A processing method of a core board laminated printed wiring board

Abstract

The present application relates to a kind of core plate laminated printed wiring board processing method, comprising the following steps: S1, provide intermediate core plate, the thickness of intermediate core plate is greater than the limit punching thickness of drilling equipment;S2, at the position of intermediate core plate pre-set, from one surface of intermediate core plate, depth control drilling is carried out, and the thickness of the position is reduced to below limit punching thickness;S3, using punching equipment to the position after thinning is punched, forms first rivet hole;S4, provide first outer layer core plate and second outer layer core plate, and respectively punch out corresponding second rivet hole;S5, obtain the expansion and contraction value of intermediate core plate, first outer layer core plate and second outer layer core plate, select a group of expansion and contraction value difference to meet preset range as pressing unit;S6, first outer layer core plate, intermediate core plate and second outer layer core plate in the same pressing unit are sequentially stacked after pressing.The present application can satisfy the rivet hole processing of super-thick intermediate core plate, improve the quality and consistency of product.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing, and more specifically, to a method for processing a core-layered printed circuit board. Background Technology

[0002] In the manufacturing process of multilayer core board stacked structures for printed circuit boards, the middle core board and the outer core boards pressed on both sides are usually pre-positioned through rivet holes before being fed into a press for lamination. However, as the number of layers and thickness of the product increase, the overall thickness of the middle core board often exceeds the processing limit of conventional punching equipment, making it impossible to directly punch through holes for riveting and positioning. If conventional through-hole drilling is used, not only is the processing efficiency low, but it is also prone to hole position misalignment and hole wall damage, failing to meet the requirements of high-precision alignment. Furthermore, due to the increased core board thickness, the different material properties, inner layer pattern distribution, and previous process experiences of each core board layer, if simply stacked and pressed, can easily lead to significant interlayer slippage and misalignment during the lamination process, ultimately resulting in poor circuit pattern alignment or even scrapping of the entire board. Summary of the Invention

[0003] The purpose of this invention is to provide a processing method for a core-board stacked printed circuit board, which can meet the requirements for riveting hole processing of ultra-thick intermediate core boards, thereby improving product quality and consistency.

[0004] A method for processing a core-board laminated printed circuit board, the core-board laminated printed circuit board comprising an intermediate core board and a first outer core board and a second outer core board pressed on both sides of the intermediate core board, the processing method comprising the following steps: S1. Provide an intermediate core board, wherein the thickness of the intermediate core board is greater than the limit punching thickness of the drilling equipment; S2. At a predetermined position on the intermediate core board, a controlled-depth drilling hole is made from one surface of the intermediate core board to remove part of the thickness, so that the thickness of the board at that position is reduced to below the limit punching thickness. S3. Use the punching equipment to punch holes in the thinned area to form the first rivet hole; S4. Provide a first outer core board and a second outer core board, and punch corresponding second rivet holes on the first outer core board and the second outer core board respectively; S5. Obtain the expansion and contraction values ​​of the intermediate core board, the first outer core board, and the second outer core board, and select a set of intermediate core boards, the first outer core board, and the second outer core board whose expansion and contraction value differences meet the preset range as a pressing unit; S6. The first outer core board, the middle core board and the second outer core board in the same pressing unit are stacked in sequence and then pressed to form the core board stacked printed circuit board.

[0005] In the above technical solution, when processing the intermediate core board whose thickness exceeds the limit of the punching equipment, the pre-set punching position is first thinned locally by using a controlled depth drilling process, so that the thickness of the board at that position is reduced to within the capacity of the equipment before punching. At the same time, based on the expansion and contraction values ​​of each core board, a set of different values ​​that meet the preset range is selected for matching and pressing. This allows the ultra-thick intermediate core board to successfully complete the rivet hole processing and ensures that the outer core board and the intermediate core board have similar dimensional change trends during the pressing process. This effectively avoids the capacity bottleneck of the punching process and the layer deviation caused by excessive expansion and contraction differences between layers after pressing.

[0006] Furthermore, in step S2, the diameter of the drill bit used for controlled-depth drilling is larger than the diameter of the rivet hole to be formed.

[0007] In the above technical solution, the controlled-depth drilling uses a drill bit larger than the diameter of the rivet hole to locally enlarge and thin the hole. A countersunk hole step with a larger diameter is pre-formed at the position to be punched, which provides a clear drilling guide and a thinner punching allowance for the subsequent punching process. This allows the punch to easily align with the center of the thinned area and punch off the remaining thin layer in one go, ensuring the hole position accuracy and hole wall quality of the rivet hole. It also avoids defects such as punching deviation or hole wall burrs caused by the thinned area being misaligned with the punching position due to the drill bit being too small.

[0008] Furthermore, in step S2, the depth of the controlled-depth borehole is determined as follows: Measure the average thickness of the intermediate core board and set the retained thickness value after thinning, which is less than the limit punching thickness; The depth of the controlled-depth drill hole is equal to the average plate thickness minus the retained thickness value.

[0009] In the above technical solution, the depth of controlled drilling is calculated based on the measured average thickness of the intermediate core board and the preset retention value below the limit thickness of the punching equipment. This allows the controlled drilling to stably control the residual thickness within the range that the punching equipment can process, ensuring that the board surface is not drilled through. This avoids the failure of subsequent punching due to insufficient drilling depth, and also prevents damage to the other side of the board due to excessive drilling depth, thus ensuring process consistency and product yield in mass production.

[0010] Furthermore, in step S2, before performing controlled-depth drilling, the feed face during punching is determined, and the controlled-depth drilling is performed from the side opposite to the feed face.

[0011] In the above technical solution, the punching inlet face is determined before the controlled depth drilling is carried out, and the drilling direction of the controlled depth drilling is set to drill from the back of the inlet face, so that the thin layer to be punched after thinning is located on one side of the punching inlet face. In this way, when the punch enters from this face, it directly faces the already thinned uniform thin layer instead of the complete thick plate, which greatly reduces the punching resistance and makes the punched edge neater and smoother.

[0012] Furthermore, in step S6, before pressing, the core board is positioned by hot melting, and rivets are inserted into the rivet holes for riveting.

[0013] In the above technical solution, before the stacked core boards are fed into the press, they are pre-positioned by hot melting and mechanically riveted and locked with rivets, so that the three core boards form an integral structure before the pressing begins. This effectively resists the lateral shear force generated by resin flow and pressure during the pressing process, prevents the outer thin core board from slipping under high temperature and high pressure conditions, and ensures that the alignment accuracy of the rivet holes and circuit patterns of each layer is within the qualified range after the pressing is completed.

[0014] Furthermore, in step S6, before pressing, a buffer layer is provided between the first outer core plate, the second outer core plate, and the intermediate core plate.

[0015] In the above technical solution, by setting a buffer layer, a heat insulation and buffer barrier is formed between the outer core plate and the hot-pressed steel plate of the press. This avoids the outer core plate from directly contacting the high-temperature steel plate and being subjected to a sudden and severe thermal shock. It slows down the heating rate of the outer core plate in the early stage of pressing and the subsequent rapid thermal contraction. This reduces the real-time expansion and contraction difference between the outer core plate and the middle core plate during the pressing process and reduces the risk of interlayer misalignment caused by the superposition of rate difference and shrinkage difference.

[0016] Furthermore, the buffer layer is made of multiple layers of brand-new kraft paper.

[0017] In the above technical solution, multi-layer new kraft paper is selected as the buffer medium. New kraft paper has good and stable heat insulation performance, compression elasticity and surface flatness. The multi-layer stacking can build a flexible buffer pad with controllable thickness and uniform heat conduction between the steel plate and the outer core board. This not only ensures the stable transfer of heat so that the resin can fully melt and fluidize, but also avoids local overheating and shrinkage caused by concentrated heat conduction. Thus, while ensuring the pressing quality, it effectively suppresses the expansion and contraction fluctuation and slippage tendency of the outer core board.

[0018] Furthermore, the buffer layer is divided into an upper kraft paper group, a middle kraft paper group, and a lower kraft paper group; the upper kraft paper group is laid on the upper surface of the first outer core board, the lower kraft paper group is laid on the lower surface of the second outer core board, and the middle kraft paper group is laid between the middle core board and the first outer core board, and between the middle core board and the second outer core board.

[0019] In the above technical solution, by refining the cushioning kraft paper into an upper layer group covering the upper surface of the first outer core board, a lower layer group covering the lower surface of the second outer core board, and an intermediate layer group laid between the intermediate core board and the first outer core board, and between the intermediate core board and the second outer core board, a heat buffering and sliding barrier system is constructed from the top, bottom and inside. This ensures that not only the outer surface is buffered during hot pressing, but the inner layer interface also receives additional energy dissipation and anti-slip protection. This ensures that each layer is in a relatively stable position during the resin melting and flow process, eliminating abnormal layer deviation and expansion / contraction differences caused by interlayer sliding and uneven internal thermal stress.

[0020] Furthermore, in step S6, the buffer layer is a buffer core board without a circuit pattern; the buffer core board is respectively laid on the upper surface of the first outer core board and the lower surface of the second outer core board.

[0021] In the above technical solution, a buffer core board without circuit patterns is used as a buffer layer and is laid on the upper surface of the first outer core board and the lower surface of the second outer core board. The material of this type of buffer core board is similar to that of the product core board, and the coefficient of thermal expansion and thermal response characteristics are consistent. During pressing, the buffer core board first bears the heat and pressure of the steel plate and undergoes synchronous deformation, transferring the severe thermal shock and lateral friction that originally acted on the outer core board of the product to the sacrificial buffer core board. Thus, while effectively protecting the integrity of the circuit pattern of the outer core board of the product, the synchronous constraint effect of the homogeneous material is used to suppress the slippage and warping of the product core board.

[0022] Furthermore, in step S5, the difference in expansion and contraction values ​​between the intermediate core plate, the first outer core plate, and the second outer core plate of the same pressing unit is ±50μm.

[0023] In the above technical solution, a difference of ±50μm in expansion and contraction is used as the matching grouping of each core plate in the same pressing unit. This ensures that the core plates that are pressed together are highly similar in initial size, controls the maximum size difference between each layer before pressing, and makes each layer exhibit relatively synchronous expansion and contraction behavior due to the consistent starting conditions, even after undergoing a high temperature and high pressure hot pressing process. This significantly reduces the probability of interlayer deviation exceeding the standard and ensures the interlayer alignment yield during the mass production of core-on-core products.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: When processing an intermediate core board whose thickness exceeds the limit of the punching equipment, a controlled-depth drilling process is first used to locally thin the preset punching position, so that the thickness of the board at that position is reduced to within the capacity of the equipment before punching. At the same time, based on the expansion and contraction values ​​of each core board, a set of different values ​​that meet the preset range is selected for matching and pressing. This allows the ultra-thick intermediate core board to successfully complete the rivet hole processing and ensures that the outer core board and the intermediate core board have similar dimensional change trends during the pressing process. This effectively avoids the capacity bottleneck of the punching process and the layer deviation caused by excessive expansion and contraction differences between layers after pressing. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the processing method of a core-board stacked printed circuit board according to an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the intermediate core plate after controlled-depth drilling according to an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the structure of the intermediate core plate after punching according to an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the structure of a core-board stacked printed circuit board according to an embodiment of the present invention.

[0029] Explanation of icon numbers: Intermediate core board 1, depth control hole 11, first rivet hole 12, first outer core board 2, second outer core board 3, second rivet hole 4. Detailed Implementation

[0030] 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.

[0031] 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.

[0032] Please refer to Figures 1 to 4This invention provides a method for processing a core-board laminated printed circuit board, wherein the core-board laminated printed circuit board includes an intermediate core board 1 and a first outer core board 2 and a second outer core board 3 pressed on both sides of the intermediate core board 1. The processing method includes the following steps: S1. Provide an intermediate core board 1, wherein the thickness of the intermediate core board 1 is greater than the limit punching thickness of the drilling equipment; S2. At a predetermined position on the intermediate core board 1, a controlled-depth drilling hole is made from one surface of the intermediate core board 1 to remove part of the thickness, so that the thickness of the board at that position is reduced to below the limit punching thickness. S3. Use the punching equipment to punch holes in the thinned area to form the first rivet hole 12; S4. Provide a first outer core board 2 and a second outer core board 3, and punch corresponding second rivet holes 4 on the first outer core board 2 and the second outer core board 3 respectively. S5. Obtain the expansion and contraction values ​​of the intermediate core plate 1, the first outer core plate 2, and the second outer core plate 3, and select a set of intermediate core plates 1, the first outer core plate 2, and the second outer core plate 3 whose expansion and contraction value differences meet the preset range as a pressing unit. S6. The first outer core board 2, the middle core board 1 and the second outer core board 3 in the same pressing unit are stacked in sequence and then pressed to form the core board stacked printed circuit board.

[0033] For example, the intermediate core board 1 can be a thick core board composed of multiple prepreg sheets and an inner core board, with an overall thickness typically ranging from 2.0 mm to 4.0 mm. The maximum punching thickness of conventional rivet hole punching equipment is usually 2.0 mm. The punching equipment used is, for example, a punching machine. Depth-controlled drilling can be performed using a CNC depth-controlled drilling machine to form depth-controlled holes 11 on the intermediate core board 1. The intermediate core board 1 is made of fiberglass cloth-reinforced epoxy resin copper-clad laminate, while the outer core board is a thin copper-clad laminate.

[0034] As can be seen from the above technical solution, when processing the intermediate core board 1 whose thickness exceeds the limit of the punching equipment, the pre-set punching position is first thinned locally by using a controlled depth drilling process, so that the thickness of the board at that position is reduced to within the capacity of the equipment before punching. At the same time, based on the expansion and contraction values ​​of each core board, a set of different values ​​that meet the preset range is selected for matching and pressing. This allows the ultra-thick intermediate core board 1 to successfully complete the rivet hole processing and ensures that the outer core board and the intermediate core board 1 have similar dimensional change trends during the pressing process. This effectively avoids the capacity bottleneck of the punching process and the layer deviation caused by excessive expansion and contraction differences between layers after pressing.

[0035] In step S2, the diameter of the drill bit used for controlled-depth drilling is larger than the diameter of the rivet hole to be formed.

[0036] For example, when the designed diameter of the rivet hole to be formed is 3.2mm, a 4.0mm diameter drill bit can be used for controlled-depth drilling. A countersunk hole with a diameter of 4.0mm and controlled depth is pre-machined on the surface of the intermediate core plate 1, making the remaining thickness of the plate to be punched at the bottom of the hole extremely thin. During subsequent punching, the punch will precisely complete the cutting within the bottom area of ​​this countersunk hole. If the rivet hole is of other specifications, a drill bit with a diameter 0.5mm to 1.0mm larger than the rivet hole diameter should be selected accordingly.

[0037] Controlled-depth drilling uses a drill bit larger than the diameter of the rivet hole for localized hole enlargement and thinning. A countersunk hole step with a larger diameter is pre-formed at the punching position, providing clear drilling guidance and a thinner punching allowance for subsequent punching processes. This allows the punch to easily align with the center of the thinned area and punch off the remaining thin layer in one go, ensuring the hole position accuracy and hole wall quality of the rivet hole. It also avoids defects such as punching deviation or hole wall burrs caused by misalignment between the thinned area and the punching position due to the drill bit being too small.

[0038] In step S2, the depth of the controlled-depth borehole is determined as follows: Measure the average thickness of the intermediate core board 1, and set the retained thickness value after thinning, which is less than the limit punching thickness; The depth of the controlled-depth drill hole is equal to the average plate thickness minus the retained thickness value.

[0039] For example, after measuring the thickness at multiple locations on the core board 1 using a thickness gauge, the average thickness is calculated to be 3.15 mm. The maximum punching thickness of the punching equipment is 2.0 mm. To ensure reliable punching, a retention thickness of 1.5 mm is set, and the depth of the controlled-depth drilling is set to 1.65 mm. The average thickness of the core board 1 needs to be remeasured and the drilling depth adjusted for each batch to compensate for the thickness fluctuations of the board.

[0040] The depth of controlled drilling is calculated based on the measured average thickness of the intermediate core board 1 and the preset retention value below the limit thickness of the punching equipment. This ensures that the residual thickness of the board is stably controlled within the range that the punching equipment can process, without drilling through the board surface. This avoids subsequent punching failures due to insufficient drilling depth and also prevents damage to the other side of the board due to excessive drilling depth, thus ensuring process consistency and product yield in mass production.

[0041] In step S2, before performing controlled-depth drilling, the feed face during punching is determined, and the controlled-depth drilling is performed from the side opposite to the feed face.

[0042] Before performing controlled-depth drilling, the punching inlet face should be clearly defined, and the drilling direction of the controlled-depth drilling should be set to drill from the back of the inlet face. This ensures that the thin layer to be punched after thinning is located on one side of the punching inlet face. In this way, when the punch enters from this face, it directly faces the already thinned uniform thin layer instead of the complete thick plate, which greatly reduces the punching resistance and makes the punched edge neater and smoother.

[0043] In step S6, before pressing, the core board is positioned by hot melting, and rivets are inserted into the rivet holes for riveting.

[0044] For example, hot-melt positioning can be achieved by heating non-circuit areas at the four corners or edges of the core board using a hot-melt machine to form molten welding points, initially bonding the stacked first outer core board 2, middle core board 1, and second outer core board 3 together. Subsequently, metal rivets are inserted into the pre-formed rivet holes, and the ends of the rivets are flanged and locked using a press riveting or punch riveting tool to complete the mechanical riveting, ensuring that the core board stack has overall rigidity before entering the press.

[0045] Before being fed into the press, the stacked core boards are pre-positioned by hot melting and mechanically riveted and locked with rivets, so that the three core boards form an integral structure before the pressing begins. This effectively resists the lateral shear force generated by resin flow and pressure during the pressing process, prevents the outer thin core board from slipping under high temperature and high pressure conditions, and ensures that the alignment accuracy of the rivet holes and circuit patterns of each layer is within the qualified range after the pressing is completed.

[0046] In step S6, before pressing, buffer layers are respectively set between the first outer core plate 2, the second outer core plate 3, and the intermediate core plate 1. By setting buffer layers, a heat insulation and buffer barrier is formed between the outer core plate and the hot-pressed steel plate of the press, avoiding the outer core plate from directly contacting the high-temperature steel plate and being subjected to a sudden and severe thermal shock. This slows down the heating rate of the outer core plate in the early stage of pressing and the subsequent rapid thermal contraction, thereby reducing the real-time expansion and contraction difference between the outer core plate and the intermediate core plate 1 during the pressing process, and reducing the risk of interlayer misalignment caused by the superposition of rate difference and shrinkage difference.

[0047] In one implementation, the buffer layer is a multi-layer of brand-new kraft paper. Using multi-layer brand-new kraft paper as the buffer medium provides excellent and stable thermal insulation, compressive elasticity, and surface smoothness. The multi-layer stacking creates a flexible buffer layer with controllable thickness and uniform heat conduction between the steel plate and the outer core board. This ensures stable heat transfer for full resin melting and fluidization while avoiding localized overheating and shrinkage caused by concentrated heat conduction. Thus, while ensuring the quality of the pressing process, it effectively suppresses the expansion and contraction fluctuations and slippage tendency of the outer core board.

[0048] The buffer layer is divided into an upper kraft paper group, a middle kraft paper group, and a lower kraft paper group; the upper kraft paper group is laid on the upper surface of the first outer core board 2, the lower kraft paper group is laid on the lower surface of the second outer core board 3, and the middle kraft paper group is laid between the middle core board 1 and the first outer core board 2, and between the middle core board 1 and the second outer core board 3. By refining the cushioning kraft paper into an upper layer group covering the upper surface of the first outer core board 2, a lower layer group covering the lower surface of the second outer core board 3, and an intermediate layer group laid between the intermediate core board 1 and the first outer core board 2, and between the intermediate core board 1 and the second outer core board 3, a heat buffering and sliding barrier system is constructed from the top, bottom, and inside. This ensures that not only the outer surface is buffered during hot pressing, but the inner layer interface also receives additional energy dissipation and anti-slip protection. This ensures that each layer is in a relatively stable position during the resin melting and flow process, eliminating abnormal layer deviation and expansion / contraction differences caused by interlayer sliding and uneven internal thermal stress.

[0049] In another implementation, in step S6, the buffer layer is a buffer core board without a circuit pattern; the buffer core board is laid on the upper surface of the first outer core board 2 and the lower surface of the second outer core board 3.

[0050] In this type of buffer core board without circuit patterns, copper-clad laminate (CCL) of the same or similar material as the outer core board of the product is typically used. During manufacturing, only the copper foil of the entire board is retained without any circuit patterns, or unetched CCL can be used directly. Its thickness can be the same as the outer core board of the product, such as 0.15mm or 0.2mm, and is removed as a process edge after lamination. During stacking, the copper side of the buffer core board faces the outer hot-pressed steel plate to further improve the uniformity of heat conduction.

[0051] A buffer core board without a circuit pattern is used as a buffer layer and is laid on the upper surface of the first outer core board 2 and the lower surface of the second outer core board 3. The material of this type of buffer core board is similar to that of the product core board, and the coefficient of thermal expansion and thermal response characteristics are consistent. During pressing, the buffer core board first bears the heat and pressure of the steel plate and undergoes synchronous deformation. The severe thermal shock and lateral friction that originally acted on the outer core board of the product are transferred to the sacrificial buffer core board. In this way, while effectively protecting the integrity of the circuit pattern of the outer core board of the product, the synchronous constraint effect of the homogeneous material is used to suppress the slippage and warping of the product core board.

[0052] In step S5, the difference in expansion and contraction values ​​between the intermediate core plate 1, the first outer core plate 2, and the second outer core plate 3 in the same pressing unit is ±50μm.

[0053] The expansion and contraction values ​​can be obtained by measuring the target spacing of the intermediate core board 1 and the outer core board using existing measuring instruments. The measured expansion and contraction values ​​in each direction are entered into the matching system, and grouping and pairing are completed according to a preset ±50μm difference threshold. Core boards that exceed this difference range are recombined with corresponding core boards from another batch to ensure that each pressing unit fed into the press has a high degree of matching in its initial state.

[0054] Using a difference of ±50μm in expansion and contraction as the matching grouping of each core plate in the same pressing unit, it is ensured that the core plates of each layer are highly similar in initial size when pressed together. This controls the maximum size difference between each layer before pressing, so that even if they undergo a hot pressing process with high temperature and high pressure, each layer will exhibit relatively synchronous expansion and contraction behavior due to the consistent starting conditions. This significantly reduces the probability of interlayer deviation exceeding the standard and ensures the interlayer alignment yield during the mass production of core-on-core products.

[0055] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0056] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for processing a core-board laminated printed circuit board, characterized in that, The core-board laminated printed circuit board includes an intermediate core board and a first outer core board and a second outer core board laminated on both sides of the intermediate core board. The processing method includes the following steps: S1. Provide an intermediate core board, wherein the thickness of the intermediate core board is greater than the limit punching thickness of the drilling equipment; S2. At a predetermined position on the intermediate core board, a controlled-depth drilling hole is made from one surface of the intermediate core board to remove part of the thickness, so that the thickness of the board at that position is reduced to below the limit punching thickness. S3. Use the punching equipment to punch holes in the thinned area to form the first rivet hole; S4. Provide a first outer core board and a second outer core board, and punch corresponding second rivet holes on the first outer core board and the second outer core board respectively; S5. Obtain the expansion and contraction values ​​of the intermediate core board, the first outer core board, and the second outer core board, and select a set of intermediate core boards, the first outer core board, and the second outer core board whose expansion and contraction value differences meet the preset range as a pressing unit; S6. The first outer core board, the middle core board and the second outer core board in the same pressing unit are stacked in sequence and then pressed to form the core board stacked printed circuit board.

2. The processing method of the core-board laminated printed circuit board according to claim 1, characterized in that, In step S2, the diameter of the drill bit used for controlled-depth drilling is larger than the diameter of the rivet hole to be formed.

3. The processing method of the core-board laminated printed circuit board according to claim 1, characterized in that, In step S2, the depth of the controlled-depth borehole is determined as follows: Measure the average thickness of the intermediate core board and set the retained thickness value after thinning, which is less than the limit punching thickness; The depth of the controlled-depth drill hole is equal to the average plate thickness minus the retained thickness value.

4. The processing method of the core-board laminated printed circuit board according to claim 1, characterized in that, In step S2, before pressing, an electromagnetic fusion machine is used to heat-melt and position the stacked core boards, and rivets are inserted into the rivet holes for riveting.

5. The processing method of the core-board laminated printed circuit board according to claim 1, characterized in that, In step S6, before pressing, the core board is positioned by hot melting, and rivets are inserted into the rivet holes for riveting.

6. The processing method of the core-board laminated printed circuit board according to claim 1, characterized in that, In step S6, before pressing, a buffer layer is provided between the first outer core plate, the second outer core plate, and the intermediate core plate.

7. The processing method of the core-board laminated printed circuit board according to claim 6, characterized in that, The buffer layer is made of multiple layers of brand-new kraft paper.

8. The processing method of the core-board laminated printed circuit board according to claim 7, characterized in that, The buffer layer is divided into an upper kraft paper group, a middle kraft paper group, and a lower kraft paper group; the upper kraft paper group is laid on the upper surface of the first outer core board, the lower kraft paper group is laid on the lower surface of the second outer core board, and the middle kraft paper group is laid between the middle core board and the first outer core board, and between the middle core board and the second outer core board.

9. The processing method of the core-board laminated printed circuit board according to claim 6, characterized in that, In step S6, the buffer layer is a buffer core board without a circuit pattern; the buffer core board is laid on the upper surface of the first outer core board and the lower surface of the second outer core board.

10. The processing method of the core-board laminated printed circuit board according to claim 1, characterized in that, In step S5, the difference in expansion and contraction values ​​between the intermediate core plate, the first outer core plate, and the second outer core plate of the same pressing unit is ±50μm.

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