A drilling method for embedded copper block PCB and a PCB with drilled holes

Abstract

This invention relates to a drilling method for a PCB board with embedded copper blocks and a PCB board with drilled holes. The drilling method includes: obtaining a PCB board with embedded copper blocks; forming holes in the L1-Lm layers at a drilling speed v1; drilling holes in the Lm-Ln layers at a drilling speed v2 using a pecking drill; forming holes in the Ln-Ln+a layers at a drilling speed v1; drilling holes in the Ln+a-Lp layers at a drilling speed v2 using a pecking drill; forming holes in the Lp-Lq layers at a drilling speed v1; where v1 > v2; a FANUC drill is used for drilling with external cooling; the center lines of each hole are on the same straight line; and the distance from the edge of the formed hole to the edge of the embedded copper block is 40 mil - 1 mm. This drilling method can avoid the PP cracking of the gap between the embedded copper block and the substrate, ensure the smooth discharge of copper chips, and improve processing efficiency.

Description

Technical Field

[0001] This invention belongs to the field of printed circuit board technology, specifically relating to a drilling method for a copper-embedded PCB board and a PCB board with drilled holes. Background Technology

[0002] With the rapid development of artificial intelligence (AI) computing power and the iteration of power supply architecture, the computing power and power consumption of computing units have soared simultaneously. The traditional method of using multiple thick copper cores for power supply heat dissipation and current flow design can no longer meet the performance requirements of products. Therefore, new printed circuit board designs adopt buried copper block structures to adapt to product performance needs. However, buried copper block PCBs have the following problems during the manufacturing process: 1. For embedded copper blocks with a thickness of 3.5mm, the heat conduction speed is fast. During the processing, the friction between the drill bit and the copper block will generate high temperature. When using conventional PCB drilling machines and conventional cooling methods, the drill bit cannot be cooled in time. In addition, due to the large thickness of the copper block, the drill bit needs to continuously cut the copper block, which will cause the drill bit and the embedded copper block to fuse together, ultimately causing equipment failure, resulting in processing interruption and product scrap.

[0003] 2. For embedded copper blocks with a thickness of 7mm, the difficulty of chip removal and heat dissipation during the processing far exceeds the carrying capacity of conventional PCB drilling machines. Conventional PCB drilling machines cannot complete the processing of embedded copper blocks of this thickness, and special drilling machines must be used, which not only increases the processing cost, but also limits the versatility of the processing.

[0004] 3. Some embedded copper blocks have a small diameter structure. When drilling a hole in the center of the embedded copper block, the distance between the hole and the edge of the embedded copper block is small. At the same time, there is a very small gap at the joint between the embedded copper block and the core, which is filled with PP glue. During the drilling process, the cutting force generated by the process is too large, which can easily cause cracks in the gap at the joint between the embedded copper block and the core, reducing the product qualification rate.

[0005] Therefore, there is an urgent need to develop a technical solution that can solve the above-mentioned processing problems. Summary of the Invention

[0006] The purpose of this invention is to provide a drilling method for a copper-embedded PCB board and a PCB board with drilled holes. This drilling method can prevent the PP adhesive at the junction of the copper-embedded block and the substrate from cracking, thus effectively improving product quality.

[0007] This invention provides the following technical solution: On one hand, the present invention provides a drilling method for a copper-embedded PCB board, the drilling method comprising: S1. Obtain a PCB board, wherein the PCB board includes, from top to bottom, layers L1-Lm, Lm-Ln, Ln-Ln+a, Ln+a-Lp, and Lp-Lq, wherein embedded copper blocks are provided in layers Lm-Ln and Ln+a-Lp respectively. S2. Form the first borehole in the L1-Lm layer at a drilling speed v1; S3. In the Lm-Ln layer, a second borehole is formed by a pecking drill at a drilling speed of v2. S4. Form the third borehole in the Ln-Ln+a layer at a drilling speed of v1; S5. In the Ln+a-Lp layer, a fourth borehole is formed by a pecking drill at a drilling speed of v2. S6. Form the fifth borehole in the Lp-Lq layer at a drilling speed of v1; Where v1>v2; FANUC drilling machine is used for drilling and external cooling is used for cooling. The center lines of the first, second, third, fourth and fifth drill holes are on the same straight line, and the distance from the edge of the drill hole to the edge of the buried copper block is 40mil-1mm.

[0008] Specifically, a FANUC drilling rig with external spindle cooling is used. If internal cooling is used, copper shavings will stick to the hole wall when drilling the embedded copper block, requiring pre-drilling, hole enlargement to remove copper shavings, and finishing the hole three times. With external cooling, the drill bit is quickly cooled with cutting fluid after cutting the copper shavings, which quickly removes the copper slag from the hole, reducing the number of times the same hole needs to be drilled and greatly improving efficiency.

[0009] In the above technical solution, by adopting a segmented drilling method, a higher drilling speed is used in the part without embedded copper blocks, and a pecking drilling method is used and the drilling speed is reduced in the part with embedded copper blocks. In conjunction with a FANUC drilling machine and external cooling cutting fluid, the heat generated by the drill bit cutting the substrate and embedded copper blocks can be dissipated in time, avoiding the PP cracking of the gap between the embedded copper blocks and the substrate, ensuring the smooth discharge of copper chips and improving processing efficiency.

[0010] Furthermore, the drill bit used during drilling is a two-flute drill bit with a wide chip removal groove, made of cemented carbide tungsten steel as the base and with a diamond coating on the surface, and the drill tip angle is 118°.

[0011] In the above technical solution, the diamond coating can reduce the coefficient of friction with copper, inhibit the adhesion of copper chips to form built-up edge, reduce cutting resistance and processing temperature rise, while improving the wear resistance and overall rigidity of the drill bit surface, reducing the risk of drill bit breakage, improving chip removal effect and drilling hole wall quality; the drill tip angle is 118°, the cutting edge is sharper, and the extrusion deformation of the copper layer is reduced.

[0012] Furthermore, the cutting fluid used during drilling is a water-based emulsified cutting fluid.

[0013] In the above technical solution, the water-based emulsified cutting fluid has excellent cooling and heat dissipation, lubrication and friction reduction and chip removal capabilities. It can quickly remove the high temperature generated by the drill bit cutting the copper block, inhibit the copper chips from adhering to the drill bit surface, and avoid high temperature welding between the drill bit and the copper block and spindle jamming. At the same time, it is compatible with the characteristics of printed circuit board substrates, will not corrode the copper layer and resin substrate, and has good processing safety and board surface compatibility.

[0014] Furthermore, the temperature of the cutting fluid is 20-30℃, the injection pressure is 0.4-0.6MPa, the flow rate is 10-15L / min, and the cutting fluid is sprayed at a 45° injection angle towards the orifice.

[0015] If the cutting fluid temperature is too high, it will reduce the viscosity of the coolant, affecting the lubrication / chip removal effect, and at the same time aggravating the thermal deformation of the resin layer; if the water flow and pressure are too low, the copper chips will get stuck in the chip removal groove; in addition, aiming the nozzle at the orifice so that the water flow directly impacts the cutting area can achieve a better cooling effect.

[0016] In the above technical solution, by setting the temperature, pressure, and flow rate of the cutting fluid in conjunction with setting the spray position, heat can be dissipated in a timely manner and copper chips can be smoothly discharged.

[0017] Furthermore, v2 = (0.4-0.6)v1, v1 = 200 mm / min.

[0018] In the above technical solution, by setting the drilling speed v1 to 200mm / min, the cutting temperature rise of the part without the embedded copper block can be reduced; while setting v2 can reduce the cutting temperature rise of the embedded copper block, effectively reduce the probability of cracking of the PP adhesive in the gap between the embedded copper block and the substrate, and at the same time reduce the frictional heat generated by the drill bit and thick copper, preventing high temperature sticking and spindle jamming.

[0019] Furthermore, the pecking drill is performed using the G83 chip-breaking cycle, and the single feed distance of the pecking drill is 0.5mm.

[0020] In the above technical solution, the copper chips are effectively broken by small-step segmented drilling, and the intermittent tool lifting facilitates the discharge of copper chips in the hole, reducing the blockage of the chip removal groove and the accumulation of chips. At the same time, the single continuous cutting stroke is shortened, the cutting temperature rise and heat accumulation are reduced, and the cutting impact is reduced, effectively reducing the probability of cracking of the PP adhesive in the gap between the embedded copper block and the substrate, and effectively improving product quality.

[0021] On the other hand, the present invention provides a PCB board with drilled holes, which is prepared by the drilling method described above.

[0022] The PCB board with drilled holes prepared by the above method can avoid cracking of the PP adhesive at the junction of the embedded copper block and the substrate, effectively improving product quality.

[0023] The present invention has the following beneficial effects: The drilling method for embedded copper block PCBs of the present invention adopts a segmented drilling approach. In the part without embedded copper block, a conventional drilling speed is used, while in the part with embedded copper block, a pecking drilling method is used and the drilling speed is reduced. In conjunction with a FANUC drilling machine and external cooling cutting fluid, the heat generated by the drill bit cutting the substrate and embedded copper block can be dissipated in time, avoiding the PP cracking of the gap between the embedded copper block and the substrate, ensuring the smooth discharge of copper chips and improving processing efficiency. Attached Figure Description

[0024] Figure 1 A schematic diagram of the PCB board structure obtained by the method provided in the embodiments of this application. Detailed Implementation

[0025] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0028] A drilling method for a copper-embedded PCB board, the drilling method comprising: S1. Obtain a PCB board, wherein the PCB board includes, from top to bottom, layers L1-Lm, Lm-Ln, Ln-Ln+a, Ln+a-Lp, and Lp-Lq, wherein embedded copper blocks are provided in layers Lm-Ln and Ln+a-Lp respectively. S2. Form the first borehole in the L1-Lm layer at a drilling speed v1; S3. In the Lm-Ln layer, a second borehole is formed by a pecking drill at a drilling speed of v2. S4. Form the third borehole in the Ln-Ln+a layer at a drilling speed of v1; S5. In the Ln+a-Lp layer, a fourth borehole is formed by a pecking drill at a drilling speed of v2. S6. Form the fifth borehole in the Lp-Lq layer at a drilling speed of v1; Where v1>v2; FANUC drilling machine is used for drilling and external cooling is used for cooling. The center lines of the first, second, third, fourth and fifth drill holes are on the same straight line, and the distance from the edge of the drill hole to the edge of the buried copper block is 40mil-1mm.

[0029] Reference Appendix Figure 1 Taking a 14-layer PCB as an example, the specific steps are as follows: S1. Obtain a PCB board, wherein the PCB board includes layers L1-L4, L4-L7, L7-L8, L8-L11, and L11-L14 from top to bottom, wherein embedded copper blocks are provided in layers L4-L7 and L8-L11 respectively. Figure 1 The PCB board shown has a total thickness of 8.57 mm. The thickness of layers L1-L4 is 0.66 mm, the thickness of layers L4-L7 is 3.5 mm, the thickness of layers L7-L8 is 0.25 mm, the thickness of layers L8-L11 is 3.5 mm, and the thickness of layers L11-L14 is 0.66 mm. The thickness of the first and second embedded copper blocks is 3.5 mm, and the diameter is 4.85 mm. Specifically, it can be understood that the layers L1-L14 are bonded together with PP adhesive. The first embedded copper block is embedded in layers L4-L7, and the second embedded copper block is embedded in layers L8-L11. There is a 2 mil wide gap between the side of the embedded copper block and the corresponding substrate, and the gap is filled with PP adhesive.

[0030] S2. Form the first borehole in layers L1-L4 at a drilling speed v1; Specifically, the drilling depth range for layers L1-L4 is 0-0.66 mm, the drilling speed v1 is 200 mm / min, the diameter of the first drill hole is 2.85 mm, and the distance from the edge of the first drill hole to the edge of the embedded copper block is 1 mm. Using a drilling speed of 200 mm / min can reduce the cutting temperature rise in the parts excluding the embedded copper block.

[0031] S3. In layers L4-L7, a second borehole is formed by a pecking motion at a drilling speed v2.

[0032] Specifically, the drilling depth range for layers L4-L7 is 0.66-4.16 mm, the drilling speed v2 is 100 mm / min, and the chip-breaking drilling uses the G83 chip-breaking cycle. The single feed distance is 0.5 mm, and the retraction distance is 1 mm above the plate surface. The diameter of the second drill hole is 2.85 mm, and the distance from the edge of the second drill hole to the edge of the embedded copper block is 1 mm. Using a drilling speed of 100 mm / min can reduce the cutting temperature rise of the embedded copper block, effectively reduce the probability of cracking of the PP adhesive in the gap between the embedded copper block and the substrate, and at the same time reduce the heat generated by friction between the drill bit and the thick copper, preventing high-temperature sticking and spindle jamming.

[0033] S4. Form a third borehole in layers L7-L8 at a drilling speed v1.

[0034] Specifically, the drilling depth of layers L7-L8 ranges from 4.16 to 4.41 mm, the drilling speed v1 is 200 mm / min, the diameter of the third drill hole is 2.85 mm, and the distance from the edge of the third drill hole to the edge of the embedded copper block is 1 mm. Using a drilling speed of 200 mm / min can reduce the cutting temperature rise in the parts without the embedded copper block, achieve a rapid transition, and reduce steps.

[0035] S5. In layers L8-L11, a fourth borehole is formed by a pecking motion at a drilling speed v2.

[0036] Specifically, the drilling depth range for layers L8-L11 is 4.41-7.91 mm, the drilling speed v2 is 100 mm / min, and the chip-breaking drilling uses the G83 chip-breaking cycle. The single feed distance is 0.5 mm, and the retraction distance is 1 mm above the plate surface. The diameter of the fourth drill hole is 2.85 mm, and the distance from the edge of the fourth drill hole to the edge of the embedded copper block is 1 mm. Using a drilling speed of 100 mm / min can reduce the cutting temperature rise of the embedded copper block, effectively reduce the probability of cracking of the PP adhesive in the bonding gap between the embedded copper block and the substrate, and at the same time reduce the frictional heat generated by the drill bit and thick copper, preventing high-temperature sticking and spindle jamming.

[0037] S6. Form the fifth borehole in layers L11-L14 at a drilling speed v1.

[0038] Specifically, the drilling depth of layers L11-L14 ranges from 7.91 to 8.57 mm, the drilling speed v1 is 200 mm / min, the diameter of the fifth drill hole is 2.85 mm, and the distance from the edge of the fifth drill hole to the edge of the embedded copper block is 1 mm. Using a drilling speed of 200 mm / min can reduce the cutting temperature rise of the parts excluding the embedded copper block, achieve smooth drilling through, and avoid burrs and flash on the base plate.

[0039] It is understandable that the centerlines of the first, second, third, fourth, and fifth boreholes are on the same straight line.

[0040] In steps S2-S6, a FANUC drilling machine with external spindle cooling is used for drilling, and the temperature is reduced by external cooling. After the drill bit cuts the copper chips, it is quickly cooled with lubricating fluid to quickly remove the copper slag from the hole, reducing the number of times the same hole is drilled and greatly improving efficiency.

[0041] In steps S2-S6, the drill bit used during drilling is a two-edged, wide chip flute drill bit with a diamond coating on the surface, made of cemented carbide tungsten steel as the base. The drill tip angle is 118° and the diameter is 2.85mm. The diamond coating can reduce the coefficient of friction with the copper material, inhibit the adhesion of copper chips to form built-up edge, reduce cutting resistance and processing temperature rise, and at the same time improve the wear resistance and overall rigidity of the drill bit surface, reduce the risk of drill bit breakage, and improve chip removal effect and hole wall quality. The drill tip angle of 118° makes the cutting edge sharper and reduces the extrusion deformation of the copper layer.

[0042] In steps S2-S6, a dedicated water-based emulsified cutting fluid is used. The cutting fluid temperature is 25°C, the injection pressure is 0.5MPa, and the flow rate is 12L / min. The cutting fluid is sprayed at a 45° angle directly at the orifice. Because water-based emulsified cutting fluid possesses excellent cooling, lubrication, friction reduction, and chip removal capabilities, it can quickly remove the high temperatures generated by the drill bit cutting the embedded copper block, inhibiting copper chips from adhering to the drill bit surface and preventing high-temperature welding between the drill bit and the embedded copper block, as well as spindle jamming. Simultaneously, it is compatible with the characteristics of printed circuit board substrates, will not corrode the copper layer and resin substrate, and offers good processing safety and board surface compatibility. By setting the cutting fluid temperature, pressure, and flow rate in conjunction with the spray position, timely heat dissipation and smooth removal of copper chips can be promoted.

[0043] Reference Appendix Figure 1 The present invention provides a PCB board with drilled holes, which is prepared by the drilling method described above.

[0044] Although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above exemplary embodiments are merely illustrative and are not intended to limit the scope of this application. Various changes and modifications can be made therein by those skilled in the art without departing from the scope and spirit of this application. All such changes and modifications are intended to be included within the scope of this application as claimed in the appended claims.

[0045] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0046] Although the description of this application has been made in conjunction with the specific embodiments described above, it will be apparent to those skilled in the art that many substitutions, modifications, and variations can be made based on the foregoing. Therefore, all such substitutions, modifications, and variations are included within the spirit and scope of the appended claims.

Claims

1. A drilling method for a copper-embedded PCB board, characterized in that, The drilling method includes: S1. Obtain a PCB board, wherein the PCB board includes, from top to bottom, layers L1-Lm, Lm-Ln, Ln-Ln+a, Ln+a-Lp, and Lp-Lq, wherein embedded copper blocks are provided in layers Lm-Ln and Ln+a-Lp respectively. S2. Form the first borehole in the L1-Lm layer at a drilling speed v1; S3. In the Lm-Ln layer, a second borehole is formed by a pecking drill at a drilling speed of v2. S4. Form the third borehole in the Ln-Ln+a layer at a drilling speed of v1; S5. In the Ln+a-Lp layer, a fourth borehole is formed by a pecking drill at a drilling speed of v2. S6. Form the fifth borehole in the Lp-Lq layer at a drilling speed of v1; Where v1>v2; FANUC drilling machine is used for drilling and external cooling is used for cooling. The center lines of the first, second, third, fourth and fifth drill holes are on the same straight line, and the distance from the edge of the drill hole to the edge of the buried copper block is 40mil-1mm.

2. The drilling method according to claim 1, characterized in that, The drill bit used for drilling is a two-flute drill bit with a wide chip flute, made of cemented carbide tungsten steel as the base and diamond coating on the surface, with a drill tip angle of 118°.

3. The drilling method according to claim 1, characterized in that, The cutting fluid used during drilling is a water-based emulsion cutting fluid.

4. The drilling method according to claim 3, characterized in that, The cutting fluid has a temperature of 20-30℃, a spray pressure of 0.4-0.6MPa, a flow rate of 10-15L / min, and is sprayed at a 45° angle towards the orifice.

5. The drilling method according to claim 1, characterized in that, The value of v2 is (0.4-0.6)v1, where v1 = 200 mm / min.

6. The drilling method according to claim 1, characterized in that, The pecking drill is performed using the G83 chip-breaking cycle, and the single feed distance of the pecking drill is 0.5mm.

7. A PCB board with drilled holes, characterized in that, The PCB board with drilled holes is manufactured using the drilling method described in any one of claims 1-6.

Images