A plate-on-board and its manufacturing method

Abstract

This invention discloses a method for manufacturing a board-on-board (Boardboard Board), addressing the problems of high manufacturing difficulty, low yield, long lead time, and high processing cost associated with existing Boardboard Boards using half-hole pads. The method includes: cutting the original copper-clad laminate (CCL); performing inner dry film treatment, browning, and lamination on the cut CCL to form a circuit board; drilling holes in the circuit board and metallizing the holes using copper plating to form vias; fabricating circuit patterns on the metallized circuit board and performing solder mask treatment to obtain a circuit board with via openings; and cutting the circuit board with via openings to predetermined dimensions to form the Board-on-board. This invention eliminates the need to cut the vias into half-holes, allows for milling 3-4 boards simultaneously, and simplifies the manufacturing process by requiring only one milling operation, thus improving production efficiency and reducing the risk of damage to the finished product.

Description

Technical Field

[0001] This invention relates to the field of solder pad technology, and in particular to an onboard board and its manufacturing method. Background Technology

[0002] Existing onboard module pads use half-hole type pads (also known as stamp hole pads), such as... Figure 1 As shown. The formation of this half-hole form is a complicated process in PCB manufacturing. It requires additional steps to create a complete via, cutting at the drilled area next to the via to split it open, followed by milling with a router, secondary milling for fine finishing, and strict control of milling speed and stack number. The milling time is more than twice that of a conventional PCB, which can easily lead to quality problems such as the half-hole peeling off from the substrate, copper peeling, and burr residue. The manufacturing process is difficult, the yield rate is low, the production lead time is long, and the processing cost is high.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an onboard board and its manufacturing method to address the shortcomings of the existing technology, thereby solving the problems of high board manufacturing difficulty, low finished product qualification rate, long production delivery time and high processing cost caused by the use of half-hole type pads in the existing onboard board module pads.

[0005] To address the aforementioned technical problems, a first aspect of this invention provides a method for manufacturing an onboard board, the method comprising the following steps:

[0006] The original copper-clad laminate is cut into pieces, and the cut copper-clad laminate is subjected to inner dry film, browning and lamination processes to form a circuit board.

[0007] Drill holes in the circuit board and metallize the holes by applying copper plating to form vias;

[0008] After the vias are metallized, circuit patterns are fabricated on the circuit board and solder mask treatment is performed to obtain a circuit board with via openings. During the solder mask process, the vias and the copper layer around the vias are exposed to form solder pads.

[0009] The circuit board with through-holes and windows is cut to a predetermined size to form a board substrate.

[0010] In one implementation, after the step of cutting the circuit board with via openings to predetermined dimensions to form an onboard board, the method further includes:

[0011] The copper surface of the solder pads on the onboard board is treated with an anti-oxidation treatment.

[0012] A second aspect of the present invention provides a board substrate, which is manufactured based on the board substrate manufacturing method described above. The board substrate includes a board body, the vias are pin through holes, the copper layer around the holes is a window area, the window area is located on the soldering surface of the board body, and each pin through hole has a preset distance from the side of the board body.

[0013] In one implementation, the window area on each pin via extends to the side of the board.

[0014] In one implementation, the depth of the hole wall of each pin via is at least 0.8 mm.

[0015] In one implementation, each pin via is provided with a circumferentially extending window wall located on the hardware mounting surface of the board.

[0016] In one implementation, the area of ​​the window opening region is larger than the area of ​​the window opening wall.

[0017] In one implementation, the window opening wall is an annular wall, and the annular radius of the annular wall is not less than 0.1 mm.

[0018] In one implementation, the pin via is a circular via.

[0019] In one implementation, the welding surface of the plate is a plane.

[0020] Beneficial effects: Previously, half-hole pads required drilling and cutting to form a half-hole on top of a via. The wall of the half-hole was exposed on the side of the half-hole board module pad, necessitating secondary milling for finishing. This also led to quality issues such as half-hole separation from the substrate, copper peeling, and burr residue. Only a maximum of two boards could be stacked during milling, resulting in low board production efficiency. This invention eliminates the need to cut the via into half-holes. During milling, 3-4 boards can be stacked and milled together in a single operation, simplifying the board manufacturing process, improving production efficiency, and reducing the risk of damage to the finished product. Attached Figure Description

[0021] Figure 1 A flowchart illustrating a method for manufacturing an onboard board provided by the present invention;

[0022] Figure 2 A schematic diagram of the structure of an onboard plate provided by the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of the welding surface of an onboard plate provided by the present invention;

[0024] Figure 4This invention provides a schematic diagram of the structure of an onboard board located on the hardware mounting surface.

[0025] Figure 5 A side view of a via opening window in a plate provided by the present invention;

[0026] Figure 6 This is an additional working diagram of the existing method for fabricating a semi-perforated plate carrier. Detailed Implementation

[0027] This invention provides an onboard board and its manufacturing method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0028] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0029] It should also be noted that the same or similar reference numerals in the accompanying drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] The invention will be further explained below with reference to the accompanying drawings and the description of the embodiments.

[0032] This embodiment provides a method for manufacturing an onboard board, such as... Figure 1 As shown, the manufacturing method includes the following steps:

[0033] Step 10: Cut the original copper-clad laminate into blanks, and then perform inner dry film treatment, browning and lamination on the cut copper-clad laminate to form a circuit board.

[0034] Step 20: Drill holes in the circuit board and metallize the holes by copper plating to form vias;

[0035] Step 30: Create circuit patterns on the circuit board after the vias are metallized, and perform solder mask treatment to obtain a circuit board with via openings. During the solder mask process, the vias and the copper layer around the vias are exposed to form pads.

[0036] Step 40: Cut the circuit board with through-hole openings to the predetermined size to form a board substrate.

[0037] Specifically, the "cutting" refers to the process of cutting the original copper-clad laminate into boards that can be manufactured on a production line; the "inner layer dry film" refers to the process of transferring the inner layer circuit patterns onto the board; the "browning" refers to the process of producing a uniform, highly adhesive organometallic layer structure through chemical treatment, which controls the roughening of the copper layer surface before inner layer bonding to enhance the bonding strength between the inner copper layer and the prepreg after lamination; the "lamination" refers to the process of bonding the circuit layers into a whole using the adhesive properties of PP sheets; the "drilling" refers to creating through-holes between the circuit board layers to connect them; the "electroplating," also known as "chemical copper plating," involves the board undergoing an oxidation-reduction reaction in an electroplating bath after drilling to form a copper layer, thereby metallizing the holes and depositing copper on the originally insulating substrate surface to achieve interlayer electrical connectivity; and the "plate plating" process thickens the copper on the board surface and inside the holes of the board immediately after electroplating to prevent the thin copper inside the holes from being oxidized or micro-corroded before pattern electroplating, thus preventing substrate leakage. The solder resist, also known as solder mask or green oil, is one of the most critical processes in printed circuit board (PCB) manufacturing. It involves screen printing or coating the PCB with solder resist ink to create a layer of solder resist. Through exposure and development, the pads and holes to be soldered are exposed, while other areas are covered with a solder resist layer to prevent short circuits during soldering. The PCB manufacturing process in this embodiment is as follows: First, the original copper-clad laminate is cut into PCBs that can be manufactured on a production line. Then, the inner layer circuit patterns are transferred to the PCB. A uniform, well-adhesive organic metal layer structure is produced through chemical treatment, resulting in controlled roughening of the copper layer surface before inner layer bonding. Using the adhesive properties of PP sheets, the circuit layers are bonded together to form a circuit board. Through-holes are drilled between the circuit board layers to connect them. After drilling, the circuit board undergoes an oxidation-reduction reaction in a copper plating bath to form a copper layer, thereby metallizing the holes and creating vias. This allows copper to be deposited on the originally insulating substrate surface, achieving electrical connectivity between layers. The process of plate plating thickens the copper layer on the newly plated circuit board, including the surface and inside the holes, to 5-8µm. This prevents the thin copper inside the holes from being oxidized and micro-corroded away before pattern plating, thus exposing the substrate. The outer layer circuit pattern is transferred to the circuit board, and the copper layers in the holes and circuits are plated to a thickness of 20-25µm to meet the final copper thickness requirements of the finished circuit board. Unused copper on the board surface is etched away to expose the useful circuit pattern. A layer of solder resist is applied to the board surface through screen printing or coating with solder mask ink. After exposure and development, the vias and the copper layer around them are exposed to form solder pads. Other areas are covered with solder resist to prevent short circuits during soldering, resulting in a circuit board with via openings. Three to four circuit boards with via openings can be stacked and formed into a board with solder pads using a coarse router along pre-routed grooves. It is worth noting that... Figure 6As shown, this embodiment, compared to the processing flow of a half-hole onboard board with modular pads, saves the steps of drilling, splitting each stamp hole by 30mm, using a rough milling cutter to form the groove (grooving and dividing adjacent waste areas of multi-panel boards, at which point the half-hole division is completed, with a conventional rough milling cutter speed of 0.4m / min to 0.8m / min), and using a fine milling cutter at low speed to grind and refine the half-hole in both directions to remove residual burrs from the via (generally, a fine milling cutter speed of 0.24m / min to 0.6m / min). This embodiment eliminates the need to cut the via into half-holes. Compared to the half-hole type pad milling method, which can only stack a maximum of two onboard boards, this embodiment can stack 3-4 boards together for milling, and only requires one milling operation, simplifying the onboard board manufacturing process, improving the production efficiency of the onboard board, and making the finished product less prone to damage.

[0038] In one implementation of this embodiment, after the onboard board is formed, although the surface of copper has good solderability, it is prone to moisture and oxidation when exposed to air for a long time, tending to exist in the form of oxides and unlikely to remain as original copper for a long time. Therefore, it is necessary to perform anti-oxidation treatment on the copper surface to ensure good solderability and electrical performance. The anti-oxidation treatment includes methods such as tin spraying, immersion gold, OSP, immersion tin, immersion silver, nickel-palladium-gold, electroplated hard gold, or electroplated gold fingers. In this embodiment, any anti-oxidation treatment method can be selected for treatment.

[0039] This embodiment also provides an onboard board, such as Figure 2 As shown in Figure 4, the onboard board is manufactured based on the onboard board manufacturing method. The onboard board module pads include a pin portion 12, and the pin portion 12 has a plurality of pin through holes 13. The copper layer of each pin through hole 13 is a window area 14. The window area 14 is located on the soldering surface 15 of the board body. The window area 14 can be a regular shape, such as a circle or a rectangle, or it can be an irregular shape. Each pin through hole 13 has a preset distance from the side 16 of the board body, so that the hole wall of the pin through hole 13 in the window area 14 will not be exposed to the side 16 of the board body. This allows the pin through holes 13 to be completed in one milling with a conventional process roughing cutter. The operation is simple, the finished product qualification rate is high, and there is no need for the cumbersome manufacturing steps of forming half holes. This greatly reduces the difficulty of board manufacturing and processing costs. When milling the pin through holes 13 in one milling with a conventional process roughing cutter, two or more boards can be stacked and milled at the same time, which greatly improves the production speed.

[0040] In one implementation of this embodiment, the welding surface of the board is a plane. Setting the welding surface of the board to a plane can, on the one hand, allow the onboard board to be placed stably on the table; on the other hand, it can allow the welding surface of the board to fit better with the external printed circuit board on the plane, so as to weld the onboard board and the external printed circuit board.

[0041] In one implementation of this embodiment, the window area 14 on each pin through-hole 13 extends to the side 16 of the board body. The board body uses the window area 14 as the contact area for soldering with the external printed circuit board. By increasing the area of ​​the window area 14 of the board body, the onboard board can make more contact with and adhere to the external printed circuit board, thereby improving the soldering stability between the window area of ​​the onboard board and the external printed circuit board.

[0042] In one implementation of this embodiment, the board body and the external printed circuit board are connected by reflow soldering. Solder paste is applied between the window area 14 of the board body and the external printed circuit board. The solder paste is located on both the window area 14 and the external printed circuit board. The solder paste contains flux, which can melt and wet the solder, allowing the solder to spread. When the solder paste is placed between the window area 14 and the external printed circuit board, the flux component in the solder paste is activated by contact heating, thereby promoting the wetting and diffusion of the solder paste. The flux turns into gas after being heated, evaporates, and solidifies upon cooling to form solder joints. Since the gas from the heated flux can be discharged from the window area 14 and the pin via 13, the solder between the board body and the external printed circuit board is less likely to contain gas, thus avoiding voids in the solder joints between the board body and the external printed circuit board, ensuring that the solder joints between the board body and the external printed circuit board are free of voids and poor soldering.

[0043] In one implementation of this embodiment, the pin via 13 is a circular via, and the depth of each pin via 13 is at least 0.8 mm. When the board body and the external printed circuit board are soldered with solder paste, the wall of the pin via 13 has a certain tinning capacity. This can prevent insufficient solder paste from causing soldering voids between the board body and the external printed circuit board, thus affecting the soldering stability of the board body and the external printed circuit board. On the other hand, it can prevent excessive solder paste from overflowing from the pin via 13 and affecting the normal use of the board. It also increases the freedom of solder paste application. In addition, since the pin via 13 is a circular via, it has a preset distance from the side of the board body. When the solder paste climbs into the pin via 13, it will not be exposed to the outside of the board body, and will not affect the simplicity and aesthetics of the overall structure of the board body.

[0044] In one implementation of this embodiment, each pin through-hole 13 is provided with a window hole wall 18 extending circumferentially. The window hole wall 18 is located on the hardware mounting surface 17 of the board body, which is the opposite side of the board body soldering surface 15. The window hole wall 18 can prevent green solder paste from entering into the pin through-hole 13, thereby affecting the venting effect of the pin through-hole 13 on the solder paste.

[0045] In one implementation of this embodiment, the area of ​​the window region 14 is larger than the area of ​​the window hole wall 18. The window region 14 is located on the periphery of the soldering surface 15 as a pin through hole 13, while the window hole wall 18 is located on the circumference of the hardware mounting surface 17 as a pin through hole 13. The window region 14 is mainly used for soldering with an external printed circuit board, while the window hole wall 18 is used for external wiring. Therefore, the area of ​​the window region 14 is larger than the area of ​​the window hole wall 18.

[0046] In one implementation of this embodiment, the window opening wall 18 is an annular wall, and the annular radius of the annular wall is not less than 0.1 mm.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of making a board-on-board, characterized by, The method comprises the following steps: The original copper-clad plate is cut, and the cut copper-clad plate is subjected to inner layer dry film, brown oxidation and lamination to form a circuit board; The circuit board is drilled, and the holes are metallized by copper plating to form vias, wherein the copper plating is used to thicken the copper on the surface of the plate and in the holes; The circuit pattern is made on the circuit board after the hole metallization, and the solder resist treatment is performed to obtain a circuit board with via opening, wherein the copper layer around the via and the via is exposed during the solder resist treatment to form a pad; The circuit board with via opening is cut to a predetermined size to form a board carrier plate; The step of cutting the circuit board with via opening to a predetermined size to form a board carrier plate comprises: Three to four circuit boards with via opening are stacked, and a rough milling cutter is used to mill along the pre-milling line to form a groove, wherein the adjacent scrap area of the multi-spliced plate is excavated and divided to complete the half-hole division; A fine milling cutter is used to polish the half-hole in two directions at a low speed to remove the residual burrs of the via to form a board carrier plate with a pad.

2. The method of claim 1, wherein After the step of cutting the circuit board with via opening to a predetermined size to form a board carrier plate, the method further comprises: The copper surface of the pad of the board carrier plate is subjected to anti-oxidation treatment.

3. An on-board board, characterized by, The board carrier plate module pad is made based on the board carrier plate manufacturing method of any one of claims 1-2, the board carrier plate comprises a plate body, the via is a pin through hole, the copper layer around the hole is an opening area, the opening area is located on the soldering surface of the plate body, and each pin through hole has a predetermined distance from the side edge of the plate body.

4. The backplane of claim 3, wherein, The opening area on each pin through hole extends to the side edge of the plate body.

5. The backplane of claim 3, wherein, The depth of the hole wall of each pin through hole is at least 0.8 mm.

6. The backplane of claim 3, wherein, A via hole wall is provided on the periphery of each pin through hole, and the via hole wall is located on the hardware mounting surface of the plate body.

7. The backplane of claim 6, wherein, The area of the opening area is greater than the area of the via hole wall.

8. The backplane of claim 6, wherein, The via hole wall is an annular hole wall, and the annular radius of the annular hole wall is not less than 0.1 mm.

9. The backplane of claim 3, wherein, The pin through hole is a circular through hole.

10. The backplane of claim 3, wherein, The soldering surface of the plate body is a plane.

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