A method for solving the problem of whitening of secondary drilling holes in aluminum substrates

Abstract

The present invention discloses a method for resolving the whitening problem of the openings of secondary drilled holes in aluminum substrates. This method belongs to the technical field of PCB processing and addresses the technical problem of whitening of the openings of secondary drilled holes in aluminum substrates. Prior to secondary drilling, a mold is placed on a backing plate to support the PP layer directly below the NPTH hole, and then the normal secondary drilling process is performed. By placing a mold on the backing plate to support the PP layer directly below the NPTH hole, the present invention effectively resolves the problem of the opening being suspended and unstressed, effectively preventing the abnormal phenomenon of whitening or cracking of the openings, improving the undesirable cracking defect of the openings of secondary drilled holes in aluminum substrates and increasing the quality yield.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB board processing technology, and more particularly, to a method for solving the problem of whitening of secondary drilling holes in aluminum substrates. Background Art

[0002] like Figure 1 As shown, some NPTH holes B in the double-sided aluminum substrate A need to be etched and then drilled out again. Because the outer layer of the aluminum substrate A (PP layer C + copper layer D) is generally relatively thick, about 2 to 3 ounces, after etching, a height difference appears between the lower surface of the copper layer D and the PP layer C, that is, there is a height difference between the lower surface of the copper foil of the aluminum substrate A and the PP layer C. When secondary drilling is required, due to the height difference, the PP layer C cannot be overlapped with the pad E. The drill bit F is not subjected to force when drilling the NPTH hole B, which is prone to abnormal phenomena such as whitening G or edge bursting of the hole. This phenomenon will reduce the reliability of the PCB board. In the communications industry, especially in 5G communications, this phenomenon must be strictly controlled. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art, and the purpose of the present invention is to provide a method for solving the problem of whitening of the openings of secondary drilling holes in aluminum substrates.

[0004] The technical solution of the present invention is: a method for solving the whitening of the secondary drilling hole of the aluminum substrate. Before the secondary drilling, a mold is first set on the pad to support the PP layer directly below the NPTH hole, and then the normal secondary drilling process is carried out.

[0005] As a further improvement, the mold includes a bottom plate, which is in contact with a pad. The top of the bottom plate is provided with a boss aligned with the NPTH hole, the boss is in contact with the PP layer, and the top surface size of the boss is larger than the cross-sectional size of the NPTH hole.

[0006] Furthermore, the top surface size of the boss is smaller than the window size of the outer line pattern of the copper layer at the position of the aluminum substrate corresponding to the NPTH hole.

[0007] Furthermore, the height of the boss is greater than the height of the copper layer of the aluminum substrate by more than half an ounce.

[0008] Furthermore, the size of the boss of the mold is such that the diameter of the NPTH hole is enlarged by more than 4 mil on one side.

[0009] Furthermore, the bottom plate is a substrate, and the boss is surface copper plated onto the substrate.

[0010] Furthermore, the thickness of the bottom plate is smaller than the height of the copper layer of the aluminum substrate.

[0011] Furthermore, the size of the mold is the same as that of the aluminum substrate.

[0012] Furthermore, the mold is provided with a target, and the target of the mold is consistent with the target of the aluminum substrate.

[0013] Furthermore, the expansion and contraction of the mold after pressing is exposed.

[0014] Beneficial effects

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] The present invention supports the PP layer directly below the NPTH hole by arranging a mold on the pad, which can effectively solve the problem that the hole mouth is suspended in the air without being subjected to force, and can effectively prevent the abnormal phenomenon of the hole mouth turning white or bursting, thereby improving the undesirable defect of the hole mouth bursting in the secondary drilling of the aluminum substrate and improving the quality yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the traditional secondary drilling method;

[0018] Figure 2 Schematic diagram of the secondary drilling method of the present invention.

[0019] Among them: 1- pad, 2- mold, 21- base plate, 22- boss, 3- NPTH hole, 4- PP layer, 5- aluminum substrate, 6- copper layer, 7- drill bit. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the specific embodiments in the accompanying drawings.

[0021] See Figure 2 A method for solving the whitening of the secondary drilling hole of the aluminum substrate. Before the secondary drilling, a mold 2 is set on the pad 1 to support the PP layer 4 directly below the NPTH hole 3, and then the normal secondary drilling process is carried out.

[0022] Specifically, the mold 2 includes a base plate 21, which contacts the pad 1. A boss 22 aligned with the NPTH hole 3 is provided on the top of the base plate 21, that is, the boss 22 is located directly below the NPTH hole 3, and the boss 22 contacts the PP layer 4. The top surface size of the boss 22 is larger than the cross-sectional size of the NPTH hole 3. When drilling, the drill bit 7 drills into the boss 22, and the boss 22 supports the PP layer 4 directly below the NPTH hole 3, which can effectively solve the problem of the hole opening being suspended and not subject to force, and can effectively prevent the abnormal phenomenon of the hole opening turning white or bursting, thereby improving the undesirable defect of the hole opening bursting during secondary drilling of the aluminum substrate and improving the quality yield.

[0023] The top surface size of the boss 22 is smaller than the window size of the outer line pattern of the copper layer 6 at the position of the aluminum substrate 5 corresponding to the NPTH hole 3, which can prevent the boss 22 from pressing on the copper layer 6 of the aluminum substrate 5.

[0024] The height of the boss 22 is more than half an ounce larger than the height of the copper layer 6 of the aluminum substrate 5. The size of the boss 22 of the mold 2 is the diameter of the NPTH hole 3 increased by more than 4 mil on one side, that is, the size of the boss 22 is greater than the diameter of the NPTH hole 3 + 8 mil. This prevents the boss 22 from supporting too little area of ​​the PP layer 4 and affecting the solution to the problem of the hole being suspended in the air without force.

[0025] Preferably, the bottom plate 21 is a substrate, and the boss 22 is surface copper plated onto the substrate.

[0026] The thickness of the bottom plate 21 is smaller than the height of the copper layer 6 of the aluminum substrate 5. The size of the mold 2 is the same as that of the aluminum substrate 5. The mold 2 is provided with a target. The target of the mold 2 is consistent with the target of the aluminum substrate 5. The expansion and contraction of the mold 2 after pressing is exposed, which serves to improve the alignment of the boss 22 and the window.

[0027] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for solving the whitening of the secondary drilling hole of the aluminum substrate, characterized in that: Before secondary drilling, a mold (2) is first set on the backing plate (1) to support the PP layer (4) around the lower end of the NPTH hole (3), the PP layer (4) is located on the surface of the aluminum substrate (5) facing the mold (2), and the copper layer (6) is located at the bottom of the PP layer (4), and then the secondary drilling process is performed; The mold (2) comprises a bottom plate (21), the bottom plate (21) contacts the backing plate (1), a boss (22) aligned with the NPTH hole (3) is provided on the top of the bottom plate (21), the boss (22) contacts the PP layer (4), and the top surface size of the boss (22) is larger than the cross-sectional size of the NPTH hole (3); The top surface size of the boss (22) is smaller than the window size of the copper layer (6) at the position corresponding to the NPTH hole (3); The height of the boss (22) is greater than the height of the copper layer (6) of the aluminum substrate (5) by more than half an ounce; The size of the boss (22) of the mold (2) is the diameter of the NPTH hole (3) increased by more than 4 mil on one side.

2. A method for solving the whitening of the secondary drilling hole of the aluminum substrate according to claim 1, characterized in that: The bottom plate (21) is a substrate, and the boss (22) is surface copper plated onto the substrate.

3. A method for solving the whitening of the secondary drilling hole of the aluminum substrate according to claim 1, characterized in that: The thickness of the bottom plate (21) is less than the height of the copper layer (6) of the aluminum substrate (5).

4. The method for solving the whitening of the secondary drilling hole of the aluminum substrate according to claim 1, characterized in that: The size of the mold (2) is the same as the size of the aluminum substrate (5).

5. The method for solving the whitening of the secondary drilling hole of the aluminum substrate according to claim 1, characterized in that: The mold (2) is provided with a target, and the target of the mold (2) is consistent with the target of the aluminum substrate (5).

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