Power module with encapsulated component and manufacturing process for this module
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN SA
- Filing Date
- 2023-01-24
- Publication Date
- 2026-06-12
Abstract
Description
Description Title of the invention: Power module with component encapsulated and manufacturing process of this module TECHNICAL FIELD OF THE INVENTION
[0001] — The present invention relates to a power module in which the component power electronics is coated in an encapsulating resin comprising various permittivities to limit breakdown phenomena. The invention also relates to a method of manufacturing this power module.
[0002] — The invention finds applications in the field of power electronics and, in particular, the field of assembly of electronic components of power in a power circuit board. TECHNOLOGICAL BACKGROUND OF THE INVENTION
[0003] Power modules are generally used, in the field of power electronics, to control actuators, machines, motors, etc. The classic power modules 10, an example of which is shown in the [Fig.1], generally include power electronic components 11 connected to the surface of a substrate 12 by soldering. These electronic components of power 11 are connected to the electrical circuit through wiring wires 13 electrical devices fixed on their upper face. In fact, the most widespread technique of connecting power electronic components is the use of wires wiring 13, the conductive element of which is generally made of gold, aluminum or copper. To allow the passage of a strong current. while reducing the resistance of the interconnections, several wiring wires are generally used in parallel.
[0004] These modules are called power modules because they allow the circulation of a strong electric current and high voltage. that is to say having a voltage greater than 1000 Volts. However, the high voltage environment may be subject to severe electrical constraints such as humidity, partial discharges, breakdowns in dry air (of the order of 3kVDC / mm), etc., likely to damage power electronic components (more simply called component or power component — as opposed to low voltage components). For To protect these components from the external environment, it is usual to encapsulate them, as well as their wiring wires, in a protective resin allowing in particular to improve the breakdown threshold (which can then reach 25kVDC / mm). However, This threshold may prove insufficient for certain high voltage applications being given that the threshold for the occurrence of partial discharge is well below the threshold of breakdown. To increase power density, it has been proposed to bury power electronic components in substrates, which also facilitates their 3D integration. One of the burying techniques consists of burying the component directly in a printed circuit (or PCB for "Printed Circuit Board" in English terminology) by benefiting from encapsulation of the components thanks to the pre-impregnated materials of the printed circuit. This technique, already known for low voltage components, without severe electrical constraints in the environment, comprises, as shown in [Fig. 3], a first step 21 of positioning the component 11 on a substrate 16. It then comprises a step 22 of coating the component by lamination of the pre-impregnated materials. Once the components are encapsulated, they must be connected to the electrical circuit. For this, two techniques are generally used: The first method is to solder the components 11 on the internal face 14 of the printed circuit board, as shown in [Fig.2]. This method has the disadvantage that the solder 15 connecting the components to the circuit printed is not protected and may be damaged during the final steps. prior to brazing. The second method is to perform laser drilling of vias 17 intended, after a step 24 of copper electroplating, to form inter- connections to electrically supply component 11. If this second method has the advantage of being easily reproducible industrially, However, it has drawbacks. One of these drawbacks comes from the components used which, for the most part, have a metallized finish aluminum which is not compatible with copper plating. If it is possible to make a metallic deposit on the metallizations in aluminum, to make them compatible with electroplating, this This operation is delicate and expensive, which greatly limits the choice of components to be buried. The power component burying technique described above, which consists of burying the power component directly in the printed circuit board in the same way as a low-voltage component, has the disadvantage of generating excessively high electrical stresses in certain areas, such as triple interface areas. Indeed, certain areas of the power component, in particular the corners of the component, i.e. the triple interface areas, called triple points, which are at the interface between three materials (in particular the metallization of the component, the copper of the upper layer of the component and the encapsulation resin), can present very high electrical stresses of up to 120KV / DC. Such high electrical stress generally leads to significant local heating, which which causes degradation of the encapsulation resin as well as the appearance of partial discharges inducing irreversible degradation of the electrical insulator, i.e. the pre-impregnated material in which the component is encapsulated. Summary of the invention To address the above-mentioned problems of high electrical stresses in certain areas of power components buried in a printed circuit, the applicant proposes a power module in which a permittivity gradient is created in the vicinity of these areas with high electrical stresses. The applicant also proposes a method for manufacturing such a power module. The term "permittivity" refers to the characteristic quantity of dielectric materials (here pre-impregnated materials) in the vicinity of the component. The term "permittivity gradient" refers to a non-constant permittivity whose value varies increasing or decreasing depending on the distance from the component. A permittivity gradient is obtained when at least two permittivities of distinct values, and preferably three or more, coexist in the same region of the power module. It should be remembered that high voltage concerns electrical voltage values greater than 1000 volts, that low voltage concerns electrical voltage values less than 1000 volts and that very low voltage concerns electrical voltage values less than or equal to 75 volts. According to a first aspect, the invention relates to a power module comprising at least one electronic power component buried in a printed circuit, said printed circuit comprising: a first and a second conductive substrate, and an encapsulating resin housed between the first and second substrates conductors and encapsulating the electronic component, the encapsulation resin comprising at least two distinct permittivities, the encapsulation resin extending away from the component comprising a first permittivity and the encapsulation resin extending close to the electronic component comprising a second permittivity, greater than the first permittivity. This power module has the advantage of offering a permittivity adapted to the considered area of the power electronic component, the permittivity being higher in the areas with high electrical stresses in order to protect the dielectric (or insulating) materials of the PCB. Such a power module has a reduced value of the electric field at the level of these areas with high electrical stresses, such as the triple points, by increasing the limit of the voltage of appearance of partial discharges and the increase of the breakdown voltage in the assembly. It thus has an improved dielectric strength and a robust assembly against the aging under electrical stress (such as partial discharges). In the description, the term "remote or remote zone" means the zones of the power module which are not directly in contact with the power component or around the triple points (or other zones with high electrical stresses), as opposed to the so-called "nearby" or "in the vicinity" zones which are directly in contact with the power component and / or the triple points of said component. In addition to the characteristics which have just been mentioned in the preceding paragraph, the power module according to one aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: the encapsulating resin is formed from at least a first sheet pre-impregnated positioned at a distance from the electronic component and from at least a second pre-impregnated sheet positioned near a predefined area of the electronic component. the encapsulating resin is formed from at least three pre- impregnated with different permittivities, the at least three pre- impregnated being arranged so as to form a permittivity gradient around the electronic component and / or the predefined area of said component electronic. the encapsulating resin is formed from a first pre-sheet impregnated interior with permittivity el positioned at a distance from the component electronics, and at least one second interior pre-impregnated sheet permittivity e2 and a third inner pre-impregnated sheet with permittivity €3, stacked on top of each other, the third inner pre-impregnated sheet being positioned as close as possible to the predefined area of the electronic component- tronic, with £3 >e2 > el. the second and third inner pre-impregnated sheets are arranged horizontally on top of each other to form a vertical stack between first two outer pre-impregnated sheets. the second and third inner pre-impregnated sheets are arranged vertically against each other to form a horizontal stack between first two outer pre-impregnated sheets, the second pre-impregnated sheet impregnated interior being arranged vertically between the first sheet inner pre-impregnated and the third inner pre-impregnated sheet, the third pre-impregnated sheet being in contact with the electronic component electronics. A second aspect of the invention relates to a method of manufacturing a power module according to the first aspect, the method comprising the following operations: (a) cutting out at least one central cavity and one lateral cavity in a first inner pre-impregnated sheet, (b) installation, in the lateral cavity, of at least a second pre-sheet impregnated internally, c) laying the first inner pre-impregnated sheet on a first outer pre-impregnated sheet, d) installation of the electronic component in the central cavity, €) laying of a second outer pre-impregnated sheet on the second inner pre-impregnated sheet and the first in- pre-impregnated sheet interior, f) laying a first and a second conductive substrate, respectively, under / on the first and second outer pre-impregnated sheets, g) rolling of the assembly obtained in step f). This process has the advantage of being very easily reproducible from an industrial point of view. It allows the burying of high-voltage power components in a PCB on an industrial scale. It also allows the miniaturization of power modules, which follows the current trend of increasing the power of modules while reducing their size and mass. The manufacturing process may include the following additional characteristics, considered individually or in all technically possible combinations: operation a) of cutting cavities involves cutting a cavity central and at least two lateral cavities arranged on either side of the central cavity. the lateral cavities are vertical and parallel to each other. it includes a final step h) of making vias through the resin encapsulation to connect the electronic component. the first outer pre-impregnated sheets and the first pre- impregnated interior are superimposed and centered on each other at using a centering tool. BRIEF DESCRIPTION OF THE FIGURES Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which: The |Fig.1], already described, represents a perspective view of an example of power module according to the state of the art; [Fig. 2], already described, represents a schematic view of an example of connection of a power component in a printed circuit board according to the state of the technique; [Fig. 3], already described, represents, according to a functional diagram, a method of mounting a power component in a printed circuit board according to the state of the art; [Fig.4A] and [Fig.4B] each schematically represent a view of side, in section, of a power module, respectively, according to a first and a second embodiment of the invention; [Fig.5] represents the permittivity of a zone with high electrical stresses of a power component of a power module according to the invention, compared to those of state-of-the-art power modules; [Fig.6] shows different examples of pre-impregnated materials that can be used for the manufacture of a power module according to the invention; [Fig.7] represents several stages of the manufacturing process of the module of power of [Fig.4B]; and [Fig.8] represents several states of the power module of [Fig.4A] at during the manufacturing process, when these states are different from those of the power module of [Fig.4B]. In the figures, identical elements are identified by identical references. For reasons of readability of the figures, the size scales between elements represented are not respected. DETAILED DESCRIPTION An exemplary embodiment of a power module and its manufacturing method are described in detail below, with reference to the attached drawings. This example illustrates the characteristics and advantages of the invention. It is however recalled that the invention is not limited to this example. Power modules according to two embodiments of the invention are shown in Figures 4A and 4B. Whatever the embodiment, the power module according to the invention, referenced 100, comprises a printed circuit 120 in which is inserted a high-voltage power semiconductor component 110, called a power component or simply a component. The printed circuit 120 comprises a first conductive substrate 121 and a second conductive substrate 122 between which extends an encapsulation resin 130 for the power component 110. According to the invention, the encapsulating resin 130 is in the form of several layers, or strata, of pre-impregnated materials agglomerated with each other following a rolling operation described later. The layers of pre-impregnated materials are formed from several pre-impregnated sheets 131-135 having specific dielectric properties. A pre-impregnated sheet consists of a relatively homogeneous mixture of resin and reinforcing fibers. Various resins and reinforcing fibers can be used to form a pre-impregnated sheet. There are therefore different types of pre-impregnated sheets depending on the resin and reinforcing fibers chosen, each type of pre-impregnated sheet having specific properties such as, for example, a specific thickness, resin proportion and / or permittivity. The resins can be, for example, phenolic, polyester, epoxy or any other resin conventionally used in the field of printed circuits. The fibers can be, for example, glass (E-glass), Aramid, carbon or any other fiber conventionally used in the field of printed circuits. Depending on the resin and reinforcing fibers chosen, the thickness of the pre-impregnated sheet can vary; it is, for example, between 32um and 190um.Similarly, the proportion of resin in the pre-impregnated sheet can also vary. Depending on the choice of resin and reinforcing fibers and on the thickness and proportion of resin, the dielectric properties of the pre-impregnated sheet (in particular the permittivity) are also variable from one type of pre-impregnated sheet to another. Several examples of pre-impregnated sheets (also called "pre-pregs") are illustrated in [Fig.6]. For example: the pre-impregnated sheet of type A, in [Fig.6], has a thickness of about 50jum, a proportion of about 70% resin and a permittivity € between 2.8 and 3.7. the pre-impregnated sheet of type B, in [Fig.6], has a thickness between about 90 and 110um, a proportion of about 50% resin and a permittivity € between 3.6 and 3.8. the pre-impregnated sheet of type C, in [Fig.6], has a thickness between approximately 60 and 70m, a proportion of approximately 60% resin and a permittivity € between 3.2 and 3.7. the pre-impregnated sheet of type D, in [Fig.6], has a thickness between about 170 and 190um, a proportion of about 45% resin and a permittivity € between 4.1 and 4.6. The power modules 100 of FIGS. 4A and 4B thus comprise several pre-impregnated sheets 131-135 superimposed and / or arranged next to each other so as to form, after lamination, an encapsulation resin 130 comprising at least two different permittivities. As explained in more detail below, the encapsulation resin comprising the highest permittivity extends close to the power component 110 and in particular in the vicinity of one or more areas with high electrical stresses, such as the triple points 115, while the encapsulation resin having the lowest permittivity extends into more distant areas. of the component 110. Indeed, the pre-impregnated sheets are arranged so as to form a permittivity gradient around the power component with a permittivity value which decreases as the distance from the power component 110 increases and in particular from the areas with high electrical stresses 115 of said component. For example, an encapsulation resin of a power module according to the invention can be formed from two types of pre-impregnated sheets: a first type of pre-impregnated sheet of permittivity el and a second type of pre-impregnated sheet of permittivity e2 (with el < e2), the second type of pre-impregnated sheet being arranged at least partially around the power component 110 while the first type of pre-impregnated sheet is arranged around the second type of pre-impregnated sheet. More than two types of pre-impregnated sheets can be used to form the encapsulation resin, for example three or four. In the two examples of Figures 4A and 4B, the encapsulating resin 130 of the power module 100 is formed from four types of pre-impregnated sheets. The encapsulating resin 130 is formed in particular from two outer pre-impregnated sheets (the first outer pre-impregnated sheet 131 and the second outer pre-impregnated sheet 132) and a set of inner pre-impregnated sheets 133 and 134 / 135. The two outer pre-impregnated sheets 131, 132 are of the same type, preferably the first type of pre-impregnated sheets of permittivity e1. The set of inner pre-impregnated sheets is composed of four different types of pre-impregnated sheets: a first type of pre-impregnated sheet 133 of permittivity el, called first inner pre-impregnated sheet, a second type of pre-impregnated sheet 134a of permittivity e2, called second inner pre-impregnated sheet, a third type of pre-impregnated sheet 134b of permittivity e3, called third inner pre-impregnated sheet, and a fourth type of 134c pre-impregnated sheet of permittivity €4, called fourth inner pre-impregnated sheet, with el < 2 < £3 < £4, In these two examples (FIGS. 4A and 4B), the power component 110 is arranged in the middle of the encapsulation resin 130, between the first and second conductive substrates 121, 122 of the printed circuit 120. The encapsulation resin 130 comprises a first and a second outer pre-impregnated sheet 131, 132 of the first type, the first outer pre-impregnated sheet 131 covering the first conductive substrate 121 and the second outer pre-impregnated sheet 132 being covered by the second conductive substrate 122. The lower face 111 of the power component 110 is therefore in contact with the first outer pre-impregnated sheet 131 and the upper face 112 of the power component 110 is in contact with the first outer pre-impregnated sheet 131 and the upper face 112 of the power component 110 is in contact with the first outer pre-impregnated sheet 131. contact with the second outer pre-impregnated sheet 132, The set of inner pre-impregnated sheets 133 / 134 comprises a first inner pre-impregnated sheet 133, at least partly hollowed out to receive, on the one hand, the power component 110 and, on the other hand, a stack of the second, third and fourth inner pre-impregnated sheets 134. In the example of [Fig.4A], the stack 134 of the second, third and fourth inner pre-impregnated sheets (respectively 134a, 134b, 134c) is a horizontal stack, each of the inner pre-impregnated sheets being arranged vertically in the YZ plane, i.e. perpendicular to the XZ plane containing the conductive substrates 121, 122. The second 134a, third 134b and fourth 134c inner pre-impregnated sheets are placed side by side with each other, or separated by a thin wall of the first pre-impregnated sheet 133, the thickness of the separating wall being very small compared to the thickness of a pre-impregnated sheet.In this example, the second inner prepreg sheet 134a is in contact with the first inner prepreg sheet 133, the fourth inner prepreg sheet 134c is closest to or in contact with the side faces 113 of the power component 110 and the third inner prepreg sheet 134b is disposed between the second and fourth prepreg sheets 134a, 134c. Each of the first, second, third and fourth inner prepreg sheets is therefore in contact with both the first and second outer prepreg sheets 131, 132. Thus, in this example of [Fig.4A], each of the triple points 115 of the power component 110 is at least partially surrounded by an encapsulation resin having a permittivity of value e4, that is to say, the value of which is high. As the distance from the power component 110 increases, the value of the permittivity decreases until it is of value el. The encapsulation resin 130 of the power module 100 according to the example of [Fig.4A] therefore has a decreasing permittivity gradient. The power module 100' of [Fig.4B] is partly identical to the power module 100 of [Fig.4A], only the set of inner pre-impregnated sheets 133 / 135 being different. Indeed, just like the power module 100, the power module 100' comprises an encapsulating resin 130 formed of a first and a second outer pre-impregnated sheets 131, 132 of the first type, where the first outer pre-impregnated sheet 131 covers the first conductive substrate 121 and the second outer pre-impregnated sheet 132 is covered by the second conductive substrate 122. In the example of [Fig.4B], the set of inner pre-impregnated sheets 133 / 135 comprises a first inner pre-impregnated sheet 133, at least in hollowed-out portion for receiving, on the one hand, the power component 110 and, on the other hand, the stack 135 of the second, third and fourth inner pre-impregnated sheets. This stack 135 of the second, third and fourth inner pre-impregnated sheets (respectively 135a, 135b, 135c) is a vertical stack where each inner pre-impregnated sheet is superimposed on the previous pre-impregnated sheet. The pre-impregnated sheets 135a-135c are therefore arranged horizontally in the XZ plane, that is to say in the same plane as the conductive substrates 121, 122.The second 135a, third 135b and fourth 135c inner prepreg sheets are superimposed on each other, the second inner prepreg sheet 135a being in contact with the second outer prepreg sheet 132, the fourth inner prepreg sheet 135c being in contact with the first outer prepreg sheet 131, the third inner prepreg sheet 134b being disposed between the second and fourth prepreg sheets 135a, 135c. Each of the second, third and fourth inner prepreg sheets is therefore in contact with both the first inner prepreg sheet 133 and the side faces 113 of the power component 110. Thus, in this example of [Fig.4B], each of the triple points 115 of the power component 110 is at least partially surrounded by an encapsulation resin having a permittivity of a value greater than the value el of the first inner and outer pre-impregnated sheets. The encapsulation resin therefore has a permittivity gradient between the first conductive substrate 121 and the second conductive substrate 122. Those skilled in the art will understand that other sets of pre-impregnated sheets may be envisaged, with more or fewer pre-impregnated sheets and more or fewer types of pre-impregnated sheets. Different stacks of the different pre-impregnated sheets may also be envisaged as long as they provide a permittivity gradient around the power component. In particular, the high permittivity pre-impregnated sheets may be deposited in a localized manner on the surface of the power components at the locations where the electric fields must be particularly enhanced. Regardless of the embodiment, the power module 100, 100” of Figures 4A and 4B comprises a power component 110 coated with an encapsulation resin 130 with a permittivity gradient, ensuring a reduction in electrical stresses at predefined areas, such as the triple points. An example of the permittivity obtained at a triple point of a power component coated as explained previously is shown on line B of [Fig. 5], in comparison with another component shown on line A. More specifically, [Fig. 5] shows, in a first column (column D), different examples of encapsulation resins of a power component and, in a second column (column E), the permittivities obtained for the components encapsulated with these resins. Row A of [Fig. 5] shows a component whose triple point p3 is encapsulated in a silicone gel and row B of [Fig. 5] shows a component according to the invention whose triple point p3 is encapsulated in a resin with a permittivity gradient. The component in row A has a permittivity of the order of 4.5, it being understood that the permittivity in a conventional printed circuit is generally of the order of 3. The component in row C, i.e. the component encapsulated in the resin with a permittivity gradient, has a permittivity reaching 23, which is considered in the field as a high permittivity. An example of a method of manufacturing the power module 100' described above is shown in [Fig. 7]. This method 200 includes a preliminary step (not shown in [Fig. 7]) of choosing the types of pre-impregnated sheets to be used to obtain the power module 100°. The method 200 then comprises a step 210 of cutting cavities c1, c2 and / or c3 in a first inner pre-impregnated sheet 133. The first inner pre-impregnated sheet 133 is represented (for step 110) in the XZ plane, i.e. according to a sectional view along the Y axis, unlike the power module 100” which is represented, whatever its state (i.e. during steps 220, 230, 240, 250, 260 and 270), in the XY plane, i.e. according to a sectional view along the Z axis. This first inner pre-impregnated sheet 133 comprises at least one central cavity c1 designed to receive the power component 110 and a lateral cavity c2 designed to receive the stack 135 of inner pre-impregnated sheets. According to the embodiments, the first inner pre-impregnated sheet 133 comprises at least one central cavity c1 designed to receive the power component 110 and a lateral cavity c2 designed to receive the stack 135 of inner pre-impregnated sheets. The inner prepreg 133 may include one or more other lateral cavities positioned along sides of the component 110, for example the cavity c3.Alternatively, the first inner pre-impregnated sheet 133 may comprise a single lateral cavity c2 in the shape of a crown (circular) or a frame (square or rectangular) positioned around the power component 110. The method 200 then comprises a step 220 of installing the pre-impregnated sheets of the stack 135 in one or more of the lateral cavities c2, c3, the number of pre-impregnated sheets of the stack 135 being able to vary from one to four, five or more depending on the applications. In the example of [Fig.7], a stack of three pre-impregnated sheets 135a, 135b, 135c is deposited in the lateral cavity c2. An identical stack 135 is also deposited in the other lateral cavity c3. The method 200 continues with a step 230 of placing the set of inner pre-impregnated sheets 133 / 135 on the first outer pre-impregnated sheet 131 and inserting the power component 110 into the central cavity cl of said set. then continues with a step 240 consisting of depositing the second outer pre-impregnated sheet 132 above the set of inner pre-impregnated sheets 133 / 135, then with a step 250 consisting of depositing the assembly of pre-impregnated sheets on the first conductive substrate 121, then with a step 260 consisting of depositing the second conductive substrate 122 above the second outer pre-impregnated sheet 122. Finally, the method 200 comprises a step 270 of laminating the assembly obtained in step 260. Indeed, the assembly obtained in step 260, and comprising the two conductive substrates 121, 122 between which are arranged the two outer pre-impregnated sheets 131, 132 as well as the set of inner pre-impregnated sheets 133 / 135 and the component 110, is laminated in accordance with conventional techniques for assembling electronic cards, by placing the assembly between two heating jaws 275. These jaws 275 apply pressure to the assembly so that the pre-impregnated sheets are laminated together and the resin they contain fills all the cavities c1, c2, c3 of the assembly. The 100” power module thus obtained thus comprises an encapsulation resin presenting a vertical permittivity gradient (referenced gv in [Fig.7]) around the power component 110, the vertical permittivity gradient having an increasing (or decreasing) permittivity value in the Y direction. According to one embodiment of the method 200, the first and second outer pre-impregnated sheets 131, 132 as well as the first inner pre-impregnated sheet 133 are superimposed and centered on each other by means of a centering tool. This centering tool may comprise one or more rods, or punches, onto which centering holes made in each of the pre-impregnated sheets to be superimposed are threaded. The method 200 of the invention may comprise an additional step of producing vias making it possible to establish an electrical connection between two layers of printed circuit and with the power component 110. These vias may, for example, be produced in two stages: firstly, chemical etching makes it possible to remove the conductive material from the conductive substrates 121, 122 of the printed circuit; then, laser drilling makes it possible to produce holes in the encapsulation resin 130; finally, an electrodeposition of copper, or another conductive material, makes it possible to metallize the holes to form the connections of the component 110. The method 200 has just been described for the manufacture of a power module 100 conforming to the example of [Fig.4B]. The same method can be implemented to manufacture a power module 100 conforming to the example of [Fig.4A], only the step of installing the pre-impregnated sheets of the stack being different. Examples of the module 100, at different stages of manufacture, are shown in the [Fig. 8]. In particular, the reference 310 represents the power module 100 in the XZ plane (i.e. a sectional view along the Y axis), during the step of cutting the cavities in the first inner pre-impregnated sheet 133. In this step 310, the method consists of cutting a central cavity c1 intended to receive the power component 110 as well as a plurality of lateral cavities, for example six lateral cavities c4-c9 parallel to each other. In this step 310, the lateral cavities c4-c9 are vertical cavities (i.e. whose height h is greater than the width l), each lateral cavity being provided to receive a pre-impregnated sheet. In the example of [Fig.8], the lateral cavities are six in number, with three lateral cavities on either side of the central cavity cl; of course, the number of lateral cavities can vary (at least one lateral cavity on either side of cl), the number of cavities being identical on each side of the central cavity cl. Alternatively, each lateral cavity can surround the central cavity cl, the lateral cavities c4-c9 then having a crown or frame shape corresponding to the shape of the central cavity cl and therefore to the shape of the power component 110. . Reference 340 of [Fig.8] represents the power module 100 in the XY plane (i.e. according to a sectional view along the Z axis) during the operation of laying the pre-impregnated sheets 134a-134c. In this step 340 of the manufacturing method, each of the lateral cavities c4-c9 is filled with a pre-impregnated sheet. If three lateral cavities have been made on either side (or around) the central cavity cl, then three separate pre-impregnated sheets 134a, 134b, 134c are deposited in the lateral cavities to form a horizontal stack 134, each of the inner pre-impregnated sheets being arranged vertically in the YZ plane, perpendicular to the XZ plane containing the conductive substrates 121, 122.The second 134a, third 134b and fourth 134c inner pre-impregnated sheets are joined to each other, or separated by a thin wall of first pre-impregnated sheet 133, so that the fourth inner pre-impregnated sheet 134c is as close as possible to the central cavity cl. Reference 370 of [Fig. 8] represents the power module 100 in the XY plane (i.e. according to a sectional view along the Z axis) during the rolling operation of the assembly formed of the conductive substrates 121, 122 between which the module 100 is housed as obtained in step 340 and in which the power component 110 is inserted. Indeed, the assembly comprising the two conductive substrates 121, 122, the two outer pre-impregnated sheets 131, 132 as well as the set of inner pre-impregnated sheets 133 / 134 and the component 110 is rolled in accordance with conventional techniques for assembling electronic cards, by placing the assembly between two heating jaws 375. These jaws 375 apply pressure to the assembly so that the pre-impregnated sheets are laminated together and that the resin they contain fills all the cavities c1, c4-c9 of the assembly. The power module 100 thus obtained thus comprises an encapsulation resin having a horizontal permittivity gradient (referenced gh in [Fig.8]) around the power component 110, the horizontal permittivity gradient having an increasing (or decreasing) permittivity value in the X direction. The other steps of manufacturing the power module 100, not shown in [Fig. 8], are identical to steps 220, 230 and 260 of the method 200 described for the manufacturing of the power module 100°, only the stack 134 of the pre-impregnated sheets of the power module 100 differing from the stack 135 of the power module 100. Although described through a certain number of examples, variants and embodiments, the power module according to the invention and its manufacturing method include various variants, modifications and improvements which will be obvious to those skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.
Claims
Claims
1. Power module (100, 100”) comprising at least one component power electronics (110) buried in a printed circuit (120), said printed circuit comprising: a first and a second conductive substrate (121, 122), and an encapsulating resin (130) housed between the first and the second conductive substrates and encapsulating the component electronic, characterized in that the encapsulating resin (130) comprises at least two distinct permittivities (e1l,e2), the encapsulating resin extending at a distance from the component comprising a first permittivity el and the encapsulating resin extending close to the electronic component tronic (110) comprising a second permittivity e2, greater than the first permittivity.
2. Power module according to claim 1, characterized in that the encapsulating resin (130) is formed from at least one first pre-impregnated sheet (131, 132, 133) positioned at a distance of the electronic component (110) and at least one second sheet pre-impregnated (134, 135) positioned near a predefined area (115) of the electronic component.
3. Power module according to claim 2, characterized in that the encapsulating resin (130) is formed from at least three sheets pre-impregnated (133, 135 / 134a, 135 / 134b, 135 / 134c) with permittivities different, the at least three pre-impregnated sheets being arranged in so as to form a permittivity gradient (gh, gv) around the component electronics (110) and / or the predefined area (115) of said component electronic.
4. : Power module according to claim 3, characterized in that the encapsulating resin (130) is formed from: of a first inner pre-impregnated sheet with permittivity el (133) positioned at a distance from the electronic component, and of at least one second inner pre-impregnated sheet permittivity e2 (135 / 134a) and a third pre-sheet impregnated interior with permittivity e3 (135 / 134b), stacked one on top of the other, the third inner pre-impregnated sheet being positioned as close as possible to the predefined zone (115) of the electronic component, with €3 > e2 > el.
5. Power module according to claim 4, characterized in that the second and third inner pre-impregnated sheets (135a, 135b) are arranged horizontally on top of each other to form an em- vertical stacking (135) between two first pre-impregnated sheets ex- interior (131, 132).
6. Power module according to claim 4, characterized in that the second and third inner pre-impregnated sheets (134a, 134b) are arranged vertically against each other to form an em- horizontal stacking (134) between two first pre-impregnated sheets outer (131, 132), the second inner pre-impregnated sheet (134a) being arranged vertically between the first pre- impregnated inner (133) and the third pre-impregnated sheet in- inner (134b), the third pre-impregnated sheet (134b) being in contact with the electronic component (110).
7. Method of manufacturing (200) a power module according to one any of claims 1 to 6, the method comprising the following operations: a cutout (210) of at least one central cavity (c1) and a lateral cavity (c2 — c9) in a first pre-sheet impregnated interior (133), b. installation, in the lateral cavity (c2-c9), of at least one second pre-impregnated inner sheet (135 / 134a), C. laying the first inner pre-impregnated sheet (133) on a first outer pre-impregnated sheet (131), d. installation of the electronic component (110) in the cavity central (cl), e laying of a second outer pre-impregnated sheet (132) on the second inner pre-impregnated sheet (135 / 134a) and the first inner pre-impregnated sheet (133), £ laying of a first and a second conductive substrate (121, 122), respectively, under and on the first and second outer pre-impregnated sheets (131, 132), g rolling of the assembly obtained in step f).
8. Method according to claim 7, characterized in that the operation a) of cavity cutting involves cutting a central cavity (cl) and of at least two lateral cavities (c2-c9) arranged on either side of the central cavity.
9. Method according to claim 8, characterized in that the cavities lateral (c4-c9) are vertical and parallel to each other.
10. | Method according to any one of claims 7 to 9, characterized in which includes a final step h) of making vias through the encapsulating resin for connecting the electronic component.
11. | Method according to any one of claims 7 to 10, characterized in what the first outer pre-impregnated sheets (131, 132) and the first inner pre-impregnated sheet (133) are superimposed and centered on each other using a centering tool.