Printed circuit board, associated electronic device and manufacturing process

Abstract

Printed circuit board, associated electronic device and manufacturing process. This printed circuit board (12) includes a via (20), which is formed through the board and includes a first barrel (21), the first barrel being made of metal, configured to dissipate heat from an electronic component (16), for example a voltage amplifier, and defining a first internal volume (V21). The via (20) includes a second barrel (22), which is different from the first barrel (21), which is made of metal and is received in the first internal volume (V21) coaxially with the first barrel (21). The second barrel (22) is bonded to the first barrel (21) by means of a first polymer resin (32) and is configured to dissipate the heat generated by the electronic component (16). Figure for the abbreviation: Figure 1

Description

Title of the invention: Printed circuit board, electronic device and associated manufacturing process

[0001] The present invention relates to a printed circuit board, as well as an electronic device comprising such a printed circuit board. The invention also relates to a method for manufacturing such a printed circuit board.

[0002] In the field of printed circuit boards, also known as PCBs (printed circuit board), certain electronic components mounted on the surface of the board are likely to heat up and require cooling. Surface-mounted components are also referred to by the acronym SMD, while surface-mount technology is known by the acronym SMT, from the English "surface mount technology".

[0003] It is known to place a metallic insert, preferably made of copper, within the PCB. This insert passes through the PCB, with the component mounted on one side of the PCB above the insert, so that the insert dissipates heat generated by the component through the PCB. A heat sink is generally placed in contact with the insert on the opposite side of the PCB. However, the metallic insert has a coefficient of thermal expansion very different from that of the PCB, which is generally made of several layers of polymer resin, for example, polyester or epoxy resin, pressed together. By way of illustration, a PCB has a coefficient of thermal expansion on the order of 18 x 10⁶ / K in a plane parallel to the PCB; in other words, for a temperature difference of 1 Kelvin, a PCB one meter long expands by 18 micrometers. The coefficient of expansion is also expressed as 18 ppm / °C.The same PCB exhibits a coefficient of thermal expansion "in Z", that is, along a direction orthogonal to the plane of the PCB, of the order of 50 to 200 x 10⁶ / K, while copper has an isotropic coefficient of thermal expansion of the order of 17 x 10⁶ / K. Thus, the difference in thermal expansion generates thermomechanical stresses inside the PCB, which may develop cracks at the interface between the copper insert and the PCB.

[0004] It is also known to create vias through the PCB. Generally, a via is formed by a hole drilled through the PCB, which is covered with a layer of metal, particularly copper, deposited by metallization. This produces a metallic shaft, which is then generally sealed with a polymer resin. Typically, the hole has a diameter of several hundred microns, for example 300 µm, while the thickness of the metal layer is typically on the order of 18 to 25 µm, or even up to 30 µm. Thus, one or more vias are The vias are positioned under the component to be cooled, depending on the component size or space constraints. Thanks to the relatively thin metal, the vias generate little to no thermomechanical stress related to thermal expansion. However, the efficiency of heat dissipation is limited by the thin metal.

[0005] It is these problems that the invention intends to remedy in particular, by proposing a printed circuit board with an improved cooling capacity for surface-mounted components, without however generating thermomechanical stresses.

[0006] To this end, the invention relates to a printed circuit board, in which: - the board has two opposite faces, the two opposite faces including a top face and a bottom face and being orthogonal to a height axis, - the map includes a via, which is provided across the map and extends along a main axis parallel to the vertical axis, - the via includes a first shaft, which is made of metal, which extends along the main axis and has an upper end, which is flush with the upper face, and a lower end, which is located opposite the upper end along the main axis, - the first barrel is configured to dissipate heat from an electronic component, for example a voltage amplifier, when the electronic component is fixed to the upper face, resting against the upper end of the first barrel, and is in operation, - the via includes a second shaft, which is different from the first shaft, which is made of metal and which is arranged in a first internal volume of the first shaft coaxially with the first shaft, the second shaft having an upper end, which is flush with the upper face of the card, and a lower end opposite the upper end, - the second drum is joined to the first drum using a first polymer resin, - the second barrel is configured to dissipate the heat generated by the operating electronic component.

[0007] Thanks to the invention, two coaxial metal tubes jointly contribute to the dissipation of heat generated by surface-mounted components. In cross-section orthogonally to the main axis, the two concentric tubes present a quantity of metal, relative to the surface area of ​​the PCB, significantly greater than what is achievable by using simple vias, even when these vias are as close together as possible.

[0008] For example, in a square exchange surface of area A, it is possible to position four vias having a disc of diameter D and tangent by their pellets to the pellet of the same diameter D of one fifth via positioned at the center of the square of the exchange surface. This geometric configuration combines side C of the square to the surface A of it such WeC = x[A Such a surface contains two barrels. metallic. The diameters of the pellets are such that D = The density The copper density obtained by cross-section of the via shafts per unit area varies according to the diameter of the via's pellet. Assuming a copper thickness of 25 µm and a bored diameter of the shaft 300 µm smaller than the pellet diameter, this density increases to -3.1% copper for small pellet diameters, then decreases for diameters greater than 650 µm, reaching 2.0% copper when the pellet reaches a diameter of 1.5 mm. In a configuration where two shafts are nested such that the bored diameter of the outer shaft matches the pellet diameter of the inner shaft, the copper density per unit area reaches a maximum of 4.25% with a pellet diameter of 925 µm for the outer shaft. This represents a 35% increase in copper density, thus improving thermal energy transfer.

[0009] Furthermore, each drum is filled with resin, which has a coefficient of thermal expansion similar to, or even identical to, that of the rest of the PCB. Thus, the two coaxial drums do not generate thermomechanical stress when the temperature of the PCB varies during its use.

[0010] According to advantageous but not mandatory aspects of the invention, such a printed circuit board may incorporate one or more of the following features taken individually or in any technically permissible combination: - The second barrel delimits a second internal volume, which is sealed by a second polymer resin, while the card presents a first metallized surface, which extends over a portion of the upper face and connects the upper end of the first barrel to the upper end of the second barrel, and that the first metallized surface is suitable for contact with an electronic component, so as to transmit part of the heat generated by the electronic component in operation together to the first barrel and the second barrel. - The lower end of the first shaft and the lower end of the second shaft are located in the same plane orthogonal to the main axis. - The lower end of the first shaft is flush with the lower face of the card. - The second barrel delimits a second internal volume, which is sealed by a second polymer resin, while the card has a second metallized surface, which extends over the lower face and connects the lower end of the first barrel to the lower end of the second barrel, and the second metallized surface is suitable for contact with a radiator component, so as to cool the first barrel and the second barrel. - The first polymer resin and / or the second polymer resin have a thermal conductivity greater than 2 W / mK. - The card includes an electronic component, for example a voltage amplifier, which is mounted on the top face of the card, the electronic component being in contact jointly with the top end of the first barrel and with the top end of the second barrel.

[0011] The invention also relates to an electronic device, comprising a card as described above.

[0012] According to another aspect, the invention relates to a method for manufacturing a printed circuit board as described above, the method including the following steps: - a step involving the supply of the printed circuit board, - Next, a first drilling stage, during which the card is drilled along its vertical axis, so as to form a first hole opening onto the upper face, - then, a first metallization stage, during which the first hole is metallized, so as to form the first shaft, the first shaft delimiting a first internal volume that is substantially cylindrical and centered on the main axis, with one upper end of the first shaft flush with the upper face, - then, a first filling stage, during which the first internal volume is filled using a first polymer resin, - then, a second drilling stage, during which the first internal volume filled by the first polymer resin is drilled, so as to form a second hole, the second hole having a diameter smaller than the diameter of the first internal volume and opening onto the upper face, - then, a second metallization stage, during which the second hole is metallized, so as to form the second barrel coaxial with the first barrel, with one upper end of the second barrel flush with the upper face.

[0013] This process induces the same advantages as those mentioned above with regard to the electronic card of the invention.

[0014] Advantageously, the process comprises the following steps: - a second filling stage, during which a second internal volume delimited by the second barrel is filled using a second polymer resin, the second filling stage being subsequent to the second metallization stage, - then, a third metallization stage, which is subsequent to the second filling stage, during which a portion of the upper face is metallized, so as to form a first metallized surface connecting the upper end of the first shaft to the upper end of the second shaft.

[0015] Advantageously, during the first metallization step, a lower end of the first barrel is flush with the lower face, while during the second metallization step, a lower end of the second barrel is flush with the lower face, and the process includes a fourth metallization step, which is subsequent to the second filling step, during which a portion of the lower face is metallized, so as to form a second metallized surface connecting the lower end of the first barrel to the lower end of the second barrel.

[0016] The invention will be better understood, and other advantages thereof will become more apparent in the light of the following description of several embodiments of an electronic board, an electronic device and a manufacturing process, in accordance with its principle, given solely by way of example and with reference to the accompanying drawings, in which:

[0017] - [Fig. 1] [Fig. 1] represents, respectively, on two inserts a) and b), a view in perspective and a cross-section of an electronic device according to a first embodiment of the invention, the electronic device comprising a printed circuit board also according to the first embodiment of the invention;

[0018] - [Fig.2] [Fig.2] represents, on four inserts a) to d), manufacturing steps of the printed circuit board of [Fig.1];

[0019] - [Fig.3] [Fig.3] represents, on four inserts a) to d), other manufacturing steps of the printed circuit board of [Fig. 1], and

[0020] - [Fig.4] [Fig.4] represents a top view of an electronic board conforming to a second embodiment of the invention.

[0021] A first embodiment of the invention is described with reference to Figures 1 to 3. An electronic device 10 is shown in [Fig. 1]#a). The electronic device 10 is schematically represented by a parallelepiped in dashed lines. The electronic device 10 comprises a card 12. The card 12 is a printed circuit board, or PCB. The card 12 has two opposite faces, the two opposite faces including a top face 14A and a bottom face 14B and being orthogonal to an axis of height Z12. Generally speaking, the notions of "top", "bottom", "right", "left", are data relating to the orientation of the elements as illustrated in the drawings, knowing that it may be otherwise in reality.

[0022] In a known manner, the card 12 is formed by pressing several layers of insulating substrate one on top of the other, with metallic layers, in particular copper, located on faces of the substrate layers. The metallic layers are etched to form printed circuits. The printed circuits on the surface of the substrate layers are not shown. It is known to provide electrical connections between the printed circuits through the substrate layers by creating metallized holes called "vias." Thus, a via is generally in the form of a metallic tube that passes through one or more substrate layers along the vertical axis.

[0023] In the illustrated example, the card 12 is formed by laminating three layers 12A, 12B and 12C of substrates, this number not being limiting, knowing that the invention can be implemented for a single-layer printed circuit board (from a substrate point of view) as well as for a multi-layer board.

[0024] The card 12 includes an electronic component 16, for example here a voltage amplifier, which is mounted on the upper face 14A of the card 12. The electronic component 16 is thus a surface-mounted component, also called SMD, so as to be connected to the printed circuit located on the upper face 14A.

[0025] When the electronic device 10 is in normal operation, the electronic component 16 generates heat, which must be dissipated. To this end, a via 20 is provided through the board 12. The via 20 is visible in cross-section in [Fig. 3]#d). The via 20 extends along a principal axis A20 which is parallel to the height axis Z12.

[0026] The via comprises a first shaft 21, extending along the principal axis A20, and made of metal. The first shaft 21 is formed by drilling through the card 12, preferably using a drill bit, the resulting hole then being metallized to form the first shaft 21. Metallization deposits a layer of metal, preferably copper, with a thickness generally between 18 µm and 30 µm. Metallization is carried out, for example, by electrochemical deposition. The first shaft 21 thus has a substantially cylindrical shape with a circular cross-section. The first shaft 21 has an upper end 24A, which is flush with the upper face 14A of the card 12, and a lower end 24B, which is flush with the face 14B, located opposite the upper end 24A along the principal axis A20. The lower end 24B is thus located on the side of the lower face 14B.The first barrel 21 delimits a first internal volume V21, which connects the upper face 14A to the lower face 14B through the card 12. It is understood that the first internal volume V21 corresponds approximately to the first hole 30, minus the first barrel 21.

[0027] The first barrel 21 is configured to dissipate some of the heat generated by the electronic component 16 in operation, the electronic component 16 being mounted against the upper end 24A of the first barrel 21.

[0028] The via 20 comprises a second barrel 22, which differs from the first barrel 21, and is made of metal and is arranged coaxially with the first barrel 21 in the first internal volume V21. The second barrel 22 is secured to the first barrel 21 by means of a first polymer resin 32, which fills a portion of the first internal volume 21 located between the second barrel 22 and the first barrel 21. The second barrel 22 has a substantially cylindrical shape with a circular cross-section. The second barrel 22 has an upper end 26A, which is flush with the upper face 24A of the card 12, and a lower end 26B opposite the upper end 26A. The second barrel 22 is configured to dissipate some of the heat generated by the electronic component 16 during operation, the electronic component 16 being mounted against the upper end 26A of the second barrel 22.

[0029] Thus it is understood that the first barrel 21 and the second barrel 22 jointly contribute to evacuating part of the heat generated by the electronic component 16 in operation.

[0030] In the illustrated example, the second barrel 22 is also filled with polymer resin 32 in order to provide support for the copper covering of the entire surface used for heat transfer or for assembly considerations of component 16. In an alternative not illustrated, the second barrel 22 is not filled with polymer resin.

[0031] A manufacturing process for via 20 is now described, with reference to Figures 2 and 3.

[0032] The process includes a step 101 of supplying the printed circuit board 12, as illustrated in [Fig.2]#a).

[0033] Next, the process includes a first drilling step 102, during which the card 12 is drilled along the height axis Z12, so as to form a first hole 30 opening onto the upper face 14A as illustrated in [Fig. 2]#b). In practice, the first hole 30 is drilled using a drill bit. The first hole 30 typically has a diameter between 500 µm and 1100 µm. The first hole 30 has a generally cylindrical shape with a circular cross-section centered on the main axis A20.

[0034] Next, the process comprises a first metallization step 103, during which the first hole 30 is metallized to form the first barrel 21, as illustrated in [Fig. 2]#c). The first barrel 21 defines the first internal volume V21, which is substantially cylindrical and centered on the main axis A30. The first metallization step 103 allows for the application of a metal thickness typically ranging from 20 to 30 µm. It is understood that the first internal volume V21 then corresponds approximately at hole 30, less the thickness of metal of the barrel 21. The upper end 24A of the first barrel 21 is flush with the upper face 14A of the card 12. Preferably, the lower end 24B of the first barrel 21 is flush with the lower face 14B of the card 12.

[0035] Next, the process includes a first filling step 104, during which the first internal volume V21 is filled with a first polymer resin 32. By way of non-limiting examples, the first polymer resin 32 is, for example, an epoxy resin. After hardening, the polymer resin 32 forms a solid plug, which seals the first internal volume V21, as illustrated in [Fig. 2]#d).

[0036] Next, the process includes a second drilling step 105, during which the first internal volume V21, previously filled with the first polymer resin 32, is drilled to form a second hole 34. This second hole 34 has a diameter smaller than one diameter of the first internal volume V21 and opens onto the upper face 14A, as illustrated in [Fig. 3]#a). Preferably, the second hole 34 is centered on the main axis A20. Preferably, the drilling of the first internal volume V21 is carried out using a drill bit. According to an alternative not shown, the drilling of the first internal volume V21 is carried out using a laser, this method being conventionally used to create small-diameter vias called "micro-vias".

[0037] Next, the process includes a second metallization step 106, during which the second hole 34 is metallized to form the second barrel 22, as illustrated in [Fig. 3]#b). The second barrel 22 defines a second internal volume V22. It is understood that the second internal volume V22 corresponds substantially to the second hole 34, minus the thickness of the second barrel 22.

[0038] Preferably, the second barrel 22 is coaxial with the first barrel 21, the upper end 26A of the second barrel 22 being flush with the upper face 14A of the card 12. In other words, the upper ends 26A and 24A of the second barrel 22 and the first barrel 21 are flush with the upper face 14A of the card 12, so that when the electronic component 16 is assembled on the card 12, the electronic component 16 is in contact with the first and second barrels 21 and 22, thus facilitating heat transfer. This results in the via 20.

[0039] With reference to [Fig.3]#c), the process advantageously includes a second filling step 107, which is subsequent to the second metallization step 106 and during which the second internal volume V22 is filled, by means of a second polymer resin 36. After hardening, the second polymer resin 36 forms a solid plug, which seals the second internal volume V22.

[0040] Next, with reference to [Fig. 3]#d), the process advantageously comprises a third metallization step 108, during which a portion of the upper face 14A of card 12, so as to connect the upper end 24A of the first barrel 21 to the upper end 26A of the second barrel 22.

[0041] As a result, the card 12 advantageously has a first metallized surface S41, which extends over a portion of the upper face 14A and connects the upper end 24A of the first barrel 21 to the upper end 24B of the second barrel 22. Preferably, the first metallized surface S41 covers at least the first internal volume V21 on the upper face 14A. The first metallized surface S41 is suitable for contact with the electronic component 16, so as to transmit a portion of the heat generated by the electronic component 16 during operation to the first barrel 21 and the second barrel 22.

[0042] Similarly, the process advantageously includes a fourth metallization step 109, which is subsequent to the second filling step 107 and during which a portion of the lower face 14B is metallized, so as to form a second metallized surface S42 connecting the lower end 24B of the first shaft 21 to the lower end 26B of the second shaft 22. Preferably, the third metallization steps 108 and the fourth metallization steps 109 are simultaneous.

[0043] As a result, the card 12 advantageously presents the second metallized surface S42, which extends over a portion of the lower face 14B and connects the lower end 24B of the first barrel 21 to the lower end 26B of the second barrel 22. Preferably, the second metallized surface S42 covers at least the first internal volume V21 on the lower face 14B. The second metallized surface S42 is suitable for contact with a heat sink component 44, so as to cool the first barrel 21 and the second barrel 22. The heat sink component 44 is shown in [Fig. 1]#b). It is understood that for the installation of the second metallized surface S42, it is necessary that the lower end 24B of the first shaft 21 and that the lower end 26B of the second shaft 22 be located in the same plane orthogonal to the main axis A20, and preferably be flush with the lower face 14B of the card 12.

[0044] Preferably, the first polymer resin 32 and / or the second polymer resin 36 are thermally conductive resins. For example, thermally conductive fillers are added to the resins so as to improve the thermal conductivity of the material. By way of non-limiting agreement, the conductive fillers include metal powders, preferably copper, and / or carbon fibers.

[0045] By way of illustration, a conventional epoxy resin has a thermal conductivity of approximately 0.2 W / mK —#Watt per meter-Kelvin#-. A thermally conductive epoxy resin has a thermal conductivity ranging from 2 to 5 W / mK. For comparison, copper has a thermal conductivity of approximately 380 W / mK. In the context of this application, a polymer resin is considered to be thermally conductive when its thermal conductivity is greater than 2 W / mK.

[0046] Within the scope of the invention, it is not necessary for the first or second polymer resins 32 / 34 to be electrically insulating. It is thus possible to modify the first or second polymer resins 32 / 34 as required, provided that the mechanical strengths remain acceptable for the intended application, and provided that a coefficient of thermal expansion of the first or second polymer resins 32 / 34, once cured, remains substantially equal to a coefficient of thermal expansion of the board 12 along the height axis Z12. By substantially equal, we mean of the same order of magnitude.

[0047] Preferably, the second polymer resin 36 used during the second filling step 107 is similar, or even identical, to the first polymer resin 32 used during the first filling step 104.

[0048] A printed circuit board 212, according to a second embodiment of the invention, is shown in [Fig. 4]. In the second embodiment, the elements analogous to those of the first embodiment bear the same reference numerals and function in the same way. The following primarily describes the differences between the first and second embodiments.

[0049] Whereas in the first embodiment, the card 12 comprises a single via 20, which includes two coaxial shafts, namely the first shaft 21 and the second shaft 22, in the second embodiment, the card 212 comprises several vias 20, each comprising the first shaft 21 and the second shaft 22. In the illustrated example, the vias 20 are advantageously arranged in a staggered pattern, which maximizes the surface area of ​​the copper while maintaining a minimum spacing between each via to meet manufacturing constraints. It is possible to reduce the spacing so that the pads of the vias 20 are tangent to each other.

[0050] By way of comparison, when vias according to the prior art are provided on a printed circuit board to dissipate heat from surface-mounted electronic components, typically 300 µm vias are arranged in a staggered pattern, with a spacing of 650 µm between the vias. This represents a "hole density" of 2.73 holes / mm². Considering that each via comprises a single shaft with a thickness of approximately 20 µm, this results in a copper density of 4.8%.

[0051] According to an example of the invention, the vias are arranged in a staggered pattern with a spacing of 900 µm, resulting in a "hole surface density" of 1.28 holes / mm². For each via, the first shaft 21 has a diameter of 600 µm, and the second shaft has a diameter of 300 µm, with both shafts 21 / 22 having a thickness of 20 µm. Under these conditions, a surface density of Copper content is 6.9%, representing a 44% increase compared to prior art. The thermal conductivity gain is also 44%. Furthermore, the copper thickness of the shafts, typically 20 to 30 sq m, is sufficiently reduced that the shafts do not have a significant impact on the thermal expansion coefficient of the 20 / 220 via along the Z12 height axis. It is, of course, possible to manufacture thicker shafts, as long as the Z-axis thermal expansion coefficients of the vias thus manufactured remain approximately equal to the Z-axis thermal expansion coefficient of the 12 chart. However, the metallization step will take longer, increasing the manufacturing cost.

[0052] In both illustrated embodiments, each via 20 / 220 comprises two coaxial shafts.

[0053] In an alternative not shown, each via comprises three or more coaxial metal drums. It is understood that using three coaxial drums represents an additional cost in terms of manufacturing time and / or cost; however, such a three-coaxial-drum arrangement can prove advantageous for locally cooling a small electronic component.

[0054] The embodiments and variants mentioned above can be combined with each other to generate new embodiments of the invention.

Claims

1.

2. Demands Printed circuit board (12; 212), in which: • the card (12; 212) has two opposite faces, the two opposite faces including a top face (14A) and a bottom face (14B) and being orthogonal to a height axis (Z12), • the map (12; 212) includes a via (20), which is provided through the map (12; 212) and which extends along a main axis (A20) parallel to the height axis (Z12), • the via (20) includes a first shaft (21), which is made of metal, which extends along the main axis (A20) and which has an upper end (24A), which is flush with the upper face (14A), and a lower end (24B), which is located opposite the upper end (24A) along the main axis (A20), • the first barrel (21) is configured to dissipate heat from an electronic component (16), for example a voltage amplifier, when the electronic component (16) is fixed to the upper face (14A) resting against the upper end (24A) of the first barrel (21) and is in operation, • the via (20) includes a second barrel (22), which is different from the first barrel (21), which is made of metal and is arranged in a first internal volume (V21) of the first barrel (21) coaxially with the first barrel (21), the second barrel (22) having an upper end (26A), which is flush with the upper face (14A) of the card (12; 212), and a lower end (26B) opposite the upper end, • the second barrel (22) is secured to the first barrel (21) by means of a first polymer resin (32), • the second barrel (22) is configured to dissipate the heat generated by the electronic component (16) in operation. Card (12; 212) according to claim 1, wherein: • the second barrel (22) delimits a second internal volume (V22), which is sealed by a second polymer resin (36), • the card (12; 212) has a first metallized surface (S41), which extends over a portion of the upper face (14A) and which connects the upper end (24A) of the first barrel (21) to the upper end (26A) of the second barrel (22), • the first metallized surface (S41) is suitable for contact with an electronic component (16), so as to transmit part of the heat generated by the electronic component (16) in operation together with the first barrel (21) and the second barrel (22).

3. Card (12; 212) according to any one of claims 1 or 2, wherein: • the lower end (24B) of the first shaft (21) and the lower end (26B) of the second shaft (22) are located in the same plane orthogonal to the main axis (A20).

4. Card (12; 212) according to claim 3, wherein: • the lower end (24B) of the first shaft (21) is flush with the lower face (14B) of the card (12; 212).

5. Card (12; 212) according to claim 4, wherein: • the second barrel (22) delimits a second internal volume (V22), which is sealed by a second polymer resin (36), • the card (12; 212) has a second metallized surface (S42), which extends over the lower face (14B) and which connects the lower end (24B) of the first barrel (21) to the lower end (26B) of the second barrel (22), • the second metallized surface (S42) is suitable for contact with a radiator component, so as to cool the first barrel (21) and the second barrel (22).

6. Card (12; 212) according to claim 5, wherein: • the first polymer resin (32) and / or the second polymer resin (36) have a thermal conductivity greater than 2 W / mK.

7. Card (12; 212) according to any one of claims 1 to 6, wherein: • the card (12; 212) comprises an electronic component (16), for example a voltage amplifier, which is mounted on the upper face (14A) of the card (12; 212), the electronic component (16) being in contact jointly with the upper end (24A) of the first barrel (21) and with the upper end (26A) of the second barrel (22).

8. Electronic device (10), comprising a card (12; 212) according to the preceding claim.

9. A method for manufacturing a printed circuit board (12; 212), the method including the following steps:

10. • a step of supplying (101) the printed circuit board (12; 212), • then, a first drilling step (102), during which the card (12; 212) is drilled along the height axis (Z12), so as to form a first hole (30) opening onto the upper face (14A), • then, a first metallization step (103), during which the first hole (30) is metallized, so as to form the first shaft (21), the first shaft (21) delimiting a first internal volume (V21) substantially cylindrical centered on the main axis (A20), an upper end of the first shaft (21) flush with the upper face (14A), • then, a first filling step (104), during which the first internal volume (V21) is filled with a first polymer resin (32), • then, a second drilling step (105), during which the first internal volume (V21) filled with the first polymer resin (32) is drilled, so as to form a second hole (34), the second hole having a diameter less than a diameter of the first internal volume (V21) and opening onto the upper face (14A), • then, a second metallization step (106), during which the second hole (34) is metallized, so as to form the second shaft (22) coaxial with the first shaft (21), an upper end (26A) of the second shaft (22) flush with the upper face (14A). A method according to claim 9, comprising the following steps: • a second filling step (107), during which a second internal volume (V22) delimited by the second barrel (22) is filled, using a second polymer resin (36), the second filling step (107) being subsequent to the second metallization step (106), • then, a third metallization step (108), which is subsequent to the second filling step (107), during which a portion of the upper face (14A) is metallized, so as to form a first metallized surface (S41) connecting the upper end (24A) of the first shaft (21) to the upper end (26A) of the second shaft (22).

11. The method according to claim 10, wherein: during the first metallization step (103), a lower end (24B) of the first barrel (21) is flush with the lower face (14B), during the second metallization stage (106), a lower end (26B) of the second barrel (22) is flush with the lower face (14B), the process includes a fourth metallization step (109), which is subsequent to the second filling step (107), during which a portion of the lower face (14B) is metallized, so as to form a second metallized surface (S42) connecting the lower end (24B) of the first shaft (21) to the lower end (26B) of the second shaft (22).

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