Glass substrate with built-in inductor, packaging structure and preparation method of packaging structure

Abstract

The invention relates to the technical field of semiconductor packaging, in particular to a glass substrate with a built-in inductor, a packaging structure and a preparation method of the packaging structure. The glass substrate with the built-in inductor comprises the glass core layer and the inductor arranged in the glass core layer, three-dimensional integration of the inductor in the vertical direction is achieved, the thickness of a packaged product is greatly reduced, meanwhile, a spiral conductor structure in the inductor is wrapped, fixed and protected by the glass core layer, and the packaging quality is improved. The mechanical shock resistance, the vibration resistance and the bending resistance of the glass substrate are far better than those of a packaging process of a surface-mounted substrate surface, and the strength of the glass substrate with the built-in inductor is improved. Furthermore, a plurality of layers of glass substrates with built-in inductors are bonded to obtain a multi-turn inductor, and under the constraint of miniaturization, a high inductance value is realized, so that the utilization efficiency of the packaging structure on a magnetic field is higher, and the energy transfer or energy storage capability is stronger. And the glass substrate with the built-in inductor only needs to be produced on a traditional glass substrate, so that the risk, time and cost of process development are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and in particular to a glass substrate with an integrated inductor, a packaging structure, and a method for its fabrication. Background Technology

[0002] In recent years, with the continuous evolution of technologies such as higher computing power, higher bandwidth transmission, and higher integration modules, the demand for thinner semiconductor packaging technology has become increasingly stringent. Many passive components integrated in semiconductor packaging, such as inductors, capacitors, and resistors, occupy more than 60% of the PCB area. Currently, inductors are mounted on the substrate surface using surface mounting methods, resulting in a relatively thick package structure, which restricts the improvement of system integration. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a glass substrate with a built-in inductor, a packaging structure, and a method for preparing the same.

[0004] This application provides a glass substrate with a built-in inductor, comprising:

[0005] Glass core layer, inductor and conductive pillars; The glass core layer has a spiral through-hole and a conductive through-hole penetrating the glass core layer; The inductor includes a spiral conductor structure; the spiral conductor structure is located inside the spiral through-hole, and one end face of the spiral conductor structure is located on the first surface of the glass core layer, and the other end face of the spiral conductor structure is located on the second surface of the glass core layer, wherein the first surface and the second surface of the glass core layer are disposed opposite to each other. The conductive post is located inside the conductive through hole.

[0006] Optionally, the spiral conductor structure has several turns.

[0007] Optionally, the spiral conductor structure has fewer than one turn.

[0008] Optionally, the cross-sectional area of ​​the spiral through-hole gradually converges from the first surface of the glass core layer and then gradually increases to the second surface of the glass core layer. Correspondingly, the cross-sectional area of ​​the spiral conductor structure gradually converges from one end face of the spiral conductor structure and then gradually increases to the other end face of the spiral conductor structure.

[0009] Optionally, the inductor further includes a first electrode and a second electrode, wherein the first electrode is located at one end face of the helical conductor structure and the second electrode is located at the other end face of the helical conductor structure.

[0010] Optionally, one end face of the spiral conductor structure serves as the first electrode of the inductor, and the other end face of the spiral conductor structure serves as the second electrode of the inductor; or one end face of the spiral conductor structure is provided with a first cap-shaped conductor layer, and the other end face of the spiral conductor structure is provided with a second cap-shaped conductor layer, wherein the first cap-shaped conductor layer serves as the first electrode of the inductor, and the second cap-shaped conductor layer serves as the second electrode of the inductor.

[0011] Optionally, the spiral conductor structure includes a conductive layer and a filling layer; the conductive layer and the filling layer are sequentially stacked on the inner wall of the spiral through-hole.

[0012] Optionally, the filling layer is a metal filling layer or a non-metal filling layer.

[0013] Optionally, the glass substrate with the built-in inductor also includes an iron core located in the central region of the inductor, the iron core being electrically connected to or electrically isolated from the helical conductor structure.

[0014] Optionally, the first surface of the glass core layer has a first redistribution layer, and the second surface of the glass core layer has a second redistribution layer.

[0015] Optionally, the glass core layer includes one of a borosilicate glass core layer, an aluminosilicate glass core layer, or an alkali-free aluminoborosilicate glass core layer.

[0016] The present invention also provides a glass substrate with an embedded inductor, comprising multiple glass substrates with the above-mentioned embedded inductors, wherein two adjacent glass substrates are bonded together, wherein the second surface of one glass core layer in the two adjacent glass substrates is disposed opposite to the first surface of the other glass core layer, the inductors in the multilayer glass substrates are correspondingly disposed and electrically connected to form a multi-turn inductor, and the conductive pillars in the multilayer glass substrates are correspondingly disposed and electrically connected.

[0017] Optionally, the first surface of the first glass core layer has a first redistribution layer, and the second surface of the last glass core layer has a second redistribution layer.

[0018] The present invention also provides a packaging structure, including a glass substrate with a built-in inductor as described above and a chip packaged on the surface of the glass substrate, wherein the chip is electrically connected to the inductor.

[0019] The present invention also provides a method for preparing a glass substrate with a built-in inductor, comprising: A glass core layer is provided, the glass core layer having a spiral through-hole and a conductive through-hole extending through the glass core layer; A helical conductor structure is formed within the helical through-hole, with one end face of the helical conductor structure disposed on the first surface of the glass core layer and the other end face of the helical conductor structure disposed on the second surface of the glass core layer, wherein the first and second surfaces of the glass core layer are disposed opposite to each other, and the helical conductor structure serves as an inductor. A conductive pillar is formed within the conductive through-hole.

[0020] Optionally, the step of preparing the glass core layer having the spiral through-hole includes: Provide the glass core layer body; A laser-induced modification process is used to form a laser focusing point in the glass core layer body. By moving the laser focusing point, a spiral through-hole modification structure is induced in the glass core layer body. The spiral through-hole modification structure extends from the first surface of the glass core layer body to the second surface of the glass core layer body. The spiral through-hole modified structure of the glass core layer body is etched to obtain a glass core layer with spiral through-holes.

[0021] Optionally, the etching process for the spiral through-hole modified structure is wet chemical etching.

[0022] Optionally, the etching solution for the wet chemical etching is one of hydrofluoric acid, a mixed solution of hydrofluoric acid and hydrochloric acid, nitric acid, sulfuric acid, or ammonium fluoride solution.

[0023] Optionally, when the helical conductor structure includes a conductive layer and a filling layer, the step of forming the glass substrate further includes: Provides a glass core layer with spiral through-holes; A conductive layer is formed on the first surface, the second surface of the glass core layer, and the inner wall of the spiral through-hole; A filling layer is formed on the surface of the conductive layer, such that the conductive layer and the filling layer are sequentially stacked on the first surface and the second surface of the glass core layer and the inner wall of the spiral through hole, thereby forming the spiral conductor structure in the spiral through hole; The conductive layer and filler layer on the first and second surfaces of the glass core layer are removed, so that one end face of the spiral conductor structure is exposed on the first surface of the glass core layer and the other end face of the spiral conductor structure is exposed on the second surface of the glass core layer, thereby obtaining a glass substrate with a spiral conductor structure.

[0024] Optionally, the conductive layer can be fabricated using one of chemical vapor deposition, atomic layer deposition, or electroless plating.

[0025] Optionally, when the filler layer is a copper layer, the copper layer is formed using an electroplating process.

[0026] Optionally, the step of preparing the glass core layer having the conductive via includes: Provide the glass core layer body; Laser-induced modification is used to induce a cylindrical conductive via modified structure in the glass core layer body. The conductive via modified structure extends from the first surface of the glass core layer body to the second surface of the glass core layer body. The conductive via modified structure of the glass core layer body is etched to obtain a glass core layer with conductive vias.

[0027] Optionally, the conductive pillar is prepared using the same process as the spiral conductor structure; the conductive pillar and the spiral conductor structure are formed in the same process.

[0028] Optionally, the manufacturing process of the conductive via is the same as that of the spiral via; the conductive via and the spiral via are formed in the same process.

[0029] Optionally, when the glass substrate with the built-in inductor further includes a first redistribution layer and a second redistribution layer, the first redistribution layer is formed on a first surface of a first glass core layer, and the second redistribution layer is formed on a second surface of a last glass core layer.

[0030] The present invention also provides a method for preparing a glass substrate with a built-in inductor, comprising: A glass substrate with multiple layers of the aforementioned built-in inductors is provided; The glass substrates with built-in inductors in two adjacent layers are bonded together, wherein the second surface of one glass core layer in the two adjacent glass substrates is disposed opposite to the first surface of the other glass core layer, the inductors in the multilayer glass substrates are correspondingly disposed and electrically connected to form a multi-turn inductor, and the conductive pillars in the multilayer glass substrates are correspondingly disposed and electrically connected.

[0031] Optionally, when the glass substrate with the built-in inductor further includes a first redistribution layer and a second redistribution layer, the first redistribution layer is formed on a first surface of the first glass core layer, and the second redistribution layer is formed on a second surface of the last glass core layer.

[0032] In summary, the advantages and beneficial effects of the present invention are as follows: This invention provides a glass substrate with an integrated inductor, a packaging structure, and a method for fabricating the same. The glass substrate with the integrated inductor includes: a glass core layer, an inductor, and conductive pillars; the glass core layer has a helical through-hole and a conductive through-hole; the inductor includes a helical conductor structure; the helical conductor structure is located within the helical through-hole, with one end face of the helical conductor structure located on a first surface of the glass core layer, and the other end face of the helical conductor structure located on a second surface of the glass core layer, wherein the first and second surfaces of the glass core layer are disposed opposite to each other; the conductive pillars are located within the conductive through-holes.

[0033] By embedding the inductor, which was originally mounted on the substrate surface, inside the glass substrate, three-dimensional integration of the inductor in the vertical direction is achieved, which greatly reduces the thickness of the packaged product. At the same time, the spiral conductor structure in the inductor is wrapped, fixed and protected by the glass core layer, which has a much greater resistance to mechanical shock, vibration and bending than the packaging process that mounts the inductor on the substrate surface, and improves the strength of the glass substrate with the inductor built in.

[0034] Furthermore, by bonding the glass substrates containing the multilayer inductors, a multi-turn inductor is obtained. Under the constraints of miniaturization, a high inductance value is achieved, making the packaging structure more efficient in utilizing magnetic fields and more capable of energy transfer or storage.

[0035] Furthermore, the glass substrate with the built-in inductor can be produced on a traditional glass substrate without introducing additional processes, which greatly reduces the risk, time and cost of process development. Attached Figure Description

[0036] Figure 1 A schematic diagram of a glass substrate with a built-in inductor provided in an embodiment of the present invention; Figure 2 A cross-sectional schematic diagram of a glass substrate with a built-in inductor provided in an embodiment of the present invention; Figure 3 A cross-sectional schematic diagram of a glass substrate with a built-in inductor provided for another embodiment of the present invention; Figure 4 A schematic diagram of a glass substrate with a built-in inductor provided in an embodiment of the present invention; Figure 5 A schematic flowchart illustrating a method for fabricating a glass substrate with a built-in inductor, provided in an embodiment of the present invention; Figures 6-10 A schematic flowchart illustrating a method for fabricating a glass substrate with a built-in inductor, provided in an embodiment of the present invention; Figure 11 A schematic diagram illustrating a method for fabricating a glass substrate with a built-in inductor according to an embodiment of the present invention; Figure 12 This is a schematic diagram illustrating a method for preparing a packaging substrate according to an embodiment of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] It should be understood that terms such as “first” and “second” used herein to describe various elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another. For example, the use of terms such as “first” and “second” herein does not imply order or sequence unless the context clearly indicates otherwise. For ease of description, spatially relative terms such as “upper” and “lower” may be used herein to describe the relationship of one element or feature to other elements or features as shown in the accompanying drawings. It should be understood that spatially relative terms are intended to include not only the orientations shown in the accompanying drawings but also different orientations of the device in use or operation.

[0039] In this application, unless otherwise expressly specified and limited, the terms "connected" and "connected" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples. It should be noted that the terms "comprising" and "having," and their variations, used in this application are intended to cover non-exclusive inclusion.

[0041] This invention provides a glass substrate with a built-in inductor, such as... Figure 1 , Figure 2 As shown, it includes: Glass core layer 10, inductor 20 and conductive pillar 30; The glass core layer 10 has a spiral through-hole and a conductive through-hole penetrating the glass core layer 10; The inductor 20 includes a spiral conductor structure 60; the spiral conductor structure 60 is located inside the spiral through hole, and one end face of the spiral conductor structure is located on the first surface of the glass core layer 10, and the other end face of the spiral conductor structure 60 is located on the second surface of the glass core layer 10, wherein the first surface and the second surface of the glass core layer 10 are disposed opposite to each other. The conductive post 30 is located inside the conductive through hole.

[0042] By embedding the inductor, which was originally mounted on the substrate surface, inside the glass substrate, three-dimensional integration of the inductor in the vertical direction is achieved, which greatly reduces the thickness of the packaged product. At the same time, the spiral conductor structure in the inductor is wrapped, fixed and protected by the glass core layer, which has a much greater resistance to mechanical shock, vibration and bending than the packaging process that mounts the inductor on the substrate surface, and improves the strength of the glass substrate with the inductor built in.

[0043] In this embodiment of the invention, the glass core layer 10 is one of a borosilicate glass core layer, an aluminosilicate glass core layer, or an alkali-free aluminoborosilicate glass core layer.

[0044] The glass core layer possesses characteristics such as low dielectric loss, low loss factor, and high resistivity, effectively improving signal transmission integrity and system efficiency. Simultaneously, the low coefficient of thermal expansion of the glass core layer ensures dimensional stability during multiple thermal cycles, preventing deformation of the packaging structure.

[0045] In this embodiment of the invention, the glass core layer 10 has a first surface and a second surface, which are disposed opposite to each other.

[0046] In this embodiment of the invention, the glass core layer 10 has a spiral through-hole and a conductive through-hole that penetrate the glass core layer 10. The spiral through-hole and the conductive through-hole extend from the first surface of the glass core layer 10 to the second surface opposite to the first surface of the glass core layer 10. The spiral through-hole is used to set the spiral conductor structure of the inductor 20, and the conductive through-hole is used to set the conductive post 30.

[0047] In this embodiment of the invention, the spiral through hole is a smooth curve spiral through hole.

[0048] In another embodiment of the present invention, the cross-sectional area of ​​the spiral through-hole gradually converges from the first surface of the glass core layer and then gradually increases until it reaches the second surface of the glass core layer.

[0049] The cross-sectional area of ​​the spiral through-hole adopts a gradually scaling design. Starting from the first surface of the glass core layer, the cross-sectional area (diameter) of the spiral through-hole gradually converges to the minimum in the middle, and then gradually increases symmetrically until it reaches the second surface of the glass core layer. That is, the diameter of the spiral through-hole goes from wide to narrow and then back to wide, realizing a spiral through-hole with expanded diameter at both ends or contracted in the middle. When forming the spiral conductor structure, the gradually scaling cross-section can guide the material to be deposited continuously and uniformly along the hole wall. The expansion section provides a buffer space for the filling layer, allowing the material to grow epitaxially layer by layer, effectively avoiding problems such as premature sealing of the inlet and internal voids or fault defects, significantly improving the quality of the inductor and the reliability of the interconnection.

[0050] When the spiral through-hole is expanded at both ends or contracted in the middle, the cross-sectional area of ​​the spiral through-hole can be set to start from the first surface of the glass core layer and end at the middle of the second surface of the glass core layer, forming a double hourglass or double flared mouth or other suitable shape.

[0051] In other embodiments, the cross-sectional area of ​​the spiral through-hole may also adopt a gradual taper, segmented steps, or other suitable morphology.

[0052] In other embodiments, the spiral through-hole is a square spiral through-hole or other suitable spiral through-hole.

[0053] In this embodiment of the invention, the cross-sectional area of ​​the spiral through-hole on the first surface of the glass core layer 10 is equal to the cross-sectional area of ​​the spiral through-hole on the second surface of the glass core layer 10.

[0054] In other embodiments, the cross-sectional area of ​​the spiral through-hole on the first surface of the glass core layer may not be equal to the cross-sectional area of ​​the spiral through-hole on the second surface of the glass core layer.

[0055] In this embodiment of the invention, the inductor 20 includes a spiral conductor structure 60, which is located in the spiral through-hole within the glass core layer 10.

[0056] In this embodiment of the invention, one end face of the spiral conductor structure 60 is located on the first surface of the glass core layer 10, and the other end face of the spiral conductor structure 60 is located on the second surface of the glass core layer 10.

[0057] In this embodiment of the invention, the spiral conductor structure 60 serves as the coil of the inductor 20, and the number of turns of the spiral conductor structure 60 serves as the number of turns of the coil of the inductor 20.

[0058] In this embodiment of the invention, the spiral conductor structure 60 has several turns to form a complete inductor structure.

[0059] In another embodiment of the present invention, the number of turns of the spiral conductor structure may also be less than one turn.

[0060] When the spiral conductor structure is less than one turn, it effectively provides an arc-shaped channel extending from the first surface of the glass core layer to the second surface of the glass core layer, forming an open filling path. This ensures that the filling material forming the spiral conductor structure can fill continuously and smoothly from beginning to end, avoiding internal voids and ensuring the uniformity and continuity of the formed spiral conductor structure. This results in a void-free, highly dense spiral conductor structure, effectively improving the quality of the formed inductor. Furthermore, by stacking and bonding multiple glass core layers together, multiple spiral conductor structures less than one turn can be connected vertically to form a multi-turn inductor.

[0061] In embodiments of the present invention, such as Figure 2 As shown, the spiral conductor structure 60 includes a conductive layer 61 and a filling layer 62; the conductive layer 61 and the filling layer 62 are sequentially stacked on the inner wall of the spiral through hole.

[0062] In this embodiment of the invention, the conductive layer 61 in the spiral conductor structure 60 is made of one or more of the following materials: titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold.

[0063] In this embodiment of the invention, the filling layer 62 in the spiral conductor structure 60 is a copper layer, which is formed on the surface of the conductive layer 61 by electroplating, and the copper layer fills the spiral through hole.

[0064] In other embodiments, the filling layer in the spiral conductor structure may also be other metals, and may be configured by directly coating a metal paste containing metal particles and volatile solvents onto a glass substrate, or by pre-fabricating a film coated with metal paste and pressing it onto the substrate.

[0065] In the case of the former method, methods for coating or filling the metal paste include, for example, screen printing, inkjet printing, gravure printing, offset printing, flexographic printing, and other printing methods, or combinations of these printing methods, spin coating, dipping, roller coating, doctor blade coating, and pressing. Among these methods, screen printing or doctor blade coating, which directly fills the substrate, and vacuum pressing, which presses a film pre-coated with metal paste, are preferred under a vacuum atmosphere.

[0066] In the latter method, the metal paste can be provided, for example, by forming a metal particle film on a support film having a metal particle layer formed by the metal paste of this embodiment described above, and pressing the metal particle film onto a substrate.

[0067] In other embodiments, the filling layer in the helical conductor structure may also be a non-metallic material layer, such as an organic polymer material layer.

[0068] In this embodiment of the invention, the inductor 20 further includes a first electrode 41 and a second electrode 42, wherein the first electrode 41 is located at one end face of the spiral conductor structure 60 and the second electrode 42 is located at the other end face of the spiral conductor structure 60.

[0069] In this embodiment of the invention, the end face of the spiral conductor structure 60 located on the first surface of the glass core layer 10 serves as the first electrode 41 of the inductor 20, and the end face of the spiral conductor structure 60 located on the second surface of the glass core layer 10 serves as the second electrode 42 of the inductor 20.

[0070] In another embodiment of the present invention, a first cap-shaped conductor layer is provided on one end face of the spiral conductor structure, and a second cap-shaped conductor layer is provided on the other end face of the spiral conductor structure. The first cap-shaped conductor layer serves as the first electrode of the inductor, and the second cap-shaped conductor layer serves as the second electrode of the inductor.

[0071] In this embodiment of the invention, the first electrode 41 and the second electrode 42 are arranged opposite to each other, which facilitates the bonding and alignment of the glass substrate of the subsequent multilayer built-in inductor.

[0072] In another embodiment of the present invention, the glass substrate with the built-in inductor further includes an iron core (not shown) located in the central region of the inductor. The iron core is electrically connected to the spiral conductor structure to reduce the total resistance of the current path and achieve interconnection; or the iron core is electrically isolated from the spiral conductor structure to absorb the electric and magnetic fields generated by the spiral conductor structure and to block external interference to the spiral conductor structure, thereby achieving electromagnetic shielding.

[0073] In another embodiment of the invention, such as Figure 3 As shown, the glass substrate with the built-in inductor further includes a first redistribution layer 101 and a second redistribution layer 102. The first redistribution layer 101 is located on the first surface of the glass core layer 10, and the second redistribution layer 102 is located on the second surface of the glass core layer 10. The first electrode of the inductor is electrically connected to the first redistribution layer, and the second electrode of the inductor is electrically connected to the second redistribution layer. The first redistribution layer 101 serves as the first surface of the glass substrate with the built-in inductor, and the second redistribution layer 102 serves as the second surface of the glass substrate with the built-in inductor.

[0074] In an embodiment of the present invention, the glass substrate with the built-in inductor includes a conductive post 30, which is located in a conductive through hole within the glass core layer 10.

[0075] In this embodiment of the invention, the conductive post 30 includes a conductive layer 61 and a filling layer 62; the conductive layer 61 and the filling layer 62 are sequentially stacked on the inner wall of the conductive through hole.

[0076] In this embodiment of the invention, the conductive layer 61 in the conductive pillar 30 is made of one or more of titanium, nickel, chromium, copper, aluminum, palladium, platinum and gold in a multilayer stacked structure.

[0077] In this embodiment of the invention, the filling layer 62 in the conductive pillar 30 is a copper layer, which is formed on the surface of the conductive layer 61 by electroplating, and the copper layer fills the spiral through hole.

[0078] In other embodiments, the filling layer in the conductive pillar can also be other metals, and can be configured by directly coating a metal paste containing metal particles and volatile solvents onto a glass substrate, or by pre-fabricating a film coated with metal paste and pressing it onto the substrate, etc.

[0079] In the case of the former method, methods for coating or filling the metal paste include, for example, screen printing, inkjet printing, gravure printing, offset printing, flexographic printing, and other printing methods, or combinations of these printing methods, spin coating, dipping, roller coating, doctor blade coating, and pressing. Among these methods, screen printing or doctor blade coating, which directly fills the substrate, and vacuum pressing, which presses a film pre-coated with metal paste, are preferred under a vacuum atmosphere.

[0080] In the latter method, the metal paste can be provided, for example, by forming a metal particle film on a support film having a metal particle layer formed by the metal paste of this embodiment described above, and pressing the metal particle film onto a substrate.

[0081] In other embodiments, the filling layer in the conductive pillar may also be a non-metallic material layer, such as an organic polymer material layer.

[0082] In this embodiment of the invention, the conductive layer and the filling layer in the conductive pillar 30 are made of the same material as the conductive layer and the filling layer in the spiral conductor structure 60, and the conductive pillar 30 and the spiral conductor structure 60 are formed in the same process.

[0083] The present invention also provides a glass substrate with an embedded inductor, comprising multiple glass substrates with the above-mentioned embedded inductors, wherein two adjacent glass substrates are bonded together, wherein the second surface of one glass core layer in the two adjacent glass substrates is disposed opposite to the first surface of the other glass core layer, the inductors in the multilayer glass substrates are correspondingly disposed and electrically connected to form a multi-turn inductor, and the conductive pillars in the multilayer glass substrates are correspondingly disposed and electrically connected.

[0084] By bonding the glass substrates containing the multilayer inductors, a multi-turn inductor 20 is obtained. Under the constraint of miniaturization, a high inductance value is achieved, which makes the packaging structure more efficient in utilizing magnetic fields and has a stronger ability to transfer or store energy.

[0085] In embodiments of the present invention, such as Figure 4 As shown, taking a glass substrate with two layers of built-in inductors as an example, it includes a first glass substrate and a second glass substrate. The second surface of the first glass substrate is disposed opposite to and bonded to the first surface of the second glass substrate. The second surface of the first glass core layer 11 in the first glass substrate is disposed opposite to the first surface of the second glass core layer 12 in the second glass substrate. The first inductor 21 in the first glass substrate and the second inductor 22 in the second glass substrate are correspondingly disposed and electrically connected to form a multi-turn inductor 200. The first conductive post 31 in the first glass substrate and the first conductive post 32 in the second glass substrate are correspondingly disposed and electrically connected.

[0086] In this embodiment of the invention, the first glass core layer 11 in the first glass substrate is bonded to the second glass core layer 12 in the second glass substrate.

[0087] In this embodiment of the invention, a first inductor 21 in the first glass substrate and a second inductor 22 in the second glass substrate are correspondingly disposed and electrically connected to form a multi-turn inductor 200. The second electrode of the first inductor 21 and the first electrode of the second inductor 22 are correspondingly disposed and electrically connected to obtain the multi-turn inductor 200. This allows for the achievement of a high inductance value under the constraint of miniaturization, resulting in higher utilization efficiency of the magnetic field in the packaging structure and stronger energy transfer or storage capabilities.

[0088] In this embodiment of the invention, the first electrode of the first inductor 21 serves as the first electrode of the multi-turn inductor 200, and the second electrode of the second inductor 22 serves as the second electrode of the multi-turn inductor 200.

[0089] In this embodiment of the invention, the first conductive post 31 and the first conductive post 32 are correspondingly arranged and electrically connected to realize the electrical connection between the upper and lower surfaces of the glass substrate.

[0090] In another embodiment of the present invention, the glass substrate of the built-in inductor further includes a first redistribution layer and a second redistribution layer, wherein the first redistribution layer is located on a first surface of the first glass core layer; the second redistribution layer is located on a second surface of the second glass core layer; the first redistribution layer serves as the first surface of the glass substrate of the built-in inductor, and the second redistribution layer serves as the second surface of the glass substrate of the built-in inductor.

[0091] The present invention also provides a packaging structure, including a glass substrate with a built-in inductor as described above and a chip packaged on the surface of the glass substrate, wherein the chip is electrically connected to the inductor.

[0092] This invention also provides a method for preparing a glass substrate with a built-in inductor, such as... Figure 5 As shown, it includes: Step S10: Provide a glass core layer, the glass core layer having a spiral through-hole and a conductive through-hole extending through the glass core layer; Step S20: A spiral conductor structure is formed in the spiral through hole, and one end face of the spiral conductor structure is disposed on the first surface of the glass core layer, and the other end face of the spiral conductor structure is disposed on the second surface of the glass core layer, wherein the first surface and the second surface of the glass core layer are disposed opposite to each other, and the spiral conductor structure serves as an inductor. Step S30: Form a conductive pillar, which is formed within the conductive through hole.

[0093] By embedding the inductor, which was originally mounted on the substrate surface, inside the glass substrate, three-dimensional integration of the inductor in the vertical direction is achieved, which greatly reduces the thickness of the packaged product. At the same time, the spiral conductor structure in the inductor is wrapped, fixed and protected by the glass core layer, which has a much greater resistance to mechanical shock, vibration and bending than the packaging process that mounts the inductor on the substrate surface, and improves the strength of the glass substrate with the inductor built in.

[0094] Furthermore, the glass substrate with the built-in inductor can be produced on a traditional glass substrate without introducing additional processes, which greatly reduces the risk, time and cost of process development.

[0095] Specifically, perform step S10, such as... Figure 6 As shown, a glass core layer 10 is provided, the glass core layer 10 having a spiral through-hole 51 and a conductive through-hole 52 penetrating the glass core layer 10.

[0096] In this embodiment of the invention, the fabrication process of the conductive through-hole 52 is the same as that of the spiral through-hole 52; the conductive through-hole 52 and the spiral through-hole 51 are formed in the same process.

[0097] In this embodiment of the invention, the step of preparing the glass core layer 10 having the spiral through-hole 51 and the conductive through-hole 52 includes: Step S101: Provide the glass core layer body; In an embodiment of the present invention, the glass core layer body has a first surface and a second surface, which are disposed opposite to each other.

[0098] Step S102: Using a laser-induced modification process, a laser focusing point is formed within the glass core layer. By moving the laser focusing point, a spiral through-hole modification structure and a conductive through-hole modification structure are induced within the glass core layer. The spiral through-hole modification structure extends from the first surface of the glass core layer to the second surface of the glass core layer, and the conductive through-hole modification structure extends from the first surface of the glass core layer to the second surface of the glass core layer. In this embodiment of the invention, a laser-induced modification process is used to form the spiral through-hole modified structure and the conductive modified structure within the glass core layer. The laser beam passes through the surface of the glass core layer and is focused at a set depth within the glass core layer. The chemical bonds of the glass at the laser focal point are broken, thereby modifying the glass and inducing the spiral through-hole modified structure and the conductive through-hole modified structure.

[0099] In this embodiment of the invention, a femtosecond laser or a picosecond laser is used to modify the glass core layer body to induce a spiral through-hole modified structure and a conductive through-hole modified structure.

[0100] Step S103: Etch the spiral through-hole modified structure and the conductive through-hole modified structure of the glass core layer body to obtain a glass core layer with spiral through-holes and conductive through-holes.

[0101] In this embodiment of the invention, the first surface of the glass core body serves as the first surface of the glass core 10, and the second surface of the glass core body serves as the second surface of the glass core 10, with the first and second surfaces of the glass core being disposed opposite to each other.

[0102] In this embodiment of the invention, the etching process for the spiral through-hole modified structure and the conductive through-hole modified structure is wet chemical etching.

[0103] In this embodiment of the invention, the etching solution for the wet chemical etching is hydrofluoric acid.

[0104] In this embodiment of the invention, the etching solution for wet chemical etching is one of the following: a mixed solution of hydrofluoric acid and hydrochloric acid, nitric acid, sulfuric acid, or ammonium fluoride solution.

[0105] The laser-modified glass core layer is immersed in an etching solution. The modified spiral through-hole structure and the modified conductive through-hole structure are dissolved at an extremely fast speed, while the unmodified glass core layer body is etched very slowly. This allows the etching solution to advance rapidly along the modification path scanned by the laser, ultimately forming the spiral through-hole and the conductive through-hole.

[0106] In this embodiment of the invention, the diameters of the spiral through-hole and the conductive through-hole are precisely controlled by controlling the laser parameters and etching time.

[0107] In this embodiment of the invention, the spiral through hole is a smooth curve spiral through hole.

[0108] In another embodiment of the present invention, the cross-sectional area of ​​the spiral through-hole gradually converges from the first surface of the glass core layer and then gradually increases until it reaches the second surface of the glass core layer.

[0109] The cross-sectional area of ​​the spiral through-hole adopts a gradually scaling design. Starting from the first surface of the glass core layer, the cross-sectional area (diameter) of the spiral through-hole gradually converges to the minimum in the middle, and then gradually increases symmetrically until it reaches the second surface of the glass core layer. That is, the diameter of the spiral through-hole goes from wide to narrow and then back to wide. When forming the spiral conductor structure, the gradually scaling cross-section can guide the material to be deposited continuously and uniformly along the hole wall. The expansion section provides a buffer space for the filling layer material to fill, allowing the material to grow epitaxially layer by layer, effectively avoiding problems such as premature sealing of the hole neck and leaving gaps or discontinuity defects, significantly improving the quality of the inductor and the reliability of the interconnection.

[0110] In other embodiments, the spiral through-hole is a square spiral through-hole or other suitable spiral through-hole.

[0111] In this embodiment of the invention, the cross-sectional area of ​​the spiral through-hole 51 on the first surface of the glass core layer 10 is equal to the cross-sectional area of ​​the spiral through-hole 51 on the second surface of the glass core layer 10.

[0112] In other embodiments, the cross-sectional area of ​​the spiral through-hole on the first surface of the glass core layer may not be equal to the cross-sectional area of ​​the spiral through-hole on the second surface of the glass core layer.

[0113] In this embodiment of the invention, the spiral conductor structure has several turns to form a complete inductor structure.

[0114] In another embodiment of the present invention, the number of turns of the spiral conductor structure may also be less than one turn.

[0115] When the spiral conductor structure is less than one turn, it effectively provides an arc-shaped channel extending from the first surface of the glass core layer to the second surface of the glass core layer, forming an open filling path. This ensures that the filling material forming the spiral conductor structure can fill continuously and smoothly from beginning to end, avoiding internal voids and ensuring the uniformity and continuity of the formed spiral conductor structure. This results in a void-free, highly dense spiral conductor structure, effectively improving the quality of the formed inductor. Furthermore, by stacking and bonding multiple glass core layers together, multiple spiral conductor structures less than one turn can be connected vertically to form a multi-turn inductor.

[0116] In this embodiment of the invention, the fabrication process of the spiral conductor structure 60 in step S20 is the same as the fabrication process of the conductive pillar 30 in step S30, and the conductive pillar 30 and the spiral conductor structure 60 are formed in the same process.

[0117] In other embodiments, the preparation order of steps S20 and S30 is not important.

[0118] like Figures 7-9 As shown, step S20 is performed to form a spiral conductor structure 60. The spiral conductor structure 60 is formed in the spiral through hole 51, and one end face of the spiral conductor structure 60 is disposed on the first surface of the glass core layer 10, and the other end face of the spiral conductor structure 60 is disposed on the second surface of the glass core layer 10. The first surface and the second surface of the glass core layer 10 are disposed opposite to each other, and the spiral conductor structure 60 serves as an inductor 20. Step S30 is executed to form a conductive post 30, which is formed within the conductive through hole 50.

[0119] In this embodiment of the invention, when both the spiral conductor structure 60 and the conductive pillar include a conductive layer 61 and a filler layer 62, the step of forming the glass substrate further includes: Step S201: Provide a glass core layer 10 with spiral through-holes 51 and conductive through-holes 52 formed thereon; Step S202: A conductive layer 61 is formed on the first surface, the second surface of the glass core layer 10, and the inner wall of the spiral through hole 51 and the conductive through hole 51. Step S203: A filling layer 62 is formed on the surface of the conductive layer 61, such that the conductive layer 61 and the filling layer 62 are sequentially stacked on the first surface and the second surface of the glass core layer 10, as well as on the inner walls of the spiral through-hole 51 and the conductive through-hole 52. Step S204: Remove the conductive layer 61 and the filling layer 62 from the first and second surfaces of the glass core layer, so that one end face of the spiral conductor structure 60 and one end face of the conductive pillar 30 are exposed to the first surface of the glass core layer 10, and the other end face of the spiral conductor structure 60 and the other end face of the conductive pillar 30 are exposed to the second surface of the glass core layer 10, thereby obtaining a glass substrate having the spiral conductor structure 60 and the conductive pillar 30.

[0120] In this embodiment of the invention, the conductive layer 61 is made of one or more of the following materials: titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold.

[0121] In this embodiment of the invention, the preparation process of the conductive layer 61 includes one of chemical vapor deposition, atomic layer deposition, or electroless plating.

[0122] In this embodiment of the invention, the filler layer 62 is formed by an electroplating process.

[0123] In this embodiment of the invention, when the filling layer 62 is a copper layer, a copper layer is formed on the surface of the conductive layer 61 by electroplating, and the copper layer fills the spiral through-hole.

[0124] In other embodiments, the filler layer may also be other metals, and may be configured by directly coating a metal paste containing metal particles and volatile solvents onto a glass substrate, or by pre-fabricating a film coated with metal paste and pressing it onto the substrate.

[0125] In the case of the former method, methods for coating or filling the metal paste include, for example, screen printing, inkjet printing, gravure printing, offset printing, flexographic printing, and other printing methods, or combinations of these printing methods, spin coating, dipping, roller coating, doctor blade coating, and pressing. Among these methods, screen printing or doctor blade coating, which directly fills the substrate, and vacuum pressing, which presses a film pre-coated with metal paste, are preferred under a vacuum atmosphere.

[0126] In the latter method, the metal paste can be provided, for example, by forming a metal particle film on a support film having a metal particle layer formed by the metal paste of this embodiment described above, and pressing the metal particle film onto a substrate.

[0127] In other embodiments, the filler layer may also be a non-metallic material layer, such as an organic polymer material layer.

[0128] In embodiments of the present invention, such as Figure 1 As shown, when the inductor 20 further includes a first electrode 41 and a second electrode 42, the first electrode 41 is formed on one end face of the spiral conductor structure 60, and the second electrode 42 is formed on the other end face of the spiral conductor structure 60.

[0129] In this embodiment of the invention, the end face of the spiral conductor structure 60 located on the first surface of the glass core layer serves as the first electrode 41 of the inductor, and the end face of the spiral conductor structure located on the second surface of the glass core layer serves as the second electrode 42 of the inductor.

[0130] In another embodiment of the present invention, a first cap-shaped conductor layer is formed on one end face of the spiral conductor structure, and a second cap-shaped conductor layer is formed on the other end face of the spiral conductor structure. The first cap-shaped conductor layer serves as the first electrode of the inductor, and the second cap-shaped conductor layer serves as the second electrode of the inductor.

[0131] In this embodiment of the invention, the first electrode and the second electrode are arranged opposite to each other, which facilitates the bonding and alignment of the glass substrates of the subsequent multilayer built-in inductors.

[0132] In another embodiment of the invention, such as Figure 10As shown, when the glass substrate with the built-in inductor further includes a first redistribution layer 101 and a second redistribution layer 102, the first redistribution layer 101 is formed on the first surface of the glass core layer 10, and the second redistribution layer 102 is formed on the second surface of the glass core layer 10. The first electrode of the inductor is electrically connected to the first redistribution layer, and the second electrode of the inductor is electrically connected to the second redistribution layer. The first redistribution layer serves as the first surface of the glass substrate with the built-in inductor, and the second redistribution layer serves as the second surface of the glass substrate with the built-in inductor.

[0133] This invention also provides a method for preparing a glass substrate with a built-in inductor, such as... Figure 11 As shown, it includes: Step S100: Provide a glass substrate with multiple layers of the above-mentioned built-in inductors; Step S200: Bond the glass substrates with the built-in inductors in two adjacent layers together, wherein the second surface of one glass core layer in the two adjacent glass substrates is disposed opposite to the first surface of the other glass core layer, the inductors in the multilayer glass substrates are correspondingly disposed and electrically connected to form a multi-turn inductor, and the conductive pillars in the multilayer glass substrates are correspondingly disposed and electrically connected.

[0134] In this embodiment of the invention, the glass substrates of two adjacent layers of built-in inductors are bonded by a hybrid bonding method.

[0135] In an embodiment of the present invention, when the glass substrate with the built-in inductor further includes a first redistribution layer and a second redistribution layer, after executing step S200, the first redistribution layer is formed on the first surface of the first glass core layer, and the second redistribution layer is formed on the second surface of the last glass core layer.

[0136] By bonding the glass substrates containing the multilayer inductors, a multi-turn inductor is obtained. Under the constraint of miniaturization, a high inductance value is achieved, which makes the utilization efficiency of the magnetic field of the package structure higher and the energy transfer or storage capability stronger.

[0137] This invention also provides a method for preparing a packaging structure, such as... Figure 12 As shown, it includes: Step S1000: Provide a glass substrate and chip with a built-in inductor as described above; Step S2000: The chip is packaged on the surface of a glass substrate with a built-in inductor. The inductor in the glass substrate with the built-in inductor is electrically connected to the chip to form the package structure.

[0138] Finally, it should be noted that any modification or equivalent substitution of some or all of the technical features based on the device structure and the technical solutions of the embodiments of the present invention, without departing from the corresponding technical solutions of the present invention, shall fall within the patent scope of the device structure and the embodiments of the present invention.

Claims

1. A glass substrate with a built-in inductor, characterized in that, include: Glass core layer, inductor and conductive pillars; The glass core layer has a spiral through-hole and a conductive through-hole penetrating the glass core layer; The inductor includes a spiral conductor structure; the spiral conductor structure is located within the spiral through-hole, and one end face of the spiral conductor structure is located on the first surface of the glass core layer, and the other end face of the spiral conductor structure is located on the second surface of the glass core layer, wherein the first surface and the second surface of the glass core layer are disposed opposite to each other; the conductive post is located within the conductive through-hole.

2. The glass substrate with a built-in inductor as described in claim 1, characterized in that, The spiral conductor structure has a number of turns.

3. The glass substrate with a built-in inductor as described in claim 1, characterized in that, The spiral conductor structure has fewer than one turn.

4. The glass substrate with a built-in inductor as described in claim 1, characterized in that, The cross-sectional area of ​​the spiral through-hole gradually converges from the first surface of the glass core layer and then gradually increases to the second surface of the glass core layer. Correspondingly, the cross-sectional area of ​​the spiral conductor structure gradually converges from one end face of the spiral conductor structure and then gradually increases to the other end face of the spiral conductor structure.

5. A glass substrate with a built-in inductor as described in claim 1, characterized in that, The inductor further includes a first electrode and a second electrode, the first electrode being located at one end face of the helical conductor structure and the second electrode being located at the other end face of the helical conductor structure.

6. The glass substrate with a built-in inductor as described in claim 5, characterized in that, One end face of the spiral conductor structure serves as the first electrode of the inductor, and the other end face of the spiral conductor structure serves as the second electrode of the inductor; or one end face of the spiral conductor structure is provided with a first cap-shaped conductor layer, and the other end face of the spiral conductor structure is provided with a second cap-shaped conductor layer, wherein the first cap-shaped conductor layer serves as the first electrode of the inductor, and the second cap-shaped conductor layer serves as the second electrode of the inductor.

7. A glass substrate with a built-in inductor as described in claim 1, characterized in that, The spiral conductor structure includes a conductive layer and a filling layer; the conductive layer and the filling layer are sequentially stacked on the inner wall of the spiral through hole.

8. A glass substrate with a built-in inductor as described in claim 7, characterized in that, The filling layer can be a metallic filling layer or a non-metallic filling layer.

9. A glass substrate with a built-in inductor as described in claim 1, characterized in that, It also includes an iron core located in the central region of the inductor, which is electrically connected to or electrically isolated from the spiral conductor structure.

10. A glass substrate with a built-in inductor as described in claim 1, characterized in that, The first surface of the glass core layer has a first redistribution layer, and the second surface of the glass core layer has a second redistribution layer.

11. A glass substrate with a built-in inductor as described in claim 1, characterized in that, The glass core layer includes one of a borosilicate glass core layer, an aluminosilicate glass core layer, or an alkali-free aluminoborosilicate glass core layer.

12. A glass substrate with a built-in inductor, characterized in that, The invention includes a multilayer glass substrate with an inductor as described in claim 1, wherein two adjacent glass substrates are bonded together, wherein the second surface of one glass core layer in the two adjacent glass substrates is disposed opposite to the first surface of the other glass core layer, the inductors in the multilayer glass substrate are correspondingly disposed and electrically connected to form a multi-turn inductor, and the conductive pillars in the multilayer glass substrate are correspondingly disposed and electrically connected.

13. A glass substrate with a built-in inductor as described in claim 12, characterized in that, The first surface of the first glass core layer has a first redistribution layer, and the second surface of the last glass core layer has a second redistribution layer.

14. A packaging structure, characterized in that, The device includes a glass substrate with a built-in inductor as described in claim 1 or 12 and a chip encapsulated on the surface of the glass substrate, wherein the chip is electrically connected to the inductor.

15. A method for preparing a glass substrate with a built-in inductor, characterized in that, include: A glass core layer is provided, the glass core layer having a spiral through-hole and a conductive through-hole extending through the glass core layer; A helical conductor structure is formed within the helical through-hole, with one end face of the helical conductor structure disposed on the first surface of the glass core layer and the other end face of the helical conductor structure disposed on the second surface of the glass core layer, wherein the first and second surfaces of the glass core layer are disposed opposite to each other, and the helical conductor structure serves as an inductor. A conductive pillar is formed within the conductive through-hole.

16. The method for preparing a glass substrate with a built-in inductor as described in claim 15, characterized in that, The steps for preparing the glass core layer having the spiral through-hole include: Provide the glass core layer body; A laser-induced modification process is used to form a laser focusing point in the glass core layer body. By moving the laser focusing point, a spiral through-hole modification structure is induced in the glass core layer body. The spiral through-hole modification structure extends from the first surface of the glass core layer body to the second surface of the glass core layer body. The spiral through-hole modified structure of the glass core layer body is etched to obtain a glass core layer with spiral through-holes.

17. The method for preparing a glass substrate with a built-in inductor as described in claim 15, characterized in that, The etching process for the spiral through-hole modified structure is wet chemical etching.

18. The method for preparing a glass substrate with a built-in inductor as described in claim 17, characterized in that, The etching solution used in the wet chemical etching process is one of the following: hydrofluoric acid, a mixed solution of hydrofluoric acid and hydrochloric acid, nitric acid, sulfuric acid, or ammonium fluoride solution.

19. The method for preparing a glass substrate with a built-in inductor as described in claim 15, characterized in that, When the spiral conductor structure includes a conductive layer and a filling layer, the step of forming the glass substrate further includes: Provides a glass core layer with spiral through-holes; A conductive layer is formed on the first surface, the second surface of the glass core layer, and the inner wall of the spiral through-hole; A filling layer is formed on the surface of the conductive layer, such that the conductive layer and the filling layer are sequentially stacked on the first surface and the second surface of the glass core layer and the inner wall of the spiral through hole, thereby forming the spiral conductor structure in the spiral through hole; The conductive layer and filler layer on the first and second surfaces of the glass core layer are removed, so that one end face of the spiral conductor structure is exposed on the first surface of the glass core layer and the other end face of the spiral conductor structure is exposed on the second surface of the glass core layer, thereby obtaining a glass substrate with a spiral conductor structure.

20. The method for preparing a glass substrate with a built-in inductor as described in claim 19, characterized in that, The conductive layer is prepared using one of the following methods: chemical vapor deposition, atomic layer deposition, or electroless plating.

21. The method for preparing a glass substrate with a built-in inductor as described in claim 19, characterized in that, When the filler layer is a copper layer, the copper layer is formed by an electroplating process.

22. The method for preparing a glass substrate with a built-in inductor as described in claim 15, characterized in that, The steps for preparing the glass core layer having the conductive vias include: Provide the glass core layer body; Laser-induced modification is used to induce a cylindrical conductive via modified structure in the glass core layer body. The conductive via modified structure extends from the first surface of the glass core layer body to the second surface of the glass core layer body. The conductive via modified structure of the glass core layer body is etched to obtain a glass core layer with conductive vias.

23. The method for preparing a glass substrate with a built-in inductor as described in claim 15, characterized in that, The conductive pillar is prepared using the same process as the spiral conductor structure; the conductive pillar and the spiral conductor structure are formed in the same process.

24. The method for preparing a glass substrate with a built-in inductor as described in claim 15, characterized in that, The conductive via is prepared using the same process as the spiral via; the conductive via and the spiral via are formed in the same process.

25. The method for preparing a glass substrate with an embedded inductor as described in claim 15, characterized in that, When the glass substrate with the built-in inductor further includes a first redistribution layer and a second redistribution layer, the first redistribution layer is formed on the first surface of the first glass core layer, and the second redistribution layer is formed on the second surface of the last glass core layer.

26. A method for preparing a glass substrate with a built-in inductor, characterized in that, include: Provide a multilayer glass substrate with an integrated inductor as described in claim 1; The glass substrates with built-in inductors in two adjacent layers are bonded together, wherein the second surface of one glass core layer in the two adjacent glass substrates is disposed opposite to the first surface of the other glass core layer, the inductors in the multilayer glass substrates are correspondingly disposed and electrically connected to form a multi-turn inductor, and the conductive pillars in the multilayer glass substrates are correspondingly disposed and electrically connected.

27. A glass substrate with a built-in inductor as described in claim 26, characterized in that, When the glass substrate with the built-in inductor also includes a first redistribution layer and a second redistribution layer, the first redistribution layer is formed on the first surface of the first glass core layer, and the second redistribution layer is formed on the second surface of the last glass core layer.

Images