally the copper layer without dry film protection is etched away by etching solution, thereby forming the welding ring on both sides of the to-be-back-drilled holes of the plurality of spare multi-layer boards. Figure 5 is a structural schematic diagram of the spare multi-layer board after forming the welding ring according to the embodiment of the present application. Figure 6 is a cross-sectional structural schematic diagram of the spare multi-layer board after forming the welding ring according to the embodiment of the present application. Figure 5 and Figure 6 As shown in the figures, the to-be-back-drilled hole 20 and the via hole 30 are included. The width of the welding ring 50 of the to-be-back-drilled hole 20 is controlled to be between 4-6 mil. Only the welding ring 50 is etched, and the via hole 30 and the copper skin at other positions are all reserved.

[0070] S130, back drilling the to-be-back-drilled holes of the spare multi-layer board by the back drilling machine, and recording the back drilling depth when the loop is detected to be open.

[0071] Specifically, by over-drilling the to-be-back-drilled holes of the spare multi-layer board, the loop is caused to be open after drilling through the signal layer, and then the back drilling depth is recorded according to the real-time open point. For example, the spare multi-layer board can be fixed on the back drilling machine, the coaxiality of the spare multi-layer board and the drill bit of the back drilling machine is adjusted, the probe of the open detection device is connected to the lead-out end of the loop, and the conduction threshold of the detection device is set. The back drilling machine is started, and the drill bit of the back drilling machine drills the to-be-back-drilled hole at a preset speed. In the process of drilling, the open detection device monitors the conduction state of the loop in real time. When the loop is detected to be open, the drilling is stopped, and the back drilling depth at this time is recorded.

[0072] In the alternative embodiment of the present application, the back drilling machine is provided with an open-short circuit detection module and a back drilling backing plate device; the open-short circuit detection module and the back drilling backing plate device are connected; and the back drilling backing plate device is connected with the welding ring and the via hole after electroplating.

[0073] Figure 7 is a structural schematic diagram of the back drilling backing plate device according to the embodiment of the present application. As shown in the figure, Figure 7As shown, the back drilling pad device is manufactured, and the back drilling pad device comprises a cavity 60, a first open short circuit probe 70 and a second open short circuit probe 80; the cavity 60 comprises a first surface 601 and a second surface 602 arranged oppositely. A plurality of windows 90 are arranged on the first surface 601. The window 90 can be the same size as the welding ring. The first open short circuit probe 70 is connected with the welding ring of the surface to be back drilled, and the second open short circuit probe 80 is connected with the via after electroplating; or, the first open short circuit probe 70 is connected with the via after electroplating, and the second open short circuit probe 80 is connected with the welding ring of the surface to be back drilled, which is not limited in the embodiment of the present application. In summary, the back drilling pad device is internally provided with movable first open short circuit probe 70 and second open short circuit probe 80, which are used in the back drilling process. One of the first open short circuit probe 70 and the second open short circuit probe 80 can be accurately moved to the welding ring of the hole to be back drilled and connected with the welding ring, and the other is connected with the via after electroplating to form a conduction loop. During the working process, the first open short circuit probe 70 can be connected with the via after electroplating and fixed, and the second open short circuit probe 80 is moved to the welding ring of the hole to be back drilled to form a loop, and then the back drilling is started. After the drill is lowered to the open circuit of the loop, the second open short circuit probe 80 is moved to the next hole to be back drilled, and the process is repeated until the back drilling is completed. An open short circuit detection module is arranged on the back drilling machine. The open short circuit detection module is connected with the back drilling pad device, which can control the back drilling tool to stop drilling when the open circuit is detected, and record the back drilling depth.

[0074] Figure 8 According to the embodiment of the present application Figure 1 The flowchart included in S130. Referring to Figure 8 S130, the hole to be back drilled of the standby multilayer board is back drilled by the back drilling machine, and the back drilling depth is recorded when the loop open circuit is detected, comprising:

[0075] S1301, the hole to be back drilled of the standby multilayer board is back drilled by the back drilling tool.

[0076] Specifically, the standby multilayer board can be fixed on the back drilling machine, and the standby multilayer board is adjusted to be coaxial with the drill bit of the back drilling tool; the first open short circuit probe is connected with the welding ring of the surface to be back drilled, and the second open short circuit probe is connected with the via after electroplating. Start the back drilling machine, and make the drill bit of the back drilling tool drill the hole to be back drilled at a preset speed.

[0077] S1302, the connection of the back drilling pad device with the welding ring and the via after electroplating is detected by the open short circuit detection module.

[0078] For example, the open-short circuit detection module outputs a constant low voltage and small current signal, such as 5V / 10mA, to the loop, and continuously monitors the resistance value or on-off state of the loop. When the resistance value of the loop suddenly increases from a stable low resistance value to a nearly infinite resistance value, it is determined that the signal layer in the loop has been cut off, causing the loop to be open.

[0079] S1303, when the open-short circuit detection module detects an open circuit, the back drilling depth is recorded and the back drilling is stopped.

[0080] Specifically, the back drilling depth is recorded when the open-short circuit detection module detects an open circuit, and the back drilling depth of each hole to be back drilled in each tool sequence is recorded when the open circuit is detected.

[0081] S140, according to the back drilling depth and the drilling depth adjustment, the final back drilling depth is determined; the drilling depth adjustment is the sum of the preset residual stub length and the thickness of the signal layer.

[0082] Specifically, according to the back drilling depth of the plurality of spare multi-layer boards, the residual stub length adjustment is inversely calculated in combination with the drilling depth adjustment, to obtain the final back drilling depth of each hole to be back drilled in the multi-layer board, i.e. the optimal actual drilling depth. Figure 9 is a back drilling depth adjustment structure diagram provided by an embodiment of the present application. As shown in Figure 9 the back drilling depth H, the signal layer thickness Y, the tool tip ineffective drilling depth h, and the back drilling tool diameter R obtained by the open circuit test. The multi-layer board 100 includes the final back drilling depth H1, the drilling depth adjustment Z, the preset residual stub length q, the signal layer thickness Y, and the back drilling tool diameter R. Therefore, it can be known that the drilling depth adjustment Z is equal to the sum of the preset residual stub length q and the signal layer thickness Y, and further that the final back drilling depth H1 after the back drilling depth adjustment is equal to the difference between the back drilling depth H and the drilling depth adjustment Z. The preset residual stub length q can be determined according to the residual stub length range required by the product.

[0083] The final back drilling depth of each hole to be back drilled in each spare multi-layer board can be determined through the above steps. In order to improve the determination accuracy of the final back drilling depth, the final back drilling depth of the multi-layer board can also be determined according to the back drilling depth of the plurality of spare multi-layer boards and the drilling depth adjustment.

[0084] In an optional embodiment of the present application, according to the back drilling depth and the drilling depth adjustment, the final back drilling depth is determined, which further includes: taking the average value of the maximum value and the minimum value of the final back drilling depth of the holes to be back drilled at the same position of the plurality of spare multi-layer boards as the final back drilling depth of each hole to be back drilled in the multi-layer board; or, according to the average value of the maximum value and the minimum value of the final back drilling depth of all holes to be back drilled in each tool sequence, the final back drilling depth of each tool sequence in the multi-layer board is determined.

[0085] Specifically, two methods can be included: (1) adjusting according to each to-be-back-drilled hole. According to the measurement results of the multiple spare multilayer boards, the drilling depth of each to-be-back-drilled hole in the multilayer board is adjusted separately without considering the order of the drill bit, the average value of the maximum value and the minimum value of the final back-drilling depth of the holes in the same position of the multiple spare multilayer boards is taken as the final back-drilling depth of each to-be-back-drilled hole in the multilayer board, and it can be detected and confirmed whether the residual stub length obtained after drilling according to the final back-drilling depth of each to-be-back-drilled hole in the multilayer board determined at this time is within the range of the required residual stub length of the product. (2) adjusting according to the order of the drill bit. According to the average value of the maximum value and the minimum value of the final back-drilling depth of all to-be-back-drilled holes of each drill bit order, the final back-drilling depth of each drill bit order in the multilayer board is determined, and it can be detected and confirmed whether the residual stub length obtained after drilling according to the final back-drilling depth of each drill bit order in the multilayer board determined at this time is within the range of the required residual stub length of the product.

[0086] S150, back drilling the multilayer board according to the final back-drilling depth to form a back-drilled hole.

[0087] Specifically, the final back-drilling depth of the to-be-back-drilled hole of the multilayer board is determined through the multiple spare multilayer boards. The back-drilled hole of the first multilayer board can be produced according to the final back-drilling depth, and after confirming that there is no abnormality, batch production can be carried out, thereby avoiding the risk of batch rejection and ensuring the consistency of batch production.

[0088] The technical scheme of the embodiment of the application provides a manufacturing method of a back-drilled hole, through which multiple spare multilayer boards are provided, accidental errors of single detection can be reduced, and the reliability of back-drilling depth calibration can be improved. The signal layer of the to-be-back-drilled hole in the spare multilayer board is connected to form a loop through a lead and a via, the to-be-back-drilled hole of the spare multilayer board is over-drilled, the loop is opened after the signal layer is drilled through, the back-drilling depth is recorded according to the real-time open point, the final back-drilling depth of the to-be-back-drilled hole of the multilayer board is determined through the back-drilling depth when each to-be-back-drilled hole is drilled through the open point and the drilling depth adjustment amount determined according to the sum of the preset residual stub length and the thickness of the signal layer. Through the technical scheme of the embodiment of the application, the optimal back-drilling depth of the to-be-back-drilled hole of the multilayer board can be effectively obtained, the precision control of the residual stub length is improved, and the quality of the PCB product is improved.

[0089] Figure 10 is a flowchart of another manufacturing method of a back-drilled hole provided by the embodiment of the application. As shown in Figure 10 , the manufacturing method of the back-drilled hole comprises:

[0090] S210, providing a multilayer board and multiple spare multilayer boards; the signal layer of the to-be-back-drilled hole in the spare multilayer board is connected to form a loop through a lead and a via.

[0091] S211, carrying out copper plating and electroplating treatment on the multilayer board and the multiple spare multilayer boards.

[0092] S212, back drilling the standby multi-layer board by the back drilling machine, and recording the back drilling depth when the loop is detected to be open.

[0093] S213, determining a preset stub length according to the stub length range.

[0094] In the optional embodiment of the present application, S213, determining the preset stub length according to the stub length range, comprises: determining the preset stub length according to half of the sum of the maximum stub length and the minimum stub length in the stub length range; or determining the preset stub length according to half of the sum of the maximum stub length and the minimum stub length in the stub length range plus a preset safety distance length.

[0095] Specifically, referring to Figure 9 , the stub length range can be that the product required stub length is between the minimum stub length M and the maximum stub length N, and then the preset stub length q can be determined according to (the minimum stub length M + the maximum stub length N) / 2.

[0096] Alternatively, a preset safety distance length can be additionally added, for example, the preset safety distance length is 1 mil or 2 mil, and then the preset stub length q can be determined according to (the minimum stub length M + the maximum stub length N) / 2 + 1 or (the minimum stub length M + the maximum stub length N) / 2 + 2.

[0097] S214, determining a drilling depth adjustment according to the sum of the preset stub length and the thickness of the signal layer.

[0098] Specifically, the drilling depth adjustment Z = the preset stub length q + the thickness Y of the signal layer.

[0099] S215, determining a final back drilling depth according to the difference between the back drilling depth and the drilling depth adjustment.

[0100] Specifically, the final back drilling depth H1 = the back drilling depth H - the drilling depth adjustment Z.

[0101] S216, back drilling the multi-layer board according to the final back drilling depth to form a back drilling hole.

[0102] S217, measuring the length of the stub to determine whether the length of the stub exceeds the stub length range.

[0103] Specifically, the final back drilling depth of the drill down to the back drilling hole of the multi-layer board is determined by the technical solution of the embodiment of the present application, and the drill down to the back drilling hole of the multi-layer board is performed according to the final back drilling depth, and then the length of the stub at this time can be measured by laser detection or other methods to determine whether the length of the stub exceeds the product required stub length range.

[0104] S218, when the length of the stub is within the stub length range, batch back drilling is performed on the to-be-back-drilled holes of the multi-layer board.

[0105] Specifically, when the length of the stub is within the stub length range, it indicates that the back drilling hole meets the product requirements, and then batch back drilling can be performed on the to-be-back-drilled holes of the multi-layer board.

[0106] S219, the multi-layer board is processed by a post-process.

[0107] Specifically, the post-process can include forming an outer layer circuit, automatically optically detecting the outer layer circuit, making a solder resist layer, silk printing characters, and surface treatment, forming a product, and quality detecting and packaging the formed product.

[0108] The main purpose of automatically optically detecting the outer layer circuit is to check whether the outer layer circuit has problems such as short circuit, open circuit, open circuit, insufficient line spacing, abnormal line width, and pad defects, to ensure the accuracy and integrity of the circuit, and to ensure the electrical performance and function of the PCB.

[0109] After automatically optically detecting the outer layer circuit, the solder resist layer is made to prevent solder from short-circuiting in places where it should not be soldered during the soldering process, and to protect the circuit from external environment, such as preventing oxidation and moisture, etc., to improve the reliability and service life of the PCB. Silk printing characters are printed on the PCB surface to print various marks, symbols and characters, etc. information, which is convenient for subsequent assembly, debugging, maintenance and identification. For example, mark the name, model, position of the element, and the version number and production batch of the PCB, etc. Surface treatment processes include but are not limited to chemical nickel plating, chemical silver plating and organic solderability preservative. The purpose of surface treatment is to improve the solderability, oxidation resistance and corrosion resistance of the PCB surface, to ensure good connection with electronic components during subsequent soldering and use.

[0110] After making the solder resist layer, silk printing characters and surface treatment, the PCB is processed into a specific shape according to the size and shape requirements of the final product, so that it can be accurately installed into electronic equipment. Appearance detection, electrical performance test and reliability test are performed on the formed product, and the product is packaged after confirming that there is no abnormality.

[0111] S220, distinguishing and scrapping a plurality of standby multi-layer boards.

[0112] Specifically, the standby multi-layer boards can be distinguished by physical marks on the standby multi-layer boards and scrapped.

[0113] Figure 11 is a flowchart of another back drilling hole making method according to an embodiment of the present application. As shown in Figure 11 the back drilling hole making method comprises:

[0114] S310, providing a copper-clad plate and a plurality of spare copper-clad plates.

[0115] Specifically, the copper-clad plate is a kind of plate-shaped material formed by impregnating electronic glass fiber cloth or other reinforcing materials with resin, covering one side or both sides with copper foil, and hot pressing. The copper-clad plate is the basis for forming a printed circuit board.

[0116] S320, drilling through holes in the multi-layer copper-clad plate and the plurality of spare copper-clad plates after the previous process and pressing treatment.

[0117] Specifically, the previous process can include: cutting, inner layer pattern making, inner layer etching, inner layer automated optical inspection (AOI). After inner layer AOI, it also includes pressing treatment. Specifically, the original copper-clad plate is cut to a size suitable for production to meet the specification requirements of the PCB design. The required circuit pattern is formed on the inner layer copper foil through etching process, which can include: first, adhere the photosensitive dry film to the copper-clad plate, expose the dry film to cause chemical reaction in the specified area, then remove the unexposed part of the dry film with developing solution, and finally etch away the copper layer without dry film protection with etching solution, thereby forming the inner layer circuit pattern. Inner layer etching is performed to remove unnecessary copper and retain the required circuit traces. Inner layer AOI is performed using optical scanning equipment to comprehensively detect the inner layer circuit, find short circuits, open circuits, gaps and other defects in the circuit, and ensure the quality of the inner layer circuit. The inner layer core plate, prepreg and outer layer copper foil are stacked together according to the design requirements, and the prepreg is melted and solidified under high temperature and pressure to bond the layers into one whole. Drilling equipment is applied to drill through holes in the multi-layer copper-clad plate after the previous process and pressing treatment.

[0118] S330, copper plating through holes and electroplating treatment of the plate surface.

[0119] Specifically, after drilling through holes, copper plating through holes and electroplating treatment of the plate surface are performed to deposit a uniform copper layer on the surface of the circuit board and the hole wall after the previous process, increase the thickness of the copper layer, and meet the requirements of subsequent manufacturing and electrical performance.

[0120] S340, back drilling the to-be-back-drilled holes of the spare multi-layer plate by a back drilling machine, and recording the back drilling depth when detecting that the loop is open.

[0121] S350, determining the final back drilling depth according to the back drilling depth and the drilling depth adjustment amount, the drilling depth adjustment amount being the sum of the preset residual stub length and the thickness of the signal layer.

[0122] S360, back drilling the multi-layer plate according to the final back drilling depth to form back drilled holes.

[0123] It should be understood that the various forms of flow illustrated above can be used to reorder, add or delete steps. For example, the steps described in the present application can be performed in parallel, in series, in a different order, or any combination thereof, as long as the desired results of the technical solutions of the present application can be achieved, which are not limited herein.

[0124] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for manufacturing a back-drilled hole, characterized in that, include: A multilayer board and multiple spare multilayer boards are provided; the signal layer of the spare multilayer board to be back-drilled is connected to vias through wires to form a loop. The multilayer board and the multiple spare multilayer boards are subjected to copper plating and electroplating treatment; The back-drilling machine is used to back-drill the holes to be back-drilled on the spare multilayer board. When the circuit is detected to be open, the back-drilling depth is recorded. The final back-drilling depth is determined based on the back-drilling depth and the drilling depth adjustment amount; the drilling depth adjustment amount is the sum of the preset residual pile length and the thickness of the signal layer. The multilayer board is back-drilled according to the final back-drilling depth to form back-drilled holes.

2. The method for manufacturing a back-drilled hole according to claim 1, characterized in that, After performing copper plating and electroplating on the multilayer board and the multiple spare multilayer boards, the process includes: Weld rings are formed on both sides of the back-drilled holes in the multiple spare multilayer boards.

3. The method for manufacturing a back-drilled hole according to claim 2, characterized in that, The back drilling machine platform is equipped with an open / short circuit detection module and a back drilling pad device. The open / short circuit detection module is connected to the back drill pad device; the back drill pad device is connected to the weld ring and the electroplated via respectively; The back-drilling process, which involves back-drilling the holes to be back-drilled on the spare multilayer board using a back-drilling machine and recording the back-drilling depth when an open circuit is detected, includes: The back-drilling holes in the spare multilayer board are drilled using a back-drilling tool. The connection between the back drill pad device and the weld ring and the electroplated via is detected by the open / short circuit detection module. When the open / short circuit detection module detects an open circuit, it controls the back drill bit to stop drilling and records the back drill depth.

4. The method for manufacturing a back-drilled hole according to claim 1, characterized in that, The final back-drilling depth is determined based on the back-drilling depth and the drilling depth adjustment amount, including: The preset residual pile length is determined based on the residual pile length range; The drilling depth adjustment amount is determined based on the sum of the preset residual pile length and the thickness of the signal layer; The final back-drilling depth is determined based on the difference between the back-drilling depth and the drilling depth adjustment amount.

5. The method for manufacturing a back-drilled hole according to claim 4, characterized in that, Determining the preset residual pile length based on the residual pile length range includes: The preset residual pile length is determined based on half of the sum of the maximum and minimum residual pile lengths within the residual pile length range; or; The preset residual pile length is determined by adding half the sum of the maximum and minimum residual pile lengths within the residual pile length range to a preset safety distance.

6. The method for manufacturing a back-drilled hole according to claim 1, characterized in that, Based on the final back-drilling depth, back-drill the holes to be back-drilled in the multilayer board, and after forming the back-drilled holes, the process includes: Measure the length of the remaining pile to determine whether the length of the remaining pile exceeds the range of remaining pile length; When the length of the residual pile is within the range of the residual pile length, the back drilling of the multilayer board is carried out in batches.

7. The method for manufacturing a back-drilled hole according to claim 2, characterized in that, The process of forming weld rings on both sides of the back-drilled holes in the multiple spare multilayer boards includes: Perform pre-processing and dry film application on multiple spare multilayer boards; Weld rings are formed on both sides of the hole to be drilled by exposure, development, and etching to remove the film.

8. The method for manufacturing a back-drilled hole according to claim 1, characterized in that, Provides multilayer boards and multiple spare multilayer boards, including: We provide copper-clad laminates and multiple spare copper-clad laminates; Drill holes in the multilayer copper-clad laminate and multiple spare copper-clad laminates after the preprocessing and lamination; The process of applying copper plating and electroplating to the multilayer board and the multiple spare multilayer boards includes: The vias are made transparent by copper plating, and the board surface is electroplated.

9. The method for manufacturing a back-drilled hole according to claim 1, characterized in that, Determining the final back-drilling depth based on the back-drilling depth and drilling depth adjustment amount also includes: The average of the maximum and minimum values ​​of the final back-drilling depths of the back-drilling holes at the same position in multiple spare multilayer boards is taken as the final back-drilling depth of each back-drilling hole in the multilayer board. or, The final back-drilling depth of each tool sequence in the multilayer board is the average of the maximum and minimum final back-drilling depths of all back-drilled holes for each tool sequence.

10. The method for manufacturing a back-drilled hole according to claim 6, characterized in that, When the length of the residual pile is within the range of the residual pile length, after batch back drilling of the back drill holes to be drilled in the multilayer board, the process includes: Post-processing is performed on the multilayer board; Distinguish and scrap multiple spare multilayer boards.

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