Method for filling and plating metal in through hole of substrate
The method of electroplating a metal layer from the bottom up in through-holes addresses the challenge of filling high AR holes, ensuring complete coverage and preventing voids, thus improving electrical performance and reliability.
Patent Information
- Application Number
- CN202510674619.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-23
- Publication Date
- 2025-07-15
AI Technical Summary
The prior art is difficult to effectively fill through holes with high thickness-to-diameter ratios, resulting in insufficient metallization in the holes and prone to voids, affecting the electrical performance and reliability of the circuit board.
When the inner wall of the through hole is not metalized in advance, the metal hole is sealed at one end and connected to the electrode, and electroplating is performed to allow metal ions to obtain electrons at the bottom of the through hole, and gradually grow upward to form a good filling effect.
Effective metal filling with high thickness-diameter ratio through holes is achieved, preventing the hole from being blocked by electroplated metal and metal voids in the holes, and is suitable for metal filling requirements of various hole types.
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Figure CN120321882A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic circuit technologies, and particularly relates to a method for filling metal in through-holes of a substrate. Background Art
[0002] A circuit board, also known as a Printed Circuit Board (PCB), is a support for electronic components and also a carrier for their electrical connections. The design and manufacture of circuit boards are key links in the development process of electronic products, and their quality directly affects the performance and reliability of electronic devices.
[0003] During the preparation process of a circuit board, the preparation of circuit patterns and vias for realizing interlayer interconnection is a key process. For example, generally, for the production of filling copper in through-holes of printed circuit boards and packaging substrates, it is usually necessary to first metallize the hole walls, and then use the methods of conformal electroplating for "X"-shaped holes and bridging "H"-shaped holes and then filling blind holes.
[0004] As circuit patterns develop towards smaller sizes and higher precision, the number of layers of circuit boards is increasing, the aspect ratio (AR) of through-holes is increasing, and it is becoming more and more difficult to metallize the hole walls. When the AR exceeds 10:1, vacuum sputtering cannot reach the middle of the hole, and copper breaks or voids are likely to occur. On the other hand, voids are likely to occur during hole filling with metal, affecting the electrical performance and reliability of the substrate and unable to meet the filling requirements for through-holes with a high aspect ratio.
[0005] Therefore, how to complete the filling of through-holes, especially through-holes with a high aspect ratio, is one of the research focuses of those skilled in the art. Summary of the Invention
[0006] Based on this, this application provides a method for filling metal in through-holes of a substrate, including the following steps:
[0007] Provide a substrate having through-holes penetrating both its two side surfaces;
[0008] Form a metal layer at one side through-hole opening of the substrate, and the metal layer at least covers the through-holes to be filled;
[0009] The metal foil is in contact with at least one cathode and an electroplating solution, and electroplating is carried out until the metal in the hole grows to the substrate surface;
[0010] Ensure that the metal layer is fully exposed at the bottom of the through-hole;
[0011] The metal layer is in contact with at least one cathode and an electroplating solution, and electroplating is carried out until the metal in the hole grows to the substrate surface;
[0012] Compared with the traditional solution, this application has the following beneficial effects:
[0013] The technical solution of the present application can, without pre-metallizing the inner wall of the through hole, seal one end with metal and connect it to the electrode. After energization, metal ions obtain electrons at the bottom of the through hole, and the metal grows gradually upward from the bottom, forming a good filling effect. This method can effectively prevent the problem that the orifice is sealed by electroplated metal due to the presence of a conductive layer and the occurrence of voids in the metal solid column in the hole, can realize the metal filling process for through holes with an ultra-large aspect ratio, and is suitable for the metal filling requirements of various hole types. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application and more comprehensively understand the present application and its beneficial effects, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative efforts.
[0015] Figure 1 Schematic diagram of the preparation process for filling a substrate through hole with metal in one embodiment;
[0016] Figure 2 Schematic diagram of the structure for filling a substrate through hole with a metal layer being an adhesive metal foil;
[0017] Figure 3 Schematic diagram of the structure for filling a substrate through hole with a metal layer being a pure metal foil;
[0018] Figure 4 Schematic diagram of the structure for filling a substrate through hole with a metal layer being metal paste;
[0019] Figure 5 Schematic diagram of the structure for filling a substrate through hole with a metal layer being a metal plate;
[0020] Figure 6 Schematic diagram of the structure for removing the metal and metal layer on the substrate surface after completing the through hole filling. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0021] The following further elaborates on the present application in combination with specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosed content of the present application more thorough and comprehensive.
[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art belonging to the technical field of the present application. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.
[0023] TERMS
[0024] Unless otherwise specified or there are contradictions, the terms or phrases used in this application have the following meanings:
[0025] In this application, when it comes to "at least one", unless otherwise specifically defined, it means including "one or more" in terms of quantity;
[0026] In this application, when it comes to "a plurality of", "multiple types", "multiple times", "multiple elements", etc., unless otherwise specifically defined, it means greater than 2 or equal to 2 in terms of quantity. For example, "one or more" means one or greater than or equal to two.
[0027] In this application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.
[0028] In this application, when it comes to "optionally", "optional", "option", it means optional, that is, it refers to either of the two parallel options of "yes" or "no". If "optional" appears multiple times in a technical solution, unless otherwise specified and there are no contradictions or mutual restrictions, each "optional" is independent of each other.
[0029] In this application, when it comes to a numerical interval (that is, a numerical range), unless otherwise specified, the optional numerical values are considered continuous within the above numerical interval, and include the two numerical endpoints of the numerical range (that is, the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints.
[0030] The temperature parameter in this application, unless otherwise specifically defined, allows both constant temperature treatment and variation within a certain temperature range. It should be understood that the so-called constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. It is allowed to fluctuate within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C.
[0031] In this application, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.
[0032] In this application, when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. It should also be understood that when interpreting the connection relationship or positional relationship of elements, although not explicitly described, the connection relationship and positional relationship are interpreted to include an error range, and this error range should be within the acceptable deviation range of a specific value determined by those skilled in the art.
[0033] This application provides a method for filling metal in through-holes of a substrate. In one embodiment, please refer to Figure 1 , the method for preparing a circuit includes the following steps:
[0034] S10. Provide a substrate, and the substrate has through-holes penetrating its two side surfaces.
[0035] Among them, the through-holes can be designed according to actual needs, and the through-holes can be formed on the raw substrate by laser drilling or mechanical drilling. The purpose of opening the through-holes is to achieve interlayer conduction between multiple layers of circuits, and the through-holes covered with metal are also called "via holes".
[0036] Optionally, the substrate is an insulating substrate, and the material of the insulating substrate includes at least one of plastic, glass, ceramic or polymer.
[0037] Please refer to Figures 2 to 6 , in each embodiment, through-holes 111 are opened on the substrate 11. The substrate 11 is a dielectric layer, and the through-holes 111 can be formed by laser or mechanical drilling. In the embodiment, the substrate thickness is 500 μm and the hole diameter is 50 μm.
[0038] S20. Form a metal layer at the through-hole opening on one side of the substrate, and the metal layer covers at least the through-holes to be filled.
[0039] The metal layer can be selected from one of metal paste, pure metal foil or adhesive metal foil. In each embodiment, Figure 2 shows a process schematic diagram of the metal layer being an adhesive metal foil, Figure 3 shows a process schematic diagram of the metal layer being a pure metal foil, Figure 4 shows a process schematic diagram of the metal layer being metal paste, Figure 5 shows a process schematic diagram of the metal layer being a metal plate.
[0040] When the metal layer is an adhesive metal foil, it can be selected from one of adhesive copper foil, adhesive aluminum foil, and adhesive tin foil. For example, Figure 2As shown, an adhesive metal foil 21 is pressed and attached to one side of the substrate 11, and the copper foil 21 covers the lower end of the through hole on the substrate. The adhesive metal foil 21 includes an adhesive layer 211 and a metal foil 212. When the metal foil is an adhesive metal foil, before it contacts the cathode, the adhesive layer on the surface of the metal foil at the bottom of the through hole is removed to ensure that the metal surface of the metal foil is fully exposed at the bottom of the through hole.
[0041] When the metal layer is a pure metal foil, it can be selected from one of copper foil, aluminum foil, and tin foil, such as Figure 3 As shown, a colloidal layer 211' is first applied to one side of the substrate 11, and then a pure metal foil layer 212' is pressed and attached.
[0042] When the metal layer is a metal paste, it can be selected from one of solder paste, silver paste, or copper paste. The viscosity range of the solder paste is 10 - 200 Pa·s, the viscosity range of the silver paste is 10 - 100 Pa·s, and the viscosity range of the copper paste is 10 - 100 Pa·s. The metal paste can be covered on one side of the substrate by printing, and then cured by heating and sintering. The sintering temperature depends on the substrate material and the type of metal paste, and is not specifically limited here. It is only necessary to be able to cure the paste. Generally, the sintering and curing temperature of the solder paste is 100°C - 200°C, the sintering and curing temperature of the silver paste is 100°C - 300°C, and the sintering and curing temperature of the copper paste is 100°C - 650°C.
[0043] When the metal layer is a metal paste, it can be selected from one or more of solder paste, copper paste, or silver paste, such as Figure 4 As shown, the metal paste 211'' is printed on the whole plate on one side of the substrate first, and then sintered to make the paste completely cover the orifice of the through hole.
[0044] When the metal layer is a metal plate, it can be selected from one of copper plate, aluminum plate, and tin plate, such as Figure 5 As shown, a fixture is used to bond the substrate 11 and the metal plate 212'' together, and the metal plate covers the orifice of the through hole.
[0045] When the metal layer is a pure metal foil or an adhesive metal foil, the method of pressing and attaching it to the substrate can be selected from one of a hot roller at 50 - 80°C or manual pressing. The total thickness range of the pure metal foil or the adhesive metal foil can be 5 - 150 μm, more preferably 15 - 55 μm. For example, the total thickness is 5 μm, 15 μm, 35 μm, 55 μm, 75 μm, 95 μm, 115 μm, 135 μm, 150 μm. The function of the adhesive layer 211 is insulation, and its thickness is usually relatively thin and can be ignored relative to the copper foil as long as it can provide insulation and has no impact on subsequent processes. The function of the copper foil is to conduct electricity, enabling the metal in the through hole to continuously deposit and grow towards the other end of the through hole 111 during the electroplating process.
[0046] S30. Ensure that the metal surface of the metal layer is fully exposed at the bottom of the through-hole.
[0047] If the metal layer is metal paste, pure metal foil or metal plate, after covering the through-hole, the metal layer does not need to be processed, and the metal surface is naturally fully exposed at the bottom of the through-hole. If the metal layer is adhesive metal foil, the adhesive layer at the bottom of the through-hole needs to be removed from the adhesive metal foil. Please refer to Figure 2 , after removing the adhesive layer of the metal foil at the bottom of the through-hole, the metal surface is exposed at the bottom of the through-hole of the through-hole and serves as the conductive layer in the subsequent steps. When electroplating, metal grows and deposits in the through-hole. In this step, the method for removing the adhesive layer can be laser ablation or chemical method. In the laser ablation method, the intensity of the laser is 1-4 kw / cm 2 , the energy is 20-50%, and the frequency range is 15-25 Hz. The chemical method generally removes the glue through chemical solution, which can refer to the conventional methods in the art, and this application does not make special restrictions.
[0048] S40. The metal layer is in contact with at least one cathode and electroplating solution for electroplating until the metal in the hole grows to the substrate surface.
[0049] In this step, the metal layer at the bottom of the through-hole in the substrate is in contact with one cathode. The anode can be an insoluble anode. The electroplating equipment is generally an electroplating tank. The main metal salt in the electroplating solution can be at least one of copper, cobalt, gold, silver, tin or their mixture. Correspondingly, the metal deposited in the through-hole is at least one of copper, cobalt, gold, silver, tin or their alloy. The electroplating solution formula for each metal can refer to the conventional electroplating solutions publicly used in the art, and this application does not make special restrictions. The current density range of the electroplating step is 0.1-50 ASD, and more preferably 0.5-10 ASD. Electroplate until the metal in the hole grows to the substrate surface, and finally obtain the metal column 41.
[0050] Optionally, after obtaining the completion of the through-hole metallization filling, the metal and metal layer on the substrate surface can be removed by mechanical polishing or chemical etching methods to make the metal in the through-hole flush with the substrate surface. As Figure 6 shown, this figure shows that the metal layer is adhesive metal foil, and there is also a step S50 after S40, that is, removing the metal and metal layer on the substrate surface to make the metal in the through-hole flush with the substrate surface.
[0051] The methods for removing the metal and metal layer on the substrate surface in this step include that chemical etching is generally carried out through chemical solution, which can refer to the conventional methods in the art, and this application does not make special restrictions.
[0052] Optionally, if both sides of the metal layer of the present invention are pressed against the substrate and the above steps S10 to S40 are repeated, through-hole filling plating can be achieved on both sides, and the efficiency is increased.
[0053] Another object of the present invention is to provide a method for manufacturing a circuit, characterized in that the method is carried out on the via metallized substrate obtained above.
[0054] The above method can be applied to the fabrication of conductive lines and interlayer vias in electronic circuits, packaging substrates, integrated circuit packages, etc.
[0055] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.
[0056] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.
Claims
1. A method for filling a through-hole of a substrate with metal, characterized in that, Comprising the following steps: Providing a substrate having through holes penetrating both of its opposite surfaces; Forming a metal layer at the orifice of the through hole on one side of the substrate, the metal layer covering at least the through holes to be filled; Ensuring that the metal surface of the metal layer is sufficiently exposed at the bottom of the through hole; Contacting the metal layer with at least one cathode and an electroplating solution to perform electroplating until the metal in the holes grows up to the surface of the substrate.
2. The method for plating a metal in a substrate through hole according to claim 1, wherein The substrate is an insulating substrate, and the material of the insulating substrate includes at least one of plastic, glass, ceramic or polymer.
3. The method for filling a metal in a through-hole of a substrate according to claim 1, characterized in that The metal layer is selected from one of metal paste, pure metal foil, adhesive metal foil or metal plate, The metal paste is selected from one or more of solder paste, silver paste or copper paste; or The pure metal foil is selected from one of copper foil, aluminum foil, tin foil; or The adhesive metal foil is selected from one of adhesive copper foil, adhesive aluminum foil, adhesive tin foil; or The metal plate is selected from one of copper plate, aluminum plate or tin plate.
4. The method for filling a metal in a substrate through-hole according to claim 1, wherein, The thickness range of the metal layer is 5 - 150 μm.
5. The method for filling a metal in a through-hole of a substrate according to claim 3, wherein The viscosity range of the solder paste is 10 - 200 Pa·s, the viscosity range of the silver paste is 10 - 100 Pa·s, and the viscosity range of the copper paste is 10 - 100 Pa·s.
6. The method for filling a metal in a substrate through-hole according to claim 1, wherein The metal in the holes includes at least one of copper, cobalt, gold, silver, tin.
7. The method for filling a metal in a through hole of a substrate according to claim 1, wherein The current density range of the electroplating operation is 0.1 - 50 ASD.
8. A method for preparing a circuit, characterized in that, The method is carried out on the substrate obtained according to any one of claims 1 - 7.