CN113840479B - Back drilling depth determination method, back drilling method and drilling system - Google Patents
Back drilling depth determination method, back drilling method and drilling system Download PDFInfo
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- CN113840479B CN113840479B CN202111427228.5A CN202111427228A CN113840479B CN 113840479 B CN113840479 B CN 113840479B CN 202111427228 A CN202111427228 A CN 202111427228A CN 113840479 B CN113840479 B CN 113840479B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
- H05K3/42—Plated through-holes or plated via connections
- H05K3/429—Plated through-holes specially for multilayer circuits, e.g. having connections to inner circuit layers
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/0011—Working of insulating substrates or insulating layers
- H05K3/0044—Mechanical working of the substrate, e.g. drilling or punching
- H05K3/0047—Drilling of holes
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Abstract
The invention relates to the technical field of printed circuit board manufacturing, and discloses a back drilling depth determination method, a back drilling method and a drilling system, wherein the back drilling depth determination method comprises the following steps: determining a first intermediate layer and a second intermediate layer, wherein a back drilling target layer is a layer to be back drilled of the PCB; acquiring the actual thickness between the back drilling starting layer and the first intermediate layer and the actual thickness between the first intermediate layer and the second intermediate layer; calculating the relative depth of the back drilling target layer relative to the first intermediate layer according to the theoretical thickness between the first intermediate layer and the second intermediate layer, the theoretical thickness between the back drilling target layer and the first intermediate layer and the actual thickness between the first intermediate layer and the second intermediate layer; the actual thickness between the back-drilling initiation layer and the first intermediate layer, and the relative depth between the back-drilling target layer and the first intermediate layer are summed. By the method, a part of actual back drilling depth is determined, and then the whole back drilling depth is obtained by matching with the relative thickness, so that the back drilling depth is more accurate.
Description
Technical Field
The invention relates to the technical field of printed circuit board manufacturing, in particular to a back drilling depth determining method, a back drilling method and a drilling system.
Background
With the development of the global communication industry, in the Printed Circuit Board (PCB) industry, high frequency digital signal transmission puts higher requirements on the manufacture of high frequency Circuit boards. A common multilayer circuit board is provided with a discontinuous signal path at a via hole, so that impedance discontinuity is easily caused when a signal passes through the circuit board, and a plurality of signal integrity problems are caused. In order to solve the problem, a back drilling process is needed to remove the excessive copper deposit of the via hole. After back drilling, the shorter the excessive copper deposition of the via hole above the signal layer is, the better the influence of the excessive copper deposition of the via hole on the signal transmission of the PCB is reduced.
In the related art, a plated Hole (PTH) is usually back-drilled from a back-drilled surface as a predetermined depth according to a predetermined back-drilling depth of different PCB boards. However, in actual work, due to the fact that the PCB plates are different in precision after being pressed, even if the thicknesses of the PCBs in the same batch of the same PCB material number are different at the same position, thickness tolerance exists. Therefore, the same position of the same type of PCB is subjected to back drilling by the same preset depth, and the accuracy of the back drilling is poor due to the thickness tolerance problem of the PCB.
Disclosure of Invention
In view of the above, it is necessary to provide a back drilling depth determination method, a back drilling method, and a drilling system that improve the accuracy of the back drilling depth.
In a first aspect, an embodiment of the present invention provides a back drilling depth determining method, where the back drilling depth determining method includes:
determining a first intermediate layer and a second intermediate layer according to a back drilling target layer, wherein the back drilling target layer is a layer to be back drilled of the PCB;
the method comprises the steps of obtaining drilling parameters for drilling the PCB, wherein the drilling parameters comprise actual thickness between a back drilling starting layer and a first middle layer determined according to position information of the back drilling starting layer and position information of the first middle layer, which are obtained at each drilling position by a cutter, and the drilling parameters further comprise actual thickness between the first middle layer and a second middle layer determined according to the position information of the first middle layer and the position information of the second middle layer, which are obtained at each drilling position by the cutter;
calculating the relative thickness of the back drilling target layer relative to the first intermediate layer according to the theoretical thickness between the first intermediate layer and the second intermediate layer, the theoretical thickness between the back drilling target layer and the first intermediate layer and the actual thickness between the first intermediate layer and the second intermediate layer;
summing an actual thickness between the backdrilling initiation layer and the first intermediate layer, and a relative thickness between the backdrilling target layer and the first intermediate layer to determine the backdrilling depth.
In some embodiments of the back drilling depth determining method, the determining a first intermediate layer and a second intermediate layer according to a back drilling target layer, where the back drilling target layer is a layer to be back drilled, specifically includes:
selecting a stratum between the back drilling starting layer and the back drilling target layer or a power supply layer between the back drilling starting layer and the back drilling target layer as a first intermediate layer;
selecting a stratum positioned on the extension line of the back drilling path or a power supply layer positioned on the extension line of the back drilling path as a second intermediate layer;
the distance between the first intermediate layer and the second intermediate layer is 0.5mm or more.
In some embodiments of the back drilling depth determination method, the obtaining drilling parameters for drilling the PCB board comprises:
the method comprises the steps of obtaining a PCB, placing the PCB on a drilling platform to be drilled, wherein copper sheet covers the positions, needing drilling, of the first middle layer and the second middle layer of the PCB, and other strata or power supply layers do not cover the copper sheets at the positions needing drilling;
applying a signal with preset frequency on a cutter in advance, and drilling at a position where a drilling initial layer needs to be drilled;
and acquiring position information corresponding to the drilling platform when the cutter is respectively contacted with the drilling starting layer, the first middle layer, the second middle layer and the bottom layer to serve as the drilling parameters, wherein the bottom layer is a layer on the PCB opposite to the drilling starting layer.
In some embodiments of the back drilling depth determination method, the obtaining position information corresponding to the drilling platform when the tool contacts the drilling start layer, the first intermediate layer, the second intermediate layer, and the bottom layer, respectively, as the drilling parameter includes:
acquiring a signal generated when the cutter drills a hole, and acquiring position information of the cutter when a corresponding signal is generated by using a grating ruler;
and arranging the signals and outputting the signals to a control board of a drilling machine in a square wave form, and when the control board reads the rising edge of the square wave, acquiring the position information of the cutter corresponding to the grating ruler at the moment so as to respectively obtain the position information of the drilling starting layer, the first middle layer, the second middle layer and the bottom layer.
In some embodiments of the back drilling depth determination method, the obtaining an actual thickness between the back drilling initiation layer and the first intermediate layer, and an actual thickness between the first intermediate layer and the second intermediate layer specifically includes the following steps:
setting the positions of the back drilling initiation layer, the first intermediate layer and the second intermediate layer relative to the drilling platform as vertical coordinates which are respectively marked as a0, a1 and a 2;
calculating an actual thickness D1= (a 1-a 0) of the back-drill initiation layer and the first intermediate layer, an actual thickness D2= (a 2-a 1) between the first intermediate layer and the second intermediate layer.
In some embodiments of the method of back drilling depth determination, said calculating a relative thickness of said back drilling target layer with respect to said first intermediate layer comprises:
recording a theoretical thickness between the first intermediate layer and the second intermediate layer as H, and a theoretical thickness between the back drilling target layer and the first intermediate layer as H1;
the relative thickness D1= D2 (H1/H) of the backdrilled target layer with respect to the first intermediate layer was calculated by a proportional method.
In a second aspect, an embodiment of the present invention further provides a back drilling method, where the back drilling method includes:
determining the back drilling depth by using the back drilling depth determination method;
and back drilling the PCB according to the back drilling depth.
In some embodiments of the back drilling method, the back drilling method further comprises:
uploading the back drilling depth between the back drilling starting layer and the back drilling target layer at each drilling hole of the PCB to a main system to form back drilling data;
setting an information mark bound with the back drilling data on the PCB;
and scanning the information marks on the PCB to acquire corresponding back drilling data from the main system so as to back drill the PCB.
In a third aspect, an embodiment of the present invention further provides a drilling system, including:
at least one drilling machine, wherein the drilling machine is configured to execute the back drilling method so as to back drill the PCB.
In some embodiments of the drilling system, the drilling system includes a plurality of drilling machines, and the PCB performs drilling and back drilling on different drilling machines, and the drilling system further includes a main system, and the main system is in signal connection with the plurality of drilling machines, so that the drilling machines transmit back drilling data to the main system, or obtain back drilling data from the main system.
The embodiment of the invention has the following beneficial effects:
according to the back drilling depth determining method, the back drilling method and the drilling system of the embodiment, the actual thickness of a section located on a back drilling path, namely the thickness from the back drilling starting layer to the first intermediate layer, is calculated, the relative thickness of the back drilling target layer relative to the first intermediate layer can be calculated according to the obtained vertical coordinates of the first intermediate layer and the second intermediate layer, and then the total back drilling depth can be obtained by summing the actual thickness between the back drilling starting layer and the first intermediate layer and the relative thickness of the back drilling target layer relative to the first intermediate layer. The method increases the operation of detecting the position of the middle inner layer, specifically determines the actual back drilling depth from the inner layer to the back drilling initial layer, and then dynamically judges the position of the back drilling final drilling position when the plate thickness is not uniform by matching with the relative thickness, so as to determine the whole back drilling depth.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Wherein:
fig. 1 shows a flowchart of a back drilling depth determination method according to an embodiment of the present invention;
fig. 2 is a schematic diagram illustrating a back drilling method for back drilling a PCB according to an embodiment of the present invention.
Description of the main element symbols:
100. a PCB board; 10. drilling a starting layer; 20. back drilling a target layer; 30. a first intermediate layer; 40. a second intermediate layer; 50. back drilling the starting layer.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In a practical application scenario, the inventor finds that due to different accuracy of the laminated PCB boards, even though the thicknesses of the same PCB material number and the same batch of PCB boards at the same position are different, thickness tolerance exists. In the prior art, the same position of the same type of PCB is back-drilled with the same preset depth, but due to the thickness tolerance problem of PCBs of different batches, the back-drilling precision is uneven, so that the back-drilling precision is poor, and the use performance of the PCB is affected.
In a first aspect, the invention provides a back drilling depth determination method, which is used for obtaining more accurate back drilling depth, so that the back drilling precision of a drilling machine during back drilling by using the back drilling depth obtained by the method is more ideal, and the back drilling quality of a PCB (printed circuit board) is ensured.
In an embodiment of the present invention, the back drilling depth determination method may include the following steps:
s10, determining a first intermediate layer and a second intermediate layer according to a back drilling target layer, wherein the back drilling target layer is a layer to be back drilled of the PCB;
s20, obtaining drilling parameters for drilling the PCB, wherein the drilling parameters comprise actual thickness between the back drilling starting layer and the first intermediate layer determined according to the position information of the back drilling starting layer and the position information of the first intermediate layer, which are obtained by the cutter at each drilling position, and the actual thickness between the first intermediate layer and the second intermediate layer determined according to the position information of the first intermediate layer and the position information of the second intermediate layer, which are obtained by the cutter at each drilling position;
s30, calculating the relative thickness of the back drilling target layer relative to the first intermediate layer according to the theoretical thickness between the first intermediate layer and the second intermediate layer, the theoretical thickness between the back drilling target layer and the first intermediate layer and the actual thickness between the first intermediate layer and the second intermediate layer;
and S40, summing the actual thickness between the back drilling starting layer and the first intermediate layer and the relative thickness between the back drilling target layer and the first intermediate layer to determine the back drilling depth.
Referring to fig. 2, in the embodiment of the present invention, the first intermediate layer 30 and the second intermediate layer 40 are selected, then the vertical coordinates of the first intermediate layer 30 and the second intermediate layer 40 relative to the drilling platform are respectively measured, so as to calculate the actual thickness between the back drilling initiation layer 50 and the first intermediate layer 30 of the PCB 100 and the actual thickness between the first intermediate layer 30 and the second intermediate layer 40, then the relative thickness between the back drilling target layer 20 and the first intermediate layer 30 is obtained through calculation, and finally the thickness between the back drilling initiation layer 50 and the back drilling target layer 20, that is, the back drilling depth, is obtained through summing the two thicknesses.
It should be noted that, during the production and manufacture of the PCB 100, the total number of layers, the theoretical thickness of each layer, and the position of each layer are recorded. Therefore, the theoretical thickness between the first intermediate layer 30 and the second intermediate layer 40, and the theoretical thickness between the back-drill target layer 20 and the first intermediate layer 30 can be easily obtained by summing the theoretical thicknesses of the corresponding layers.
The depth of the whole back drill can be obtained by accurately confirming a section of back drill depth of the PCB 100 on the back drill path, obtaining the residual depth of the back drill according to a series of parameters and summing the depth of the back drill and the residual depth of the back drill. The method can also be said to be that the position of an intermediate inner layer on the back drilling path is determined firstly, and then the position of the back drilling final drilling position when the plate thickness is not uniform is dynamically judged, so that the determined back drilling depth is more accurate. Compared with the prior art that the back drilling depth is corrected according to the ratio of the board thickness of the PCB recorded during drilling to the theoretical board thickness of the PCB, the back drilling depth determined by the method in the embodiment of the invention is more accurate, and the error of the back drilling depth can be reduced.
In an embodiment, the step S10, that is, determining the first intermediate layer and the second intermediate layer according to the back drilling target layer, may specifically include:
s11, selecting a stratum between the back drilling starting layer and the back drilling target layer or a power supply layer between the back drilling starting layer and the back drilling target layer as a first intermediate layer;
s12, selecting a stratum positioned on the extension line of the back drilling path or a power supply layer positioned on the extension line of the back drilling path as a second middle layer;
and the distance between the S13 and the first intermediate layer and the second intermediate layer is greater than or equal to 0.5 mm.
The copper-clad areas of the ground layer and the power layer of the PCB 100 are very large, and even almost all of the copper is clad, which is beneficial to generate the required parameters when the tool drills, therefore, the ground layer or the power layer is usually selected as the first middle layer 30 and the second middle layer 40. When selecting the ground layer and the power supply layer, it should be noted that, in order to make the back drilling depth obtained later more accurate, the ground layer or the power supply layer which is closer to the back drilling target layer 20 and is respectively located at two sides of the back drilling target layer 20 needs to be selected. It should be noted here that a ground layer or a power supply layer, which is a layer having a relatively short distance between two layers, is selected as the first intermediate layer 30 and the second intermediate layer 40, respectively, and the distance between the first intermediate layer 30 and the second intermediate layer 40 is preferably 0.5mm or more. If the selected distance between the first intermediate layer 30 and the second intermediate layer 40 is less than 0.5mm, it may happen that the tool drills both the second intermediate layer 40 and the first intermediate layer 30, which may affect the position of the subsequent measurements of the first intermediate layer 30 and the second intermediate layer 40.
In a specific embodiment, the step S20, namely acquiring drilling parameters for drilling the PCB, may specifically include the following steps:
s21, obtaining a PCB, placing the PCB on a drilling platform to be drilled, wherein copper sheets cover the positions, needing drilling, of the first middle layer and the second middle layer of the PCB, and copper sheets do not cover other strata or power supply layers at the positions needing drilling;
s22, applying a signal with a preset frequency on the cutter in advance, and drilling at the position where the drilling is needed in the drilling initial layer;
s23, acquiring position information corresponding to the drilling platform when the cutter is respectively contacted with the drilling initial layer, the first middle layer, the second middle layer and the bottom layer, and taking the position information as drilling parameters, wherein the bottom layer is a layer on the PCB opposite to the drilling initial layer.
When the PCB is manufactured, a computer or other intelligent terminals are needed to draw the graphs of each layer of the PCB, or the distribution condition of each layer of the PCB can be understood. For example, in the embodiment of the present invention, a stratum which is located on the upper side and the lower side of the back drilling target layer and is closer to the back drilling target layer, or a power supply layer which is closer to the back drilling target layer needs to be selected as the first intermediate layer and the second intermediate layer, where a distance between the first intermediate layer and the second intermediate layer is not less than 0.5 mm. When producing the PCB board, need be in the position distribution big copper sheet layer of the position of boring the through-hole of being located of first intermediate level and second intermediate level, and other stratum and power plane need not distribute big copper sheet layer in the position of this drilling, just so make when this drilling position is drilled, just so can contact the copper sheet when only cutter contact drilling initial layer, first intermediate level, second intermediate level and bottom, and then make things convenient for the record position. The specific way to draw the distribution diagram of each layer of the PCB is the category of the prior art, and in order to avoid encumbrance, it is not described herein too much.
It should be noted that, if the copper-clad areas of the selected first intermediate layer and the second intermediate layer are not sufficient (it can be said that the copper-clad areas of the first intermediate layer and the second intermediate layer are not sufficient to generate a sufficiently large signal at a subsequent measurement position), one or more layers of the large-area copper-clad layers adjacent to the first intermediate layer and the second intermediate layer need to be selected at this time, so that the large-area copper-clad layers are connected with the first intermediate layer and the second intermediate layer, so that the collected signal value is obvious when the tool contacts the first intermediate layer and the second intermediate layer.
Generally, a drilling machine is used for drilling a hole on a PCB, wherein the drilling machine includes at least one drilling platform and at least one cutter, the bottom end of the PCB is fixed on the drilling platform during drilling, and the drilling machine controls the cutter to drill the hole at a corresponding position on the PCB. It should be noted that, a multilayer PCB is generally formed by alternately stacking metal layers and insulating layers, so after drilling is completed, copper plating is required to be performed on the inner wall of the hole to electrically connect the metal layers, and copper plating on the inner wall of the hole is a prior art and will not be described herein.
Referring to fig. 2, during drilling, a hole is drilled from an end (i.e., the drilling initiation layer 10) of the PCB 100 away from the drilling platform toward the drilling platform, and the parameters to be obtained during drilling include longitudinal positions, i.e., vertical coordinates, of the drilling initiation layer 10, the first intermediate layer 30, the second intermediate layer 40, and the bottom layer (not shown) of the PCB 100 relative to the drilling platform, as drilling parameters. The drilling platform can be set as a reference surface in the longitudinal direction, i.e. the origin of the ordinate. It should be noted that, in an actual application scenario, the required ordinate may be obtained specifically by using a capacitive type or a current type.
Specifically, in the capacitor type, since the drilling start layer 10 of the PCB 100 is generally a full copper-clad layer, the surfaces of the first intermediate layer 30 and the second intermediate layer are almost entirely copper-clad. The structure similar to the capacitor can be formed between the drilling starting layer 10, the second intermediate layer 40 and the layers between the drilling starting layer 10 and the second intermediate layer 40, and similarly, the capacitor structure is formed by the first intermediate layer 30, the second intermediate layer 40 and the layers between the two layers, and the capacitor structure is also formed by the first intermediate layer 30, the bottom layer and the layers between the two layers. It should be noted that, in general, the bottom layer of the PCB 100 is similar to the drilling initiation layer 10, and a large area of copper is covered, and during drilling, a paper board is required to be placed between the PCB 100 and the drilling platform, or in addition to placing the paper board, a customer may require a bakelite board to be placed between the paper board and the drilling platform, so that the bottom layer of the PCB can also form a capacitor structure with the drilling platform. Therefore, the whole PCB board 100 can be regarded as a plurality of capacitor structures connected in series.
Before drilling, firstly, an alternating current signal with a preset frequency is applied to the cutter, and the signal generates a current signal when forming a loop. Since the drilling platform is grounded, when the tool comes into contact with the drilling initiation layer 10, an ac signal previously applied to the tool can form a loop with the drilling platform through the PCB board 100, which is equivalent to applying an ac signal in a loop having several capacitors to charge the capacitors. When actually drilling, a receiving circuit on the drilling machine can judge whether a loop is formed or not through the amplitude of the capacitor charging voltage in the loop. And then acquiring the position information of the drilling starting layer 10, the first middle layer 30, the second middle layer 40 and the bottom layer of the PCB according to the loop signal.
In the current type position measuring method, unlike the capacitive type, it is necessary to connect the ground of the control board of the drilling machine to the drilling initiation layer 10, the second intermediate layer 40, the first intermediate layer 30 and the bottom layer of the PCB, respectively, when the tool contacts any one of the layers, a loop is formed, and a current signal is also generated, and when the tool drills through one of the drilling initiation layer 10, the second intermediate layer 40, the first intermediate layer 30 or the bottom layer of the PCB, an open circuit is formed, and the current signal disappears. The receiving circuit on the drill will determine whether a loop is formed by the amplitude of the current signal in the loop. And then acquiring the position information of the drilling starting layer 10, the first middle layer 30, the second middle layer 40 and the bottom layer of the PCB according to the loop signal. The specific method for measuring the position can be determined according to actual conditions, and is not limited herein. The embodiments of the present invention are described with reference to the capacitance.
It should be noted that, when back drilling the PCB 100, one way is to turn over the bottom layer of the PCB and the drilling initiation layer 10, so that the drilling initiation layer 10 is below the bottom layer of the PCB, and then back drilling is performed with the bottom layer of the PCB as the back drilling initiation layer 50, and another way is to perform back drilling directly from the drilling initiation layer 10, and then the drilling initiation layer 10 may be regarded as the back drilling initiation layer 50. In the embodiment of the present invention, the bottom layer of the PCB is taken as the back drilling initiation layer 50 for illustration.
In a specific embodiment, the step S23, namely acquiring position information corresponding to the drilling platform when the tool contacts the drilling start layer, the first middle layer, the second middle layer and the bottom layer respectively, as the drilling parameters, specifically includes:
s231, acquiring a signal generated when the cutter drills, and acquiring position information of the cutter when a corresponding signal is generated by using a grating ruler;
s232, arranging the signals and outputting the signals to a control board of a drilling machine in a square wave mode, and when the control board reads the rising edge of the square wave, obtaining the position information of the cutter corresponding to the grating ruler at the moment so as to respectively obtain the position information of the drilling starting layer, the first middle layer, the second middle layer and the bottom layer.
In the above embodiment, the drilling device is further provided with a grating ruler, the grating ruler functions as a sensor, when the signal in the loop is acquired, the grating ruler can give the position corresponding to the tool at a certain signal position, and then store the information of the position. The positions of the drilling starting layer 10, the first intermediate layer 30, the second intermediate layer 40 and the bottom layer of the PCB relative to the drilling platform can be obtained by determining the corresponding signals of the tool when the tool respectively contacts the drilling starting layer 10, the first intermediate layer 30, the second intermediate layer 40 and the bottom layer, and the recorded positions of the grating ruler when the grating ruler collects the signals. It should be noted that there is a signal interval from when the tool contacts the drilling start layer 10 to just through the drilling start layer 10, or from when the tool contacts the drilling start layer 10 to just after drilling on the drilling start layer 10. Since each layer between the drilling start layer 10 and the first intermediate layer 30 does not have copper cladding at the drilling position when designing the PCB, although a signal is generated when the tool drills between the drilling start layer 10 and the second intermediate layer 40, the signal is small, and only when the tool contacts the second intermediate layer 40, the signal becomes large suddenly, and so is the subsequent drilling. Therefore, the trend that the signals are suddenly high and suddenly low during drilling can be easily obtained, the signals sent when the cutter respectively contacts the drilling initial layer 10, the second middle layer 40, the first middle layer 30 and the bottom layer of the PCB can be easily distinguished when the signals rise, and further the position information of the cutter corresponding to the signals can be easily determined through the grating ruler.
Specifically, when the cutter contacts the drilling starting layer 10, the first intermediate layer 30, the second intermediate layer 40 and the bottom layer of the PCB and drills holes on the layers, a loop is formed with the drilling platform, the capacitor charging voltage is large, and when the cutter drills holes on each layer between the layers, the cutter forms an open circuit with the grounding platform, and the capacitor charging voltage is small, so that the trend information of the signal, namely the periodic increase and decrease of the signal, can be easily acquired when the cutter drills holes. A threshold value may be set based on the values of the higher voltage signal and the lower voltage signal, the threshold value being between the high signal and the low signal. By comparing the obtained relationship between the voltage signal and the threshold, the voltage signal can be output in the form of a square wave, wherein the wave crest represents the voltage signal higher than the threshold, and the wave trough represents the voltage signal lower than the threshold. The square wave can be transmitted to a control board (the control board is the existing structure of the drilling device and is not described much here), the control board receives the square wave and when the control board reads the rising edge of the square wave, the control board indicates that the cutter just contacts one of the drilling starting layer 10, the first middle layer 30, the second middle layer 40 and the bottom layer of the PCB, and as to which layer the cutter is, the follow-up can be determined according to the sequence of the data. When the control board reads the rising edge of the square wave, the position information recorded in the grating ruler at the moment is read, so that the positions of the drilling starting layer 10, the first middle layer 30, the second middle layer 40 and the bottom layer of the PCB can be obtained, and the vertical coordinate of each layer is calculated.
In a specific embodiment, the step S20 may specifically include:
s24, setting the positions of the back drilling starting layer, the first intermediate layer and the second intermediate layer relative to the drilling platform as vertical coordinates which are respectively marked as a0, a1 and a 2;
s25, calculating an actual thickness D1= (a 1-a 0) of the back-drill initiation layer and the first interlayer, and an actual thickness D2= (a 2-a 1) between the first interlayer and the second interlayer.
And the coordinates of the first intermediate layer and the second intermediate layer measured when the cutter drills are the actual vertical coordinates relative to the drilling platform. By calculating the quantitative relationship between these ordinates, the actual thickness between the first intermediate layer and the second intermediate layer can be derived.
It should be noted that, referring to fig. 2, in general, since the drilling initiation layer 10 during drilling the PCB 100 is usually opposite to the back drilling initiation layer 50 when the PCB 100 is processed, that is, the bottom layer of the PCB is the back drilling initiation layer 50, a difference between a vertical coordinate of the first intermediate layer 30 and a vertical coordinate of the bottom layer is an actual thickness of the back drilling initiation layer 50 and the first intermediate layer. Because the back-drill target layer 20 is located between the first intermediate layer 30 and the second intermediate layer 40, the actual thickness of the back-drill initiation layer 50 and the first intermediate layer 30 is a portion of the actual back-drill depth at which back-drilling from the back-drill initiation layer 50 begins.
It should be noted that, as mentioned above, sometimes the back drilling may also be directly started at the drilling start layer 10 of the PCB 100, when the back drilling is performed at the drilling start layer 10, the thickness to be calculated is the thickness between the drilling start layer 10 and the second intermediate layer 40, and it is only necessary to subtract the ordinate of the second intermediate layer 40 from the ordinate of the drilling start layer 10. Whether the back drilling is started from the bottom layer of the PCB or the drilling starting layer 10, a layer of aluminum sheet needs to be laid, and at the moment, the thickness of the aluminum sheet needs to be added when the back drilling depth is calculated.
In addition, when back drilling the hole starting layer 10, attention needs to be paid to whether the back drilling position is deformed or not and the type of the deformation. Specifically, the ordinate of each position of the drilling initiation layer 10 can be measured, the measured ordinate is the actual thickness of each position of the drilling initiation layer 10, and at this time, the actual thickness of the position requiring backdrilling is compared with the theoretical thickness, and whether the actual thickness and the theoretical thickness are the same or not is compared. If the actual thickness of the back drilling position is different and smaller than the theoretical thickness, it can be determined that the position of the drilling starting layer 10 is in a concave structure, in this case, the actual thickness from the aluminum plate to the second intermediate layer 40 cannot be the thickness of the aluminum plate added to the thickness between the drilling starting layer 10 and the second intermediate layer 40, the actual thickness from the aluminum plate to the second intermediate layer 40 at this time is equal to the thickness between the drilling starting layer 10 and the second intermediate layer 40 added to the thickness of the aluminum plate, and then the difference between the theoretical thickness and the actual thickness of the PCB 100 at this time needs to be added. Alternatively, the actual thickness of the PCB 100 at the back-drilling position is greater than the theoretical thickness, and at this time, the back-drilling tool is directly used to drill the depth of the second intermediate layer 40 by the thickness between the drilling start layer 10 and the second intermediate layer 40 plus the thickness of the aluminum plate.
In an embodiment, step S30 may specifically include:
s31, recording the theoretical thickness between the first intermediate layer and the second intermediate layer as H, and recording the theoretical thickness between the back drilling target layer and the first intermediate layer as H1;
s32, calculating the relative thickness D1= D2 (H1/H) of the backdrilling target layer with respect to the first intermediate layer by a proportional method.
Referring to fig. 2, in the process of manufacturing the PCB 100, it is desirable that the surfaces of the stacked layers are not deformed, and therefore, the theoretical thickness between the first intermediate layer 30 and the second intermediate layer 40 and the theoretical thickness between the back drill target layer 20 and the first intermediate layer 30 can be obtained by summing the theoretical thicknesses of the respective layers of the PCB 100. Knowing the actual thickness between the first intermediate layer 30 and the second intermediate layer 40, the position of the backdrilling target layer 20 relative to the first intermediate layer 30 can now be derived using the proportional method calculation formula D1= D2 (H1/H). At this time, the thickness between the back-drill target layer 20 and the first intermediate layer 30 is obtained as the remaining depth of the back-drill. The actual thickness D1 between the back-drilling initiation layer 50 and the first intermediate layer 30, and the relative thickness D1 between the back-drilling target layer 20 and the first intermediate layer 30 are simply summed to obtain the depth of the entire back-drilling.
For a more clear understanding of the back drilling depth determination method according to the embodiment of the present invention, a specific example is given for further explanation.
Referring to fig. 1, the back drilling depth determining method includes:
s100, selecting a first intermediate layer and a second intermediate layer according to a back drilling target layer: and selecting a first intermediate layer and a second intermediate layer on two sides of the back drilling target layer according to the position of the back drilling target layer required, wherein the surfaces of the selected first intermediate layer and the second intermediate layer are required to be covered with copper sheets with a large enough area. Generally, the ground layer and the power layer on the PCB are covered with a large area of copper sheet. Therefore, the stratum or the power supply layer positioned between the back drilling starting layer and the back drilling target layer is selected as the first intermediate layer, and the stratum or the power supply layer positioned on the extension line of the back drilling path is selected as the second intermediate layer. It should be noted that, in order to obtain a more accurate back drilling depth in the subsequent step, both the first intermediate layer and the second intermediate layer need to be as close to the back drilling target layer as possible, but the distance between the first intermediate layer and the second intermediate layer needs to be not less than 0.5 mm;
s200, forming a capacitive measurement loop: the drilling platform is grounded, an alternating current signal is applied to a drilling cutter, a capacitor structure can be formed between the drilling starting layer and the second middle layer, between the second middle layer and the first middle layer, and between the first middle layer and the bottom layer of the PCB, and the whole PCB is equivalent to a structural capacitor series structure. When the tool with the alternating current signal contacts the drilling initial layer, a loop can be formed, and a voltage signal for charging the capacitor is generated.
S300, acquiring position information of a drilling starting layer, a first middle layer, a second middle layer and a bottom layer of the PCB: when the cutter drills, the position of the cutter relative to the drilling platform can be recorded through the grating ruler, specifically, the grating ruler is equivalent to a sensor, as long as a signal is transmitted to the grating ruler, the grating ruler can record the position of the cutter relative to the drilling platform at the moment after capturing the signal, and position information is stored. When the cutter drills, a higher signal value is generated only when the cutter contacts with a drilling starting layer, a first middle layer, a second middle layer and a bottom layer of the PCB, a lower signal value is generated when the cutter contacts with other layers, even no signal is generated, therefore, a threshold value is set between the high signal value and the low signal value according to the high signal value and the low signal value, a signal exceeding the threshold value forms a wave crest, a signal lower than the threshold value forms a wave trough, and the signal is output in a square wave mode. The rising edge of the square wave signal corresponds to that the cutter just contacts one of the drilling initial layer, the first middle layer, the second middle layer and the bottom layer of the PCB. The square wave signal is received through the receiving circuit and is transmitted to the control panel, when the control panel catches the rising edge, gathers the positional information of grating chi record this moment immediately to gather the relative positional information of the bottom of drilling initial layer, second intermediate level and first intermediate level and PCB board in proper order.
S400, determining the back drilling depth: the position of the drilling platform is set as a starting point, and the vertical coordinates of the drilling starting layer, the first middle layer of the second middle layer and the bottom layer of the PCB can be respectively obtained according to the position information of the drilling starting layer, the second middle layer, the first middle layer and the bottom layer of the PCB relative to the drilling platform. When the back drilling is started from the bottom layer of the PCB, the thickness from the back drilling starting layer to the first middle layer can be obtained as the difference value between the ordinate of the first middle layer and the ordinate of the bottom layer of the PCB.
And subtracting the ordinate of the first intermediate layer from the ordinate of the second intermediate layer to obtain the actual thickness D2 between the first intermediate layer and the second intermediate layer, obtaining the theoretical thickness H between the first intermediate layer and the second intermediate layer and the theoretical thickness H1 between the first intermediate layer and the back drilling target layer through processing data during processing of the PCB, and calculating the relative thickness of the back drilling target layer from the first intermediate layer by using a proportional method calculation formula D1= D2 (H1/H). Finally, the thickness is added to the thickness from the back drilling initial layer to the first intermediate layer to obtain the back drilling depth.
Briefly, the back drilling depth is divided into two parts, one part is the actual back drilling depth which can be obtained, the other part is the relative thickness of the obtained back drilling target layer, and the sum of the two parts is the back drilling depth. Compared with the method that the back drilling depth is corrected by directly using the ratio of the thickness of the PCB obtained in the drilling process to the theoretical thickness of the PCB, the back drilling depth obtained by the method in the embodiment is more accurate.
In a second aspect, an embodiment of the present invention further provides a back drilling method, where the back drilling method includes: and determining the back drilling depth by using the back drilling depth determination method of any embodiment of the first aspect, and back drilling the PCB according to the back drilling depth.
It should be noted that the back drilling described in the above embodiments may specifically include, but is not limited to, a milling process, a cutting process, or a drilling process related to depth control, and the back drilling process is not limited to this, and may be selected according to an actual scenario.
Based on the first aspect, the back drilling depth can be determined more accurately by adding the operation of detecting the position of the middle inner layer, and the back drilling method for processing according to the back drilling depth in the above embodiment can control the processing depth of the circuit board more accurately, so that the back drilling quality of the circuit board is improved.
In one embodiment, the back drilling method may further comprise:
s511, uploading the back drilling depth between the back drilling initial layer and the back drilling target layer at each drilling hole of the PCB to a main system to form back drilling data;
s512, setting an information mark bound with the back drilling data on the PCB;
s513, the corresponding back drilling data is obtained from the main system by scanning the information marks on the PCB so as to back drill the PCB.
Typically, the PCB is drilled and backdrilled on one machine, but sometimes the PCB is drilled and backdrilled on a different machine, requiring a host system to be established between the different machines, the host system being connected to each drilling machine. After the PCB board drills the through hole, the back drilling data recorded into the drilling machine when the PCB board drills the through hole is packaged and sent to the main system for storage, and it should be noted here that the back drilling data may be not only the back drilling depth between the back drilling starting layer and the back drilling target layer, but also the longitudinal coordinate values of the back drilling starting layer, the first intermediate layer, and the second intermediate layer, and the like. After the back drill data is sent to the main system, an information mark bound with the back drill data can be arranged on the PCB, and the information mark can be a unique bar code or a two-dimensional code and the like. When the PCB with the drilled hole is taken to another machine for back drilling, the machine for back drilling can acquire corresponding back drilling data in the main system by scanning the information mark, so that the PCB can be back drilled quickly, conveniently and accurately.
In a third aspect, an embodiment of the present invention further provides a drilling system, where the drilling system mainly includes at least one drilling machine, and the drilling machine is configured to perform the above-mentioned back drilling method to back drill the PCB.
In a specific embodiment, the drilling system comprises a plurality of drills, and the PCB board is through-drilled and back-drilled on different drills. The drilling system further comprises a main system, a control module is arranged in the drilling machine, the control module is the core of the drilling machine, the drilling machine is controlled by the control module, and the control module is the prior art and is not described herein too much. The main system can be in signal connection with the control modules in the drilling machines through a wireless network, so that the control modules in the drilling machines can send back drilling data to the main system, or the control modules can acquire the back drilling data from the main system.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method of back drilling depth determination, comprising:
determining a first intermediate layer and a second intermediate layer according to a back drilling target layer, wherein the back drilling target layer is a layer to be back drilled of the PCB;
the method comprises the steps of obtaining drilling parameters for drilling the PCB, wherein the drilling parameters comprise actual thickness between a back drilling starting layer and a first middle layer determined according to position information of the back drilling starting layer and position information of the first middle layer, which are obtained at each drilling position by a cutter, and the drilling parameters further comprise actual thickness between the first middle layer and a second middle layer determined according to the position information of the first middle layer and the position information of the second middle layer, which are obtained at each drilling position by the cutter;
calculating the relative thickness of the back drilling target layer relative to the first intermediate layer according to the theoretical thickness between the first intermediate layer and the second intermediate layer, the theoretical thickness between the back drilling target layer and the first intermediate layer and the actual thickness between the first intermediate layer and the second intermediate layer;
summing an actual thickness between the backdrilling initiation layer and the first intermediate layer, and a relative thickness between the backdrilling target layer and the first intermediate layer to determine the backdrilling depth.
2. The back drilling depth determination method according to claim 1, wherein the determining of the first intermediate layer and the second intermediate layer according to a back drilling target layer, the back drilling target layer being a layer to be back drilled, specifically comprises:
selecting a stratum between the back drilling starting layer and the back drilling target layer or a power supply layer between the back drilling starting layer and the back drilling target layer as a first intermediate layer;
selecting a stratum positioned on the extension line of the back drilling path or a power supply layer positioned on the extension line of the back drilling path as a second intermediate layer;
the distance between the first intermediate layer and the second intermediate layer is 0.5mm or more.
3. The back-drilling depth determination method of claim 2, wherein the obtaining drilling parameters for drilling the PCB board comprises:
the method comprises the steps of obtaining a PCB, placing the PCB on a drilling platform to be drilled, wherein copper sheet covers the positions, needing drilling, of the first middle layer and the second middle layer of the PCB, and other strata or power supply layers do not cover the copper sheets at the positions needing drilling;
applying a signal with preset frequency on a cutter in advance, and drilling at a position where a drilling initial layer needs to be drilled;
and acquiring position information corresponding to the drilling platform when the cutter is respectively contacted with the drilling starting layer, the first middle layer, the second middle layer and the bottom layer to serve as the drilling parameters, wherein the bottom layer is a layer on the PCB opposite to the drilling starting layer.
4. The back-drilling depth determination method according to claim 3, wherein the acquiring position information corresponding to the drilling platform when the tool contacts the drilling start layer, the first intermediate layer, the second intermediate layer, and the bottom layer, respectively, as the drilling parameter comprises:
acquiring a signal generated when the cutter drills a hole, and acquiring position information of the cutter when a corresponding signal is generated by using a grating ruler;
and arranging the signals and outputting the signals to a control board of a drilling machine in a square wave form, and when the control board reads the rising edge of the square wave, acquiring the position information of the cutter corresponding to the grating ruler at the moment so as to respectively obtain the position information of the drilling starting layer, the first middle layer, the second middle layer and the bottom layer.
5. The back drilling depth determination method according to claim 1, wherein the obtaining of the actual thickness between the back drilling initiation layer and the first intermediate layer and the actual thickness between the first intermediate layer and the second intermediate layer specifically comprises the following steps:
setting the positions of the back drilling initiation layer, the first intermediate layer and the second intermediate layer relative to the drilling platform as vertical coordinates which are respectively marked as a0, a1 and a 2;
calculating an actual thickness D1= (a 1-a 0) of the back-drill initiation layer and the first intermediate layer, an actual thickness D2= (a 2-a 1) between the first intermediate layer and the second intermediate layer.
6. The back-drilling depth determination method of claim 1, wherein the calculating a relative thickness of the back-drilling target layer with respect to the first intermediate layer comprises:
recording a theoretical thickness between the first intermediate layer and the second intermediate layer as H, and a theoretical thickness between the back drilling target layer and the first intermediate layer as H1;
the relative thickness D1= D2 (H1/H) of the backdrilled target layer with respect to the first intermediate layer was calculated by a proportional method.
7. A back drilling method, comprising:
determining a back drilling depth using the back drilling depth determination method of any one of claims 1-6;
and back drilling the PCB according to the back drilling depth.
8. The back drilling method of claim 7, further comprising:
uploading the back drilling depth between the back drilling starting layer and the back drilling target layer at each drilling hole of the PCB to a main system to form back drilling data;
setting an information mark bound with the back drilling data on the PCB;
and scanning the information marks on the PCB to acquire corresponding back drilling data from the main system so as to back drill the PCB.
9. A drilling system, comprising:
at least one drilling machine configured to perform the back drilling method of claim 7 or claim 8 to back drill a PCB board.
10. The drilling system of claim 9, wherein the drilling system comprises a plurality of drilling machines, and the PCB board is drilled and backdrilled on different drilling machines, the drilling system further comprising a host system in signal communication with each of the plurality of drilling machines for the drilling machines to transmit the backdrilling data to the host system or to obtain the backdrilling data from the host system.
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