A method for manufacturing a blind slot board to prevent etching and damage of the solder pad on the back of the blind slot

Abstract

The present invention discloses a method for manufacturing a blind slot board that prevents the back pad of a blind slot from being etched and damaged, comprising the following steps: step S1, preparing a top core board component and a bottom core board component, attaching a film block to the area of ​​the bottom core board component corresponding to the preset position of the blind slot, and pressing the top core board component and the bottom core board component together to form a circuit board; step S2, performing a first controlled depth milling at the preset position of the blind slot on the circuit board to form a blind slot; step S3, picking out part of the film block to expose part of the bottom surface of the top core board component; step S4, drilling the circuit board to form a first through hole in the blind slot; step S5, performing a second controlled depth milling on the circuit board; step S6, picking out the remaining film block. The present invention can prevent the back pad of the blind slot from being etched and damaged, thereby improving the processing efficiency and quality of the circuit board.

Description

Technical Field

[0001] The invention relates to the field of blind slot plate processing technology, and in particular to a method for manufacturing a blind slot plate which can prevent a soldering pad on the back side of the blind slot from being etched and damaged. Background Art

[0002] With the development of electronic product technology, the improvement of assembly density, product performance and the demand for multi-functionality, circuit board blind slot design came into being. Due to the irreplaceable advantages of blind slots, they have been particularly prominent in the RF microwave, wireless communication, power amplifier and other industries in recent years, and the demand has been increasing day by day.

[0003] Among the various existing blind slot boards, one type of blind slot board has non-metallized sidewalls and a plated through-hole at the bottom of the blind slot that is not filled with resin. This plated through-hole serves as a plug-in hole. According to conventional process solutions, the plated through-hole in the blind slot is processed when the inner sub-core board is manufactured, and the circuit at the bottom of the blind slot is also etched when the inner sub-core board is manufactured. During processing, this part of the circuit and the plated through-hole are plated with a layer of resist to protect them, so as to prevent the processed circuit and plated through-hole from being damaged in subsequent processing. However, in this process, the resist on the solder ring where the plated through-hole extends to the back of the blind slot will be damaged due to multiple processes, exposing copper. The exposed copper part will cause a gap in the hole ring during the etching process in the subsequent process, which will in turn cause etching damage to the solder pad on the back of the blind slot. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for manufacturing a blind slot circuit board that prevents etching damage to the solder pads on the back of the blind slot, thereby preventing etching damage to the solder pads on the back of the blind slot and improving the processing efficiency and quality of the circuit board.

[0005] According to an embodiment of the present invention, a method for manufacturing a blind slot board for preventing etching and damage of the back pad of a blind slot includes the following steps: step S1, preparing a top core board component and a bottom core board component, wherein the top core board component and the bottom core board component are both formed by pressing together multiple core boards, and PP material is filled between adjacent core boards, and a blocking film is attached to the area of ​​the bottom core board component corresponding to the preset position of the blind slot, and then PP material is filled between the top core board component and the bottom core board component, and the top core board component and the bottom core board component are pressed together to form a circuit board, and the blocking film is located between the top core board component and the bottom core board component; step S2, performing a first depth control milling at the preset position of the blind slot on the circuit board to form a blind slot, and the depth of the blind slot after the first depth control milling is the same as that of the bottom core board component. The thickness of the components is consistent. When the blind groove is depth-controlled milling, only the film block needs to be exposed to prevent damage to the underlying circuit. The inner diameter of the blind groove after the first depth-controlled milling is smaller than the outer diameter of the film block; step S3, pick out part of the film block to expose part of the bottom surface of the top core board component; step S4, drill the circuit board to form a first through hole in the blind groove, and make a circuit pattern in the blind groove and the first through hole; step S5, perform a second depth-controlled milling on the circuit board, the depth of the blind groove after the second depth-controlled milling is consistent with the depth of the blind groove after the first depth-controlled milling, the inner diameter of the blind groove after the second depth-controlled milling is larger than the inner diameter of the blind groove after the first depth-controlled milling and larger than the outer diameter of the film block. When the blind groove is depth-controlled milling, only the film block needs to be exposed to prevent damage to the underlying circuit; step S6, pick out the remaining film block.

[0006] The present invention has at least the following beneficial effects: During the blind slot board manufacturing process, the first through-hole in the blind slot and the circuit pattern at the bottom of the blind slot are both produced after the circuit board is pressed and assembled, rather than during the core board manufacturing process. Therefore, there is no need to coat the first through-hole and the blind slot with a resist, and thus, etching damage to the pad strip due to damage from the resist is prevented. Therefore, the present invention can prevent etching damage to the pad on the back side of the blind slot, thereby improving the efficiency and quality of circuit board processing.

[0007] According to some embodiments of the present invention, the film blocking sheet is in sheet shape and has an inner ring and an outer ring. The inner ring and the outer ring of the film blocking sheet are adhered to each other in the initial state. In step S3, the inner ring of the film blocking sheet is picked out, and in step S6, the outer ring of the film blocking sheet is picked out.

[0008] According to some embodiments of the present invention, after the inner circle of the film blocking sheet is removed, the single-side spacing between the inner diameter of the outer circle of the film blocking sheet and the inner diameter of the blind groove is 5 mil.

[0009] According to some embodiments of the present invention, the single-side distance between the outer diameter of the outer ring of the film stop and the inner diameter of the blind groove after the second controlled depth milling is 5 mil.

[0010] According to some embodiments of the present invention, the top core board assembly includes a first core board, a second core board and a third core board. The circuit layers on the upper and lower surfaces of the first core board are respectively a CS layer and an L1 layer. The circuit layers on the upper and lower surfaces of the second core board are respectively L2 layers and L3 layers. The circuit layers on the upper and lower surfaces of the third core board are respectively L4 layers and L5 layers. Before making the top core board assembly in step S1, it is necessary to etch out the circuit patterns of the L1 layer, the L2 layer, the L3 layer and the L4 layer. After pressing to form the top core board assembly, it is necessary to etch out the circuit patterns of the L5 layer except for the preset position of the blind groove.

[0011] According to some embodiments of the present invention, the bottom core board assembly includes a fourth core board and a fifth core board, the circuit layers on the upper and lower surfaces of the fourth core board are L6 layer and L7 layer respectively, and the circuit layers on the upper and lower surfaces of the fifth core board are L8 layer and SS layer respectively. Before making the bottom core board assembly in step S1, the circuit patterns of the L7 layer and the L8 layer need to be etched out, and after pressing to form the bottom core board assembly, the circuit pattern of the L6 layer needs to be etched out.

[0012] According to some embodiments of the present invention, the step S4 further includes the following step: drilling the circuit board to form a second through hole outside the blind slot.

[0013] According to some embodiments of the present invention, the circuit pattern of the CS layer and the circuit pattern of the SS layer are etched together when etching the first through hole, the second through hole and the circuit pattern at the bottom of the blind trench.

[0014] According to some embodiments of the present invention, the inner diameter of the blind groove after the second controlled depth milling is spaced 20 mils from the inner diameter of the blind groove after the first controlled depth milling.

[0015] According to some embodiments of the present invention, the formation of the pattern circuit at the bottom of the blind trench is sequentially performed through copper deposition, external light imaging, copper-tin plating, laser patterning and alkaline etching.

[0016] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of a circuit board after completing step S1 according to an embodiment of the present invention;

[0019] Figure 2Schematic diagram of the cross-sectional structure of the circuit board after completing step S2 in an embodiment of the present invention;

[0020] Figure 3 Schematic diagram of the cross-sectional structure of the circuit board after completing step S3 in an embodiment of the present invention;

[0021] Figure 4 Schematic diagram of the cross-sectional structure of the circuit board after completing step S4 in an embodiment of the present invention;

[0022] Figure 5 Schematic diagram of the cross-sectional structure of the circuit board after completing step S5 in an embodiment of the present invention;

[0023] Figure 6 Schematic diagram of the cross-sectional structure of the circuit board after step S6 is completed in an embodiment of the present invention.

[0024] Figure Number:

[0025] Top core plate assembly 100, first core plate 110, second core plate 120, third core plate 130;

[0026] bottom core plate assembly 200, fourth core plate 210, fifth core plate 220;

[0027] Blind slot 300;

[0028] Film block 400, inner ring 410, outer ring 420;

[0029] a first through hole 500;

[0030] The second through hole 600 . DETAILED DESCRIPTION

[0031] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0032] In the description of the present invention, if there is a description of first and second, it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0033] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0034] The present invention discloses a method for manufacturing a blind slot plate to prevent etching damage to the backside pad of the blind slot, comprising the following steps:

[0035] Step S1, prepare a top core panel assembly 100 and a bottom core panel assembly 200, the top core panel assembly 100 and the bottom core panel assembly 200 are both formed by pressing together multiple core panels, PP material is filled between adjacent core panels, and a film block 400 is attached to the area of ​​the bottom core panel assembly 200 corresponding to the preset position of the blind groove, and then the PP material is filled between the top core panel assembly 100 and the bottom core panel assembly 200, and the top core panel assembly 100 and the bottom core panel assembly 200 are pressed together to form a circuit board, and the film block 400 is located between the top core panel assembly 100 and the bottom core panel assembly 200;

[0036] Step S2: Performing a first controlled depth milling operation at a preset blind groove position on the circuit board to form a blind groove 300. The depth of the blind groove 300 after the first controlled depth milling is consistent with the thickness of the underlying core board assembly 200. During the controlled depth milling operation, only the film block 400 needs to be exposed to prevent damage to the underlying circuit. The inner diameter of the blind groove 300 after the first controlled depth milling operation is smaller than the outer diameter of the film block 400.

[0037] Step S3, removing part of the film blocking sheet 400 to expose part of the bottom surface of the top core board assembly 100;

[0038] Step S4, drilling the circuit board to form a first through hole 500 in the blind groove 300, and making a circuit pattern in the blind groove 300 and the first through hole 500;

[0039] Step S5, performing a second controlled depth milling on the circuit board. The depth of the blind groove 300 after the second controlled depth milling is consistent with the depth of the blind groove 300 after the first controlled depth milling. The inner diameter of the blind groove 300 after the second controlled depth milling is larger than the inner diameter of the blind groove 300 after the first controlled depth milling and larger than the outer diameter of the film block 400. When the blind groove is controlled depth milled, only the film block 400 needs to be exposed to prevent damage to the underlying circuit.

[0040] Step S6: picking out the remaining film blocking sheets 400 .

[0041] It is understood that during the blind slot board manufacturing process of the present invention, the first through hole 500 in the blind slot 300 and the circuit pattern at the bottom of the blind slot 300 are both produced after the circuit board is pressed and combined, rather than during the core board manufacturing process. Therefore, there is no need to coat the first through hole 500 and the blind slot 300 with a resist, and thus, the etching damage of the pad strip due to damage from the resist will not occur. Therefore, the present invention can prevent etching damage to the pad on the back side of the blind slot, thereby improving the efficiency and quality of circuit board processing.

[0042] Furthermore, in order to better perform depth-controlled blind groove milling on the laminated circuit board, the present invention further affixes a film block 400 to the bottom core plate assembly 200. The area where the film block 400 is located will not be filled with PP material during the subsequent lamination process, and thus, during the subsequent depth-controlled milling process, the tool will not touch the PP layer between the bottom core plate assembly 200 and the top core plate assembly 100 (i.e., Figure 1 If the adhesive sheet 400 structure is not provided, the adhesive on the adhesive sheet will melt during the high temperature pressing of the PP3 layer, and the melted adhesive will flow to the bottom surface of the top core plate assembly 100 (i.e. Figure 1 The L5 layer circuit layer in the circuit is above the L5 layer, thereby affecting the subsequent production of the L5 layer circuit.

[0043] In addition, the first through hole 500 and the bottom circuit pattern of the blind groove 300 in the present invention are both produced after the circuit board is pressed together to form an integral body. Therefore, there will be no problem of misalignment caused by inconsistent expansion and contraction of the circuit board in various processes, thereby improving the quality of the circuit board.

[0044] It should be noted that the blind groove board referred to in the present invention is a circuit board with a blind groove 300. In addition, the up and down directions involved in the embodiment of the present invention are only directions set for the convenience of expression. This scheme is not limited to the placement orientation in the embodiment of the present invention. In practice, it can be rotated accordingly according to the placement direction of different circuit boards.

[0045] like Figures 1 to 6 As shown, the film block 400 is in sheet shape and has an inner ring 410 and an outer ring 420. The inner ring 410 and the outer ring 420 of the film block 400 are separated from each other in the initial state (i.e., the state in step S1) (the distance between the inner ring 410 and the outer ring 420 of the film block 400 is equal to the diameter of the light spot), the inner ring 410 and the outer ring 420 are in the same horizontal plane and have the same thickness. In step S3, the inner ring 410 of the film block 400 is picked out, and in step S6, the outer ring 420 of the film block 400 is picked out. The film barrier 400 is laser cut into an inner ring 410 and an outer ring 420 to facilitate subsequent separation. The film barrier 400 is processed by attaching the entire film barrier to the L5 circuit layer, then laser-cutting the inner and outer rings 410, 420 of the film barrier 400. Finally, the unnecessary tape is removed, leaving only the film barrier 400. It should be noted that the film barrier 400 can be a sheet made of polyimide, and the surfaces of the film barrier 400 that contact the L6 and L5 circuit layers can have a certain degree of adhesion.

[0046] Reference Figure 3 In step S3, after the inner ring 410 of the film blocking sheet 400 is removed, the single-side spacing between the inner diameter of the outer ring 420 of the film blocking sheet 400 and the inner diameter of the blind groove 300 can be set to 5 mil.

[0047] Reference Figure 5 In step S5, after the second controlled depth milling, the outer diameter of the outer ring 420 of the film stop 400 and the inner diameter of the blind groove 300 after the second controlled depth milling are 5 mils on one side, so as to completely expose the outer ring 420 of the blind groove 300, making it easier to pick out the outer ring 420 of the blind groove 300 later.

[0048] The top core board assembly 100 in the embodiment of the present invention includes a first core board 110, a second core board 120 and a third core board 130. The circuit layers on the upper and lower surfaces of the first core board 110 are respectively the CS layer and the L1 layer, the circuit layers on the upper and lower surfaces of the second core board 120 are respectively the L2 layer and the L3 layer, and the circuit layers on the upper and lower surfaces of the third core board 130 are respectively the L4 layer and the L5 layer. Before making the top core board assembly 100 in step S1, it is necessary to etch out the circuit patterns of the L1 layer, L2 layer, L3 layer and L4 layer. After pressing to form the top core board assembly 100, it is necessary to etch out the circuit patterns of the L5 layer except for the preset position of the blind groove to avoid damage to the outer layer circuit during the pressing process.

[0049] The bottom core board assembly 200 in the embodiment of the present invention includes a fourth core board 210 and a fifth core board 220. The circuit layers on the upper and lower surfaces of the fourth core board 210 are L6 layer and L7 layer respectively, and the circuit layers on the upper and lower surfaces of the fifth core board 220 are L8 layer and SS layer respectively. Before making the bottom core board assembly 200 in step S1, the circuit patterns of the L7 layer and L8 layer need to be etched out. After pressing to form the bottom core board assembly 200, the circuit pattern of the L6 layer needs to be etched out to avoid damage to the outer layer circuit during the pressing process.

[0050] In step S4 of the embodiment of the present invention, the following step may be further included: drilling the circuit board to form a second through hole 600 outside the blind slot 300 to meet the situation where a through hole is also provided outside the blind slot 300 .

[0051] It should be noted that the circuit pattern of the CS layer and the circuit pattern of the SS layer can be etched together when etching the first through hole 500 , the second through hole 600 and the circuit pattern at the bottom of the blind trench 300 .

[0052] Reference Figure 5 The inner diameter of the blind groove 300 after the second controlled depth milling is 20 mils apart from the inner diameter of the blind groove 300 after the first controlled depth milling. The second controlled depth milling can remove the metallized inner wall of the blind groove 300 to achieve non-metallization of the blind groove 300.

[0053] It is understandable that the circuit pattern at the bottom of the blind groove 300 can be formed by sequentially performing copper deposition, external light imaging, copper-tin plating, laser patterning and alkaline etching.

[0054] A method for manufacturing a blind slot board to prevent etching and damage of the backside pad of the blind slot in the present invention specifically comprises the following steps:

[0055] Step S1.1, prepare the top core plate assembly 100 and the bottom core plate assembly 200, the top core plate assembly 100 and the bottom core plate assembly 200 are both formed by pressing together multiple core plates, and PP material is filled between adjacent core plates. The top core plate assembly 100 includes a first core plate 110, a second core plate 120 and a third core plate 130. The circuit layers on the upper and lower surfaces of the first core plate 110 are respectively CS layer and L1 layer, the circuit layers on the upper and lower surfaces of the second core plate 120 are respectively L2 layer and L3 layer, and the circuit layers on the upper and lower surfaces of the third core plate 130 are respectively L4 layer and L5 layer. Before making the top core plate assembly 100, it is necessary to etch out The circuit patterns of the L1 layer, L2 layer, L3 layer and L4 layer need to be etched out after the top core board component 100 is pressed together to form the circuit pattern of the L5 layer except the preset position of the blind groove. The bottom core board component 200 includes a fourth core board 210 and a fifth core board 220. The circuit layers on the upper and lower surfaces of the fourth core board 210 are L6 layer and L7 layer respectively, and the circuit layers on the upper and lower surfaces of the fifth core board 220 are L8 layer and SS layer respectively. Before making the bottom core board component 200, the circuit patterns of the L7 layer and L8 layer need to be etched out. After pressing together to form the bottom core board component 200, the circuit pattern of the L6 layer needs to be etched out.

[0056] Step S1.2, attaching a film block 400 to the area of ​​the L6 layer of the bottom core panel assembly 200 corresponding to the preset position of the blind groove, the film block 400 is in a sheet shape and has an inner ring 410 and an outer ring 420, the inner ring 410 and the outer ring 420 of the film block 400 are adhered to each other in the initial state, filling PP material between the top core panel assembly 100 and the bottom core panel assembly 200, pressing the top core panel assembly 100 and the bottom core panel assembly 200 to form a circuit board, and the film block 400 is located between the L5 layer of the top core panel assembly 100 and the L6 layer of the bottom core panel assembly 200;

[0057] Step S2, performing a first controlled depth milling at a preset position of the blind groove on the circuit board to form a blind groove 300, wherein the depth of the blind groove 300 after the first controlled depth milling is consistent with the thickness of the underlying core board assembly 200, and the inner diameter of the blind groove 300 after the first controlled depth milling is smaller than the outer diameter of the film block 400;

[0058] Step S3, picking off the inner circle 410 of the film block 400 to expose a portion of the L5 layer of the top core board assembly 100;

[0059] Step S4: drilling the circuit board to form a first through hole 500 in the blind slot 300 and a second through hole 600 outside the blind slot 300, and forming circuit patterns in the blind slot 300 and in the first through hole 500 and the second through hole 600, i.e., metallizing the first through hole 500 and the second through hole 600;

[0060] Step S5, performing a second controlled depth milling on the circuit board, wherein the depth of the blind groove 300 after the second controlled depth milling is consistent with the depth of the blind groove 300 after the first controlled depth milling, and the inner diameter of the blind groove 300 after the second controlled depth milling is larger than the inner diameter of the blind groove 300 after the first controlled depth milling and larger than the outer diameter of the outer ring 420 of the film block 400;

[0061] Step S6: picking off the outer ring 420 of the film blocking sheet 400.

[0062] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] Of course, the present invention is not limited to the above-mentioned embodiments. Those skilled in the art may make equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for manufacturing a blind slot board to prevent etching damage to the back pad of the blind slot, characterized in that: The following steps are involved: Step S1, preparing a top core board component and a bottom core board component, wherein the top core board component and the bottom core board component are both formed by pressing a plurality of core boards together, PP material is filled between adjacent core boards, a blocking film is affixed to an area of ​​the bottom core board component corresponding to a preset position of a blind groove, and then the PP material is filled between the top core board component and the bottom core board component, and the top core board component and the bottom core board component are pressed together to form a circuit board, and the blocking film is located between the top core board component and the bottom core board component; Step S2, performing a first controlled depth milling at a preset position of the blind groove on the circuit board to form a blind groove, wherein the depth of the blind groove after the first controlled depth milling is consistent with the thickness of the underlying core board component, and only the plastic blocking sheet needs to be exposed during the controlled depth milling of the blind groove to prevent damage to the underlying circuit, and the inner diameter of the blind groove after the first controlled depth milling is smaller than the outer diameter of the plastic blocking sheet; Step S3, removing a portion of the film blocking sheet to expose a portion of the bottom surface of the top core board assembly; Step S4, drilling the circuit board to form a first through hole in the blind groove, and making a circuit pattern in the blind groove and the first through hole; Step S5, performing a second controlled depth milling on the circuit board, wherein the depth of the blind groove after the second controlled depth milling is consistent with the depth of the blind groove after the first controlled depth milling, and the inner diameter of the blind groove after the second controlled depth milling is larger than the inner diameter of the blind groove after the first controlled depth milling and larger than the outer diameter of the film block. When the blind groove is controlled depth milled, only the film block needs to be exposed to prevent damage to the underlying circuit; Step S6: picking out the remaining film blocking sheets.

2. A method for manufacturing a blind slot board to prevent etching damage to the back pad of the blind slot according to claim 1, characterized in that: The film blocking sheet is in sheet form and has an inner ring and an outer ring. The inner ring and the outer ring of the film blocking sheet are initially adhered to each other. In step S3, the inner ring of the film blocking sheet is picked out, and in step S6, the outer ring of the film blocking sheet is picked out.

3. A method for manufacturing a blind slot board to prevent etching damage to the back pad of the blind slot according to claim 2, characterized in that: After the inner circle of the film blocking sheet is removed, the single-side spacing between the inner diameter of the outer circle of the film blocking sheet and the inner diameter of the blind groove is 5 mil.

4. The method for manufacturing a blind slot board to prevent etching damage to the backside pad of the blind slot according to claim 2, characterized in that: The single-side distance between the outer diameter of the outer ring of the film barrier and the inner diameter of the blind groove after the second depth control milling is 5 mil.

5. The method for manufacturing a blind slot board to prevent etching damage to the backside pad of the blind slot according to claim 1, characterized in that: The top core board assembly includes a first core board, a second core board and a third core board. The circuit layers on the upper and lower surfaces of the first core board are respectively the CS layer and the L1 layer, the circuit layers on the upper and lower surfaces of the second core board are respectively the L2 layer and the L3 layer, and the circuit layers on the upper and lower surfaces of the third core board are respectively the L4 layer and the L5 layer. Before making the top core board assembly in step S1, it is necessary to etch out the circuit patterns of the L1 layer, the L2 layer, the L3 layer and the L4 layer. After pressing to form the top core board assembly, it is necessary to etch out the circuit patterns of the L5 layer except for the preset position of the blind groove.

6. A method for manufacturing a blind slot board to prevent etching damage to the backside pad of the blind slot according to claim 5, characterized in that: The bottom core board assembly includes a fourth core board and a fifth core board. The circuit layers on the upper and lower surfaces of the fourth core board are L6 layer and L7 layer respectively, and the circuit layers on the upper and lower surfaces of the fifth core board are L8 layer and SS layer respectively. Before making the bottom core board assembly in step S1, the circuit patterns of the L7 layer and the L8 layer need to be etched out. After pressing to form the bottom core board assembly, the circuit pattern of the L6 layer needs to be etched out.

7. A method for manufacturing a blind slot board to prevent etching damage to the backside pad of the blind slot according to claim 6, characterized in that: In the step S4, the method further includes the following steps: drilling the circuit board to form a second through hole outside the blind slot.

8. A method for manufacturing a blind slot board to prevent etching damage to the backside pad of a blind slot according to claim 7, characterized in that: The circuit pattern of the CS layer and the circuit pattern of the SS layer are etched together when etching the first through hole, the second through hole and the circuit pattern at the bottom of the blind trench.

9. The method for manufacturing a blind slot board to prevent etching damage to the backside pad of the blind slot according to claim 1, characterized in that: The inner diameter of the blind groove after the second controlled depth milling is spaced 20 mils from the inner diameter of the blind groove after the first controlled depth milling.

10. The method for manufacturing a blind slot board to prevent etching damage to the backside pad of the blind slot according to claim 1, characterized in that: The formation of the pattern circuit at the bottom of the blind groove is sequentially carried out through copper deposition, external light imaging, copper tin plating, laser burning pattern and alkaline etching.

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