CN103687306A - A printed circuit board and its manufacturing method - Google Patents

Abstract

The invention provides a manufacturing method of a printed circuit board. The method comprises the following steps: obtaining a mother board by laminating a plurality of insulated laminated daughter boards; fabricating a through hole in the mother board; enlarging the through hole at the part of outer daughter boards; the connection part of the enlarged part of the through hole and the original part of the through hole is contained in a single insulating layer; plating the mother board; removing metal at the connection part. The invention further provides the printed circuit board manufactured by the method. According to the invention, the manufacturing quality of the printed circuit board is improved.

Description

A printed circuit board and its manufacturing method

technical field

The invention relates to the field of printed circuit boards (PCBs), in particular to a printed circuit board and a manufacturing method thereof.

Background technique

Today's PCB design adopts back drilling and blind buried hole design, which can reduce signal loss and crosstalk, and can increase the number of layers and density of wiring. At the same time, the plug-in hole has also developed from the previous single-sided plug-in hole to the latest double-sided plug-in hole. The number of integrated chips is doubled compared with the original single-sided plug-in, thereby reducing the number of PCB wiring layers and achieving the purpose of reducing PCB manufacturing costs.

The existing PCB double-sided plug-in hole processing technology is as follows (taking PCB processing with only one buried hole and single crimping hole depth as an example):

As shown in Figure 1, three sub-boards 1, 2, and 3 are laminated respectively, and the sub-boards 1, 2, and 3 are all multi-layer PCB boards;

Then, as shown in Figure 2, process through holes 11, 21, 31 on three sub-boards 1, 2, 3 respectively;

Next, as shown in Figure 3, after aligning the through holes 11, 21, and 31 on the three sub-boards 1, 2, and 3 (that is, the centerlines of the three through holes are on the same axis), use the prepreg to place the three through holes. Sub-boards 1, 2, and 3 are laminated and bonded together to form a PCB motherboard;

As can be seen from the above description, since the existing double-sided plug-in hole PCB board processing technology with a buried hole structure has at least two laminations, the process flow is long. In the lamination process of Fig. 3, the three sub-boards 1, 2 , 3. Misalignment often occurs, so that the through holes 11, 21, and 31 cannot be coaxially aligned, thereby affecting product quality.

Contents of the invention

The present invention aims to provide a PCB and its manufacturing method to solve the above problems.

In an embodiment of the present invention, a method for manufacturing a PCB is provided, comprising: obtaining a mother board by laminating a plurality of daughter boards laminated with insulating layers; making through holes on the mother board; enlarging the through holes on the outer daughter board Part of the aperture, the connection between the reamed part and the unexpanded part of the through hole is on an insulating layer; the motherboard is plated with metal; the metal on the connection is removed.

In an embodiment of the present invention, a PCB manufactured by the above manufacturing method is provided.

The PCB and its manufacturing method in the above-mentioned embodiments of the present invention adopt hole reaming method to make plug-in holes, which avoids the operation of aligning sub-boards, thus overcomes defects caused by alignment errors of sub-boards, and improves the manufacturing quality of PCB.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

FIG. 1 shows a schematic diagram of each sub-board provided by the prior art;

Fig. 2 shows the schematic diagram of processing through holes on each sub-board provided by the prior art;

Figure 3 shows a schematic diagram of laminating each sub-board provided by the prior art;

FIG. 4 shows a schematic diagram of a motherboard provided by an embodiment of the present invention;

FIG. 5 shows a schematic diagram of forming a through hole on a motherboard provided by an embodiment of the present invention;

Fig. 6 shows a schematic diagram of external reaming along the centerline of the through hole in Fig. 5;

Fig. 7 shows a schematic diagram of forming a stepped hole and a buried hole along the center line of the stepped through hole in Fig. 6;

8 shows a schematic diagram of a PCB with double-sided plug-in holes with different buried hole depths finally produced in the embodiment of the present invention;

FIG. 9 shows a flow chart of a PCB manufacturing method according to an embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

Fig. 9 shows the flow chart of the manufacturing method of PCB according to the embodiment of the present invention, including:

Step S10, laminating multiple sub-boards stacked with insulating layers to obtain a motherboard;

Step S20, making through holes on the motherboard;

Step S30, enlarging the diameter of the through hole on the outer sub-board, and the connection between the expanded part and the unexpanded part of the through hole is on an insulating layer;

Step S40, plating the motherboard with metal;

Step S50, removing the metal on the connection part.

In the prior art, plug-in holes are made by aligning sub-boards. When through holes used to make plug-in holes cannot be coaxially aligned, the quality of the PCB will be affected. However, in this embodiment, the hole expansion method is used to make the plug-in holes, and it is not necessary to align the through holes of the daughter boards for making the plug-in holes coaxially, thereby avoiding the defects caused by the misalignment of the daughter boards, and improving the PCB. product quality.

Fig. 4 is a schematic diagram of a mother board provided by the embodiment of the present invention. A plurality of daughter boards are arranged, and the daughter boards are tightly bonded together by pressing a prepreg (a kind of insulating layer, prepreg is used as an example below) to form a mother board. plate.

FIG. 5 shows a schematic diagram of forming through holes on a motherboard provided by an embodiment of the present invention. Through-holes 51 are formed by drilling on the motherboard 5 .

FIG. 6 shows a schematic diagram of external reaming along the centerline of the through hole in FIG. 5 . On the center line of the through hole, the drill bit is used to carry out controlled depth drilling by adopting a drill bit larger than the aperture of the through hole, so as to enlarge the aperture of the through hole in the outer sub-board part. Preferably, taking the offset error into consideration, a drill bit that is 0.30mm-0.42mm larger than the diameter of the through hole is used for controlled depth drilling. As shown in Fig. 6, the through hole 52 is processed by deep drilling on both sides of the center line of the through hole 51. The through hole 52 is a stepped hole, and the diameter of the drill tip of the stepped hole part is 0.30mm-0.42 larger than the diameter of the through hole 51. mm.

FIG. 7 shows a schematic diagram of forming a stepped hole and a buried hole along the centerline of the stepped through hole in FIG. 6 . On the center line of the through hole, back drilling is performed to remove the metal on the connecting part by using a drill bit with a diameter larger than that of the unexpanded part of the through hole and smaller than that of the reamed part. Preferably, the thickness of the metal plating is 25-35um. The motherboard can be electroplated, so that the walls of the through holes 52 are electroplated with a metal copper layer, and the thickness of the metal copper layer is 25-35um. Preferably, the back drilling is carried out by using a drill bit which is 0.12 mm to 0.18 mm larger than the diameter of the unexpanded part of the through hole and 0.18 mm to 0.22 mm smaller than the diameter of the reamed part. As shown in FIG. 7 , back-drill on both sides along the centerline of the stepped through hole 52, the depth requirement is to drill off the metal copper at the stepped connection part of the through hole 51 and the stepped through hole 52, and process a stepped hole 53 and a buried hole 54. The diameter of the back drill bit is required to be 0.15 mm larger than the diameter of the through hole 51, and 0.2 mm smaller than the diameter of the stepped through hole 52; by comparing the size of the back drill bit and the stepped through hole 52, it can be known that the diameter of the back drill bit is more than The diameter of the stepped through hole 52 is 0.2mm smaller, and the thickness of the metal copper layer plated on the inner wall of the stepped through hole is 25-35um, so the metal copper on the wall of the stepped through hole 52 will not be damaged during the back drilling process, so the The copper in the stepped connection part of the stepped through hole 52 is removed to insulate the inner wall of the stepped through hole 52. The original stepped through hole 52 forms a stepped hole 53, and the original through hole 51 forms a buried hole 54. When the depth is different from that of the back-drilling, stepped holes 53 and buried holes 54 of different depths can be made, so that a PCB with double-sided plug-in holes with a buried hole structure can be made.

Preferably, the diameters of the through holes at the two opposite outer sub-boards are enlarged, and the finally formed through holes are double-sided plug-in holes. FIG. 8 shows a schematic diagram of a PCB with double-sided plug-in holes with different depths of buried holes finally produced in the embodiment of the present invention. Of course, if necessary, only one side of the through hole can be reamed to be processed into a single-sided plug-in hole.

In the prior art, because the double-sided plug-in holes of the final PCB board are blind holes, there are problems of blind holes hiding liquid and easy oxidation in the subsequent etching process, and there are also blind holes in the subsequent electroplating and surface treatment processes. The quality defect that the wall cannot be plated with metal. However, in the embodiment of the present invention, the metal is first plated, and then the metal on the connecting wall is removed with a drill bit, so the problem of blind hole hiding liquid and easy oxidation caused by the etching process of the prior art is avoided, and the problem of blind hole wall is also overcome. Quality defects that cannot be plated on metal.

Another embodiment of making double-sided plug-in holes is to drill the two outer sides of the motherboard with a larger diameter drill bit coaxially to control the depth drilling, make the buried holes on the two outer sides, then carry out metal plating, and then use a small diameter drill bit drills through the junction between the two outer bores. However, when a small-diameter drill bit is used to drill through the joint between the buried holes on the two outer sides, powder chips are easily generated, and the powder chips increase with the increase of the plate thickness and the diameter of the drill bit, and the powder chips are more difficult to discharge. However, the embodiments of FIGS. 4-9 of the present invention can avoid this problem.

When the PCB with double-sided plug-in holes with buried holes of different depths made by the above-mentioned embodiments of the present invention is used, the crimping PIN is inserted into the upper and lower stepped holes of the PCB. Since the inner wall of the stepped hole is insulated, the chip crimping process There will be no disconnection phenomenon. Compared with the existing double-sided plug-in PCB boards with different depths of buried holes, the embodiment of the present invention only needs one lamination, which greatly shortens the process flow and avoids the up and down of several existing sub-boards during lamination. Dislocation occurs in the blind holes. In addition, because the double-sided plug-in holes processed by the embodiment of the present invention are still through holes, it solves the problem that the double-sided plug-in holes or single-sided plug-in holes in the prior art are blind holes, which cause hidden medicine and easy oxidation. , Plating can not be metal and other problems, improve the processing quality of blind holes. The blind hole processed in this way has a smooth hole wall and less edge, the hole type is vertical, and the buried hole in the middle is a PTH hole, which can transmit signals.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. A method for making a printed circuit board, comprising: The mother board is obtained by laminating multiple sub-boards laminated with insulation; making through-holes on said motherboard; enlarging the aperture of the through hole on the outer sub-board part, and the connection part between the reamed part and the unexpanded part of the through hole is on one of the insulating layers; metallizing the motherboard; The metal on the connecting portion is removed. 2. The method according to claim 1, characterized in that, on the center line of the through hole, the depth control drilling is carried out by adopting a drill bit larger than the aperture of the through hole to enlarge the through hole Apertures in the outer daughterboard section. 3. The method according to claim 2, characterized in that, the controlled depth drilling is carried out using a drill bit which is 0.30mm-0.42mm larger than the aperture of the through hole. 4. The method according to claim 1, characterized in that, on the center line of the through hole, by adopting a larger aperture than the unexpanded portion of the through hole, and a larger diameter than the aperture of the reamed portion Small drill bits, backdrilled to remove metal from the connection. 5. The method according to claim 4, characterized in that, a drill that is 0.12 mm to 0.18 mm larger than the diameter of the unexpanded portion of the through hole and 0.18 mm to 0.22 mm smaller than the diameter of the expanded portion is used. Tsui, perform back drilling. 6. The method according to claim 5, characterized in that the thickness of the metal plating is 25-35um. 7. The method according to any one of claims 1-6, characterized in that the apertures of the through holes at the two opposite outer sub-boards are enlarged, and the finally formed through holes are double-sided plug-in holes. 8. A printed circuit board, characterized in that it is made by the method according to any one of claims 1-7.

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