PCB and processing method thereof

Abstract

The application relates to the technical field of PCBs, and discloses a PCB and a processing method thereof. The method comprises the following steps: providing a substrate to be processed; performing pretreatment on the substrate to be processed, wherein the pretreatment comprises the following steps: removing the copper foil of a pretreatment area of a first surface of the substrate to be processed and part of the substrate under the copper foil, so as to form a stepped groove; the pretreatment area covers a preset drilling area of a target processing hole and is larger than the preset drilling area by a preset size on one side; drilling the preset drilling area to obtain the target processing hole; performing copper electroplating on the substrate to be processed; and performing resin plug processing on the target processing hole. According to the pretreatment, the stepped groove is formed, the hole opening is naturally thickened during electroplating, the selective thickening and accurate regulation and control of the copper coating can be realized, the copper is filled in the stepped groove during electroplating to form an embedded anchoring structure, the embedded anchoring structure is physically interlocked with the substrate, and the bonding force and reliability are significantly improved.

Description

Technical Field

[0001] This application relates to the field of PCB technology, and more particularly to a PCB and its processing method. Background Technology

[0002] In recent years, low-Earth orbit (LEO) satellite technology has been developing rapidly, gradually becoming a strategic focus in the global aerospace and communications fields. In PCB products, which form the basis of the physical and electrical interconnections of satellite electronic systems, the copper overlay (i.e., the annular thickened copper layer covering the orifice to connect the hole wall plating to the surface traces) is a key structure ensuring the reliability of interlayer electrical interconnections. Its thickness and uniformity directly affect signal quality and product lifespan.

[0003] However, with the increasing integration of satellite functions, PCB structure design is becoming increasingly complex, often involving multiple lamination processes, posing a severe challenge to the ability to control copper thickness during manufacturing. Especially in the copper-clad areas, thin copper is prone to occur, and this defect directly affects the electrical interconnect reliability, signal transmission quality, and long-term service life of the PCB under harsh environments such as mechanical vibration, extreme temperature cycling, and vacuum radiation.

[0004] Therefore, existing technologies need to be improved to enhance the ability to control the copper thickness of PCB copper cladding under complex structural designs.

[0005] The above information is provided as background information only to aid in understanding this application and does not constitute an assertion or admission that any of the above content can be used as prior art relative to this application. Summary of the Invention

[0006] This application provides a PCB and its processing method to solve the problem in the prior art that the copper thickness of the copper-clad area cannot be effectively controlled.

[0007] To achieve the above objectives, this application provides the following technical solution:

[0008] In a first aspect, embodiments of this application provide a PCB manufacturing method, including:

[0009] A substrate to be processed is provided, the substrate having a first surface and a second surface disposed opposite to each other;

[0010] The substrate to be processed is pre-treated, the pre-treatment including: removing the bottom copper of the pre-treatment area of ​​the first surface of the substrate to be processed and a portion of the substrate thickness below the bottom copper to form a stepped groove; the pre-treatment area covers the preset drilling area of ​​the target processing hole and is larger than the preset drilling area by a preset dimension on one side.

[0011] Drill holes in the preset drilling area of ​​the substrate to be processed to obtain the target processing hole;

[0012] After completing the pretreatment and drilling, the substrate to be processed is electroplated with copper to form a cladding copper layer in the stepped groove area around the target processed hole, a hole copper layer electrically connected to the cladding copper layer is formed on the hole wall of the target processed hole, and surface copper is formed in other areas of the first surface except for the stepped groove area.

[0013] After copper plating, the target machined holes are filled with resin.

[0014] Optionally, the preprocessing further includes: machining and shaping the groove opening of the stepped groove so that the inner sidewall of the stepped groove is formed as an inclined surface, and the angle between the inclined surface and the bottom wall of the stepped groove is an obtuse angle.

[0015] Optionally, the method for machining and shaping the groove opening of the stepped groove includes:

[0016] The bottom copper on the outer periphery of the stepped groove is cut and leveled using a milling cutter. The tool path is from the outside to the inside, and the milling depth gradually increases from the outside to the inside.

[0017] Optionally, the milling depth of the milling cutter is equal to the thickness of the bottom copper.

[0018] Optionally, the PCB processing method further includes: after the copper plating and before the resin plugging, first covering the surface area of ​​the first surface corresponding to the stepped groove with an anti-etching protective layer, then reducing the surface copper of the first surface to a preset target thickness by chemical etching, and then removing the anti-etching protective layer.

[0019] Optionally, the PCB processing method further includes: after removing the etch-resistant protective layer, leveling the first surface of the substrate to be processed.

[0020] Optionally, the pre-processed area is 2-4 mil larger on one side than the preset drilling area.

[0021] Optionally, in the pretreatment step, the thickness of the substrate removed is 5-10 μm.

[0022] Secondly, embodiments of this application provide a PCB, which is manufactured according to any of the PCB processing methods described above.

[0023] Compared with the prior art, this application has the following beneficial effects:

[0024] On the one hand, the embodiments of this application pre-form a stepped groove around the orifice through pretreatment. The stepped groove structure allows the orifice area to naturally obtain a thicker copper layer deposition during the subsequent electroplating process, thereby enabling the copper coating layer to achieve local selective thickening without adding additional processes. At the same time, by controlling the preset size of the pretreatment area and the substrate reduction thickness, the structural size of the stepped groove can be precisely designed and implemented, thereby achieving precise control of the copper coating layer thickness.

[0025] On the other hand, since the copper cladding layer in this embodiment is formed by electroplated copper filling the stepped groove, an embedded anchoring structure is formed inside the substrate, which makes the copper cladding layer and the substrate form a reliable physical interlock, improving the bonding force between the two and thus ensuring the reliability of the copper cladding layer.

[0026] This application has other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of this application. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of a PCB manufacturing method provided in an embodiment of this application;

[0029] Figure 2 This is a schematic diagram showing the effect of the PCB after preprocessing according to the embodiments of this application;

[0030] Figure 3 This is a schematic diagram of the plating recess effect of the PCB provided in the embodiments of this application;

[0031] Figure 4 This is a schematic diagram of the tool path direction in the orifice shaping process provided in the embodiments of this application;

[0032] Figure 5 This is a schematic diagram illustrating the effect of PCB reshaping after orifice shaping according to an embodiment of this application;

[0033] Figure 6 This is a schematic diagram showing the effect of drilling on a PCB provided in an embodiment of this application;

[0034] Figure 7This is a schematic diagram illustrating the effect of copper plating on a PCB provided in this application embodiment;

[0035] Figure 8 This is a schematic diagram showing the effect of resin plugging on the PCB provided in the embodiments of this application;

[0036] Figure 9 This is a schematic diagram of the copper reduction process provided in the embodiments of this application;

[0037] Figure 10 This is a schematic diagram illustrating the effect of copper reduction on a PCB provided in this application embodiment;

[0038] Figure 11 This is an operational schematic diagram of the copper leveling process provided in the embodiments of this application;

[0039] Figure 12 This is a schematic diagram showing the effect of the PCB after copper leveling according to the embodiments of this application.

[0040] Figure label:

[0041] 1. Substrate to be processed; 2. Base copper; 3. Substrate; 4. Step groove; 5. Target processing hole; 6. Copper coating layer; 7. Surface copper; 8. Hole copper layer; 9. Resin; 10. Anti-etching protective layer. Detailed Implementation

[0042] 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. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] To effectively control the copper coating thickness, please refer to... Figure 1 This application provides a PCB manufacturing method, including:

[0044] S11. Provide a substrate 1 to be processed, the substrate 1 having a first surface and a second surface disposed opposite to each other.

[0045] In this step, the substrate 1 to be processed is obtained by pressing a multilayer core board under high temperature and high pressure. The outer surfaces of the outer core boards on the upper and lower sides are respectively formed as the first surface and the second surface of the substrate 1 to be processed.

[0046] S12. Pre-processing is performed on the substrate 1 to be processed. The pre-processing includes removing the bottom copper 2 of the first surface pre-processing area of ​​the substrate 1 to be processed and the substrate 3 of a certain thickness located below the bottom copper 2 to form a stepped groove 4. The pre-processing area covers the preset drilling area of ​​the target processing hole 5 and is larger than the preset drilling area by a preset size on one side.

[0047] S13. Drill holes in the preset drilling area of ​​the substrate 1 to be processed to obtain the target processing hole 5.

[0048] S14. After completing the pretreatment and drilling, copper plating is performed on the substrate 1 to be processed, so as to form a cladding copper layer 6 in the step groove 4 area around the target processing hole 5, a hole copper layer 8 electrically connected to the cladding copper layer 6 is formed on the hole wall of the target processing hole 5, and a surface copper 7 is formed in the other areas of the first surface except for the step groove 4 area.

[0049] S15. After copper plating, the target machined hole 5 is plugged with resin 9.

[0050] In general, on the one hand, the embodiments of this application pre-form a stepped groove 4 around the orifice through pre-treatment. This stepped groove 4 structure allows for a thicker copper layer deposition in the orifice area during subsequent electroplating, thereby enabling selective thickening of the copper coating layer 6 locally without the need for additional processes. Simultaneously, by controlling the preset dimensions of the pre-treatment area and the thickness reduction of the substrate 3, the structural dimensions of the stepped groove 4 can be precisely designed and implemented, thus achieving precise control over the thickness of the copper coating layer 6. On the other hand, since the copper coating layer 6 in the embodiments of this application is formed by electroplated copper filling the stepped groove 4, an embedded anchoring structure is formed inside the substrate 3, resulting in a reliable physical interlock between the copper coating layer 6 and the substrate 3, enhancing their bonding strength and ensuring the reliability of the copper coating layer 6.

[0051] When the stepped groove 4 initially formed in step S2 is a right-angled or acute-angled structure, the corner area of ​​the stepped groove 4 at the groove opening is a typical concave corner structure during the electroplating process. Copper ions in this area are consumed at a high speed during electroplating, and the replenishment rate of copper ions in the electroplating solution is difficult to match the consumption rate due to the limited diffusion path. This results in insufficient local ion concentration at the groove opening corner, and consequently, after the copper plating process, a plating depression is easily formed at the corner of the stepped groove 4 (e.g., ...). Figure 3 (As shown). This depression will cause the copper cladding layer 6 to become thinner and less dense at the corner of the slot, becoming a weak area and severely weakening the mechanical strength and long-term reliability of the copper cladding layer 6.

[0052] Therefore, in an optional embodiment, the preprocessing further includes: machining and shaping the groove opening of the stepped groove 4 so that the inner sidewall of the stepped groove 4 is formed as an inclined surface, and the angle between the inclined surface and the bottom wall of the stepped groove 4 is an obtuse angle.

[0053] The core function of this sloping design is to optimize the ion diffusion path and current density distribution during electroplating by changing the geometric contour of the stepped groove 4, while eliminating stress concentration points caused by structural abrupt changes. This synergistically reduces the degree of plating depression from two dimensions: electroplating uniformity and structural mechanics. Specifically, when the inner wall of the stepped groove 4 is shaped into a sloping surface, and the angle between the sloping surface and the bottom wall is obtuse, the groove opening corner of the stepped groove 4 changes from a "sharp right angle / acute angle" to a "gentle obtuse angle transition." On the one hand, the gentle sloping surface structure increases the ion diffusion channel in the corner area, allowing copper ions in the electroplating solution to be replenished to the groove opening area more smoothly. This eliminates the local ion concentration deficiency caused by limited diffusion, enabling the electroplated copper layer to be uniformly deposited in the groove opening transition area, effectively suppressing the formation of depressions. On the other hand, the smooth transition structure of the obtuse angled sloping surface eliminates stress concentration points at sharp corners, allowing the coated copper layer 6 to transmit and release stress more evenly under thermal loads, further improving the structural integrity and crack resistance of the coated copper layer 6.

[0054] For example, the method for machining and shaping the groove opening of the stepped groove 4 includes:

[0055] The bottom copper 2 on the outer periphery of the groove opening of the stepped groove 4 is cut and leveled using a milling cutter. The tool feed direction is from the outside to the inside, and the milling depth gradually increases from the outside to the inside. The milling depth of the milling cutter is equal to the thickness of the bottom copper 2.

[0056] In this embodiment, the milling cutter moves from the outside in and the milling depth gradually increases from the outside in, precisely controlling the milling depth to be equal to the thickness of the bottom copper 2. This allows the edge of the stepped groove 4 to be cut into a gentle slope transition structure, effectively removing the edge of the bottom copper 2 without damaging the substrate 3 at the bottom of the groove. This slope structure increases the ion diffusion channels in the corner area of ​​the groove opening during subsequent electroplating, effectively suppressing plating depressions and ensuring that the copper layer 6 has a uniform thickness and dense structure. At the same time, the outward-to-inward cutting direction also prevents the copper layer from flipping up or peeling off, improving reliability.

[0057] Please see Figures 2 to 12 Below is an application example, and the specific processing method includes:

[0058] S21. Pre-treatment of target holes.

[0059] like Figure 2 As shown, the target processing hole 5 that needs to be controlled for copper plating is pre-treated. The size of the pre-treatment area is 2-4 mil larger than the single side of the hole. The bottom copper 2 in the area is removed through pre-treatment to form a substrate ring. At the same time, the substrate 3 below with a thickness of 5-10 μm is reduced (to increase roughness and improve the copper plating adhesion).

[0060] S22, Orifice shaping.

[0061] To alleviate such Figure 3 The following describes the depressions in the plating layer after electroplating, such as... Figure 4 As shown, a large-angle milling cutter is used to cut and flatten the bottom copper 2 of the substrate ring opening. The tool path is from the outside to the inside. The effect after shaping is as follows. Figure 5 As shown.

[0062] S23. Make a through hole.

[0063] Using a CCD drilling machine (ensuring precise alignment), holes requiring copper coating are drilled. The post-drilling effect is as follows: Figure 6 As shown.

[0064] S24, Electroplating.

[0065] The PCB is electroplated as a whole (electroplating parameters are designed to plate 8 through holes in one pass), and the effect after electroplating is as follows. Figure 7 As shown.

[0066] S25, resin 9, hole plugging process.

[0067] The PCB undergoes resin 9-hole plugging, and the effect after resin 9-hole plugging is as follows. Figure 8 As shown.

[0068] S26, copper reduction processing on the surface.

[0069] like Figure 9 As shown, an anti-etching protective layer 10 is used to cover the corresponding area of ​​the stepped groove on the first surface, followed by a copper reduction operation. The effect after copper reduction is as follows. Figure 10 As shown.

[0070] S27, surface copper 7 leveling process.

[0071] like Figure 11 As shown, the entire PCB board is leveled to remove surface resin residue, copper pillars, etc. The effect after leveling is as follows. Figure 12 As shown.

[0072] Secondly, embodiments of this application provide a PCB, which is manufactured according to the PCB processing method described in any of the above embodiments.

[0073] The PCB described above can perform the methods provided in any embodiment of this application and has the corresponding beneficial effects of performing the methods, which will not be elaborated here.

[0074] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A PCB manufacturing method, characterized in that, include: A substrate (1) to be processed is provided, the substrate (1) having a first surface and a second surface disposed opposite to each other; The substrate to be processed (1) is pre-processed, the pre-processing includes: removing the bottom copper (2) of the pre-processed area of ​​the first surface of the substrate to be processed (1) and a portion of the thickness of the substrate (3) below the bottom copper (2) to form a stepped groove (4); the pre-processed area covers the preset drilling area of ​​the target processing hole (5) and is larger than the preset drilling area by a preset size on one side. Drill holes in the preset drilling area of ​​the substrate to be processed (1) to obtain the target processing hole (5); After completing the pretreatment and drilling, the substrate (1) to be processed is electroplated with copper to form a cladding copper layer (6) in the stepped groove (4) area around the target processing hole (5), a hole copper layer (8) electrically connected to the cladding copper layer (6) is formed on the hole wall of the target processing hole (5), and surface copper (7) is formed in other areas of the first surface except for the stepped groove (4) area. After copper plating, the target machined hole (5) is plugged with resin (9).

2. The PCB processing method according to claim 1, characterized in that, The preprocessing further includes: processing and shaping the groove opening of the stepped groove (4) so ​​that the inner sidewall of the stepped groove (4) is formed as an inclined surface, and the angle between the inclined surface and the bottom wall of the stepped groove (4) is an obtuse angle.

3. The PCB processing method according to claim 2, characterized in that, The method for machining and shaping the groove opening of the stepped groove (4) includes: The bottom copper (2) on the outer periphery of the groove opening of the stepped groove (4) is cut and leveled using a milling cutter. The cutting direction is from the outside to the inside, and the milling depth gradually increases from the outside to the inside.

4. The PCB processing method according to claim 3, characterized in that, The milling depth of the milling cutter is equal to the thickness of the bottom copper (2).

5. The PCB processing method according to claim 1, characterized in that, The PCB processing method further includes: after the copper plating and before the resin (9) plugs the holes, first covering the surface area of ​​the first surface corresponding to the stepped groove (4) with an anti-etching protective layer (10), then reducing the surface copper (7) of the first surface to a preset target thickness by chemical etching, and then removing the anti-etching protective layer (10).

6. The PCB processing method according to claim 5, characterized in that, The PCB processing method further includes: after removing the anti-etching protective layer (10), leveling the first surface of the substrate to be processed (1).

7. The PCB processing method according to claim 1, characterized in that, The pre-processed area is 2-4 mil larger on each side than the preset drilling area.

8. The PCB processing method according to claim 1, characterized in that, In the pretreatment step, the thickness of the substrate (3) is removed by 5-10 μm.

9. A PCB, characterized in that, The PCB is manufactured according to the PCB processing method according to any one of claims 1 to 8.

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