WO2022068162A1

WO2022068162A1 - Measurement method and circuit board

Info

Publication number: WO2022068162A1
Application number: PCT/CN2021/084940
Authority: WO
Inventors: 许校彬; 陈金星
Original assignee: 惠州市特创电子科技股份有限公司
Priority date: 2020-09-30
Filing date: 2021-04-01
Publication date: 2022-04-07
Also published as: CN112179252A

Abstract

A measurement method and a circuit board (70). The measurement method comprises: injecting a colloidal solution into a back-drilled hole (714) to be measured that is obtained by back drilling; solidifying the colloidal solution into a semi-gel state by means of a solidification operation; then taking semi-gel out of the hole to be measured; and measuring, by means of a back drilling measurement device, the depth of the back-drilled hole (714) corresponding to the semi-gel, the obtained measurement result being the depth of the hole to be measured. The operation mode is simple, the measurement efficiency is high, and no damage is caused to the circuit board (70). Without slicing the drilled board, the depth of the back-drilled hole (714) can be directly obtained by measuring the depth of the semi-gel, and the method is thus high in detection efficiency, low in cost and simple in operation mode.

Description

Measurement method and circuit board

technical field

The invention relates to the technical field of printed circuit board fabrication, in particular to a measurement method and a circuit board.

Background technique

With the rapid development of the global communication industry, the demand for high-level multi-layer communication boards has increased dramatically, and 5G or higher frequency digital signal transmission has put forward higher requirements for the manufacture of high-frequency circuit boards. Ordinary multi-layer circuit boards have discontinuous signal paths at the vias when the signals pass through, which can easily cause impedance discontinuities and bring about signal integrity problems such as attenuation, reflection, and delay. In order to solve the signal integrity problem caused by vias, PCB manufacturers often use back-drilling technology to process special multi-layer circuit boards to ensure signal integrity.

The back-drilling process drills out the through-hole section that does not play any connection or transmission function, so as to avoid reflection, scattering, delay, etc. of high-speed signal transmission, which will bring "distortion" to the signal. In order to solve this problem, it is necessary to further process the through holes of the circuit board, that is, a back-drilling process, thereby obtaining a circuit board with back-drilled holes. A circuit board with back-drilled holes is also called a back-drilled board. The function of back-drilling is to drill out the through-hole section that does not play any connection or transmission function, so as to avoid reflection, scattering and delay of signal transmission. In fact, in addition to design, board materials, transmission lines, connectors, chip packaging and other factors, vias have a greater impact on the signal integrity of the signal system. Therefore, the back-drilling process is very important for the signal transmission of the circuit board.

However, due to high processing requirements and precision requirements, it is easy to miss drilling during operation, and it is difficult to control the depth of back-drilling holes. The current method of detecting the depth of back-drilling holes is mainly to manually slice the specified circuit board level. Then use a microscope to observe whether the depth and level of the back drilling meet the requirements. However, the efficiency of slicing a specified layer and then observing it manually through a microscope is low, and a large number of slices need to be made, which requires manual cutting and grinding, which is costly to process, and the circuit board will be damaged by making slices. That is to say, the traditional method for detecting the depth of back-drilling has the problems of low detection efficiency, high processing cost and complicated detection process.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art, and to provide a measurement method and a circuit board with high detection efficiency, low cost and simple operation.

The purpose of this invention is to realize through the following technical solutions:

A measurement method for measuring a circuit board, comprising the steps of:

The circuit board is processed into a through hole and a back hole that are connected to each other, wherein the hole diameter of the through hole is a first preset value, the hole diameter of the back hole is a second preset value, and the first The preset value is smaller than the second preset value;

injecting the colloidal solution into the through-hole and the back-drilled hole respectively, so that the through-hole and the back-drilled hole are completely filled with the colloidal solution;

performing a solidification treatment operation on the colloidal solution in the through hole and the back-drilled hole, so that the colloidal solution in the through-hole and the back-drilled hole forms a colloid in a semi-gel state;

Scraping off the excess colloid on the edge of the through hole and the back-drilled hole;

The colloid is taken out, and the depth and alignment degree of the colloid are measured to obtain the depth value and alignment degree value of the colloid.

In one embodiment, the first preset value is 2.0 mm˜2.2 mm.

In one embodiment, the second preset value is 3.0 mm˜3.2 mm.

In one embodiment, the colloidal solution is a silica gel solution.

In one embodiment, before the step of curing the colloidal solution in the through hole and the back drilling, and before the colloidal solution is injected into the through hole and the back hole, respectively After the steps in the drilling, the measuring method further comprises the steps of:

The colloidal solution was allowed to stand for 3 min to 5 min.

In one embodiment, before the step of injecting the colloidal solution into the through hole and the back-drilled hole respectively, and after the step of processing the connected through-hole and the back-drilled hole on the circuit board, The measurement method also includes:

A grease layer is coated on the hole walls of the through hole and the back-drilled hole.

In one embodiment, the steps of taking out the colloid and measuring the depth and alignment of the colloid are as follows:

The colloid is taken out from the through hole to the back-drilled hole, and the depth and alignment of the colloid are measured.

A circuit board, which is measured by using the measurement method described in any of the above embodiments.

In one embodiment, the circuit board includes a circuit board body, and a signal layer, a power ground layer and a preset safety distance layer respectively disposed in the circuit board body, and the through hole is opened adjacent to the signal layer , the back-drilled hole is opened adjacent to the power supply ground layer, the preset safety distance layer is electrically connected to the signal layer, and the preset safety distance layer is disconnected from the ground power supply layer through the back-drilled hole .

In one embodiment, the thickness of the preset safety distance layer is 40 μm˜100 μm.

Compared with the prior art, the present invention has at least the following advantages:

In the measurement method of the present invention, the colloidal solution is injected into the back-drilled hole to be measured after the back-drilling, and the colloidal solution is solidified into a semi-gel state through a curing operation, and then the semi-gel is taken out from the hole to be measured, and the The back-drilling measuring device measures the depth of the half-gel corresponding to the back-drilling hole, and the obtained measurement result is the depth of the hole to be measured. The operation method is simple, the measurement efficiency is high, and the circuit board is not damaged. Different from the traditional method of changing the compensation through the trial drilling value, the compensation is changed by slicing. During the process, the machine needs to wait for the slicing result before compensation can be produced, which consumes a lot of time and personnel energy. The method adopted in the present invention does not require slicing the drill plate, and can directly obtain the depth of the back-drilled hole by measuring the depth of the semi-gel, and has the advantages of high detection efficiency, low cost and simple operation mode.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

1 is a flowchart of a measurement method in an embodiment;

Fig. 2 is the structural representation of the back drill measuring device that the measuring method shown in Fig. 1 measures the circuit board;

3 is a schematic structural diagram of the back-drill measuring device used for measuring the circuit board by the measuring method shown in FIG. 1 under the measuring state;

FIG. 4 is a schematic structural diagram of a circuit board before measurement using the measurement method shown in FIG. 1 according to an embodiment;

FIG. 5 is a schematic structural diagram of a circuit board during measurement using the measurement method shown in FIG. 1 according to an embodiment.

Detailed ways

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the related drawings. The preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the present disclosure is provided.

It should be noted that when an element is referred to as being "fixed 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 similar expressions used herein are for the purpose of illustration only and do not represent the only embodiment.

Unless otherwise defined, 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 terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The present application provides a measurement method for measuring a circuit board. The above-mentioned measurement method includes the following steps: processing the circuit board into connected through holes and back drill holes, wherein the diameter of the through holes is a first preset value, and the diameter of the back drill holes is a second preset value. set value, the first preset value is smaller than the second preset value; inject the colloidal solution into the through hole and the back drill hole respectively, so that the through hole and the back drill hole are completely filled having the colloidal solution; performing a solidification treatment operation on the colloidal solution in the through-hole and the back-drilled hole, so that the colloidal solution in the through-hole and the back-drilled hole forms a colloid in a semi-gel state; The excess colloid on the edge of the through hole and the back-drilled hole is scraped off; the colloid is taken out, and the depth and alignment of the colloid are measured to obtain the depth value of the colloid and the corresponding colloid. accuracy value.

In the above measurement method, the colloidal solution is injected into the back-drilled hole to be measured after back-drilling, and the colloidal solution is solidified into a semi-gel state through a curing operation, and then the semi-gel is taken out from the hole to be measured, and passed through the back hole. The drill measuring device measures the depth of the back-drilled hole corresponding to the semi-gel, and the obtained measurement result is the depth of the hole to be measured. The operation method is simple, the measurement efficiency is high, and the circuit board is not damaged. Different from the traditional method of changing the compensation through the trial drilling value, the compensation is changed by slicing. During the process, the machine needs to wait for the slicing result before compensation can be produced, which consumes a lot of time and personnel energy. The method adopted in the present invention does not require slicing the drill plate, the depth of the back drill hole can be directly obtained by measuring the depth of the semi-gel, and the colloidal solution is very easy to obtain and the cost is relatively low. The above measurement method has the advantages of high detection efficiency, low cost and simple operation.

In order to better understand the measurement method of the present invention, the measurement method of the present invention will be further explained below. The measurement method of an embodiment is used to measure a circuit board. The measurement method includes the following steps:

S100. Process the circuit board to form through holes and back drill holes that are connected to each other, wherein the diameter of the through holes is a first preset value, the diameter of the back drill holes is a second preset value, and the first preset value is smaller than the second preset value. default value. In this embodiment, the back drill is used to machine a through hole with a first preset value at the position of the circuit board frame, and the depth control part, that is, the back drill part, uses a tool with a second preset value to test the hole, and the size of the hole is determined by itself. Processing, only the depth is processed according to the user's requirements, so as to ensure that the depth gauge can be used for subsequent measurement. It solves the problem that the back drill produces a test hole consistent with the user's standard at the frame position. When the hole diameter processed by the user is small, the depth gauge cannot be used and must be sliced to measure, thereby improving the measurement efficiency.

S200, inject the colloidal solution into the through hole and the back-drilled hole respectively, so that the through-hole and the back-drilled hole are completely filled with the colloidal solution. In this embodiment, the colloidal solution is injected into the through-holes and back-drilled holes to be measured in the circuit board through a glue gun, so that the colloidal solution completely fills the through-holes and the back-drilled holes, so as to form the same structure as the hole to be measured. For the shape of the colloid, the depth of the back drilling and the through hole can be obtained by measuring the depth of the colloid. The measurement operation is simple and the measurement efficiency is high.

S300, performing a curing operation on the colloidal solution in the through hole and the back-drilled hole, so that the colloidal solution in the through-hole and the back-drilled hole forms a colloid in a semi-gel state. In this embodiment, the colloidal solution filled in the back-drilled holes and the through holes is subjected to a curing operation, and the colloidal solution is heated by a heat gun, so that the colloidal solution is cured and maintained in a semi-gel state, thereby facilitating the colloidal solution. The removal operation and the solidification of the colloid in a semi-solid state of semi-gel facilitate subsequent measurement of the colloid and improve the accuracy of the measurement.

S400, scrape off excess colloid on the edge of the through hole and the back-drilled hole. In this embodiment, by scraping off the excess colloid kept in the semi-gel state on the edges of the through hole and the back-drilled hole, the edges of the colloid kept in the semi-gel state are separated from the colloid of the through hole and the back-drilled hole respectively. The edges are kept consistent, so as to ensure the alignment of the colloid, avoid measurement errors caused by the shape of the colloid and the shape of the hole to be measured, and thus improve the accuracy of the back drill measurement.

S500, the colloid is taken out, and the depth and alignment degree of the colloid is measured to obtain the depth value and alignment degree value of the colloid. In this embodiment, the colloid kept in the semi-gel state is taken out from the drill plate, and the length and alignment of the colloid are measured. Wherein, the measurement of the length of the colloid includes the part of the colloid corresponding to the back-drilled shape structure, the part corresponding to the through-hole shape structure and the length of the whole colloid. For the depth of the drilled hole, by subtracting the length of the part corresponding to the through hole shape structure from the overall length of the colloid, the measurement result of the part corresponding to the back drill hole shape structure can be checked, thereby improving the measurement accuracy. In addition, by measuring the alignment degree of the colloid, the alignment deviation data of the colloid can be obtained and adjusted according to the alignment deviation data, which is beneficial to improve the accuracy of the back-drilling measurement, and at the same time, it is beneficial to control the deviation between the back-drilling hole and the through hole. offset, thereby improving the accuracy of backdrilling. Among them, the length of the S line segment shown in Figure 5 is the depth of the glue column; the length of the A line segment shown in Figure 5 is equal to the distance between one side of the glue column and the center line, and the length of the B line segment is equal to the other side of the glue column and the center line The absolute value of the difference between the length of line A and the length of line B is the alignment of the glue column. It can be understood that if the absolute value is smaller, the alignment degree of the glue column is smaller, that is, the symmetry on both sides of the glue column is better; otherwise, the alignment degree of the glue column is larger, that is, the symmetry on both sides of the glue column is higher. Difference.

Further, according to the measurement results of the length and alignment of the colloid, the depth of the back-drilling hole can be adjusted on site, and the depth of the back-drilling hole can be adjusted to obtain a second back-drilling hole, so that the depth of the second back-drilling hole reaches predetermined depth. According to the measurement result of the length of the colloid, the preliminary result of the back-drilling depth is calculated. According to the measurement result of the alignment degree of the colloid, the accuracy of the preliminary result of the back-drilling depth is checked. If the alignment degree reaches the standard, the back-drilling depth is obtained The final result of the drilling depth. Then compare the difference between the final result of the back-drilling depth and the required drilling depth, adjust the back-drilling depth to obtain the second back-drilling hole, so that the depth of the second back-drilling hole reaches the predetermined depth, that is, the required drilling depth depth. In this process, the depth of the back hole can be measured on-site. After the measurement results are obtained, the depth of the back hole can be adjusted immediately. The depth data can be directly adjusted and repeated to the optimal value on site. The traditional processing method needs to wait for the slice to be punched out. After the measurement value is fine-tuned, the slicing is repeated. If the depth has not been adjusted well, multiple slicing needs to be made, which takes a lot of time. In addition, the traditional back-drilling measurement method starts to process the holes required by the user in the back-drilling plate after adjusting the optimal depth value. It is necessary to stop the machine again to cut the first piece of the inner plate and repeat the slicing confirmation process, which is not only complicated, but also greatly reduces production. efficiency. However, the measurement method in the present application does not require slicing the back-drilling plate, and can directly obtain the depth of the back-drilling hole by measuring the depth of the semi-gel, which has the advantages of high detection efficiency, low cost and simple operation.

In one of the embodiments, the first preset value is 2.0 mm˜2.2 mm. In this embodiment, the size of the through hole is 2.0mm to 2.2mm. Within this size range, it is more suitable for the operation of the glue gun and the heating gun in the back drilling device, which is convenient for the injection of the colloid solution and the subsequent curing treatment. It is beneficial to improve the accuracy of back drilling measurement. The through-hole is smaller than the back-drilling hole, which can completely separate the colloid from the drill plate, ensure the integrity of the colloid, and improve the accuracy of subsequent back-drilling measurements.

In one of the embodiments, the second preset value is 3.0 mm˜3.2 mm. In this embodiment, the size of the back drilling is 3.0 mm to 3.2 mm. Within this size range, it is more suitable for the operation of the glue gun and the heating gun in the back drilling device, which is convenient for the injection of the colloidal solution and the subsequent curing treatment. , which is beneficial to improve the accuracy of back drill measurement.

Further, the back drill is used to process a 2.0mm through hole at the frame position of the drill plate, and the depth control part is drilled with a 3.0mm knife. The size of the hole is processed by itself, and only the depth is processed according to the user's requirements to ensure that it can be measured with a depth gauge. . The traditional back drill produces a test hole at the frame position that is consistent with the user's standard. When the hole processed by the user is small, the depth gauge cannot be used, and it must be measured by slicing. That is, after drilling the side and back of the circuit board, stop and send the sample. It takes a lot of time to go to the laboratory for slice measurement. In this application, the side and back of the circuit board are drilled, and the depth gauge can be measured directly on site after the machine is stopped, and the measurement data can be obtained intuitively. Since the 3.0mm knife is a flat drill, the chips on both sides are relatively uniform, and the depth gauge data is for reference.

In one embodiment, the colloidal solution is a silica gel solution. In this embodiment, the colloid solution is a silica gel solution, and the silica gel solution can be solidified into a colloid in a semi-gel state under the condition of heating, so as to facilitate the extraction operation of the colloid, and the solidification of the colloid to keep the colloid in the semi-gel state. The semi-solid state is convenient for subsequent measurement of the colloid and improves the accuracy of the measurement.

In order to facilitate the extraction and measurement of the colloid and improve the accuracy of the back-drilling measurement, in one embodiment, the heating temperature of the silica gel solution is 175°C to 185°C. In this embodiment, the silicone gel solution is heated to 175°C to 185°C to ensure that the silicone gel solution is solidified into a semi-gel state, which facilitates the extraction and measurement of the colloid, and can improve the accuracy of back drill measurement.

In one embodiment, before the step of curing the colloidal solution in the through-hole and the back-drilled hole, and after the step of injecting the colloidal solution into the through-hole and the back-drilled hole, respectively, the measuring method further includes the step of : Let the colloid solution stand for 3min~5min. In this embodiment, the colloidal solution is filled in the back-drilled holes and the through-holes and left to stand for 3 to 5 minutes, so that the colloidal solution can be fully diffused into the back-drilled holes and the through-holes, and the structure is the same as that of the back-drilled holes and the through-holes. The colloidal shape improves the accuracy of the back drill measurement.

In order to make the cured colloid more convenient and quick to take out and improve the efficiency and accuracy of back-drilling measurement, in one embodiment, before the steps of injecting the colloid solution into the through hole and the back-drilling hole respectively, and before the steps of injecting the circuit After the step of processing the connected through holes and the back-drilled holes on the board, the measuring method further includes: coating a grease layer on the hole walls of the through-holes and the back-drilled holes. In this embodiment, before injecting the colloidal solution, a layer of grease is applied on the surface of the back-drilled hole and the hole wall of the through hole, so that a layer of grease is formed on the surface of the back-drilled hole and the hole wall of the through hole, so that the injected The colloid solution adheres to the grease layer, and does not contact the surface of the hole wall of the back-drilled hole and the through hole, so as to avoid the colloid solution sticking to the surface of the hole wall of the back-drilled hole and the through hole after solidification, which will cause the colloid to be removed when it is taken out. damaged, thereby affecting the accuracy of the back drill measurement. At the same time, the grease layer has lubricity, which can make the colloid more convenient and quick to take out, thereby improving the efficiency and accuracy of back drilling measurement.

In order to ensure the integrity of the colloid and improve the accuracy of measurement, in one embodiment, the steps of taking out the colloid and measuring the depth and alignment of the colloid are as follows: taking out the colloid from the through hole to the back drilling , and measure the depth and alignment of the colloid. In this embodiment, when the colloid kept in the semi-gel state is taken out from the circuit board, it is separated from the drill board from the through hole to the back-drilling direction. On the drill board, the back-drilling hole is larger than the through hole, so that the colloid can be completely It is separated from the drill plate to ensure the integrity of the colloid and improve the accuracy of subsequent back drill measurements. Further, the colloid is taken out at 1mm/s～3mm/s, so that the speed of the colloid to be measured is slower from the through hole to the back drilling direction from the circuit board, so as to avoid the colloid to be measured from being damaged when it is separated from the circuit board, so that the colloid is completely intact. It is separated from the drill plate to ensure the integrity of the colloid, thereby improving the accuracy of the measurement.

In one of the embodiments, when back-drilling the circuit board, the positioning holes are drilled at one time or simultaneously drilled with the small holes that need to be back-drilled for positioning. It is understandable that if the target holes punched by X-Ray are used for positioning in both one-time drilling and back-drilling, the hole position deviation caused by the expansion and contraction of the inner layer will easily occur. The small holes are drilled and the positioning holes drilled at the same time are used for positioning, which effectively reduces the hole position deviation caused by the expansion and contraction of the inner layer.

In one embodiment, the colloidal solution is glucomannan. It can be understood that the gel forming conditions of glucomannan are simple, the off-cup is complete, the gel strength and toughness are high, and the cost is low. The glucomannan raw material is dissolved and heated to 70°C to 72°C, then the heated glucomannan solution is injected into the hole to be measured, and after cooling to room temperature, the glucomannan solution solidifies into a gel state. At room temperature, glucomannan is stably maintained in a gel state, and it is not easy to expand or shrink or change in shape. .

In one embodiment, after the curing operation of the colloid solution is completed, 1 to 2 drops of glucomannan solution are added dropwise at the junction of the colloid and the hole to be measured, left for 3min to 5min, and the orifice of the hole to be measured is scraped off. excess colloid. It can be understood that, add 1-2 drops of the heated and dissolved glucomannan solution dropwise to the junction of the colloid and the hole to be measured, and let it stand for 3min to 5min, so that the glucomannan solution can fully penetrate into the colloid and the hole to be measured. After the temperature is cooled to room temperature, it solidifies into a gel state, which ensures the consistency of the shape and structure of the colloid and the hole to be measured, and improves the accuracy of back-drilling measurement.

In one of the embodiments, the measurement method of any of the above embodiments uses the back-drilling measurement device 10 to measure the circuit board.

As shown in FIG. 2 to FIG. 3 , in one embodiment, the back drill measurement device 10 includes a glue dispensing control assembly 100 , a glue liquid accommodating member 200 , a piston member 300 , a glue dispensing assembly 400 and a measuring mechanism 500 . The glue control assembly 100 includes a mounting base 120 , a control member 130 and a fixing member 140 , the control member 130 is connected to the mounting base 120 , and the fixing member 140 is fixedly connected to the mounting base 120 ; the glue liquid accommodating member 200 is fixedly connected to the fixing member 140 , An accommodating cavity 212 is formed in the glue liquid accommodating member 200 . The piston member 300 is slidably connected to the mounting seat 120, and the piston member 300 is partially located in the accommodating cavity 212 and is slidably connected to the glue liquid accommodating member 200; The plate 430 is respectively connected with the glue gun 410 and the heating gun 420. The connecting plate 430 is also connected with the glue container 200. The glue gun 410 is communicated with the accommodating cavity 212. Gel column in gel state. The measuring mechanism 500 is used to measure the thickness and alignment of the glue column.

In this embodiment, the glue dispensing control assembly 100 in the backdrill measuring device 10 includes a mounting seat 120 , a control member 130 and a fixing member 140 , the piston member 110 is slidably connected to the mounting seat 120 , and the control member 130 is connected to the mounting seat 120 . , the fixing member 140 is fixedly connected to the mounting seat 120 . The fixing member 140 is connected to the mounting seat 120, and can support the mounting seat 120, so that the piston member 300 and the control member 130 will not interfere with the glue liquid accommodating member 200 connected under the glue dispensing control assembly 100 during the movement process. Causes pressure, which in turn affects the control of glue output. A accommodating cavity 212 is formed in the glue liquid accommodating member 200. The piston member is slidably connected to the mounting seat. The piston member is partially located in the accommodating cavity and is slidably connected with the glue liquid accommodating member. The accommodating cavity can be pushed by the piston member. The internal colloid solution is glued out.

Further, the glue dispensing assembly 400 includes a glue gun 410 , a heating gun 420 and a connecting plate 430 . The connecting plate 430 is respectively connected with the glue gun 410 and the heating gun 420 , and the connecting plate 430 is also connected with the glue container 200 . , the glue gun 410 is communicated with the accommodating cavity 212, and the heating gun 420 is used for heating the colloidal solution to form a semi-gel state glue column. The movement of the piston member 300 is controlled by the control member 130 to push the colloidal solution in the accommodating cavity 212 , and the colloidal solution is injected into the back hole through the glue gun 410 . The glue gun 410 is connected with the heating gun 420 through the connecting plate 430, that is to say, after the colloidal solution injection is completed, the colloidal solution in the back hole can be heated and solidified by the heating gun 420 at the other end of the connecting plate 430 immediately, The colloid solution is turned into a semi-gel state with a stable shape, which facilitates the extraction and measurement of the colloid from the backdrilled hole.

Further, through the measuring mechanism 500 connected to the end of the accommodating cavity 212 away from the mounting seat 120, the colloid can be measured on-site, and the depth of the colloid, that is, the depth of the back-drilling hole, can be quickly obtained. It can be understood that in the present application, the glue is injected into the back hole through the glue control assembly 100 , the glue container 200 , the piston 300 and the glue discharge assembly 400 , and the heating gun 420 in the glue discharge assembly After the glue is cured, take it out, and then use the measuring mechanism 500 to measure the cured glue to obtain the depth of the back-drilling hole. During the measurement process, there is no need to perform any processing on the circuit board. The advantage of causing damage. Since the glue dispensing assembly 400 includes a glue gun 410 and a heating gun 420, after the glue is injected into the back hole through the glue gun 410, the glue is directly cured by the heating gun 420, and then the cured glue is taken out through The measuring mechanism 500 directly measures the colloid on the spot to obtain data, quickly confirms the depth of the back-drilling hole, and greatly improves the measurement efficiency. In addition, since the back-drilling measuring device 10 of the present application measures the colloid filled in the back-drilling hole through the glue dispensing assembly 400 and the measuring mechanism 500 to obtain the back-drilling depth, while avoiding damage to the circuit board, the back-drilling is also avoided. The deviation of the measurement results caused by the unpredictability in the hole makes the measurement accuracy more accurate.

As shown in FIG. 2 to FIG. 3 , in one embodiment, the measurement mechanism 500 includes a measurement assembly 510 . The measurement assembly 510 includes a measurement fixing rod 512 , a measurement reference piece 514 and a measurement telescopic piece 516 , and the measurement reference piece 514 is connected to the measurement fixing rod 512 . The rod 512 is connected, and the measurement telescopic piece 516 is slidably arranged on the measurement fixed rod 512 . The measurement telescopic piece 516 is provided with a displacement sensor. In this embodiment, the cured glue is taken out and placed at the measurement reference member 514. At this time, the glue gun 410 and the heating gun 420 can function as positioning members. First, adjust the position of the measurement reference member 514 to the same horizontal position as the end points of the glue gun 410 and the heating gun 420, and then place the glue to be measured at the end points of the glue gun 410 and the heating gun 420 to perform Measurement. The distance value between the measurement telescopic member 516 and the measurement reference member 514 is measured by the displacement sensor, so as to obtain the thickness value and contrast value of the colloid.

In order to facilitate the control of the measuring mechanism and further improve the accuracy of back-drilling measurement, in one embodiment, the measuring mechanism 500 further includes an operation panel 520, the operation panel 520 is connected to the fixing rod 512, and the operation panel 520 is connected to the glue The accommodating member 200 is connected, and the control end of the operation panel 520 is electrically connected with the displacement sensor.

As shown in FIG. 2 to FIG. 3 , in order to avoid errors caused by manual reading and improve the accuracy of the measurement results, in one embodiment, the operation panel 520 is provided with an electronic display screen 5220, and the electronic display screen 5220 is embedded in the operation panel In 520, the electronic display screen 5220 is electrically connected to the displacement sensor, and the electronic display screen 5220 is used to display the distance value measured by the output displacement sensor, that is, the result of the colloid depth measurement, that is, the result of the back drilling depth measurement, so that the measurement The results are more intuitive and accurate, avoiding errors caused by manual readings.

As shown in FIG. 2 to FIG. 3 , in order to improve the accuracy and controllability of measurement, in one embodiment, the measurement mechanism 500 further includes a drive assembly, and the power output end of the drive assembly is connected with the measurement telescopic member 516 to The measured telescopic piece 516 is driven to slide relative to the measurement reference piece; the operation panel 520 is also provided with a start key and a stop key 5250, the start key and the stop key 5250 are both electrically connected to the drive assembly, and the start key is used to control the operation of the drive assembly, The stop key 5250 is used to control the drive assembly to stop working. Further, the start key further includes a first control key 5230 and a second control key 5240. The first control key 5230 is used to control the drive assembly to drive and measure the elongation of the telescopic member 516, and the second control key 5240 is used to control the drive assembly to drive the measurement The shortening of the telescopic member 516 further improves the accuracy and controllability of the measurement. In this embodiment, the drive assembly may be a motor drive assembly or a cylinder drive assembly.

As shown in FIG. 2 to FIG. 3 , in one embodiment, the measuring telescopic member 516 includes a measuring telescopic rod 5162 and a measuring needle 5164 , the measuring needle 5164 is fixedly connected to one end of the measuring telescopic rod 5162 , and the measuring reference member 514 is set on the measuring rod 5162 . One end of the telescopic rod 5162 away from the measurement needle 5164 is connected to the measurement reference member 514 at one end of the measurement fixed rod 512 , and the operation panel 520 is connected to the end of the measurement fixed rod 512 away from the measurement reference member 514 . In this embodiment, the cured glue is taken out and placed at the measurement reference member 514. At this time, the glue gun 410 and the heating gun 420 can function as positioning members. First, adjust the position of the measurement reference member 514 to the same horizontal position as the end points of the glue gun 410 and the heating gun 420, and then place the glue to be measured at the end points of the glue gun 410 and the heating gun 420 to perform Measurement. It can be understood that the measuring needle 5164 is fixedly connected to one end of the measuring telescopic rod 5162, and one end of the measuring telescopic rod 5162 away from the measuring needle 5164 is set on the measuring reference member 514. By adjusting the position of the telescopic rod, the measuring needle 5164 can be relative to the measuring reference. 514 is moved, that is to say, one end of the colloid to be measured is placed at the end points of the glue gun 410 and the heating gun 420, and then the measuring needle 5164 is moved to the other end of the colloid to be measured, that is, the measurement result can be obtained. The measurement device has the advantages of simple operation, high measurement efficiency, accurate measurement accuracy and no damage to the circuit board. Further, placing the heating gun 420 on the surface of the colloid during measurement can achieve the effect of heating and heat preservation, so that the colloid will not expand or shrink or change in shape at room temperature, which is beneficial to improve the measurement accuracy.

As shown in FIG. 2 , in order to control the glue output and speed of the glue gun 410 and improve the measurement accuracy of the back drill, in one embodiment, the piston member 300 includes a piston handle 310 , a piston rod 320 and a piston body 330 , the piston body 330 is connected to one end of the piston rod 320, the piston body 330 is located in the accommodating cavity 212 and is slidably connected with the glue container 200; the piston handle 310 is connected to the other end of the piston rod 320 away from the piston body 330, the piston rod 320 are respectively slidably connected to the mounting bases 120 . It can be understood that the width of the piston handle 310 is larger than the diameter of the piston rod 320, and the piston handle 310 can protect the piston rod 320 and prevent the piston rod 320 from detaching from the mounting seat 120 during the movement process, thereby affecting the glue output and output of the glue gun 410. glue speed. By controlling the piston handle 310 and the piston rod 320, the piston body 330 can be pushed to move. The piston rod 320 is slidably connected to the mounting seat 120 , and the control member 130 is connected to the piston rod 320 through the mounting seat 120 , and the movement range and speed of the piston rod 320 can be controlled by the control member 130 , thereby controlling the glue output and the speed of the glue gun 410 . The glue output speed makes the colloidal solution more tightly packed in the back drilling, improving the measurement accuracy of the back drilling.

Further, in order to more accurately control the amount of glue and the speed of glue dispensing from the glue gun 410 and improve the measurement accuracy of the back drill, the outer wall of the accommodating cavity 212 in the glue accommodating member 200 is the outer wall of the transparent cavity, and the transparent cavity The outer wall is provided with a scale line, and the numerical value on the scale line represents the volume of the colloidal solution in the accommodating cavity. The glue output of the glue gun 410 can be intuitively obtained through the scale value in the scale line, so that the glue output and glue speed of the glue gun 410 can be controlled more accurately, and the measurement accuracy of the back drill can be improved.

In order to more accurately control the glue output and speed of the glue gun 410 and improve the measurement accuracy of the back drill, in one embodiment, the control member 130 includes a control rod 1320 , a gear and a rack. The control rod 1320 is rotatably connected to the mounting seat 120 , the gear is sleeved on the rotating shaft, and the gear is meshed with the rack for transmission. The rack is arranged on the piston rod. It can be understood that the length direction of the rack is parallel to the axial direction of the piston rod. When the control rod is rotated, the control rod 1320 drives the gear to rotate, so that the gear and the rack are engaged for transmission, thereby driving the piston rod 320 to slide relative to the mounting seat 120 . In this embodiment, when the control rod is rotated clockwise, the control piston rod 320 slides in a direction away from the glue gun 410; when the control rod is rotated counterclockwise, the control piston rod 320 is controlled to move closer to the glue gun 410. The liquid gun 410 slides in the direction of movement. In this way, the movement and displacement of the piston rod 320 can be accurately controlled by the control rod, thereby controlling the glue output of the glue gun 410 and improving the measurement accuracy of the back drill.

In one embodiment, the glue liquid accommodating member 200 includes a accommodating body 210 and a accommodating cover 220. One end of the accommodating body 210 close to the mounting base 120 is fixedly connected to the fixing member 140, and the accommodating cavity 212 is opened in the accommodating body. 210 , the accommodating cover 220 covers the accommodating body 210 , the piston member 300 slides through the accommodating cover 220 , and the piston member 300 is partially located in the accommodating cavity 212 and is slidably connected with the accommodating body 210 .

As shown in FIG. 2 to FIG. 3 , in order to improve the accuracy of the back drill measurement, in one embodiment, the glue gun 410 includes a fixing part 4120 and a glue gun main body 4130 , and the fixing part 4120 is connected to the connecting plate 430 and the glue gun respectively. The liquid container 200 is connected, the fixing part 4120 is provided with a first glue discharge hole, the first glue discharge hole is communicated with the accommodating cavity 212, and the glue gun main body 4130 is provided with a second glue discharge hole communicated with the first glue discharge hole .

In this embodiment, the glue gun 410 includes a fixing part 4120 and a glue gun main body 4130, wherein the glue gun main body 4130 has a needle-like structure. It can be understood that the back hole is generally small, and needle-like glue is used. The gun 410 facilitates the injection of the colloid solution into the back-drilled hole more precisely, while improving the alignment of the colloid. The fixing portion 4120 is cylindrical or prismatic, and the diameter and width of the fixing portion 4120 are much larger than that of the glue gun main body 4130. The fixing portion 4120 is respectively connected to the connecting plate 430 and the glue container 200, and the fixing portion 4120 is provided with a first glue row. The first row of glue holes communicates with the accommodating cavity 212, and the glue gun main body 4130 is provided with a second row of glue holes that communicate with the first row of glue holes, so that the glue gun main body 4130 is more stable during the glue dispensing process. Ensure the stability of the glue injection, ensure the complete fit of the glue and the shape of the back drilling, and improve the accuracy of the back drilling measurement.

As shown in FIGS. 2 to 3 , in one embodiment, the heating gun 420 includes a heat generating part 4220 and a heating part 4230 , the heating part 4230 is fixedly connected to one end of the heat generating part 4220 , and the heat generating part 4220 is far away from the heating part 4230 One end is connected to the connecting plate 430 . In this embodiment, the heating gun 420 transfers the heat generated by the heat generating part 4220 to the colloidal solution through the heating part 4230 , because the heat generated by the heat generating part 4220 is relatively concentrated and the temperature is not easy to control, and the temperature changes after passing through the heating part 4230 It is more uniform and more suitable for the curing temperature of the colloid, so that the heating temperature of the colloid solution is more uniform, and the curing and forming effect is better, which is conducive to improving the accuracy of the measurement.

The present application also provides a circuit board, and the circuit board is measured by using the measurement method in any of the above embodiments.

As shown in FIG. 4 , in one embodiment, the circuit board 60 includes a backing plate 620 , a PCB copper plate 630 , an aluminum sheet 640 and an insulating plate 650 . The PCB copper plate 630 is laminated on the backing plate 620 , the aluminum sheet 640 is laminated on the PCB copper plate 630 , and the insulating plate 650 is laminated on the aluminum sheet 640 . Further, the thickness of the insulating plate 650 is 0.4 mm˜0.6 mm, and the insulating plate 650 is a flat insulating plate 650 which is closely attached to the aluminum plate. The above circuit board is the circuit board before drilling. By setting an insulating plate 650 above the aluminum plate, the drilling chips can be cleaned up during the cutting process, thereby reducing the influence of the swarf wire on the conductivity and the accuracy of the back drilling, ensuring that the The cleanliness of the drill bit ensures the drilling quality and improves the drilling accuracy.

As shown in FIG. 5 , in one embodiment, the circuit board 70 includes a circuit board body 710 , and a signal layer 720 , a power supply ground layer 730 and a preset safety distance layer 740 respectively disposed in the circuit board body 710 . Through holes 712 is opened adjacent to the signal layer 710 , the back hole 714 is opened adjacent to the power ground layer 730 , the preset safety distance layer 740 is electrically connected to the signal layer 710 , and the preset safety distance layer 740 is disconnected from the power ground layer 730 through the back hole 714 . The above-mentioned circuit board is a circuit board after drilling, and the circuit board includes a signal layer 720, a power ground layer 730 and a preset safety distance layer 740. The signal layer 720 is used for arranging the wires on the circuit board, and the power ground layer 730 is used for arranging the power supply wire and ground wire, because the subsequent process will electrolyze a small part of the copper, so set a preset safety distance.

In one embodiment, the preset safety distance is 40 μm˜100 μm. In this embodiment, since a small part of copper will be electrolyzed in the subsequent process, a preset safety distance is set. stability.

Example 1

Put the silicone gel solution into the glue injection gun in the back drill measurement device. Before injecting the silicone gel solution, coat a layer of grease on the surface of the hole wall of the hole to be measured, and inject the colloidal solution into the circuit board through the glue gun. In the hole to be measured, let stand for 3 minutes until the colloidal solution completely fills the hole to be measured. Put the heat gun into the hole to be measured to heat the silicon gel solution, and the heating temperature is 175°C. When the silicon gel solution is solidified to a semi-gel state, the heating is stopped. After the silicone gel is cooled, it is taken out from the hole to be measured and the length and alignment of the silicone gel are measured. The measurement of the length of the silicone gel includes the part of the silicone gel corresponding to the back-drilled shape structure, Corresponding to the length of the part of the through-hole shape structure and the overall length of the silicone gel, the value a1 of the measurement result of the part of the back-drilled structure in the silicone gel is the depth of the back-drilling hole, and the length c1 of the whole silicone gel is subtracted from the value of c1 The value of the length b1 of the part of the silicone gel corresponding to the through-hole shape structure can be checked against the measurement result of the part corresponding to the back-drilled hole shape structure. If the measured depth of the back-drilling hole is less than the depth required to be drilled in advance, continue back-drilling according to the measurement result, and repeat the above steps to measure the back-drilling hole depth after the back-drilling is completed. Until the back-drilling depth reaches the pre-required drilling depth.

Example 2

Put the silicone gel solution into the glue injection gun in the back drill measurement device. Before injecting the silicone gel solution, coat a layer of grease on the surface of the hole wall of the hole to be measured, and inject the colloidal solution into the circuit board through the glue gun. In the hole to be measured, let stand for 5 minutes until the colloidal solution completely fills the hole to be measured. Put the heat gun into the hole to be measured to heat the silicon gel solution, the heating temperature is 185°C, and stop heating when the silicon gel solution is solidified to a semi-gel state. After the silicone gel is cooled, it is taken out from the hole to be measured and the length and alignment of the silicone gel are measured. The measurement of the length of the silicone gel includes the part of the silicone gel corresponding to the back-drilled shape structure, Corresponding to the length of the part of the through-hole shape structure and the whole of the silicone gel, the measurement result a2 value of the part of the back-drilled shape structure in the silicone gel is the depth of the back-drilling hole, and the length c2 of the whole silicone gel is subtracted from the value of c2 The value of the length b2 of the part of the silicone gel corresponding to the through-hole shape structure can be checked on the measurement result of the part corresponding to the back-drilled hole shape structure. If the measured depth of the back-drilling hole is less than the depth required to be drilled in advance, continue back-drilling according to the measurement result, and repeat the above steps to measure the back-drilling hole depth after the back-drilling is completed. Until the back-drilling depth reaches the pre-required drilling depth.

Example 3

Put the silicone gel solution into the glue injection gun in the back drill measurement device. Before injecting the silicone gel solution, coat a layer of grease on the surface of the hole wall of the hole to be measured, and inject the colloidal solution into the circuit board through the glue gun. In the hole to be measured, let stand for 4 minutes until the colloidal solution completely fills the hole to be measured. Put the heat gun into the hole to be measured to heat the silicon gel solution, the heating temperature is 180°C, and stop the heating when the silicon gel solution is solidified to a semi-gel state. After the silicone gel is cooled, it is taken out from the hole to be measured and the length and alignment of the silicone gel are measured. The measurement of the length of the silicone gel includes the part of the silicone gel corresponding to the back-drilled shape structure, Corresponding to the length of the part of the through-hole shape structure and the whole of the silicone gel, the measurement result a3 value of the part of the back-drilled shape structure in the silicone gel is the depth of the back-drilling hole, and the length c3 of the whole silicone gel is subtracted from the value of c3 The value of the length b3 of the part of the silicone gel corresponding to the through-hole shape structure can be checked on the measurement result of the part corresponding to the back-drilled hole shape structure. If the measured depth of the back-drilling hole is less than the depth required to be drilled in advance, continue back-drilling according to the measurement result, and repeat the above steps to measure the back-drilling hole depth after the back-drilling is completed. Until the back-drilling depth reaches the pre-required drilling depth.

Example 4

Heat the glucomannan solution to 70°C, put the heated glucomannan solution into the glue injection gun in the back-drilling measuring device, and coat the surface of the hole wall of the hole to be measured before injecting the glucomannan solution. Layer grease, inject the colloidal solution into the hole to be measured on the circuit board through a glue gun, and let it stand for 5 minutes until the colloidal solution completely fills the hole to be measured. After the glucomannan is cooled, it is taken out from the hole to be measured and the length of the glucomannan and the alignment degree are measured. Corresponding to the length of the part of the through-hole shape structure and the overall length of the glucomannan, the measurement result a2 value of the part of the back-drilled structure in the glucomannan is the depth of the back-drilled hole, and the c2 value of the overall length of the glucomannan is subtracted. The value of the length b2 of the part of the glucomannan corresponding to the through-hole shape structure can be checked on the measurement result of the part corresponding to the back-drilled hole shape structure. If the measured depth of the back-drilling hole is less than the depth required to be drilled in advance, continue back-drilling according to the measurement result, and repeat the above steps to measure the back-drilling hole depth after the back-drilling is completed. Until the back-drilling depth reaches the pre-required drilling depth.

Example 5

The glucomannan solution was heated to 72°C, and the heated glucomannan solution was loaded into the glue injection gun in the back-drilling measuring device. Before injecting the glucomannan solution, coat the surface of the hole wall of the hole to be measured Layer grease, inject the colloidal solution into the hole to be measured on the circuit board through a glue gun, and let it stand for 5 minutes until the colloidal solution completely fills the hole to be measured. After the glucomannan is cooled, it is taken out from the hole to be measured and the length of the glucomannan and the alignment degree are measured. Corresponding to the length of the part of the through-hole shape structure and the overall length of the glucomannan, the measurement result a2 value of the part of the back-drilled structure in the glucomannan is the depth of the back-drilled hole, and the c2 value of the overall length of the glucomannan is subtracted. The value of the length b2 of the part of the glucomannan corresponding to the through-hole shape structure can be checked on the measurement result of the part corresponding to the back-drilled hole shape structure. If the measured depth of the back-drilling hole is less than the depth required to be drilled in advance, continue back-drilling according to the measurement result, and repeat the above steps to measure the back-drilling hole depth after the back-drilling is completed. Until the back-drilling depth reaches the pre-required drilling depth.

Example 6

Heat the glucomannan solution to 71°C, put the heated glucomannan solution into the glue injection gun in the back-drilling measuring device, and coat the surface of the hole wall of the hole to be measured before injecting the glucomannan solution. layer grease, inject the colloidal solution into the hole to be measured on the circuit board through a glue gun, and let it stand for 5 minutes until the colloidal solution completely fills the hole to be measured. After the glucomannan is cooled, it is taken out from the hole to be measured and the length of the glucomannan and the degree of alignment are measured, and the measurement of the length of the glucomannan includes the part corresponding to the back-drilled shape structure in the glucomannan, Corresponding to the length of the part of the through-hole shape structure and the overall length of the glucomannan, the measurement result a2 value of the part of the back-drilled shape structure in the glucomannan is the depth of the back-drilled hole, and the overall length of the glucomannan The c2 value is subtracted The value of the length b2 of the part of the glucomannan corresponding to the through-hole shape structure can be checked on the measurement result of the part corresponding to the back-drilled hole shape structure. If the measured depth of the back-drilling hole is less than the depth required to be drilled in advance, continue back-drilling according to the measurement result, and repeat the above steps to measure the depth of the back-drilling hole after the back-drilling is completed. Until the back-drilling depth reaches the pre-required drilling depth.

In the measurement method of the present invention, the colloidal solution is injected into the back-drilled hole to be measured after the back-drilling, and the colloidal solution is solidified into a semi-gel state through a curing operation, and then the semi-gel is taken out from the to-be-measured hole. The back-drilling measuring device measures the depth of the half-gel corresponding to the back-drilling hole, and the obtained measurement result is the depth of the hole to be measured. The operation method is simple, the measurement efficiency is high, and the circuit board is not damaged. Different from the traditional method of changing the compensation through the trial drilling value, the compensation is changed by slicing. During the process, the machine needs to wait for the slicing result before the compensation can be produced, which consumes a lot of time and personnel energy. The method adopted in the present invention does not require slicing the drill plate, and can directly obtain the depth of the back-drilled hole by measuring the depth of the semi-gel, and has the advantages of high detection efficiency, low cost and simple operation mode.

The above examples only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

A measurement method for measuring a circuit board, characterized in that the measurement method comprises the following steps:

The circuit board is processed into a through hole and a back hole that are connected to each other, wherein the hole diameter of the through hole is a first preset value, the hole diameter of the back hole is a second preset value, and the first The preset value is smaller than the second preset value;

injecting the colloidal solution into the through hole and the back-drilled hole respectively, so that the through-hole and the back-drilled hole are completely filled with the colloidal solution;

performing a solidification treatment operation on the colloidal solution in the through hole and the back-drilled hole, so that the colloidal solution in the through-hole and the back-drilled hole forms a colloid in a semi-gel state;

Scraping off the excess colloid on the edge of the through hole and the back-drilled hole;

The colloid is taken out, and the depth and alignment degree of the colloid is measured to obtain the depth value and alignment degree value of the colloid.
The measurement method according to claim 1, wherein the first preset value is 2.0 mm˜2.2 mm.
The measuring method according to claim 1, wherein the second preset value is 3.0 mm˜3.2 mm.
The measuring method according to claim 1, wherein the colloidal solution is a silica gel solution.
The measurement method according to claim 1, characterized in that before the step of curing the colloidal solution in the through hole and the back-drilled hole, the colloidal solution is injected into the through holes respectively. After the steps in the through hole and the back drilling, the measurement method further includes the steps:

The colloidal solution was allowed to stand for 3 min to 5 min.
The measuring method according to claim 1, characterized in that, before the steps of injecting the colloidal solution into the through hole and the back-drilling hole, respectively, and before processing the circuit board into the through hole and the connected through hole. After the step of back drilling, the measuring method further includes:

A grease layer is coated on the hole walls of the through hole and the back-drilled hole.
The measuring method according to claim 1, wherein the steps of taking out the colloid and measuring the depth and alignment of the colloid are as follows:

The colloid is taken out from the through hole to the back-drilled hole, and the depth and alignment of the colloid are measured.
A circuit board, characterized in that, the circuit board is measured by using the measurement method according to any one of claims 1 to 7.
The circuit board according to claim 8, wherein the circuit board comprises a circuit board body, and a signal layer, a power grounding layer and a preset safety distance layer respectively disposed in the circuit board body, and the communication A hole is opened adjacent to the signal layer, the back hole is opened adjacent to the power ground layer, the preset safety distance layer is electrically connected to the signal layer, and the preset safety distance layer is connected to the back hole through the back hole. The ground power plane is disconnected.
The circuit board according to claim 9, wherein the thickness of the preset safety distance layer is 40 μm˜100 μm.