Method for processing back drilling of printed circuit board and printed circuit board

Abstract

The present invention discloses a method for processing back drilling holes of a printed circuit board and a printed circuit board. The processing method includes: dividing the back drilling area of ​​the printed circuit board into a plurality of sub-back drilling areas; determining the residual copper rate of each layer of copper foil in each sub-back drilling area; determining the thickness of each sub-back drilling area after glue filling and the depth coefficient of each sub-back drilling area; calculating the first theoretical back drilling depth of the back drilling position; and determining the second theoretical back drilling depth of the back drilling position in the sub-back drilling area; determining the actual back drilling depth of the back drilling position in the sub-back drilling area according to the second theoretical back drilling depth of the back drilling position in the sub-back drilling area and the preset residual copper amount; processing the back drilling hole according to the actual back drilling depth of the back drilling position in the sub-back drilling area; and inspecting the residual copper amount of the back drilling hole. The technical solution provided by the embodiment of the present invention improves the yield rate of residual copper of the back drilling hole.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit boards, and in particular to a method for processing back drilling holes of a printed circuit board and the printed circuit board. Background Art

[0002] With the continuous advancement of the information industry, digital signal transmission speeds are increasing, and frequencies are rising. Traditional printed circuit board designs can no longer meet the demands of these high-frequency circuits. Research on signal integrity transmission has become an increasingly critical core technology. When the frequency of circuit signals reaches a certain level, the excess copper plating in the unused vias of the printed circuit board acts like an antenna, radiating signals and interfering with other surrounding signals. In severe cases, this can affect the normal operation of the circuit system. The backdrilling process removes this excess copper plating, thereby eliminating this electromagnetic interference problem.

[0003] Backdrilling, a specialized drilling technique that controls hole depth, is widely used in high-frequency, high-speed products. Current backdrilling processes cannot completely eliminate residual copper. In circuit design, residual copper can cause reflections, scattering, and delays in signal transmission, compromising signal integrity. While PCB design techniques, such as laser drilling or changing the layer stacking sequence to move traces closer to the via stub ends, can be used to reduce residual copper, these methods are not always feasible from a manufacturing and cost perspective in many high-density PCBs and backplanes / midplanes. In such cases, the only option is to backdrill to remove the unused copper from the vias.

[0004] As printed circuit board products have increasingly higher requirements for signal integrity, the control of backdrilling residual copper during backdrilling processing has become increasingly stringent. Currently, the yield rate of backdrilled copper residue in backdrilling processes is not high and cannot meet the product requirements with strict backdrilling residual copper requirements. Summary of the Invention

[0005] The present invention provides a method for processing back drilling holes of a printed circuit board and a printed circuit board, so as to improve the yield rate of residual copper in the back drilling holes.

[0006] According to one aspect of the present invention, a method for processing back drilling holes in a printed circuit board is provided. The method for processing back drilling holes in a printed circuit board comprises:

[0007] Dividing the backdrill area of ​​the printed circuit board into a plurality of sub-backdrill areas;

[0008] Determine the residual copper rate of each layer of copper foil in each sub-backdrilling area;

[0009] Determine the thickness of each sub-back drill area after filling based on the residual copper rate of each layer of copper foil in each sub-back drill area;

[0010] Determine the depth coefficient of each sub-backdrilling area;

[0011] Calculating a first theoretical backdrilling depth of the backdrilling position according to the thickness between the drilling surface of the backdrilling position in each sub-backdrilling area and the target backdrilling layer;

[0012] Determine a second theoretical backdrill depth of the backdrill position in the sub-backdrill area according to the first theoretical backdrill depth of the backdrill position in the sub-backdrill area, the theoretical board thickness of the sub-backdrill area, the thickness of the sub-backdrill area after glue filling, and the depth coefficient of the sub-backdrill area;

[0013] determining an actual backdrill depth of the backdrill position in the sub-backdrill area according to a second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount;

[0014] Back drilling is performed according to the actual back drilling depth of the back drilling position within the sub-back drilling area;

[0015] Check the amount of residual copper in the back-drilled holes.

[0016] Optionally, dividing the backdrill area of ​​the printed circuit board into a plurality of sub-backdrill areas includes:

[0017] The backdrilling area of ​​the printed circuit board is divided into multiple square sub-areas of equal area.

[0018] Optionally, determining the residual copper rate of each layer of copper foil in each sub-backdrilling area includes:

[0019] Determine the area of ​​each layer of copper foil in each sub-backdrilling area;

[0020] The residual copper rate of each layer of copper foil in each sub-back drill area is determined according to the ratio of the area of ​​each layer of copper foil in each sub-back drill area to the area of ​​the corresponding sub-back drill area.

[0021] Optionally, determining the thickness of each sub-back-drilled area after glue filling based on the residual copper rate of each layer of copper foil in each sub-back-drilled area includes:

[0022] The thickness of each sub-back drilling area after filling is determined according to the sum of the products of the residual copper rate of each layer of copper foil in each sub-back drilling area and the thickness of the corresponding copper foil and the total thickness of the film layer between the copper foils.

[0023] Optionally, determining the depth coefficient of each sub-backdrilling area includes:

[0024] Determine the actual plate thickness after lamination in each sub-backdrilled area;

[0025] Determine the theoretical plate thickness of each sub-backdrilling area;

[0026] The depth coefficient of each sub-backdrilling region is determined according to the ratio of the actual plate thickness of each sub-backdrilling region after pressing to the theoretical plate thickness of each sub-backdrilling region.

[0027] Optionally, determining a second theoretical backdrill depth of the backdrill position in the sub-backdrill area according to the first theoretical backdrill depth of the backdrill position in the sub-backdrill area, the theoretical board thickness of the sub-backdrill area, the thickness of the sub-backdrill area after glue filling, and the depth coefficient of the sub-backdrill area includes:

[0028] The second theoretical backdrill depth of the backdrill position in the sub-backdrill area is determined according to the product of the ratio of the first theoretical backdrill depth of the backdrill position in the sub-backdrill area to the theoretical board thickness of the sub-backdrill area, the thickness of the sub-backdrill area after filling with glue, and the depth coefficient of the sub-backdrill area.

[0029] Optionally, determining the actual backdrill depth of the backdrill position in the sub-backdrill area according to the second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount includes:

[0030] An actual backdrill depth of the backdrill position in the sub-backdrill area is determined according to a difference between a second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount.

[0031] Optional inspection of the amount of copper remaining in the back drilled hole includes:

[0032] Check the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole;

[0033] Perform slice inspection on the amount of residual copper in the back-drilled hole.

[0034] Optionally, checking the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole includes:

[0035] The concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole is inspected by image detection equipment.

[0036] According to another aspect of the present invention, there is provided a printed circuit board, the printed circuit board comprising:

[0037] At least one back-drilled hole and a conductive hole, the back-drilled hole and the conductive hole are arranged in a one-to-one correspondence;

[0038] The back drilling method is processed by adopting the above-mentioned back drilling method of the printed circuit board.

[0039] The embodiment of the present invention first determines the backdrilling area of ​​the printed circuit board and then divides the backdrilling area into multiple sub-backdrilling areas. In subsequent backdrilling processing, all backdrilling positions can be completely covered for backdrilling processing. Then, a second theoretical back-drill depth of the back-drill position in the sub-back-drill area is determined based on the first theoretical back-drill depth of the back-drill position in the sub-back-drill area, the theoretical board thickness of the sub-back-drill area, the thickness of the sub-back-drill area after glue filling, and the depth coefficient of the sub-back-drill area. The actual back-drill depth of the back-drill position in the sub-back-drill area is determined based on the second theoretical back-drill depth of the back-drill position in the sub-back-drill area and the preset residual copper amount. The residual copper rate of each layer of copper foil in each sub-back-drill area determines the thickness of each sub-back-drill area after glue filling. The actual back-drill depth determined by the above technical solution is specific to each sub-back-drill area, taking into account the influence of the residual copper rate of each layer of copper foil, the influence of glue filling in the sub-back-drill area on the thickness, the influence of the depth coefficient of each sub-back-drill area, and the preset residual copper amount. This improves the accuracy of the actual back-drill depth ultimately determined for the back-drill position in a particular sub-back-drill area, ensuring that the residual copper amount of the back-drilled hole is within a control range, thereby improving the residual copper yield of the back-drilled hole. Finally, back-drilling is performed according to the actual back-drilling depth of the back-drilling position within the sub-back-drilling area; and the amount of residual copper in the back-drilled holes is inspected to ensure that the amount of residual copper in the back-drilled holes is within the control range, thereby improving the back-drilling residual copper capacity and reducing the number of times the back-drilled holes need to be reworked and scrapped.

[0040] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 This is a flow chart of a method for processing back drilling of a printed circuit board according to an embodiment of the present invention;

[0043] Figure 2 1 is a schematic diagram of a design for processing a backdrill hole in a sub-backdrill area of ​​a printed circuit board according to an embodiment of the present invention;

[0044] Figure 3 1 is a schematic diagram of dividing a square sub-area of ​​a printed circuit board according to an embodiment of the present invention;

[0045] Figure 4 yes Figure 1 The method flow chart included in S120;

[0046] Figure 5 yes Figure 1 The method flow chart included in S140;

[0047] Figure 6 yes Figure 1 Flowchart of the method included in S190. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0049] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0050] The embodiment of the present invention provides a method for processing back drilling of a printed circuit board. Figure 1 is a flowchart of a method for processing back drilling of a printed circuit board according to an embodiment of the present invention, with reference to Figure 1 , the back drilling processing methods of printed circuit boards include:

[0051] S110: Divide the backdrilling area of ​​the printed circuit board into a plurality of sub-backdrilling areas.

[0052] The shape and size of the sub-backdrilling area can be designed based on actual needs. For example, the sub-backdrilling area can be rectangular, square, etc., and this is not limited in the present embodiment. In this embodiment, the backdrilling area of ​​the printed circuit board is first determined, and then the backdrilling area is divided into multiple sub-backdrilling areas. Subsequently, the backdrilling process is performed to achieve backdrilling of all backdrilling locations.

[0053] S120: Determine the residual copper rate of each layer of copper foil in each sub-backdrilling area.

[0054] Specifically, due to the differences in the actual circuit routing in each sub-backdrilled area, each layer of copper foil in each sub-backdrilled area may contain copper or not, resulting in different residual copper rates for each layer of copper foil in different sub-backdrilled areas. Therefore, embodiments of the present invention calculate the residual copper rate of each layer of copper foil in each sub-backdrilled area based on the area of ​​the copper-containing position in the sub-backdrilled area and the area of ​​the sub-backdrilled area.

[0055] S130 , determining the thickness of each sub-back-drilling region after filling with glue according to the residual copper rate of each layer of copper foil in each sub-back-drilling region.

[0056] Specifically, the thickness of each sub-backdrill area after filling with glue needs to be determined based on the specific structure of the printed circuit board, the thickness of each copper foil layer in each sub-backdrill area, the residual copper rate of each copper foil layer, and the thickness of the glue layer. The glue layer can be made of prepreg (PP).

[0057] S140: Determine the depth coefficient of each sub-backdrilling area.

[0058] Specifically, the depth coefficient of each sub-backdrilling region may be determined by measuring and calculating the actual plate thickness of each sub-backdrilling region after lamination and the theoretical plate thickness of each sub-backdrilling region.

[0059] S150 , calculating a first theoretical backdrilling depth of the backdrilling position according to the thickness between the drilling surface of the backdrilling position in each sub-backdrilling area and the target backdrilling layer.

[0060] For example, Figure 2 This is a schematic diagram of a backdrilling process for a sub-backdrilling area of ​​a printed circuit board according to an embodiment of the present invention. Figure 2The copper foil of the printed circuit board includes layer 1, layer 2, layer 3, layer 4, layer 5, layer 6, layer 7 and layer 8. Among them, layer 1 and layer 8 are outer copper foils. The remaining copper foils are inner copper foils. Layer 2 and layer 3 are located on two opposite surfaces of the inner layer board (core layer). Layer 4 and layer 5 are located on two opposite surfaces of the inner layer board (core layer). Layer 6 and layer 7 are located on two opposite surfaces of the inner layer board (core layer). There is a prepreg (PP) between layer 1 and layer 2, a prepreg (PP) between layer 3 and layer 4, a prepreg (PP) between layer 5 and layer 6, and a prepreg (PP) between layer 7 and layer 8. The thickness of each film layer of the printed circuit board from layer 1 to layer 8 is: 0.6mil, 3mil, 1.2mil, 7mil, 1.2mil, 5mil, 2.4mil, 7mil, 2.4mil, 5mil, 1.2mil, 7mil, 1.2mil, 3mil, and 0.6mil.

[0061] The sub-backdrilling area shown in the printed circuit board includes conductive hole 1, conductive hole 2, backdrilled hole 1 and backdrilled hole 2. Backdrilled hole 1 and conductive hole 1 are set correspondingly, and backdrilled hole 2 and conductive hole 2 are set correspondingly. The target backdrilling layer of backdrilled hole 1 is layer 5, and the target backdrilling layer of backdrilled hole 2 is layer 7. The embodiment of the present invention takes the target backdrilling layers as layer 5 and layer 7 as an example to explain in detail the calculation of the first theoretical backdrilling depth, which is specifically described as follows: wherein, backdrilled hole 1 selects layer 1 as the drilling surface of the backdrilling position in the sub-backdrilling area, and layer 7 is the target backdrilling layer, then the first theoretical backdrilling depth a of backdrilled hole 1 is the sum of the copper foil thickness from layer 1 to layer 6 and the thickness of each intermediate filling layer, that is, the first theoretical backdrilling depth a of backdrilled hole 1

[0062] a=0.6mil+3mil+1.2mil+7mil+1.2mil+5mil+2.4mil+7mil+2.4mil+5mil+1.2mil+

[0063] 7mil=43mil; and backdrill hole 2 selects layer1 as the drilling surface of the backdrill position in the sub-backdrill area, and layer5 is the target backdrill layer. Then the first theoretical backdrill depth b of backdrill hole 2 is the sum of the copper foil thickness from layer1 to layer5 and the thickness of each intermediate fill layer, that is, the first theoretical backdrill depth b of backdrill hole 2=0.6mil+3mil+1.2mil+7mil+1.2mil+5mil+2.4mil+7mil=27.4mil.

[0064] S160: Determine a second theoretical backdrill depth of the backdrill position in the sub-backdrill area according to the first theoretical backdrill depth of the backdrill position in the sub-backdrill area, the theoretical board thickness of the sub-backdrill area, the thickness of the sub-backdrill area after glue filling, and the depth coefficient of the sub-backdrill area.

[0065] The theoretical plate thickness of the sub-backdrilling area can be understood as the designed median value of the plate thickness of each sub-backdrilling area, that is, the average value of the plate thickness of each sub-backdrilling area. For example, Figure 2 As shown, Figure 2 Theoretical board thickness of the sub-backdrilled area is shown

[0066] =0.6mil+3mil+1.2mil+7mil+1.2mil+5mil+2.4mil+7mil+2.4mil+5mil+1.2mil+

[0067] 7mil+1.2mil+3mil+0.6mil=47.8mil.

[0068] Specifically, the second theoretical backdrill depth of the backdrill position in the sub-backdrill area can be determined based on the ratio of the first theoretical backdrill depth of the backdrill position in the sub-backdrill area to the theoretical board thickness of the sub-backdrill area, and the product of the thickness of the sub-backdrill area after filling with glue and the depth coefficient of the sub-backdrill area.

[0069] S170: Determine an actual backdrill depth of the backdrill position in the sub-backdrill area according to a second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount.

[0070] Specifically, the calculated second theoretical back-drill depth of the back-drill position in the sub-back-drill area is the ideal state in which the back-drill just drills into the target layer, but a certain space must actually be reserved to avoid mistakes during back-drilling. The certain space reserved during actual back-drilling is the preset residual copper amount, so that the residual copper amount of the back-drilled hole is within the control range, thereby improving the yield of the residual copper of the back-drilled hole. Among them, the specific length of the preset residual copper amount can be designed according to the specific situation. For example, when the control of the back-drilling residual copper amount during back-drilling is between 2-7mil, the length of the preset residual copper can be selected as 4.5mil. Therefore, the actual back-drill depth of the back-drill position in the sub-back-drill area can be obtained by subtracting the second theoretical back-drill depth of the back-drill position in the sub-back-drill area from the preset residual copper amount. For example, as Figure 2 As shown, the actual length of the remaining copper corresponding to the back-drilled hole 1 is a1, and the actual length of the remaining copper corresponding to the back-drilled hole 2 is b1.

[0071] S180 , back-drilling is performed according to the actual back-drilling depth of the back-drilling position in the sub-back-drilling area.

[0072] S190. Inspect the amount of residual copper in the back-drilled holes.

[0073] The inspection contents include the concentricity inspection of the back-drilled hole and the conductive hole corresponding to the back-drilled hole, and the slicing inspection of the residual copper amount of the back-drilled hole.

[0074] The embodiment of the present invention first determines the backdrilling area of ​​the printed circuit board and then divides the backdrilling area into multiple sub-backdrilling areas. In subsequent backdrilling processing, backdrilling can be performed on all backdrilling positions. Then, a second theoretical back-drill depth of the back-drill position in the sub-back-drill area is determined based on the first theoretical back-drill depth of the back-drill position in the sub-back-drill area, the theoretical board thickness of the sub-back-drill area, the thickness of the sub-back-drill area after glue filling, and the depth coefficient of the sub-back-drill area. The actual back-drill depth of the back-drill position in the sub-back-drill area is determined based on the second theoretical back-drill depth of the back-drill position in the sub-back-drill area and the preset residual copper amount. The residual copper rate of each layer of copper foil in each sub-back-drill area determines the thickness of each sub-back-drill area after glue filling. The actual back-drill depth determined by the above technical solution is specific to each sub-back-drill area, taking into account the influence of the residual copper rate of each layer of copper foil, the influence of glue filling in the sub-back-drill area on the thickness, the influence of the depth coefficient of each sub-back-drill area, and the preset residual copper amount. This improves the accuracy of the actual back-drill depth ultimately determined for the back-drill position in a particular sub-back-drill area, ensuring that the residual copper amount of the back-drilled hole is within a control range, thereby improving the residual copper yield of the back-drilled hole. Finally, back-drilling is performed according to the actual back-drilling depth of the back-drilling position within the sub-back-drilling area; and the amount of residual copper in the back-drilled holes is inspected to ensure that the amount of residual copper in the back-drilled holes is within the control range, thereby improving the back-drilling residual copper capacity and reducing the number of times the back-drilled holes need to be reworked and scrapped.

[0075] Optionally, based on the above technical solution, S110 divides the backdrilling area of ​​the printed circuit board into a plurality of sub-backdrilling areas including:

[0076] The backdrilling area of ​​the printed circuit board is divided into multiple square sub-areas of equal area.

[0077] The square sub-area is the sub-backdrilling area. Specifically, the size of the square sub-area can be determined according to actual conditions. For example, Figure 3 This is a schematic diagram of dividing a square sub-area of ​​a printed circuit board according to an embodiment of the present invention, with reference to Figure 3 The backdrill area of ​​the printed circuit board can be divided into 100 equal-sized square sub-areas, each measuring 0.5 by 0.5 inches. The backdrill area is divided into multiple sub-areas, and subsequent backdrilling is performed to achieve backdrilling of all backdrill locations. Figure 3 100 positions are shown, namely position 1 to position 100, and each position corresponds to a square sub-area, ie, a sub-backdrilling area.

[0078] Figure 4 yes Figure 1 The method flow chart included in S120 is optional, refer to Figure 4 Based on the above technical solution, S120 determines the residual copper rate of each layer of copper foil in each sub-backdrilling area, including:

[0079] S1201. Determine the area of ​​each layer of copper foil in each sub-backdrilling area.

[0080] S1202 : Determine the residual copper rate of each layer of copper foil in each sub-back-drilling area according to the ratio of the area of ​​each layer of copper foil in each sub-back-drilling area to the area of ​​the corresponding sub-back-drilling area.

[0081] Specifically, due to the different actual routing of the circuits in each sub-backdrilling area, the area of ​​each layer of copper foil in each sub-backdrilling area can be determined according to the actual routing of each sub-backdrilling area, and finally the residual copper rate of each layer of copper foil in each sub-backdrilling area is determined according to the ratio of the area of ​​each layer of copper foil in each sub-backdrilling area to the area of ​​the corresponding sub-backdrilling area. For example, in the embodiment of the present invention, Figure 3 Taking position 1 in the example, the residual copper rate of each layer of copper foil from layer 1 to layer 8 is calculated based on the proportion of the area of ​​each layer of copper foil in the sub-backdrilling area corresponding to position 1 in the entire square. Figure 2 Back drilled via 1 and back drilled via 2 are shown located at Figure 3 One of the sub-backdrilling areas is in position 1. Table 1 lists the residual copper rates of each layer of copper foil in the sub-backdrilling area (position 1).

[0082] Table 1 Residual copper rate of each layer of copper foil in the sub-backdrilling area (position 1)

[0083] Location Area Layer Residual copper rate Position 1 Layer 1 100％ Position 1 Layer 2 80％ Position 1 Layer 3 80％ Position 1 Layer 4 45％ Position 1 Layer 5 45％ Position 1 Layer 6 80％ Position 1 Layer7 80％ Position 1 Layer8 100％

[0084] Optionally, based on the above technical solution, S130 determines the thickness of each sub-backdrilling area after filling with glue according to the residual copper rate of each layer of copper foil in each sub-backdrilling area, including:

[0085] The thickness of each sub-back drilling area after filling is determined according to the sum of the products of the residual copper rate of each layer of copper foil in each sub-back drilling area and the thickness of the corresponding copper foil and the total thickness of the film layer between the copper foils.

[0086] set up Figure 2 Back drilled via 1 and back drilled via 2 are shown located at Figure 3 One of the sub-backdrilling areas is in position 1. For example, the thickness of the sub-backdrilling area (position 1) after filling is

[0087] =0.6*100%+3+1.2*80%+7+1.2*80%+5+2.4*45%+7+2.4*45%+5+1.2*80%+7+1.2*80%+3+0.6*100%=44.2mil.

[0088] Figure 5 yes Figure 1 The method flow chart included in S140 is optional, refer to Figure 5 Based on the above technical solution, S140 determines the depth coefficient of each sub-backdrilling area including:

[0089] S1401. Determine the actual plate thickness of each sub-backdrilled area after pressing.

[0090] S1402: Determine the theoretical plate thickness of each sub-backdrilling area.

[0091] S1403 : Determine a depth coefficient of each sub-backdrilling region according to a ratio of the actual plate thickness of each sub-backdrilling region after lamination to the theoretical plate thickness of each sub-backdrilling region.

[0092] Specifically, since it is impossible to cover all positions when measuring the actual plate thickness of each sub-back-drilled area after pressing, a nine-point measurement method can be used, that is, nine test points are selected in each sub-back-drilled area by an automatic plate thickness measurement device, and the test values ​​of the nine test points are averaged to finally determine the actual plate thickness of each sub-back-drilled area after pressing. For example, Figure 3 For example, the actual board thickness of the sub-back drill area (position 1) after lamination is 45.5 mil. Figure 2 As shown, Figure 3The theoretical board thickness of the sub-back drill area (position 1) is the sum of the thickness of each layer of copper foil and the thickness of each layer of filler layer, that is, the theoretical board thickness of the sub-back drill area (position 1)

[0093] =0.6mil+3mil+1.2mil+7mil+1.2mil+5mil+2.4mil+7mil+2.4mil+5mil+1.2mil+

[0094] 7mil+1.2mil+3mil+0.6mil=47.8mil, then the depth coefficient of position 1 is the ratio of the actual plate thickness at position 1 after pressing to the theoretical plate thickness at position 1, that is, the depth coefficient of position 1 is 45.5mil / 47.8mil=0.95.

[0095] Optionally, based on the above technical solution, S160 determines the second theoretical backdrill depth of the backdrill position in the sub-backdrill area according to the first theoretical backdrill depth of the backdrill position in the sub-backdrill area, the theoretical board thickness of the sub-backdrill area, the thickness of the sub-backdrill area after glue filling, and the depth coefficient of the sub-backdrill area, including:

[0096] The second theoretical backdrill depth of the backdrill position in the sub-backdrill area is determined according to the product of the ratio of the first theoretical backdrill depth of the backdrill position in the sub-backdrill area to the theoretical board thickness of the sub-backdrill area, the thickness of the sub-backdrill area after filling with glue, and the depth coefficient of the sub-backdrill area.

[0097] Specifically, the second theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area can be determined according to the ratio of the first theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area to the theoretical board thickness of the sub-backdrilling area, and the product of the thickness of the sub-backdrilling area after filling with glue and the depth coefficient of the sub-backdrilling area. For example, Figure 2 Taking backdrill hole 1 and backdrill hole 2 in the example, assuming that backdrill hole 1 is in position 1, the first theoretical backdrill depth of backdrill hole 1 is determined to be 43 mil according to S150, the theoretical board thickness of the sub-backdrill area (position 1) is 47.8 mil, the thickness of the sub-backdrill area (position 1) after filling with glue is determined to be 44.2 mil according to S130, and the depth coefficient of the sub-backdrill area (position 1) is determined to be 0.95 according to S1401-S1403. Then, the second theoretical backdrill depth of backdrill hole 1 in the sub-backdrill area (position 1) = 43 mil / 47.8 mil*(44.2 mil*0.95) = 37.77 mil;

[0098] Assuming that back-drilled hole 2 is also in position 1, the first theoretical back-drilling depth of back-drilled hole 2 is determined to be 27.4 mil according to S150, the theoretical board thickness of the sub-back-drilled area (position 1) is 47.8 mil, the thickness of the sub-back-drilled area (position 1) after filling with glue is determined to be 44.2 mil according to S130, and the depth coefficient of the sub-back-drilled area (position 1) is determined to be 0.95 according to S1401-S1403, then the second theoretical back-drilling depth of back-drilled hole 2 in the sub-back-drilled area (position 1) = 27.4 mil / 47.8 mil*(44.2 mil*0.95) = 24.07 mil.

[0099] Optionally, S170 determines the actual backdrill depth of the backdrill position in the sub-backdrill area according to the second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount, including:

[0100] An actual backdrill depth of the backdrill position in the sub-backdrill area is determined according to a difference between a second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount.

[0101] Among them, the preset residual copper amount can be set according to the back drilling residual copper control range of 2-7mil. During processing, the middle value of the back drilling residual copper control range of 4.5mil is taken. The preset residual copper amount takes the middle value during actual processing to ensure that the actual back drilling deviation can be within the back drilling residual copper control range of 2-7mil. Then the actual back drilling depth of the back drilling hole 1 in position 1 = 37.77mil-4.5mil=33.27mil.

[0102] Table 2 Thickness, depth coefficient, second theoretical backdrilling depth, and actual backdrilling depth of each sub-backdrilling area after filling with glue for backdrilled holes at 8 different locations

[0103]

[0104] Table 2 lists the thickness, depth coefficient, second theoretical backdrill depth and actual backdrill depth of each sub-backdrill area after filling with glue for backdrill holes at 8 different locations. Among them, the difference between the second theoretical backdrill depth of the backdrill holes at 8 different locations and the preset residual copper amount (4.5mil) is the actual backdrill depth. It should be noted that the backdrill 1-1 at position 1 in Table 2 is Figure 2 Back drill hole 1 in.

[0105] Figure 6 yes Figure 1 The method flow chart included in S190 is optional, refer to Figure 6 , S190 inspection of the residual copper content of back-drilled holes includes:

[0106] S1901. Inspect the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole.

[0107] S1902. Perform a slice test on the amount of residual copper in the back-drilled hole.

[0108] Specifically, the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole can be tested first. On the premise of ensuring that the concentricity test meets the requirements, the amount of residual copper in the back-drilled hole can be sliced ​​and tested to confirm whether the length of the back-drilled residual copper meets the back-drilled residual copper control range.

[0109] Table 3 Concentricity test results and residual copper slice test results corresponding to each back-drilled hole in Table 2

[0110] Back drilling name Concentricity test results Residual copper slice Back Drill 1-1 OK 5mil Back drilling 1-2 OK 3.5mil Backdrill 1-3 OK 4mil Backdrill 1-4 OK 5mil Backdrill 2-1 OK 3mil Back Drill 2-2 OK 5.5mil Backdrill 2-3 OK 6mil Backdrill 2-4 OK 5mil

[0111] It should be noted that in Table 3, the concentricity test results corresponding to each back-drilled hole are obtained by testing the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole using the Eagle Eye device.

[0112] Optionally, checking the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole includes:

[0113] The concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole is inspected by image detection equipment.

[0114] For example, the image detection device may be an Eagle Eye device. Specifically, the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole is inspected by an image detection device such as an Eagle Eye device, and the detection result has high accuracy.

[0115] An embodiment of the present invention provides a printed circuit board, which includes: at least one back-drilled hole and a conductive hole, and the back-drilled hole and the conductive hole are arranged in a one-to-one correspondence; the back-drilled hole is processed by the back-drilled hole processing method of the printed circuit board described in any of the above embodiments.

[0116] Exemplary, reference Figure 2 , taking backdrilled hole 1 corresponding to conductive hole 1 and backdrilled hole 2 corresponding to conductive hole 2 as examples, the specific description is as follows:

[0117] First, the backdrilling area of ​​the PCB is divided into multiple sub-areas. Then, the conductive vias to be processed, namely, via 1 and via 2, are selected. For vias 1 and 2 within the same backdrilling area, the residual copper ratio of each layer of copper foil within the backdrilling area is determined. Based on this residual copper ratio, the thickness of the backdrilled sub-area after filleting is determined, along with the depth coefficient of the sub-area. Since layer 1 is selected as the drilling entry point within the backdrilling sub-area and layer 7 is the target backdrilling layer, the theoretical backdrilling depth a for backdrilling via 1 is the sum of the copper foil thicknesses from layers 1 to 6 and the thickness of the intermediate fillet layers. For backdrilling via 2, layer 1 is selected as the drilling entry point within the backdrilling sub-area and layer 5 is the target backdrilling layer. Therefore, the theoretical backdrilling depth b for backdrilling via 2 is the sum of the copper foil thicknesses from layers 1 to 5 and the thickness of the intermediate fillet layers. After determining the first theoretical backdrill depths of backdrill holes 1 and 2, the second theoretical backdrill depths of the backdrill positions within the sub-backdrill area are determined based on the first theoretical backdrill depths of the backdrill positions within the sub-backdrill area, the theoretical board thickness of the sub-backdrill area, the thickness of the sub-backdrill area after glue filling, and the depth coefficient of the sub-backdrill area, namely, the second theoretical backdrill depth of backdrill hole 1 and the second theoretical backdrill depth of backdrill hole 2. The actual backdrill depths of the backdrill positions within the sub-backdrill area are then determined based on the second theoretical backdrill depths of backdrill holes 1 and 2 and a preset amount of residual copper. Finally, backdrilling is performed according to the actual backdrill depths of backdrill holes 1 and 2, resulting in the printed circuit board provided by the embodiment of the present invention.

[0118] The printed circuit board provided by the embodiment of the present invention first determines the backdrill area of ​​the printed circuit board and then divides the backdrill area into multiple sub-backdrill areas. When performing subsequent backdrilling processing, all backdrill positions can be completely covered for backdrilling processing. Then, a second theoretical back-drill depth of the back-drill position in the sub-back-drill area is determined based on the first theoretical back-drill depth of the back-drill position in the sub-back-drill area, the theoretical board thickness of the sub-back-drill area, the thickness of the sub-back-drill area after glue filling, and the depth coefficient of the sub-back-drill area. The actual back-drill depth of the back-drill position in the sub-back-drill area is determined based on the second theoretical back-drill depth of the back-drill position in the sub-back-drill area and a preset residual copper amount. The residual copper rate of each layer of copper foil in each sub-back-drill area determines the thickness of each sub-back-drill area after glue filling. The actual back-drill depth determined by this processing method is specific to each sub-back-drill area, taking into account the influence of the residual copper rate of each layer of copper foil, the influence of glue filling in the sub-back-drill area on the thickness, the influence of the depth coefficient of each sub-back-drill area, and the preset residual copper amount. This improves the accuracy of the actual back-drill depth ultimately determined for the back-drill position in a particular sub-back-drill area, ensuring that the residual copper amount of the back-drilled hole is within a control range, thereby improving the residual copper yield of the back-drilled holes in the printed circuit board. Finally, back-drilling is performed according to the actual back-drilling depth of the back-drilling position within the sub-back-drilling area to form the printed circuit board provided by the embodiment of the present invention; and the amount of residual copper in the back-drilled holes of the printed circuit board is inspected to ensure that the amount of residual copper in the back-drilled holes is within the control range, thereby improving the back-drilling residual copper capability and reducing the number of times the back-drilled holes need to be reworked and scrapped.

[0119] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0120] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for processing back drilling of a printed circuit board, characterized in that: include: Dividing the backdrill area of ​​the printed circuit board into a plurality of sub-backdrill areas; Determine the residual copper rate of each layer of copper foil in each sub-backdrilling area; Determine the thickness of each sub-back drill area after filling based on the residual copper rate of each layer of copper foil in each sub-back drill area; Determine the depth coefficient of each sub-backdrilling area; Calculating a first theoretical backdrilling depth of the backdrilling position according to the thickness between the drilling surface of the backdrilling position in each sub-backdrilling area and the target backdrilling layer; determining a second theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area according to the first theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area, the theoretical board thickness of the sub-backdrilling area, the thickness of the sub-backdrilling area after glue filling, and the depth coefficient of the sub-backdrilling area; determining an actual backdrill depth of the backdrill position in the sub-backdrill area according to a second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount; Back drilling is performed according to the actual back drilling depth of the back drilling position in the sub-back drilling area; The amount of residual copper in the back-drilled holes is inspected.

2. The method for processing back drilling of a printed circuit board according to claim 1, characterized in that: Dividing the backdrill area of ​​a printed circuit board into multiple sub-backdrill areas includes: The backdrilling area of ​​the printed circuit board is divided into multiple square sub-areas of equal area.

3. The method for processing back drilling of a printed circuit board according to claim 1, characterized in that: Determining the residual copper rate of each layer of copper foil in each sub-backdrilling area includes: Determine the area of ​​each layer of copper foil in each sub-backdrilling area; The residual copper rate of each layer of copper foil in each sub-back drill area is determined according to the ratio of the area of ​​each layer of copper foil in each sub-back drill area to the area of ​​the corresponding sub-back drill area.

4. The method for processing back drilling of a printed circuit board according to claim 1, wherein: Based on the residual copper rate of each layer of copper foil in each sub-backdrilling area, the thickness of each sub-backdrilling area after filling is determined, including: The thickness of each sub-back drilling area after filling is determined according to the sum of the products of the residual copper rate of each layer of copper foil in each sub-back drilling area and the thickness of the corresponding copper foil and the total thickness of the film layer between the copper foils.

5. The method for processing back drilling of a printed circuit board according to claim 1, characterized in that: The depth coefficients for determining each sub-backdrilling area include: Determine the actual plate thickness after lamination in each sub-backdrilled area; Determine the theoretical plate thickness of each sub-backdrilling area; The depth coefficient of each sub-backdrilling region is determined according to the ratio of the actual plate thickness of each sub-backdrilling region after pressing to the theoretical plate thickness of each sub-backdrilling region.

6. The method for processing back drilling of a printed circuit board according to claim 1, wherein: Determining a second theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area according to the first theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area, the theoretical board thickness of the sub-backdrilling area, the thickness of the sub-backdrilling area after glue filling, and the depth coefficient of the sub-backdrilling area includes: The second theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area is determined according to the product of the ratio of the first theoretical backdrilling depth of the backdrilling position in the sub-backdrilling area to the theoretical board thickness of the sub-backdrilling area, the thickness of the sub-backdrilling area after filling with glue, and the depth coefficient of the sub-backdrilling area.

7. The method for processing back drilling of a printed circuit board according to claim 1 or 6, characterized in that: Determining an actual backdrill depth of the backdrill position in the sub-backdrill area according to a second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount includes: An actual backdrill depth of the backdrill position in the sub-backdrill area is determined according to a difference between a second theoretical backdrill depth of the backdrill position in the sub-backdrill area and a preset residual copper amount.

8. The method for processing back drilling of a printed circuit board according to claim 1, characterized in that: The inspection of the residual copper amount of the back-drilled hole includes: Checking the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole; The amount of residual copper in the back-drilled hole is subjected to a slice inspection.

9. The method for processing back drilling of a printed circuit board according to claim 8, characterized in that: Checking the concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole includes: The concentricity of the back-drilled hole and the conductive hole corresponding to the back-drilled hole is inspected by an image detection device.

10. A printed circuit board, characterized in that: include: at least one back-drilled hole and a conductive hole, wherein the back-drilled hole and the conductive hole are arranged in a one-to-one correspondence; The back drilling method is manufactured by adopting the back drilling method of the printed circuit board described in any one of claims 1-9.

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