Power module and method of manufacturing a power module

Abstract

The present invention relates to a power module and a method of manufacturing a power module. A power module comprises a substrate, an insulation portion, at least one chip and a cooling device, the substrate comprising an insulation layer, a first metal layer arranged on one surface of the insulation layer and a second metal layer arranged on the other surface of the insulation layer, the insulation portion being arranged on one surface of the substrate, the insulation portion having a circuit pattern embedded in the insulation portion, the at least one chip being mounted on the substrate within the insulation portion, the at least one chip being connected to the circuit pattern, the cooling device being connected to the substrate, the cooling device having at least one cooling channel.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2025-0046267, filed on April 9, 2025, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to power modules and methods for manufacturing power modules. Background Technology

[0004] Inverters can be used to drive motors in hybrid vehicles, electric vehicles, and other similar applications. An inverter can convert direct current (DC) power to alternating current (AC) power, or vice versa. An inverter may include a power module comprising semiconductor chips that perform switching functions. During operation of the power module, heat may be generated in the semiconductor chips due to high current. This heat can cause the temperature of the power module to rise, which may adversely affect its operation. For stable operation of the power module, it may be necessary to dissipate the heat generated in the semiconductor chips to cool the power module.

[0005] Embedded power modules are used as a form of power module. An embedded power module can refer to a power module in which power semiconductor devices (chips) that perform power conversion and supply functions are directly embedded in a printed circuit board (PCB) or substrate.

[0006] As a method for cooling power modules, indirect cooling methods and direct cooling methods can be used. An indirect cooling method may involve inserting a material such as a thermal interface material (TIM) into the space between the substrate and the cooling channel, and transferring heat from the substrate to the cooling channel through the inserted material. A direct cooling method may be a method that allows heat transfer to occur with the substrate and cooling channel directly connected to each other. Summary of the Invention

[0007] One aspect of the present invention is to provide a power module that is advantageous for miniaturization and a method for manufacturing the power module.

[0008] Another aspect of the present invention is to provide a power module with improved cooling performance and a method for manufacturing the power module.

[0009] According to one aspect of the present invention, a power module is provided, comprising a substrate, an insulating portion, at least one chip, and a cooling device. The substrate has an insulating layer, a first metal layer disposed on one surface of the insulating layer, and a second metal layer disposed on the other surface of the insulating layer. The insulating portion is disposed on one surface of the substrate and has a circuit pattern embedded therein. The at least one chip is mounted on the substrate within the insulating portion and is connected to the circuit pattern. The cooling device is connected to the substrate and has at least one cooling groove.

[0010] According to another aspect of the present invention, a method for manufacturing a power module is provided, the method comprising: a chip mounting operation of mounting a chip on one surface of a substrate; an insulation portion forming operation of laminating and curing an insulating sheet on one surface of the substrate to form an insulating portion; a circuit pattern space forming operation of removing a portion of the insulating portion to form a circuit pattern space; a circuit pattern forming operation of injecting conductive material into the circuit pattern space to form a circuit pattern; and a cooling device fixing operation of fixing a cooling device to another surface of the substrate.

[0011] According to an exemplary embodiment of the present invention, the power module can be miniaturized.

[0012] According to an exemplary embodiment of the invention, the power module can have improved cooling performance. Attached Figure Description

[0013] The above and other aspects, features and advantages of the invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0014] Figure 1 This is a schematic cross-sectional view of a power module according to an exemplary embodiment of the present invention;

[0015] Figure 2 This is a schematic cross-sectional view of a power module according to another exemplary embodiment of the present invention;

[0016] Figure 3 This is a flowchart of a method for manufacturing a power module according to another exemplary embodiment of the present invention;

[0017] Figure 4 This is a cross-sectional view of a power module manufacturing method according to another exemplary embodiment of the present invention, showing a chip mounted on a substrate.

[0018] Figure 5 This is a cross-sectional view of the state in which the insulating portion is formed in a power module manufacturing method according to another exemplary embodiment of the present invention;

[0019] Figure 6 This is a cross-sectional view of the state of forming a circuit pattern space in a power module manufacturing method according to another exemplary embodiment of the present invention;

[0020] Figure 7 This is a cross-sectional view of the state of forming a circuit pattern in a power module manufacturing method according to another exemplary embodiment of the present invention;

[0021] Figure 8 yes Figure 7 A plan view of the circuit pattern formed in the process; and

[0022] Figure 9 This is a cross-sectional view of the cooling device being attached to a substrate in a power module manufacturing method according to another exemplary embodiment of the present invention. Detailed Implementation

[0023] Various modifications can be made to the example implementation. Here, the example implementation should not be construed as limiting to the present invention, and should be understood to include all changes, equivalents and alternatives within the concept and technical scope of the present invention.

[0024] Components may be described herein using terms such as first, second, A, B, (a), (b), etc. Each of these terms is not intended to define the nature, order, or sequence of the corresponding component, but only to distinguish the corresponding component from other components. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component. The term "and / or" may include a combination of multiple related descriptive terms or any one of multiple related descriptive terms.

[0025] Terms such as “unit,” “part,” and “component” can be used to describe various components, but components should not be limited by terms. The terms mentioned above can refer to terms that indicate not only physically / visually distinct components, but also the function or component of the corresponding part, even in the absence of explicit division or separation.

[0026] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to limit the exemplary embodiments. As used herein, the singular forms “a,” “an,” and “described” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and / or” includes any one of the associated enumerations and any combination of any two or more items. It will be further understood that when the terms “comprising” and / or “including” are used in this invention, it specifies the presence of the stated feature, value, operation, task, element, component, or combination thereof, but does not exclude the presence or addition of one or more other features, values, operations, tasks, elements, components, and / or groups thereof.

[0027] Unless otherwise defined herein, all terms used herein, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art. Unless otherwise defined herein, terms defined in common dictionaries shall be interpreted as having a meaning that matches the contextual meaning in the relevant art and shall not be interpreted as having an idealized or overly formal meaning.

[0028] In the following description, the terms “front,” “back,” “up,” “down,” “top,” “bottom,” etc., used in relation to direction are defined based on the accompanying drawings.

[0029] Preferred exemplary embodiments of the invention will be described in more detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic cross-sectional view of a power module according to an exemplary embodiment of the present invention. (Reference) Figure 1 According to an example embodiment of the present invention, the power module 1 may include a substrate 100, an insulating portion 200, a chip 300, and a cooling device 400.

[0031] The substrate 100 may include an insulating layer 110, a first metal layer 120, and a second metal layer 130. The insulating layer 110 may include at least one of ceramic or polymer resin. For example, the insulating layer 110 may include at least one of alumina, aluminum nitride, silicon nitride, epoxy resin, or polyimide. For example, the insulating layer 110 may be provided in the form of a plate.

[0032] The first metal layer 120 may be disposed on one surface of the insulating layer 110. The first metal layer 120 may include a plurality of circuit lines. The circuit lines of the first metal layer 120 may be electrically connected to at least one of the chip 300, power leads, or signal leads. For example, the first metal layer 120 may be electrically connected to at least one of the chip 300, power leads, or signal leads by means of a circuit pattern 210 formed in the insulating portion 200. The power leads may be formed of a conductive material electrically connected to the chip 300 to supply power to the chip 300 or output power converted by the chip 300. The signal leads may be formed of a conductive material electrically connected to the chip 300 to input control signals to the chip 300 or receive status information of the chip 300. The first metal layer 120 may be configured as a conductor with high conductivity. For example, the first metal layer 120 may include at least one of copper, aluminum, silver, or nickel. The first metal layer 120 may be formed using lamination, deposition, or plating methods. The method of forming the first metal layer 120 may be replaced by various methods commonly used in the art to which this invention pertains.

[0033] The second metal layer 130 can be disposed on the other surface of the insulating layer 110. Here, the ratio (i.e., volume ratio) of the volume (v1) of the first metal layer 120 to the volume (v2) of the second metal layer 130 can be 1:1. Here, the volume (v1) of the first metal layer 120 can be the volume of the space formed by the outer edge of the first metal layer 120. The volume (v2) of the second metal layer 130 can be the volume of the space defined by the outer edge of the second metal layer 130. Forming a volume ratio of 1:1 between the first metal layer 120 and the second metal layer 130 can minimize the warpage of the substrate 100.

[0034] The cooling device 400 can be connected to the second metal layer 130. For example, the cooling device 400 can be connected to the second metal layer 130 such that at least a portion of the second metal layer 130 is disposed in the cooling tank 410 of the cooling device 400. When the chip 300 mounted on the substrate 100 operates, heat may be generated. The heat generated in the chip 300 can be transferred to the second metal layer 130. The heat generated from the chip 300 can be dissipated outward through the second metal layer 130. The second metal layer 130 can be configured as a conductor with high thermal conductivity. For example, the second metal layer 130 may include at least one of copper or aluminum. The second metal layer 130 can be formed using lamination, deposition, or plating processes. The method of forming the second metal layer 130 can be replaced by various methods commonly used in the art to which this invention pertains.

[0035] At least one auxiliary cooling groove 131 may be provided in the second metal layer 130. The auxiliary cooling groove 131 may be provided on the outer surface of the second metal layer 130. For example, the auxiliary cooling groove 131 may be provided on a surface of the second metal layer 130 that is not opposite to the insulating layer 110. The auxiliary cooling groove 131 may be formed by recessing a portion of a surface of the second metal layer 130 inward to a predetermined depth. When the cooling device 400 is connected to the substrate 100, the auxiliary cooling groove 131 may be connected to the cooling groove 410 of the cooling device 400. The auxiliary cooling groove 131 may form a cooling path CP for the flow of coolant together with the cooling groove 410 provided in the cooling device 400.

[0036] The insulating portion 200 may be disposed on one surface of the substrate 100. The insulating portion 200 may be a prepreg. The prepreg may be an intermediate substrate of a fiber-reinforced composite material, exhibiting excellent flowability and adhesion in a semi-cured state, and thus serving as an adhesive layer or insulating layer. For example, the prepreg (a molding material in which a matrix resin is pre-impregnated into reinforcing fibers) may be an adhesive sheet in which resin (BT / epoxy resin, FR4, FR5, etc.) is impregnated into glass fibers. Furthermore, the insulating portion 200 may be a thermosetting or thermoplastic polymer substrate, a ceramic substrate, an organic / inorganic composite substrate, or a glass fiber impregnated substrate. When the insulating portion 200 comprises a polymer resin, it may comprise an epoxy-based insulating resin or a polyimide-based resin.

[0037] Circuit pattern 210 can be disposed within insulating portion 200. Circuit pattern 210 can electrically connect chip 300 and lead portions to each other; that is, chip 300 and power leads or chip 300 and signal leads. Circuit pattern 210 can be embedded within insulating portion 200. For example, at least a portion of circuit pattern 210 can be disposed within insulating portion 200. A portion of circuit pattern 210 can be exposed on a surface of insulating portion 200. For example, refer to… Figure 1 The circuit pattern 210 may be exposed on the upper surface of the insulating portion 200. Power leads or signal leads may be connected to the circuit pattern exposed on one surface of the insulating portion 200. For example, the circuit pattern exposed on one surface of the insulating portion 200 may be joined or wired to the power leads or signal leads using a conductive component such as a power bus bar.

[0038] At least one chip 300 may be mounted on the substrate 100. For example, the chip 300 may be mounted on the first metal layer 120 of the substrate 100. The chip 300 may be disposed in an insulating portion 200. In other words, the chip 300 may be embedded in the insulating portion 200. For example, the outer surface of the chip 300 may be surrounded by the insulating portion 200. The chip 300 may be electrically connected to the first metal layer 120 and the circuit pattern 210. The first metal layer 120 and the circuit pattern 210 may form circuit lines for driving the power module 1. The chip 300 may be embedded in the insulating portion 200 and connected to the circuit pattern 210 embedded in the insulating portion 200, so that the power module 1 according to the exemplary embodiment of the present invention can be facilitated by miniaturization.

[0039] Chip 300 may include at least one of an insulated-gate bipolar transistor (IGBT), a compound semiconductor (SiC), a sorting circuit, a silicon controlled rectifier (SCR), a power transistor, a MOS transistor, a power rectifier, a power regulator, or a diode. Chip 300 may be connected to power leads and signal leads. For example, chip 300 may be connected to power leads and signal leads via at least one of a first metal layer 120 or a circuit pattern 210. Chip 300 may be a switching device. Chip 300 may convert power supplied through the power leads and output the converted power. For example, chip 300 may receive direct current (DC), convert DC to alternating current (AC), and output AC, or it may receive AC, convert AC to DC, and output DC.

[0040] The cooling device 400 can be connected to the substrate 100. For example, the cooling device 400 can be connected to a portion of the substrate 100 where the second metal layer 130 is provided. A sealing member for water tightness can be provided between the cooling device 400 and the substrate 100. The cooling device 400 may include a cooling tank 410. The cooling tank 410 can form a cooling flow path CP for coolant to flow therethrough together with an auxiliary cooling tank 131 formed in the substrate 100. Cooling fluid can flow in the cooling flow path.

[0041] In the power module 1 according to an exemplary embodiment of the present invention, the second metal layer 130 of the substrate 100 can be configured as part of the cooling flow path CP, thereby shortening the distance between the chip 300 and the coolant and cooling device 400, thus improving the cooling performance of the power module 1. Furthermore, an auxiliary cooling tank 131 can be formed in the second metal layer 130, thereby increasing the surface area in contact with the cooling fluid (coolant), further improving the cooling performance of the power module 1. Because the power module 1 has improved cooling performance, deformation of the substrate 100 caused by heat can be minimized.

[0042] Figure 2 This is a schematic cross-sectional view of a power module 1 according to another exemplary embodiment of the present invention. (See reference) Figure 2 According to another exemplary embodiment of the present invention, the power module 1 may include a substrate 100, an insulating portion 200, a chip 300, and a cooling device 400. In addition to the configuration of the insulating portion 200, Figure 2 The power module 1 shown in another exemplary embodiment of the present invention can be coupled with... Figure 1 The power modules shown in the example embodiments according to the present invention are substantially the same. Accordingly, detailed descriptions of the same configurations are omitted and replaced with the above description.

[0043] The insulating portion 200 may be disposed on one surface of the substrate 100. The insulating portion 200 may be a prepreg. The prepreg may be an intermediate substrate of a fiber-reinforced composite material, exhibiting excellent flowability and adhesion in a semi-cured state, and thus serving as an adhesive layer or insulating layer. For example, the prepreg (a molding material in which a matrix resin is pre-impregnated into reinforcing fibers) may be an adhesive sheet in which resin (BT / epoxy resin, FR4, FR5, etc.) is impregnated into glass fibers. Furthermore, the insulating portion 200 may be a thermosetting or thermoplastic polymer substrate, a ceramic substrate, an organic / inorganic composite substrate, or a glass fiber impregnated substrate. When the insulating portion 200 comprises a polymer resin, it may comprise an epoxy-based insulating resin or a polyimide-based resin.

[0044] The circuit pattern 210 can be disposed within the insulating portion 200. The circuit pattern 210 can electrically connect the chip 300 and the lead portion to each other, that is, the chip 300 and the power lead to each other or the chip 300 and the signal lead to each other. The circuit pattern 210 can be embedded within the insulating portion 200.

[0045] The insulating portion 200 may include a plurality of insulating layers 200a and 200b. The plurality of insulating layers 200a and 200b may have opposing surfaces that are bonded to each other. Although Figure 2 The diagram shows a configuration in which two insulating layers 200a and 200b are joined together, but the number of insulating layers is not limited thereto, and the insulating portion 200 may include three or more insulating layers depending on structural or design requirements.

[0046] Multiple insulating layers 200a and 200b may each include circuit pattern portions 210a and 210b. The circuit pattern portions 210a and 210b formed in the multiple insulating layers 200a and 200b can form a circuit pattern 210. For example, a circuit pattern portion 210a formed in one of the multiple insulating layers 200a can be electrically connected to at least one of the first metal layer 120, the chip 300, or a circuit pattern portion 210b formed in an adjacent insulating layer 200b to form a circuit pattern 210.

[0047] At least a portion of the circuit pattern 210 may be exposed on a surface of the uppermost insulating layer 200b among the plurality of insulating layers 200a and 200b. The circuit pattern 210 exposed on a surface of the uppermost insulating layer 200b may include a power lead connection 211 (see [link to relevant documentation]). Figure 8 ) and signal lead junction 212 (see Figure 8 The power lead connection 211 and the signal lead connection 212 can be connected to the power lead and the signal lead, respectively.

[0048] Figure 3 This is a flowchart of a method for manufacturing a power module according to another exemplary embodiment of the present invention. (See reference) Figure 3 A method for manufacturing a power module according to another exemplary embodiment of the present invention may include a chip mounting operation (S100), an insulating portion forming operation (S200), a circuit pattern space forming operation (S300), a circuit pattern forming operation (S400), and a cooling device fixing operation (S500).

[0049] refer to Figure 4 In the chip mounting operation (S100), chip 300 can be mounted on substrate 100. Various methods commonly used in the art to which this invention pertains can be used as methods for mounting chip 300 on substrate 100, such as sintering and soldering. Substrate 100 may include an insulating layer 110, a first metal layer 120 disposed on one surface of insulating layer 110, and a second metal layer 130 disposed on the other surface of insulating layer 110. Chip 300 can be mounted on the surface of substrate 100 on which the first metal layer 120 is disposed. Chip 300 can be electrically connected to circuit lines formed on the first metal layer 120. The second metal layer 130 may have at least one auxiliary cooling groove 131. The auxiliary cooling groove 131 can form a cooling flow path CP for coolant flow together with the cooling groove 410 disposed in the cooling device 400, which will be described below.

[0050] refer to Figure 5 After the chip 300 is mounted on the substrate 100, an insulating portion forming operation (S200) can be performed. In the insulating portion forming operation (S200), an insulating portion 200 can be formed. For example, the insulating portion 200 can be formed by laminating and curing an insulating sheet on the substrate 100. For example, the insulating sheet can be a prepreg sheet. In other words, the insulating portion 200 can be a prepreg. The prepreg (a molding material in which a matrix resin is pre-impregnated into reinforcing fibers) can be, for example, an adhesive sheet in which resin (BT / epoxy resin, FR4, FR5, etc.) is impregnated into glass fibers. The insulating portion 200 can be formed to cover one surface of the substrate 100 and the chip 300.

[0051] refer to Figure 6 After forming the insulating portion 200, a circuit pattern space forming operation (S300) can be performed. In the circuit pattern space forming operation (S300), a circuit pattern space 200c can be formed. The circuit pattern space 200c can be formed by removing a portion of the insulating portion 200. For example, the circuit pattern space 200c can be formed by cutting and drilling the insulating portion 200. The circuit pattern space 200c can have a circuit pattern 210 to be formed in the insulating portion 200 (see...). Figure 7The shape corresponding to the shape of ).

[0052] The circuit pattern space 200c can be configured as multiple segmented regions. A portion of the circuit pattern space 200c can be connected to the chip 300. Other portions of the circuit pattern space 200c can be connected to the substrate 100.

[0053] refer to Figure 7 and Figure 8 After forming the circuit pattern space 200c, a circuit pattern forming operation (S400) can be performed. In the circuit pattern forming operation (S400), a circuit pattern 210 can be formed in the insulating portion 200. The circuit pattern 210 can be formed by injecting a conductive material into the circuit pattern space 200c. For example, the conductive material can be copper (Cu). The circuit pattern 210 can be electrically connected to the chip 300 or the substrate 100. At least a portion of the circuit pattern 210 can be exposed on a surface of the insulating portion 200. The circuit pattern 210 exposed on a surface of the insulating portion 200 can include a power lead connection 211 and a signal lead connection 212. The power lead connection 211 and the signal lead connection 212 can be connected to a power lead and a signal lead, respectively.

[0054] The insulating portion forming operation (S200), the circuit pattern space forming operation (S300), and the circuit pattern forming operation (S400) can be repeated multiple times. In this case, the insulating portion 200 can have a shape in which multiple layers are bonded together (see...). Figure 2 Circuit patterns can be formed on each of multiple layers, and circuit patterns formed on multiple layers can be electrically connected to the chip.

[0055] refer to Figure 9 After forming the circuit pattern 210, a cooling device fixing operation (S500) can be performed. In the cooling device fixing operation (S500), the cooling device 400 can be fixed to the substrate 100. The cooling device 400 can be bonded to a portion of the substrate 100 where the second metal layer 130 is provided. At least a portion of the second metal layer 130 can be arranged in the cooling tank 410 of the cooling device 400. The auxiliary cooling tank 131 of the second metal layer 130 can form a cooling flow path CP together with the cooling tank 410 of the cooling device 400.

[0056] While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and alterations may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A power module comprising: A substrate, comprising an insulating layer, a first metal layer disposed on one surface of the insulating layer, and a second metal layer disposed on the other surface of the insulating layer; An insulating portion is disposed on one surface of the substrate, the insulating portion having a circuit pattern embedded therein; At least one chip, the at least one chip being mounted on the substrate within the insulating portion, the at least one chip being connected to the circuit pattern; as well as A cooling device connected to the substrate, the cooling device having at least one cooling tank.

2. The power module according to claim 1, wherein, At least one auxiliary cooling tank is disposed on the outer surface of the second metal layer, and the auxiliary cooling tank together with the cooling tank forms a cooling flow path.

3. The power module according to claim 1, wherein, The volume ratio of the first metal layer to the second metal layer is 1:

1.

4. The power module according to claim 1, wherein, The insulating portion comprises multiple laminated insulating layers.

5. The power module according to claim 4, wherein, Each of the plurality of insulating layers includes a circuit pattern portion that forms a circuit pattern.

6. The power module according to claim 4, wherein, At least a portion of the circuit pattern is exposed on one surface of the uppermost insulating layer among a plurality of insulating layers.

7. The power module according to claim 6, wherein, The lead portion is connected to a circuit pattern on a surface exposed to the insulating layer.

8. The power module according to claim 1, wherein, The insulating part is made of prepreg.

9. The power module according to claim 1, wherein, The first metal layer includes copper, aluminum, silver, or nickel.

10. The power module according to claim 1, wherein, The insulating portion includes a thermosetting or thermoplastic polymer substrate, a ceramic substrate, an organic / inorganic composite material substrate, or a glass fiber impregnated substrate.

11. A method of manufacturing a power module, the method comprising: Chip mounting operation, which involves mounting a chip onto one surface of a substrate. An insulating portion formation operation involves laminating and curing an insulating sheet on one surface of a substrate to form an insulating portion. A circuit pattern space forming operation that removes a portion of the insulation to form the circuit pattern space. Circuit patterning is an operation in which conductive material is injected into a circuit pattern space to form a circuit pattern. The cooling device is fixed to the other surface of the substrate during the cooling device fixing operation.

12. The method according to claim 11, wherein, In the insulation part forming operation, the insulation sheet is set as a prepreg sheet.

13. The method according to claim 11, wherein, In the circuit pattern space formation operation, a portion of the circuit pattern space is connected to the chip, and the other portion of the circuit pattern space is connected to the substrate.

14. The method according to claim 11, wherein, The circuit pattern of the circuit pattern forming operation is exposed on one surface of the insulating part.

15. The method according to claim 11, wherein, The insulation part forming operation, the circuit pattern space forming operation, and the circuit pattern forming operation are repeated multiple times, and the insulation part has a shape in which multiple layers are combined with each other.

16. The method according to claim 15, wherein, The circuit pattern is formed on each of the plurality of layers, and the circuit pattern formed on the plurality of layers is electrically connected to the chip.

17. The method according to claim 11, wherein, The substrate includes an insulating layer, a first metal layer disposed on one surface of the insulating layer, and a second metal layer disposed on the other surface of the insulating layer; During the cooling device fixing operation, the cooling device is connected to the portion of the substrate that has a second metal layer.

18. The method according to claim 17, wherein, The first metal layer includes copper, aluminum, silver, or nickel.

19. The method according to claim 11, wherein, The insulating portion includes a thermosetting or thermoplastic polymer substrate, a ceramic substrate, an organic / inorganic composite material substrate, or a glass fiber impregnated substrate.

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