Method for manufacturing small-aperture back drill hole without residual wires

Abstract

The invention relates to a manufacturing method for no residual wire in a small-aperture back drilling hole, which comprises the following steps of: (1) copper plating: designing an electroplating manufacturing process, plating a small amount of hole copper during hole copper manufacturing, and taking the copper plating thickness as the criterion of ensuring copper connected with the hole and copper loss in the subsequent process; (2) tin plating: tin plating is carried out on the whole plate surface, and a small amount of hole copper is electroplated in the previous steps, so that the thickness-diameter ratio of tin plating is reduced, and the tin plating and hole filling effect is met; (3) back drilling is conducted, specifically, back drilling is conducted on the tinned plate according to the product requirement, manufacturing is conducted according to the finished product requirement on the basis that stub is guaranteed, plating in a to-be-drilled hole is reduced, then back drilling is conducted, the hole blocking risk is reduced, and a small number of residual wires exist in the hole; (4) residual wire removal: removing residual wires in the holes by adopting alkaline etching, and then stripping tin to avoid the residual wires in the holes; and (5) plating: after cleaning, plating copper on the hole surface to the copper thickness required by the product. The method has the advantages that the tinning capability is met, the residual wire is prevented from blocking the hole, and the quality hidden danger is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of circuit board processing, in particular to a method for manufacturing a small-diameter back-drilled hole without residual wire. Background Art

[0002] Back drilling is mainly to remove the copper plating on the hole wall and reduce the transmission signal loss. However, with the continuous increase in product functions and density, the aperture requirements for back drilling holes also need to become smaller and smaller. As a result, the deviation in positioning accuracy during the production process will cause the problem of residual wire blocking the hole. The conventional tin plating after completing the copper hole cannot meet the deep plating capacity of the current tin plating, and there will be a series of problems such as hole breakage, residual debris blocking the hole, or conventional tin plating is not performed, but the back drilling residual wire cannot be handled due to the small hole.

[0003] At present, many communication boards and server products have multi-layer thickness of 2.5mm or more, and due to the dense wiring of the products, the aperture will be smaller. For example, if the hole diameter of the drilling tool is 0.2mm, and the back drilling is 0.35mm or 0.4mm, plus the hole copper requirements, the finished product aperture is 0.15mm or smaller, and the thickness-to-diameter ratio reaches more than 16.6, which exceeds the conventional tin plating production capacity and cannot be tinned, resulting in the problem of back drilling residual wire in the hole. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of insufficient existing tin plating capacity and inability to handle residual wire in back-drilled holes, and to provide a method for producing small-diameter back-drilled holes without residual wire, which can meet the tin plating capacity while avoiding residual wire clogging the holes and reducing quality risks.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A method for producing a small-diameter back-drilled hole without residual wire, the specific steps comprising: (1) Copper plating: Design the electroplating process. When making hole copper, first plate a small amount of hole copper. The thickness of the copper plating should be based on ensuring the copper connection of the hole and the loss of copper in the subsequent process; (2) Tin plating: Tin plating is performed on the entire board surface. Due to the small amount of copper plated in the holes in step (1), the thickness-to-diameter ratio of the tin plating is reduced, thus satisfying the tin plating hole filling effect; (3) Back drilling: The tinned board is back drilled according to the product requirements. The stub is ensured to be produced according to the finished product requirements. The plating in the hole to be drilled is reduced before back drilling, which reduces the risk of hole blockage, but there will still be a small amount of residual wire in the hole; (4) Removing residual wire: Use alkaline etching to remove the residual wire in the hole, and then strip the tin to avoid residual wire in the hole; (5) Re-plating: After cleaning, re-electroplating is performed to re-plate the hole surface copper to the copper thickness required by the product.

[0006] Furthermore, in step (1), the electroplating thickness of the hole copper is recommended to be 4-6 μm.

[0007] Furthermore, in the step (5), when the copper plating is performed, the stub in the hole will increase. According to the thickness of the copper plating, the stub back-drilled in the step (3) should be compensated accordingly.

[0008] Compared with the prior art, the advantages of the technical solution of the present invention are: (1) The present invention reduces the thickness-to-diameter ratio by reducing the thickness of the copper plated once, thereby effectively avoiding the problem of insufficient tinning capacity and the inability to tinnize; (2) The present invention adopts the method of first plating a small amount of copper and then plating tin. Alkaline etching can be used to remove the residual wire in the hole, thereby avoiding hole blocking, facilitating the processing of subsequent process products, and reducing quality risks; (3) The present invention adopts the method of layered electroplating to complete the hole copper, which avoids the problem of quality hole blocking and residual wire, ensures the loss impact of customer use, and meets customer needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic flow chart of the method for producing a small-diameter back-drilled hole without residual wire according to the present invention. DETAILED DESCRIPTION Example

[0010] To make the present invention more clear, a method for making a small-diameter back-drilled hole without residual wire of the present invention is further described below in conjunction with the accompanying drawings. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0011] See also Figure 1 , a method for making a small-diameter back-drilled hole without residual wire, characterized in that: S1, copper plating: design the electroplating process, first plate a small amount of hole copper when making hole copper, the thickness of copper plating should be based on the guarantee of hole connection copper and loss copper in the subsequent process, 4~6μm is recommended; S2, tin plating: tin plating is performed on the entire board surface. Due to the small amount of electroplated hole copper in step (1), the thickness-to-diameter ratio of tin plating is reduced, thus satisfying the tin plating hole filling effect; S3, back drilling: the tinned board is back drilled according to the product requirements, and the stub is made according to the finished product requirements. The plating in the hole to be drilled is reduced before back drilling, which reduces the risk of hole blockage, but there will still be a small amount of residual wire in the hole; S4, remove residual wire: use alkaline etching to remove the residual wire in the hole, and then strip the tin to avoid residual wire in the hole; S5, additional plating: After cleaning, the copper on the hole surface is electroplated again to the copper thickness required by the product. During this process, the stub in the hole will increase. According to the thickness of the additional copper, the stub back-drilled in step (3) must be compensated accordingly.

[0012] The present invention reduces the thickness-to-diameter ratio of subsequent tin plating by plating a small amount of copper in the early stage, effectively avoids insufficient tin plating capacity and inability to tin plating, improves the tin-filling effect, and uses alkaline etching to remove residual wire in the hole after back drilling, avoids hole blockage, is beneficial to the processing of subsequent process products, reduces quality risks, and meets customer needs.

[0013] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for producing a small-diameter back-drilled hole without residual wire, characterized in that: (1) Copper plating: Design the electroplating process. When making hole copper, first plate a small amount of hole copper. The thickness of the copper plating should be based on ensuring the copper connection of the hole and the loss of copper in the subsequent process; (2) Tin plating: Tin plating is performed on the entire board surface. Due to the small amount of copper plated in the holes in step (1), the thickness-to-diameter ratio of the tin plating is reduced, thus satisfying the tin plating hole filling effect; (3) Back drilling: The tinned board is back drilled according to the product requirements. The stub is ensured to be produced according to the finished product requirements. The plating in the hole to be drilled is reduced before back drilling, which reduces the risk of hole blockage, but there will still be a small amount of residual wire in the hole; (4) Removing residual wire: Use alkaline etching to remove the residual wire in the hole, and then strip the tin to avoid residual wire in the hole; (5) Re-plating: After cleaning, re-electroplating is performed to re-plate the hole surface copper to the copper thickness required by the product.

2. The method for producing a small-diameter back-drilled hole without residual wire according to claim 1, characterized in that: In the step (1), the electroplating thickness of the hole copper is recommended to be 4-6 μm.

3. The method for producing a small-diameter back-drilled hole without residual wire according to claim 1 or 2, characterized in that: In the step (5), when the copper is plated, the stub in the hole will grow. According to the thickness of the plated copper, the stub back-drilled in the step (3) needs to be compensated accordingly.

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