High-density multi-layer interconnection circuit board structure with optimized surface flatness

Abstract

A high-density multilayer interconnection circuit board structure with optimized surface flatness comprises a first circuit board, a second circuit board, a third circuit board, a first copper foil, a second copper foil and a plurality of prepregs, and the first circuit board, the first copper foil, the second circuit board, the second copper foil and the third circuit board are sequentially stacked from top to bottom. The copper foil is arranged on the second circuit board, the prepreg is arranged between the two adjacent circuit boards and the copper foil, an electroplating hole is formed in the surface, in contact with the prepreg, of the second circuit board, a groove is formed in the top surface of the electroplating hole, and a bulge is arranged at the corresponding position of the prepreg; the circuit board is also provided with a pre-hollow area, and the outer side of the pre-hollow area is provided with a copper ring. According to the utility model, the problem that the copper foil warping plate is not flat when the multi-layer plate is laminated for multiple times can be solved. And the problem of unevenness caused by hole sinking can be reduced, the practicability is high, and high popularization significance is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to circuit board technical field especially relates to a high density multilayer interconnection circuit board structure of optimization surface flatness. BACKGROUND

[0002] In recent years, with the high speed development of line manufacturing technology, high density interconnection circuit board is more and more high in multifunctional integration, thin type, light and handy, manufacturing precision etc. With the increasing line density and the diversification of interlayer structure of high density interconnection circuit board, more and more copper plated blind holes are on the circuit board. In actual production, the thickness aperture of hole filling electroplating board is usually 0.8:1, due to the reasons of blind hole aperture or through hole thickness ratio electroplating hole filling (hole structure) and the basic principle limitation of electroplating additive, the inner recess structure will inevitably appear on the top surface of blind hole filling. When making multilayer board pressing, PP semi-solidified is arranged between adjacent boards, and the softened PP material will flow into the copper plated recess, and after solidification, the recess part is formed on the upper end of the upper layer board and the lower end of the lower layer board, which affects the surface flatness of the circuit board. SUMMARY

[0003] Therefore, it is necessary to provide a high density multilayer interconnection circuit board structure for optimizing surface flatness in view of the deficiencies in the prior art.

[0004] A high density multilayer interconnection circuit board structure for optimizing surface flatness comprises a first circuit board, a second circuit board, a third circuit board, a first copper foil, a second copper foil and a plurality of semi-solidified sheets, the first circuit board, the first copper foil, the second circuit board, the second copper foil and the third circuit board are sequentially stacked from top to bottom, and the semi-solidified sheets are arranged between two adjacent circuit boards and copper foils, a plating hole is arranged on the surface of the second circuit board in contact with the semi-solidified sheet, a groove is formed on the top surface of the plating hole, and a protrusion is arranged on the corresponding position of the semi-solidified sheet; a pre-hollowing area is further arranged on the circuit board, and a copper ring is arranged on the outer side of the pre-hollowing area.

[0005] Further, a first solder resist layer and a second solder resist layer are further arranged on the outer surface of the first circuit board or the second circuit board, the outer surface of the first solder resist layer is in a stepped shape, and the outer surface of the second solder resist layer is arranged in a horizontal manner.

[0006] Further, a reinforcing plate is further included, the inner surface of the reinforcing plate is provided with protrusions and recess structures, and the protrusions and recess structures correspond to the protrusions and recesses on the outer surface of the first circuit board or the third circuit board.

[0007] Further, the inner surface of the reinforcing plate is provided with a plurality of protrusions and recess structures.

[0008] Further, the first circuit board and the third circuit board each comprise a base layer and a circuit layer, and the circuit layer is formed on the outer surface of the base layer.

[0009] Further, the third circuit board is a single-layer board, and the circuit layer of the third circuit board is arranged on one side of the prepreg.

[0010] In conclusion, the high-density multi-layer interconnection circuit board structure with optimized surface flatness has the advantages that the copper foil layer is arranged in the board, and the copper plate body is arranged on the outer side, so that the pressure resistance can be improved; the copper foil is arranged on the outer side of the circuit board, and the copper foil will be warped when being pressed multiple times; the copper foil is arranged on the inner side, so that the product thickness can be thinned, and the unevenness caused by the copper filling surface depression of the blind hole is reduced; in addition, the reinforcing structure and the reinforcing plate structure arranged between the prepreg and the circuit board can improve the flatness of the circuit board to a certain extent; the high-density multi-layer interconnection circuit board structure with optimized surface flatness has high practicability and strong popularization significance. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Fig. 1 is a sectional view of a first embodiment of a structure schematic diagram of the high-density multi-layer interconnection circuit board structure with optimized surface flatness according to the present application;

[0012] Figure 2 Fig. 2 is a schematic diagram of a pre-hollowing area of a circuit board according to the present application; Figure 1

[0013] Fig. 3 is a schematic diagram of a prepreg and a circuit board according to the present application; Figure 3 Figure 1 Fig. 4 is a schematic diagram of a circuit board surface flatness structure according to another embodiment of the present application;

[0014] Figure 4 Fig. 5 is a third embodiment of a structure schematic diagram of the high-density multi-layer interconnection circuit board structure with optimized surface flatness according to the present application.

[0015] DETAILED DESCRIPTION Figure 5 In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0016] As

[0017] As Figures 1 to 3 ​As shown, it provides a kind of high-density multilayer interconnection circuit board structure of optimization surface flatness.The high-density multilayer interconnection circuit board structure of optimization surface flatness includes first circuit board 10,second circuit board 20,third circuit board 30,first copper foil 40,second copper foil 50 and several prepregs 60,first circuit board 10,first copper foil 40,second circuit board 20,second copper foil 50,third circuit board 30 are stacked in turn from top to bottom, and prepreg 60 is arranged between two adjacent circuit boards and copper foil, to facilitate heat curing and pressing.

[0018] The second circuit board 20 is provided with an electroplating groove, and the electroplating groove is filled with a plating layer. The top surface of the plating layer is provided with a groove. The corresponding prepreg 60 of the second circuit board 20 is formed with a boss, and the shape of the boss is substantially the same as the size of the groove. Thus, when stacking, the protruding part is embedded into the corresponding groove; when hot-pressing, the recess can be reduced.

[0019] The outer surface of the high-density multilayer interconnection circuit board structure of optimization surface flatness is provided with a copper-free pre-hollowing area 70, and the periphery of the copper-free pre-hollowing area 70 is provided with a copper ring 80. Thus, the probability of board warping can be reduced, and the flatness yield can be improved. In this embodiment, the third circuit board 30 is a single-layer board, and the circuit layer is arranged on one side of the prepreg 60; thus, when pressing multiple times, the problem of copper foil warping can be avoided.

[0020] In another embodiment, the outer surface of the first circuit board 10 or the second circuit board 20 is also provided with a first solder resist layer 11 and a second solder resist layer 12. The thickness of the first solder resist layer 11 is less than the thickness of the PAD, and the second solder resist layer 12 covers the outer surface of the first solder resist layer 11. The outer surface of the first solder resist layer 11 is stepped, and the outer surface of the second solder resist layer 12 is horizontally arranged.

[0021] In a third embodiment, the outer surface of the high-density multilayer interconnection circuit board structure of optimization surface flatness is also provided with a reinforcing plate 80. The inner surface of the reinforcing plate 80 is provided with a groove or a protruding part, which corresponds to the positions of holes, grooves, hollows, etc. More specifically, the high-density multilayer interconnection circuit board structure of optimization surface flatness is normally pressed first, and then the corresponding recesses and protrusions are prepared on the reinforcing plate according to the recesses and protrusions on the surface. Thus, when pressing, the protrusions of the reinforcing plate 80 will further extrude the prepreg 60, so that the original protrusions on the circuit board become flat, and the recesses are extruded to become recessed, so that the prepreg 60 at this position becomes thick and no longer recessed. The reinforcing plate 80 can be arranged on the top surface or the bottom surface or both the top surface and the bottom surface according to requirements, which is not limited herein.

[0022] In summary, the utility model discloses a kind of high-density multilayer interconnection circuit board structure of optimization surface flatness is by being arranged copper foil layer in board, copper plate body is arranged on outside, can improve pressure resistance, copper foil is arranged in circuit board outside, when multiple compression, there is the problem of copper foil warping plate.But copper foil is arranged in inside, not only can thin product thickness, and reduce the uneven problem caused by the depression of blind hole copper filling surface.In addition, the reinforcing structure between the prepreg 60 and the circuit board, the setting of the reinforcing plate 80 structure, can also improve the flatness of the circuit board to some extent.The utility model has strong practicability and strong popularization significance.

[0023] The above-described embodiments only express three kinds of embodiments of the utility model, and the description is more specific and detailed, but it cannot be understood as the limitation of the utility model patent scope. It should be pointed out that for ordinary skilled person in the art, without departing from the concept of the utility model, a number of modifications and improvements can be made, which belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent should be subject to the appended claims.

Claims

1. A high density multilayer interconnect circuit board structure optimized for surface flatness, characterized by: The application relates to a circuit board, which comprises a first circuit board, a second circuit board, a third circuit board, a first copper foil, a second copper foil and a plurality of prepregs, wherein the first circuit board, the first copper foil, the second circuit board, the second copper foil and the third circuit board are stacked in sequence from top to bottom, the prepregs are arranged between two adjacent circuit boards and copper foils, a plating hole is arranged on a surface of the second circuit board in contact with the prepreg, a groove is formed on the top surface of the plating hole, and a protrusion is arranged on a corresponding position of the prepreg; and a pre-hollowing area is further arranged on the circuit board, and a copper ring is arranged on the outer side of the pre-hollowing area.

2. A high density multilayered interconnection circuit board structure for optimizing surface flatness as recited in claim 1, wherein: A first solder resist layer and a second solder resist layer are further arranged on the outer surface of the first circuit board or the second circuit board, the outer surface of the first solder resist layer is in a stepped shape, and the outer surface of the second solder resist layer is horizontally arranged.

3. A high density multilayered interconnection circuit board structure for optimizing surface flatness as recited in claim 1, wherein: The application further relates to a reinforcing plate, wherein a protrusion and a recess structure are arranged on the inner surface of the reinforcing plate, and the protrusion and the recess structure correspond to the protrusion and the recess on the outer surface of the first circuit board or the third circuit board.

4. The high density multilayered interconnection printed circuit board structure for optimizing surface flatness according to claim 3, wherein: The inner surface of the reinforcing plate is provided with a plurality of protrusions and recesses.

5. The high-density multilayer interconnect circuit board structure with optimized surface flatness as described in claim 3, characterized in that: The first circuit board and the third circuit board each comprise a base layer and a circuit layer, and the circuit layer is formed on the outer surface of the base layer.

6. A high density multilayered interconnection circuit board structure for optimizing surface flatness as recited in claim 5, wherein: The third circuit board is a single-layer board, and the circuit layer is arranged on one side of the prepreg.

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