A method for improving the oxidation surface delamination of a PCB sub-outer layer.

Abstract

The application discloses a PCB secondary outer layer and a method for improving PCB secondary outer layer oxidation surface board explosion, and belongs to the technical field of PCBs. The method comprises the following steps: selecting PP of M8 grade material and a substrate matched with HVLP3 grade copper foil as a PCB substrate; setting an independent hole on the exposed outer layer of the substrate, and setting a large hole concentric with the independent hole and having a diameter larger than that of the independent hole; setting a large copper surface outside a pad of the large hole with a distance of at least 20 mil; and obtaining a designed outer layer pattern. The designed outer layer pattern is subjected to the processes of brown oxidation, pressing, drilling, copper plating, outer layer pattern etching and solder mask, so that a test board is prepared, and the problem of secondary outer layer oxidation surface board explosion is effectively solved.

Description

Technical Field

[0001] This invention relates to a PCB sub-outer layer and a method for improving the PCB sub-outer layer oxide surface cracking, belonging to the field of PCB technology. Background Technology

[0002] With the continuous upgrading of electronic products, the number of layers, thickness, and electrical performance of PCBs are constantly increasing. To meet product requirements and improve electrical performance, the roughness of the copper foil on the PCB substrate is constantly being reduced, and the resin glass cloth also needs to be continuously upgraded and optimized. At the same time, the roughness of the browning process is also being continuously reduced.

[0003] Because the peel strength of high-grade materials generally weakens after browning, the oxide surface is prone to cracking, especially after thermal stress-induced tin drift or reflow soldering, which exacerbates the problem. Current PCB industry improvement methods include: releasing substrate stress and removing moisture through baking after browning; improving the roughness of the browning process, but this can affect the PCB's electrical performance; or replacing the outermost layer with a non-signal layer and using RTF copper foil with higher roughness. None of these methods effectively solve the outermost oxide surface cracking problem without affecting other performance characteristics. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the PCB secondary outer layer oxide surface cracking. By modifying the non-functional graphic design of the outer layer, the problem of secondary outer layer oxide surface cracking is solved.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for improving the delamination of the oxide surface of a PCB's second outermost layer, comprising:

[0007] PP of M8 grade and substrate with HVLP3 grade copper foil were selected as PCB substrate;

[0008] Independent holes are set in the outer layer of the exposed substrate, and large holes are concentric with the independent holes and have a larger diameter than the independent holes. The area at least 20mil away from the pad of the large hole is set as a large copper surface to obtain the designed outer layer pattern.

[0009] The outer layer pattern after design is subjected to browning, lamination, drilling, copper plating, outer layer pattern etching and solder masking processes to produce the test board.

[0010] In conjunction with the first aspect, the browning further includes browning the PCB substrate using a low-roughness browning solution with a roughness specific surface area of ​​9%-13%.

[0011] Furthermore, the test board has a thickness of not less than 200 mil and a number of layers of not less than 32L.

[0012] Furthermore, the diameter of the large hole is at least 1.0 mm greater than that of the individual holes.

[0013] In a second aspect, the present invention provides a PCB sub-outer layer, which is prepared according to a method for improving the delamination of the PCB sub-outer layer oxide surface as described in any of the preceding claims.

[0014] Furthermore, after the PCB sub-outer layer is sliced ​​at positions with different apertures and subjected to at least six tin-bleaching operations or ten reflow operations, the PCB sub-outer layer without oxide surface cracking occurs.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0016] This invention improves the PCB surface cracking of the sub-outer oxide layer by reasonably setting the outer layer pattern without changing the original PCB data. Compared with the existing technology that improves processing parameters or changes raw materials, it effectively reduces costs and improves efficiency. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for improving the delamination of the second outermost oxide surface of a PCB, provided by an embodiment of the present invention.

[0018] Figure 2 This is the original design of the outer layer pattern and the design drawing of the anti-bursting plate of the secondary outer layer oxidation surface provided in the embodiments of the present invention;

[0019] Figure 3 This is a schematic diagram of the outermost anti-oxidation surface of the PCB cross-section after lamination, provided in an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the outermost layer of the PCB cross-section after lamination provided in an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of a PCB cross-section provided in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0023] like Figure 1 The diagram shown is a flowchart of a method for improving the delamination of the second outermost oxide layer of a PCB according to an embodiment of the present invention, which mainly includes the following steps:

[0024] 1) Select sample materials and browning solution;

[0025] In this embodiment, M8 grade PP material and HVLP3 grade copper foil are selected as the substrate, and a high-speed browning agent with a roughness specific surface area of ​​9-13% is selected for browning.

[0026] 2) Test board graphic design;

[0027] Design a test board with a thickness of 200mil and 32L layers.

[0028] Design different ball grid arrays, including independent holes and large holes with a diameter at least 1.0 mm larger than the independent holes.

[0029] like Figure 2 As shown in the diagram, the left-hand side shows the original design, while the right-hand side shows the design to prevent the outermost layer from oxidizing and bursting. Specifically, on the exposed outer layer of the substrate, the area surrounding the large hole pads (at least 1.0mm away from the independent holes) with a distance of 20mil is designed as a large copper surface.

[0030] 3) Test board fabrication;

[0031] like Figure 3 The image shown is a schematic diagram of the outermost anti-oxidation surface of the PCB after lamination, indicating a potential PCB breakage. Figure 4 This is a schematic diagram of the outermost layer of the PCB cross-section after lamination.

[0032] The browning process uses a high-speed browning solution with a roughening degree and specific surface area of ​​9-13% to brown the substrate, followed by lamination, drilling, copper plating, outer layer pattern etching, and solder masking.

[0033] 4) Conduct the test;

[0034] After the test board is manufactured, slices are taken from different hole diameters. After at least six tin-bleeding cycles or ten reflow cycles, it is confirmed whether there is any oxide surface cracking on the outermost layer.

[0035] In this embodiment, tin bleaching was performed six times to check for any board breakage on the outermost oxide layer. Figure 5 The images show cross-sectional views of a PCB board. Figure a shows the oxide layer of the second outermost layer after six tin bleaching cycles, and Figure b shows the oxide layer of the second outermost layer after ten reflow cycles. Figure 5 As can be seen from the above, the method for improving the PCB secondary outer layer oxide surface explosion provided by the present invention can be implemented without changing customer information, is easy to operate, and can be optimized and improved at the source design stage, which can effectively avoid the scrapping of PCB boards.

[0036] 5) Judgment criteria: After thermal stress, cross-section is used to confirm whether there is oxidized surface cracking in the outermost layer.

[0037] For those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A method for improving the delamination of the oxidized surface of the secondary outer layer of a PCB, characterized in that, The application relates to a PCB substrate and a test board. The PCB substrate comprises: A PP material of M8 grade is selected as a PCB substrate; An independent hole is arranged on an exposed outer layer of the substrate, and a large hole is arranged concentrically with the independent hole and has a diameter larger than that of the independent hole; a large copper surface is arranged outside a pad of the large hole at a distance of at least 20 mil, so as to obtain a designed outer layer pattern; 2. The method for improving the PCB secondary outer layer oxidation surface explosion board according to claim 1, characterized in that, The designed outer layer pattern is subjected to processes of brown oxidation, pressing, drilling, copper plating, outer layer pattern etching and solder mask, so as to obtain the test board.

3. The method of claim 1, wherein the method further comprises: The brown oxidation comprises using a low-roughness brown oxidation solution with a roughness degree ratio of 9%-13% to brown the PCB substrate.

4. The method of claim 1, wherein the method further comprises: The test board has a thickness not less than 200 mil and a layer number not less than 32L. The large hole has a diameter at least 1.0 mm larger than that of the independent hole.

Images