Metal plated hole laminated structure for circuit board and manufacturing method thereof

Abstract

The invention discloses a metal plated hole laminated structure for a circuit board and a manufacturing method thereof. The metal plated hole laminated structure comprises a substrate, an upper surface metal layer, an in-hole metal layer and an insulating component, through holes are formed in the substrate, and each through hole is provided with an inner wall and a first hole edge adjacent to the upper surface. The upper surface metal layer is arranged on the upper surface of the substrate. The in-hole metal layer is arranged on the surface of the inner wall to form at least one filling hole corresponding to the at least one through hole, and the upper surface metal layer and the in-hole metal layer are connected at the first hole edge and form a fillet curved surface. The insulating component is filled in the at least one filling hole. Therefore, according to the metal plating hole stacking structure provided by the invention, the overflowing hole plugging agent can be removed by applying a laser process, the thickness of the metal layer on the surface of the substrate is improved, and meanwhile, the process is simplified.

Description

Technical Field

[0001] The invention relates to a circuit board structure, in particular to a metal plated hole stacking structure for a circuit board. Background Art

[0002] In existing PCB manufacturing, the thickness of the interlayer copper is increased beforehand to prevent the subsequent removal of the plugging agent with chemical solvents. This also results in a thinner copper layer. This thinned interlayer copper is susceptible to cracks at the edges of the through-holes due to external stress, and the thinned copper also has a higher resistance. Both of these issues can affect the electrical performance of the PCB.

[0003] Therefore, how to simplify the circuit board manufacturing process by improving the structural design and overcoming the above-mentioned defects has become one of the important issues that the above-mentioned business aims to solve. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a metal plated hole stacking structure for circuit boards and a manufacturing method thereof in response to the shortcomings of the existing technology. A laser process can be used to remove overflowed plugging agent and increase the thickness of the metal layer on the surface of the substrate, while simplifying the process.

[0005] In order to solve the above-mentioned technical problems, one of the technical solutions adopted by the present invention is to provide a metal-plated hole stacking structure for a circuit board, which includes a substrate, an upper surface metal layer, an inner hole metal layer and an insulating component. The substrate has an upper surface and a lower surface, and at least one through hole is provided in the substrate, each having an inner wall and a first hole edge adjacent to the upper surface. The upper surface metal layer is provided on the upper surface of the substrate. The inner hole metal layer is provided on the surface of the inner wall to form at least one filling hole corresponding to at least one of the through holes, and the upper surface metal layer and the inner hole metal layer are connected at the first hole edge to form a rounded curved surface. And an insulating component is filled in at least one of the filling holes. The inner hole metal layer has a first thickness, the upper surface metal layer has a second thickness, and the difference between the first thickness and the second thickness can be in the range of 0 microns to 5 microns.

[0006] Furthermore, the upper surface metal layer includes a first metal layer and a second metal layer, the first metal layer is arranged on the upper surface, the second metal layer is arranged on the first metal layer, and the second metal layer and the in-hole metal layer together form a continuous metal layer.

[0007] Furthermore, the metal-plated hole stacking structure also includes a lower surface metal layer, which is arranged on the lower surface of the substrate, and at least one of the through holes also has a second hole edge adjacent to the lower surface. The lower surface metal layer and the metal layer in the hole are connected at the second hole edge to form another rounded curved surface.

[0008] Furthermore, the lower surface metal layer includes a third metal layer and a fourth metal layer, the third metal layer is arranged on the lower surface, the fourth metal layer is arranged on the third metal layer, and the second metal layer, the in-hole metal layer and the fourth metal layer together form the continuous metal layer.

[0009] Furthermore, the substrate is an insulating material, which can be selected from glass fiber, paper phenolic or plastic material.

[0010] Furthermore, the upper surface metal layer can be selected from one or more of copper, tin, gold, silver, lead-tin alloy, titanium-copper, titanium alloy and tin-copper alloy.

[0011] Furthermore, the lower surface metal layer can be selected from one or more of copper, tin, gold, silver, lead-tin alloy, titanium-copper, titanium alloy and tin-copper alloy.

[0012] Furthermore, the average surface roughness of the upper metal layer is in the range of 0.5 micrometer to 1.0 micrometer.

[0013] Furthermore, the insulating component is made of resin.

[0014] In order to solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide a method for manufacturing a metal-plated hole stacked structure for a circuit board, which includes: forming an upper surface metal layer on the upper surface of a substrate. Forming one or more through holes in the substrate, each of the one or more through holes having an inner wall and a first hole edge. Forming an in-hole metal layer on the surface of the inner wall of each through hole to form a filled hole corresponding to each through hole, the filled hole having a second hole edge. Filling the filled hole with insulating material and then baking it; and removing the insulating material that overflows the second hole edge by emitting a laser beam using a laser device.

[0015] Furthermore, the upper surface metal layer includes a first metal layer and a second metal layer. After the first metal layer is formed on the upper surface, the second metal layer is formed on the first metal layer, and the second metal layer and the in-hole metal layer together form a continuous metal layer.

[0016] Furthermore, the manufacturing method further includes forming a lower surface metal layer on a lower surface of the substrate.

[0017] Furthermore, the lower surface metal layer includes a third metal layer and a fourth metal layer. After the third metal layer is arranged on the lower surface, the fourth metal layer is arranged on the third metal layer, and the third metal layer, the in-hole metal layer and the fourth metal layer together form a continuous metal layer.

[0018] Furthermore, after the continuous metal layer is formed, the surface of the continuous metal layer is treated by chemical agents or physical and mechanical methods.

[0019] Furthermore, the insulating material is resin.

[0020] Furthermore, when the laser device emits the laser light to etch the overflowed insulating material, the etching endpoint can be detected by human eyes or a detection device.

[0021] Furthermore, when the detection device detects or the human eye perceives the light source reflected by the upper surface metal layer, the laser light is stopped.

[0022] Furthermore, the wavelength of the laser light emitted by the laser device may be greater than 1000 nanometers.

[0023] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic cross-sectional view of a metal plated hole stacking structure according to an embodiment of the present invention.

[0025] Figure 2 4 is a flowchart of the process steps of an embodiment of the present invention.

[0026] Figures 3A-3E Schematic cross-sectional view of each process step of an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following is an explanation of the implementation methods of the "metal-plated hole stacking structure and its manufacturing method" disclosed in the present invention through specific specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following embodiments will further explain the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention. In addition, the term "or" used in this article may include any one or more combinations of the associated listed items depending on the actual situation.

[0028] Figure 1 FIG1 is a cross-sectional view of a metal plated hole stacked structure 1 according to a first embodiment of the present invention. Figure 1 The embodiment of the present invention provides a metal plated hole stacking structure 1 for a circuit board, which includes: a substrate 10, an upper surface metal layer 20, a hole metal layer 30, an insulating component 40, and a lower surface metal layer 50. In this embodiment, the substrate 10 is formed by laminating multiple circuit layers to form a circuit board, for example, by printing, electroplating or yellow light processing methods, electronic circuits (such as contacts, interconnection circuits, graphics, etc.) are arranged on opposite sides of a single circuit carrier to form a pair of electronic layers. Figure 1 As shown, the substrate 10 has a dielectric layer, multiple conductive layers arranged on the upper and lower sides of the dielectric layer, and multiple conductive layer interconnection through-holes, which electrically connect the metal layers on the upper and lower sides of the dielectric layer through the conductive layer interconnection through-holes. The dielectric layer in the embodiment can be, for example, epoxy resin, fiberglass, or paper phenolic. The conductive layer interconnection through-holes in the substrate 10 can be a laminated structure passing through all the conductive layers and the dielectric layers, or a laminated structure passing through part of the conductive layers and the dielectric layers, or a plurality of conductive layer interconnection through-holes can be staggered with each other in the substrate 10.

[0029] In the embodiment of the present invention, the stacking relationship of the various components is as follows: the upper surface metal layer 20 is located on the upper surface 120 of the substrate 10, and the lower surface metal layer 50 is located on the lower surface 130 of the substrate 10. The substrate 10 has multiple through-holes 110, each of which has an inner wall 111 and first hole edges 112 located on the upper and lower sides of the through-hole 110. The in-hole metal layer 30 is located on the inner wall 111 and forms a filling hole 310 corresponding to the through-hole 110. In this embodiment, the material of the upper surface metal layer, the lower surface metal layer, and the in-hole metal layer is copper. An insulating component 40 is located in the filling hole 310.

[0030] In addition, the upper surface metal layer 20 also includes a first metal layer 210 and a second metal layer 220. The first metal layer 210 is located on the upper surface 120 of the substrate 10. The second metal layer 220 is formed on the first metal layer 210, and the second metal layer 220 and the in-hole metal layer 30 form a continuous metal layer. Similarly, on the lower surface 130 side of the substrate 10, the lower surface metal layer 50 also includes a third metal layer 510 and a fourth metal layer 520. The third metal layer 510 is located on the lower surface 130 of the substrate 10, and the fourth metal layer 520 is located on the third metal layer 510. The second metal layer 220, the in-hole metal layer 30, and the fourth metal layer 520 together form a continuous metal layer.

[0031] like Figure 1 As shown, in the embodiment of the present invention, the insulating component 40 is made of resin. Laser removal of the resin that overflows the hole edges is used to create rounded curved surfaces 320 at both the first hole edge 112 and the second hole edge 113 of the continuous metal layer. Specifically, during the copper plating process to coat the through-hole 110, the first metal layer 210, and the third metal layer 510, the interlayer copper and the hole copper in the printed circuit board are simultaneously formed. Because the thickness of the interlayer copper and the hole copper determines the electrical properties of the product, and the product must meet international acceptance standards for printed circuit boards (PCBs), the thickness of the interlayer copper and the hole copper is greater than that of the bottom copper and the surface copper, meaning that the continuous metal layer is thicker. As described above, due to the greater thickness of the continuous metal layer, when copper is electroplated on the first hole edge 112 and the second hole edge 113 of the through-hole 110, rounded curved surfaces 320 are formed at the turning points. In other words, from a cross-sectional perspective, the copper layer extends from the vertical plane of the through-hole 110 to the horizontal plane of the substrate 10, with the nearly 90-degree turn forming an arc shape. From a top view of the substrate 10 surface, the third hole edge 330 of the filled hole 310 has a progressive aperture radius, gradually increasing as the vertical plane extends to the horizontal plane.

[0032] In current PCB manufacturing processes, the method for removing the plugging resin from the inner wall 111 of the through-hole 110 and the first metal layer 210 is typically to repeatedly thin the surface copper with a chemical solvent, followed by physical abrasion. Chemical solvents such as permanganate solvents are used. Physical abrasion methods, such as rough grinding the substrate surface with a ceramic or abrasive belt, or fine grinding the rough-ground substrate surface with a non-woven fabric, remove any residual resin from the surface.

[0033] However, current methods for removing plugging resin mostly rely on chemical solutions and physical abrasion, both of which thin the interlayer copper on the substrate surface. The interlayer copper on the substrate is relatively thin, and the thickness of the interlayer copper decreases during the plugging resin removal process, resulting in a right angle in the cross-section at the junction of the interlayer copper and the hole copper. The right angles in the thinned metal layer are susceptible to external stress and cracks, causing the circuit board's circuits to short-circuit and increase their resistance, making it impossible to achieve the desired voltage. To avoid the copper loss caused by the plugging resin removal process, current circuit board processes reserve redundant thickness during copper plating to compensate for the copper loss in this process.

[0034] To address the aforementioned issues, this embodiment uses a laser to remove the insulating material covering substrate 10. In this embodiment, the insulating material may be, for example, resin, and the metal layer may be, for example, copper. Because resin and copper are dissimilar materials, the brightness of the reflected light produced when irradiated by laser light differs significantly. That is, when the detection equipment detects or the human eye perceives the laser light reflected by the copper, it indicates that the resin that has overflowed the filling hole and covered the metal layer has been removed, and the laser can be terminated at this point. Therefore, in this embodiment, the thickness of the upper surface metal layer 20 is not significantly reduced. Specifically, the metal layer 30 within the hole has a first thickness TH1, and the upper surface metal layer 20 has a second thickness TH2. The metal layer 30 within the hole and the second metal layer 220 within the upper surface metal layer 20 are continuous metal layers. Therefore, in this embodiment, the difference between the second thickness TH2 and the first thickness TH1 is approximately equal to the thickness of the first metal layer 210 within the upper surface metal layer 20. In alternative embodiments, the difference between the second thickness TH2 and the first thickness TH1 can be within a range of 0 microns to 5 microns.

[0035] Figure 2 4 is a flowchart of the process steps of an embodiment of the present invention. Figures 3A-3E Schematic cross-sectional view of each process step of an embodiment of the present invention. Figure 2 、 Figures 3A to 3E The embodiment of the present invention provides a method for manufacturing a metal plated hole stacked structure 1, which comprises at least the following steps:

[0036] Metal layers are formed on the upper and lower sides of the substrate 10. More precisely, the first metal layer 210 of the upper surface metal layer 20 is formed on the upper surface 120 of the substrate 10, and the third metal layer 510 of the lower surface metal layer 50 is formed on the lower surface 130 of the substrate 10. In this step, all the metal layers mentioned can be made of conductive metal materials, such as copper, and can be formed, for example, using chemical electroplating. However, the above is only an example, and the present invention does not particularly limit the type of conductive metal material and the method used to form the metal layers. The cross-sectional view of the circuit board of this process is shown as follows: Figure 3AAs shown, the first metal layer 210 and the third metal layer 510 are respectively plated on the upper and lower sides of the substrate 10. Specifically, in this step, copper is plated on the upper surface 120 and the lower surface 130 of the substrate 10 having the closed inner layer circuit by chemical electroplating.

[0037] Next, a plurality of through holes 110 are formed in the substrate 10 on which the metal layers (eg, the first metal layer 210 and the third metal layer 510) have been formed. The cross-sectional view of the circuit board in this process is shown in FIG. Figure 3B As shown, each through hole 110 has an inner wall 111, a first hole edge 112 and a second hole edge 113, and each through hole 110 passes through the substrate 10. Specifically, in this step, a through hole can be drilled in the substrate 10 by mechanical drilling or laser drilling, for example.

[0038] Next, another metal layer is formed on the upper and lower sides of the substrate 10 and in the through hole 110. The metal layer formed in this step can be used to make the metal layers on the upper and lower sides of the substrate 10 conductive. In other words, the inner metal layer 30 is formed on the surface of the inner wall 111 of each through hole 110 to form a filling hole 310 corresponding to the through hole 110. The upper and lower ends of the filling hole 310 have a third hole edge 330. The cross-sectional view of the circuit board of this process is shown as follows: Figure 3C As shown, the metal layer 30 in the hole, the second metal layer 220 of the upper surface metal layer 20, and the fourth metal layer 520 of the lower surface metal layer 50 are continuous metal layers, which are formed simultaneously on the inner wall 111, the first metal layer 210, and the third metal layer 510. In this embodiment, the first metal layer 210, the third metal layer 510, and the continuous metal layer are all copper. Specifically, this step uses chemical electroplating to plate a layer of copper on the inner wall 111 of the through hole 110. The inner wall 111 includes the conductive layer of the inner layer circuit of the substrate 10 and non-conductive resin or glass fiber. The metallized inner wall 111 can connect the inner layer circuit and the outer layer circuit of the substrate 10, so the through hole 110 is also called a conductive hole.

[0039] Next, the filling hole 310 in the substrate 10 is plugged. In this step, a filling material such as an insulating material can be filled into the filling hole 310 and then baked. The insulating material can be, for example, a resin. The cross-sectional view of the circuit board in this process is shown in FIG. Figure 3D As shown, the resin filling the filling holes 310 will overflow the third hole edges 330 at the upper and lower ends. If the number of filling holes 310 in the substrate 10 is large and the density is high, the entire surface of the substrate 10 will be covered with resin. To prevent the excess filling material from affecting subsequent products or processes, it needs to be removed.

[0040] Next, the excess hole filling material is removed. In this step, the hole filling material overflowing the third hole edge 330 can be removed by, for example, emitting a laser beam through a laser device. The cross-sectional view of the circuit board in this process is shown in FIG. Figure 3EAs shown, when using a laser device, for example, a fiber laser with a wavelength greater than 1000 nanometers can be used to remove resin that has overflowed the third hole edge 330. Because the brightness of the reflected light produced by resin and copper when irradiated by laser light is significantly different, when a detection device detects or the human eye perceives the light reflected by the copper, it indicates that the resin that has overflowed the filling hole 310 or covered the copper has been removed. At this point, the laser device can be stopped or the laser beam can be moved to the next target location to continue the hole filling material removal process.

[0041] At this point, the substrate 10 is formed after the excess via plugging has been removed using the process of the present invention. Because the laser process only removes the resin, the copper thickness remains unchanged. A cross-section of the substrate 10 reveals that the connection between the top metal layer 20 and the via metal layer 30 at the first via edge 112 forms a rounded curved surface 320. Similarly, the connection between the bottom metal layer 50 and the via metal layer 30 at the second via edge 113 also forms a rounded curved surface 320.

[0042] Next, a protective layer is formed on the substrate 10 after removing the excess hole-filling material. This completes the circuit layout, and a solder mask is formed on the substrate 10. The solder mask can be made of green paint (solder mask). The substrate 10 is then processed and cut to the desired shape, completing the printed circuit board (PCB) produced using the present invention.

[0043] In embodiments of the present invention, since the metal layer is not mechanically damaged, the finished product can have a metal layer with lower surface roughness. Such a metal layer provides better stability for signal transmission. Optionally, in embodiments of the present invention, the average surface roughness of the metal layer on the substrate surface is in the range of 0.5 microns to 1.0 microns.

[0044] For example, in the embodiment of the present invention, the material of the upper surface metal layer 120, the lower surface metal layer 130, and the hole metal layer 30 can be selected from copper, tin, gold, silver, lead-tin alloy, titanium-copper, titanium alloy, tin-copper alloy, or a combination thereof. However, the above example is only one possible embodiment and is not intended to limit the present invention.

[0045] One of the benefits of the present invention is that the metal-plated via stacked structure and its manufacturing method utilize laser resin removal, replacing the existing four-stage process of alternating chemical thin copper deposition and ceramic or grinding wheel brushing. Furthermore, because the present invention eliminates copper loss and the need for redundant copper thickness, manufacturing costs can be reduced.

[0046] Furthermore, the metal-plated hole stacked structure and its manufacturing method provided by the present invention not only shortens the overall process to reduce PCB production time, but also reduces PCB manufacturing costs by replacing chemical copper thinning with lasers. Furthermore, due to its optimized electrical properties, the present invention is applicable not only to bismaleimide triacine (BT) substrates but also to high-end ABF (Ajinomoto Build-up Film) substrates.

[0047] The contents disclosed above are only preferred feasible embodiments of the present invention and do not limit the scope of protection of the claims of the present invention. Therefore, all equivalent technical changes made using the contents of the description and drawings of the present invention are included in the scope of protection of the claims of the present invention.

Claims

1. A metal plated hole stacking structure for a circuit board, characterized in that: The metal plated hole stacked structure for a circuit board comprises: A substrate having an upper surface and a lower surface, wherein the substrate is provided with at least one through hole, each through hole having an inner wall and a first hole edge adjacent to the upper surface; an upper surface metal layer, disposed on the upper surface of the substrate; an in-hole metal layer, disposed on the surface of the inner wall to form at least one filled hole corresponding to at least one of the through holes, wherein the upper surface metal layer and the in-hole metal layer are connected at the first hole edge to form a rounded curved surface; and an insulating component filled in at least one of the filling holes; The metal layer in the hole has a first thickness, the metal layer on the upper surface has a second thickness, and the difference between the first thickness and the second thickness is in the range of 0 micrometers to 5 micrometers.

2. The metal plated hole stacked structure for a circuit board according to claim 1, characterized in that: The upper surface metal layer includes a first metal layer and a second metal layer. The first metal layer is arranged on the upper surface, the second metal layer is arranged on the first metal layer, and the second metal layer and the in-hole metal layer together form a continuous metal layer.

3. The metal plated hole stacked structure for a circuit board according to claim 2, characterized in that: The metal plated hole stacked structure for a circuit board further includes: a lower surface metal layer, disposed on the lower surface of the substrate; At least one of the through holes further has a second hole edge adjacent to the lower surface, and the lower surface metal layer and the metal layer in the hole are connected at the second hole edge to form another rounded curved surface.

4. The metal plated hole stacked structure for a circuit board according to claim 3, characterized in that: The lower surface metal layer includes a third metal layer and a fourth metal layer, the third metal layer is arranged on the lower surface, the fourth metal layer is arranged on the third metal layer, and the second metal layer, the in-hole metal layer and the fourth metal layer together form the continuous metal layer.

5. The metal plated hole stacked structure for a circuit board according to claim 1, characterized in that: The substrate is an insulating material selected from glass fiber, paper phenolic or plastic material.

6. The metal plated hole stacked structure for a circuit board according to claim 1, characterized in that: The upper surface metal layer is selected from one or more of copper, tin, gold, silver, lead-tin alloy, titanium-copper, titanium alloy and tin-copper alloy.

7. The metal plated hole stacked structure for a circuit board according to claim 3, characterized in that: The lower surface metal layer is selected from one or more of copper, tin, gold, silver, lead-tin alloy, titanium-copper, titanium alloy and tin-copper alloy.

8. The metal plated hole stacked structure for a circuit board according to claim 1, characterized in that: The average surface roughness of the upper metal layer is in the range of 0.5 micrometer to 1.0 micrometer.

9. The metal plated hole stacked structure for a circuit board according to claim 1, characterized in that: The insulating component is made of resin.

10. A method for manufacturing a metal plated hole stacked structure for a circuit board, characterized in that: The manufacturing method of the metal plated hole stacking structure for a circuit board comprises: forming a top metal layer on an upper surface of a substrate; forming at least one through hole in the substrate, wherein each of the at least one through hole has an inner wall and a first hole edge; forming an in-hole metal layer on the surface of the inner wall of at least one of the through holes to form a filling hole corresponding to the at least one through hole, wherein the filling hole has a third hole edge; Filling an insulating material into the filling hole and then baking the filling material; and A laser device is used to emit a laser beam to remove the insulating material overflowing from the edge of the third hole.

11. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 10, wherein: The upper surface metal layer includes a first metal layer and a second metal layer. After the first metal layer is formed on the upper surface, the second metal layer is formed on the first metal layer, and the second metal layer and the in-hole metal layer together form a continuous metal layer.

12. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 11, wherein: The manufacturing method further includes: forming a lower surface metal layer on a lower surface of the substrate.

13. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 12, wherein: The lower surface metal layer includes a third metal layer and a fourth metal layer. After the third metal layer is arranged on the lower surface, the fourth metal layer is arranged on the third metal layer, and the third metal layer, the in-hole metal layer and the fourth metal layer together form a continuous metal layer.

14. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 13, wherein: After the continuous metal layer is formed, the surface of the continuous metal layer is treated by chemical agents or physical and mechanical methods.

15. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 10, wherein: The insulating material is resin.

16. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 10, wherein: When the laser device emits the laser light to etch the overflowed insulating material, the etching end point is detected by human eyes or a detection device.

17. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 16, wherein: When the detection device detects or the human eye perceives the light source reflected by the upper surface metal layer, the laser light is stopped.

18. The method for manufacturing a metal plated hole stacked structure for a circuit board according to claim 10, wherein: The wavelength range of the laser light emitted by the laser device is greater than 1000 nanometers.

Images